The effect of cooling time of the injection moldings on the therodynamic equation of state

摘要

The dependencies between the pressure (p, in the range 0.1-120 MPa), specific volume (v) and temperature (T) during the isobaric cooling of polypropylene injection moldings, obtained after various cooling time in the mold cavity (11s,20s or 29s) [15] have been investigated. The results o investigations were presented in the p-v-T graphs (Figs. 2-4). On this basis the constants in the thermodynamic equation of state by Tait as well as in the IKV equation have been determined; these constants have been determined for solid and molten state of PP in relation to cooling time of moldings (Tables 3-6). The assessment of the values of relative errors of approximation has been done using two discription of the courses of curves in p-v-T graphs, obtained on the basis of measurements (Tables 2 and 5). The effect of cooling time of injection moldings on the course of curves describing the dependencies of specific volume on the temperature has been also analyzed.