Effects Of Different Pretreatment Methods On Wood Powder Modification

Nowadays,the world is short of energy resources.Also environmental pollution is serious.So researchers from all over the world turn their attention to green and environment-friendly biomass materials.Biomass resources are rich and renewable.It is easy to store and transport.Therefore,it has attracted attention from all over the world increasingly.At present,the biomass in China mainly comes from four aspects : first is the waste from agricultural waste and the processing of agricultural and forestry products;second is the excreta of people and animals;third is the living garbage in urban and rural areas;fourth is the waste of animals.Based on wood fiber from forestry and agricultural residues,we want to prepare bio-based plastics with good mechanical properties.In this study,the main research is about the mulberry branch of the agricultural and forestry wastes in biomass resources.After peeling,drying,smashing and drying,the mulberry branches were treated with three different pretreatment methods:after ball milling,the mulberry branches were processed by ultrasonic swelling in the sodium hydroxide;non-milling wood powder was pretreated in sodium hydroxide by wet milling;after ball milling,the mulberry branches were processed in dilute sulfuric acid.The samples were modified by esterification after different pretreatments.Then we add phthalic anhydride as esterifying agent,dimethyl sulfoxide as solvent and DMAP as catalyst in the sample.The sample was molded by esterification modification and the mechanical properties of the sample were tested.The main research content and the results are as follows:1.After the mulberry branches were balling milling,the wood powder was processed in sodium hydroxide with ultrasonic pretreatment.The mulberry branches were first treated by ball milling.Then the wood powder was ultrasonic swelling in sodium hydroxide with different concentrations.The swelling time is also different.After the pretreatment,the sample was esterified and the modified product was injected into injection molding.The bending strength of the sample was 43.42 MPa,the tensile strength was 26.18 MPa and the weight gain rate was up to 157.8%.The SEM diagram showed that the surface structure of the curved section was compact and smooth which can reflect the excellent mechanical properties of the spline.XRD also showed that after the pretreatment,the crystallinity of cellulose was reduced.The FI-TR showed that the internal structure of the ball milling wood powder was damaged which increased the accessibility of cellulose and the modified products had good thermal plasticity.2.Non-ball milling mulberry branches were processed in sodium hydroxide with wet grinding pretreatment.The pretreatment method combines the physical methods and chemical methods.The samples are treated through the different mass fraction of sodium hydroxide(5%,8%,10%,12%)with the different wet milling time(2h,2.5h,3h,3.5H,4h).The mechanical properties of the sample were good.The bending strength was 34.04 MPa,the tensile strengthwas 21.61 MPa and the weight gain rate was 110%.3.After the mulberry branches were balling milling,the wood powder was processed in dilute sulfuric acid.First,the mulberry branches were balling milling.The wood powder was pretreated in different mass fraction of dilute sulfuric acid(0.5%,1%,2%)which was heating and stirring at different temperatures(80?,90?,100?)and time(0.5h,1.0h,2.0h)at the same time.After pretreatment,the samples were modified by the same esterification method.Then the mechanical properties were tested by injection molding at last.In this experiment,the influence of three factors on the mechanical properties of the samples was designed by orthogonal test.The experimental results were analyzed by orthogonal test and equation analysis.The optimum condition of the experiment was that the dilute sulfuric acid with mass fraction of 0.5% heated and stirred for half hour at 80?.The injection molding was finished after the esterification modification.The results showed that the bending strength was52.67 MPa.The tensile strength was 29.97 MPa.The weight gain rate was up to 106%.The FI-TR showed that after the pretreatment,the hydrogen bond between the cellulose macromolecules was affected and the intermolecular force was weakened.The infrared spectra showed that the dilute sulfuric acid made the hydrogen bond between the intramolecular and intermolecular of cellulose weakened.It also dissolved lignin of lignocellulose and hemicellulose and broke the close relationship between the three.The SEM showed the spline bending section is compact and smooth,which confirmed the good mechanical properties of the bio based plastic from the side.