Study On The Preparation And Properties Of Rape Straw Fibre-based Composites

In recent years,people attached growing importance to decreasing forest resources, shortage of petroleum resources and increasingly serious environment pollution.In order to make fully use of abandoned biomass resources,and avoid the environmental pollution caused by burning,the new composites were prepared using plastic and plant straw instead of wood,such as rape straw.And we could seek for a reliable path of sustainable development for the comprehensive utilization of rape crops.However,compatibility between plant fibre and plastic,crystallization behavior of biomass composites and ageing problem in deposit and use would affect various performances.Taking these aspects into account,the paper investigated that compatibility improvement between rape straw flour(RSF) and high density polyethylene(HDPE) by mean of silane coupling agent(SG-Si900),and crystallization kinetics and ageing properties of RSF/HDPE composites.The main contents and conclusions are as follows:1.Fourier transform Infrared spectrum(FTIR) analysing modified rape straw flour (MRSF) showed that the crosslinking takes place in the presence of trace amounts of water and SG-Si900 groups were hydrolyzed to hydroxyl groups(-OH),which combined with hydroxyl groups of RSF and formed C-O-Si bonding.Meanwhile,some destructive hydrogen bond of RSF showed that compatibility between RSF and HDPE was improved and mechanical properties of the composites were enhanced largely.Mechanical properties of the composites were also improved by additive nano-SiO₂. and the regression equation describing dispersed process of nano-SiO₂ by ultrasonic was obtained by using the three-factors quadratic regression orthogonal rotary method: Y=0.362653-0.001513Z₁-0.009720Z₂-0.002860Z₃+0.000620Z₁Z₂-0.000155Z₁Z₃ -0.000262Z₂Z₃.The optimal ultrasonic operating conditions were also discussed:The ultrasonic temperature 59℃,ultrasonic time 25.1 min,ultrasonic frequency 32.5KHz.2.The isothermal and non-isothermal crystallization kinetics of HDPE and MRSF/HDPE composites were investigated by means of differential scanning calorimetry (DSC).A decrease in crystallization capability and rate of HDPE in the composites implied that the MRSF cannot act as a nucleating agent for the HDPE matrix and the neat HDPE and the MRSF/HDPE composites corresponds to a tridimensional growth with heterogeneous nucleation.And morphological observation(POM) did also support these results.Several theoretical models were applied to describe the process of non-isothermal crystallization.The results showed that the Avrami analysis modified by Jeziorny could describe the primary crystallization stage of the composites and failed to describe the later crystallization stage because of secondary crystallization which gave rise to non-linear dependence of curves.And a method developed by Mo could describe the non-isothermal crystallization of the composites very well.However,the Ozawa analysis did not give an adequate description.3.As the exposure time increased,the carbonyl index increased for the RSF/HDPE composites and nano-SiO₂/RSF/HDPE composites.The carbonyl index was roughly higher for the RSF/HDPE composites than for the nano-SiO₂/RSF/HDPE composites. Meanwhile,there was no significant vinyl group formation during the exposure of the RSF/HDPE and nano-SiO₂/RSF/HDPE composites through the initial 15 days.After 15 days,vinyl group formation significantly increased with UV exposure time,leveling after 75 days.At the same time,carbonyl index and vinyl index decrease with an increasing depth of composites,particularly decreasing strongly from 100 to 200μm.The crystallinity of the samples appeared to increase through 75 days of exposure,at which point they then began to decrease,resulting in a significant decrease at 120 days.The results of the foundational research opened up a reliable path for integrated utilization of abandoned resources and agricultural industrialization,and provided theory foundation and practice reference for rape straw fibre-based composites.