β-Nucleation of pimelic acid supported on metal oxides in isotactic polypropylene

To investigate the nucleation of metal pimelate for isotactic polypropylene (iPP) crystallization, iPP filled with a series of metal oxides with and without metal pimelate on their surface was prepared. There was a chemical reaction between pimelic acid (PA) and metal oxides MgO, CaO, BaO or ZnO, but not TiO2. The corresponding metal pimelate formed by the chemical reaction between PA and MgO, CaO, BaO or ZnO had a different influence on the crystallization behavior and melting characteristics of iPP. Addition of metal oxides increased the crystallization temperature of iPP and mainly formed a-phase due to the heterogeneous a-nucleation of metal oxides. The a-nucleation of CaO could be easily changed into beta-nucleation using CaO-supported PA, and 90.1% beta-phase was obtained. The beta-nucleation of BaO could be markedly enhanced by barium pimelate formed using supported PA. However, no beta-phase was observed for iPP filled with MgO- or ZnO-supported PA. The various metal oxides with supported PA had a different influence on the crystallization behavior and melting characteristics of iPP due to the different structure of metal pimelate formed by chemical reaction between PA and the metal oxides. Copyright (c) 2012 Society of Chemical Industry