We have developed an approximate analysis method of polymer melt flow in dies, in which the velocity field was calculated by a pure-viscous non-Newtonian model and the stress field was obtained by substituting the velocity field in a viscoelastic model. The pure-viscous non-Newtonian model was modified so that the model could represent the strain-thickening effect of elongational viscosity. In order to examine the applicable range of this model to the flow analysis, we compared the velocity field for this model with that obtained from the Giesekus model with the same shear and elongational vsicosities in a two dimensional contraction flow with various entry angles and flow rates. It was found that the deviation between the calculated results from both models was under 10 percent up to We=70. Furthermore, the deviation between the stress fields obtained from this method and the mixed method using the Giesekus model was under 30 percent.
A numerical simulation of three-dimensional flow in tapered contraction was also carried out by this approximate analysis method. The calculated results of stress distributions were compared with the experimental values measured by the flow birefringence technique. The stress distributions calculated were in good agreement with the experimental values. It was concluded that this approximate analysis method was applicable to practical flow analysis.

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One of the important tasks in the analysis of the molding process is to directly observe the melt flow behavior inside an injection mold. Researchers have proposed visual molds with glass or acrylic inserted into a metal mold. One of the coauthors and his coworkers have developed a “Glass-Inserted Mold”, which was constructed from standard mold parts. This mold can be utilized on any injection molding machine, and it can be operated under usual injection pressures of less than 50MPa. By using this mold, we succeeded in observing the melt flow behavior under high injection rate and high injection pressure that could not be observed by other visual molds. However, up to now, we did not investigate whether the melt in the glass-inserted cavity and that in the metal cavity behave differently from cach other, i. e., whether the differences in the thermal conductivity coefficient, the specific heat, etc. between glass and metal cause different melt flow behavior.
In this paper, we propose a method to estimate the influence of the glass cavity surface on the melt flow behavior through comparing weld-line generation patterns, based on a new experimental Glass-Inserted Mold with a wide visible area. With this method, we investigated the above influence on the filling pattern and the pressure distribution. In conclusion, we confirmed that, if the molding experiments of GPPS were carried out with mold temperatures at least 20°C lower than the glass transition temperature of the melt, the influence of the above differences between glass and metal can be neglected.

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Polyaminobismaleimide oligomer was cured at various curing temperatures from 210 to 290°C. The relation between the curing temperature and structural characteristics of the resulting polymers has been investigated by means of IR, DTA, TG, TMA, tensile properties and dynamic viscoelasticity measurments.
The IR absorption peaks centered at 690 and 820cm^-1 decreased in intensity with increasing curing temperature. Because the bands are assigned to the double bond of the maleimide ring, the curing extent may be estimated from the band intensities. As the curing extent increased, the thermal expansion decreased regularly. The temperature dependence of the dynamic viscoelasticity in the temperature range of 200-300°C varied with the curing temperature as well. The E′ value decreased considerably from 200°C and recovered up to 300°C. This variation in E′ decreased gradually at higher curing temperatures and disappeared at curing temperatures above 270°C. The α relaxation peak of slightly cured polymer seen in E″-and tan δ-temperature curves decreased in height and shifted to higher temperatures with increasing curing temperatures. It was found that the initial increase in the strength and elongation at break was followed by a decrease at curing temperatures higher than 280°C.

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