Study On Aging Properties Of Wood Fiber Reinforced High Density Polyethylene Composites

In this paper, iron oxide series pigments were chose as colorant, wood fiberreinforced high density polyethylene composites (WPC) with different colors wereprepared by extrusion machine, primary (without colored),annatto,claybank andcholoate.Analyzing the physical and mechanical propertises of WPC before and aftercolored.By hydrothermal aging and natural aging test, the effects of pigment andaging factor on the properties of WPC and the kinetics of the color properties werestudied.Besides,DMA,FTIR,XPS and SEM were researched to study the rule andmechanism of aging.Conclusions were shown as following:(1) Pigment dispersed well in WPC, all the WPCs got bright color, withoutspots and stripes. After colored, Modulus of Elasticity(MOE) and Modulus ofRupture(MOR) and iMPact strength decreased slightly, a slight increase in thecontact angle.(2) After70days hydrothermal aging,the water absorption characteristics ofWPC which were colored was reduced,but MOE,MOR, impact strength and theirretention rate were raised,choloate had the best protective effect, annatto andclaybank were almost the same.According to SEM,the section was more smoothedand with fewer holes.According to FTIR, no obvious chemical reaction happenedafter hydrothermal aging. DMA showed the storage modulus was raised at first,thendecreased,the peak of tanδ was increased after aging.(3) According to the kinetic analysis using the time-temperature superpositionprinciple(TTSP) method,the apparent activation energy (Ea) and coefficients ofdetermination (R2) of L*、a*、b*and△E*were：78.8kJ/mol and0.9899,76.9kJ/moland0.9866,87.8kJ/mol and0.9832,82.4kJ/mol and0.9828,all of them had highlinearity (R2>0.9823).(4) After180days natural aging under the condition of water,sunshine andwater+sunshine,the degree of color change was that primary﹥annatto﹥claybank﹥choloate.Overall,the effects of aging factor on the degree of color change andMOE,MOR were water+sunshine﹥sunshine﹥water, water+sunshine﹥water﹥sunshine respectively. MOE and MOR were protected by pigment,choloate had thebest protective effect, annatto and claybank were almost the same.DMA showed thestorage modulus was raised under the condition of sunshine,but it was decreasedunder the condition of water and water+sunshine. According to FTIR, the Carbonylabsorbance was raised after aging.According to XPS,WPC was oxidated afteraging,the content of C1and C2were decreased, C3and C4raised. According to SEM,the surface of WPC was damaged after aging, the effects of pigment and agingfactor on the degree of damage were water+sunshine﹥water﹥sunshine, primary＞choloate.(5)The change of properties of WPC after hydrothermal aging was mainlycaused by physical changes,included the swelling of matrix and fiber and the damageof interface;For natural aging, the change of properties of WPC were caused by bothphysical and chemical changes,included the damage of interface and the degradationof matrix and fiber.