射出成形による結晶性樹脂のP-v-T特性評価に関する研究

第1報 固相における状態式定数の決定

抄録

The P-v-T properties of polymers play a very important role in the prediction of warpage and shrinkage using computer aided engineering (CAE) programs. The usual measurements of P-v-T properties generally need very low cooling rates in order to make the temperature distribution uniform in the specimen, but the cooling rate in injection moldings is very high and changes with molding conditions. Therefore, the P-v-T properties obtained by the usual methods have some problems in applying them to the analysis of crystallization behaviors in injection moldings. In order to solve these problems the practical P-v-T measurement method has been proposed by taking the cooling rate in injection molding process into account. The undercooling which is defined as the difference between the melting point and the crystallization onset temperature, can be represented as a function of the cooling rate and the pressure history in the injection molding process. We have found that the specific volume of the molded specimen at a pressure 1atm at 293K could be estimated as a function of the undercooling. By taking it into account, the specific volume variations with temperature and pressure were calculated from the thermal expansion coefficient α_V and the compressibility κ. Then the constants of Spencer-Gilmore's equation of state obtained from these P-v-T properties are determined as a function of undercooling. Hence it is shown that the obtained Spencer-Gilmore's equation of state accompanying with appropriate constants indicates good agreement with the P-v-T properties in the solid phase over the wide variations of injection molding conditions.