Study On Straw Flour/HDPE Composite Plastic Injection Molding Experiment

With the rapid development of socio-economic, plastics industry is playing an increasingly important role in the national economy. The conflict between increasing demand for plastic products and the relative shortage of oil resources becomes current difficulties faced by china and the world. Wood/Plastic composites (WPC) in recent years become new research and new ways.The paper chose wheat straw flour and high-density polyethylene (HDPE) as the main raw material to make wheat straw/polyethylene composite with the presence of additive silane as a coupling agent for improving their adhesion, adding the appropriate amount of plasticizers and lubricants to improve their liquidity, prevent the wheat straw decomposition, lower melt temperatures, reduce damage of the device and tooling as the main purpose by way of twin-screw extrusion granulation Then, the prepared aggregates were shot by means of injection molding into products.In this study, content of the wheat straw flour, silane, lubricant and plasticizer consumption made the different levels of analysis on the effect of flow, mechanical and thermal properties of wheat straw flour/HDPE composites. Obtained the optimum experimental formula:30 present of wheat straw flour,70 present of high density polyethylene,4 present of silanes,1 present of dibutyl phthalate(DBP),2 present of liquid paraffin. under this formula in injection molding, analysis of the mold temperature,injection pressure were made on the mechanical properties of composite to draw suitable injection process conditions.The following conclusions could be drawn from this study:The wheat straw powder content has an important influence on the fluidity, mechanical and thermal properties of the composites. With the increase of wheat straw flour content, the fluidity, tensile and impact strength of composites decreased, but weightlessness rate of composites increased in 170℃-450℃range. its fluidity decrease margin get smaller and smaller, tensile and impact strength of composites decreased respectively by almost 6.8MPa,0.54KJ/m2 in 0%-10% range.Silane content has a significant influence on flow, mechanical and thermal properties of composites. With the increase of silane dosage, its liquidity reached a turning point in silane dosage 4%,4% ago the melt index reduce subsequently rise. On the contrary, tensile and flexural strength first increased then decreased, when silane dosage was 4%, the melt index was higher. Impact strength increased with the increase of silane dosage. TGA showed coupling agent can slow composites decomposition rate.Lubricants and plasticizers were only made the experimental analysis of the flow properties of composites, the result showed that the fluidity could be improve with the increase of their content.30 present of wheat straw powder/HDPE composites optimal process parameters:maximum temperature 170℃, screw injection pressure 65%(60MPa), mold temperature 60℃. In this condition, tensile strength, flexural strength, tensile modulus, flexural modulus of samples were respectively 21.49 MPa,40.56 MPa, 1004.80 MPa,1838.55 MPa.