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1
Gotoh, Hiroaki, Chang Liu, Abu Bin Imran, Mitsuo Hara, Takahiro Seki, Koichi Mayumi, Kohzo Ito, and Yukikazu Takeoka. "Optically transparent, high-toughness elastomer using a polyrotaxane cross-linker as a molecular pulley." Science Advances 4, no. 10 (October 2018): eaat7629. http://dx.doi.org/10.1126/sciadv.aat7629.
Повний текст джерелаАнотація:
An elastomer is a three-dimensional network with a cross-linked polymer chain that undergoes large deformation with a small external force and returns to its original state when the external force is removed. Because of this hyperelasticity, elastomers are regarded as one of the best candidates for the matrix material of soft robots. However, the comprehensive performance required of matrix materials is a special challenge because improvement of some matrix properties often causes the deterioration of others. For example, an improvement in toughness can be realized by adding a large amount of filler to an elastomer, but to the impairment of optical transparency. Therefore, to produce an elastomer exhibiting optimum properties suitable for the desired purpose, very elaborate, complicated materials are often devised. Here, we have succeeded in creating an optically transparent, easily fabricated elastomer with good extensibility and high toughness by using a polyrotaxane (PR) composed of cyclic molecules and a linear polymer as a cross-linking agent. In general, elastomers having conventional cross-linked structures are susceptible to breakage as a result of loss of extensibility at high cross-linking density. We found that the toughness of the transparent elastomer prepared using the PR cross-linking agent is enhanced along with its Young’s modulus as cross-linking density is increased.
2
Furukawa, M., and K. Wakiyama. "Deterioration of novel polyesterurethane elastomers in outdoor exposure." Polymer Degradation and Stability 65, no. 1 (July 1999): 15–24. http://dx.doi.org/10.1016/s0141-3910(98)00209-2.
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3
Choi, I. S., C. M. Roland, and L. C. Bissonnette. "An Elastomeric Ejection System." Rubber Chemistry and Technology 67, no. 5 (November 1, 1994): 892–903. http://dx.doi.org/10.5254/1.3538720.
Повний текст джерелаАнотація:
Abstract The ability of elastomers to store large quantities of energy, which can subsequently be recovered very quickly, makes them attractive materials for propulsion devices. Recently the U.S. Navy has developed a torpedo ejection system based on an elastomeric mechanical capacitor. The criteria governing selection of a material for this application include high elastic energy, sufficient fatigue life, minimal creep, and resistance to deterioration by seawater. This paper describes various approaches to obtaining these material properties.
4
Toczek, Klaudia, Magdalena Lipińska, and Joanna Pietrasik. "Smart TPE Materials Based on Recycled Rubber Shred." Materials 14, no. 21 (October 20, 2021): 6237. http://dx.doi.org/10.3390/ma14216237.
Повний текст джерелаАнотація:
Thermo-responsive shape memory materials were developed based on recycled ethylene-propylene-diene (EPDM) rubber shred and thermoplastic elastomers (TPE). Ethylene-1-octene TPEs (Engage 8180, 8411, 8452) with varying degrees of crystallinity and Mooney viscosity were used to prepare the composite materials. To avoid the deterioration of static mechanical properties after mixing recycled EPDM rubber shred (RS) with thermoplastic elastomers, they were partially cured using dicumyl peroxide. The peroxide curing was the most effective for a rubber shred/Engage 8180 blend, where the highest cure rate index (CRI), 1.88 dNm⋅min−1, was observed. The curing caused an approximately 4-fold increase of tensile strength (TS) values for EPDM rubber shred/thermoplastic elastomer blend to the level acceptable for the rubber industry compared with an uncured blend. The incorporation of EPDM rubber shred changed thermoplastic elastomers’ viscoelastic behavior, increasing the values of storage (G′) and loss (G″) modulus. The lowest viscosity of molten Engage 8411 during mixing led to higher compatibility of rubber shred RS/8411 blend, as confirmed by analysis of Cole-Cole plots and the blend morphology. All rubber shred RS/TPE blends showed the shape memory behavior. For the RS/Engage 8452 blend, the highest shape fixity (F) value (94%) was observed, while the shape recovery (RR) was 87%. Studies confirmed that the intelligent materials with shape memory effect could be obtained via selectively chosen thermoplastic elastomers; ethylene-1-octene as a binder for recycled EPDM. Prepared recycled TPE/rubber shred blends can be successfully reused due to their viscoelastic and mechanical properties. Therefore, such a concept can be potentially interesting for the rubber industry.
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Gunatillake, Pathiraja A., Darren J. Martin, Gordon F. Meijs, Simon J. McCarthy, and Raju Adhikari. "Designing Biostable Polyurethane Elastomers for Biomedical Implants." Australian Journal of Chemistry 56, no. 6 (2003): 545. http://dx.doi.org/10.1071/ch02168.
Повний текст джерелаАнотація:
The chemical structure, synthesis, morphology, and properties of polyurethane elastomers are briefly discussed. The current understanding of the effect of chemical structure and the associated morphology on the stability of polyurethanes in the biological environments is reviewed. The degradation of conventional polyurethanes appears as surface or deep cracking, stiffening, and deterioration of mechanical properties, such as flex-fatigue resistance. Polyester and poly(tetramethylene oxide) based polyurethanes degrade by hydrolytic and oxidative degradation of ester and ether functional groups, respectively. The recent approaches to develop polyurethanes with improved long-term biostability are based on developing novel polyether, hydrocarbon, polycarbonate, and siloxane macrodiols to replace degradation-prone polyester and polyether macrodiols in polyurethane formulations. The new approaches are discussed with respect to synthesis, properties and biostability based on reported in vivo studies. Among the newly developed materials, siloxane-based polyurethanes have exhibited excellent biostability and are expected to find many applications in biomedical implants.
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Senichev, V. Yu, and E. V. Pogorel’tsev. "Abrasive resistance of polyetherurethane ureas." Journal of Physics: Conference Series 2094, no. 4 (November 1, 2021): 042077. http://dx.doi.org/10.1088/1742-6596/2094/4/042077.
Повний текст джерелаАнотація:
Abstract The relationship between the structure of the polymer chains and the abrasion resistance of segmented polyurethane ureas based on polyoxytetramethylene oligoether was studied. Experimental data were obtained for systems with the hard segments content above 39%. It was found that the function of the volumetric wear of polyurethane-urea samples on the content of hard segments had an extremum; at high contents of these segments (more than 35%), a further increase in this content lead to a deterioration in the abrasion resistance. The reasons for this effect can be associated with a sharp deterioration in the strength and strain properties of the studied elastomers when additional amounts of diisocyanate are introduced into the system, which can lead to the formation of excessive interchain bonds.
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Diekmann, Astrid, Marvin Christopher Vincenzo Omelan, Ulrich Giese, and Viktor Rose. "CARBON NANOHORN–BASED NBR HYBRID NANOCOMPOSITES." Rubber Chemistry and Technology 93, no. 4 (October 1, 2020): 615–32. http://dx.doi.org/10.5254/rct.20.79958.
Повний текст джерелаАнотація:
ABSTRACT Carbon nanohorn (CNH)–filled elastomer hybrid nanocomposites were prepared based on NBR. Three different CNH types were analyzed, each featuring various characteristics such as aggregate structure, specific surface area, surface energy distribution, and electrical conductivity and resulting in different potentials regarding the properties of the developed elastomers. For the CNH types, a high tendency of agglomeration was observed in the pristine state, indicating the need for an effective strategy to break up the agglomerates during the mixing or the compounding procedure to realize their incorporation and sufficient dispersion in a polymer matrix. In addition to the melt mixing technology by means of an internal lab mixer, a discontinuous static and a continuous dynamic latex compounding process were used. Carbon nanotubes and a highly conductive carbon black (Printex) were used as hybrid fillers in the compounds mixed by melt mixing, whereas two different types of carbon black (Printex and Derussol) were also incorporated in the latex experiments. Hybrid nanocomposites with low content of CNHs (≤1 wt%) show an improvement in dynamic-mechanic and physical properties due to distinctive polymer–filler interactions. Dealing with higher amounts of CNHs leads to filler reagglomeration, resulting in deterioration of the elastomer properties. For the electric conductivity assessment, addition of CNH indicates no synergistic effects and no significant increase of the hybrid compounds, which is demonstrated in dielectric measurements, although pristine CNHs are conductive themselves. Elastomer compounds processed via the latex method show enhanced material performance by using the continuous dynamic latex compounding, which is mainly attributed to the dispersion of the hybrid filler.
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Hu, Hang, Dongsheng Li, and Weijun Zhu. "Piezoelectric composites from sandwiched polydimethylsiloxane sponges." Journal of Applied Physics 132, no. 18 (November 14, 2022): 184901. http://dx.doi.org/10.1063/5.0111435.
Повний текст джерелаАнотація:
A novel elastomer-based composite material with enhanced piezoelectric performances is proposed in this paper, which is composed of the top and bottom polytetrafluoroethylene (PTFE) solid films with the middle PTFE nanoparticle–polydimethylsiloxane (PDMS) sponge layer. To enhance the charge retention capability of elastomers, PTFE nanoparticles are introduced to form PTFE–PDMS interfaces, which can trap charges with longevity. Besides, PTFE solid films take on the role of the charge blocking layers to further improve the piezoelectric performances. As a result, the PTFE–PDMS sandwich structure shows the advantages of remarkable sensitivity (1053 pC/N), high stability, and flexibility. After a 6 h of annealing treatment at the temperature of 100 °C, no significant deterioration of the piezoelectric properties can be observed, which reveals the great thermal stability of the sandwich structure. In addition, the sandwich structure can be immersed in water for 24 h without any loss of piezoelectric activity. Finally, the experiment of lighting one LED by hand pressing successfully demonstrates that the sandwich structure has good applicability in the field of energy harvesting. Considering the excellent electrical and mechanical features, the PTFE–PDMS sandwich structure has promising applications in sensing, energy harvesting, and actuation.
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Huang, Xiaoyu, Jinghui Zhao, Yichun Wang, Yuchao Ke, and Zixi Wang. "Study on a New Static Sealing Method and Sealing Performance Evaluation Model for PEMFC." World Electric Vehicle Journal 12, no. 4 (November 11, 2021): 237. http://dx.doi.org/10.3390/wevj12040237.
Повний текст джерелаАнотація:
The long-term stability and durability of seals are critical for various instruments and types of equipment. For static sealing, an important sealing state, there are currently two representative sealing methods, namely, pre-compressing static sealing and adhesive static sealing. In this paper, the characteristics and shortcomings of these sealing methods are summarized. At present, some static sealing requirements are urgent and difficult. For example, the deterioration of the sealing performance is an important factor which limits the service life of proton exchange membrane fuel cells and redox flow batteries. Therefore, a new method of static sealing whose sealing materials are rubber elastomers is proposed, named alterable static sealing. Then, its sealing processes are proposed. Furthermore, the actual contact area ratio r is used as the standard for sealability. Based on the mathematical model of pre-compressing static sealing, the influence of interface bonding was considered, and the mathematical model of alterable static sealing was established. Moreover, the compensatory effect of alterable static sealing on the static sealing capacity of rubber elastomers was proved.
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Lattimer, Robert P., Robert A. Kinsey, Robert W. Layer, and C. K. Rhee. "The Mechanism of Phenolic Resin Vulcanization of Unsaturated Elastomers." Rubber Chemistry and Technology 62, no. 1 (March 1, 1989): 107–23. http://dx.doi.org/10.5254/1.3536228.
Повний текст джерелаАнотація:
Abstract It is well known that during the sulfur curing of unsaturated rubbers, two competing reactions occur: (a) crosslinking or vulcanization, and (b) reversion or devulcanization. In the case of butyl rubber, these two competing reactions have been summarized in earlier reports. Tire curing bag (bladder) compounds are usually made of butyl rubber (IIR), a copolymer of isobutene and isoprene, with typically 1–5% of the diene monomer. Curing bags were originally manufactured using sulfur cures. The high temperatures (140–180°C) employed in tire curing caused reversion, however, and these bladders had very short service lives. The deterioration of the IIR bladders was evidenced by a gradual softening of the surface. A major technical advancement for increasing the service life of curing bladders was the development of phenol/formaldehyde (resole) resins for vulcanizing IIR. These resins can give IIR cures with very thermally stable crosslinks. The vulcanizates are essentially immune to reversion, even at the high use temperatures of tire curing operations. The basic curing resins used are generally 2,6-dihydroxymethyl-4-alkylphenols 1 or their condensation polymers 2 (Scheme 1). These materials are produced via the base-catalyzed reaction of the p-substituted phenol with formaldehyde. R is typically methyl, t-butyl, or t-octyl in commercial resins. The use of a blocking substituent in the para position maximizes the formation of o-hydroxymethyl groups. R′ is either methylene (—CH2—) or dibenzylether (—CH2—O—CH2—), depending on the conditions of the resin synthesis or the cure.
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Aziz, Siti Aishah Abdul, Saiful Amri Mazlan, U. Ubaidillah, Norzilawati Mohamad, Seung-Bok Choi, Mohamad Amirul Che Aziz, Mohd Aidy Faizal Johari, and Koji Homma. "Thermal Aging Rheological Behavior of Magnetorheological Elastomers Based on Silicone Rubber." International Journal of Molecular Sciences 21, no. 23 (November 27, 2020): 9007. http://dx.doi.org/10.3390/ijms21239007.
Повний текст джерелаАнотація:
Engineering rubber composites have been widely used as main components in many fields including vehicle engineering and biomedical applications. However, when a rubber composite surface area is exposed to heat or sunlight and over a long-term accelerated exposure and lifecycle of test, the rubber becomes hard, thus influencing the mechanical and rheological behavior of the materials. Therefore, in this study, the deterioration of rheological characteristics particularly the phase shift angle (δ) of silicone rubber (SR) based magnetorheological elastomer (MRE) is investigated under the effect of thermal aging. SR-MRE with 60 wt% of CIPs is fabricated and subjected to a continuous temperature of 100 °C for 72 h. The characterization of SR-MRE before and after thermal aging related to hardness, micrograph, and rheological properties are characterized using low vacuum scanning electron microscopy (LV-SEM) and a rheometer, respectively. The results demonstrated that the morphological analysis has a rough surface and more voids occurred after the thermal aging. The hardness and the weight of the SR-MRE before and after thermal aging were slightly different. Nonetheless, the thermo-rheological results showed that the stress–strain behavior have changed the phase-shift angle (δ) of SR-MRE particularly at a high strain. Moreover, the complex mechanism of SR-MRE before and after thermal aging can be observed through the changes of the ‘in-rubber structure’ under rheological properties. Finally, the relationship between the phase-shift angle (δ) and the in-rubber structure due to thermal aging are discussed thoroughly which led to a better understanding of the thermo-rheological behavior of SR-MRE.
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Marykutty, C. V., G. Mathew, and Sabu Thomas. "Mechanical and Swelling Behavior of Double Networked Natural Rubber Cured Using a New Binary Accelerator System." Rubber Chemistry and Technology 80, no. 5 (November 1, 2007): 809–19. http://dx.doi.org/10.5254/1.3539417.
Повний текст джерелаАнотація:
Abstract The concept of double networks, which impart chain orientation to elastomers, is a rather new idea. Double networks were induced in natural rubber vulcanizates cured with different accelerator systems. Double networked natural rubber with different extensions cured with N-cyclohexyl benzothiazyl sulphenamide (CBS) and 1-phenyl 5-ortho -tolyl 2,4 dithiobiuret was studied and the effect of extension on the mechanical properties and swelling was analyzed. The extent of chain orientation was analyzed through anisotropic swelling studies. The modulus, tensile strength and tear strength showed an increase with increased residual extension ratio. The effect was more predominant in the longitudinal direction than in the transverse direction. The ultimate tensile elongation showed a slight deterioration. It was revealed that the formation of double networks with higher residual extension ratios restricted the entry of the solvent. Based on the studies it was concluded that residual extension has a profound effect in determining the final properties of vulcanizates.
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Li, Gui-Yang, and J. L. Koenig. "A Review of Rubber Oxidation." Rubber Chemistry and Technology 78, no. 2 (May 1, 2005): 355–90. http://dx.doi.org/10.5254/1.3547888.
Повний текст джерелаАнотація:
Abstract The aging of rubber caused by oxidative degradation leads to the deterioration in the physical and mechanical properties of vulcanized rubbers. In an effort to improve the oxidative stability of rubbers and elastomers, considerable amount of work has been carried out over the past 50 years (especially in the most recent 5 years) in order to understand degradation modes and effects in rubber due to the action of oxygen and ozone in the air. Different mechanisms have been proposed to interpret the experimental data relative to the oxidation of rubber. The diffusion limited theory has been widely used in the literature and verified by many experiments. Various instrumental techniques have been utilized to characterize the oxidation and degradation and their mechanisms in rubber compounds. Recently, FTIR imaging has demonstrated a unique combination of spectral and spatial resolution which allows not only the identification of the oxidation products but also their spatial distribution from the oxygen penetrating surfaces. This critical review will cover the major developments in our understanding of the oxidation of rubbers.
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Li, Gui-Yang, and J. L. Koenig. "A Review of Rubber Oxidation." Rubber Chemistry and Technology 78, no. 3 (July 1, 2005): 355–90. http://dx.doi.org/10.5254/1.3547889.
Повний текст джерелаАнотація:
Abstract The aging of rubber caused by oxidative degradation leads to the deterioration in the physical and mechanical properties of vulcanized rubbers. In an effort to improve the oxidative stability of rubbers and elastomers, considerable amount of work has been carried out over the past 50 years (especially in the most recent 5 years) in order to understand degradation modes and effects in rubber due to the action of oxygen and ozone in the air. Different mechanisms have been proposed to interpret the experimental data relative to the oxidation of rubber. The diffusion limited theory has been widely used in the literature and verified by many experiments. Various instrumental techniques have been utilized to characterize the oxidation and degradation and their mechanisms in rubber compounds. Recently, FTIR imaging has demonstrated a unique combination of spectral and spatial resolution which allows not only the identification of the oxidation products but also their spatial distribution from the oxygen penetrating surfaces. This critical review will cover the major developments in our understanding of the oxidation of rubbers.
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Aziz, Siti Aishah Binti Abdul, Saiful Amri Mazlan, Nur Azmah Nordin, Nor Azlin Nazira Abd Rahman, U. Ubaidillah, Seung-Bok Choi, and Norzilawati Mohamad. "Material Characterization of Magnetorheological Elastomers with Corroded Carbonyl Iron Particles: Morphological Images and Field-dependent Viscoelastic Properties." International Journal of Molecular Sciences 20, no. 13 (July 5, 2019): 3311. http://dx.doi.org/10.3390/ijms20133311.
Повний текст джерелаАнотація:
High temperatures and humidity could alter the field-dependent rheological properties of MR materials. These environmental phenomena may accelerate the deterioration processes that will affect the long-term rheological reliability of MR materials such as MR elastomer (MRE). This study therefore attempts to investigate the field-dependent rheological characteristics of MRE with corroded carbonyl iron particles (CIPs). The corroded CIPs were treated with hydrochloric acid (HCl) as a way of providing realistic environments in gauging the CIPs reaction towards the ambient conditions. The corroded CIPs along with silicone rubber as a matrix material were used in the fabrication of the MRE samples. To observe the effect of HCl treatment on the CIPs, the morphological observations of MREs with non-corroded and corroded CIPs were investigated via field emission scanning electron microscopy (FESEM), energy-dispersive x-ray spectroscopy (EDX) and x-ray diffractometer (XRD). In addition, the magnetic properties were examined through the vibrating sample magnetometer (VSM), while the field-dependent rheological characteristics such as the storage modulus of MRE with the corroded CIPs were also tested and compared with the non-corroded CIPs. The results showed that the corroded CIPs possessed hydrangea-like structures. In the meantime, it was identified that a sudden reduction of up to 114% of the field-dependent MR effect of MRE with the corroded CIPs was observed as a result of the weakened interfacial bonding between the CIPs and the silicon in the outer layers of the CIPs structure.
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Halász, István Zoltán, Dávid Kocsis, Dániel Ábel Simon, Andrea Kohári, and Tamás Bárány. "Development of Polypropylene-based Thermoplastic Elastomers with Crumb Rubber by Dynamic Vulcanization: A Potential Route for Rubber Recycling." Periodica Polytechnica Chemical Engineering 64, no. 2 (December 23, 2019): 248–54. http://dx.doi.org/10.3311/ppch.13962.
Повний текст джерелаАнотація:
In our current paper the preparation and properties of thermoplastic elastomer produced by dynamic vulcanization is presented and discussed. We dynamically vulcanized natural and styrene butadiene rubber (NR/SBR) phase by continuous extrusion. Dispersion and in-situ vulcanization of the rubber phase occurred simultaneously in a co-rotating twin screw extruder. We used a random polypropylene copolymer (rPP) as the thermoplastic matrix and untreated crumb rubber (CR) to partially substitute the neat fresh rubber in order to check whether this is a potential recycling route for waste rubber products. We studied the effect of various rubber formulations, various processing conditions (screw speed and configuration) and various CR particle size distributions by characterizing the mechanical performance of the thermoplastic dynamic vulcanizates (TDVs) with tensile and hardness tests and their morphology by evaluating SEM micrographs taken from the fracture surfaces of the tensile specimens. The results showed that increasing screw speed and more high-shear elements in the screw setup led to a finer dispersion of the rubber phase, resulting in improved mechanical properties. The ultimate tensile properties of the best TDVs reached 20.5 MPa in tensile strength and 550 % in strain at break. However, partial replacement of the fresh rubber with untreated CR caused a significant deterioration in mechanical properties, due to poor adhesion between the CR particles and the matrix and rubber. This suggests that some kind of pre-treatment (e.g. by microwave or other devulcanization techniques) is necessary to enhance the surface activity of the CR particles.
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Yue, Dongmei, Xinpeng Wei, Xunzhang Wang, Weimin Wang, and Liqun Zhang. "HYDROGENATED BUTADIENE-ACRYLONITRILE-BUTYLACRYLATE RUBBER AND ITS PROPERTIES." Rubber Chemistry and Technology 86, no. 2 (June 1, 2013): 165–74. http://dx.doi.org/10.5254/rct.13.88997.
Повний текст джерелаАнотація:
ABSTRACT Butadiene-acrylonitrile-butylacrylate rubber (BNBR), which is synthesized by copolymerization of butadiene, acrylonitrile, and butyl acrylate, retains excellent properties of oil resistance and heat resistance because of the introduction of -CN, -COOR in the polymer. However, the presence of a lot of carbon-carbon double bonds (-C=C-) could lead to deterioration of material properties such as thermal stability and ozone resistance. To improve the properties of unsaturated elastomers, further chemical modification of diene-based polymers is very critical. Hydrogenation is a useful chemical modification method that can improve the thermal stability of diene-based polymer. BNBR was hydrogenated by homogenous hydrogenation using the Wilkinson catalyst RhCl(PPh3)3 in xylene. The effects of catalyst concentrations, reaction times, and hydrogen pressures on the conversion and product selectivity were discussed. The degree of hydrogenation was measured by proton nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy. The thermal stability of hydrogenated and nonhydrogenated copolymers was evaluated by thermogravimetric analysis (TGA). The CCD camera was used to characterize the ozone resistance of hydrogenated copolymer (HBNBR). The results obtained by TGA and the CCD camera show that the maximum saturation level is a critical factor for improvement of thermal stability and the ozone resistance of HBNBR.
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Moubark, Safaa, Farag Khodary, and Ayman Othman. "Evaluation of Mechanical properties for polypropylene Modified Asphalt concrete Mixtures." International Journal of Scientific Research and Management 5, no. 12 (December 31, 2017): 7797–801. http://dx.doi.org/10.18535/ijsrm/v5i12.28.
Повний текст джерелаАнотація:
It is noticeable that the increase of road traffic during the last two decades in addition to the insufficient degree of maintenance caused an accelerated deterioration of road structure. These roads show early signs of distress such as rutting, cracking, low temperature cracking, ageing and stripping. Heavier loads and higher traffic volume demand higher performance of pavement. Excellent performance of pavement requires bitumen that is less susceptible to high temperature, rutting or low temperature cracking. Several additives are used to increase the performance of bitumen and the quality of the produced mixtures. Polymers are considered the most widely used additives in asphalt modification that give better performance. The performance of the Polymer-modified asphalt depends on the type and the level of modification the used polymer. The choice of modification level and t modification type depends on the physical properties of the polymer, and its compatibility with bitumen. The polymer can be loosely classified into two categories, Plastomers and Elastomers. The results indicated that, the addition of polypropylene generally improved the mechanical properties of the mixture regardless of the percentage of polymers that added and (PP) content of 5%. it can be noticed that the performance of PP-modified asphalt mixtures is better compared with unmodified asphalt concrete mixtures modifier because it has the highest Marshall Stiffness, indirect tensile strength and unconfined compressive strength
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Paul, Anawe A. L., and Folayan J. Adewale. "Novel Synthetic-Based Drilling Fluid through Enzymatic Interesterification of Canola Oil." International Journal of Chemical Engineering 2018 (August 1, 2018): 1–11. http://dx.doi.org/10.1155/2018/6418090.
Повний текст джерелаАнотація:
Over the years, the oil industries have avoided aromatic, naphthenic, and paraffinic oils as drilling mud base fluids principally because of their detrimental environmental issues on pelagic and benthic marine ecosystems as a result of their toxicity and nonbiodegradability coupled with the possible deterioration of the oil itself and the rubber parts of the drilling equipment because the aromatic hydrocarbons present in the oil have a tendency to dissolve/damage elastomers present in rubber. Hence, possible insights into how to chemically and/or physically produce synthetic base drilling fluids whose cuttings are nontoxic, readily biodegradable, environmentally friendly, and of nonpetroleum source become imperative. In this study, enzymatic interesterification of canola oil was done with ethanol by using enzyme lipase as catalyst under optimum conditions of temperature and pressure and the physicochemical properties of the produced ester were evaluated and compared with that of diesel and a synthetic hydrocarbon base fluid (SHBF). Results show that the specific gravity, kinematic viscosity, dynamic viscosity, and surface tension of canola oil were reduced by 5.50%, 94.74%, 95.03%, and 9.38%, respectively, upon enzymatic interesterification to conform to standard requirements. Similarly, increased |mud ability to pump fluids and possibility of cold temperature environment can be achieved with the reduction in pour point and cloud point, respectively, of the produced canola oil ester. Finally, the produced ester showed no aromatic content as confirmed from its FTIR analysis which indicates its nontoxicity, biodegradability, and environmental friendliness.
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Dike, Ali Sinan, and Ulku Yilmazer. "Improvement of organoclay dispersion into polystyrene-based nanocomposites by incorporation of SBS and maleic anhydride-grafted SBS." Journal of Thermoplastic Composite Materials 33, no. 4 (November 3, 2019): 554–74. http://dx.doi.org/10.1177/0892705719882998.
Повний текст джерелаАнотація:
In this study, organoclay-containing polystyrene (PS)-based nanocomposites were fabricated by extrusion in the presence of thermoplastic elastomer modifiers. Styrene–butadiene–styrene (SBS) rubber was used as the elastomeric compatibilizer and maleic anhydride (MA) was grafted onto SBS rubber at different ratios. Grafting was made via melt blending. Cloisite® 30B was used as the organoclay and it was added to PS and PS/SBS blends using a corotating twin-screw extruder, followed by injection molding. Clay loading was kept constant as 2 wt%, and the elastomer content was varied between 0 and 40 wt% throughout the study. MA grafted SBS enhanced the intercalation/exfoliation of clay layers resulting in higher tensile strength, modulus, elongation at break, and impact strength with respect to neat PS. Composites containing 15 wt% MA grafted SBS displayed the optimum average domain size resulting in the high impact strength without deteriorating the tensile strength and modulus values. Elastomer addition increased the glass transition temperature of the samples due to branching or cross-linking during extrusion. PS and PS/SBS exhibited similar melt flow index values with their organoclay-containing composites. MA acted as a plasticizer and decreased viscosity. Scanning electron microscopy study indicated that dispersion of clay layers was observed at the PS-SBS interphase and also in the elastomer phase. Intercalated and exfoliated structures of organoclay layers were confirmed by X-ray diffraction and transmission electron microscopy analyses.
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Tziourtzioumis, Dimitrios N., and Anastassios M. Stamatelos. "Diesel-Injection Equipment Parts Deterioration after Prolonged Use of Biodiesel." Energies 12, no. 10 (May 22, 2019): 1953. http://dx.doi.org/10.3390/en12101953.
Повний текст джерелаАнотація:
The application of biodiesel blends is known to significantly affect operation of diesel-injection equipment, especially the injectors and fuel pump. This paper summarizes experience on this subject from burning fuel blends with high-percentages of biodiesel (up to 70%) on a common-rail, high-pressure-injection diesel engine and a conventional DI engine. Both engines were unable to start after running for 100 h each and staying shut off for more than two months. In order to understand the wear characteristics of the injector nozzle, pump pistons, and elastomer parts (in the case of the high-pressure pump of the common-rail engine), due to the prolonged operation with high-percentage biodiesel blends, their injectors and pumps parts were examined and compared by performing normal photography and low magnification microscopy. Additionally, the various elastomer parts of the high-pressure fuel pump of the common-rail engine were examined for wear and deterioration. The results are compared with existing literature results from other researchers. The observed deterioration of diesel-injection equipment is caused by use of high-percentage biodiesel blends and subsequent engine shut down.
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NAKAUCHI, HIDEO. "Special issue "Development and Perspective of Elastomer Engineering". Deterioration of Rubber Composite." NIPPON GOMU KYOKAISHI 64, no. 9 (1991): 566–78. http://dx.doi.org/10.2324/gomu.64.566.
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Sowińska, Anna, Magdalena Maciejewska, Laina Guo, and Etienne Delebecq. "Effect of SILPs on the Vulcanization and Properties of Ethylene–Propylene–Diene Elastomer." Polymers 12, no. 6 (May 27, 2020): 1220. http://dx.doi.org/10.3390/polym12061220.
Повний текст джерелаАнотація:
Ionic liquids (ILs) are increasingly used in elastomer technology due to unique physico-chemical properties, which are stable at the temperature of preparation and during processing of rubber compounds. The latest IL application concept is supported ionic liquid-phase (SILP) materials, where an IL film is immobilized on the solid phase. The main aim of this work was studying the influence of IL immobilized on the surface of solid supports, such as silica and carbon black, on the vulcanization process, mechanical properties, and thermal behavior of ethylene–propylene–diene (EPDM) elastomer. Application of the SILP materials enabled the control of EPDM vulcanization without deterioration of the crosslink density, damping properties, thermal stability, and resistance of the vulcanizates to thermo-oxidative aging. Slight improvements in the tensile strength and hardness of the vulcanizates were observed.
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KURAMASU, HAJIME. "Special issue "Recent Development of Instrumental Analytical Methods". Spectroscopic Approach to the Deterioration of Elastomer." NIPPON GOMU KYOKAISHI 67, no. 11 (1994): 798–806. http://dx.doi.org/10.2324/gomu.67.798.
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Kakhramanov, N. T., A. D. Guliev, and V. S. Osipchik. "Dynamically vulcanized elastoplastics based on the technologically compatible random polypropylene and butadiene-nitrile rubber." Plasticheskie massy 1, no. 11-12 (January 2, 2020): 30–33. http://dx.doi.org/10.35164/0554-2901-2019-11-12-30-33.
Повний текст джерелаАнотація:
The basic physicomechanical properties of dynamically vulcanized elastoplastics based on random polypropylene and nitrile butadiene rubber are considered. It is shown that the higher the concentration of nitrile groups in the nitrile-butadiene rubber, the higher the limiting concentration of the elastomer to appear rubber-like properties in elastoplastics. In order to improve the compatibility of the components of the mixture, a graft copolymer of polypropylene with methacrylic acid was used as a compatibilizer. In contrast to sulfuric vulcanization, peroxide one contributes to a signifi cant deterioration of the melt fl ow index of elastoplastics.
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Li, Ruilong, Na Wang, Zhuyu Bai, Shaopeng Chen, Jianbing Guo, and Xiaolang Chen. "Microstructure design of polypropylene/expandable graphite flame retardant composites toughened by the polyolefin elastomer for enhancing its mechanical properties." RSC Advances 11, no. 11 (2021): 6022–34. http://dx.doi.org/10.1039/d0ra09978c.
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Bonato, Jasminka, Nikola Tomac, and Vinko Tomas. "ASSESSMENT OF THE INFLUENCE OF RADIATION AND DEFORMATION ON THE ELASTOMER DETERIORATION BY USING FUZZY LOGIC." Brodogradnja 68, no. 2 (February 2, 2017): 63–77. http://dx.doi.org/10.21278/brod68205.
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Kobelchuk, Yu M., Yu N. Vashchenko, and L. S. Holub. "Application of 4,4'-dihydroxydiphenylsulfone and its polymethylol derivative as additives in elastomeric materials." Voprosy Khimii i Khimicheskoi Tekhnologii, no. 4 (July 2021): 66–72. http://dx.doi.org/10.32434/0321-4095-2021-137-4-66-72.
Повний текст джерелаАнотація:
One of the ways to improve the quality of elastomeric materials is the modification of the elastomeric matrix as well as the use of multifunctional ingredients that can function as stabilizers, vulcanizing group components and compatibilizers (i.e. substances that increase compatibility in polymer heterogeneous systems). Compounds that can be used as binders in composite materials of different composition and ensure the environmental friendliness of their production and application are considered to be promising. Among such compounds, the reaction products of 4,4'-dioxydiphenylsulfone with formaldehyde attract a particular interest since they have a lower degree of toxicity than the phenol-formaldehyde resins. This work revealed the effect of 1, 2, and 4 parts by weight of 4,4'-dihydroxydiphenylsulfone and its polymethylol derivative on technological and physical-mechanical properties of elastomeric compositions. We showed the stabilizing activity of the investigated additives in rubbers based on carbochain unsaturated rubbers. The surface of the crushed vulcanizate was modified. It was determined that the addition of modified crushed vulcanizate to the composition of rubber mixtures improves the quality of rubbers. We showed the possibility of replacing traditional anti-aging agents without deterioration of the properties of finished products.
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Lokhande, Rajkiran, Tushar Patil, Avinash Mahamuni, Krishnakumar Jaju, Ketan Gore, and Rajlaxmi Rai. "COMPARISON OF THE FORCE DETERIORATION OF DIFFERENT ORTHODONTIC ELASTOMERIC MATERIALS IN ARTIFICIAL SALIVA: AN IN VITRO STUDY." International Journal of Clinical and Biomedical Research 1, no. 1 (January 27, 2019): 41–44. http://dx.doi.org/10.31878/ijcbr.2018.51.11.
Повний текст джерелаАнотація:
The orthodontist must be able to choose an elastic band with force-extension characteristics that are most suitable for the particular tooth movement required. From a clinician view it would be mandatory not only to know the clinical aspect of these elastics but also their basic properties, in order to extract the most out of these polymers. Stretching of elastics are thought to be the primary cause of force degradation of orthodontic elastics but there is evidence of increased force degradation of elastics when exposed to various types of substances like artificial saliva, phosphoric acid and citric acid. Orthodontic elastics have received mixed reactions of practitioners as reported by the vendors of orthodontic supplies. The present study is designed to compare the force deterioration of different orthodontic elastomeric materials in artificial saliva medium. There was a force deterioration over time in all materials, being greatest on the seventh day of the experiment, especially more in the chains; From the third to the fourth week there was no noticeable force degradation in either group; By the end of the experiment, modules showed less deterioration of the force compared to the chains and threads.
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Roland, C. M., and J. W. Sobieski. "Anomalous Fatigue Behavior in Polyisoprene." Rubber Chemistry and Technology 62, no. 4 (September 1, 1989): 683–97. http://dx.doi.org/10.5254/1.3536268.
Повний текст джерелаАнотація:
Abstract Annealing of a polyisoprene-based elastomer can resuit in significant changes in its failure properties, the nature of which depends on the deformation of the rubber during the annealing. Although a deterioration of properties from low-strain annealing and improved performance from high-strain annealing may be contrary to intuition, the mechanisms which underlie these annealing effects are well known. The behavior described herein simply represents other manifestations of these phenomena. These alterations in performance, moreover, are readily induced at strains within the range of conventional fatigue and crackgrowth experimentation, and thus demonstrate some of the difficulties in relating laboratory characterizations to the performance of materials in other environments.
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Goiato, Marcelo Coelho, Aldiéris Alves Pesqueira, Amália Moreno, Daniela Micheline dos Santos, Marcela Filié Haddad, and Lisiane Cristina Bannwart. "Effects of pigment, disinfection, and accelerated aging on the hardness and deterioration of a facial silicone elastomer." Polymer Degradation and Stability 97, no. 9 (September 2012): 1577–80. http://dx.doi.org/10.1016/j.polymdegradstab.2012.06.033.
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Leshkevich, A. V., Z. S. Shashok, N. R. Prokopchuk, E. P. Uss, and O. V. Karmanova. "Compatibility study of plasticizing additives based on recycled raw materials in the petrochemical with elastomer matrix." Proceedings of the Voronezh State University of Engineering Technologies 81, no. 4 (February 11, 2020): 190–95. http://dx.doi.org/10.20914/2310-1202-2019-4-190-195.
Повний текст джерелаАнотація:
The compatibility of SRI-3 polyisoprene rubber with plasticizing additives based on recycled petrochemical raw materials (DVCH, DVCH with modifying additive (MA) in the amount of 0.5; 1.0; 2.5; 5.0 and 10.0% mas.) in comparison with industrial petroleum oils (PO-6 and I-20). The compatibility of polymer with a plasticizer additive was evaluated by of experimental data using the equilibrium swelling method. As a result, the polimer-plasticizer interaction parameter (Huggins parameter) and the diffusion coefficient of plasticizing components in the polymer volume were determined. Analysis of the experimental data showed that the plasticizer component based on recycled petrochemical raw materials DVCH has better compatibility with the elastomer matrix SRI-3 compared to industrial oils PO-6 and I-20. Was established that the use of modifying additives in the amount of 0.5 and 1.0% mas. leads to an increase in the diffusion coefficient and a decrease in the Huggins parameter in comparison with DVCH in individual form It indicates their better compatibility with rubber SRI-3. Was shown that a further increase in the content of modifying additive (more than 1.0% mas.) in the volume of plasticizing component DVCH is impractical. This leads to a deterioration of the parameters, and, as a result, to a worse compatibility with the elastomer.
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Liu, Xiaoxiao, Wenbin Zhang, Peng Sun, and Ming Liu. "Time-Dependent Seismic Fragility of Typical Concrete Girder Bridges under Chloride-Induced Corrosion." Materials 15, no. 14 (July 19, 2022): 5020. http://dx.doi.org/10.3390/ma15145020.
Повний текст джерелаАнотація:
Recent studies highlighted the importance of the combined effects of prestress loss and corrosion deterioration for concrete girder bridge structures when the effect of damage on the performance level is estimated. The multi-deterioration mechanisms connected with chloride erosion include the cross-sectional area loss of longitudinal bars and stirrups, the reduction in the ductility, the decrease in the strength of steels and the strength loss of concrete in RC columns. For the corroded RC columns and corroded elastomeric bridge bearings, analytical models of the material degradation phenomena were employed for performing the probabilistic seismic performance analysis, which could obtain the system seismic fragility of aging bridges by considering the failure functionality of multiple correlated components (e.g., columns, bearings). The combined effects of prestress loss and cracking were also considered when developing time-dependent system seismic fragility functions. Here, a typical multi-span reinforced concrete girder bridge was used as a case study for studying the time-variant seismic performance. The results revealed the importance of the joint effects of the multi-deterioration mechanisms when modeling the time-dependent seismic fragility of aging bridge systems, as well as the significance of considering the combined effects of prestress loss and cracking.
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Bérubé, Marc-André, Benoit Fournier, and Jean Frenette. "Détérioration de fondations de pylones d'ancrage de lignes de transport d'électricité par des réactions alcalis–granulats, performance mécanique et réparation du béton." Canadian Journal of Civil Engineering 16, no. 6 (December 1, 1989): 945–59. http://dx.doi.org/10.1139/l89-138.
Повний текст джерелаАнотація:
A number of concrete tower foundations that support power lines over the St. Lawrence River in the Quebec City area were showing deterioration related to alkali–aggregate reactions. The aggregates involved are siliceous limestones commonly exploited in the area. Many foundations have been cored down to the rock basement and samples were taken all along the cores for petrographic examination and mechanical testing. These studies show that the concrete presents some mechanical weaknesses but only in the first decimeters close to the surface, even if the entire mass of the concrete foundations is affected by alkali–aggregate reactions. The results also suggest that the deterioration is isotropic in the concrete and that the compressive strength is affected as much as the tensile (Brasilian) strength. Various types of corrective measures were applied to the deteriorated components: sealing of cracks, removing of the deteriorated concrete and replacement with a new concrete containing silica fumes in addition to a low alkali cement, insertion and posttensioning of steel rods in some components, application of water-tight elastomer liners on the exposed concrete surface, etc. Key words: concrete, aggregate, cement, alkali–aggregate reaction, expansion, mechanical strength, repair, protection.
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Oßwald, K., K. Reincke, S. Döhler, U. Heuert, B. Langer, and W. Grellmann. "Aspects of the Ageing of Elastomeric Materials." International Polymer Science and Technology 44, no. 12 (December 2017): 1–10. http://dx.doi.org/10.1177/0307174x1704401201.
Повний текст джерелаАнотація:
Rising raw materials prices and increasing customer demands for reliability and durability mean that there is huge interest in finding more and more ways of improving the service life of elastomeric products, for economic and environmental reasons, by boosting their resistance under the relevant operating conditions. The material-dependent oxygen absorption capacity and oxygen permeability play an important role in oxidative ageing processes and their modelling. Thus, ageing resistance is substantially dependent on the rate of oxygen diffusion into the bulk of the material in the case of thermo-oxidative attack. To evaluate the resistance of materials to external influences, artificial ageing methods are used in practice. The advantage of these methods is that, as a result of intensifying the test parameters, e.g. temperature and humidity, the ageing processes in the vulcanisate are accelerated. Within the scope of this study, the influence of accelerated ageing on the mechanical and viscoelastic properties of mainly carbon-black-filled natural rubber (NR) vulcanisates was studied in an oxygen atmosphere at elevated temperature and in oxygen with solar radiation. The filler content was varied and the antioxidant IPPD was used. The analyses showed that, as well as mechanical properties such as hardness and tensile strength, the viscoelastic properties are also affected, depending on the ageing time and the type of ageing. In addition to the investigation of mechanical properties, a direct evaluation of the material change was carried out for selected samples by means of analytical tests. The investigations showed the deterioration of the antioxidant activity.
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Azrem, Ahmad Azmi, N. Z. Noriman, M. N. Razif, and S. T. Sam. "Physical and Morphological Properties of Styrene Butadiene Rubber/Recycled Chloroprene Rubber (SBR/CRr) Blends - The Effects of TOR as a Compatibilizer." Key Engineering Materials 594-595 (December 2013): 862–66. http://dx.doi.org/10.4028/www.scientific.net/kem.594-595.862.
Повний текст джерелаАнотація:
Elastomer blends are widely used in rubber products for a variety of reasons, which include improved physical properties, improved service life, easier processing, and reduced production cost [. Butadiene and chloroprene (2-chloro-1,3 butadiene) are related monomers [. Blending of SBR with CR has been done to obtain better crystallisation resistance, better compression set resistance, lower brittleness temperature and enhanced resistance to sunlight deterioration as compared with CR alone. Other important properties, such as oil, heat, flame and ozone resistance, decrease as the amount of SBR increases [. It is possible to improve the phase morphology of SBR/CR blend by incorporating 5±10 phr of a modified copolymer that has segments chemically identical to SBR and CR phases. Addition of halocarbenes to polymers has been reported since a long time; however, available information on the commercial application on such modified polymers is limited [.
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Ballesteros, Alberto, Ester Laguna-Gutiérrez, and Miguel Ángel Rodríguez-Pérez. "SEBS as an Effective Nucleating Agent for Polystyrene Foams." Polymers 13, no. 21 (November 6, 2021): 3836. http://dx.doi.org/10.3390/polym13213836.
Повний текст джерелаАнотація:
Different percentages of an elastomeric phase of styrene-ethylene-butylene-styrene (SEBS) were added to a polystyrene (PS) matrix to evaluate its nucleating effect in PS foams. It has been demonstrated that a minimum quantity of SEBS produces a high nucleation effect on the cellular materials that are produced. In particular, the results show that by adding 2% of SEBS, it is possible to reduce the cell size by 10 times while maintaining the density and open cell content of the foamed materials. The influence of this polymeric phase on the glass transition temperature (Tg) and the shear and extensional rheological properties has been studied to understand the foaming behavior. The results indicate a slight increase in the Tg and a decrease of the shear viscosity, extensional viscosity, and strain hardening coefficient as the percentage of SEBS increases. Consequently, an increase in the density and a deterioration of the cellular structure is detected for SEBS amounts higher than 3%.
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Acton, Claire, Nicola Ivins, Paul Bainbridge, and Paul Browning. "Management of incontinence-associated dermatitis patients using a skin protectant in acute care: a case series." Journal of Wound Care 29, no. 1 (January 2, 2020): 18–26. http://dx.doi.org/10.12968/jowc.2020.29.1.18.
Повний текст джерелаАнотація:
Objective: Incontinence-associated dermatitis (IAD) is a common type of irritant contact dermatitis. It is categorised by persistent erythema and can be associated with denudation and/or colonisation and infection. IAD is challenging to treat and affects 3.4–50% of patients. This case series evaluates a novel, elastomeric, advanced skin protectant (3M Cavilon Advanced Skin Protectant) in a UK acute health-care setting, for the management of IAD in patients suffering from moisture-associated skin damage (MASD) in the sacral/genital area. Method: The patient's skin was assessed by clinicians using the GLOBIAD classification tool at the point of recruitment and to monitor progress throughout the study period. The product was applied as a single layer in accordance with the instructions for use. Patients, when able, were asked to assess their own pain level using the Wong-Baker FACES pain scale. Photographs were taken as part of the ongoing assessment. Results: The skin protectant was used on average every 2.28 days. Of the 18 IAD patients recruited, 79% (n=11) were classified as IAD-free, based on the GLOBIAD categorisation tool, by the end of the evaluation period. Skin deterioration during the evaluation period was seen in one patient (6%), and of the patients able to complete pain assessments, 55% (n=6) reported a reduction in pain. Conclusion: These results suggest that the elastomeric skin protectant, applied every three days, plays a role in the improvement of IAD. The skin protectant adheres to wet and weeping partial-thickness wounds and may aid IAD management. Reducing application to every third day supports a change in practice which may offer benefits to patients and caregivers.
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González, Arturo, and Hussein Aied. "Application of the Hilbert-Huang Transform for Identification of Changes in Boundary Conditions of a Bridge Using Vibration Data due to Traffic." Key Engineering Materials 569-570 (July 2013): 892–99. http://dx.doi.org/10.4028/www.scientific.net/kem.569-570.892.
Повний текст джерелаАнотація:
The translational restraints associated to pin and rocker bearings are typically idealized in the form of fixed and free conditions. However, elastomeric bearings need to be represented with springs to reasonably predict the time- and frequency-domain response of bridges under traffic-induced vibrations. Therefore, changes in the response of these bearings are common as a result of aging, deterioration, variation in loading levels and/or environmental changes. The latter makes difficult to discern if changes in the frequency content of the structural response to ambient vibration are due to changes in temperature, changes in normal operational loads or the occurrence of damage. In this paper, the bridge is idealized by a beam model supported on a hysteretic translational sprung support. The purpose is twofold: (a) to gather a better understanding of the variations of the bridge response with bearing performance; and (b) to be able to quickly identify an anomaly in the bearing. Empirical Mode Decomposition and the Hilbert-Huang Transform are employed to capture changes in the bearing stiffness from the bridge response.
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Diekmann, Astrid, Marvin C. V. Omelan, and Ulrich Giese. "Influence of Carbon Nanotube-Pretreatment on the Properties of Polydimethylsiloxane/Carbon Nanotube-Nanocomposites." Polymers 13, no. 9 (April 21, 2021): 1355. http://dx.doi.org/10.3390/polym13091355.
Повний текст джерелаАнотація:
Incorporating nanofillers into elastomers leads to composites with an enormous potential regarding their properties. Unfortunately, nanofillers tend to form agglomerates inhibiting adequate filler dispersion. Therefore, different carbon nanotube (CNT) pretreatment methods were analyzed in this study to enhance the filler dispersion in polydimethylsiloxane (PDMS)/CNT-composites. By pre-dispersing CNTs in solvents an increase in electrical conductivity could be observed within the sequence of tetrahydrofuran (THF) > acetone > chloroform. Optimization of the pre-dispersion step results in an AC conductivity of 3.2 × 10−4 S/cm at 1 Hz and 0.5 wt.% of CNTs and the electrical percolation threshold is decreased to 0.1 wt.% of CNTs. Optimum parameters imply the use of an ultrasonic finger for 60 min in THF. However, solvent residues cause a softening effect deteriorating the mechanical performance of these composites. Concerning the pretreatment of CNTs by physical functionalization, the use of surfactants (sodium dodecylbenzenesulfonate (SDBS) and polyoxyethylene lauryl ether (“Brij35”)) leads to no improvement, neither in electrical conductivity nor in mechanical properties. Chemical functionalization enhances the compatibility of PDMS and CNT but damages the carbon nanotubes due to the oxidation process so that the improvement in conductivity and reinforcement is superimposed by the CNT damage even for mild oxidation conditions.
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Roh, Hyun-gyoo, Sunghoon Kim, Jungmin Lee, and Jongshin Park. "Effect of Low-Temperature Pyrolysis on the Properties of Jute Fiber-Reinforced Acetylated Softwood Kraft Lignin-Based Thermoplastic Polyurethane." Polymers 10, no. 12 (December 3, 2018): 1338. http://dx.doi.org/10.3390/polym10121338.
Повний текст джерелаАнотація:
Short jute fiber-reinforced acetylated lignin-based thermoplastic polyurethane (JF reinforced ASKLTPU) was prepared and characterized as a short-fiber-reinforced elastomer with carbon-neutrality and biodegradability. The acetylated softwood kraft lignin-based thermoplastic polyurethane (ASKLTPU) was prepared with polyethylene glycol (PEG) as a soft segment. Short jute fiber was modified using low-temperature pyrolysis up to the temperatures of 200, 250, and 300 °C in order to remove non-cellulosic compounds of jute fibers for enhancing interfacial bonding and reducing hydrophilicity with the ASKLTPU matrix. JF-reinforced ASKLTPUs with fiber content from 5 to 30 wt % were prepared using a melt mixing method followed by hot-press molding at 160 °C. The JF-reinforced ASKLTPUs were characterized for their mechanical properties, dynamic mechanical properties, thermal transition behavior, thermal stability, water absorption, and fungal degradability. The increased interfacial bonding between JF and ASKLTPU using low-temperature pyrolysis was observed using scanning electron microscopy (SEM) and also proved via interfacial shear strength measured using a single-fiber pull-out test. The mechanical properties, thermal properties, and water absorption aspects of JF-reinforced ASKLTPU were affected by increased interfacial bonding and reduced hydrophilicity from low-temperature pyrolysis. In the case of the degradation test, the PEG component of ASKLPTU matrix highly affects degradation and deterioration.
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Ibrahim AInuwa, Abubakar Musa Yola, Hassan Abba Musa, Victor Mlanga, and Umar Shuaibu. "Bridge assessment: A case study of Ajaokuta-Itobe Bridge, Kogi State." World Journal of Advanced Engineering Technology and Sciences 2, no. 2 (June 30, 2021): 066–78. http://dx.doi.org/10.30574/wjaets.2021.2.2.0040.
Повний текст джерелаАнотація:
This report summarizes the assessment carried out as a result of the public uproar on the degree of safety of the Ajaokuta/Itobe Bridge in Kogi state. The public outcry was as a result of a severe damaged expansion joints of the bridge. Visual inspection and concrete strength test were carried out to ascertain the safety condition of Itobe Bridge. Seven out of the total number of eight expansion joint covers were damaged and out of place while all the elastomeric bearings were in good working condition. The scouring of the river bed was not visually pronounced except little at the abutment side of the Abuja-Ayingba approach which is attributed to change of water course. Farming activities within the vicinity of the bridge embankment has no effects on the bridge foundation. The compressive strength test result of some bridge elements selected shows that the values are within the satisfactory range. The assessment recommended the lengthening and desilting of the drainage pipes to prevent further corrosion of the concrete and steel members. The use of sand blasting and repainting of the steel beams was also recommended to protect them from further corrosion. Maintenance of cracks on the reinforced concrete abutment and piers should be carried out. The use of sheet piles filled with compacted sand or gabions around the exposed piles caps to protect the foundation was recommended. Shoreline protection measures should be used in protecting the bridge eroded embankment. Seven out of eight expansion joint devices were damaged therefore exposing the elements of the structure that are otherwise protected by the joint devices. The openings about 47cm-53cm becomes a conduit by which moisture, abrasives, chemicals, and other debris are deposited on the superstructure and substructure below the opening, thereby causing extensive damage. The expansion joints devices should be fixed with proper elastomeric strip seal to protect the bridge from further deterioration.
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Andrade Borges, Emilia, Eva O. L. Lantsoght, Sebastián Castellanos-Toro, and Johannio Marulanda Casas. "Modeling and analysis of a prestressed girder bridge prior to diagnostic load testing." ACI Avances en Ciencias e Ingenierías 13, no. 2 (November 22, 2021): 23. http://dx.doi.org/10.18272/aci.v13i2.2295.
Повний текст джерелаАнотація:
Progressive deterioration is a problem that affects road infrastructure, especially bridges. This requires the development of methods for its adequate detection and revision, one of them being load testing. Within load testing, finite element analysis (FEA) models provide initial information to understand the behavior of a structure and plan accordingly, which represents a fundamental step towards a precise structural evaluation of a bridge. This study focused on the modeling and analysis of the static response of the bridge over the river Lili in Cali, Colombia, a prestressed girder bridge programmed to undergo a diagnostic load test. A linear FEA model was created with information from a manual survey and from other bridges’ plans designed and built under the regulations in force at the time. Due to the absence of plans and design specifications for the bridge, variations were applied to certain model parameters (stiffness of diaphragms and elastomeric bearings), to quantify their effect on the overall behavior of the bridge. The analysis included obtaining the critical position for the design vehicles, the transversal distribution of stresses and determining the influence of the variation parameters in the response of the structure. Results showed that the critical combinations for bending moment and shear were when the loads were the closest to the exterior girders, being these elements the most affected. The variation on the modulus of elasticity for the diaphragms and the stiffness of the elastomeric bearings did not significantly influence the results for bending moment and shear, nor the critical position. Girder distribution factors (GDF) from the model were compared to previous research, finding similarities in shape and value with other FEA models and experimental results. Finally, an instrumentation plan focused on the girders of the bridge was proposed based on the zones where the maximum effects are expected. The findings in this study show how linear FEA models provide initial but relevant information regarding the critical position of design vehicles, the distribution of stresses and the expected values for bending moment and shear under design loads.
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Liu, Yunpeng, Shuo Jiang, Xiaozhou Fan, and Yuan Tian. "Effects of Degraded Optical Fiber Sheaths on Thermal Aging Characteristics of Transformer Oil." Applied Sciences 8, no. 8 (August 19, 2018): 1401. http://dx.doi.org/10.3390/app8081401.
Повний текст джерелаАнотація:
With the development of fiber optic sensing technology, optical fiber sensors have been widely used in online monitoring of power transformers. To investigate the influence of aging fiber sheaths on transformer oil, two kinds of special optical fibers with thermoplastic polyester elastomer (TPEE) and poly tetra fluoroethylene (PTFE) as sheaths underwent thermally accelerated aging in transformer oil at 130 °C. The volume resistivity, dielectric dissipation factor (DDF), and breakdown voltage of the oil were measured to indicate insulation strength. The water content and acid value of the oil were measured and fitted to predict the aging tends. The thermal aging characteristics of the oil were quantitatively compared and results showed two kinds of optical fibers could exacerbate all the physical and chemical parameters of oil, and the TPEE sheath had a more significant impact on the oil. The reasons contributing to such phenomenon were analyzed using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Both TPEE and PTFE were depolymerized in high-temperature transformer oils, producing water and small molecule hydrocarbon groups. The accumulation of small hydrocarbon groups promoted positive feedback of pyrolysis in the oil. The free hydrogen produced by oil pyrolysis increased the acidity of the oil, which in turn increased the solubility of the water produced by sheath depolymerization. The chain depolymerization of TPEE was more severe than that of PTFE, further exacerbating the deterioration of TPEE-containing oil.
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Bogomolov, Pavel O., Vladimir T. Ivashkin, Alexey O. Bueverov, Igor V. Maev, Olga I. Sagalova, Snezhana S. Sleptsova, Nikolay D. Yushuk, Denis A. Gusev, Konstantin V. Zhdanov, and Vladimir P. Chulanov. "Efficacy and safety of bulevirtide in patients with chronic hepatitis D and compensated cirrhosis." Terapevticheskii arkhiv 93, no. 11 (November 15, 2021): 1290–99. http://dx.doi.org/10.26442/00403660.2021.11.201163.
Повний текст джерелаАнотація:
Aim. To study the efficacy and safety of bulevirtide, the HBV and HDV entry inhibitor.
Materials and methods. Analysis of the results of using bulevirtide in randomized controlled open-label comparative studies MYR202 and MYR203 in 56 patients with chronic hepatitis D and compensated cirrhosis, in monotherapy and combination with pegylated interferon alpha-2a (PEG-IFN).
Results. Monotherapy with bulevirtide for 24 weeks in the MYR202 study in 46 patients with compensated liver cirrhosis demonstrated: 1) a high rate of virological (100%) and biochemical response (alanine aminotransferase normalization rate 45.7%), 2) superiority of bulevirtide in efficacy over the control group (tenofovir), 3) comparability of treatment efficacy in patients with and without cirrhosis, 4) no progression of liver fibrosis with elastometry in most patients.
Treatment with bulevirtide in monotherapy and combination with PEG-IFN for 48 weeks in 10 patients with compensated liver cirrhosis in the MYR203 study was accompanied by a high rate of virological response (80%) and normalization of alanine aminotransferase (70%).
Bulevirtide was well tolerated, there was no deterioration in tolerability compared with patients without cirrhosis, there were no serious adverse events and cases of treatment cancellation due to adverse events.
Conclusion. Bulevirtide is recommended as the first line of treatment for chronic hepatitis D in patients with compensated cirrhosis in monotherapy and combination with PEG-IFN.
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Rohman, Géraldine, Sylvie Changotade, Sophie Frasca, Salah Ramtani, Anne Consalus, Credson Langueh, Jean-Marc Collombet, and Didier Lutomski. "In vitro and in vivo proves of concept for the use of a chemically cross-linked poly(ester-urethane-urea) scaffold as an easy handling elastomeric biomaterial for bone regeneration." Regenerative Biomaterials 6, no. 6 (April 23, 2019): 311–23. http://dx.doi.org/10.1093/rb/rbz020.
Повний текст джерелаАнотація:
Abstract Bone loss can occur as a result of various pathologies, traumas and injuries and poor bone healing leads to functionally debilitating condition, loss of self-sufficiency and deterioration in life quality. Given the increasing incidence of facial trauma and the emergence of new procedural techniques, advanced scaffolds are currently developed as substitutes for bone tissue engineering. In this study, we investigated the capability of a chemically cross-linked ε-caprolactone-based poly(ester-urethane-urea) (PCLU) scaffold to support bone regeneration. In vitro assays demonstrated that PCLU scaffolds could be colonized by cells through direct cell seeding and cell migration from outside to scaffold inside. Moreover, PCLU scaffolds could provide a suitable environment for stem cells proliferation in a 3D spatial arrangement, and allowed osteogenic differentiation under appropriate induction. In vivo results revealed the osteogenic properties of PCLU scaffolds through a drilled-hole femoral bone defect repair improvement in rats. Using histology and microtomography analysis, we showed that PCLU scaffolds fit well the bone cavity and were eventually entrapped between the newly formed trabeculae. Finally, no sign of inflammation or rejection was noticed. We envision that PCLU scaffolds can provide the clinicians with a substitute having appropriate characteristics for the treatment of bone defects.
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Romanik, Grzegorz, Janusz Rogula, and Paweł Regucki. "Investigation of the Durability of Gaskets in Contact with Bio- and Aviation Fuels." Materials 15, no. 18 (September 9, 2022): 6288. http://dx.doi.org/10.3390/ma15186288.
Повний текст джерелаАнотація:
Care for the natural environment, which can be observed in the tightening of emission standards, has enforced the search for new fuels, especially renewable sources of natural origin. The article presents the results of theoretical and experimental considerations on the impact of aviation biofuels on the materials used for sealing flange joints. The fuel type selected for the test is compatible with aviation fuels. Fuels have been enriched with a bio-additive that changes the technical and physical properties of the fuel. The tested gaskets were made of soft, aramid-elastomeric materials that were flat in shape and without reinforcement. Their commercial names are AFO and AFM. Tests were carried out with the use of a simple flange joint with a fuel reservoir at 373 K. Both fuel loss and the pressure drop on the gasket were measured during a 1000 h period of time. The experiments showed that the seals preserved the technical parameters in the presence of the tested fuels. The fuel loss did not exceed the accepted limits, which demonstrates the suitability of the tested materials for utilization with new types of fuel. However, no unequivocal conclusions can be drawn about the positive or negative impact of bio-additives on the sealing material due to the fact that both an improvement and deterioration in tightness under certain circumstances were observed. Based on the experimental data, a mathematical model was proposed that makes it possible to predict the service life of the gaskets in flange joints in contact with the investigated types of fuel. The potential application of the research results is practical information about the impact of biofuel on the gasket, and hence the information about the possibility of using traditional sealing materials in a new application—for sealing installations for the production, transmission and storage of biofuels.
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Daszko, Sebastian, Carsten Richter, Jens Martin, Katrin Berger, Uta Juda, Christiane Frank-Rotsch, Patrick Steglich, and Karoline Stolze. "Transfer Printable Single-Crystalline Coupons for III-V on Si Integration." ECS Meeting Abstracts MA2022-02, no. 17 (October 9, 2022): 863. http://dx.doi.org/10.1149/ma2022-0217863mtgabs.
Повний текст джерелаАнотація:
The next-generation internet (6G) requires highly functional devices that e.g. realize frequencies in the THz range for higher data rates and lower latencies. Those requirements exceed the physical limits of established CMOS technologies based on silicon (Si). Hence, there is demand for other semiconductor materials with superior electronic and optical properties that complement Si. One of the key candidates is the III-V compound semiconductor, indium phosphide (InP). Due to its high electron mobility and direct band gap, InP-based devices allow access to frequencies >100 GHz and operate at the optical fibre compatible wavelength of 1.55 μm.1 With the perspective of leveraging the advantages of Si-based CMOS technology and III-V semiconductors, hetero-integration of III-V materials on Si is of great interest. However, existing integration approaches entail certain disadvantages: (i) High dislocation densities due to the lattice mismatch of InP and Si for integration via hetero-epitaxial growth;2 (ii) limited integration density and the requirement of accurate alignment for flip-chip integration; and (iii) high process-related losses of Si and III-V materials as well as thermal stress and low thermal conductivity of adhesive layers degrading device performance for wafer/die bonding technologies.3 Another promising approach for III-V-on-Si integration is micro-transfer-printing (μTP) that involves pick-up and transfer of µm-small chips from a source substrate to a target substrate with high alignment accuracy by using an elastomeric stamp. Advantages of μTP are high integration densities and efficient material use. The technique was already implemented for III-V-on-Si photonic integrated circuits by transfer of epitaxial III-V layers.4 However, using sacrificial III-V interlayers for release and adhesives for bonding still leads to transfer issues and low operation temperature for the devices, respectively. We pursue a new approach to hetero-integration of III-V on Si that aims at the transfer of single-crystalline InP coupons onto Si via μTP. This will be achieved by obtaining crystalline coupons with a thickness of d ≤ 10 µm and two polished surfaces that attain low roughness, needed i.a. for µTP. If the high structural quality of the single-crystalline InP source material can be maintained, this process will provide high quality templates for subsequent epitaxial growth. Towards this goal, we developed a sophisticated micro-preparation process in cooperation with the Leibniz Institute for High Performance Microelectronics IHP.5 Starting from 4-inch single crystals with homogeneous, low dislocation density of 2×103 cm- 2 grown at IKZ,6 thinned InP dies were obtained by sawing, grinding and employing an optimized two-step chemical mechanical polishing (CMP). In order to produce µm-sized transfer-printable coupons, the InP dies were micro structured by means of photolithography assisted patterning and wet (under-)etching (Fig. 1). The coupons can then be picked up with a stamp and transferred to the target wafer. Main innovation of this process is the resin which serves as low stress fixing layer for CMP as well as sacrificial layer for later release. The optimized CMP process with abrasive-free final polishing yielded InP platelets of the desired thickness below 10 μm with low thickness deviation < 1 µm and excellent surface roughness of S q ≈ 0.3 nm (Fig. 2a,b,d). This value even meets the requirements for adhesive-free bonding (S q ≤ 2 nm) and subsequent epitaxial growth (S q ≤ 0.5 nm). X-ray rocking curve mapping provides accurate spatial maps of lattice deformations in the material that may be a consequence of the mechanical processing. Rocking curve widths mappings of the 004 reflection of a (001) sample before and after thinning are homogeneous and below 25 arcsec in the majority of the sample area. Overall no signs of systematic crystal quality deterioration in the product platelets compared to bulk samples have been detected. In summary, the feasibility of μm-thin InP platelet fabrication was demonstrated. Final platelets meet the prerequisites of low and uniform thickness, high planarity, low roughness and little crystal quality deterioration. Furthermore, first InP platelets could successfully be patterned to 100–400 µm-sized coupons using optical lithography and wet etching (Fig. 2c). This opens a path to take the next steps towards hetero-integration on Si by means of µTP with high potential for adhesive-free bonding. References [1] J. C. Rode, et al. IEEE Trans. Electron Devices 2015, 62, 2779–2785. [2] Q. Li, K. M. Lau Prog. Cryst. Growth Charact. Mater. 2017, 63, 105–120. [3] X. Guo, et al. J. Semicond. 2019, 40, 101304. [4] J. Zhang, et al. APL Photonics 2019, 4, 110803. [5] IKZ-IHP Patent filed - DE 10 2022 100 661.1. [6] K. Giziewicz, et al. 51st Annual Meeting of the German Association of Crystal Growth, 2021, Berlin. Figure 1
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Nair, Abha, and Sudeep Saratchandran. "Comparative Evaluation of Color Stability of Maxillofacial Silicones Following Accelerated Aging Conditions." FACE, May 23, 2022, 273250162211018. http://dx.doi.org/10.1177/27325016221101899.
Повний текст джерелаАнотація:
Objectives: This study evaluated & compared the effect of both outdoor weathering and accelerated aging conditions on the color stability of two different maxillofacial silicone elastomers. Methods: 72 samples of two different silicones were made and divided into groups of conditioning; Dark storage, accelerated aging and outdoor weathering. Color measurements were recorded by Commission Internationale de l’Eclairage–CIE L*a*b* color system before and after conditioning using spectrophotometer. The data was analyzed by one way ANOVA for multiple Group comparisons, followed by Post hoc Scheffe’s Multiple comparison test for Group wise calculation at the 0.05 significance level. Results: All groups exhibited variation in color over time. The color change (∆E) of the pigmented specimens of all tested High Temperature Vulcanization—HTV & Room Temperature Vulcanization—RTV silicone elastomers were greater than the acceptable value (∆E >3.0). Within non pigmented HTV specimens, none of the tested silicone elastomers showed significant color changes. Within non pigmented RTV specimens, all of the tested silicone elastomers showed significant color changes ( P < .05). The HTV M511 elastomer showed better color stability compared with the RTV A-2186 material. Furthermore, accelerated aging condition was more detrimental and showed significant deterioration of the color properties of both HTV & RTV specimens. Significance: The results of this research will help in providing patients with maxillofacial defects in India, a prosthetic appliance that restores pleasant facial appearance with good esthetics. This will reduce trauma from head & neck cancer surgery & will help people lead a normal life in society.
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Ranpura, Krishna J., Keyurkumar J. Soni, Nipa Prajapati, Dhaval Somani, and Sunny Rathod. "study to evaluate experimentally the effect of hot water, hot green tea, and hot coffee on the tensional strength of orthodontic elastomeric chains." International journal of health sciences, July 15, 2022, 9151–57. http://dx.doi.org/10.53730/ijhs.v6ns5.10709.
Повний текст джерелаАнотація:
Background: The shape memory quality of elastomeric chains makes them useful in orthodontic mechanics, however elastomers also provide significant force reduction in specific instances. Researchers were looking for a correlation between hot drinks and elastomeric chain deformation. Material and Methods: Using various immersion liquids (artificialsaliva, hot water, green tea, and coffee), four groups were evaluated (group 4). It took 7, 14, or 21 days for the elastomeric chains of groups 2, 3, and 4 to reach 70 ±1°C when submerged in the appropriate liquids for 30 seconds twice daily. All samples were preserved in artificial saliva and maintained at a constant 37±1°C temperature in an incubator for long periods of time. Finally, the elastomeric chains were tested for tensile strength deterioration, as well as other properties. Results: Through intragroup comparisons, it was shown that the control demonstrated a statistically significant decrease in tensile strength during the course of the research. When it came to hot water and green tea, the results revealed a statistically significant decrease over the course of seven to fourteen days. The tense atmosphere persisted for a period of 14 to 21 days.