Particle network formation in poly(lactic acid)/calcium carbonate composite with natural rubber and its effect of mechanical properties

Abstract

Since poly(lactic acid) (PLA) has similar properties of commercial polymer, PLA has been received considerable attention as an alternative to petroleum based polymer. However, inherent brittleness of PLA is major drawback. Rubber toughening is common way to overcome brittleness of PLA. In the various studies, by controlling the morphology of rubber, brittleness of PLA could be compensated. However, rubber toughening caused decrease in stiffness. This property of polymer could be enhanced by adding nanoparticles to polymer. For effective improvement of stiffness, manipulating dispersion and structure of particles is major issue. In other word, for making stiffness-toughness well-balanced PLA/NR/particle composite, controlling not only morphology of dispersed phase but also dispersion and structure of particle is essential. In this study, PLA is blended with NR in order to compensate brittleness of PLA. Inorganic particles, calcium carbonate, are incorporated to this polymer blend in order to not only minimize the decrease of strength but also improve the compatibility between two polymers. It is expected that the excess particles will not only play a role of being located at the interface of two polymer but also will deform the dispersed phase. It is also expected that the dispersion state of the particles will be changed because dispersed phase will induce the aggregation of the particles. We focus on the microstructure of ternary composite in terms of controlling both particle dispersion and dispersed phase morphology simultaneously. With changed an interaction between particle and dispersed phase, mutual effect of particle and dispersed phase was investigated. The effect of the content of particles, dispersed phase on morphology of ternary composites was also examined. To investigate dispersion and structure of particle and morphology of dispersed phase, rheological measurement and morphological observation were conducted.

Key words: Biopolymer, particle network, mechanical properties