Studies On Preparation,Properties And Hot Water Aging Of Ramie/Poly Lactic Acid Composites

Natural plant fiber are widely applied in industry due to its advantages of low cost, light weight, high specific strength and high specific stiffness, especially it is a kind of renewable resources and can be degraded naturally.Therefore,developing the environmentally friendly and biodegradable green composites whose reinforcing material is the low-cost natural plant fiber and the matrix is biodegradable resin,has become a powerful alternative to glass fiber reinforced composite materials.In this paper,the interfacial properties,process optimization and hot water aging properties of ramie fiber reinforced poly lactic acid composite were fully analyzed and studied.Firstly, two types of different surface treatment methods, water treatment and different concentrations of alkali treatment, were applied on ramie fibers for investigating the effect of different treatment methods on the surface properties of ramie fiber.The characterization of ramie fiber before and after treatment, including the observation of surface morphology, infrared spectrum, crystallinity and tensile strength of single fiber were tested.The results showed that both the water treatment and alkali treatment had removed part of the fiber surface impurities.These treatment had a certain impact on the surface morphology and properties.After treatment with water or 5% NaOH solution, the ramie fiber was smooth and most of the impurities were removed.While using 10% NaOH,a part of the surface of ramie fiber was smooth.And a part of the surface is rough with a residual surface layer.According to the XRD test, the crystal structure of ramie fiber was changed.Besides the tensile strength of ramie fiber was significantly enhanced after the surface treatment. The tensile strength of fiber treated by water treatment increased by52% compared with that of untreated. And the tensile strength of 5%Na OH and 10%NaOH treated fiber was respectively increased by 30% and 19%.Secondly,in this paper, the interfacial bonding properties of ramie /PLA composite were evaluated by the method of micro drop extraction and the shear-lag model.The experimental study on the hot water aging of ramie fiber /PLA composites was carried out respectively for water treatment and alkali treatment to explore the influence of interface and mechanical properties.The results showed that the IFSS of micro composite with water treatment or 5%NaOH treatment increased significantly which was respectively increased by 39% and 50%.And the interfacial shear strength(IFSS) decreased significantly after 10%NaOH solution treatment.As for the hot water aging test, in addition to 0min water aging, the interfacial bonding properties of the composites after the water treatment are all stronger than that of the 5%Na OH treated interface.This showed that the sample with water treatment which was more green and simple had better durability.Fianally, hot-pressed technology was used to prepare the sheet of ramie fiber / PLA composites from the point of view of practical application.Water treatment and cyclic loading processing method were also applied on the ramie fabric whose influence on the mechanical properties of ramie fabric reinforced poly lactic acid composites was analyzed.The results showed that after the treatment,the tensile strength of ramie fabric reinforced poly lactic acid composite was increased by 29.2%.And the tensile modulus was increased by44.8%. But the improvement of the bending strength is not significant.In conclusion, the systematic analysis and research were conducted on the micro and macro properties of these natural fiber reinforced composites. The scientific and technical problems of natural fiber composites were studied by using the representative ramie fiber and poly lactic acid resin,which provides some data and technical support for the development of natural fiber reinforced composite materials in the field of composite materials in China.