Spray drying preparation of polymethyl methacrylate-grafted natural rubber composite powders and its impact reinforcement effect

Encapsulation represents one feasible approach of preparing powdered natural rubber. Herein, we demonstrated the preparation of polymethyl methacrylate-grafted natural rubber (PMMA-g-NR) powders through emulsion polymerization followed by spray drying and investigated its impact reinforcement effect after blending with polylactic acid (PLA). The effects of feeding order, initiator concentration (CHPO/TEPA), monomer concentration (MMA) and reaction time on the grafting efficiency and yield were investigated. 1H-NMR and FTIR analyses confirmed the formation of PMMA-g-NR powder with high grafting efficiency (∼85%). TEM observations revealed the core-shell structure of the composite powder particles. DSC and TGA analyses proved that the PMMA-g-NR powder possessed improved thermal properties compared to neat NR. Impact strength of PLA/PMMA-g-NR blends were improved by 4.5-fold by the spray-dried composite powder prepared using 25 phr MMA and 1 phr CHPO/TEPA with 5 hours reaction time. The enhanced mechanical properties were attributed to the microstructures and high surface areas of PMMA-g-NR powder.