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林业工程学报,2020,5(3):59-65JournalofForestryEngineeringDOI:10.13360/j.issn.2096-1359.201907037栓皮栎软木动态黏弹性研究毕俊杰,王庆国,吴世谦,宋孝周∗(西北农林科技大学林学院,陕西杨凌712100)摘 要:软木是从栓皮树上采剥的树皮,是一种天然可再生的生物质材料。通过对软木的动态黏弹性进行研究,可以揭示许多关于软木材料结构和分子运动的相关信息。本试验主要运用动态力学分析技术研究了栓皮栎软木的动态黏弹性,并和国外栓皮槠软木进行了对比。结果表明:在不同测试频率条件下,再生栓皮栎软木的储能模量(E′)均随温度升高而呈现降低趋势,损耗因子(tanδ)曲线主要出现了3个明显的损耗峰,对应的3个损耗过程分别由软木脂无定形区发生玻璃化转变、软木中有关成分发生熔融和吸着水的损失、纤维素和半纤维素发生热软化或降解所引起。再生栓皮栎软木分别沿轴向、径向和弦向进行拉伸测试时,E′、损耗模量(E″)和tanδ曲线的变化趋势基本一致,但在相同测试温度下,E′和E″在3个方向存在明显差异。在本试验条件下,栓皮栎和栓皮槠软木存在不同温度的损耗峰,主要表现为初生和再生栓皮栎软木的tanδ曲线分别在-10和-19℃出现一个损耗峰,而再生栓皮槠软木对应的损耗峰出现在14℃。关键词:栓皮栎软木;动态黏弹性;储能模量;损耗模量;损耗因子中图分类号:S781.3 文献标志码:A 文章编号:2096-1359(2020)03-0059-07开放科学(资源服务)标识码(OSID):StudyondynamicviscoelasticityofcorkfromQuercusvariabilisBIJunjie,WANGQingguo,WUShiqian,SONGXiaozhou∗(CollegeofForestry,NorthwestA&FUniversity,Yangling712100,Shaanxi,China)Abstract:CorkisthebarkmainlyfromQuercusvariabilisinChinaandQuercussurberinEuropeandAfrica.Itisalsoanaturalrenewablebiomassmaterialwithmanyappreciatedproperties,suchaslightweight,lowpermeability,lowther⁃malconductivity,soundabsorption,heatinsulation,wear⁃resistanceandchemicalstability.Themaincomponentofcorkissuber,lignin,polysaccharidesandextractables.Corkiswidelyusedinmanyfields,suchascorksealingmaterial,heatinsulationlayer,buildinganddecorationmaterials.Corkwouldbeaffectedbythechangingmagnitudeanddirectionofforceinthepracticalapplication,showingtwodifferentmechanismsofdeformation,namely,elasticityandviscosity,whichbelongstotheviscoelasticityofcork.Undertheactionofthecyclicalternatingstress(strain),therearestrain(stress)hysteresisandmechanicalloss,whichisthedynamicviscoelasticityofcork.Bystudyingthedynamicviscoelasticityofcork,thechangerulesofthestoragemodulus,lossmodulusandlossfactorwithtemperaturewerees⁃tablished.Theserulescanrevealtherelevantinformationofthecorkmaterialstructureandmolecularmovement.There⁃searchresultswereofgreatsignificancetodeterminetheprocessinganduseconditionsofcorkmaterials,beingusedtoevaluatetheimpactresistance,soundabsorptionanddampingcharacteristicsofthecork.ThedynamicviscoelasticityofthecorkfromQ.variabiliswasmainlyinvestigatedbythedynamicmechanicalanalysisandcomparedwiththatofthecorkfromQ.surber.TheresultsshowedthatthestoragemodulusofthereproductioncorkfromQ.variabilisdecreasedwiththeincreaseoftemperatureunderdifferenttestfrequencies,andtherewerethreeobviouspeaksinlossfactorcurves.Thethreelossprocesseswerecausedbytheglasstransitionintheamorphouszoneofsuberin,meltingofrelatedcomponentsinthecorkandlossofadsorbedwater,andthermalsofteningordegradationofcelluloseandhemicellulose,respectively.WhenthereproductioncorkfromQ.variabiliswastestedalongtheaxial,radialandtangentialdirections,respectively,thechangetrendsofstoragemodulus,lossmodulusandlossfactorcurveswerebasicallythesame.Whileatthesametesttemperature,thestoragemodulusandlossmoduluswereobviouslydifferentinthreedirections.ThecorkfromQ.variabilisandQ.surberhadlosspeaksatdifferenttemperaturesundertheexperimentalconditionsofthisre⁃search.ThelosspeaksofthevirgincorkandreproductioncorkfromQ.variabilisappearedat-10and-19℃,respec⁃收稿日期:2019-07-22 修回日期:2019-11-08基金项目:国家自然科学基金(31470583)。作者简介:毕俊杰,男,研究方向为木材科学与技术。通信作者:宋孝周,男,教授。E⁃mail:xzhsong@163.com
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