Polypropylene-based wood-plastic composites: Effect of using a coupling agent derived from a renewable resource

Abstract

In this work, post-consumer polypropylene and wood flour from Pinus elliottii were used to produce wood plastic composites. The effect of polypropylene grafted with itaconic acid used as a coupling agent on mechanical properties, thermal stability and morphology of the composites was investigated and compared with the composite developed with polypropylene grafted with maleic anhydride, commonly used as coupling agent in wood plastic composites. Composites with 30 wt% of wood flour and 2 wt% of coupling agent were produced in a co-rotating twin-screw extruder and after were injection molded. The mechanical properties showed that flexural strength improved on 29% and 35% with addition of polypropylene grafted with itaconic acid and polypropylene grafted with maleic anhydride respectively, when compared with the wood plastic composites without coupling agent. On the other hand, the incorporation of polypropylene grafted with itaconic acid does not change the impact strength values significantly. Additionally, the temperature corresponding to 3 wt% of weight loss determined by thermogravimetry for composites with polypropylene grafted with itaconic acid increased by 14°C when compared with wood plastic composites without coupling agent, while addition of polypropylene grafted with maleic anhydride increased approximately 6°C the composite thermal stability. A morphological study revealed the positive effect of the polypropylene grafted with itaconic acid on the interfacial bonding of recycled polypropylene and wood flour.

Influence of coupling agents on rheological, thermal expansion and morphological properties of recycled poypropylene wood flour composites

“…Figure 1 shows the SEM micrographs of the fracture surfaces of the non-treated composite and the composites treated with MAPP. The fracture surface of non-treated composite in Figure 1(a) indicated the presence of pulled-out traces and bigger gaps between the wood flour and matrix, which is evidence of weak interfacial adhesion at the interface (Hong et al 2014, Poletto 2017b). The addition of MAPP promotes better compatibility between the hydrophobic matrix and hydrophilic fiber, as can be seen in Figure 1(b).…”

“…Due to such advantages lignocellulosic thermoplastic composite materials are an emerging research and development area and the object of several applications in the automotive, construction and aerospace industries (Naghmouci et al 2015, Turku et al 2017. However, the use of lignocellulosic fibers in polymeric composites presents some drawbacks such as degradation at relatively low temperatures and low compatibility between the hydrophilic character of the polar lignocellulosic filler and hydrophobic character of the non-polar polymer matrix (Khonsari et al 2015, Poletto 2017b.…”

Produção de biocompósitos de biopolietileno/farinha de madeira compatibilizados com PE-g-MA. Avaliação do teor de anidrido maleico nas propriedades mecânicas e termomecânicas

“…Comportamento do módulo elástico dos biocompósitos, em função do teor do compatibilizante. maleico do PE-g-MA com as hidroxilas da farinha de madeira, como também verificado por vários autores (Rodrigues et al, 2013;Poletto, 2017b;Wang et al, 2020). Em relação a influência do teor de PE-g-MA, o comportamento da resistência à tração é semelhante para todos os biocompósitos compatibilizados.…”

Natural oils as coupling agents in recycled polypropylene wood flour composites: Mechanical, thermal and morphological properties

“…6 Of these useful products, wood-plastic composites (WPCs) are one of the most attractive composites because they enable to use recycled plastics associated with forest and agricultural by-products. 6 -8 WPC can be used as interior or exterior building materials, furniture and automotive products.…”