讲义课件案例dkch23

Naturalrubberadhesivescanbeclassifiedintotwopripaltypes:latexadhesivesandsolutionadhesives.NaturalrubberlatexisobtainedbytapthetreeHaveabrasiliensis.Thelatexconsistsofabout35%solids.Ammoniaisaddedtothelateximmediayafterthetaptopreventbacterialattackandcoagulation.Beforemarketing,thelatexisconcentratedtoatotalsolidscontentofabout60to70%.Solutionadhesiveisobtainedfromsolidrubberobtainedbycoagulationoflatexasacquiredfromthetree.Thecoagulationiseffectedbydiluteaqueoussolutionoforganicacids.Thesolidrubbercanbegradedintermsofdirtcontent,ashcontent,nitrogencontent,andvolatilematter.ItcsobecategorizedbysticityretentionindexandMooneyviscosity.Tomaintainuniformityitisnecessarytochoosesolituralrubberofknown.LATEXLatexadhesivesaremadefromnaturalrubberlatexbyaddingstabilizers,wettingagents,andothercomponents.Theyareappliedtothesubstratebybrush,spray,doctorknife,orreverserollcoater.Theadhesiveisdriedtofilmnearroomtemperature.Theadhesivestrengthcanbeimprovedbyvulcanizingthesystem.Theapplicationsoflatexadhesivesaretoporoussubstancessuchaspaper,leather,andtextiles.Latexadhesivescanbehandledeasilybecausetheyaremorefluidduetolowersolidcontent.Theyhavelittleendiaryriskbecauseoftheabsenceofsolvent.Theyarecheaperbecausetheydonotcontainsolvent,whichislostondrying.However,naturalrubbersolutionadhesivespossessintrinsicallygreateradhesiontothesubstratethandolatexadhesives.Followingaresomeexamplesofnonvulcanizingnaturalrubberlatex.Self-sealenvelopePartsbyweight Naturalrubber Potassiumhydroxide Aqueousdispersionof LeatherPartsbyWeight60%Naturalrubber 20% etraceticacid 59%Aqueousdispersionpoly(2,2,4-trimethyl-1,2-dihydroquinoline) General-purposepuregumPartsbyweight60%Naturalrubber 50%Dispersionof 10%Solutionofammonium Adhesivesforthecarpetindustry.Formulationsforbackingcarpetsofhessianandpolypropylenestapleconstructionaregivenbelow.Partsbydry Naturalrubber [sodiumlaurylethersulfate Aqueousdispersionof AqueousdispersionofN-N0-cyclohexylp- Togive75% Dispersionofpolyacrylate

Ingredientsaretobemixedintheordergivenabove.Thestabilizer,thiourea,water,andantioxidantmustbecompleydispersedinthemixbeforeaddingthewhiting.Thewhitingmustbecompleydispersedinthemixbeforeaddingthickeners.TirecordPartsbyweight60%Naturalrubber 40%Vinylpyridine Resorcinol–formaldehyderesin Sodium Formaldehyde for6hat25 SOLUTIONSolutionadhesivesconsistofsolidrubberdissolvedinasolventsuchastoluene,naphtha,ortrichloroethane.Thesolventusedwilldependonthedryingandflbilityconsid-erationsintheapplication.Milledrawrubbercanbeshreddedandagitatedinthesolventuntilaclearsolutionisobtained.Othercomponentsareaddedatthisstageandmixeduniformly.Alternatively,thesolidrubbercanbecompoundedwithothercomponentsandthemixdissolvedinthesolvent.Solutionadhesivesareappliedat10–25%totalsolidscontentbyspray,doctorknife,reverserollcoater,roller,orbyspatulaortrowel.Theadhesiveisdriedatroomtempera-tureorinairovens,carebeingtakentoeliminatethefireandhealthhazardsassociatedwithsomesolvents.Thetoughnessanddurabilityofthebondmaybeimprovedbyusingvulcanizablerubbersolutionadhesives.Thesearenormallydastwocomponentswhicharemixedpriortouse.ComponentAispreparedasfollows:PartsbyNatural 1ComponentBispreparedasfollows:To100partsofcomponentA,add4partsofa10%solutionofadithiocarbamateaccelerator.Themixedadhesivewillvulcanizeatroomtemperatureoratahighertemperature,ifrequired.Typicalvulcanizingtimeatroomtemperatureis3–4days.Solituralrubberiswidelyusedinadhesiveformulationsformakingelectricalinsula-tiontapes,packagingtapes,andsurgicaltapesandsters.Thebackingmaybemadefrompapercrepe,cloth,orsyntheticmaterials,dependingontheapplication.Therubbercanbeappliedfromsolventsorcalendereddirectlyontothebacking.Thefollowingformulationsareforpackagingtapeandsurgicaltapeadhesives:PartsbyPackingSurgicalNaturalEstergumLanolin(wool11 Solvent(toluene,naphtha,orInitialshreddingorgranulationoftherubberaidsdissolving.Alternatively,lightlymilltherubberandzoxide,thenaddsolvent.BlendtheswollenmixtureinaZ-blademixeruntilhomogeneous,thenaddestergum,antioxidant,andfinally,lanolin.TheauthoracknowledgespermissionoftheRubberResearchInstituteofMalaysia,KualaLumpur,tocitetheinformationonadhesiveformulations.NRTechnologyRubberDevelopmentsSupplement,No.2,NaturalRubberProducers’ResearchAssociation,Brickendonbury,UK,1970.NRTechnologyRubberDevelopmentsSupplement,No.4,NaturalRubberProducers’ResearchAssociation,Brickendonbury,UK,1972.天然橡胶粘合剂SadhanK.De印度理工学院，印度I.简介天然橡胶粘合剂可分为被浓缩至总固体含量约60%至70%。16710116720160%天然胶乳16750%