| Jute fiber reinforced PLA composites have specific advantages,such as lightweight and environmental.protection the composites also have good mechanical properties,excellent biocompatibility and processibility.So the bio-based materials are gradually replacing petroleum-based materials in automobile applications.However,the PLA/jute fiber products gradually hydrolyze and degrade in daily use,which limits their applications.The paper researched two ways to delay material degradation:one was treating PLA fibers with finishing agents in the process of melti spinning,the other way was enhancing PLA/jute composites by the way of after treatment.In the aspect of PLA fiber modification,this paper researched the influence of hydrolytic resistance agent polycarbodiimide(PCDI)’s different mass fractions(0 wt%,0.2 wt%,0.4 wt%,0.8 wt%,1.2 wt%,1.6 wt%,2.0 wt%)on PLA fiber’s hydrolystic resistance performance.The accelerated hydrolytic experiments were carried out by two methords:the 95 ℃ thermostat water bath processing,constant temperature and humidity(50 ℃,95%RH)treatment.Fiber strength tests showed that:fiber’s degradation rate in the thermostat water bath was significantly faster than that in constant temperature and humidity.Structure characterization results showed that:PCDI reacted with-COOH which came from hydrolysis.The test of fibers treated and untreated by thermostat water bath were characterized by GPC,strength of filament,DSC.The results showed that:with the increasing content of PCDI,the comprehensive performance of PLA fiber improved in the beginning and then reduced.When PCD1 content was 0.4 wt%,the molecular weight(Mn,Mw,Mz),melting point,crystallinity of the fiber increased to the largest,but mechanical properties reduced rarely.In general,the comprehensive performance is the best.After treated by thermostat water bath,Fiber’s molecular weight(Mn,Mw,Mz),strength of filament,glass transition temperature(Tg),melting temperature(Tm),crystallization temperature(Xc)were lower,which are the most obvious in pure PLA fiber’s reduction,and the molecular weight distribution(PDI)was wider.we can also see numbers of shuttle-type holes from micro-structure images.The strength of PLA fiber with 0.4 wt%PCDI content achieved the best,and the reduction of the molecular weight,glass transition temperature(Tg),crystallization temperature(Tc),melting temperature(Tm)were the smallest.What is more,there was no obvious defect in microcosmic structure.The PLA/jute fiber composites were treated with three kinds of finishing agent(Aziridine Crosslinker SaC-100,multifunction polycarbodiimide UN-557,fluoroacrylate copolymer TG-5541F),and then made it to the composite sheets by hot-pressing.The composites were characterized by Fourier-transform infrared spectrometer(FT-IR),mechanical properties(tensile strength,izord impact strength),DMA,TG and SEM after 95 ℃ thermostat water bath treated.The results indicated that:the finishing agents’ effect of hydrolysis-resistance was,SaC-100>UN-557>TG-5541F.The infrared spectrum diagram and the DMA test results showed that,SaC-100 and UN-557 reduced the number of-COOH groups to enhance the hydrolytic properties.TG-5541F,as an effecient surfactant,improved the water-resistance performance of composites.Mechanical properties,TG tests showed that SaC-100,UN-557 improved the composites’ tensile strength and impact strength,while TG-5541F had the opposite effect.All the three kinds of finishing agents have improved composites’ heat-resisting performance.After water-bath processing,the tensile impact strength of the PLA/jute composites were reduced which treated by three kinds of finishing agents.And SEM test further indicated that SaC-100 improved interface compatibility of PLA/jute composites. |
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