Preparation And Properties Of Jute Fiber/polylactic Acid Composites For Automotive Interior

Jute fiber reinforced polylactic acid composites are expected to gradually replace petroleumbased materials and are widely used in automotive interiors because of its light weight,environmental protection,excellent biocompatibility and easy molding.However,the jute fiber reinforced polylactic acid composites are easily hydrolyzed,which has become one of the problems that limit its application.In this paper,a series of research work was carried out on the jute fiber reinforced polylactic acid composite panel used for the automotive interior materials,and the main conclusions are as follows.Surface modification of jute fiber by alkali solution,silane coupling agent KH-550 and the combination of the two methods was performed.The surface structure of the modified jute fiber was studied by means of Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM),thermogravimetric analysis(TGA)etc..And then the jute fiber/polylactic acid composites were prepared by melt blending.The effects of surface modification of jute fiber on the interfacial properties and mechanical properties of the composites were studied.The results showed that different surface treatment methods could improve the surface structure of jute fiber and improve the interfacial adhesion of jute fiber/polylactic acid composites.The alkali treatment removed hemicellulose,lignin,etc.,and the diameter decreased,while surface roughness and the crystallinity of the fiber increased,.However,the crystallinity of the jute fiber treated with silane coupling agent KH-550 decreased slightly,and the fiber diameter slightly increased.After surface modification,the impact toughness of jute fiber/polylactic acid composites was improved,but the effects on the tensile strength was different.According to the comprehensive analysis,the silane coupling agent KH-550 treatment was the most beneficial to the improvement of mechanical properties of the jute fiber reinforced polylactic acid composites.The tensile strength was 23.3% higher than that of the untreated jute fiber reinforced polylactic acid composites,and the impact strength increased by 11.6%.Jute fiber/polylactic acid composite panel with different jute fiber content was prepared by web molding using jute fiber and polylactic acid fiber as raw materials.The effects of jute fiber content on the interfacial properties,mechanical properties,thermal properties and hydrolysis resistance of composite panel were studied.Further analysis on the properties,such as density,combustion performance,24 h water absorption rate,etc.,required for automotive interior materials was carried out,which was also compared with the industrialized jute fiber/polypropylene composite panel.The results showed that the tensile strength and flexural strength of jute fiber/polylactic acid composite panel increased first and then decreased with the increase of jute fiber content,while the notched impact strength increased continuously.The heat distortion temperature and the crystallinity of the polylactic acid matrix gradually decreased with increasing the content of jute fiber.When the jute fiber content was 50 wt%,the jute fiber/polylactic acid composite panel had relatively excellent mechanical properties.The hydrolysis tests under different environments revealed that the jute fiber/polylactic acid composite panel had the highest degree of hydrolysis under alkaline environment compared with neutral and acidic environment,and the composite panel with the jute fiber content of 40 wt% had better hydrolysis resistance under different hydrolysis environments.Compared with the commercial jute fiber/PP composite panel,the composite panel based on polylactic acid had higher tensile properties and combustion properties,and its density and 24 h water absorption rate met the requirements of automotive interior materials.Anti-hydrolysis PLA fiber was prepared by masterbatch spinning method with polycarbodiimide(PCDI)as anti-hydrolysis agent,and its structure and properties were studied.Furthermore,the anti-hydrolysis modified jute fiber/polylactic acid composite panel was prepared by the method of web molding.The mechanical properties and hydrolysis resistance of the composite panel were studied and compared with the unmodified composite panel.The results showed that the polylactic acid fiber modified by PCDI had good hydrolysis resistance.After accelerated hydrolysis for 30 h in a constant temperature water bath at 95 °C,the surface of the unmodified polylactic acid fiber was obviously depressed,while the molecular weight decreased and the molecular weight distribution became wider.The cold crystallization peak and the melting endothermic peak of the polylactic acid gradually moved toward the low temperature direction as the hydrolysis time extended,and the melting endothermic peak became narrow.The surface of the hydrolysis-resistant polylactic acid fiber kept smooth and flat,and the molecular weight has no obvious change.Compared with the unmodified polylactic acid fiber,the monofilament strength retention rate was improved.The mechanical properties tests for the anti-hydrolysis modified jute fiber/polylactic acid composite panel showed that the tensile strength and notched impact strength were maintained or slightly decreased compared with the unmodified composite panel at the same jute fiber content,but the bending strength dropped significantly.The modified jute fiber/polylactic acid composite panel had better hydrolysis resistance.When the content of jute fiber was 40 wt%,the mass loss rate after hydrolysis for 150 hours in an alkaline environment reduced by 18.7%,and the strength retention rate increased by 33.8%.