Anisotropy in Thermoplastic Moldings and Their Impact Strength.

摘要

The mechanical anisotropy of several thermoplastic polymers has been investigated, and the relationship with a practical dart drop impact measurement has been explored. It has been shown that the unnotched Izod impact strength of a specimen taken perpendicular to flow orientation can be correlated with the dart drop impact strength. Further, the effect of several dart drop test variables, such as drop height, dart tip radius, and specimen size, have been investigated and reported. It has been concluded that the conventional strength measurement of injection molded specimens may lead to erroneous appraisal of the practical strength of a material. Testing at an orientation normal to flow or by multiaxial stressing as in a dart drop test is suggested.