Degumming Of Apocynum Venetum And Development And Properties Of AV/Jute Reinforced Polypropylene Composites

In recent years,the energy shortage and environmental pollution are increasingly serious,the development of environmentally friendly materials has become a hot topic.Natural fiber reinforced composites(NFRC)have attracted extensive attention due to light weight,high modulus and regeneration,which have wide potential application in the aerospace,automobile,urban rail transit,etc.In this paper,Apocynum Venetum plants(AV)were boiled,and the bast of Apocynum Venetum(AV bast fiber)was obtained by manual peeling.In addition,the optimum technique parameters of chemical degumming were studied and then the physical and chemical properties of Apocynum Venetum before and after degumming were compared and analyzed.Furthermore,AV fibers and jute fibers were mixed at seven different weight ratios and carded into webs.The hot pressing process was used to make pure polypropylene films(PP).Herein,Apocynum Venetum/Jute hybrid fiber reinforced polypropylene composites with different ratios were prepared by laminating and heat molding process.The mechanical properties and sound absorption performance were tested and analyzed.The details are as follows.First,AV bast fibers were obtained and the optimum technique parameters of chemical degumming process was discussed.The results showed that AV bast fibers were obtained by manual peeling after water boiling process for 1.5h.Through the orthogonal test and range analysis,the optimum technique parameters for chemical degumming were 5wt.%NaOH concentration in the first cooking and 15 wt.%NaOH concentration with 2.5h in the second cooking.Secondly,the physical and chemical properties of Apocynum Venetum before and after degumming were characterized and analyzed.From the results of these tests,the average fineness of AV fiber was 4673.25 Nm,the residual gum rate was 5.4%.Scanning Electron Microscopy(SEM)results showed that the surfaces of AV bast fibers were covered with a layer of gum,which could protect AV fiber,but the AV fibers had a smooth surface without torsion and a certain number of nodes were observed distributed randomly.In addition,the trend of the Fourier Transform Infrared Spectroscopy(FTIR)was same,but the characteristic transmission intensity was different.From X-Ray Diffraction(XRD)results,the crystallinity index increased from 34.92% to 70.36%,representing the degumming removed most of the colloid and the degumming effect was obvious.Thirdly,the basic properties of jute fibers and the thermal properties of polypropylene(PP)were tested and the forming process and technology of composites were determined.The molding process was that AV/Jute HFRP was prepared with AV/Jute hybrid webs and PP films by the methods of lamination and molding process.The forming process included that the degradation temperatures of AV fibers and jute fibers were around 350? and 240?respectively,and the polypropylene of melting temperature was 150.01?,which determined the hot-pressing process of AV/Jute HFRP with the temperature of 200 ? and the pressure of2 MPa for 180 s.Finally,the mechanical properties(tensile and bending)and sound absorption properties of AV/Jute HFRP with seven ratios were tested,and the cross sections of the fractured composites were characterized.The results showed that the composites with 60 wt.% content of AV fibers had better tensile properties,and the composites with AV fibers content of 50 wt.% had better bending properties.At the same time,the tensile modulus of the material was calculated by using the modified formulas and compared with the measured results.It was found that they had a good agreement and showed that the effective of the modified formulas.Additionally,the sound absorption performance of composites were analyzed.In general,when the ratio of AV fibers and jute fibers was 40:60,the sound absorption performance of composites was better.And when the frequency was greater than 2500 Hz,the absorption coefficient of the composites with the AV fiber content of 80 wt.% was 5.2,which had obvious sound absorption effect.Therefore,it is necessary to choose suitable composites due to different requirements to make best use of this kind of composites.