Particle percolation in a poly(lactic acid)/calcium carbonate nanocomposite with a small amount of a secondary phase and its influence on the mechanical properties.

In this study, poly(lactic acid) (PLA) is blended with natural rubber (NR) to improve a brittleness of PLA. Surface‐modified inorganic particles of calcium carbonate are incorporated to this polymer blend not only to mitigate the strength loss but also to induce toughening of the PLA. Specifically, in order to toughen the PLA, the influence of NR as a second phase on the particle dispersion characteristics is examined while varying the concentration of the particles or the second phase and undertaking rheological measurements and morphological observations. With the surface‐modified particles, the secondary phase was found to induce the aggregation of particles along the interface as opposed to creating a homogeneous dispersion of particles. In addition, it enhanced the particle percolation throughout the blend and improved the brittleness of the PLA. With regard to elongation at break of the PLA/particle, it was increased from 12 to 86% by the addition of NR (19 vol%). On the other hand, for a composite with uncoated particles, the second phase of NR did not induce particle aggregation. Elongation at break of this composite decreased as the particle concentration increased. POLYM. COMPOS., 40:4023–4032, 2019. © 2019 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]