Making use of available data from the literature, a master correlation based upon a two-domain-Tait representation is developed which describes the asymptotic high-temperature and low-temperature PVT behavior of isotactic polypropylene. The transition between these two asymptotes in the cooling mode is then handled based upon the quiescent-crystallization-kinetics equation of Nakamura, employing model constants for the temperature- and pressure-dependent crystallization rate based upon earlier work by the present investigator. As a further step, it is shown 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, since the rule-of-mixtures representation contains the absolute crystallinity as an explicit parameter, it is proposed that this model might also be used under flow-induced conditions once the corresponding crystallization kinetics become established.