Relevant bibliographies by topics / Long chain branching

Academic literature on the topic 'Long chain branching'

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Published: 4 June 2021
Last updated: 3 February 2022

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Journal articles on the topic "Long chain branching"

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Mcleish, T. C. B. "Long Chain Branching." Chemical Engineering Research and Design 78, no. 1 (January 2000): 12–32. http://dx.doi.org/10.1205/026387600527031.

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Janzen, J., and R. H. Colby. "Diagnosing long-chain branching in polyethylenes." Journal of Molecular Structure 485-486 (August 1999): 569–83. http://dx.doi.org/10.1016/s0022-2860(99)00097-6.

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Shiga, S. "Modern Characterization of Long-Chain Branching." Polymer-Plastics Technology and Engineering 28, no. 1 (February 1989): 17–41. http://dx.doi.org/10.1080/03602558908048583.

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Cangussú, Manoela E., Ana P. de Azeredo, Adriane G. Simanke, and Benjamin Monrabal. "Characterizing Long Chain Branching in Polypropylene." Macromolecular Symposia 377, no. 1 (February 2018): 1700021. http://dx.doi.org/10.1002/masy.201700021.

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Ghielmi, Alessandro, Stefano Fiorentino, Giuseppe Storti, Marco Mazzotti, and Massimo Morbidelli. "Long chain branching in emulsion polymerization." Journal of Polymer Science Part A: Polymer Chemistry 35, no. 5 (April 15, 1997): 827–58. http://dx.doi.org/10.1002/(sici)1099-0518(19970415)35:5<827::aid-pola1>3.0.co;2-i.

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Yu, Youlu, Paul J. DesLauriers, and David C. Rohlfing. "SEC-MALS method for the determination of long-chain branching and long-chain branching distribution in polyethylene." Polymer 46, no. 14 (June 2005): 5165–82. http://dx.doi.org/10.1016/j.polymer.2005.04.036.

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Liu, Jianye, Lijuan Lou, Wei Yu, Ruogu Liao, Runming Li, and Chixing Zhou. "Long chain branching polylactide: Structures and properties." Polymer 51, no. 22 (October 2010): 5186–97. http://dx.doi.org/10.1016/j.polymer.2010.09.002.

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Liu, Jianye, Shijun Zhang, Liying Zhang, and Yiqing Bai. "Crystallization Behavior of Long-Chain Branching Polylactide." Industrial & Engineering Chemistry Research 51, no. 42 (October 11, 2012): 13670–79. http://dx.doi.org/10.1021/ie301567n.

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Warakomski, John M., and Bruce P. Thill. "Evidence for long chain branching in polyethyloxazoline." Journal of Polymer Science Part A: Polymer Chemistry 28, no. 13 (December 1990): 3551–63. http://dx.doi.org/10.1002/pola.1990.080281303.

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Small, K. W., F. Yearsley, and J. C. Greaves. "Long chain branching in poly(vinyl chloride)." Journal of Polymer Science Part C: Polymer Symposia 33, no. 1 (March 8, 2007): 201–9. http://dx.doi.org/10.1002/polc.5070330120.

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Dissertations / Theses on the topic "Long chain branching"

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Thomas, Sydney. "Measurement and modelling of long chain branching in chain growth polymerization." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0001/NQ42769.pdf.

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Beigzadeh, Daryoosh. "Long-chain branching in ethylene polymerization using combined metallocene catalyst systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0020/NQ52024.pdf.

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Gragert, Maria Magdalena. "Catalyst design for ethylene polymerisation : a study on long-chain branching." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/44956.

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Polyethylene (PE) is the most produced polyolefin worldwide. Since recently discovered long-chain branches (LCB) have been shown to improve the processability, this thesis concentrates on the synthesis of new catalysts capable of producing long-chain branched polyethylene (LCB PE), the investigation of the mechanism which leads to LCB, and the control of the branching degree. The synthesis of new Group IV metal complexes with aromatic carbon-donor ligands which are η1-bound to the metal centre is described. These ligands include biphenyls, diphenylpyridines and terphenyls. Furthermore, an amido complex has been prepared and its synthesis and characterisation is presented herein. All complexes with carbon-based ligands are highly sensitive to air and moisture. Only the use of metal precursors with electron donating ligands enabled the formation of such complexes and it is concluded that electron donating ligands stabilise the electron deficient metal centre and metal-carbon bond. Polymerisation studies showed that the new complexes are active ethylene polymerisation catalysts. Their activity usually increases with temperature. The effect of hydrogen on the polymerisation activity cannot be predicted. Sensitive rheology measurements of the polymer melts revealed the presence of long-chain branches and it has been shown that the Group IV metal complexes with carbon-based ligands described in this thesis are producing LCB PE. Initial experiments towards the investigation of the long-chain branch forming mechanism are described within this thesis. Although not finished, a suitable route to complexes bearing a long alkyl chain has been established, which can be pursued in further studies. A series of tertiary-alkyl amines has been prepared and reacted with a silane to give the targeted aminosilane ligand. The effect of alkyl chain substituents on a cyclopentadienyl ligand in metallocenes has additionally been investigated with respect to the formation of LCB. In order to control the number of LCB in a PE resin, a bicatalytic system involving a bis(imino)pyridineiron catalyst that produces linear PE, an α-diiminenickel catalyst that produces branched PE and a chain transfer agent (CTA) was investigated. The combination of chain shuttling and chain walking as common mechanisms involved in ethylene polymerisation with late transition metal complexes showed to be a promising approach for the control of branching in PE while using ethylene as only monomer feed. Not only can branching be induced by carefully selecting the catalyst ratio and amount of CTA, but it has been shown that chain straightening occurs.
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Parmar, Harisinh, and h_arzoo@yahoo com. "Rheology Of Peroxide Modified Recycled High Density Polyethylene." RMIT University. Civil, Environmental and Chemical Engineering, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080724.164249.

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Consumption of plastics has increased exponentially, in line with the world's population. Not surprisingly this is reflected in enormous growth of the plastic industry especially during the last five decades. Commensurate with this, waste produced from plastics consumption has created a major environmental problem. Many types of waste disposal methods have been used all over the world so far, but all of them have disadvantages. Furthermore, some methods are responsible for the generation of green house gases and further contribution to global warming. Recently, reduction of green house gas emission has become a target of most industries. Plastic recycling and reuse breaks the cycle of endless production of virgin polymer and thus contributes to a net reduction of green house gas emission. Recycling of plastics should produce materials with improved properties to replace virgin plastics for a variety of applications. Improvement in the properties of recycled plastics can be achieved by blending with other plastics, by filler addition and by modification using free radical initiators. Introduction of the free radical initiator (organic peroxide) during reprocessing of the recycled plastics has been found to offer significant property improvements to the recycled materials. Extremely small amounts of a free radical initiator (typically ranging between 0.01 wt% to 0.2 wt%) is capable of enhancing the properties of the recycled plastics to a great extent. This project investigates the use of free radical initiators in the recycling of post consumer recycled high density polyethylene using reactive extrusion. Both molecular and rheological characterisation of recycled and reprocessed materials was carried out and this was followed by tensile testing of the modified materials to satisfy end use applications such as packaging and drainage piping. Post consumer recycled high density polyethylene (R-HDPE) resin and virgin high density polyethylene (V-HDPE) were reactively extruded with low concentrations of dicumyl peroxide (DCP) and 1, 3 1, 4 Bis (tert- butylperoxyisopropyl) Benzene (OP2) respectively in a twin screw extruder in order to produce modified materials with varying composition (0.0 wt%, 0.02 wt%, 0.05 wt%, 0.07 wt%, 0.10 wt% and 0.15 wt%) of both organic peroxides. Morphological characterisation using modulated differential scanning calorimetry (MDSC) demonstrated that there is a decrease in the crystallinity level for all the modified samples. Shear rheological tests were carried out to study the structure of the modified materials within the linear viscoelastic region. Viscoelastic parameters, such as storage modulus (G'), loss modulus (G
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Kulkarni, Amit S. "Nature of Branching in Disordered Materials." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1190655419.

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Wood-Adams, Paula. "The effect of long chain branching on the rheological behavior of polyethylenes synthesized using constrained geometry and metallocene catalysts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0027/NQ50282.pdf.

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Majumder, Khokan Kanti, and khokankanti@yahoo com. "Blown Film Extrusion: Experimental, Modelling and Numerical Study." RMIT University. Civil, Environmental and Chemical Engineering, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080509.161859.

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Abstract This thesis correlates rheological data into a non-linear blown film model that describes the stress and cooling-induced morphological transformations in the axial and flow profiles of the blown films. This will help to improve the physical and mechanical properties of the films in a cost effective way, which will in turn be of great benefit to the food and packaging industries. In this research, experimental and numerical studies of a blown film extrusion were carried out using two different low-density polyethylenes (LDPEs). In the experiment, the key parameters measured and analysed were molecular, rheological and crystalline properties of the LDPEs. In the numerical study, blown film simulation was carried out to determine the bubble characteristics and freeze line height (FLH). A new rheological constitutive equation was developed by combining the Hookean model with the well known Phan-Thien and Tanner (PTT) model to permit a more accurate viscoelastic behaviour of the material. For experimental verification of the simulation results, resins were processed in a blown film extrusion pilot plant using identical die temperatures and cooling rates as used in the simulation study. Molecular characteristics of both LDPEs were compared in terms of their processing benefit in the film blowing process. Based on the experimental investigation, it was found that molecular weight and its distribution, degree of long chain branching and cooling rate play an important role on melt rheology, molecular orientation, blown film processability, film crystallinity and film properties. Effect of short chain branching was found insignificant for both LDPEs. Statistical analysis was carried out using MINITAB-14 software with a confidence level of 95% to determine the effect of process variables (such as die temperature and cooling rate) on the film properties. Film properties of the LDPEs were found to vary with their molecular properties and the process variables used. Blown film model performance based on the newly established PTT-Hookean model was compared with that based on the Kelvin model. Justification of the use of PTT-Hookean model is also reported here using two different material properties. From the simulation study, it has been found that predictions of the blown film characteristics conformed very well to the experimental data of this research and previous studies using different materials and different die geometries. Long chain branching has been found as the most prominent molecular parameter for both LDPEs affecting melt rheology and hence the processability. Die temperature and cooling rate have been observed to provide similar effect on the tear strength and shrinkage properties of blown film for both LDPEs. In comparison to the Kelvin model, the PTT-Hookean model is better suited for the modelling of the film blowing process. It has also been demonstrated in this study that the PTT-Hookean model conformed well to the experimental data near the freeze line height and is suitable for materials of lower melt elasticity and relaxation time.
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Ramachandran, Ramnath. "Quantification of Structural Topology in Branched Polymers." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1326828758.

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Giumanca, Radu. "The effects of long chain branching on the rheological properties of polymers." Thesis, 2002. http://hdl.handle.net/2429/12911.

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Long chain branching (LCB) is a very important feature in polymer science due to its influence on the rheological properties of polymers. It has been shown that long chain branching causes strain hardening behavior in the extensional flow of polymer, feature which is not seen in linear species. A great industrial interest has been shown in a method which would detect long chain branching by a simple, yet robust method. Fifteen different samples of polypropylene (PP) of varying molecular weights (MW) and branching structures were studied. The aim was to obtain linear viscoelastic measurements using a Rheometrics System IV rheometer and compare the results to determine the effects of backbone MW, branch MW, and number of branches on the polymers' viscoelastic properties. It was discovered that the samples exhibit drastic thermal degradation, even under inert atmosphere. An antioxidant (Irganox 1010) was found to have no effect. A comparison of linear viscoelastic data yielded questionable results, perhaps suggesting a higher than expected polydispersity. Samples of comb-structure polystyrene were also studied. Linear viscoelastic data was obtained for two different series of PS, differing in MW and branch MW. By comparing with previously obtained data, it was discovered that time (~20 years) has had a small effect for most of the samples. Non-linear measurements were also obtained, and the results for the most part agree with published data. The differences, especially an extended plateau feature previously unpublished, are discussed.
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Zhao, Z. G., Q. Yang, Philip D. Coates, Benjamin R. Whiteside, Adrian L. Kelly, Y. J. Huang, and P. P. Wu. "Structure and Property of Microinjection Molded Poly(lactic acid) with High Degree of Long Chain Branching." 2018. http://hdl.handle.net/10454/16981.

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Yes
Long chain branches (LCB) are successfully grafted to linear poly(lactic acid) (PLA) using functional group reactions with pentaerythritol triacrylate (PETA) and tetraethylthiuram disulfide (TETDS). Results show a high branching degree of PLA (∼49.5%) can be effectively obtained with adding only 1 wt % PETA, contributing remarkably to enhancing strain hardening. The density of the nuclei formed during nonisothermal crystallization for LCB-PLA samples is markedly increased contrasted with PLA, resulting in significantly enhancing crystallinity from 13.3% to 41%, the onset crystallization temperature (∼20 °C), and the crystallization rate. Interestingly, compared with mini-injection molding, the elevated wall shear rates (and corresponding shear stresses) prove to be beneficial to the creation of special crystalline morphologies (β-crystal form) and oriented structures under microinjection molding conditions, resulting in the improvement of tensile strength by ∼45 MPa.
Chinese Scholarship Council
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Book chapters on the topic "Long chain branching"

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Gooch, Jan W. "Long-Chain Branching." In Encyclopedic Dictionary of Polymers, 433. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_7007.

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Mirabella, Francis M., and Leslie Wild. "Determination of Long-Chain Branching Distributions of Polyethylenes." In Advances in Chemistry, 23–44. Washington, DC: American Chemical Society, 1990. http://dx.doi.org/10.1021/ba-1990-0227.ch002.

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"Long-chain branching." In Encyclopedic Dictionary of Polymers, 582. New York, NY: Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-30160-0_6898.

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Striegel, Andre. "Long-Chain Branching Macromolecules." In Encyclopedia of Chromatography, Third Edition (Print Version). CRC Press, 2009. http://dx.doi.org/10.1201/noe1420084597.ch271.

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Striegel, Andr√©. "Long-Chain Branching Macromolecules." In Encyclopedia of Chromatography, Second Edition, 1008–12. CRC Press, 2005. http://dx.doi.org/10.1201/noe0824727857.ch210.

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"Long-Chain Branching of Polymer Resins." In Radiation Processing of Polymer Materials and its Industrial Applications, 248–75. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2011. http://dx.doi.org/10.1002/9781118162798.ch8.

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Striegel, André M. "Long-Chain Branching Macromolecules: Analysis by SEC." In Encyclopedia of Chromatography, 1008–12. CRC Press, 2005. http://dx.doi.org/10.1201/noe0824727857-210.

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Lu, Wei, and Jimmy Mays. "Characterization of long-chain branching in polymers." In Molecular Characterization of Polymers, 281–304. Elsevier, 2021. http://dx.doi.org/10.1016/b978-0-12-819768-4.00005-1.

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Soares, João B. P., and Archie E. Hamielec. "Semicrystalline Polyolefins - Narrow MWD and Long Chain Branching: Best of Both Worlds." In Metallocene Catalyzed Polymers, 103–12. Elsevier, 1998. http://dx.doi.org/10.1016/b978-188420759-4.50013-9.

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Han, Chang Dae. "Tubular Film Blowing." In Rheology and Processing of Polymeric Materials: Volume 2: Polymer Processing. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780195187830.003.0012.

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Tubular film blowing has long been used to produce biaxially oriented films using such thermoplastic polymers as low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP). Here, LDPE refers to a polymer that is synthesized by free-radical polymerization under high pressure (Fawcett et al. 1937). The discovery of linear low-density polyethylene (LLDPE) in the 1980s via the Unipol process (Beret et al. 1986; Jones et al. 1985), which uses a low-pressure gas-phase process, has led to additions to the family of tubular blown films during the past two decades. The discovery of metallocene catalysts (Stevens and Neithamer 1991; Welborn and Ewen 1994) in the 1990s further increased the number of LLDPEs that have been used to produce tubular blown films during the last decade. To distinguish LLDPE from LDPE, LLDPE is sometimes referred to as low-pressure low-density polyethylene (LP-LDPE) and LDPE is referred to as high-pressure low-density polyethylene (HP-LDPE) (see Chapter 6 of Volume 1). In this chapter, however, we use the terminologies LDPE and LLDPE. As described in Chapter 6 of Volume 1, LDPE has a high degree of long-chain branching, while LLDPE has short-chain branching with little or no longchain branching. However, the metallocene catalysts apparently allow one to produce LLDPEs having a wide range of side chains, including a certain degree of long-chain branching. The details of the synthetic procedures for producing such a variety of LLDPEs are closely guarded industrial secrets. Biaxially oriented film can be strong and tough in all directions in the plane of the film. As in fiber spinning, the polymer melt exiting from the die flows under a mechanical tension in the direction of flow. However, in the film blowing process, the tube of molten polymer is extended in both the transverse and the axial (machine) directions. Therefore, rheologically speaking, the film blowing process may be treated from the point of view of biaxial elongational flow, whereas the fiber spinning process may be treated from the point of view of uniaxial elongational flow.
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Conference papers on the topic "Long chain branching"

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Gu, Liangliang, Yuewen Xu, Grant Fahnhorst, and Christopher W. Macosko. "Long chain branching of PLA." In NOVEL TRENDS IN RHEOLOGY VII. Author(s), 2017. http://dx.doi.org/10.1063/1.4982985.

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Karjala, T. P., R. L. Sammler, M. A. Mangnus, L. G. Hazlitt, M. S. Johnson, C. M. Hagen, J. W. L. Huang, et al. "Detection of Low Levels of Long-Chain Branching in Polyolefins." In THE XV INTERNATIONAL CONGRESS ON RHEOLOGY: The Society of Rheology 80th Annual Meeting. AIP, 2008. http://dx.doi.org/10.1063/1.2964685.

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Rolón-Garrido, Víctor H., Jinji Luo, Manfred H. Wagner, and Martin Zatloukal. "Increase of Long-chain Branching by Thermo-oxidative Treatment of LDPE." In NOVEL TRENDS IN RHEOLOGY IV. AIP, 2011. http://dx.doi.org/10.1063/1.3604477.

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Li, Yan, Jin-Cheng Lu, Shao-Long Qiu, Zhen-Hua Chen, Fang-Jun Zhu, Zhen Yao, Changchun Zeng, and Kun Cao. "On the Dynamics of Polypropylene Melt: Long Chain Branching and Physical Cross-links." In 14th Asia Pacific Confederation of Chemical Engineering Congress. Singapore: Research Publishing Services, 2012. http://dx.doi.org/10.3850/978-981-07-1445-1_202.

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Scanu, Lauriane, George W. Roberts, Joseph M. DeSimone, Saad Khan, Albert Co, Gary L. Leal, Ralph H. Colby, and A. Jeffrey Giacomin. "Melt Rheology of Poly Vinilydene Fluoride: Evidence of Long Chain Branching and Microgel Formation." In THE XV INTERNATIONAL CONGRESS ON RHEOLOGY: The Society of Rheology 80th Annual Meeting. AIP, 2008. http://dx.doi.org/10.1063/1.2964691.

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VERROS, G. D. "COMPUTER AIDED ESTIMATION OF MOLECULAR WEIGHT AND LONG CHAIN BRANCHING DISTRIBUTION IN FREE RADICAL POLYMERIZATION." In Proceedings of the International Conference (ICCMSE 2003). WORLD SCIENTIFIC, 2003. http://dx.doi.org/10.1142/9789812704658_0147.

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Okamoto, Kenzo, Masayuki Yamaguchi, Masaoki Takahashi, Albert Co, Gary L. Leal, Ralph H. Colby, and A. Jeffrey Giacomin. "Shear Modification and Elongational Behavior of Two Types of Low-Density Polyethylene Melts with Different Long Chain Branching." In THE XV INTERNATIONAL CONGRESS ON RHEOLOGY: The Society of Rheology 80th Annual Meeting. AIP, 2008. http://dx.doi.org/10.1063/1.2964726.

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Burhin, Henri G. "Characterisation of Long Chain Branching (LCB) in Polyolefins and Elastomers Using Large Amplitude Oscillatory Shear (LAOS) and Fourier Transform Rheology Using Harmonics of the Stress Signal." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32186.

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It is difficult, if not impossible to quantify LCB in polymers using rheological test methods only. Most of the reported rheological methods are affected by polymer characteristics other than LCB (Molecular weight Distribution (MWD), polymer microstructure, polymer type etc…). Poly-Propylene samples having different level of LCB produced by reactive extrusion with Per-Oxi-Dicarbonate have been characterised at strain ratios between 2.5 and 10. Stress signal distortion has been found to be sensitive only to the presence and level of LCB and not to Average Molecular Weight (AMW) and MWD. Quantification of the signal distortion was performed using Fourier transform rheology. As linear visco-elasticity equations are not applicable to LAOS, the approach of Giacomin and Dealy was applied. This considers the stress signal as a Fourier series and enables the calculation of G′n and G″n. LCB has a strong effect on both G′n and G″n, on their ratio and especially on G′ from the first harmonic (G′1). Repeatability data (CV) on G′1 and G″1 shows excellent sensitivity (&lt;1%). The technique has been successfully applied to commercially available elastomers (BR and EPDM) enabling comparisons based on LCB level irrespectively of the AMW and MWD. Rapid graphical differentiation between linear and non linear polymers is achieved with stress/strain rate curves (Lissajou figure). The development of this technique provides polymer suppliers and their customers the ability to rapidly assess variations in Long Chain Branching, essential for incoming material and/or production control.
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Vittorias, Iakovos, Dieter Lilge, Albert Co, Gary L. Leal, Ralph H. Colby, and A. Jeffrey Giacomin. "On the Use of Indexes for Quantifying Long-Chain Branching in Polyethylene: Can We Describe the Rheology of LCB PE and Correlate it to Processing Performance by Using a Single Number?" In THE XV INTERNATIONAL CONGRESS ON RHEOLOGY: The Society of Rheology 80th Annual Meeting. AIP, 2008. http://dx.doi.org/10.1063/1.2964686.

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