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Mechanical anisotropy in injection‐molded polypropylene
Author(s) -
Fujiyama Mitsuyoshi,
Awaya Hiroshi,
Kimura Shukichi
Publication year - 1977
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1977.070211209
Subject(s) - materials science , composite material , ultimate tensile strength , anisotropy , necking , polypropylene , flexural strength , flexural modulus , melt flow index , modulus , polymer , optics , physics , copolymer
By use of a mod with a film gate, two straight polypropylenes (PP) with different melt flow index ( MFI ) and a glass fiber‐reinforced polypropylene (FRPP) were injection molded at various molded at various temperatures into square plates with orientational anisotropy. The anisotropies of tensile property, tensile impact strength, and flexural property were studied on the molded sample cut mainly in the machine direction (MD), 45°‐direction (45°), and transverse direction (TD). Both the orders of the yield strength and tensile impact strength of the FRPP, and those of the necking stress and tensile impact strength of the straight PP, were MD >45° >TD, which are reasonable tendencies. The orders of the yield strength and flexural modulus of the straight PP were MD > TD > 45°, which suggests the presence of shear deformation between the lamellae in the skin layer. The variation of the flexural modulus with the angle to the MD fitted well to Hearmon's equation. Generally, for straight PP, the anisotropy of various properties increased as the MFI and cylinder temperature became lower, or as the skin layer became thicker. For the FRPP, the anisotropy increased as the cylinder temperature became higher, or as the degree of the orientation of glass fibers became higher.