Properties of Regenerated Cellulose Lyocell Fiber-Reinforced Composites

Properties of composites based on short regenerated cellulose lyocell fibers as a reinforcement and high-density polyethylene (HDPE) matrix were analyzed in this study. The effect of the fiber content and chemical pre-treatments (silane coupling agent, grafting of polymethyl metacrylate, PMMA) on composite mechanical and physical properties were investigated by mechanical tensile testing, water absorption test and fracture surface microstructure analysis. Mechanical tensile test indicated that fiber-reinforced composites show higher modulus than pure HDPE. In addition, silane and grafting (with PMMA) treatments of lyocell fibers resulted in a significant increase of the Young's modulus. Also, the effect of silane pre-treatment on fiber-matrix adhesion resulted in better mechanical properties when treatment was performed on lyocell fibers compared with flax fibers (used as reference fibers). Moreover, it was observed that the tensile strength of composites with a fiber content higher than 13.8% lay below the tensile strength of HDPE due to an inadequate stress transfer between fiber and matrix which was confirmed by scanning electron microscopy (SEM) analysis. Water absorption test indicated that moisture absorption decreased for chemically treated lyocell, improving the dimensional stability of the composites.