Fabrication And Properties Of Vinylester Rresin Composite Reinforced By Jute Fiber Needled Mat

With the extension of the theme of sustainable development,natural fiber-reinforced composites step into the new areas of high-tech research for its low-cost,environmentally friendly and high mechanical properties of materials, therefore,they can be comparable with the FRP in the automobile industry, architecture and so on.Jute fibers which are one kind of the bast fibers,high specific strength and modulus in natural fibers will be widely applied as reinforcement materials of the composite.Vinylester resin which is a new kind of low-viscosity thermoset resin is polymerized by the epoxy resin and the unsaturated unitary carboxylic acid with double bonds,so it has the advantages both of unsaturated polyester resin and epoxy resin and been widely used abroad as the matrix of such high-performance fiber as the glass fiber,carbon fiber and etc.The composites based on the jute fiber needled mat as the reinforcement and Atlac580 vinylester resin as the matrix were fabricated by the method of the vacuum-assisted resin transfer molding,tested and analyzed the mechanical properties. In the article,jute fibers tested were pretreated by the alkali and hydrogen peroxide and three different needled mat were made of the above three types of jute fibers by the same needle punching technology:three laid times,pre-punching frequency of 550r/min,main high punching frequency of 850 r/min,and punching depth of 9mm. Furthermore,we tested the basic parameters,including the thickness,weight per 25 cm~2 and logitudinal tensile properties of the nonwoven.The testing results show that: the ratio and thickness of the needled mat were lower than that was untreated,but the longitudinal tensile strength were improved.Furthermore,the uneven coefficients of all the basic parameters reduced because of the treatment. In order to study the effect of degumming treatment on the mechanical properties of the composites,the original jute fiber needled mats were alkali scoured to obtain two different degumming mats and the composites reinforced by the above three types of jute fibers needled mats were prepared and experimented to compare their properties. The results show that the degumming teament changed the penetration rate of the vinylester resin on the jute fiber mats and the mechanical properties of composites were improved to a lot.With the pectin content reduced gradually,the tensile strength of the composites were enchanced correspondingly,but the bending strength of the composite reinforced by jute needled mat of residual glue rate of 4.51%is much higher than that of that reinforced by jute needled mat of residual glue rate of 2.78%. And the tensile modulus and bending modulus whose change is more obvious, improved when the degumming level increased.After a preliminary study we know that degumming can't solve the problems of interface compatibility between the jute fiber and the vinylester resin,effects of surface modification to jute fiber needled mat by alkali,potassium permanganate and silane coupling agent A-151 on the properties of composites were studied by mechanical properties tests,fiber surface energy test and SEM,respectively. Experimental results show that the surface rough which can increase the mechnical physic bonding power between the fiber and the matrix.The rough of jute fibers by by potassium permanganate modification is more higher than that by alkali modification. After the modificationof the coupling agent A-151,there is the cell wall bond link between the fiber and A- 151,which can provide an effective bridge-and-response that matches the functional group of vinyleaster resin,and further resulting in improved jute carpet fiber reinforced composite mechanical properties;Furthermore,the studies also show that the tensile strength and bending strength are enchanced by 51.38%and 77.46%,that is more obvious than those of alkali and potassium permanganate.In order to enhance the mechanical properties of the composites,carbon fibers are used to lay lengthways into three-storey in hydrogen peroxide jute fiber neddled dmat, and we make a comparison of the hybrid reinforced composites between the test and the theoretical value,which were predicted by establishing tensile and bending math-model.Meanwhile,the same fiber content of hydrogen peroxide treatment jute fiber reinforced composites were fabricated and analyzed about their mechanical properties.The results show that there is a certain line between the theoretical value and the actual value of the hybrid fiber reinforced composites,but there is still some deviation.Although,the use of the carbon fiber has greatly enhanced the tensile strength and tensile modulus of hybrid composite,but the bending model can't be changed a lot.