《热固性塑料》PPT课件

《《热固性塑料》PPT课件》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、ThermosettingplasticsThermosettingplastics(thermosets)arepolymermaterialsthatirreversiblycure.Thecuremaybedonethroughheat(generallyabove200oC),throughachemicalreaction(two-partepoxy,forexample),orirradiationsuchaselectronbeamprocessing.Mostoften,thecureprocessinvolvescross-linkingwhichstrengthenst

2、hepolymer(setting).Thermosetmaterialsareusuallyliquidormalleablepriortocuringanddesignedtobemoldedintotheirfinalform,orusedasadhesives.Othersaresolidslikethatofthemoldingcompoundusedinsemiconductorsandintegratedcircuits.ThermosettingplasticsCross-linkedmoleculesCooledHeatedsoftensPermanentlyhardTh

3、ermosettingmeanstheplasticsoftenswheninitiallyheated,butsetspermanentlyrigidonceithascooledorhasbeenchemicallycrosslinked.Itissimilartotherelationshipbetweenarawandacookedegg.PreparationStrategyofthermosets+MultifunctionalmonomertocrosslinkedpolymerMelamineresinPolyesterresinPrepolymertocrosslinke

4、dpolymerPhenolicresinUrearesinPhenolicresin酚醛树脂Dr.LeoBaekelandFirsttotallysyntheticplastic(1907)Patentedin1909Bycontrollingthepressureandtemperatureappliedtophenolandformaldehyde,hefoundhecouldproducehisdreamed-ofhardmoldableplastic:bakeliteReplacedrubberforinsulationinelectricsDr.LeoH.BaekelandIn

5、1872，thefamousGermanychemist,AdolfvonBayerhadalreadyobservedtheresidueatthebottomofthetesttubeusingforthereactionofPhenolandformaldehyde,whichwasveryhardtogetridof.However,hisinterestingwasfocusedontheorganicdye,hedidn’tresearchthisreaction在酸性介质中，酚与醛的反应过程如下：式中的n一般为4～12，其数值的大小与反应物中苯酚的过量程度有关。固化时，利用树

6、脂中酚基上未反应的对位活泼氢与甲醛或六甲基四胺作用，形成不溶不熔的热固性酚醛树脂。OHOH＋CH2O－CH2OHOH－CH2－OHOHH2O－CH2OHOH－CH2－OHOH－CH2－OHnn二羟二苯基甲烷热塑性酚醛树脂热固性酚醛树脂的聚合原理热固性酚醛树脂的合成是苯酚与甲醛在碱性介质中缩聚而得。其中甲醛稍微过量，一般一般酚与甲醛的物质的量的比为6∶7。反应的第一阶段形成各种羟基酚，第二阶段是各种羟基酚之间进行反应，第三阶段是形成网状大分子的反应：第一阶段OH＋CH2O－CH2OHOHCH2OHOH（邻羟甲基酚）（对羟甲基酚）CH2O－CH2OHOHCH2OHOH（2，6-二羟甲基酚）（2

7、，4-二羟甲基酚）CH2OHOCH2－第二阶段－CH2OH－CH2OHOHHOCH2－CH2OH（2，4，6-三羟甲基酚）－CH2OHOHCH2OHOH－CH2－OHCH2OHOH＋其它略－CH2OHOHHOCH2－CH2OHOH－CH2OH－CH2－OHHOCH2－CH2OHOH－CH2OH＋－CH2OHOHHOCH2－－CH2OHOHHOCH2－CH2OH－CH2OHOHHOCH2－CH2－CH2OHHOCH2－OH