Characterization of mechanical and morphological properties of cellulose reinforced polyamide 6 composites

The utilization of cellulose in reinforcing engineering thermoplastics through melt compounding processes is an argumentative topic in the natural fiber research community. Three different cellulosic materials were used to reinforce polyamide 6 (PA6) at three loading levels (2.5, 5 and 10 % by weight): (1) microcrystalline cellulose, (2) spray-dried cellulose nanofibrils (CNFs) and (3) spray-dried cellulose nanocrystals (CNCs). The particle size, morphology, and thermostability of cellulose were determined using laser diffraction, scanning electron microscopy (SEM), and thermogravimetric analysis. Compounding of cellulose with PA6 was conducted using a batch mixer at 232 °C and testing samples were produced using an injection molder at 270 °C. Slight mass loss of cellulose was observed at 232 °C while serious thermal degradation occurred at 270 °C. No serious thermal degradation of cellulose was observed in the composites because the cellulose materials were exposed to injection molding processing temperatures for a short time period. The mechanical testing results indicated that tensile modulus and strength of the composites were improved by adding cellulose while cellulose had negligible effect on the flexural properties. Impact strength decreased significantly by adding cellulose because of the poor distribution of cellulose particles throughout the matrix using the batch mixing process. Optimized mixing with improved distribution of cellulose are necessary to explore the potential reinforcing effect of cellulose, especially CNF and CNC in PA6. The SEM micrographs showed that there were no agglomerations among the cellulose particles, indicating that spray-dried cellulose materials could be suitable reinforcements in polymer-based composites.