In Situ Intercalation Green Polymerization, Characterization, and Kinetics of Poly( lactic acid)/Zinc Oxide Pillared Saponite Nanocomposites

Poly(lactic acid) (PLA)/Zinc oxide (ZnO) pillared saponite nanocomposites were prepared with ZnO pillared saponite as the green catalyst and lactic acid as monomer through in situ intercalation polymerization method. The optimum polymerization parameters were as follows the addition content of ZnO pillared saponite was 1% (wt) and the reaction was running at 180 degrees C for 7 h. The Fourier transform infrared and H-1 NMR results showed that the polymerization sample was PLA; Gel permeation chromatography result showed the PLA had a narrow molecular weight distribution, which arranged from 3,000 to 5,000 and the polydispersity index of PLA was 1.2. Differential scanning calorimetry showed ZnO pillared saponite improved the crystallinity of PLA. Thermogravimetric analysis showed the thermal stability of PLA-based nanocomposites were improved by ZnO pillared saponite. It was shown that in situ intercalative polymerization kinetics model of PLA/ZnO pillared saponite nanocomposites accorded with third order, and the activation energy of polymerization reaction was 49.3 kJ/mol under the polymerization reaction conditions as follows: the vacuum degree was 0.085 MPa, the temperature was 130 degrees C, and the reaction extent was 2.35 approximate to 47.69%, the content of ZnO pillared saponite catalyst was 1 wt%. POLYM. COMPOS., 35:1023-1030, 2014. (c) 2013 Society of Plastics Engineers