Interface-engineered polypropylene/cellulose nanofibril composites with enhanced thermal stability, mechanical modulus, and impact strength

To attain interface-engineered polypropylene/cellulose nanofibril (PP/CNF) composites with improved thermal and mechanical performance, PP was grafted with glycidyl methacrylate (GMA) and styrene via direct melt-mixing and GMA/styrene-grafted PP (PGMA) was reinforced with 1-10 wt% CNF content through a mass-producible melt-compounding process. The spectroscopic analyses confirmed the existence of specific hydrogen-bonding interactions between CNF and PGMA in the composites. The melt-rheological measurement revealed the occurrence of chemical reactions between the hydroxy group of CNF and the glycidyl group of PGMA of the composites. Accordingly, the dispersion and interfacial adhesion of CNF in the PGMA matrix was improved. beta-form PP crystals were also developed by accelerating the crystallization of PGMA and PGMA/CNF composites, unlike PP with only alpha-form crystals. The storage modulus of PGMA/CNF composites was enhanced noticeably with increasing CNF content. Moreover, the impact strength of PGMA composite with 1 wt% CNF was found to be 29.2% higher than that of neat PP.

Automated summary

Interface-engineered polypropylene/cellulose nanofibril (PP/CNF) composites with improved thermal and mechanical performance were successfully obtained through grafting modification and nanofiber reinforcement. Spectroscopic analyses confirmed the presence of specific hydrogen-bonding interactions, and melt-rheological measurement revealed chemical reactions, improving the dispersion and interfacial adhesion of nanofibers in the composite matrix. Additionally, by changing the crystalline form, the storage modulus of the composite was further enhanced, and the impact strength was significantly improved.