Preparation And Mechanical Properties Of Melon Vine Single Fiber Reinforced Ploylactic Acid Composites

The low cost,large-scale development and utilization of renewable energy are the common development direction of various countries in resource utilization.Plant fiber is a kind of renewable energy which is used more and more widely.Compared with synthetic fibers,plant fibers have richer resources,lower energy consumption of composite materials preparation,lower degree wear of processing equipment,and safer working environment,especially,plant fibers are renewable and biodegradable,which can realize the harmonious development of resource utilization and environmental protection.Based on this,single fiber/polylactic acid composites were prepared by lamination method with luffa and pumpkin single fiber felt and polylactic acid film.The fiber content in the composite is controlled by adjusting the number and sequence of fiber felt and film layers.And the tensile and bending mechanical properties of composites with different fiber contents were measured,then the section morphology was observed by scanning electron microscope(SEM).In the aspect of fibre modification,physical hot pressing and chemical silane coupling agent were used to improve the bond properties between single fiber and polylactic acid,respectively,and the effects of the two methods on the mechanical properties were analyzed.These two parts are the main innovation points and core contents of this thesis.The specific contents and results of the study are as follows:(1)The single fiber was extracted from the vine materials of luffa and pumpkin using optimized chemical degumming method,and the degumming process was improved to make the extraction process become higher efficiency and lower consumption,meanwhile,the tensile strength of luffa single fiber and pumpkin vine single fiber were increased by 111.8 MPa(39.9%)and 47.0 MPa(12.4%),and elastic modulus were increased by 2.02 GPa(68.9%)and 1.31 GPa(32.0%).(2)Single fiber/polylactic acid composites were prepared by lamination method with luffa and pumpkin single fiber and polylactic acid.The effect of fiber content on the tensile properties of the composites was analyzed.The experimental data show that when the content of the two fiber materials is 13 layers(38.1wt%),the tensile properties of composites are the best,The tensile strength was increased by 17.1MPa(29.1%)and 20.9MPa(35.5%),respectively,and the elastic modulus was increased by1848MPa(82.4%)and 3117.5MPa(139.0%).The interfacial properties of fiber and poly(lactic acid)acid are consistent with the tensile properties.(3)The effects of heat treatment modification and silane coupling agent modification on the tensile and flexural properties of the composites(with 38.1wt%of single fiber of melon vine)were studied.The results showed that the cross section defects of luffa single fiber/polylactic acid composites were reduced,the compatibility of two phases was enhanced,the tensile and bending properties of the composites were improved after the modification of the single fiber,besides,the heat treatment effect was better.However,The tensile and bending properties of the pumpkin single fiber/polylactic acid composites were not improved after the modification,and considering that there are many defects in the microscopic observation section,the possible reason is that the physical and chemical modification reduces the mechanical properties of the single pumpkin vine fiber.