Modification Research Of Polyolefin-based Wood Plastic Composites

As the global increasing shortage of timber resource, the wood plastic composite(WPC) prepared from discarded wood fiber and plastic is considered as the idealsubstitute of timber. Due to the poor compatibility of wood and plastic, it was neededto pretreat of wood powder or add additives to improve the interface bonding strengthbetween wood and plastic, thus improve its mechanical properties. Meanwhile, sincethe wood fiber and plastic are flammable materials, the flame retardant property ofcomposite need to be improved. Hence, in this paper, flour, polyolefin (polyethyleneand polypropylene), inorganic enhancer, flame retardant and other additives were usedas raw material to prepare polypropylene-based WPC, and the modification effect wasstudied.Firstly, organic vermiculite (O-VMT) or bamboo charcoal (BC) was used toreinforce polyolefin-based WPC. The experimental results showed that with theaddition of O-VMT, the water absorption of polypropylene-based WPC was decreasedwhile the tensile and flexural properties were increased, the best addition content ofO-VMT was3.0wt%; with the addition of BC, the water absorption of low-densitypolyethylene-based WPC was decreased, and the influence of water on themechanical property were decreased while the thermal stability, tensile and flexuralproperties were increased.Secondly, ammonium polyphosphate (APP), O-VMT or BC was used to improveflame retardant performance of high-density polyethylene-based WPC. Theexperimental results showed that with the addition of APP, the mechanical property ofthe composite was decreased while the flame retardant performance was increased;with the additions of APP and O-VMT, the mechanical loss of composite could beremedied, although the O-VMT and APP had no synergy flame retardant effect; withthe additions of BC and APP, or with the additions of BC, APP and O-VMT into WPC,APP and BC had synergy flame retardant effect on the composite. Moreover, BC could remedy the mechanical loss of composite caused by the addition of APP.Finally, hybrid flame retardant additives were added into the polyethylene (CPE)or a mixture of CPE and linear low-density polyethylene (LLDPE) to prepare flameretardant masterbatch. Such obtained masterbatch was added into high-densitypolyethylene-based WPC to get flame-retardant HDPE based WPC. The experimentalresults showed that the flame retardant level of composite got to V-0grade and thelimit oxygen index was34when47.5wt%CPE-based flame retardant masterbatchwas added.