Gel Spinning of Polyethylene

There is a second observation which is also directly related to the existing entanglement network A reduction in the entanglement density greatly increases the drawability of samples. One possible route for a reduction is the gel-spinning of polyethylene. High molecular weight polyethylene is dis-... 

A.J. Pennings, R.J. Van Derhooft, A.R. Postema, W. Hoogsteen, G. Ten Brinke, Hig speed gel-spinning of ultra high molecular weight polyethylene. Polym. Bull. 16(2-3), 167-174(1986)... 

In 4.3 we have already seen that polymers, in the rubber or fluid condition, crystallize much more rapidly when their chains are oriented. Therefore a stretched rubber, if stereospecific in its molecular structure, is able to crystallize at a temperature considerably above its equilibrium thermodynamic melting point. Also a thermoplast such as polyethylene, when in the molten state or in solution, can crystallize spontaneously when the chains are being orientated in elongational flow. The latter case is utilized when polyethylene is spun from a diluted solution (gel spinning process), resulting in fibres of super-high strength and stiffness ( Dyneema fibres). 

De Gennes scaling concepts for polymer solutions and melts and the concept of reptation movement of polymer chains in melts Pennings discovery of chain extension and shish-kebab formation in stirred solutions of very high MW polyethylene this eventually led to the ultra-high modulus gel-spinning process of polyethylene... 

The next major development was the "gel-spinning" by Smith and Lemstra (1979), where a "gel fibre" is first produced by spinning a dilute solution of very high molecular weight polyethylene into cold water after drying this "gel fibre" is drawn in a hot oven at... 

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. 

Figure 4.11 Flow diagram of the gel-spinning process of making ultra high molecular weight polyethylene fiber.

Some further studies of the gel spinning and drawing process have been undertaken by Manley and co-workers In polyethylene, their efforts were concentrated... 

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