Investigation On The Performance And Forming Mechanism Of HDPE/Bamboo Powder Foam Composite

In this paper,a foamed wood plastic composite,taking bamboo fiber as major filler,azodicarbonamide(AC)and zinc oxide(ZnO)mixture(AC/ZnO)as foaming agent and HDPE as the polymer matrix,was prepared by a two-step molded method.A mathematical model of the growing up of the air bubble was established based on the bubbles grow up process of cell model,combined with three basic equations,polymer rheology constitutive equation,momentum equation,quality equation and gas diffusion equation.The bubble forming and processing mechanism of the HDPE/bamboo composite was analyzed,and the influence of different contents of poplar-wood flour and foaming agent on the foaming efficiency,resilience and water absorption of the HDPE/poplar-wood composites were studied,too.Through the analysis and discussion of the research,the conclusion is as follows:1.The best processing parameters for this experiment were obtained,which was the temperature of the mill roller was controlled at 140~145℃,the curing press should also be controlled,where the upper temperature should be 175℃,the lower temperature should be 170℃,and the pressure should be 13 MPa,the holding time should be 10 min.2.The adding of bamboo powder has the largest effect on the density,resilience and mechanics performance of the composite.When the filling quantity of the bamboo powder reached 30%,the density of the composite reached the lowest value of 0.039 g/cm~3,a maximum gas rate of 96.3%.The tensile strength reached the maximum value of 24.8 MPa,and the bending strength also reached the maximum value of 42.5 MPa.When the bamboo powder adding quantity is 50 wt%,the density of the non-foamed composite is 1.132 g/cm~3,but the density of the foamed composite is only 0.072 g/cm~3,which reduced about 93.7% compared with the non-foamed composite.3.From the microstructure of the composites,the content of AC/ZnO foaming agent would have the most impact on the density and the resilience of the material,which was verified by the density of the foamed composite reached the minimum of 0.047 g/cm~3 and the maximum resilience of 90.7% when the dosage of foaming agent was 15 wt %.Furthermore,the tensile property and the elongation at break of the composite also reached the minimum,which was 10.9 MPa and 96%,respectively.The bending strength and bending modulus is 11.4 MPa and 810.5 MPa,respectively.4.The addition of aluminum titanium coupling agent also has a great influence on the water absorption performance of the composite.When the coupling agent on the usage of 2 wt %,the bibulous rate of the foamed composite is 0.69%,which was much lower than the non-foamed one.And the tensile strength of the composite reached maximum value was 22.3MPa,the bending strength reached maximum value was 45.2MPa,the minimum value of the density was 0.059 g/cm~3,the resilience of the composite reached a maximum of 91.2%.5.The influence of dicumyl peroxide(DCP)as cross-linking agent on the mechanical properties and the foaming performance of the composite is also couldn’t be ignored.When the amount of DCP was 0.4%,the bending strength and the notched impact strength of the non-foamed composite were 31.9 MPa and 8.1KJ/m2,respectively.But the bending strength and the notched impact strength of the foamed composite were 29.3 MPa and 6.8KJ/m2,which were 8.2% and 16% lower than the non-foamed composites,respectively.