Mechanical properties of PP/kenaf core nanocomposites made from nanocrystalline cellulose as an additive

Abstract

Kenaf core contains a fairly high amount of cellulose and lignin; hence, any attempt to use both components would be beneficial. In this study, kenaf core was used as reinforcement in PP/kenaf core nanocomposites. The core was prepared in two forms: (i) as micron-size reinforcement and (ii) as nanocrystalline cellulose. The bleaching process for nanocrystalline cellulose was conducted at different intensities in order to retain different amounts of lignin in the pulp. Then, the nanocrystalline cellulose was prepared via hydrolysis reaction. Both the micron-size kenaf core pulp and the nanocrystalline cellulose of different bleaching intensity were loaded in the polypropylene matrix with the aid of maleic anhydride grafted polypropylene coupling agent. The mixtures were then hot pressed at 180°C for 8 min to form into standard testing size sample according to standard ASTM D638 (dumbbell shape for tensile test) and D790 (for flexural and impact test). The chemical, mechanical and morphological properties of the composites were evaluated. The results revealed that composites added with unbleached nanocrystalline cellulose (11.48% lignin content) had lowered the tensile and flexural strength. On the contrary, the impact strength was increased when unbleached nanocrystalline cellulose was added.