The characteristics of crystallization, melting and spherulitie growth of a random propylene eopolymer (PRC) containing small amount of ethylene were studied in the presence of a selective 13-nucleating agent (calcium pimelate). It was established that the products of isothermal and non-isothermal crystallization are very rich in 13-modification but have mixed polymorphic composition. The formation of ct-modifieation may be attributed to 13or-transition on the surface of growing ~-spherulites resulting in cx~-twin-spherulites. During melting of PRC of [3-modification, the characteristics observed with 13-nucleated propylene homopolymers, namely, a 13c~-recrystallization of recooled samples and separated melting of non-reeooled samples (i.e. the melting memory effect), as well as a [3~3-reerystallization leading to a perfection of the structure within the 13-modification, are also demonstrated. The disturbance of regularity of the polymer chain highly reduees the tendency to 13-crystaltization. In contrast to the observations with propylene homopolymers, the growth rate of c~-modification (G,~) is higher than that of 13-modification (C~) and no critical crossover temperature can be found (T(13ot)=413 K) below which G~,< C_~. The experimental results ~how that a partial disturbance of chain regularity by incorporation of eomonomer units considerably reduces the tendency to [3-crystallization.

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Preparation, crystallization and melting characteristics of blends of β‐nucleated isotactic polypropylene with different elastomers and polyethylenes were studied. Blends of β‐polypropylene can be prepared if the polymer additive is amorphous or has negligible α‐nucleating effect during the crystallization of polypropylene.