Enhanced thermal and transport properties of PP/CaCO₃ micro- and nanocomposites: performance evaluation

Mechanical tests previously demonstrated that optimizing the dispersion of micro- and nanoparticulate CaCO₃ in polypropylene (PP) composites was successfully achieved through a Design of Experiments (DOE), enabling the identification and guided processing parameters for further evaluation of thermal and barrier properties. The formulation with 1.2 wt% nanofiller exhibited enhanced crystallinity compared to hPP. The incorporation of ~4.0 wt% nanoparticulate CaCO₃ increased the Heat Deflection Temperature (HDT) by 12 °C compared to neat homopolymer polypropylene (hPP), and by 3 °C relative to microfilled composites. Oxidation Onset Temperature (OOT) improved with increasing filler content, especially in nanocomposites. A slight reduction in flammability was observed for the composite with ~0.5 wt% nanofiller. Water Vapor Transmission Rate (WVTR) remained mostly unchanged in microcomposites, while a 1.5 wt% microfilled sample showed excellent Oxygen Transmission Rate (OTR) performance. Notably, nanocomposites containing 0.48wt% CaCO₃ reduced OTR by 52%, confirming their thermal stability and barrier properties at low filler loadings.

Keywords:
calcium carbonate; polypropylene nanocomposites; barrier properties; oxygen transmission rate (OTR); water vapor transmission rate (WVTR)