SynopsisBy use of a mod with a film gate, two straight polypropylenes (PP) with different melt flow index (MFZ) and a glass fiber-reinforced polypropylene (FRPP) were injection 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 > 45O, 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.

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synopmsIt is the object of the present study to obtain clear knowledge of the relations in the polypropylene melt between its linear viscoelasticity and its nonlinear steady capillary flow, paying particular attention to the elastic properties in its capillary flow. By representing the linear viscoelasticity numerically with zero-shear viscosity, q0, and steady-state compliance, Je0, evaluation has been made of the properties concerning the elasticity of polymer melt in the capillary flow, such as non-Newtonianity, the entrance pressure loss, the end correction, the Barus effect, and the melt fracture. The steady flow viscosity q, the entrance pressure loss Po, the critical shear stress, T~, and the critical shear rate +, at which melt fracture begins to occur are subject to 70 as follows:log $ a log qo, log P o a log 70, TC alog 70, log 9, alog $0.From the well-known relationship between $0 and the weight-average molecular weight 2,, these quantities are governed by M, . Meanwhile, for such quantities tls structural viscosity index N, end correction coefficient Y, and elastic pressure loss ratio Po/P, following correlations hold: N 0: log ($0.Jeo), log P a log ($oZ.J2), Po/P a log (qo*.J,O). As 70 and J,O are respectively determined mainly by $w and the molecular weight distribution MWD, these quantities are governed by both a, and MWD. Physical meanings of qO-Jeo and qoz-Jao are, respectively, mean relaxation time and a measure of stored energy in steady flow. The Barus effect has a positive correlation t o J,O, Y, and Po/P. (The symbol a employed here means positive correlation.)

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