This paper deals with a model that can predict flow-ability improvements due to radiation heating for the injection molding process. The model is derived through considering the thermal energy balance within a molded product, and can provide a quantitative estimation without the need for complex heat transfer calculations or numerical simulation of the polymer flow. Experimental molds, equipped with a transparent window (heat-resistant glass), were used to mold simple disc shaped samples. Infrared radiation, which was provided by a high power infrared lamp, was introduced from the outside of the mold and directly irradiated the molten polymer to maintain its flow-ability during the filling stage. The weight of all the molded products were measured with an electronic balance to investigate the effect of the following molding parameters: wall temperature, melt temperature, flow rate of the melt, product thickness, radiation absorption coefficient, and irradiation intensity. Flow available time, meaning the time that the polymer melt can be kept flowing in the cavity, was introduced. It was calculated by considering the thermal energy balance that includes all the parameters listed above. The estimation of the molded product weight by the model agreed well with the experimental results under various molding conditions.

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Aliphatic polyesters as biodegradable plastics have been studied and their commercial applications are growing progressively. Processability to be applied to conventional forming methods must be an important factor to extend the applicability of biodegradable plastics. It has been known that long chain branching contributes excellent processability of polyethylene and polypropylene. For aliphatic polyesters the introduction of long chain branching (LCB) is expected to improve their processability. In this study the molecular structure, viscoelastic properties of the melts and processability for direct extrusion gas foaming were investigated for branched poly (butylene succinate) (PBS-B) which was copolymerized with multifunctional monomer and linear poly (butylene succinate) (PBS-L). It was found that the PBS-B showed a broad distribution of molecular weights and existing of LCBs in a molecule. Futhermore, the PBS-B had longer relaxation time components in dynamic viscoelasticity and showed strain hardening in the elongational viscosity measurement, while PBS-L did not show such characteristics.
The processability of direct extrusion gas foaming for PBS-B was thereby drastically improved, e.g. we were able to obtain biodegradable foamed sheet products having densities from 30 to 250kg/m³ and thicknesses from 0.5 to 3mm, while PBS-L did not show such good processability. In addition, these foamed sheets were stable in the atmosphere for 2 years, but biodegradable in hot compost or in moist soil under aerobic conditions where a large number of microorganisms was present.

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DRI (Die Rotary Injection) is a new injection molding method that can fabricate tubular products by the conventional injection molding process. The process of making tubular products by this method is as follows.
1. Fabricate a pair of half products.
2. Open the mold. (a half product is kept in the mold)
3. Rotate a part of the mold to oppose each half product.
4. Inject a resin in the gap between the half products.
The most important step in this process is to ensure the reliability of the welding.
In this paper, the welding mechanism, material properties and injection conditions for high welding strength were investigated. The possibility of welding with different materials was also discussed.
The results showed that the surface of the primary resin was melted by the molten secondary resin. The requirements for high welding strength were concluded as follows.
1. A primary resin should be compatible with a secondary resin.
2. The molding temperature of a secondary resin should be higher than that of a primary resin.
3. A secondary resin should be molded at high temperature and high injection speed.
4. In the case of crystalline polymers, it is necessary that the melting latent heat should be lower than the crystallization latent heat.

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