Affiliation:
1. Bell Telephone Laboratories, Incorporated Murray Hill, New Jersey
Abstract
The dynamic Young's moduli E of molded films of a polyethylene and a polypropylene were found to decrease with increasing thickness t. An upper limit of E appears to exist when the film thickness is reduced to less than 1 mil. For thicker films, E is inversely proportional to t. Finally, the modulus approaches a lower asymptotic value when t is in excess of 20 mil. The results can be represented quantita tively by a model in which the surface transcrystalline region and the bulk phase of the polymer respond in a parallel com bination to the applied stress. The modulus of the trans crystalline region in each polymer is higher than that of the bulk phase. The thickness of a surface region is about 12μ in polypropylene and 15μ in polyethylene. The effects of thermal history and the nature of the molded surface were examined briefly.
Subject
General Earth and Planetary Sciences,General Environmental Science
Cited by
1 articles.
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