Poly(lactic acid) based nanocomposites: mechanical, thermal and rheological properties and morphology

Açık, Eda
The aim of this study was to increase the potential applications of poly(lactic acid) (PLA) by incorporating reactive functionalities with different nano-scale fillers. To investigate the effects of nanoclay types, five different organically modified nanoclays (Cloisites®15A, 25A and 30B and Nanofils®5 and 8) were used. Two elastomeric compatibilizers, ethylene-glycidyl methacrylate (E-GMA) and ethylene-butyl acrylate-maleic anhydride (E-BA-MAH), were added to the nanocomposites produced via melt compounding. The degree of clay dispersion was determined by the chemical compatibility between the polymer matrix and the modifier. Compatibility between C25A, C30B and E-GMA resulted in better dispersion and thus, enhanced tensile modulus and toughness. The network structure formed owing to the high reactivity of the epoxide group of GMA towards the PLA end groups resulted in high impact toughness and solid-like behavior in the melt state. Effects of filler loadings with different production methods (melt compounding and solution mixing) were investigated with expanded graphite (EG) as the filler. Filler loading was kept below 2 wt. % to minimize the dispersion problem and solvent usage. No significant changes were observed in filler dispersion in both methods. However, when E-GMA was added, melt compounded blends had phase separated matrix morphology and solution mixed blends had continuous matrix morphology. Significant decreases in ultimate tensile strength and elastic modulus, but increased strain at failure were observed for samples prepared by solution mixing. Enhancements in elastic behavior and complex viscosity of composites in the melt state are other remarkable outcomes of addition of E-GMA by the solution mixing method.
Citation Formats
E. Açık, “Poly(lactic acid) based nanocomposites: mechanical, thermal and rheological properties and morphology,” Ph.D. - Doctoral Program, Middle East Technical University, 2014.