Morphological structure, impact toughness, thermal property and kinetic analysis on the cold crystallization of poly (lactic acid) bio-composites toughened by precipitated barium sulfate

Abstract

The bio-composites of poly (lactic acid) (PLA) involving a varied mass fraction of precipitated barium sulfate (BaSO4) were prepared via melt-compounding and subsequent injection molding. The morphologies, impact toughness and thermal properties of the composites were investigated carefully, and the toughening mechanism was emphasized by a combination of BaSO4 content and the crystallization ability. Results showed that an adequate amount of BaSO4 could disperse homogeneously in PLA matrix with well-bonded interfaces. The impact toughness was increased significantly by 52.7% due to added inorganic particles as well as the increased actual crystallinity of the composites. The added BaSO4 let the cold crystallization occur earlier (shifting to low temperature) while suppressing the cold crystallinity of PLA phase. Such inhibition effects derived from the increased inorganic filler were then further explored and confirmed by the kinetic analysis on the cold crystallization under non-isothermal conditions. Indeed, the added BaSO4 increased the crystallization half-time and crystallization parameter of F(T) based on Mo equation. Moreover, the activation energy on cold crystallization was strengthened along with the increasing BaSO4. It seemed that there is little change in the reaction order of PLA/BaSO4 bio-composites, following the unique reaction thermal decomposition, whereas the activation energies were decreased steadily based on Carrasco method.