Nucleation of isotactic polypropylene with metal monoglycerolates

Isotactic polypropylene (iPP) has been modified with various nucleating agents, based on layered metal monoglycerolate complexes. Increased crystallisation temperatures (Tc) of iPP were observed in the presence of the isostructural zinc and cobalt layered monoglycerolates (ZMG & CoMG) and the structurally-related calcium monoglycerolate (CaMG), at loadings as low as 200 ppm, indicating highly effective nucleation. Optical microscopic observations showed that iPP nucleates from the thin edges/sides of CoMG and not from the larger area flat hexagonal/rhombic surfaces of the platelets. X-ray powder diffraction (XRD) studies revealed predominantly selective alpha -nucleation, although small amounts of the beta -phase were observed with CaMG/iPP. The (040) peak of alpha -phase of iPP was enhanced for nucleated injection moulded samples. Molecular modelling indicated a close structural match between the edges of nucleating platelets and alpha -iPP in multiple lattice directions, each with a dimensional mismatch of less than 4%.