The structure, properties, and foaming of long chain branched polypropylene/clay-supported calcium pimelate composites

Long chain branched polypropylene/clay-supported calcium pimelate (LCBPP/CaHA-OMMT) composites and their foams were prepared using self-made CaHA-OMMTs. The CaHA-OMMT showed high beta-nucleation efficiency, especially that with larger initial interlayer distance could induce 89% of beta crystal in LCBPP with a dosage of 0.5%. Clay layers were mostly exfoliated in the composites with low CaHA-OMMT content, while intercalated structure was dominant and agglomeration occurred when the content of CaHA-OMMT was higher than 2%. The composite foams were prepared with improved compression molding. The cell structure of the composite foams is improved, that is, the density, cell size, and cell size distribution decreased, and the cell density increased compared with that of LCBPP foam. The minimum average cell size of LCBPP/CaHA-OMMT foams was 77 mu m and the maximum cell density was 2.8 x 10(6) cells/cm(3) with the CaHA-OMMT content of 2%. It is concluded that there are two requirements for high nucleation efficiency: the CaHA was supported on OMMT layers, and the OMMT platelets were dispersed well and exfoliated. The compression properties of the composite foams, including compression modulus, energy absorption density and failure strength increased first and then decreased with the increase of CaHA-OMMT content.