Comb-like copolymer dispersant for PP/CaCO3 composites: effects of particle concentration on properties of composites
Abstract A comb-like copolymer poly (styrene-co-maleic anhydride)-graft-poly (ε-caprolacton) (SMA-g-PCL, SP) with carboxyl group as an anchoring group and polycaprolactone as a solvent chain was used as an effective dispersant for CaCO3 in the polypropylene (PP) matrix. The effects of CaCO3 concentration on crystallization behaviors, mechanical properties, and thermal stabilities were studied systematically. The results revealed that the dispersion of CaCO3 in the PP matrix was markedly improved owing to the steric hindrance effect caused by PCL, and the SP-coated CaCO3 was a very effective nucleating agent for PP. Proper CaCO3 concentration corresponded to the improvement of crystallization temperature, crystallinity, and crystallization rate of PP. There was only a slight improvement in yield stress but great improvement in Young’s modulus, flexural modulus, and impact strength. However, the excessive CaCO3 filler deteriorated the mechanical properties. The good dispersion of SP-coated CaCO3 in the PP matrix also accounted for the improvement of thermal stability. The initial decomposition temperature of the PP/CaCO3 composite with 7.4 wt.% CaCO3 increased 35°C compared with neat PP.