The effect of concentration distribution of Gauche conformation on ultra-drawing of ultrahigh molecular weight polyethylene gel-films prepared from solution

Abstract

This paper reports the relationship between ultra-drawing and chain formation with gauche conformation in ultrahigh molecular weight polyethylene (UHMWPE) gel-films, which were prepared under several different concentrations, measured by infrared analysis. We demonstrated the effect of concentration distribution of gauche conformation on the ultra-drawing of UHMWPE gel-films. The relationship between the concentration distribution of gauche conformation and chain entanglement is also discussed here. It was found that the concentration of gauche conformation, defined by IR intensity ratio: σ = I1303/I1352, increased as the film-casting concentration increased. The UHMWPE gel-film prepared from the solution around the critical concentration (400–500 kg/m3) showed the highest draw ratio (λ > 300). The changes of gauche conformation concentration correspond to that of chain entanglement number deduced by Matuso from specific viscosity. The σ value of UHMWPE gel-films decreased to a constant one after heat treatment. The heat treatment temperature affected the σ value more than the heat treatment time did. The σ value remained unchanged after heating the sample for 5 min at the drawing temperature. These results are consistent with the hypothesis that annealing at the drawing temperature is a prerequisite stage to reach ultrahigh draw ratio (Spells and Hill, Polymer32 (1991) 2716). The UHMWPE gel-films could easily reach ultra-drawing (λ > 300) when they were drawn in the range of low σ values. These results were of great importance to detect and design the preparation conditions of UHMWPE gel-films deeply, the relationship between ultra-drawing and the structure texture and to ensure the ideal orientation of molecular chains.