| Reed fiber is a kind of natural fiber,with high yield,renewable and lower planting cost.However,the processing of cellulose is restricted by its limited solubility in common solvents and its inability to melt because of its numerous intermolecular and intramolecular hydrogen bonding.In recent years,increasing attention has been paid on the ionic liquids as the green solvents of natural cellulose.This has been not only providing a new and versatile platform for reed fiber homogeneous modification,but also expanding the scope of application of reed fiber in the wood-fiber plastics composites.This dissertation is set out from synthesis of ionic liquids,the work of this thesis is mainly concentrated on the following issues:(1)The ionic liquid 1-ethenyl-3-hydroxyethyl imidazolium chloride was direct synthetized using N-ethenyl imidazol and 2-chlorthanol by one-step,and which chemical structure was characterized by FTIR and 1H-NMR.It was shown that the side chain of the ionic liquids containing both double bond and hydroxyl group.(2)The chemical structure,change of crystallinity,thermostability and microstructure of the regenerated reed fiber were analyzed by FTIR,XRD,TGA and SEM technology respectively.The results showed that reed fiber in the ionic liquid could be directly dissolved without derivatization.The crystal structure of microcrystal linecellulose was transformed from cellulose type-Ⅰ to cellulose type-Ⅱ after the process of its dissolution and regeneration in the ionic liquid.Compared with native reed fiber,the regenerated cellulose has a worse onset temperature and much more residues of the thermal decomposition.Regenerated cellulose interface fuzzy loose structure.(3)Homogeneous graft modification of reed fiber with maleic anhydride using the ionic liquid as reaction medium.From the FTIR spectra of graft modified product,the strong absorption peak at 1722cm-1 are observed,which provides the evidence of graft modification without any catalyst.(4)Adopting the acetyl chloride as the esterifying agent,the homogeneous esterification modification of reed fiber was carried out in an ionic liquid 1-ethenyl-3-hydroxyethyl imidazolium chloride synthetized by ourselves.The C=O stretching vibration nearby 1734 cm-1 in the FTIR spectrum was observed and the atoms ratio of carbon to oxygen increased from 1.20 to 1.78 was measured by elemental analysis,which proved that the homogeneous esterification modification of reed fiber was successful.The polarity of the reed fiber reduced was proved by contact angle increased from 35.6 ° to 68.5 °.The results of XRD also indicated that the hydrogen bond and the crystallinity of the regenerated cellulose were distinctly decreased from 50.17%to 35.47%.The influence of the amount of esterifying agent,reaction time and reaction temperature on degree of esterification were investigated.It was found that the best conditions as follow:the molar ratio of acetyl chloride to cellulose anhydroglucose unit was 5:1,the reaction time was 2h and the reaction temperature was 80 ℃.(5)With reed fiber untreated and modified by silane coupling agent A-151,KH550,titanate coupling agent NDZ-101 as reinforcement respectively,with high density polyethylene(HDPE)and low density polyethylene(LDPE)blend as matrix,reed fiber/polyethylene(PE)composites were prepared.The effects of different modifiers and different treatment conditions on the mechanical properties,the processing performance and microstructure of the composites were studied.The results showed that when the blend rate of HDPE and LDPE is 30:70,the dosage of reed was 30 phr,the comprehensive performance of the composites is best.Compared to that without pretreatment,the impact strength,tensile strength and bending strength of reed fiber/PE composites processed by silane coupling agent A-151 increased by 29.3%,33.1%and 33.1%,respectively.Bibulous rate reduced by 47.5%and processing liquidity has also improved,and there is no adverse effect on the thermal performance.(6)PE/graft modified reed fiber(P/GR)and PE/esterified reed fiber(P/ER)composites were prepared.The effects homogeneous modification on the mechanical properties,the processing performance and microstructure of composites were studied.The results showed that compared to P/R,the impact strength of the composites added esterified reed fiber increased by 36.6%and 61.0%.There is no bad effect on tensile strengh,bending strengh and elasticity modulus.As the same time,the melt flowing rate of the composites contained homogeneous modified reed fiber raised by 8.6%and 31.4%respectively,which produced positive effects on the processing flow performance.As we can see from SEM,homogeneous modification can promote the reed fiber to disperse in PE matrix,which is beneficial to improve the interfacial bonding between the reed fiber and matrix. |
