In this paper, the effects of the equivalency of foaming time and temperature on the cell size and density, as well as the number of cells per unit volume remaining in foamed polystyrene (PS) plastics, are investigated. The foaming was carried out by the following procedure. First, a solid resin was saturated with a blowing agent under high pressure at a temperature lower than the glass transition temperature of the resin in a pressure vessel. After the blowing agent reached its saturation state, the pressure was released at a constant rate. The specimen was then taken out of the pressure vessel and heated in a hot bath to allow foaming under various foaming temperatures and times. Finally, the specimen was cooled in a water bath in order to halt cell growth. The following results were obtained.
(1) Cell size becomes small when the foaming time is shortened at a low foaming temperature and becomes large when the foaming time is lengthened at a high foaming temperature.
(2) Cell density increases when the foaming time is shortened at a low foaming temperature and decreases when the foaming time is lengthened at a high foaming temperature.
(3) The cell density of foamed PS shows an equivalency between foaming time and temperature, i. e., a master curve can be obtained. This suggests that a time-temperature equivalency law holds for cell density.
(4) The time-temperature shift factors obtained from constructing master curves gives two different Arrhenius activation energies, which are similar to the those describing the viscoelastic behavior of materials.
(5) Based on this equivalency of time and temperature, it is possible to predict the required foaming conditions of plastics having arbitrary cell densities.

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Injection molded plates using fiber-reinforced plastics often exhibit deformation due to fiber orientation. We would expect thin injection molded plates to have different material flow rates and fiber interactions than general thickness (3mm) plates.
In this report, a detailed examination of the deformation, fiber orientation distribution and thermal expansion coefficient anisotropy in thin injection molded plates using fiber reinforced plastics was conducted, and the following conclusions were obtained.
1) Twisting (warpage) occurs in the thin injection molded plates using fiber-reinforced plastics.
2) Thin injection molded plates form a three layer structure normally seen in thicker 3mm plates, however, the boundaries between the layers become indistinct.
3) The material property distribution in each layer in the thin injection molding plate is quite large when compared with thicker 3mm injection molded plates.
4) Fiber orientation and anisotropy of the thermal expansion coefficient are likely causes for the generation of twist (warpage) in thin plates molded from fiber-reinforced plastics

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