The ceramic injection molding production system consists of a number of independent elementary processes. In the present study, the processing factors were taken up from four independent elementary processes and a statistically designed experiment using an orthogonal array was conducted. Thus the processing conditions under which the dispersion of the whole production system becomes the smallest were identified. The minimum dispersion conditions so identified were verified through a follow-up confirmation experiment. The material under investigation was sintered alumina. As a result, we reduced the variance of the dimensions of sintered molded products to one tenth of its original value.

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The strength and the microstructure of the weld region of injection molded test pieces of a polymer alloy of PPE (poly(oxy-2, 6-dimethyl-1, 4-phenylene)) and polyamide were studied. A distinctive weld line was observed at the weld region of an injection molded test piece. The strength of the weld region strongly depended on the width of the weld line. The effects of the molecular weights of the polymers, the types of the elastomer, the conditions of the reactive processing and the composition of PPE and PA on the weld strength were also examined. A microscopic observation of the weld region as well as the strength of the molded test pieces suggested that the dispersed phase, which is composed of PPE and the elastomer dispersed within the PPE phase, was strongly stretched near the weld region while it was molded, and subsequently moved apart from the weld region partially being displaced by polyamide during the cooling procedure.

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In order to obtain a fundamental knowledge of polymer blends, the rheological and thermal properties of two model blend-systems, (i) styrene-ethylene·butylene-styrene block copolymer (SEBS) and polystyrene (PS) and (ii) SEBS and polyethylene (PE), were investigated. And the effects of the interactions between the common segments of the component polymers on these properties and the mixed structures were discussed.
(1) The molten blends of SEBS and PS showed abnormal increases in the viscosities and the moduli and the remarkable decrease in the activation energy of flow at some mixed compositions. The flow curves of these blends exhibited remarkable yielding behaviors at low strain rate region. In these cases, the shear viscosity-shear rate curves of the blends did not coincide with the complex viscosity-angular velocity curves, and this result suggested, from the Cox-Merz rule, the existence of some heterogenous mixed structures in the molten state. Furthermore, these blends kept the high moduli even at low angular velocity region, suggesting the longer relaxation time due to the formation of some heterogeneous high order-structures. (2) In the SEBS/PE blends, such abnormal rheological behaviors could not be recognized but the approximately additive relations with the blend compositions were observed. (3) From the thermal analysis, the partial compatibilities between the component polymers through the common segment-units were recognized in both of the SEBS/PS and the SEBS/PE blend-systems. (4) From these results of the rheological behaviors and the thermal analysis, the complicated mixed structures of the SEBS/PS blends, due to the partial solubility of the PS chains into the St-domains of the SEBS and the consequent enlargement of the domain structures, were proposed.

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