Influence of coupling agent on post-consumption polypropylene composites reinforced with malt bagasse fibers

The aim of this work was to evaluate the influence of the use of coupling agent (CA) on the properties of thermoplastic composites produced from post-consumer polypropylene (rPP) and malt bagasse fibers (MB) of brewing industry. The CA used was maleic anhydride graft polypropylene copolymer (MAgPP). The study was carried out in two stages: in first step the best concentration of MB fibers was verified, where was varied the fiber contents between 0, 10, 20 and 30% (w/w); in the second step, the best MB concentration evaluated was used with different CA concentrations (0, 1, 3, 5 and 7% w/w). Of the three MB concentrations evaluated as reinforcing filler, the sample with a 30% (w/w) ratio presented 44% lower deformation than the others, presenting better mechanical resistance, although it also presented the highest water absorption. Thus, the 30% MB fiber content was chosen for two step, where the results showed that the PP/MB-30 composite treated with 3% (w/w) CA had a modulus of elasticity 10.3% higher than the same composite without CA, corroborating with the morphological analysis, which indicated better interfacial adhesion between composite components when CA was used. The PP/MB-30 composite treated with 1% (w/w) CA showed the highest thermal stability among all samples.