Tensile strength of highly oriented polyethylene. II. Effect of molecular weight distribution

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Abstract
The tensile strength of oriented polyethylene filaments is discussed in relation to molecular weight. Short‐term tensile properties at room temperature were obtained in our laboratory and from the literature for polymer samples covering the molecular weight (Mw) range from 54 × 103 to 4 × 106, and polydispersities ranging from 1.1 to 15.6, oriented by solid‐state extrusion, melt spinning/drawing, solution spinning/drawing, and “surface growth.” It was found that both the molecular weight and its distribution markedly affected tensile strength. The breaking stress σ of highly oriented fibers varied with molecular weight roughly as σ ∝, M0.4, at constant Mw/Mn over the entire range studied. Reduction of polydispersity from 8 to 1.1 by an increase of Mn with Mw approximately constant at 105 increased tensile strength of oriented polyethylene filaments by a factor of nearly 2.