Ultrahigh molecular weight polyethylene spinning

Extended-chain polyethylene fiber became available commercially in 1984 when DSM, a Dutch firm in the Netherlands, introduced Dyneema , and Mitsui Petrochemicals in Japan announced Tekmilon . Allied Signal of the United States entered the field in 1985 when it introduced Spectra fibers. These materials are characterized by very high strength and modulus, which are achieved by the use of ultrahigh molecular weight polyethylene spun by the gel spinning method into fibers having extended-chain structures and near perfect orientation. 

In gel spinning, a variant of solvent spinning, the polymer is fed as a gel instead of a solution. With gel spinning, very high orientation and strength are possible. The most widely known fiber made by this process is Spectra and Dyneema, both made from ultrahigh molecular weight polyethylene. 

Highly oriented flexible-chain polymers, in particular ultrahigh-molecular-weight polyethylene (UHMWPE) fibers prepared by gel spinning process, as suggested by Smith and Lemstra [322], exhibit the extremely high mechanical strength and modulus of elasticity rather close to the theoretical estimates. At the same time, these fibers reveal decreased creep resistance which substantially restricts their application potential. 

As described earlier, the main prerequisite for the creation of high performance self-reinforced polymer composites is a thermoplastic polymer fibre with the necessary mechanical properties to make the creation of the final composites attractive. Ultrahigh molecular weight polyethylene (UHMWPE) fibres with veiy high mechanical properties, produced by gel spinning, became commercially... 

Solution and gel spinning have much in common [47-50] the outlines of both processes are illustrated in Figure 9. The initial step in both processes is the dissolution of ultrahigh molecular weight polyethylene in a large excess of... 

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