Weibull statistics of tensile strength distribution of gel-cast ultra-oriented film threads of ultra-high-molecular-weight polyethylene

Abstract

Studies of the potentials of the multi-stage hot-zone drawing technique for enhancing the tensile strength (σ) of ultra-high-molecular-weight polyethylene (UHMWPE) gel-cast highly oriented film threads, the applicability of the Weibull statistics to the σ distribution, and the solvent role in the film thread strength are presented. It is shown that the results of a large number of mechanical measurements for two series of UHMWPE film threads drawn to an ultimate draw ratio (λ) of 120 from xerogels formed from 1.5 % solutions of UHMWPE in decalin or paraffin oil are satisfactorily described by the Weibull model. It is shown that the threads produced are characterised by an average strength σ av = 4.7 GPa and 20 % of the samples have σ = 5.2–6.5 GPa. This is higher than the strength of the commercially available gel-spun oriented UHMWPE fibres of σ = 3.5 GPa. It is found that the solvent nature does not affect the tensile strength of the film threads but exerts a considerable influence on the long-term characteristics.