Chopped glass and recycled newspaper as reinforcement fibers in injection molded poly(lactic acid) (PLA) composites: A comparative study

Natural/bio-fibers are replacing synthetic reinforcements traditionally used for the preparation of the environmentally friendly composites. Composite materials are also replacing conventional materials in various fields due to their ease of processability. Chopped glass fiber- and recycled newspaper cellulose fiber (RNCF)- reinforced poly(lactic acid) (PLA) composites were processed using a full size twin-screw extruder and an injection molder. Additionally, a glass-reinforced polypropylene (PP) composite was compounded and molded, and compared to PLA/RNCF and PLA/glass fiber composites. The tensile and flexural moduli of RNCF- reinforced composites were significantly higher when compared to the virgin resin. The morphology, evaluated by scanning electron microscopy, indicated uniform dispersion of both fibers in the PLA matrix. The mechanical and thermo-physical properties of PLA/RNCF, PLA/glass and PP/glass fiber composite were studied and compared using dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). DMA results confirmed that the storage and loss moduli of the PLA/RNCF composites increased with respect to the pure polymer, whereas the mechanical loss factor (tan delta) decreased. The results of the TGA experiments indicated that the addition of fibers increased the thermal stability of the biocomposites compared to neat PLA. The heat defection temperature of PLA/RNCF was found to be comparable to that of the glass fiber-reinforced PLA composites. Such studies are of great interest in the development of environmentally friendly composites from biodegradable polymers.