Study On The Basic Properties Of Wheat Straw From Different Areas

Wheat straw was widespread throughout the world.Make full use of wheat straw as a composite material can not only solve shortage of resources,but also to avoid polluting the environment.In this paper,properties of wheat straw from four different areas(Yangzhou、Wuxi、Weinan、Qingdao)were studied in order to make wheat straw used as composite material and biomass energy effectively.The difference of physical properties、tensile properties、main chemical functional groups through FT-IR、thermal properties including TG&DSC and surface microstructure of wheat straw from different areas were compared.Andchanges of these properties above of wheat straw with different temperatures and physical and chemical treatments were explored.The main conclusions can be drawn as follows:(1)Surface wettability of wheat strawfrom different areas were different.The order of wetting angles of wheat straw from low to high was as follows:Yangzhou 83.70°,Wuxi 84.22°,Qingdao 94.30°,Weinan 95.45°.The difference of moisture absorption of wheat straw from different areas was small.The difference of other three areas was nearly none except Yangzhou.The saturation of moisture of wheat straw was reached anfter 12 hours,which from high to low was as follows:Weinan 8.85%、Wuxi 8.62%、Qingdao 8.45%、Yangzhou 7.69%.Moisture content of wheat straw in order from high to low was as follows:Weinan 9.09%,Wuxi 8.20%,Qingdao 8.19%,Yangzhou 7.62%.The 24h water absorption descending order was as follows:Yangzhou 497.60%,Wuxi 381.00%,Qingdao 288.80%,Weinan 268.60%.(2)Analysis of tensile of wheat straw from different areas showed that their maximum tension、tensile strength and elastic modulus were changed by different insternodes.And maximum tension、tensile strength and elastic modulus of wheat straw were decreased when internodes were increased.Maximum tension、tensile strength and elastic modulus of wheat straw fromWeinan were higher than the other three areas’ wheat straw.There was little difference between other three areas.From the analysis of variance,the factors including internodes and areas had a significant or extremely significant influence on the tensile properties of wheat straw.The tensile properties of wheat straw with different temperatures(80℃,110℃,14℃)treated、hydrothermal treated、2%oxalic acid treated and 2%NaOH treated were changed a lot.As temperature of treatment rised,tensile strength and elastic modulus were improved.The influence of treatments of hydrothermal,2%oxalic acid and 2%NaOH on the tensile properties of wheat straw was obvious than temperature treatment.Andthe improvement of tensile properties on wheat straw with 2%NaOH treated was the obviousest.The 2%oxalic acidtreatment was the worsest.From the analysis of variance,different treatments of temperatures(80℃,110℃,140℃)、hydrothermal、2%oxalic acid and 2%NaOH had a extremely significant influence on tensile properties of wheat straw.(3)The analysis of thermal properties of wheat straw showed that the pyrolysis process of wheat straw was divided into four stages:drying volatile stage in 30℃～100℃;heating stage in 100℃-250℃:thermal decomposition stage in 250℃-400℃;The remaining material heated stage over 400℃.Thermal properties of different areas’ wheat straw were different.TG curves of them had the same trends.But their residual masses at the end-point temperature were different.Their residual masses ratio descending were as follows:Yangzhou 43.22%,Qingdao 39.23%,Wuxi 31.62%,Weinan 29.57%.The difference of DSC curves of four areas’ wheat straw was more significant than their TG curves.The required calorific values of wheat straw from Yangzhou and Qingdao were lower than those from Weinan and Wuxi.(4)The analysis of FT-IR showed that absorption peaks of different insternodes were quite different.Absorption peaks of cellulose and ligin of wheat straw descending were as follows:the second insternodes,the third insternodes,the fourth insternodes.While the difference between the third and fourth insternodes was little.And the difference of wheat straw from different areas was great.The intensities of absorption peaks including 3430～33 80cm-1,～1640cm-1 center broadband.1505～1515cm-1,1450～1460cm-1.1370～1380cm-1,1230～1250cm-1,1150～1160Ccm-1 had obvious difference,which meant that content of hydroxy in carbohydrate,hydrogen bond and lignin of wheat strawfrom strong to weak was as follows:Wuxi,Yangzhou,Qingdao,Weinan,And 2130～2100cm-1 was absorption peak of NH3+ of amino acids,the intensity from strong to weak was Qingdao,Wuxi,Yangzhou,Weinan.Theintensity of 900～890cm-1 and 780～790cm--peaks which were behalf of hydrogen bond、carbohydrateand Si-O from strong to weak were as follows:Wuxi,Yangzhou,Weinan,Qingdao.After different treatments(hydrothermal,2%oxalic acid,2%NaOH)of wheat straw,some absorption peaks were appearence or disappearence,enhance or weak,or shift.The surface wax-silicied layer of wheat straw was removed more or less by different treatments.While the contents of cellulose,hemicellulose and ligninwere reducedso that mechanical properties and surface wettability of wheat straw were affented.The results showed that effects of acid and alkali treatmentswere more obvious,and the number of infrared absorption peak increased,the intensity of absorption peak enhanced.(5)The microstructure observation of surface and inner surface of wheat straw showed that:the difference of microstructure of four areas’ wheat straw was small.As the treated temperature(80℃,110℃,140℃)increased,the surface of the waxy layer of wheat straw were decreased even broken.And the surface of wheat straw appeared black oxydic spots after 110℃ and 140℃ treatment.The layered structure of polygon filamentous on inner surface of wheat straw were cracked and broken,and the inner wall of wheat straw was exposed gradually.Four different treatments affected both surface and inner surfaceof wheat straw and their influences descending were as follows:2%NaOH treatment,2%oxalic acid treatment,hydrothermal treatment.The effect of wheat straw with hydrothermal treatment was little.A part of waxy layer and ash on surface of wheat straw with 2%oxalic acid treatment were dissolved so that the binding of wheat straw was improved.2%NaOH treatment had a great impact on wheat straw.The wax layer on surfacewas teared and dissolved a lot,the lower epidermis tissue was exposed increasely.The silk layer structure on inner surfacewas completely broken,the inner wall of inner surface of wheat straw was clearly visible.