Investigating Mechanical Performance and Water Absorption Behavior of Organo-nanoclay Modified Biofiber Plastic Composites

Hydrophobic Surface modification of biofibers to reduce water/moisture absorption of the biofiber or biofiber-plastic composites has attracted many researchers. In order to reduce the moisture sensitivity of kraft and mechanical pulp fibers, organo-nanoclay particles were adsorbed on the biofiber surfaces. Surface hydrophobicity, in terms of moisture absorption, water uptake, water contact angle and surface energy of the modified fibers were tested. The treated fibers had nano-scale surface roughness and substantially lower surface energy. The thermal stability of the mechanical pulp fibers increased after the nanoclay modification. The organo-nanoclay treated kraft and mechanical pulp fibers were used to make biofiber reinforced high density polyethylene (HDPE) composites. The organo-nanoclay treated kraft fibers had a more uniform dispersion in the HDPE matrix and the resulting composites had a higher Young’s modulus and thermal stability. Similar trend was observed for the mechanical pulp fiber-HDPE composites. The adhesion between the kraft fibers and matrix was greatly improved after adding maleic anhydride polyethylene (MAPE) as a compatibilizer, therefore, improvements in tensile strength, Young’s modulus, and thermal stability of both treated and untreated fiber composites were observed. However, this improvement was more significant for the composites containing the treated fibers. In addition, water absorption was decreased by incorporating the organo-nanoclay treated mechanical pulp fibers in the HDPE composites. The treated kraft fiber-HDPE-MAPE composites also showed a decrease in water absorption. The crystallization behaviors of the organo-nanoclay treated and untreated kraft fiber-HDPE composites with and without MAPE compatibilizer were studied. It was found by differential scanning calorimetry (DSC) analysis that both organo-nanoclay treated and untreated kraft fibers could act as nucleating agents. All composites crystallized much faster than the neat HDPE, while their crystallinity levels were lower. The organo-nanoclay treatment of the kraft fibers increased the nucleation rate. However, both the crystallinity level and the nucleation rate of the treated kraft fiber composites were increased by the addition of the MAPE compatibilizer. X-ray diffraction (XRD) analysis reveled that MAPE could also increase the d-spacing of the organo-nanoclay layers in the composites. When the fiber loading was 40 wt% in the composites, exfoliation of the nanoclays in the composites was observed.Ph