Abstract
The effect of solid state extrusion on the crystal density of polyethylene has been investigated with the help of wide angle X-ray diffraction studies. It is found that unit cell parameters a- and b- increase with increase in extrusion ratio R while the parameter c- remains practically unaffected. This implies that the crystal density decreases with increasing R. We have also determined the change in the degree of crystallinity X as a function of R by X-ray diffraction. It is found that X increases with R. Using the usual relation connecting X with the observed specific volume of the semicrystalline polyethylene, the specific volumes of the crystal phase and the amorphous phase, the change in the amorphous specific volume with R has been determined. These results are analysed in terms of Peterlin’s model of plastic deformation in semicrystalline polymers and compared with the corresponding reported data for drawn samples. Finally taking account of observed changes in the degree of crystallinity, the crystal and amorphous specific volumes due to extrusion, we have determined the entropy difference ΔSR, between the unoriented and the oriented amorphous phase as a function of R from the corresponding data for heat of fusion.
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Dhawan, K., Jain, P. & Nanda, V. The Effect of Solid State Extrusion on Some Physical Properties of High Density Polyethylene. Polym J 17, 577–585 (1985). https://doi.org/10.1295/polymj.17.577
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DOI: https://doi.org/10.1295/polymj.17.577