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1、Unit3ThePlasticMoldDesignLesson6PlasticsandClassificationofPlastics3.1Lesson7ThermoplasticMoldDesign3.2Lesson8TransferandInjectionMolding3.3ReadingMaterials6CharacteristicsofFormingforPlasticMaterial3.4Unit3ThePlasticMoldDesignReadingMaterials7ThermosettingMoldDesign3.
2、5ReadingMaterials8CompressionMolding3.63.1Lesson6PlasticsandClassificationofPlasticsPlasticmeanspliableorimpressionable.Itisdefinedasthecapabilityofbeingdeformedcontinuouslyinanydirectionwithoutbreakingapart.[1]Followingthisdefinition，plasticscouldincludeglass,metals,a
3、ndwax．Thus,itisevidentthatnameplasticsismisleadingandnotexactlycorrect．Today,however,thenameplasticsisidentifiedwiththeproductswhicharederivedfromsyntheticresins.Thesyntheticresinsaremadebyvariouschemicalprocesses．Plasticsmanufacturingisofcomparativelyrecentdate.Todayp
4、lasticsarecommonlyfoundinhomes,automobiles,numerousotherproductsandmachines.Somemachineswhichutilizeelectricityrequireplasticpartswithelectricalinsulatingproperties.Plasticsareusuallyshippedtomanufacturingplantsaspelletsorpowders,andtheyaremelted(forthermoplastics)just
5、beforetheshapingprocess.Plasticsarealsoavailableassheet,plate,rod,andtubing,whichmaybeformedintoavarietyofproducts.[2]Liquidplasticsareusedespeciallyinthemakingofreinforcedplasticparts.Plasticsorpolymers,commonlycalledplastics,fallintotwobroadclasses:Thermoplasticmold
6、ingmaterials—TheseincludepolymerssuchasABSandpolycarbonateusedfortoys,consumerelectronicproducts,andmoreflexiblekitchenwareproducts.[3]Thekeyfeatureisthattheseplasticscanbeheatedtoaviscousfluid,molded,andcooledinareversible,time-andtime-againmanner.Becausethethermoplas
7、ticmaterialsarethosewhichsoftenwithheatingandsolidifyandhardenwithcooling,theycanberemeltedandcooledtimeaftertimewithoutundergoinganyappreciablechemicalchange.Thermosettingmoldingmaterials—Theseincludethemelamine-formaldehydeusedinhardplastictablewareandtheepoxyresins
8、usedforgluesandrein-forcedcastproductssuchaskayaksandtennisracketframes.Thermosettingproductsareheateduntiltheybecome
