Study On Preparation And Aging Properties Of Salix/Polylactic Acid Composite Materials

With the strong promotion of environmental protection concepts such as"green and sustainable"and"harmonious development between humans and nature"in China,environmentally friendly biomass composite materials have become a research hotspot in the field of materials science.Natural plant fiber reinforced PLA based composite materials have attracted much attention due to their excellent mechanical properties,environmental protection,biodegradability,and other advantages.This study uses polylactic acid(PLA)and willow wood powder as raw materials to prepare biodegradable biomass composite materials using a molding process.Exploring the influence of process factors on the mechanical properties of composite materials through single factor experiments;Constructing a prediction model for the main mechanical performance indicators of composite materials using response surface methodology,and optimizing the optimal preparation process of composite materials;By conducting thermal oxygen and hydrothermal aging tests,the aging laws of composite materials were studied,and the aging mechanism of composite materials was explored using scanning electron microscopy and Fourier transform infrared spectroscopy.The research results indicate that:The research results indicate that:When the hot pressing temperature is 180～190℃,the mechanical properties of the composite material show a trend of first increasing and then decreasing as the temperature increases.When the hot pressing temperature is 190℃,the mechanical properties of the composite material reach the optimal value;The mesh size of Salix is40-100 mesh,and the mechanical properties of the composite material show a decreasing trend with the increase of mesh size.When the mesh size is 40-60 mesh,the mechanical properties of the composite material reach the optimal value;With the increase of the ratio of wood powder to PLA(wood polymer ratio),the mechanical properties of the composite material show a downward trend.When the wood polymer ratio is 2:8,the mechanical properties of the composite material reach the optimal value;When the dosage of coupling agent is 0-2.5%,the mechanical properties of the composite material show an upward trend with increasing dosage.The coupling agent maleic anhydride has a better effect on improving the interface of composite materials than KH550,KH570,and titanate 201.When the appropriate amount of maleic anhydride is 2%,the mechanical properties of the composite material are optimal.2.Based on the content of Study 1,response surface optimization experiments were conducted by selecting significant process factors.Through variance analysis of the fitting models for the static bending strength,elastic modulus,and impact strength of composite materials,the significance coefficient P values(P<0.05)were 0.0121,0.0406,and 0.0281,respectively,indicating that the fitting model is significant;In addition,the fitting coefficients R~2(R~2<1)are 0.8899,0.8371,and 0.8557,respectively,indicating that the model has a good fitting performance.The optimal preparation process of Salix/PLA composite material was obtained through model optimization as follows:hot pressing temperature 188.56℃,Salix/PLA mass ratio 2:8,and addition of 1.5%maleic anhydride.The predicted values of static bending strength,elastic modulus,and impact strength of the product were 53.7364MPa,4414.69MPa,and 6.38969KJ/m2,respectively.The deviation rates of the validation test results were all less than 10%,indicating that the process conditions optimized by the response surface model are feasible.3.Using thermal oxygen aging and hydrothermal aging tests to explore the aging laws of composite materials.The results indicate that under thermal oxygen and hydrothermal aging conditions,the overall color difference value of the material increases with timeΔE*all increase,and the surface of the material fades significantly;The mass loss rate,mechanical properties,and contact angle of the material show a decreasing trend,and the decreasing trend gradually decreases with the increase of coupling dosage;During the aging process,the degradation reaction of material components destroyed the chemical bond at the material interface,changed the matrix network structure,and cracks occurred on the surface.The higher the temperature,the more obvious the change.