Articoli di riviste: "Room temperature vulcanization"

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Kittipoomwong, Prakorn, e Thirawudh Pongprayoon. "Degree of Vulcanization of Rubber Latex by Capillary Viscometer". Key Engineering Materials 728 (gennaio 2017): 313–17. http://dx.doi.org/10.4028/www.scientific.net/kem.728.313.

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The degree of vulcanization of latex compound was determined by capillary viscometer with controlled temperature to study effect of time and temperature on vulcanization process. The standard equilibrium swelling test was also conducted to assess the degree of vulcanization. A latex compound for medical glove was investigated. The latex viscosity was observed to increase over time at above room temperature condition. On the other hand, the viscosity fluctuated around mean value at room temperature. This is partly consistent with the swell ratio measurement which complete vulcanization was observed at curing temperature of 60 °C.

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Senemar, Mohammad, Behzad Niroumand, Ali Maleki e Pradeep K. Rohatgi. "Synthesis of the in situ aluminum matrix composite through pyrolysis of high temperature vulcanization silicone". Journal of Composite Materials 52, n. 1 (3 aprile 2017): 123–34. http://dx.doi.org/10.1177/0021998317702955.

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In this study, in situ aluminum matrix composites were synthesized through pyrolysis of high temperature vulcanization silicone in commercially pure aluminum melt. For this purpose, 1 to 4 wt% of high temperature vulcanization silicone was added to a vortex of molten aluminum at 750℃ and the resulting slurries were cast in steel dies. Microstructure, hardness, and tensile properties of the as-cast samples were examined at ambient and high temperatures. The results revealed the in situ formation and distribution of reinforcement particles in the matrix. Energy-dispersive X-ray analysis indicated that the formed reinforcement particles consisted of O and Si elements. This confirms the in situ reinforcement formation by pyrolysis of high temperature vulcanization silicone in the melt. The size of the in situ formed particles was mostly in the range of 200–2000 nm. It was shown that the composites synthesized by the addition of 4 wt% high temperature vulcanization had the highest mechanical properties both at ambient and high temperatures. Room temperature hardness, tensile strength, and yield strength of this sample were increased by about 50%, 23%, and 19% compared to the monolithic sample, respectively.

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Fawcett, Amanda S., John B. Grande e Michael A. Brook. "Rapid, metal-free room temperature vulcanization produces silicone elastomers". Journal of Polymer Science Part A: Polymer Chemistry 51, n. 3 (31 ottobre 2012): 644–52. http://dx.doi.org/10.1002/pola.26414.

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Tonkin, Samuel J., Christopher T. Gibson, Jonathan A. Campbell, David A. Lewis, Amir Karton, Tom Hasell e Justin M. Chalker. "Chemically induced repair, adhesion, and recycling of polymers made by inverse vulcanization". Chemical Science 11, n. 21 (2020): 5537–46. http://dx.doi.org/10.1039/d0sc00855a.

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Versloot, P., J. G. Haasnoot, J. Reedijk, M. van Duin e J. Put. "Sulfur Vulcanization of Simple Model Olefins, Part IV: Vulcanizations of 2,3-Dimethyl-2-Butene with TMTD and Activated Zinc Dithiocarbamate/Xanthate Accelerators at Different Temperatures". Rubber Chemistry and Technology 68, n. 4 (1 settembre 1995): 563–72. http://dx.doi.org/10.5254/1.3538757.

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Abstract The mechanism of the accelerated sulfur vulcanization of rubber was studied by the use of 2,3-dimethyl-2-butene (C6H12, TME) as a simple, low-molecular model alkene. Treatment of TME with a mixture of ZnO, S8 and the classical accelerator TMTD at temperatures above 100°C yields a mixture of addition products ((C6H11—Sn—C6H11) ). In the temperature range of 50 up to 100 °C only intermediate products, C6H11—Sn—S(S)CN(CH3)2 are obtained. Room temperature vulcanization is feasible using highly reactive accelerators, such as xanthate derivatives. These derivatives result in formation of the crosslink precursors which are converted to the actual crosslink in the presence of zinc dithiocarbamates. The addition of (secondary) amines enhances the solubility of the dithiocarbamates, and therefore the reactivity of the xanthate/zinc dithiocarbamate combination.

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Yahya, Siti Rohana, Farah Nadiah Hamdan, Azura A. Rashid e Baharin Azahari. "The Effect of Pre-Vulcanization Temperature on Mechanical and Rheological Properties of Starch Filled Natural Rubber Latex Compounds". Advanced Materials Research 858 (novembre 2013): 184–89. http://dx.doi.org/10.4028/www.scientific.net/amr.858.184.

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The main objective of this study was to investigate the effect of the pre-vulcanization temperature on mechanical and rheological properties of starch filled natural rubber (NR) latex films. The 10 phr filler loading of starch was added into the latex prior to the pre-vulcanization process at 60°C to 140°C. The dipped films were cured in the oven at 100°C for 20 minutes and cooled at room temperature for 24 hours before stripping. The rheological properties of NR latex compounds were studied based on the viscosity measurement. The tensile and tear tests of starch filled NR latex films were also carried out. The results indicated that the rheological properties of the latex compounds showed shear thickening behavior where viscosity was increased with the increase in shear rate and pre-vulcanization temperature proportionally. The pre-vulcanization temperature at 80°C showed the optimum mechanical properties of starch filled NR latex films.

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Richers, Casseday P., Jeffery A. Bertke e Thomas B. Rauchfuss. "Syntheses of transition metal methoxysiloxides". Dalton Transactions 46, n. 27 (2017): 8756–62. http://dx.doi.org/10.1039/c6dt04205h.

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Sample, Caitlin S., Sang-Ho Lee, Shaoguang Li, Morgan W. Bates, Valerie Lensch, Brooke A. Versaw, Christopher M. Bates e Craig J. Hawker. "Metal-Free Room-Temperature Vulcanization of Silicones via Borane Hydrosilylation". Macromolecules 52, n. 19 (18 settembre 2019): 7244–50. http://dx.doi.org/10.1021/acs.macromol.9b01585.

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Joseph, Rani. "HXNBR Coating for Improving Aging Resistance of Natural Rubber Products". Rubber Chemistry and Technology 79, n. 4 (1 settembre 2006): 553–60. http://dx.doi.org/10.5254/1.3547951.

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Abstract HXNBR (Hydrogenated Carboxylated Nitrile Rubber) has very good heat ageing resistance and oil resistance. A novel accelerator system is designed to bring about the vulcanization of HXNBR at room temperature. The room temperature cured samples showed good mechanical properties equivalent to those of high (150 °C) temperature cured samples. Natural rubber vulcanizates are highly prone to oxidative and ozone degradation. The oil resistance of natural rubber vulcanizates is also very low. The oil resistance, ozone and oxidative degradation resistance of natural rubber vulcanizates are considerably improved by placing a thin coating of HXNBR over it.

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Li, Dong, Hong Xia Chen, Zhu Chen, Yang Li, Shu Xin Wu e Ji Gui Wang. "Mechanical and Ablative Properties of Polyacrylonitrile(PAN)/RTV Silicone Internal Insulating Composites". Advanced Materials Research 399-401 (novembre 2011): 403–6. http://dx.doi.org/10.4028/www.scientific.net/amr.399-401.403.

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The polyacrylonitrile short fibers/ room temperature vulcanizing silicone rubber (PAN/RTV silicone) composites were prepared by mechanical mixing method and vulcanization at room temperature for 7 days as internal insulator. The effects of the content of fiber on the mechanical and ablative performances for the composites were investigated. The results show that with increasing content of PAN fiber filled, the tensile strength increases, the break elongation decreases, and the ablation rate(Rt) of PAN/silicone composites decreases rapidly at first, then increases. When PAN fiber content is 10phr, the ablation rate(Rt) is 0.06mm/s.

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Versloot, P., J. G. Haasnoot, P. J. Nieuwenhuizen, J. Reedijk, M. van Duin e J. Put. "Sulfur Vulcanization of Simple Model Olefins, Part V: Double Bond Isomerization during Accelerated Sulfur Vulcanization as Studied by Model Olefins". Rubber Chemistry and Technology 70, n. 1 (1 marzo 1997): 106–19. http://dx.doi.org/10.5254/1.3538411.

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Abstract The sulfur vulcanization of unsaturated rubber has been studied with the use of various olefins as simple, low-molecular models. By treatment of these olefins with a mixture of zinc oxide, sulfur, and tetramethylthiuram disulfide (TMTD) at 140 °C, a mixture of dialkenyl sulfides is obtained mimicking crosslinked rubber. Isomerization of the double bond may take place during this reaction, depending on the olefin used. The position of the double bond is on the one hand determined by crosslink formation mechanisms, and on the other hand by isomerization, which takes place at higher temperatures. The position of the equilibrium between isomeric alkenyl sulfides is determined by the increased stability of the sulfide which in itself results from an increased degree of alkyl substitution at the unsaturation. Due to the isomerization reaction, at higher temperatures no mechanism for crosslink formation can be discerned. At room temperature, however, a radical mechanism appears to be predominant during the vulcanization process.

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Zhao, Su Fen, Li Qong Zhang, Xiao Yan Liu, Zhi Gang Tu e Chen Zhang. "Study on the Modification of Concentrated Emulsion of Organosilicon for Propagating Ethanol Permselective Pervaporation Film". Advanced Materials Research 1004-1005 (agosto 2014): 808–11. http://dx.doi.org/10.4028/www.scientific.net/amr.1004-1005.808.

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Vinyl-cyclosilane and styrene were introduced to harden the polysiloxane via radical crosslinking ensuring the independency of the particles and the generation of the micro-channels. After the emulsion had been prepared, when the shape of emulsion particles became stable, the room temperature vulcanization crosslinker was added to form the separation membrane.

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Luo, Weiqi, Zhimin Li, Haihua Luo, Yuting Liu, Guojiang Xia, Hangtian Zhu, Jiayi Zhou et al. "Preparation of Room Temperature Vulcanized Silicone Rubber Foam with Excellent Flame Retardancy". Scanning 2021 (20 maggio 2021): 1–8. http://dx.doi.org/10.1155/2021/9976005.

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To retard the spread of fire in many cases with sealing materials is significant. A series of silicone rubber foam materials were prepared with room temperature vulcanization and foaming reactions. The morphology, chemical structure, cell structure, and thermal stability were investigated and results proved that the synthesis of silicone rubber was successful in a wide range of feed ratios. The fire-retardant tests were carried out to study the fire-proof property of the composite materials, and the excellent performance showed a promising prospect for wide application in sealing materials.

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Chen, Zhu, Dong Li, Ai Juan Shi, Yang Li e Shu Xin Wu. "Properties Characteristics of Silicone Inhibitors". Advanced Materials Research 750-752 (agosto 2013): 43–46. http://dx.doi.org/10.4028/www.scientific.net/amr.750-752.43.

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The short carbon fibers/ room temperature vulcanizing silicone rubber composites were prepared by mechanical mixing method and vulcanization at room temperature for 7 days as internal insulator. The effects of the content of fiber on the mechanical , ablative and adhesive performances for the composites were investigated. The results show that with increasing content of carbon fiber filled, the tensile strength increases, the break elongation decreases, and the ablation rate (Rt) of the composites decreases rapidly at first, then increases. When carbon fiber content is 10phr, the ablation rate (Rt) is 0.076mm/s. no significant differences in adhesive values were obtained yet.

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Coran, A. Y. "New Elastomers by Reactive Processing. Part I. Vulcanizable Precured Alloys from NBR and ACM". Rubber Chemistry and Technology 63, n. 4 (1 settembre 1990): 599–612. http://dx.doi.org/10.5254/1.3538276.

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Abstract The dynamic vulcanization of ACM (the dispersed phase) during its mixing with NBR (the continuous phase) can produce a new type of millable specialty elastomer alloy. The millable dynamic vulcanizate containing the crosslinked dispersed phase can be later mixed with curatives for the continuous phase, fillers, antidegradants, etc. The completed mixture of millable dynamic vulcanizate with the additional curatives (for the NBR), fillers, stabilizers, etc. can then be vulcanized e.g., in a heated mold. Thus, the dynamic vulcanization technique is a means of separately controlling the vulcanization of individual phases of a blend of elastomers. Since the ACM can be completely vulcanized during the dynamic vulcanization stage of the mixing process, the usual postcuring associated with ACM technology is not necessary. Also, since the continuous or external phase is NBR, the prevulcanized millable alloy exhibits processability more similar to that of NBR than to that of ACM. Sticking and splitting on the roll mill is less of a problem after dynamic vulcanization than before dynamic vulcanization. The dynamic vulcanization of the ACM can be achieved by using the soap-sulfur type or the diamine-generator type curatives during the mixing process at elevated temperatures. Compositions filled either with carbon black (N326) or silica (Hisil 233) give compositions of excellent hot-oil resistance and room-temperature set. (Compression-set testing has not yet been done at this early stage of our research.) As in the case of conventional NBR stocks, the silica-filled compositions give excellent hot-air resistance whereas, carbon-black-filled compositions give fair hot-air resistance. In either the black-filled or the silica-filled compositions, provided that at least half of the rubber polymer is ACM, essentially complete resistance to ozone attack is obtained.

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Wu, Zheng-Xue, Le-Qing Fan, Jiao-Juan Chen, Xu-Geng Deng, Tao Tang, Yun-Fang Huang e Ji-Huai Wu. "Amorphous Co-Mo-S nanospheres fabricated via room-temperature vulcanization for asymmetric supercapacitors". Journal of Colloid and Interface Science 649 (novembre 2023): 880–89. http://dx.doi.org/10.1016/j.jcis.2023.06.163.

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Ansar, Asnaeni, Dahlang Tahir, Bualkar Abdullah, Nurhasmi, Siti Fatimah e Jusmawang. "Physical Characteristics of Soft Tissue Phantom from Silicone Rubber Based Vulcanization System". Materials Science Forum 966 (agosto 2019): 194–99. http://dx.doi.org/10.4028/www.scientific.net/msf.966.194.

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Phantom from silicone rubber base material has been synthesized without glycerin and with additional glycerin of 10%, 20%, 30% and 40%. The type of Silicone rubber used is Room Temperature Vulcanized (RTV) 52 with a vulcanization system at room temperature. The concentration of catalyst is 5% from silicone rubber. Sample has characterized by using physical testing, Fourier Transform Infra Red (FTIR) and elastic modulus measurements. Physical testing result shows that phantoms have low degradation and can be applicated in a long time. FTIR data shows a phantom structure is poly (dimethylsiloxane) that has Si-CH3 bond at wavenumber 1261 cm-1 and 802 cm-1 and the Si-O-Si siloxane group at wavenumber 1024 cm-1. The elastic modulus values of phantom are 244 kPa for without glycerin, 210 kPa for 10% glycerin and 126 kPa for 20% glycerin. From the data indicated phantoms has range of the liver elastic modulus value at 0.6-4000 kPa. It means that phantom can be used as a substitute for the soft tissue of the human liver.

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Guo, Mei Xia, Shou Hong Xue, Yuan Yuan Zhang, Zhi Ying Wang e Wen Zhan Zhang. "A Study of Performance on Anti-Pollution Flashover Coating Based on Composite Room Temperature Vulcanized Silicone Rubber". Advanced Materials Research 772 (settembre 2013): 20–24. http://dx.doi.org/10.4028/www.scientific.net/amr.772.20.

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The article totally discusses the influence of polytetrafluoroethylene (PTFE) to the property of room temperature vulcanization silicone rubber (RTV) pollution flashover coating, inclduding hydrophobic, corrosion resistance and heat resistance. It is turned out that the PTFE can effectively improve the corrosion resistance of the coating only if the contents of PTFE has no impact on the mechanical property, flame retaradant and heat resisting property of the coating and highly enhances the hydrophobicity property.

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Vladkova, Todorka G., Alexander Chr Alaminov e Milka G. Pankova. "A Study of the Interactions Between Oligoamidephosphate (OAPh) and Curatives in a Sulphenamide-Accelerated Sulphur Vulcanizing System". Journal of Polymer Engineering 19, n. 2 (1 marzo 1999): 95–108. http://dx.doi.org/10.1515/polyeng-1999-0203.

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Abstract The possible interactions between oligoamidephosphate (OAPli) and the curatives of a sulphenamide-accelerated sulphur vulcanizing system were studied by differential scanning calorimetry, IR-spectroscopy, and X-ray analysis. The interactions in double mixtures were between OAPh and zinc oxide (ZnO) and OAPh and sulphur. The OAPh/ZnO interaction that starts at room temperature seems to be the key for understanding the peculiarities of sulphenamide-accelerated sulphur vulcanization in the presence of OAPh.

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Gümrük, Recep, Uğur Mazlum e R. A. W. Mines. "COMPRESSIVE MECHANICAL BEHAVIORS OF HYBRID COMPOSITE MATERIALS BASED ON MICRO LATTICE STRUCTURE AND RUBBERLIKE MATERIALS". Rubber Chemistry and Technology 88, n. 1 (1 marzo 2015): 147–62. http://dx.doi.org/10.5254/rct.14.86921.

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ABSTRACT This article investigates compressive and energy absorption characteristics for composites obtained by filling stainless steel micro lattice materials, manufactured via the selective laser melting method, with three different rubbers, including room temperature vulcanization silicone, natural rubber, and neoprene rubber. At the stage of building the composites with natural and neoprene rubbers, an experimental setup was designed for these two rubbers to be infiltrated into lattice spaces under vulcanization temperatures and high pressures. The results showed that the composites with silicone and neoprene matrix had a quite similar response as well as a seriously enhanced energy absorbing capacity and plateau stresses, in comparison with the corresponding lattice structures, for especially small sized lattice components. Also, the compression tests of the composite with natural rubber matrix clearly show that there should be no large differences between the individual mechanical properties of each component in the composite, and, in this way, the contribution of each component on the mechanical behavior of composite should be guaranteed to provide the satisfying performance.

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Ravikumar, K., K. Palanivelu e K. Ravichandran. "Vulcanization, Mechanical and Dielectric Properties of Carbon Black/Nanoclay Reinforced Natural Rubber Hybrid Composites". Applied Mechanics and Materials 766-767 (giugno 2015): 377–82. http://dx.doi.org/10.4028/www.scientific.net/amm.766-767.377.

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In this present work the effect of reinforcement of hybrid fillers such as nanoclay and carbon black in natural rubber were studied. Sodium bentonite clay was organically modified with octadecyl amine using cation exchange reaction and characterized by FTIR, XRD and SEM. The organomodified clay with 5 phr loading and also with carbon black (CB) of 25 phr loading were incorporated into natural rubber by using a two-roll mixing mill. Vulcanization, mechanical and dielectric properties were studied. Vulcanization and mechanical properties of natural rubber increases on addition of organomodified clay and also with combination of clay and carbon black compared to unmodified clay and gum compounds. Dielectric properties such dielectric constant, dielectric loss and volume resistivity were studied at room temperature and found improved results of the combination of modified clay/CB filled hybrid composites.

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Gubanski, S. M., e M. S. E. Wang. "Vulcanization influence on TSD currents and wettability of room temperature vulcanized silicone rubber hv insulator coatings". European Transactions on Electrical Power 3, n. 5 (6 settembre 2007): 367–73. http://dx.doi.org/10.1002/etep.4450030508.

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Danikas, M. G., e M. Gubanski. "Vulcanization influence on tsd currents and wettability of room temperature vulcanized silicone rubber hv insulator coatings". European Transactions on Electrical Power 4, n. 4 (6 settembre 2007): 317–19. http://dx.doi.org/10.1002/etep.4450040410.

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Han, Wei, e You Hong Tang. "Water-Swelling Rubber Containing Small Amount of Nanofillers with Enhanced Water Swelling Durability". Advanced Materials Research 774-776 (settembre 2013): 544–47. http://dx.doi.org/10.4028/www.scientific.net/amr.774-776.544.

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A series of water-swelling rubbers (WSR) were prepared by directly mixing room temperature vulcanization-2 components silicone rubber (RTV-2 SR) with superabsorbent polymer (SAP) and nanofiller (s) (halloysite nanotube or/and CaCO3). The effects of component on its mechanical behaviours and water-absorbent properties such as degree of swelling, swelling ratio, and weight loss ratio were investigated. The equilibrium swelling ratio increased with increasing amounts of water-absorbent resin. Well-dispersed nanofiller (s) increased the mechanical properties of WSR and prevented SAP breaking off from the elastomer network to effectively enhance the water-swelling durability of WSR.

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Abbas, Karim, Lukas Hedwig, Nicolae Balc e Sebastian Bremen. "Advanced FFF of PEEK: Infill Strategies and Material Characteristics for Rapid Tooling". Polymers 15, n. 21 (1 novembre 2023): 4293. http://dx.doi.org/10.3390/polym15214293.

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Traditional vulcanization mold manufacturing is complex, costly, and under pressure due to shorter product lifecycles and diverse variations. Additive manufacturing using Fused Filament Fabrication and high-performance polymers like PEEK offer a promising future in this industry. This study assesses the compressive strength of various infill structures (honeycomb, grid, triangle, cubic, and gyroid) when considering two distinct build directions (Z, XY) to enhance PEEK’s economic and resource efficiency in rapid tooling. A comparison with PETG samples shows the behavior of the infill strategies. Additionally, a proof of concept illustrates the application of a PEEK mold in vulcanization. A peak compressive strength of 135.6 MPa was attained in specimens that were 100% solid and subjected to thermal post-treatment. This corresponds to a 20% strength improvement in the Z direction. In terms of time and mechanical properties, the anisotropic grid and isotropic cubic infill have emerged for use in rapid tooling. Furthermore, the study highlights that reducing the layer thickness from 0.15 mm to 0.1 mm can result in a 15% strength increase. The study unveils the successful utilization of a room-temperature FFF-printed PEEK mold in vulcanization injection molding. The parameters and infill strategies identified in this research enable the resource-efficient FFF printing of PEEK without compromising its strength properties. Using PEEK in rapid tooling allows a cost reduction of up to 70% in tool production.

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Ahmad, Mohd Hafizi, Nouruddeen Bashir, Zolkafle Buntat, Yanuar Z. Arief, Abdul Azim Abd Jamil, Mohamed Afendi Mohamed Piah, Abubakar A. Suleiman, Steve Dodd e Nikola Chalashkanov. "Temperature Effect on Electrical Treeing and Partial Discharge Characteristics of Silicone Rubber-Based Nanocomposites". Journal of Nanomaterials 2015 (2015): 1–13. http://dx.doi.org/10.1155/2015/962767.

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This study investigated electrical treeing and its associated phase-resolved partial discharge (PD) activities in room-temperature, vulcanized silicone rubber/organomontmorillonite nanocomposite sample materials over a range of temperatures in order to assess the effect of temperature on different filler concentrations under AC voltage. The samples were prepared with three levels of nanofiller content: 0% by weight (wt), 1% by wt, and 3% by wt. The electrical treeing and PD activities of these samples were investigated at temperatures of 20°C, 40°C, and 60°C. The results show that the characteristics of the electrical tree changed with increasing temperature. The tree inception times decreased at 20°C due to space charge dynamics, and the tree growth time increased at 40°C due to the increase in the number of cross-link network structures caused by the vulcanization process. At 60°C, more enhanced and reinforced properties of the silicone rubber-based nanocomposite samples occurred. This led to an increase in electrical tree inception time and electrical tree growth time. However, the PD characteristics, particularly the mean phase angle of occurrence of the positive and negative discharge distributions, were insensitive to variations in temperature. This reflects an enhanced stability in the nanocomposite electrical properties compared with the base polymer.

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Liu, Yong, Xin Wang, Yu Mei Ding e Wei Min Yang. "Encapsulating and Manufacture Technology Study of Impact-Resisting, Enclosed Soft Aramid Vesicle". Materials Science Forum 686 (giugno 2011): 752–57. http://dx.doi.org/10.4028/www.scientific.net/msf.686.752.

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In order to get a soft and enclosed vesicle which can endure an instantaneous high temperature and super high pressure the soaking technology of aramid fiber with Room Temperature Vulcanization silicon rubber and liquid polyurethane was studied. Then the performance of the composites was tested. Two kinds of rubber vesicle were made, one with metal valve and another without the valve. Using three-dimension braid method, aramid fiber vesicle was made outside the rubber vesicle. Compression test results of the composite vesicle showed that no-valve rubber vesicle had a good match with the aramid one and endured a very large pressure. It can transfer the liquid pressure from inner vesicle to the outer one, which the aramid fiber has excellent mechanical performance and can endure a very large compression.

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Alvarez Grima, M. M., J. G. Eriksson, A. G. Talma, R. N. Datta e J. W. M. Noordermeer. "Mechanistic Studies into the New Concept of Co-Agents for Scorch Delay and Property Improvement in Peroxide Vulcanization". Rubber Chemistry and Technology 82, n. 4 (1 settembre 2009): 442–60. http://dx.doi.org/10.5254/1.3548257.

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Abstract In previous studies a new concept of a peroxide cure system for rubber has been reported where scorch safety and mechanical properties are improved at the same time. This new system consists of the use of a combination of a peroxide, a bismaleimide type co-agent and a sulfur spender for the cure of saturated or low-unsaturated rubber. Several mechanical properties have been studied and were found to be improved by using this curing system, such as tensile strength, moduli, compression set and aging. The present paper deals with the understanding of the reported phenomena. Mechanistic studies have been performed with the aim of comprehending the chemistry that takes place during peroxide vulcanization in the presence of a maleimide co-agent and a sulfur spender. From Nuclear Magnetic Resonance and Infrared analysis the loss of the maleimide unsaturation from the co-agent was observed, due to reaction with the sulfur spender. This reaction already takes place at room temperature, thus previous to peroxide decomposition. Further, Model Compound Vulcanization studies were performed using 3-methylpentane as representative model for the saturated rubber backbone. The reaction products of the peroxide vulcanization of 3-methylpentane in the presence of a maleimide type co-agent and a sulfur donor have been analyzed by means of Liquid Chromatography-Mass Spectrometry. Several reaction products have been identified and a reaction mechanism that explains the scorch delay and the property improvement by the new cure system is proposed.

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Khaigunha, Pattarabordee, e Tanakorn Wongwuttanasatian. "An Improvement on Tracking Resistance of Silicone Rubber Filled with Micro-Wollastonite/Gehlenite Synthesized by Solid-State Reaction". Key Engineering Materials 902 (29 ottobre 2021): 107–11. http://dx.doi.org/10.4028/www.scientific.net/kem.902.107.

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Enhancement of the room temperature vulcanization silicone rubber (RTV) tracking resistance with various filler loadings of synthesized wollastonite against electrical surface tracking was prepared. The X-ray diffraction (XRD), Scanning electron microscope (SEM), and X-ray fluorescent (XRF) techniques were involved in characterizing the synthesized substances. The test method IEC-60587 standard was employed to evaluate the surface tracking resistance. The results obtained from the XRF technique confirmed that the raw materials could be synthesized for wollastonite, while the XRD and SEM techniques revealed the formation of wollastonite (CaSiO3) associated with gehlenite (Ca2Al2SiO7). Moreover, it was found that the electrical surface tracking resistance of composite insulation takes a long time to track when the filler loading is increased more than 5 phr.

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de Risi, F. R., e J. W. M. Noordermeer. "Effect of Methacrylate Co-Agents on Peroxide Cured PP/EPDM Thermoplastic Vulcanizates". Rubber Chemistry and Technology 80, n. 1 (1 marzo 2007): 83–99. http://dx.doi.org/10.5254/1.3548170.

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Abstract Thermoplastic vulcanizates (TPVs) have gained large technical and economic importance. TPVs are characterized by a chemically crosslinked rubber phase, embedded in a thermoplastic matrix, produced by dynamic vulcanization during mixing with the thermoplastic in its molten state. Methacrylate species are investigated as co-agents for peroxide vulcanization of polypropylene/ethylene-propylene-diene-rubber (PP/EPDM) TPVs, whereby the weight fraction of the EPDM is varied from 30, 50 to 70%. Ethylene glycol dimethacrylate (EDMA), trimethylol propane trimethacrylate (TMPTMA, often referred to as TRIM) and zinc dimethacrylate (ZDMA) are tested. A fixed amount of dicumyl peroxide as crosslinker and varying contents of co-agents are employed, the latter to boost EPDM-crosslinking and prevent degradation of the PP by β-scission. Differences observed in mechanical properties point to diverse structures of the crosslink networks of the TPVs. Of the three co-agents, TMPTMA gives the best overall balance of properties by EPDM crosslinking and preventing PP-degradation. This is explained by the positioning of the solubility parameter of this co-agent between those of EPDM and PP, whilst EDMA presents a value far away from either one. ZDMA, although giving very good room temperature properties like tensile strength, shows signs of thermo-reversion of the crosslinks in the compression set measured at 70 °C.

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31

Egorov, Evgeny N., Nikolay I. Kol'tsov e Nikolay F. Ushmarin. "TECHNOLOGICAL ADDITIVES FOR OIL AND PETROL RESISTANCE RUBBERS BASED ON BUTADIENE-NITRILE CAOUTCHOUCS". IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 64, n. 6 (15 maggio 2021): 41–46. http://dx.doi.org/10.6060/ivkkt.20216406.6169.

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The article investigated the influence of various technological additives (zincolet BB 222, lubstab-01 and MA-L22) on the technological properties of the rubber mixture, physical, mechanical and operational characteristics of rubber based on nitrile butadiene caoutchouc BNKS-40AMN. Basic rubber mixture studied included caoutchouc, BC-FF percadox, zinc monomethacrylate, maleide F, triallyl isocyanurate, acetonanil N, MGF-9 and THM-3 oligoester acrylates, carbon black P 514 and other ingredients. The rubber mixture was prepared on laboratory rolls LB 320 160/160 in two stages. At the first stage, BNKS-40AMN caoutchouc was mixed with ingredients and processing aids. As technological additives, zincolet BB 222, lubstab-01 and MA-L22 were used. In the second mixing step, BC-FF percadox and vulcanization coagents were introduced. For the obtained variants of the rubber mixture the vulcanization characteristics were studied on an MDR 3000 Basic rheometer at a temperature of 170 °C. The rubber mixture prepared was vulcanized in a P-V-100-3RT-2-PCD type vulcanizing press at 150 °C for 40 min. Determination of elastic-strength and operational properties of rubber were carried out according to the standards existing for the rubber industry. The oil resistance of the vulcanizates was evaluated by changing their elastic strength after exposure to standard liquid SZHR-1 at a temperature of 125 °C, as well as by changing the mass of the samples after exposure to a mixture of isooctane with toluene at room temperature. It was found that the introduction of technological additives in the rubber compound improves the distribution of carbon black P 514 and powdered ingredients (zinc monomethacrylate, maleide F, triallyl isocyanurate, acetonanil H) in the caoutchouc matrix. Increased elastic strength indicators and their smallest changes after exposure to aggressive hydrocarbon media is characterized a rubber containing technological additive MA-L22. A comparison of technological, elastic-strength properties and resistance to aggressive media for rubbers containing butadiene-nitrile caoutchoucs BNKS-18AMN, BNKS-28AMN and BNKS-40AMN with optimal technological additives for them was done. It has been established that rubber containing BNKS-40AMN and technological additive MA-L22 is characterized by improved vulcanization properties, increased elastic strength indicators and their smallest changes after exposure to aggressive hydrocarbon media.

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32

Kumar, Vineet, Anuj Kumar, Minseok Song, Dong-Joo Lee, Sung-Soo Han e Sang-Shin Park. "Properties of Silicone Rubber-Based Composites Reinforced with Few-Layer Graphene and Iron Oxide or Titanium Dioxide". Polymers 13, n. 10 (12 maggio 2021): 1550. http://dx.doi.org/10.3390/polym13101550.

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The increasing demand for polymer composites with novel or improved properties requires novel fillers. To meet the challenges posed, nanofillers such as graphene, carbon nanotubes, and titanium dioxide (TiO2) have been used. In the present work, few-layer graphene (FLG) and iron oxide (Fe3O4) or TiO2 were used as fillers in a room-temperature-vulcanized (RTV) silicone rubber (SR) matrix. Composites were prepared by mixing RTV-SR with nanofillers and then kept for vulcanization at room temperature for 24 h. The RTV-SR composites obtained were characterized with respect to their mechanical, actuation, and magnetic properties. Fourier-transform infrared spectroscopy (FTIR) analysis was performed to investigate the composite raw materials and finished composites, and X-ray photoelectron spectroscopy (XPS) analysis was used to study composite surface elemental compositions. Results showed that mechanical properties were improved by adding fillers, and actuation displacements were dependent on the type of nanofiller used and the applied voltage. Magnetic stress-relaxation also increased with filler amount and stress-relaxation rates decreased when a magnetic field was applied parallel to the deformation axes. Thus, this study showed that the inclusion of iron oxide (Fe3O4) or TiO2 fillers in RTV-SR improves mechanical, actuation, and magnetic properties.

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33

Wang, Yunfei. "Preparation and Study of EPDM Composites with High Volume Resistance Retention Rate". Scientific Journal of Technology 6, n. 3 (21 marzo 2024): 113–22. http://dx.doi.org/10.54691/ze4kqv22.

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LDPE/ EPDM composites were prepared by mechanical blending method. The effects of two compatibilizers MA/Zn and CPE on the vulcanization properties, mechanical properties, aging resistance and electrical properties of the composites were studied. The results showed that the addition of two kinds of compatibility significantly improved the compatibility of LDPE and EPDM. Compared with CPE, the addition of MA/Zn can improve the properties of the composites better. The mechanical and electrical properties of the composite were improved by the addition of MA/Zn compatibilizer. The volume resistivity of sample L3M2 is the highest at room temperature and 125 ℃, which are 19.8×1013Ω·m and 16.8×1012Ω·m, respectively. Compared with L3, the increase was 26.1% and 25.8%, respectively. The tensile strength is 14.1MPa, which is 90.5% higher than L3.

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34

Xu, Huihui, Yanhong Gao, Zihou Liu e Yiling Bei. "Theoretical Investigation of the Hydrolytic Mechanism of α-Functionalized Alkoxysilanes as Effective Crosslinkers and the Difficulty of Deep Vulcanization in RTV Silicone Rubber". Materials 11, n. 9 (24 agosto 2018): 1526. http://dx.doi.org/10.3390/ma11091526.

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The reactions between α-, γ-ethylenediaminemethyl trimethyl-ketoxime silane (α-, γ-EAMOS) and H2O were investigated on the geometries of stationary points, the reaction pathway (IRC), thermodynamic and kinetic analysis by density functional theory (DFT) at the B3LYP/6-311G (d, p) level. Interestingly, the results showed that the hydrolysis activity of α-EAMOS is higher than that of γ-EAMOS, due to the influence of an amino substituent in position α-C on silicon. α-EAMOS can be used as a superior crosslinker for room temperature vulcanized (RTV) silicone rubber to achieve rapid crosslinking without a toxic catalyst. Besides, compared with the reaction between α-EAMOS and H2O, the reactivity between α-EAMOS and hydroxy siloxane (HO–Si(CH3)2–OSiH3) was discussed. Particularly, it revealed that the deep vulcanization of RTV silicone rubber is difficult.

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35

Pazur, Richard J., e T. Mengistu. "INFLUENCE OF THE CROSSLINK STRUCTURE ON THE ACTIVATION ENERGY CALCULATED UNDER THERMO-OXIDATIVE CONDITIONS". Rubber Chemistry and Technology 91, n. 1 (1 gennaio 2018): 205–24. http://dx.doi.org/10.5254/rct-17-83714.

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ABSTRACT A series of six carbon black reinforced brominated poly(isobutylene-co-isoprene) (BIIR) compounds has been developed varying only in cure system type: sulfur, sulfur donor, zinc oxide, peroxide, phenolic resin, and ionic. Compounds were aged from room temperature up to 115 °C, and hardness, mechanical properties, and network chain density were measured. Non-Arrhenius behavior was observed due to data curvature from 70 to 85 °C. The oxidation process was adequately described by assigning low (23–85 °C) and high (85–115 °C) temperature regimes. Heterogeneous aging due to diffusion limited oxygen (DLO) occurred for heat aging above 85 °C, and all measured responses except tensile strength were strongly affected, causing lower activation energies. The activation energy for the high temperature oxidation process is in the range of 107 to 133 kJ/mol in the following ascending order: zinc oxide, ionic, sulfur donor, sulfur, peroxide, and resin. The midpoint of the high temperature activation energies is of the same order as the BIIR and poly(isobutylene) elastomers. The low temperature activation energy is in the range of 55–60 kJ/mol and is likely due to a combination of oxidative chain scission (crosslink density loss) and crosslinking recombination (network building) reactions. Apart from the crosslink structure stability, the presence of unsaturation along the polymer chain after vulcanization affects the high temperature activation energy.

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36

Tepsila, Sujirat, e Amnart Suksri. "A Study on Modification Properties of Silicone Rubber Using Organic Filler from Golden Apple Snail Shell". Key Engineering Materials 718 (novembre 2016): 40–44. http://dx.doi.org/10.4028/www.scientific.net/kem.718.40.

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Silicone rubber room temperature vulcanization (RTV) is widely used as an insulator. This paper aims to improve the electrical and mechanical properties of RTV with organic filler from golden apple snail shells. The processed golden apple snail shells have the particle size of 75 μm. Specimen were made from silicone rubber with an addition of organic filler and inorganic filler for tested under ASTM D638-2a standard. The filler ratio was varying from 0 to 50% by weight with incremental of 5%. Experimental results showed that, there were good agreement in threshold of electrical and mechanical properties. RTV with the organic filler ratio of 40% out performed the inorganic filler in electrical aspect. Tensile strength of RTV was found to be increased when 5% addition of organic filler is used and decreases steadily as this filler is increased. The amount of filler has greater contribution to the hardness property of the RTV and it may become brittle when it is used in excessive amount.

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37

Al-Kadi, Faten K., Jwan F. Abdulkareem e Bruska A. Azhdar. "Hybrid Chitosan–TiO2 Nanocomposite Impregnated in Type A-2186 Maxillofacial Silicone Subjected to Different Accelerated Aging Conditions: An Evaluation of Color Stability". Nanomaterials 13, n. 16 (20 agosto 2023): 2379. http://dx.doi.org/10.3390/nano13162379.

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This study explores the impact of the incorporation of a chitosan–TiO2 nanocomposite on the color stability of pigmented room-temperature vulcanization maxillofacial silicone under various accelerated aging conditions. Five hundred disk-shaped specimens were formed with type A-2186 silicone elastomer, and they were distributed into groups based on pigment types and nanoparticle treatments. The color difference (ΔE) was assessed using a colorimeter in the CIELAB color system before and after exposure to aging conditions, including UV-accelerated aging and outdoor weathering. ANOVA, Dennett’s T3, and Tukey HSD tests revealed significant color alterations across all silicone types, with the most pronounced being in the red-colored 3% chitosan specimens and the least pronounced being in the 2% TiO2 specimens that underwent UV-accelerated aging. Outdoor weathering consistently increased the ΔE values across all categories. This study suggests that while nanoparticles may offer some resistance against accelerated aging, they fall short in adequately defending against UV radiation during outdoor weathering.

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38

Abbasi, Amin, Wan Zaireen Nisa Yahya, Mohamed Mahmoud Nasef, Muhammad Moniruzzaman e Ali Shaan Manzoor Ghumman. "Copolymerization of palm oil with sulfur using inverse vulcanization to boost the palm oil industry". Polymers and Polymer Composites 29, n. 9_suppl (novembre 2021): S1446—S1456. http://dx.doi.org/10.1177/09673911211054269.

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Nowadays, most of the world’s palm oil is being produced in Malaysia and Indonesia; however, the demand for this vegetable oil as an edible oil is declining in many countries since consuming palm oil in excess can result in serious health problems. Consequently, finding new applications such as the production of bio-based polymers to make use of this cheap and abundant vegetable oil seems necessary. Herein, we report the copolymerization of palm oil with sulfur with different feed ratios via inverse vulcanization. The copolymers are then characterized using Fourier-transform infrared spectroscopy, differential scanning calorimetry and X-ray diffraction analysis. The results confirmed the formation of the polymers and their stability against depolymerization. Altogether, the obtained sulfur-palm oil copolymers showed great properties such as thermal stability up to 230°C under a nitrogen atmosphere and rubbery properties at room temperature. Although the Thermogravimetric analysis (TGA) thermograms had previously confirmed the high conversion of elemental sulfur into the polymeric structure by comparing the initial sulfur content and the final polysulfide content in the polymer, some unreacted elemental sulfur was also observed in the final product. Sulfur-palm oil (S-Palm oil) is a new green polymer that helps to find a new use for palm oil as a big industry as well as sulfur which is underutilized and left in stockpile as a byproduct in gas and petroleum refineries.

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39

dos Santos, Danielle Ferreira, e Renata Antoun Simão. "Study of the Impact of Ionic Liquid on the Reactive Compatibilization of the NBR/EVASH/PP Vulcanized Thermoplatic Elastomer Using the Click Chemistry Technique by Thiol-Ene". Applied Mechanics and Materials 909 (28 settembre 2022): 1–9. http://dx.doi.org/10.4028/p-109457.

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Abstract (sommario):

The dynamic vulcanization technique is a process of crosslinking an elastomer during mixing with a molten state thermoplastic, resulting in a new class of thermoplastic elastomers (TPEs): vulcanized thermoplastics (TPVs). This technique obtains materials with rubber behavior at room temperature, but processed as plastics at high temperatures, especially by extrusion and injection. The advantage of using the process of obtaining thermoplastic elastomers is that traditional elastomers require several steps in their processing. From an environmental point of view, vulcanized thermoplastics are interesting, since these materials keep their properties practically unchanged with direct recycling, without the need for any treatments. The objective of this work was to develop a new system of reactive compatibilization for the PP/NBR mixture, by means of the click chemistry technique by the reaction of the thiol-ene type, using as a compatibilizing agent the addition of EVASH (Poli (ethylene-co-alcoholicvinyl)-co-mercapto-vinyl acetate), resulting from the chemical modification of EVA (poly (acrylonitrile-co-butadiene)) with mercaptan groups by transesterification. The ionic liquid acted as a catalyst, optimizing the transesterification reaction of EVA, to obtain EVASH with a greater presence of -SH to EVA, obtaining more rigid systems due to the click thiol-ene bond.

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Yang, K., e C. L. Gu. "Research on novel shape memory alloy multi-fingered humanoid hand". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 221, n. 9 (1 settembre 2007): 1131–40. http://dx.doi.org/10.1243/09544062jmes527.

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Two new type actuators named planar bending embedded shape memory alloy actuator (ESMAA) and spacial bending ESMAA were presented. Using shape memory effect of SMA wires and elasticity of room temperature vulcanization silicone rubber, the ESMAAs could output force and bend displacement steadily. Furthermore, a novel three-fingered humanoid robot hand consisting of six ESMAAs was developed first. The structural parameters of the actuators, such as rod's radius, wire's radius, wire's recoverable curvature, and offset distance were optimized by combining analytical model with experimental results. On the basis of bionics, the lengths of hand's knuckles were determined through statistical research on the configuration of human beings' hands. The locations of fingers were carefully chosen through a volume optimal index. It is shown in the experiments that maximum angle between ends' tangents of each finger are 68.5°, 79°, and 79°, respectively. The tip of each finger could reach its final position approximately at the same time and by controlling the bending of each finger, the hand could accomplish fine manipulation like that of a human being.

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Sandesh, Bhaktha, Hegde Sriharsha, U. Rao Sathish e Gandhi Nikhil. "Investigation of tensile properties of RTV Silicone based Isotropic Magnetorheological Elastomers." MATEC Web of Conferences 144 (2018): 02015. http://dx.doi.org/10.1051/matecconf/201814402015.

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Magnetorheological elastomer (MRE) consists of an elastomer matrix and a Ferro-magnetic ingredient. The mechanical properties of MR elastomers can be reversibly controlled by applying a magnetic field of suitable intensity. The current work focusses on the enhancement of tensile property of RTV (Room Temperature Vulcanization) silicone based elastomer. The influence of Carbonyl iron powder (CIP) content and magnetic field were experimentally investigated. Addition of CIP increases the tensile modulus but it reduces the percentage elongation and tensile strength making it brittle. Under the influence of magnetic field, the enhancement of tensile properties up to 20% content was linear. The behavior above 20% is observed to be non-linear. The onset of non-linear stress-strain behavior is investigated. Regression equation is developed from the experimental data relating percentage content with the mechanical properties of MRE. The developed equation predicted the behavior of 27% MRE with an error of less than 8%. Hyperelastic model developed by Yeoh was fitted to the stress-strain behavior of MRE with minimal error.

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42

Zhou, Xinxin, Lesi Cai, Weiwei Lei, He Qiao, Chaohao Liu, Xiuying Zhao, Jianfeng Chen, Runguo Wang e Liqun Zhang. "Preparation and intermolecular interaction of bio-based elastomer/hindered phenol hybrid with tunable damping properties". Pure and Applied Chemistry 87, n. 8 (1 agosto 2015): 767–77. http://dx.doi.org/10.1515/pac-2014-1207.

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AbstractIn this research, crosslinked hybrids of a newly invented bio-based elastomer poly(di-isoamyl itaconate-co-isoprene) (PDII) and 3,9-bis[1,1-dimethyl-2{β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]-2,4,8,10-tetraoxaspiro[5,5]-undecane (AO-80) were designed and prepared by the mechanical kneading of the PDII/AO-80 hybrids at a temperature higher than the melting point of AO-80, followed by the crosslinking of PDII during the subsequent hot-pressing/vulcanization process. The microstructure, morphology, and mechanical properties of the hybrids were systematically investigated in each preparation stage by using DSC, FTIR, XRD, SEM, DMTA, and tensile testing. Part of the AO-80 molecules formed an AO-80-rich phase, but most of them dissolved in the PDII to form a very fine dispersion in amorphous form. The results of FTIR and DSC indicated that strong intermolecular interactions were formed between the PDII and the AO-80 molecules. Each PDII/AO-80 crosslinked hybrid showed a single transition with a higher glass transition temperature and significantly higher loss value (tan δ) than the neat PDII because of intermolecular interactions between the PDII and the AO-80 molecules. For instance, tan δ of PDII/AO-80 consisting of 100 phr AO-80 achieved 2.6 times as neat PDII. The PDII/AO-80 crosslinked hybrids with applicability at room temperature are potential bio-based damping materials for the future.

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Liang, Weijie, Xin Ge, Jianfang Ge, Tiehu Li, Tingkai Zhao, Xunjun Chen, Yaozhen Song et al. "Reduced Graphene Oxide Embedded with MQ Silicone Resin Nano-Aggregates for Silicone Rubber Composites with Enhanced Thermal Conductivity and Mechanical Performance". Polymers 10, n. 11 (12 novembre 2018): 1254. http://dx.doi.org/10.3390/polym10111254.

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Abstract (sommario):

With developments of the electronics industry, more components are being included in electronic devices, which has led to challenges in thermal management. Using reduced graphene oxide embedded with MQ silicone resin (RGO/MQ) nano-aggregates as the composite filler and silicone rubber (SR) as the matrix, a simple approach is designed to prepare RGO/MQ/SR composites. Reduced graphene oxide (RGO) was first used as a substrate for the growth of MQ silicone resin by hybridization, forming sandwich-like micro structured RGO/MQ nano-aggregates successfully. Then, RGO/MQ was integrated into α,ω-dihydroxylpolydimethylsiloxane based on the in situ solvent-free blending method, followed by condensation and vulcanization, fabricating the final RGO/MQ/SR composites. The effective strategy could enhance the adaptability between graphene and silicone matrix under external stimuli at room temperature by embedding nanoscale MQ into the interface of graphene/silicone as the buffer layer. Obvious improvements were found in both thermal conductivity and mechanical properties due to excellent dispersion and interfacial compatibility of RGO/MQ in the host materials. These attractive results suggest that this RGO/MQ/SR composite has potential as a thermal interface material for heat dissipation applications.

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44

Du, Dajiang, Teruo Asaoka, Makoto Shinohara, Tomonori Kageyama, Takashi Ushida e Katsuko Sakai Furukawa. "Microstereolithography-Based Fabrication of Anatomically Shaped Beta-Tricalcium Phosphate Scaffolds for Bone Tissue Engineering". BioMed Research International 2015 (2015): 1–9. http://dx.doi.org/10.1155/2015/859456.

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Abstract (sommario):

Porous ceramic scaffolds with shapes matching the bone defects may result in more efficient grafting and healing than the ones with simple geometries. Using computer-assisted microstereolithography (MSTL), we have developed a novel gelcasting indirect MSTL technology and successfully fabricated two scaffolds according to CT images of rabbit femur. Negative resin molds with outer 3D dimensions conforming to the femur and an internal structure consisting of stacked meshes with uniform interconnecting struts, 0.5 mm in diameter, were fabricated by MSTL. The second mold type was designed for cortical bone formation. A ceramic slurry of beta-tricalcium phosphate (β-TCP) with room temperature vulcanization (RTV) silicone as binder was cast into the molds. After the RTV silicone was completely cured, the composite was sintered at 1500°C for 5 h. Both gross anatomical shape and the interpenetrating internal network were preserved after sintering. Even cortical structure could be introduced into the customized scaffolds, which resulted in enhanced strength. Biocompatibility was confirmed by vital staining of rabbit bone marrow mesenchymal stromal cells cultured on the customized scaffolds for 5 days. This fabrication method could be useful for constructing bone substitutes specifically designed according to local anatomical defects.

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45

Bahruddin, Zuchra Helwani, Lili Saktiani, Yanuar e Rahmat Satoto. "Study on Utilization of Palm Oil Fly Ash as a Filler for Thermoset Natural Rubber". Advanced Materials Research 844 (novembre 2013): 280–84. http://dx.doi.org/10.4028/www.scientific.net/amr.844.280.

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Palm oil fly ash (POFA) as solid waste produced from crude palm oil industries consist of quite high of silica (more than 50% w/w). This study aimed to compare the properties and morphology of thermoset natural rubber (TNR) with POFA, silica, carbon black (CB), and mixture of POFA-CB fillers. The filler content used is 30 phr (per hundred rubbers). The process of making the compound was conducted by using a roll mill at room temperature and a maximum roll rotational speed of 20 rpm. Zinc oxide 5 phr, stearic acid 2 phr, mercaptodibenzothiazyldisulfide (MBTS) 0.6 phr, and Sulfur of 3 phr were used as curative agents. Trimethylquinone (TMQ) 1 phr was used as an antioxidant. Commercial minarex 2.5 phr was used as a plasticizer. Vulcanization process was carried out at a temperature of 150 °C and a pressure of 50 kg/cm2 using a hot press. Morphology was observed using a scanning electron microscope (SEM). Measurement of tensile properties was carried out using universal testing machine (UTM) according to ASTM D412-06a standard. The results indicated that the use of POFA as a filler could potentially produce TNR with quite good morphology, tensile properties and water absorption properties. A mixture of POFA-CB with a mass ratio of 50/50 (w/w) produced the thermoset with the value of 18.5 MPa of tensile strength, 1600% of elongation at break, and 1.2 MPa of elastic modulus.

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Harahap, Hamidah, Adrian Hartanto, Kelvin Hadinatan, Indra Surya e Baharin Azahari. "Effect of Aging on Mechanical Properties of Natural Rubber Latex Products Filled with Alkanolamide-Modified Cassava Peel Waste Powder (CPWP)". Advanced Materials Research 1123 (agosto 2015): 387–90. http://dx.doi.org/10.4028/www.scientific.net/amr.1123.387.

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The effect of aging on mechanical properties of natural rubber latex (NRL) products filled with alkanolamide-modified cassava peel waste powder (CPWP) was studied. CPWP used as fillers was prepared by milling and sieving it until the size of 100 mesh. The powder then was dispersed in a suspension containing water and alkanolamide in order to modify the prepared powders. The dispersion system of 10 pphr (part per hundred rubber) then was added into NRL matrix followed by pre-vulcanization at 70°C for 10 minutes. The NRL compound then were casted into films by coagulant dipping method then dried at 120°C for 10 minutes. Afterwards, the films were allowed to cool at room temperature for 24 hours before being aged in a circulation of hot air for 24 hours at 70°C. The properties such as tensile strength, tensile modulus, and elongation at break were evaluated between the aged samples and the unaged samples. From this study, it showed that the aged films have increasing value of tensile strength and tensile modulus while the value of elongation at break decreases. These datas are supported by Scanning Electron Microscope (SEM) micrographs which indicate that the change of morphology in NRL films occurs before and after aging.

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Zhao, Shi Huai, Wen Wen Xu, Xiao Ming Zhao e Zi Bo Yang. "Preparation and Capacitance Properties of Nickel-Cobalt Sulfide/Graphene Composites". Materials Science Forum 956 (giugno 2019): 35–45. http://dx.doi.org/10.4028/www.scientific.net/msf.956.35.

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Abstract (sommario):

In order to explore the supercapacitor electrode material with high energy density, a composite material that nickel-cobalt sulfide loaded in graphene (NiCo2S4@rGO) with core-shell structure was successfully prepared by hydrothermal, room temperature vulcanization and annealing. The core-shell structure of the material greatly increased the contact area between the material and the electrolyte and improved the electrochemical performance. In addition, the energy density has been significantly improved. NiCo2S4@rGO was characterized by field emission scanning electron microscopy (SEM), high-resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectrometer. The electrochemical properties of the material were evaluated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). The results show that the capacitance can reach 1100 F/g at the current density of 0.5 A/g. Furthermore, the NiCo2S4@rGO as positive electrode and reduced graphene oxide (rGO) as negative electrode were assembled into an asymmetric supercapacitor (ASC). The device exhibits a high energy density of 74.78 Wh/Kg at a power density of 400 W/Kg, as well as excellent cycling stability of 88.9% after 3 000 cycles, which reflects the excellent electrochemical performance of the material.

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48

Al-Kadi, Faten K., Jwan Fateh Adbulkareem e Bruska A. Azhdar. "Evaluation of the Mechanical and Physical Properties of Maxillofacial Silicone Type A-2186 Impregnated with a Hybrid Chitosan–TiO2 Nanocomposite Subjected to Different Accelerated Aging Conditions". Biomimetics 8, n. 7 (11 novembre 2023): 539. http://dx.doi.org/10.3390/biomimetics8070539.

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Abstract (sommario):

The effects of incorporating a pioneer chitosan–TiO2 nanocomposite on the mechanical and physical properties of room-temperature vulcanization (RTV) maxillofacial A-2186 silicone under accelerated aging protocols were rigorously examined. This investigation utilized 450 samples distributed across five distinct silicone classifications and assessed their attributes, such as tensile strength, elongation, tear strength, hardness, and surface roughness, before and after various accelerated aging processes. Statistical methodologies, including a one-way ANOVA, Tukey’s HSD, and Dunnett’s T3, were employed based on the homogeneity of variance, and several key results were obtained. Silicones infused with 1 wt.% chitosan–TiO2 showed enhanced tensile strength across various aging procedures. Moreover, the 1 wt.% TiO2/Chitosan noncombination (TC) and 2 wt.% TiO2 compositions exhibited pronounced improvements in the elongation percentage. A consistent rise was evident across all silicone categories regarding tear strength, with the 1 wt.% chitosan–TiO2 variant being prominent under certain conditions. Variations in hardness were observed, with the 1 wt.% TC and 3 wt.% chitosan samples showing distinctive responses to certain conditions. Although most samples displayed a decreased surface roughness upon aging, the 1 wt.% chitosan–TiO2 variant frequently countered this trend. This investigation provides insights into the potential of the chitosan–TiO2 nanocomposite to influence silicone properties under aging conditions.

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Toki, Shigeyuki, Igors Sics, Shaofeng Ran, Lizhi Liu, Benjamin S. Hsiao, Syozo Murakami, Masatoshi Tosaka et al. "Strain-Induced Molecular Orientation and Crystallization in Natural and Synthetic Rubbers under Uniaxial Deformation by In-situ Synchrotron X-ray Study". Rubber Chemistry and Technology 77, n. 2 (1 maggio 2004): 317–35. http://dx.doi.org/10.5254/1.3547826.

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Abstract In-situ synchrotron wide-angle X-ray diffraction (WAXD) studies and simultaneous measurements of stress and strain during uniaxial stretching of various vulcanized rubbers were carried out (at room temperature and 0°C) to reveal the strain-induced molecular orientation and crystallization relationships. Rubbers evaluated included natural rubber (NR), synthetic poly-isoprene rubber (IR), poly-cis-1,4-butadiene rubber (BR) and butyl rubber (IIR). Some universal features were observed in these systems: (i) At high strains (> 5.0), the majority of the chains (up to 50 ≈ 75%) in natural and synthetic rubbers remained in the un-oriented amorphous state with only a small amount of crystalline fraction formed (10–20%). The rest of the chains were in the oriented amorphous state. (ii) During deformation, the oriented amorphous chains acted as precursors to strain-induced crystallization. A network of micro-fibrillar crystallites is formed within the closely populated vulcanization points, leading to the enhancement of mechanical properties at high strains. Different rubbers exhibited different behaviors during strain-induced crystallization. For example, poly-isoprenes (NR and IR vulcanized with sulfur and peroxide) showed strain-induced crystallization at a low strain of 2.5, resulting in larger crystalline but smaller oriented amorphous fractions. In contrast, BR and IIR crystallized at a higher strain of 4.0 lead to higher molecular orientation, higher oriented amorphous, but smaller crystalline fractions. The relationship between the molecular orientation and crystallization in strained rubber depends on the intrinsic crystallizability of the chains and the topology of the crosslinked network.

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Silva, Rubens Signoretti Oliveira, Fernanda Faria Rocha, José Alcides Almeida de Arruda, Isadora França Vieira da Silva, Cláudia Lopes Brilhante Bhering, Vagner Rodrigues Santos e Amália Moreno. "Effects of Brazilian green propolis glycolic solutions against bacterial biofilm on elastomers used in maxillofacial prostheses". Research, Society and Development 11, n. 3 (1 marzo 2022): e40111326739. http://dx.doi.org/10.33448/rsd-v11i3.26739.

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Maxillofacial prostheses are among the modalities of prosthetic rehabilitation but the disinfectant solutions for their cleaning have been barely explored. The purpose of the present study was to evaluate the antibacterial effects of a Brazilian green propolis glycolic (PGL) solution on the removal of biofilm from the surface of two maxillofacial elastomers (room temperature vulcanization [RTV] and high consistency silicone rubber [HCR]). A total of 42 specimens (3×10 mm) were made with these two elastomers and Staphylococcus aureus was allowed to grow for 24 hours on the surface of the biomaterials. Specimens (n=3) were randomly allocated to the following treatment groups by immersion for 15 minutes: 0.9% saline solution; 2% chlorhexidine gluconate (CHX); 11%, 16% and 20% PGL; and Daro Brand® antimicrobial liquid agent and antibacterial gel soap. Quantitative assessment was performed by counting the number of colony-forming units (CFU). Two-way ANOVA was employed for data analysis. Specimens of both maxillofacial elastomers treated with PGL solutions at concentrations of 11%, 16% and 20%, as well as 2% CHX, did not reveal CFU/mL of the S. aureus strain, indicating the broad spectrum of antibiofilm action of these disinfectant solutions. In addition, the Daro Brand® antimicrobial liquid agent showed lower CFU/mL in both maxillofacial elastomers compared to the Daro Brand® gel soap and 0.9% saline solution. Therefore, disinfection with PGL solutions is effective and might be considered to be a promising alternative in eliminating the S. aureus biofilm from specimens of maxillofacial elastomers by immersion for 15 minutes.

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