| Abstract: | The tensile drawing behavior of a range of selected polyethylene copolymers has been studied. Sheets were prepared by quenching molten polymer into cold water. Two-centimeter-gauge-length samples were then drawn in air at 75 or 115°C in an Instron tensile testing machine at a crosshead speed of 10 cm/min. It was found that even at the very low concentration of one side branch per 1000 carbon atoms there was a very marked effect on the strain hardening behavior and the maximum draw ratio that could be achieved. The reduction in draw ratio increased with increasing branch concentration, and long branches were more effective than short branches in limiting the draw ratios achieved. The similarity between these effects and the effects of increasing M?w or radiation crosslinking is noteworthy. This suggests that even a very small concentration of branches can significantly reduces the moleculer motions required for the process of plastic deformation. The Young's modulus/draw ratio relationship follows a pattern virtually identical to that observed in the case of homopolymers. |
