Analysis of the dynamic crystallisation of isotactic polypropylene/α-nucleating agent systems by DSC

The nucleation efficiency of dibenzylidene sorbitol, methyldibenzylidene sorbitol and 1,2,3,4-bis(3,4-dimethylbenzylidene) sorbitol in the crystallisation of the monoclinic phase of isotactic polypropylene has been evaluated by differential scanning calorimetry as a function of cooling rate and nucleation agent concentration. In order to analyse the nucleation activity of the additives, the self-nucleation process of the pure polypropylene has also been studied by thermal techniques. A large increment in the crystallisation temperatures has been obtained even for the lowest additive concentration, and the nucleating efficiencies are of the highest observed for alpha-nucleating agents in isotactic polypropylene.