Study On The Steam-exploded Eucalyptus Fiber With Oxidation-reduction Modification And The Performance Of Modified Materials

Plant fibers are abundant renewable biomass resources in nature.If plant fibers can be processed and molded as easily as thermoplastics and partially replace petroleum-based materials,will effectively solve the increasingly serious resource and environmental problems.However,a large amount of hydroxyl in the three components of plant fiber form intramolecular and intermolecular hydrogen bonds,especially the high crystallinity of cellulose,which make its melting temperature is higher than the thermal decomposition temperature and thermoplastic processing cannot be achieved.Therefore,it is necessary to modify plant fiber,reduce its glass transition temperature,broaden its processing temperature range,and improve its ability of heat flow deformation.Traditional modification methods will use a large amount of acid,alkali and organic solvents,not only will cause environmental pollution,but also will reduce the excellent performance of the plant fiber itself.Therefore,it is crucial to seek an environmentally friendly and efficient method to plasticize plant fibers.In this paper,eucalyptus fiber was plasticized and modified by oxidation-reduction reaction combines with steam explosion pretreatment.The influence of continuous steam explosion pretreatment on oxidation-reduction reaction,the processability and mechanical properties of materials were discussed.The continuous steam explosion pretreatment can destroy the compact structure of fiber bundles.The partial removal of intercellular lignin and the increased specific surface area greatly improve the accessibility of carbohydrate in eucalyptus fiber.Under the same oxidation conditions,the reaction efficiency of eucalyptus fiber steam-exploded four times was about 15% higher than that of untreated eucalyptus fiber with a similar specific surface area.Therefore,the eucalyptus fiber steam-exploded four times could generate more diol cellulose and diol hemicellulose of linear ether chain,which will result in lower glass transition temperature of the material,the material thus has better processing performance.The fiber bundle of eucalyptus is thoroughly separated after four times steam explosion pretreatment,its large aspect ratio makes the fibers have more joint points to form more complex interfacial bonding networks.At the same time,the oxidation reaction of eucalyptus fiber steam-exploded four times is more uniform,so the material is more homogeneous and the mechanical properties of material is thus better.To achieve maximum tensile strength as a standard,the glass transition temperature of eucalyptus fiber steamexploded four times with oxidation-reduction modification can reach 175.9 ?,and the tensile strength of the molded material can reach 25.9 MPa,and the yield is as high as 80.2% compared with plant fiber raw materials.The glass transition temperature of eucalyptus of 100 mesh with oxidation-reduction modification can reach 186.7 ?,and the tensile strength of the molded material can reach 15.54 MPa,and the yield is 83.5% compared with plant fiber raw materials.By partially removing hemicellulose,lignin or hemicellulose and lignin from eucalyptus fiber steam-exploded four times,this article has evaluated the effects of various components on the processing and mechanical properties of the materials.The results show that the modified diol cellulose and diol hemicellulose have better movement ability after partial removal of lignin,the processing performance of the material is thus better.At the same time,the existence of lignin is not conducive to the combination between fibers,the molded material with partial removal of lignin is more dense,and has better mechanical properties.To achieve maximum tensile strength as a standard,the glass transition temperature of eucalyptus fiber steamexploded four times with oxidation-reduction modification can reach 140.4 ? after partial removal of lignin,reduced 35.5 ? compared with the prior to partial removal of lignin,and the tensile strength of the molded material can reach 30.9 MPa,increased 5.02 MPa compared with the prior to partial removal of lignin.However,its yield is only 56.4% compared with plant fiber raw materials.The modified dialcohol hemicellulose has stronger chain motion ability,so partial removal of hemicellulose is not conducive to processing performance of material.However,the chemical instability,low molecular weight and amorphous properties of hemicellulose make its mechanical properties worse.When the oxidation degree is high,partial removal of hemicellulose can improve the mechanical properties of the material.To achieve maximum tensile strength as a standard,the glass transition temperature of eucalyptus fiber steam-exploded four times with oxidation-reduction modification can reach 180.8 ? after partial removal of hemicellulose,increased 4.9 ? compared with the prior to partial removal of hemicellulose,and the tensile strength of the molded material can reach 26.8 MPa,increased 0.92 MPa compared with the prior to partial removal of hemicellulose.However,its yield is only 63.2% compared with plant fiber raw materials.For eucalyptus fiber steam-exploded four times with removal of hemicellulose and lignin,to achieve maximum tensile strength as a standard,the glass transition temperature can reach 151.3 ?,increased 24.6 ? compared with the prior to partial removal of hemicellulose and lignin,the tensile strength can reach up to 31.5 MPa,increased 5.62 MPa compared with the prior to partial removal of hemicellulose and lignin.However,the yield is only 30.5% compared with plant fiber raw materials.In summary,the material prepared by oxidation-reduction reaction combines with steam explosion pretreatment has good thermoplastic processing and mechanical performance,and the preparation process is characterized by environmental protection and high efficiency.The material can be applied to packaging materials,indoor panels and other fields.The steam explosion pretreatment can improve the accessibility of carbohydrate and form a complex interfacial bonding network,so that the thermoplastic processing and mechanical performance of the modified material are better.Lignin and hemicellulose have a certain influence on the thermoplastic processing and mechanical performance of the modified material.However,removing it will greatly reduce the utilization rate of plant fiber,which will not only cause the waste of resources,but also pollute the environment and increase the cost.