Influence of coupling agents in the preparation of polypropylene composites reinforced with recycled fibers

The use of coupling agents based on polyolefins is an interesting strategy for the preparation of composites with marked different chemical structure between their components. That is the case of polypropylene-based composites reinforced with lignocellulose fibers. In this work a deep study of the influence of the intrinsic parameters of maleated polypropylene (MAH-PP) has been carried out in order to determine the effect of its acid number as well as molecular weight in mechanical properties of composites reinforced with low cost reinforcements, under tensile, flexural and impact stresses, flow capacity, water absorption behavior and surface morphology. The use of high functionalized MAH-PP coupling leaded to important improvements in mechanical stresses and also a lower capacity of water absorption due to the formation of thinner interfaces. In the case high molecular weight MAH-PP agents, even higher than plain polymer matrix, conducted to an interesting increase in unnotched Charpy Impact Strength attributed to a low dispersion of the coupling agent in the matrix during mixing process keeping microdomains that help to avoid crack propagation.