Abstract:

The present short review aims to summarize advanced nucleating agents for polypropylene (PP). Reviewing the relevant literature, we focused on powerful nucleators that are capable of significantly increasing the crystn. temp. of the polymer at very low working concns. and also serving as clarifying agents. The nucleation mechanism and efficiency of these compds. are discussed in detail. The nucleating agents were divided into groups according to their tendency to induce monoclinic ($\alpha$), hexagonal ($\beta$), or orthorhombic ($\gamma$) PP cell geometries. The major $\alpha$-nucleators and clarifiers are sorbitol-based compds. that speed-up the polymer crystn. due to gelation phenomena and induction of epitaxial crystn. by the metal salts of substituted arom. heterocyclic phosphate. Among $\beta$-nucleators, N,N'-dicyclohexyl-2,6-naphthalene dicarboxamide was found to be very efficient and its nucleation ability was highly concn. dependent. In addn., it was shown that nucleation efficiency of a nucleator can be significantly increased by a new dispersion method comprising its solubilization in a microemulsion. Moreover, the nucleator (HPN-68) increased the $\gamma$-modification present in the polymer. [on SciFinder(R)]