Investigation on the tensile properties and dimensional stability of polypropylene/wheat straw fiber/paper mill sludge composites

In this investigation, tensile and physical properties of polypropylene (as matrix)/wheat straw fiber/paper mill sludge (as filler) composites was studied. For this aim, ratio of wheat straw fiber/ paper mill sludge include (40/0, 30/10, 20/20, 10/30 and 0/40) were used in composite. Also, for better compatibility between the two phases3% of grafted MA as coupling agent was used. Mixing process was done in internal mixer, and then composite samples manufactured by injection molding. Result indicated that the tensile modulus of elasticity improved with increase of two fillers and also observed that the toughness of composite increased when compared to the pure PP, while the highest tensile modulus of elasticity related to the higher percentage of paper mill sludge. Tensile strength of composite decreased with adding of 40% wheat straw fiber, but with addition of sludge tensile strength increased significantly. With addition of straw wheat in PP matrix and its hydrophilic properties highest rates of water absorption and thickness swelling was observed. While with adding of sludge and less amount of Lignocellulosic materials, water absorption and thickness swelling were noticeably decrease with addition of binder and better connection with two phases.