Nucleating effect of calcium stearate coated CaCO3 nanoparticles on polypropylene

The ability of stearate coated calcium carbonate nanoparticles to promote the nucleation of polypropylene (PP) was investigated systematically. The effects of surfactant coverage and CaCO3 particle concentration were explored using differential scanning calorimetry as well as optical and atomic microscopies. The results indicate that at the crystallization temperature of PP, a monolayer stearate coating remains as a rigid layer and provides a noticeable nucleating effect. Insufficient or excess coating diminishes the nucleating effect, the former because of the formation of agglomerates, and the latter by forming a soft layer at the PP/CaCO3 interface at high temperatures, leading to the weak nucleating ability. Monolayer-coated nanoparticles had the strongest nucleating effect. The crystallization temperature and crystallization rate increased with the concentration of the monolayer-coated nanoparticles up to 40 wt.%.

Monolayer-coating surface is more effective to induce crystallization of polypropylene.Figure optionsDownload high-quality image (90 K)Download as PowerPoint slideResearch highlights
► Monolayer-coated calcium carbonate nanoparticles have the strongest nucleating effect on polypropylene (PP).
► A monolayer stearate coating remains as a rigid layer at high temperatures, serving as nucleation sites for PP.
► Good dispersion of monolayer-coated nanoparticles provides the maximum number of nucleation sites.
► Sub-monolayer coatings, which are soft layers at higher temperatures, do not provide effective nucleation sites.