Fabrication And Properties Of Apocynum And Ramie Fiber Reinforced Polylactic Composites

With the increasing awareness of environmental protection and rational utilization of resources, the natural fiber reinforced composites have been widely used in automobile,medical and health fields due to their light weight,low cost,superior mechanical properties and environmental protection.Apocynum fiber is known as the “king of wild fibers” with the similar advantages of good moisture absorption,permeability and mechanical properties with the ordinary fibrilias,and they also own the properties of health care,anti-bacteria and anti-ultraviolet.Regarding to Polylactic acid(PLA),it is one type of biodegradable thermoplastic resins with the main raw material of lactic acid originating from the corn and other natural materials.Though PLA has the merits of environmentally friendliness,good plasticity,and easy processing and molding,their mechanical properties are low.Therefore,the composites prepared with fibrilia reinforments can improve the overall mechanical properties,and have the advantages of environmental protection and so on.In this paper,based on the characterization of the physical and chemical properties of Apocynum fiber,the apocynum fiber mat and polylactic acid were prepared as the composites' reinforcement and matrix.The apocynum fiber / PLA composite panels were fabricated by the method of hot press molding,and the optimum processing parameters were determined.The mechanical,thermal and antibacterial properties of the composites were tested and analyzed,which were also compared with the properties of ramie fiber / PLA composites at the same time.The detailed research contents are as follows:Firstly,the basic structure and properties of apocynum fiber were tested and analyzed,which included apocynum fiber's transverse and longitudinal microstructure analysis,fiber's fineness,single fiber mechanical properties and thermal performance. The results showed that the cross section of the apocynum fiber is irregular polygon or ellipse,and had obvious vertical and transverse sections.The surface of the fiber is smooth with no crimp.Additionally,the fiber is fine and the average fineness is 3.5dtex. The average fracture strength of the single fiber is about 8.3 c N/dtex with low elongation,belonging to the low elongation and high modulus fiber.Apocynum fiber's decomposition temperature is about 270?,and the decomposition rate reached the highest value at the temperature range from 270? to 330?.Secondly,through the processing of opening,carding and needling,the apocynum fiber pre-needled felt,apocynum fiber needled felt,ramie fiber needled felt and apocynum 50/ ramie 50 fiber needled felt were prepared from apocynum and ramie fiber.Then,the above four kinds of fiber mat reinforced PLA composites were prepared by the hot pressing method, and the final molding parameters were determined with the temperature of 180?,the pressure of 3 Mpa,and the hot pressing time of 5min.Thirdly,the mechanical properties of the four kinds of fiber reinforced PLA composites were tested and analyzed.The results showed that the tensile properties of apocynum fiber needled felt reinforced composites had the highest tensile strength and modulus,and they were 15.3% and 60.1% higher than ramie fiber needled felt reinforced composites respectively.However,the pure apocynum fiber needled felt composites did not show good bending properties,and the flexural strength and flexural modulus were 21.8% and 7.6% lower than ramie fiber needled felt reinforced composites.Furthermore,the microscopic morphology of the samples was observed by the Scanning Electron Microscopy(SEM).It was found that the debonding of the apocynum fiber reinforced composites was not as good as that of the ramie composites,which was possibly due to the smooth surface of apocynum fiber.Furthermore,the thermal properties of the composites were characterized and the four kinds of fiber reinforced composites showed similar behaviors.Finally,in order to explore the antibacterial properties of the fiber reinforced composites,antibacterial circle method was applied.Three kinds of composite materials including the apocynum fiber needled felt reinforced composites,the ramie fiber needled felt reinforced composites and the apocynum 50/ ramie 50 fiber needled felt reinforced composites were tested to detect the antibacterial effects of Escherichia coli and Staphylococcus Staphylococcus aureus.The inhibitory effects of three kinds of composite materials on Escherichia coli and Staphylococcus aureus were shown follwing the descending sequence: the apocynum fiber needled felt reinforced composites,the apocynum 50/ ramie 50 fiber needled felt reinforced composites and the ramie fiber needled felt reinforced composites.The overall inhibitory effects of three kinds of composite materials on Escherichia coli were better than those of Staphylococcus aureus.