Drawing properties and physical properties of ultrahigh-molecular-weight polyethylene swollen in mixed solvent

We report new conditions for obtaining high-strength and high-modulus polyethylene using the swell-drawing process which was introduced by Mackley and Solbai [Polymer, 28, 1115 (1987)]. Cyclohexane-toluene mixture was used to allow polyethylene with M-w of 1.75 x 10(6) to swell significantly at relatively low temperature. We found that a dumbbell-shaped polyethylene specimen swelled under stress gained higher drawability in subsequent drawing processes. It was confirmed that in a polyethylene specimen swelled and elongated under an optimal stress, the fibrillar textures were oriented without recrystallization in the direction of elongation. The specimen showed highest draw ratio when the solvent in the swollen polyethylene was reduced to 30% of the polyethylene in weight. Under these conditions a maximum tensile strength of 3.5 GPa and modulus of 120 GPa were achieved. These values are greater than those for the fiber prepared by Mackley and Solbai [Poly-titer, 28, 1115 (1987)] who used polyethylene with molecular weight greater than 10(6). The present results show that the improved swell-drawing method, where polyethylene specimen swelled and elongated under appropriate stress is drawn, can be used for the production of high-strength and high-modulus fiber from ultra-high molecular weight polyethylene. The result suggests the applicability of the method for polyethylene of much larger molecular weight.