A green and efficient method to prepare oleic acid–modified CaCO3/reHDPE composites

Industrial recycling of waste plastics frequently utilizes mechanical recovery and recycling. However, plastics recycled through mechanical recovery tend to have reduced properties, limiting their applications. In this study, modified calcium carbonate (OA-CaCO3) was prepared using different amounts of oleic acid (OA) (0.5, 1.0, and 2.0 wt%). Infrared spectroscopic characterization showed OA was successfully adsorbed on the CaCO3 surface. Particle size, micromorphology, oil absorption value, and activation tests indicated that CaCO3 modified with 1.0 wt% OA yielded optimal results. Melt blending 1.0 wt% OA-modified CaCO3 with recycled high-density polyethylene (reHDPE) produced composites. Scanning electron microscopy results showed OA modification enhanced interfacial compatibility between the two phases. Mechanical property tests revealed at high filling levels, the impact strength of OA-modified composites increased considerably, reaching 42.6 kJ/m2 with 40 wt% OA-CaCO3 filling. Melt flow rate test results showed that OA-modified composites had increased melt flow and modified processing properties. Filling OA-CaCO3 to compensate for reHDPE properties caused by mechanical recycling is essential to expand mechanical recycling applications in plastics recycling.