Crystalline recovery of quenched polyethylene

0022-3832

Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Physics

The effect of time and temperature on the crystalline recovery of quenched Marlex 50 polyethylene has been investigated. Quenching thin films in ice water reduced the room temperature crystallinity from a normal value of 93 to 82%. These specimens were maintained at 25, 66.2, and 106.4°C., and the time variation of crystallinity was followed by nuclear spin resonance. The crystalline recovery appears to follow the empirical formula, X = A + B log t, where X is the percentage crystallinity and t, is the time in hours. The rate, X, increases with temperature. The temperature-dependence of B was computed by assuming the rate to be controlled by diffusion in the amorphous phase. The temperature-dependence of diffusion is determined by nuclear spin resonance line width measurements to be exp {-8700/RT}. The rate is then X = C/t exp {-8700/RT}, and C, evaluated at 25, 66.2, and 106.4°C., is 2.2 ± 1.9, 1.7 ± 0.5, and 2.1 ±0.2 × 105. This agreement is within the probable error, and justifies the assumption of diffusion as the rate-controlling factor. The result is X = 2.04 × 105(1/t) exp { -8700/RT} and X = A + 4.70 × 105 log t exp {-8700/RT}.

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