Mechanical properties, thermal stability, and crystallization kinetics of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)/calcium carbonate composites

polyester poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) containing 5 mol% 4HB was composited with different calcium carbonate (CaCO3) fillers. The effect of CaCO3 contents on thermal properties, mechanical property, and crystallization kinetics was evaluated. The thermal stability of P3/4HB was reduced by mixing with CaCO3 particles. With increasing CaCO3 content, the elongation at break, tensile strength, and impact strength decrease; however, elastic modulus increases. When P3/4HB with 20 mol% 4HB was added into the P3/4HB/CaCO3 composite, the impact strength were enhanced significantly; however, the elongation at break and tensile strength were only slight to moderate improvements. However, when compared with nano-and light-CaCO3, heavy CaCO3 had the best mechanical properties. The nonisothermal and isothermal crystallization results demonstrated that the crystallization rate of P3/4HB was reduced and the highest crystallinity was obtained for all kinds of CaCO3 fillers at 40 phr content. POLYM. COMPOS., 32: 1134-1142, 2011. (C) 2011 Society of Plastics Engineers