Topic
Polyethylene
About: Polyethylene is a research topic. Over the lifetime, 34338 publications have been published within this topic receiving 413090 citations. The topic is also known as: polythene & Polyethylene.
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TL;DR: In this article, the effects of gamma and electron irradiation on virgin and recycled polyethylene were compared and their mechanical, thermal and chemical properties were analyzed, showing that VPE samples showed higher crosslinking percentages than RPE samples in all range of doses studied, unirradiated RPE sample had higher values on their tensile properties than VPE.
1,536 citations
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TL;DR: In this article, the authors discuss the scope of Ziegler catalysis, stereoselectivity, kinetics, and mechanism of homogeneous Natta catalysts; and side reactions in homogeneous catalysts.
Abstract: Publisher Summary This chapter discusses the scope of Ziegler catalysis; stereoselectivity, kinetics, and mechanism of Ziegler catalysis; homogeneous Ziegler–Natta catalysts; and side reactions in homogeneous catalysts. Ziegler catalysis involves rapid polymerization of ethylene and α-ole-fins with the aid of catalysts based on transition-element compounds, normally formed by the reaction of a transition-element halide or alkoxide or alkyl or aryl derivative with a main-group element alkyl or alkyl halide. There are thousands of patents involving every combination of pure or mixed main-group alkyls with transition-element compounds, each claiming advantages. The result of the early work led to the development of “second-generation” Ziegler catalysts. Polymers produced with unmodified Ziegler catalysts showed extremely high molecular weight and broad distribution, and in some cases, there was evidence for “living polymer.” All homogeneous catalyst systems for ethylene polymerization become heterogeneous when polyethylene is formed. On using vanadium-based homogeneous catalysts, polymers consisting of syndiotactic stereo blocks and stereo-irregular blocks are obtained. Very high stereoselectivity is observed for racemic 4-methyl- 1-hexene and racemic 3,7-dimethyl-1-octene, where the asymmetric carbon atom is in the α-position relative to the double bond. Stereoselectivity is caused by the chirality of the catalytically active center, and not by chiral atoms in the growing chain. It must be concluded from the results that reactions take place, which change the number of active sites present, due to the different behavior of the polymers in solution. Study of these new catalysts is intensive. After a short induction period, the activity of polymerization increases as a function of the monomer concentration.
810 citations
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TL;DR: The optimal crosslinking dose provides a balance between these physical properties and the wear resistance of the implant and might substantially reduce the incidence of wear‐induced osteolysis with total hip replacements.
718 citations
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TL;DR: The effect of chemical treatment on the tensile properties of sisal fiber-reinforced LDPE composites was investigated in this article, where various chemical treatments were carried out to improve the bonding at the fibre polymer interface.
666 citations
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20 Jan 2000
TL;DR: In this paper, the basic history, molecular structure and intrinsic properties, practical applications and future developments of polyethylene production and marketing, including recycling systems and metallocene technology, are discussed.
Abstract: This text provides the basic history, molecular structure and intrinsic properties, practical applications and future developments of polyethylene production and marketing - including recycling systems and metallocene technology. It describes commercial processing techniques used to convert raw polyethylene to finished products, emphasizing special
659 citations