Ultra-high-molecular-weight PE UHMWPE

Ultra-high-molecular weight PE (UHMWPE) Polyurethane (PUR)... 

Aerospace composite structures can also employ high-performance polymeric fibres such as the aramids Kevlar (DuPont) or Twaron (Teijin Twaron), poly(p-phenyl-ene-2,6-benzobisoxazole) (PBO) (Toyobo) and high-modulus polyethylene (PE) (Dynema, Certran and Spectra). Generally ultra-high-molecular-weight PE (UHMWPE) can be considered to be inert to most environments except that the service temperature is limited to <130 °C. 

Poly Hi Solidur Plastics India Limited [4] developed products for use on the Indian Railways based on ultra-high molecular weight PE (UHMWPE Hoechst s Hostalen GUR). The base polymer is mixed with patented additives and uses a computer controlled sintering process and sophisticated fabrication methods to produce a material which is claimed to have much higher values for a number of technically important properties such as wear, chemical and water resistance, impact strength and dynamic coefficient of friction. The growth of the market for UHMWPE products is briefly discussed, and the applications targeted by Poly Hi Solidur Plastics are discussed. 

In the mid-sixties, Dr. Pennings from the DSM Laboratories found that it was possible to retain complicated structures from a sheared dilute solution of ultra high molecular weight PE (UHMWPE). These structures proved to be a combinatbn of chain folded ard chain extended molecules. In a later stage. Prof. Pennings proved that perfection of this "shishkebab" structures could lead to the extreme mechanical properties we now know for Dyneema. 

Different polymer properties, that is the ability to form injection-moulded products, sheet, film, extruded products (tubes, fibres etc), all require different MWs. When the MW becomes greater than 10 then the polymer becomes difficult to process, since it will not melt and depolymerizes or decomposes when heated. These materials are fabricated by sintering (by applying pressure and heat). Examples include PTFE and ultra-high molecular weight PE (UHMWPE). 

Blends of LLDPE/PP = 50 50, with or without compatibilizing ethylene-propylene copolymer, EPR, were studied by Dumouhn et al. [1984]. In spite of the expected immiscibihty, the blends showed additivity of properties with good superposition of the stress growth functions in shear and elongation, as well as with the zero deformation rate Trouton ratio, Rj, = 1. In earlier work, blends of medium density PE (MDPE) with small quantities of ultra-high molecular weight polyethylene (UHMWPE) were studied in shear and extension. Again, SH and Rj, = 1 were observed. 

The focus in this chapter will be on the two main polyolefin polymers, namely polyethylene (PE) and polypropylene (PP). The latter especially has established itself as a very versatile fiber with unique applications in the textile and nonwoven industry. Polyethylene, on the other hand, has not been widely used as a fiber compared to other synthetic polymers such as PET, PP, and nylon, due in part to its low melting point. This chapter will, however, discuss ultra-high molecular weight polyethylene (UHMWPE) fiber that given its success and uniqueness in the synthetic fiber industry. 

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