MODELING THE PVT BEHAVIOR OF ISOTACTIC POLYPROPYLENE

Making use of available data from the literature, a master correlation based upon a two-domain-Tait representation is developed which descri bes the asymptotic high-temperature and low-temperature PVT behavior o f isotactic polypropylene. The transition between these two asymptotes in the cooling mode is then handled based upon the quiescent-crystall ization-kinetics equation of Nakamura, employing model constants for t he temperature- and pressure-dependent crystallization rate based upon earlier work by the present investigator. As a further step, it is sh own that a rule-of-mixtures approach can describe the low-temperature and high-temperature asymptotic PVT behavior equally as well as the 2- domain-Tait model while requiring two less free parameters. In turn, s ince the rule-of-mixtures representation contains the absolute crystal linity as an explicit parameter, it is proposed that this model might also be used under flow-induced conditions once the corresponding crys tallization kinetics become established.