The Impact Of Wood Flour Particle Size And Gradation On PVC Wood-plastic Composites Rheology And Mechanical Properties

Wood Plastics Composite (WPC) is a new material which is composed bynatural fiber and various kinds of resin materials. The WPC has the benefits ofmoisture-resistance, moth-resistance, high stability, small warping deformation,and so on. Comparing to the other WPC, polyvinyl chloride polymer (PVC) plasticcomposite material possesses lower price, higher strength, stronger wood texture,better flame retardant property. PVC wood plastic composite materials have beenwidely used in fields of building and decoration. However, since PVC wood plasticcomposite materials have the high viscosity at the high-temperature, thedecomposition can be easily happened during the melt processing. So, the lowerviscosity is required under the condition of constant temperature.In this paper, the lower viscosity has been achieved by controlling the size andgrading of wood powder. And the effect of particle size and grading of woodpowder on the mechanical properties of PVC wood composites has been studied,and the best ratio is obtained.Firstly, the particle size of wood powder has been screened. The60/100/150mesh is chosen as a basis wood powder, and the300+mesh is chosen as gradingwood powder. The9groups involving the different weight ratios are designed.Secondly, the PVC wood plastic composites are made by the mixture of woodpowder, PVC material and plasticizers. The viscosity of the sample is measuredunder the condition of185℃for8min. The results demonstrated that theviscosity decreases with the particle size of wood powders at a constanttemperature. The appropriate grading can decline the viscosity significantly andimprove the flow characteristics of the PVC wood plastic composites. When theparticle size is60mesh and the weight ratio of basic wood powder and gradingwood powder is3:7, the best flow characteristics are achieved.Finally, by using the self-designed mold, the PVC wood plastic composites ismolding in the vulcanizing machine under the condition of185℃and10MPapressure for10min. The tensile, bending and the dynamic mechanical propertiesare analyzed in detail. The results show that tensile and bending strength with100mesh wood powder is greater than that of60and150mesh wood powders. Theappropriate grading can improve the viscosity effectively and the interfacialbonding strength. And the tensile and bending strength can be enhanced. Thedynamic mechanical properties analyzed results show that storage modulus, lossmodulus and thermal deformation temperature are increased with the particle sizeof the wood powder; the loss factor is decreased with the particle size of the woodpowder; the storage modulus and loss modulus will decreased with grading wood powder of300+mesh, while the glass transition temperature remain basicallyunchanged. Consider all the above, the mechanic properties of the WPC are thebest while the particle size of the basic wood powder is100mesh and the weightratio of basic wood powder and grading wood powder is3:7.