The relationship between the swelling behavior and blow molding processability of polypropylene/polyethylene blends was investigated. Polypropylene (PP) and low-density polyethylene of different MFR (PE) were prepared by melt blending. A blow molding grade of high-density polyethylene (HDPE) was also used as a reference for blow molding processability. The swelling ratio of PP and PE increased with an increase in shear rate. On the other hand, the shear rate dependence of the swelling ratio of specific PP/PE blends and HDPE was very small. The mixture rule could not explain the swelling ratio behavior of PP/PE blends. The influence of slip phenomenon on swelling behavior was investigated. Slip phenomenon was observed for every sample, but its influence on the shear rate dependence of the swelling ratio was not significant. Parison extrusion characteristics were measured by using a pinch-off mold, and blow molding was also performed. The parison weight of PP/PE blends with a small shear rate dependence of the swelling ratio changed linearly with the die gap. Therefore, the thickness distribution of the blow molded product changed slightly when the die gap was altered. The change of parison weight with an increase of throughput was small. The weight and thickness distribution of the product was also not influenced by the throughput. It was concluded that a small shear rate dependence of the swelling ratio was the reason for good blow molding processability and parison control.

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In injection molding, it is very inefficient in time and cost to correct a mold. Thus there are many research programs to apply numerical analysis to determine by calculation appropriate molding conditions for targeted values.
We have been using a genetic algorithm (GA) based on a discrete optimization method for multi-cavity molds. In this GA-based optimization calculation, if a design variable increases, the solution space spreads, the calculation takes time and the convergence speed is affected. Thus a grouping of the design variables was carried out, and an algorithm to acquire the optimal forming conditions more easily for many design variables was developed.
In this paper, we will explain the developed algorithm and report the results of calculations.

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Warpage of injection-molded products can be largely attributed to two principal factors. One is a flow factor related to the anisotropy or distribution of the coefficient of linear expansion as a result of the molecular orientation produced by the resin flow. The other is a thermal factor related to shrinkage differences stemming from different rates of cooling in the molded product. In an actual molding process, the mold temperature is asymmetrical due to the mold and product geometries. Shrinkage differences between the low and high temperature sides are especially apt to cause warpage. It is also thought that Warpage may occur due to the effect of the asymmetrical mold temperature on the resin flow. However, there do not appear to be any reports in the literature of studies concerning the effects of the asymmetry of the mold temperature on resin flow characteristics.
In the present research, visualization experiments were conducted to determine the effects of the asymmetry of the mold temperature on the resin flow and its relationship to the molecular orientation ratio. The results made the following points clear.
(1) Under conditions of an asymmetrical mold temperature, the solid layer grows more slowly on the high temperature side than on the low temperature side and the mainstream of the resin flow shifts to the high temperature side.
(2) Shear stress induced by the distribution of the resin flow velocity in the thickness direction has the effect of increasing the molecular orientation ratio on the high temperature side, with the result that the distribution of the thermal expansion is affected.

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