| Wood plastic composite (WPC) is manufactured by extrusion forming technology to molding, plate or other products and it is modified thermoplastic material which is filled with plant fiber or wood fibers. It has both cost and performance advantages of wood and plastic, such as low price, reusable, biodegradable, rich wood fiber resources etc, it can replace wood and plastic in some applications. Howover, due to the polarity, easy bibulous straw powder and non-polar hydrophobic PVC matrix compatibility is poorer, straw powder/PVC composite materials’ tensile, bending and impact strength is poorer, and after filling the straw stalk powder, the density of the material also increased, which limits the application of straw powder/PVC composite material.This paper uses a variety of physical methods and chemical methods to modified straw powder, and improved the mechanical properties of the composite material.In this paper, with polyvinyl chloride (PVC) as matrix, straw powder as filler, after modified by silane coupling agent KH550, CPE and ACR modification agent, filler was prepared by using the method of hot-pressing molding different content requirement of PVC based wood plastic composite material. First studied the fill amounts of straw powder on the mechanical properties of composite material, found that the with straw powder filling volume increase in the PVC matrix, due to the low density of shraw powder, the volume occupied by the packing ratio increase, at the same time straw fiber’s dispersion become weak, granular pile, it not only provides more concentration, but also seriously influence on the main stress part of the continuity of the PVC matrix, so that the composite materials tensile strength, impact strength and bending strength decreased significantly, when the straw powder filling quantity is 35%, the tensile, impact and flexural strength were 14.36 MPa and 31.26 MPa and 8.82 KJ/m2, relative to the straw powder filling quantity is only 15% was reduced by 33.58%,14.59% and 41.74%. When the straw powder filling quantity is 45%, the hardness of materials was reduced by 32.22%, but the bibulous rate of composite materials and thermal conductivity ascent 9 times and 5.72% respectively. Considering the wood-plastics material economy, when straw powder filling quantity is 35%, the comprehensive performance is good.With containing amino silane coupling agent KH55O to deal with straw powder can effectively enhance composite materials’ tensile strength, bending strength and hardness, when KH550 content is 5%, relative to the KH550 quantity is only 1%, stretching and bending strength of the composite materials increased by 78.54% and 175% respectively, the hardness is 101.33 HR, increased by 35.7%. However the impact strength of composites, water absorption and thermal conductivity decreased, when KH550 content is 5%, relative to the KH550 quantity is only 1%, the impact strength decreased by 18.39%, water absorption and thermal conductivity decreased by 48.87% and 3.34% respectively. After Silane coupling agent processing of straw powder, the section of the two phase interface become blurred, under high magnification can be found that the straw powder with the PVC stick around, this showed that straw powder has been treated with silane coupling agent, good compatibility with PVC matrix, two phase bonding force significantly enhanced, so the compound material mechanics performance has been enhanced.after Modifier ACR processing straw powder, wood plastic composite performance can be improved, along with the increase of the dosage of modifier ACR, composites’ tensile, bending and impact strength showed a trend of falling after rising first, and when the dosage of modifier ACR is about 6% reaches maximum value. The hardness of composites is still showed a trend of falling after rising first, and when the dosage of modifier ACR is about 6% reaches maximum value. Composites’ material bibulous rate is a trend of rising after falling, and when the dosage of modifier ACR is about 4% reaches minimum value. The coefficient of thermal conductivity of composites is also showed a trend of falling after rising first, and when the ACR content is 6% reaches minimum value. While ACR content was 6%, composite materials’tensile, bending and impact strength increased by 61.65%,61.65% and 2.6 times respectively than the unmodified. Composite materials’ hardness increased by 25.42%, while water absorption and thermal conductivity decreased by 10.40% and 18.16% respectively. When the modifier ACR is 4%, the cross section of roughness reaches minimum, phase boundary is fuzzy, the composite material has good compatibility.There are certain influences on the tensile strength, bending strength and hardness of composite materials after modifier CPE join the composite system, when CPE content less to 2%, the tensile strength of the composites increased by 103.17% than the unmodified, bending strength increased 94.28%, the hardness increased by 26.11%, but it has weakened the water absorption performance and thermal conductive performance of composite materials, bibulous rate is lower than the unmodified by 20.63%, and coefficient of thermal conductivity decreased by 21.64%. With the increase of content of CPE, it improve the impact strength of composites particularly, when the content of CPE is 6%, the impact strength of composites increased 1.5 times than the unmodified, other properties show the trend of fluctuations. When CPE content is less than 6%, with the increase of content of CPE, composites’ interface cavity from the scattered distribution gradually transition to the uniform distribution, and hole has decreased, straw powder had no obvious reunion, dispersed more evenly. Got a lot of improve of the interfacial compatibility of composite materials. To sum up, when the CPE content is 2%, stretching, bending strength and hardness of the composite materials perform great, when the content of CPE is 6% composite material has good impact strength. |
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