ElastomerBlendsand Composites
Principles,Characterization,Advances, andApplications
Editedby
SanjayMavinkereRangappa
SeniorResearchScientist,KingMongkut’sUniversityofTechnology NorthBangkok(KMUTNB),Bangkok,Thailand
JyotishkumarParameswaranpillai
AssociateProfessor,DepartmentofScience,FacultyofScience&Technology, AllianceUniversity,Bengaluru,Karnataka,India
SuchartSiengchin
President,KingMongkut’sUniversityofTechnology, NorthBangkok(KMUTNB),Thailand
TogayOzbakkaloglu
Professor,IngramSchoolofEngineering,TexasStateUniversity, SanMarcos,TX,UnitedStates
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Contents
Contributorsxiii
Prefacexvii
1.Introductiontoelastomers1
JyotishkumarParameswaranpillai,C.D.MidhunDominic,SanjayMavinkere Rangappa,SuchartSiengchinandTogayOzbakkaloglu
1.1Introduction1
1.2Vulcanization/cross-linkinginelastomers2
1.3Elastomericcompositesandblends2
1.4Recentdevelopmentsinelastomericblendsandcomposites3
1.5Conclusion6 Acknowledgments7 References7
2.Manufacturingmethodsofelastomerblendsandcomposites11
M.Ramesh,D.Balaji,L.RajeshkumarandV.Bhuvaneswari
2.1Introduction11
2.2Preparationtechniques13
2.3Conclusion29 References29
3.Elastomer-basedblends33
AswathyJayakumar,SabarishRadoor,JyotishkumarParameswaranpillai,E.K. Radhakrishnan,InduC.NairandSuchartSiengchin
3.1Introduction33
3.2Compatibilizationofelastomer-basedblends34
3.3Impactofnanofillersonelastomer-basedblends34
3.4Fabricationmethodsofelastomers35
3.5Processingandcharacterizationmethodsof elastomers-basedblends35
3.6Propertiesofelastomers-basedblends36
3.7Applicationsofelastomer-basedblends36
3.8Conclusion41 References41
4.Elastomer-based fillercomposites45
S.N.VasanthaKumarandP.C.Sharath
4.1Introduction45
4.2Preparationandpropertiesoffillers46
4.3Conclusionsandperspectives52 References53
5.Engineeringapplicationsofelastomerblendsandcomposites57
NagaSrilathaCheekuramelli,DattatrayaLate,S.Kiranand BaijayantimalaGarnaik
5.1Introduction57
5.2Elastomerblendsandcompositesprocessingmethods58
5.3Elastomerblendsandcompositesengineeringapplications62
5.4Conclusion76 Acknowledgments77 References77
6.Rheologyofelastomerblendsandcomposites83
MariacristinaGagliardi
6.1Introduction83
6.2Basicaspectsofrheology84
6.3Basickeyterms85
6.4Rheologicalmodels86
6.5Newtonianfluids(viscousliquids)86
6.6Non-Newtonianfluids88
6.7Conditionsaffectingtherheologicalpropertiesofmaterials89
6.8Effectoftemperature90
6.9Effectofthesystemstructureatthemicro-/nano-scale90
6.10Appliedrheologyinelastomers,blends,andcomposites thereof91
6.11Staticversusdynamicrheologicaltests92
6.12Laboratorytestsandinstrumentations96
6.13Cone-and-platerheometer97
6.14Capillaryviscometer97
6.15Mooneyviscometer97
6.16Constitutiverheologicalmodels98
6.17Uncuredrubbermelts98
6.18Elastomerblends100
6.19Elastomercomposites101
6.20Conclusions101 References102
7.Morphologicalcharacteristicsofelastomerblendsand composites103
A.V.Kiruthika Listofabbreviations103
7.1Introduction103
7.2Morphology104
7.3Effectofplantfiber-reinforcedelastomercomposites117
7.4Effectofsyntheticfiber-reinforcedelastomercomposites120
7.5Conclusions121 References122
8.Mechanicalbehaviorofelastomerblendsandcomposites127
G.RajeshkumarandS.ArvindhSeshadri
8.1Introduction127
8.2Mechanicalbehaviorofelastomerblends128
8.3SMPofelastomerblends128
8.4DMPofelastomerblends133
8.5Mechanicalbehaviorofelastomercomposites136
8.6SMPofelastomercomposites136
8.7DMPofelastomercomposites141
8.8Conclusions144 References144
9.Thermalbehaviorofelastomerblendsandcomposites149
AtulKumarMaurya,RupamGogoiandGauravManik
9.1Introduction149
9.2Thermodynamicsoftherubber rubberandrubber polymerblends150
9.3Thermalbehaviorofblends152
9.4Thermalbehaviorofelastomericcomposites161
9.5Conclusion164 References165
10.Viscoelasticbehaviorofelastomerblendsandcomposites171
RupamGogoi,GauravManikandSushantaK.Sahoo
10.1Introduction171
10.2Viscoelasticityofelastomerblends180
10.3Viscoelasticityofelastomercomposites185
10.4Conclusion190 References191
11.Spectroscopyofelastomerblendsandcomposites195
SabarishRadoor,JasilaKarayil,AmrithaBemplassery,AswathyJayakumar, JyotishkumarParameswaranpillaiandSuchartSiengchin 11.1Introduction195
11.2FT-IRandRamanspectroscopy196
11.3Fluorescencespectroscopy199
11.4NMRspectroscopy202 11.5Conclusion204 Acknowledgments204 References204
12.Wide-angleX-raydiffractionandsmall-angleX-ray scatteringstudiesofelastomerblendsandcomposites209 AngelRomo-Uribe
12.1Focus209 12.2X-raydiffraction210
12.3MethodsinX-rayscattering215
12.4Wide-angleX-raydiffraction,WAXD217
12.5Small-angleX-rayscattering(SAXS)224
12.6Applications234
12.7Synchrotronscattering237
12.8Conclusions239 References240 Furtherreading241
13.Theoreticalmodelingandsimulationofelastomerblends andnanocomposites243
JithaS.Jayan,B.D.S.Deeraj,AppukuttanSarithaandKuruvillaJoseph 13.1Introduction243
13.2Simulationsofelastomers244
13.3Modelingstudyofelastomerblendsandcomposites250
13.4Majorconcern/challenges256
13.5Conclusionandfuturescope257 References257
14.Recyclingofelastomerblendsandcomposites269
JithaS.Jayan,A.S.Sethulekshmi,GopikaVenu,B.D.S.Deeraj, AppukuttanSarithaandKuruvillaJoseph 14.1Introduction269
14.2Devulcanizationmethods271
14.3Value-addedproductsfromrevulcanizedelastomeric blendsandcomposites286
14.4Conclusion296 14.5Futureperspectives297 References297 Furtherreading304
15.Applicationsofelastomerblendsandcomposites305 SudheerKumar,SukhilaKrishnanandSmitaMohanty
15.1Introduction305
15.2Polyurethane-basedelastomerblendsandcomposites307
15.3Silicone-basedelastomerblendsandcomposites314
15.4Ethylene-propylene-dienemonomer(EPDM)-based elastomer317
15.5Otherelastomers321
15.6Conclusions324 References324
16.Propertiesofelastomer biologicalphenolicresin composites331
KushairiMohdSalleh,MarhainiMostapha,KamShengLauandSaraniZakaria
16.1Introduction331
16.2Biologicalphenolicresin334
16.3Propertiesofblendedcomposite340
16.4Conclusion346
16.5Futuretrend346 Acknowledgments347 References347
17.Advancesinstimuli-responsiveandfunctional thermoplasticelastomers353
JiaqiYanandRichardJ.Spontak
17.1Overviewofthermoplasticelastomersandtheir applications353
17.2IntroductiontomodelblockcopolymersasTPEs356
17.3PhysicalmodificationofnonpolarTPEsandtheir applications366
17.4ChemicalmodificationofnonpolarTPEsandtheir applications381
17.5Morphologicaldevelopmentandapplicationsofcharged TPEs385
17.6Concludingremarks391 Acknowledgments392 References392
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Contributors
D.Balaji DepartmentofMechanicalEngineering,KPRInstituteofEngineeringand Technology,Coimbatore,TamilNadu,India
AmrithaBemplassery DepartmentofChemistry,NationalInstituteofTechnology, Calicut,Kerala,India
V.Bhuvaneswari DepartmentofMechanicalEngineering,KPRInstituteof EngineeringandTechnology,Coimbatore,TamilNadu,India
NagaSrilathaCheekuramelli PolymerScienceandEngineeringDivision,CSIRNationalChemicalLaboratory,Pune,MH,India;AcademyofScientificandInnovative Research,ACSIRHeadquarters,CSIR-HRDCCampus,Ghaziabad,UP,India
B.D.S.Deeraj DepartmentofChemistry,IndianInstituteofSpaceScienceand Technology,Valiamala,Thiruvananthapuram,Kerala,India
MariacristinaGagliardi NEST,IstitutoNanoscienze-CNRandScuolaNormale Superiore,Pisa,Italy
BaijayantimalaGarnaik PolymerScienceandEngineeringDivision,CSIR-National ChemicalLaboratory,Pune,MH,India;AcademyofScienti ficandInnovativeResearch, ACSIRHeadquarters,CSIR-HRDCCampus,Ghaziabad,UP,India
RupamGogoi DepartmentofPolymerandProcessEngineering,IndianInstituteof TechnologyRoorkee,Saharanpur,UP,India
AswathyJayakumar SchoolofBiosciences,MahatmaGandhiUniversity, Kottayam,Kerala,India;DepartmentofMechanicalandProcessEngineering,The SirindhornInternationalThai-GermanGraduateSchoolofEngineering(TGGS),King Mongkut’sUniversityofTechnologyNorthBangkok,Bangkok,Thailand;Materialsand ProductionEngineering,TheSirindhornInternationalThai-GermanGraduateSchoolof Engineering(TGGS),KingMongkut’sUniversityofTechnologyNorthBangkok, Bangkok,Thailand
JithaS.Jayan DepartmentofChemistry,SchoolofArtsandSciences,AmritaVishwa Vidyapeetham,Amritapuri,Kollam,Kerala,India
KuruvillaJoseph DepartmentofChemistry,IndianInstituteofSpaceScienceand Technology,Valiamala,Thiruvananthapuram,Kerala,India
JasilaKarayil GovernmentWomen’sPolytechnicCollege,Calicut,Kerala,India
S.Kiran PolymerScienceandEngineeringDivision,CSIR-NationalChemical Laboratory,Pune,MH,India;AcademyofScienti ficandInnovativeResearch,ACSIR Headquarters,CSIR-HRDCCampus,Ghaziabad,UP,India
A.V.Kiruthika DepartmentofPhysics,SeethalakshmiAchiCollegeforWomen, Karaikudi,TamilNadu,India
SukhilaKrishnan SahrdayaCollegeofEngineeringandTechnology,Department ofAppliedScienceandHumanities,Kodakara,Kerala,India
SudheerKumar SchoolforAdvancedResearchinPetrochemicals(SARP), LaboratoryforAdvancedResearchinPolymericMaterials(LARPM),CentralInstituteof PetrochemicalsEngineeringandTechnology(CIPET),Bhubaneswar,Odisha,India
DattatrayaLate AcademyofScientificandInnovativeResearch,ACSIR Headquarters,CSIR-HRDCCampus,Ghaziabad,UP,India;PhysicalandMaterials ChemistryDivision,CSIR-NationalChemicalLaboratory,Pune,MH,India
KamShengLau Bioresource&BiorefineryResearchGroup,DepartmentofApplied Physics,FacultyofScienceandTechnology,UniversitiKebangsaanMalaysia,Bangi, Selangor,Malaysia
GauravManik DepartmentofPolymerandProcessEngineering,IndianInstituteof TechnologyRoorkee,Saharanpur,UP,India
AtulKumarMaurya DepartmentofPolymerandProcessEngineering,Indian InstituteofTechnologyRoorkee,Saharanpur,UP,India
SanjayMavinkereRangappa MaterialsandProductionEngineering,The SirindhornInternationalThai-GermanGraduateSchoolofEngineering(TGGS),King Mongkut’sUniversityofTechnologyNorthBangkok,Bangkok,Thailand
C.D.MidhunDominic DepartmentofChemistry,SacredHeartCollege (Autonomous),Kochi,Kerala,India
SmitaMohanty SchoolforAdvancedResearchinPetrochemicals(SARP), LaboratoryforAdvancedResearchinPolymericMaterials(LARPM),CentralInstituteof PetrochemicalsEngineeringandTechnology(CIPET),Bhubaneswar,Odisha,India
MarhainiMostapha Bioresource&BiorefineryResearchGroup,Departmentof AppliedPhysics,FacultyofScienceandTechnology,UniversitiKebangsaanMalaysia, Bangi,Selangor,Malaysia;HICOE-CentreforBiofuelsandBiochemicalResearch(CBBR), InstituteofSelf-SustainableBuilding(ISB),UniversitiTeknologiPetronas,SeriIskandar, Perak,Malaysia
InduC.Nair DepartmentofBiotechnology,SahodaranAyyappanSmarakaSree NarayanaDharmaParipalanaYogam(SASSNDPYOGAM),College,Konni, Pathanamthitta,Kerala,India
TogayOzbakkaloglu DepartmentofCivilEngineering,TexasStateUniversity,San Marcos,TX,UnitedStates
JyotishkumarParameswaranpillai DepartmentofScience,FacultyofScience& Technology,AllianceUniversity,Bengaluru,Karnataka,India
E.K.Radhakrishnan SchoolofBiosciences,MahatmaGandhiUniversity,Kottayam, Kerala,India
SabarishRadoor MaterialsandProductionEngineering,TheSirindhorn InternationalThai-GermanGraduateSchoolofEngineering(TGGS),KingMongkut’s UniversityofTechnologyNorthBangkok,Bangkok,Thailand;Departmentof MechanicalandProcessEngineering,TheSirindhornInternationalThai-German GraduateSchoolofEngineering(TGGS),KingMongkut’sUniversityofTechnology NorthBangkok,Bangkok,Thailand
G.Rajeshkumar DepartmentofMechanicalEngineering,PSGInstituteof TechnologyandAppliedResearch,Coimbatore,TN,India
L.Rajeshkumar DepartmentofMechanicalEngineering,KPRInstituteof EngineeringandTechnology,Coimbatore,TamilNadu,India
M.Ramesh DepartmentofMechanicalEngineering,KIT-Kalaignarkarunanidhi InstituteofTechnology,Coimbatore,TamilNadu,India
AngelRomo-Uribe Research&Development,AdvancedScience&Technology Division,Johnson&JohnsonVisionCareInc.,FL,Jacksonville,UnitedStates
SushantaK.Sahoo MaterialsScienceandTechnologyDivision,CSIR National InstituteforInterdisciplinaryScienceandTechnology,Thiruvananthapuram,Kerala, India
KushairiMohdSalleh Bioresource&BiorefineryResearchGroup,Departmentof AppliedPhysics,FacultyofScienceandTechnology,UniversitiKebangsaanMalaysia, Bangi,Selangor,Malaysia
AppukuttanSaritha DepartmentofChemistry,SchoolofArtsandSciences, AmritaVishwaVidyapeetham,Amritapuri,Kollam,Kerala,India
S.ArvindhSeshadri DepartmentofMechanicalEngineering,PSGInstituteof TechnologyandAppliedResearch,Coimbatore,TN,India
A.S.Sethulekshmi DepartmentofChemistry,SchoolofArtsandSciences,Amrita VishwaVidyapeetham,Amritapuri,Kollam,Kerala,India
P.C.Sharath MetallurgicalEngineeringDepartment,JainUniversity,Bangalore, Karnataka,India
SuchartSiengchin MaterialsandProductionEngineering,TheSirindhorn InternationalThai-GermanGraduateSchoolofEngineering(TGGS),KingMongkut’s UniversityofTechnologyNorthBangkok,Bangkok,Thailand;Departmentof MechanicalandProcessEngineering,TheSirindhornInternationalThai-German GraduateSchoolofEngineering(TGGS),KingMongkut’sUniversityofTechnology NorthBangkok,Bangkok,Thailand
RichardJ.Spontak DepartmentofChemical&BiomolecularEngineering,North CarolinaStateUniversity,Raleigh,NC,UnitedStates;DepartmentofMaterialsScience& Engineering,NorthCarolinaStateUniversity,Raleigh,NC,UnitedStates
S.N.VasanthaKumar MechanicalEngineeringDepartment,CanaraEngineering College,Mangalore,Karnataka,India
GopikaVenu DepartmentofChemistry,SchoolofArtsandSciences,AmritaVishwa Vidyapeetham,Amritapuri,Kollam,Kerala,India
JiaqiYan DepartmentofChemical&BiomolecularEngineering,NorthCarolina StateUniversity,Raleigh,NC,UnitedStates
SaraniZakaria Bioresource&BiorefineryResearchGroup,DepartmentofApplied Physics,FacultyofScienceandTechnology,UniversitiKebangsaanMalaysia,Bangi, Selangor,Malaysia
Preface
Elastomersarealsocalledrubbersandhavemanyspecificfeaturessuchaselasticity,good strength,andhightoughness.Someoftheexamplesofelastomersarenaturalrubber, polyurethane,ethylene propylenerubber,siliconerubbers,etc.Theperformanceofthe elastomerdependsonthecross-linkdensity,molecularweight,andtypeofelastomer.The elastomerassuchpossessespoorthermomechanicalproperties.Therefore,cross-linkingof elastomersisessentialforimprovingtheirperformance.Sulfurorno-sulfurcompoundsare usedforcross-linkingelastomers.Thecross-linkdensityorvulcanizationcanbecontrolledby changingthecross-linkingagents,varyingtheamountoffillers,etc.Generallycross-linking improvestheperformanceoftheelastomer.
Inrecentyears,blendsandcompositesofelastomersareformulatedforimproved performance.Someofthepotentialapplicationsofelastomericblendsandcompositesarein theoilandgasindustry,automobile,conveyerbelts,adhesive,andsealants,etc.Thisbook comprisesalltheimportantareasofelastomericblendsandcompositesandtheircharacteristicpropertiessuchasstructural,thermomechanical,morphology,rheology,and modeling.Therecyclingandpotentialapplicationsofelastomericblendsandcompositesare alsodiscussed.Wehopethisimportantbookwillbenefitstudents,scientists,industrialists, andthosewhoareinterestedinrubber-basedmaterials.Theeditorsthankalltheauthorsfor theircontributions.
Acknowledgments
ThisworkwassupportedbyKingMongkut’sUniversityofTechnologyNorthBangkokhas receivedfundingsupportfromtheNationalScience,ResearchandInnovationFund(NSRF) withGrantNoofKMUTNB-FF-65-19.
Editors
SanjayMavinkereRangappa(Thailand) JyotishkumarParameswaranpillai(India) SuchartSiengchin(Thailand) TogayOzbakkaloglu(USA)
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Introductiontoelastomers
JyotishkumarParameswaranpillai1,C.D.MidhunDominic2, SanjayMavinkereRangappa3,SuchartSiengchin3, TogayOzbakkaloglu4
1 DEPARTMENTOFSCIENC E,FACULTYOFSCIENCE & TECHNOLOGY,ALLIANCEUNIVERSITY, BENGALURU,KARNATAKA,INDIA; 2 DEPARTMENTOFCHEMISTRY,SACREDHEARTCOLLEGE (AUTONOMOUS),KOCHI,KERALA,INDIA; 3 MATERIALSANDPRODUCTIONENGINEERING, THESIRINDHORNINTERNATIONALTHAI-GERMANGRADUATESCHOOLOFENGINEERING (TGGS),KINGMONGKUT ’ SUNIVERSITYOFTECHNOLOGYNORTHBANGKOK,BANGKOK, THAILAND; 4 DEPARTMENTOFCIVILENGINEERING,TEXASSTATEUNIVERSITY,SANMARCOS, TX,UNITEDSTATES
1.1Introduction
Elastomersareviscoelasticpolymers,showingbothviscousandelasticproperties.The elastomerpossesseslongpolymerchainsheldtogetherwithweakintermolecularforces. Theseweakforcesmakethemflexibleandsticky,withhighelongationuponthe applicationofstress.Oncethestressisreleased,itcouldcomebacktotheoriginalshape andhencecalledelastomer.Mostofthesepolymersarehaving100%recoverability, thankstotheirlowdegreeofcross-links.Thelowdegreeofcross-linksintheelastomer makesitamorphous;however,onceitisstretched,crystallinesitescanbeobserved.The elastomerretainsitsoriginalshapebecauseofthesecross-links.Inorderwords,crosslinkingwithintheelastomerprovidesabettershapeandstiffness.Theotherfeatures ofelastomersarelowglasstransitiontemperature,hydrophobicity,goodadhesion,good breakingresistance,tearstrength,abrasionresistance,resistanttogas,water,andsteam, andareexcellentinsulators.Itfindsapplicationinadhesives,sealingapplications,and insulations[1].Elastomersareofnaturalandsyntheticorigin.Thesyntheticelastomers arepetroleum-based,whilenaturalrubbersareofplantorigin.Examplesforelastomers arenaturalrubber,EPDMrubber,siliconerubber,olefinthermoplasticelastomer,etc. Thepropertiesofapureelastomersuchaselasticity,strength,hardness,andresilience arepoor,whichrestrictsitsuseinadvancedapplications.Therefore,cross-linkingis necessary.Thepropertiesandperformanceoftheelastomercanbedramatically enhancedwithvulcanization/cross-linking[2].
1.2Vulcanization/cross-linkinginelastomers
Vulcanizationorcross-linkinginelastomerscanbeachievedbysulfur[3]andnonsulfur [4]compounds.Thecross-linkingresultsinathree-dimensionalnetworkstructure.The cross-linkingofelastomerwithsulfurisaslowprocessandmaytakealongtimefor completecuring.However,ashortercuretimeispreferred,andtheprocesscanspeedup byincludingotheringredientsalongwithsulfur.But,thecross-linkingreactionsin elastomersshouldbecontrolledfortheirusefulnessandsuccessforspecificapplications.Prematurecross-linkingresultsinpoorperformance,andtheproductsformedare notuseable.Effectivecontroloverthecross-linkingisthereforeessentialforachieving therightphysicalproperty.Thefollowingagentsareusedalongwithsulfurfortheoptimumcross-linking(i)accelerators,(ii)activators(iv)retarders,(v)prevulcanization inhibitor[5].
Theaccelerators(examples:N-t-butylbenzothiazole-2-sulfenamide,2-mercaptobenzothiazole,2,20 -dithiobisbenzothiazole,dithiocarbamates,tetramethylthiuramdisulfide, tetramethylthiurammonosulfide,etc)areusedforfastcross-linking;italsoenables thecurereactiontotakeplaceatalowertemperatureandreducedtheconsumption ofsulfur[6,7].Theactivators(zincoxide)andcoactivators(fattyacids)arewidely employedtoimprovethevulcanizationefficacyofelastomers[8].Theretarders(examples: phthalicanhydride,salicylicandbenzoicacids,andN-nitrosodiphenylamine)areused toretardthevulcanizationofelastomerwhiletheprevulcanizationinhibitor (N-cyclohexylthiophthalimide)preventsearlyvulcanization[2].Manystudieshadbeen carriedoutfortheunderstandingofthemechanismofvulcanization.Itisproposedthatin thefirststep,theZnOreactswithstearicacidformingazinc/stearatecomplex.Inthe secondstep,thezinc/stearatecomplexreactswiththeacceleratorforminganactive acceleratorcomplex.Inthethirdstep,theactiveacceleratorcomplexreactswithsulfur forminganactivesulfuratingagent.Theactivesulfuratingagentreactswithelastomer resultinginacross-linkedintermediate,followedbypolysulfidecross-links,andfinally fullyvulcanizednetwork[8].Further,theperformanceoftheelastomercanbeenhanced bytheadditionofimprovingagentssuchasantioxidants(dithiocarbamate)[9],plasticizers(oil,resins,waxes)[10,11],fillers(carbonblack,nanomaterials,etc),anddyes(TiO2, ZnO,ZnS,etc.)[12].
1.3Elastomericcompositesandblends
Inrecentyears,therehasbeenaboomintheapplicationofnanotechnologyinelastomers.Thiscausedtheresearcherstoattempttheapplicationsofdifferentnanomaterialsindifferentelastomers.Thenanoparticlessuchasgraphene,CNTs,CNF,silica, metalnanoparticles,CaCO3,cellulose,plantfibers,etc.,havebeenwidelyusedforthe modificationofelastomers[13,14].Itwasobservedthatthemechanical,thermalstability,viscoelasticproperties,flameretardancy,andbarrierpropertiescanbeimproved withthemodificationwithnanofillers.However,thepropertiesofthenanocomposites
dependonseveralfactorssuchassize,shape,l/dratio,methodofmanufacturing,and distributionofnanoparticles.Themethodsusedforthepreparationofelastomer-based compositesaresolutionmixing,latexcompounding,meltmixing,andin-situpolymerization[14].Similarly,elastomericblendsystemshavealsobeenreported.Blending isaneffectivemethodtoimproveperformance.Developinganewelastomertakestime andisnotcost-effective.However,blendingwithappropriateelastomerwillbring attractiveproperties[15].ExamplesofelastomericblendsarePP/SEBS,polyamide6 (PA6)/fluoroelastomer,naturalrubber-polypropylene(NR/PP),etc.[16 18].Blending dependsonseveralfactorssuchascompatibility,blendratio,morphology,etc.Various characterizationtechniquessuchasuniversaltestingmachine,SEM,TEM,XRD,FTIR, TGA,DSC,DMA,etc,maybeutilizedforthesuccessfulcharacterizationandevaluation oftheblendsandcomposites.Thesehigh-performanceelastomericblendsandcompositesfindapplicationsinlightweightcomposites,spaceshuttles,tireinnerliners,cable industry,shapememorypolymers,softroboticapplications,andflame-retardantapplications[19 24].
1.4Recentdevelopmentsinelastomericblendsand composites
1.4.1NR-basedelastomers
Bayatetal.[25]developedcompositefoamsbasedonnaturalrubberandsilicananoparticles.Azodicarbonamideisusedastheformingagent.One-step(140 C)andtwostepformingcycles(90and140 C)wereused,andtheresultedfoamswerecompared. Thepresenceofsilicareducedthecellsize,however,theincreasedthecellwallthickness andfoamdensity.Thecellsizeandcellwallthicknessaremoreorlessinagreementfor compositespreparedbyone-stepandtwo-stepformingcycles.However,thetwo-step processhasalowerfoamdensitycomparedtothesingle-stepprocess.Yangetal.[26] fabricatedconductingNRcompositeshaving10wt%PEDOT:PSS(organicconductor). Thecompositesshowedexcellentconductivity(87S/cm)andelongationatbreak(490%); furthermore,showedgoodtemperatureandstrainsensingproperties.Alametal.[27] reportedgoodmechanicalpropertiesforanisotropicNBR/carbonylironparticlescompositesinthepresenceofanappliedmagneticfield.TheauthorsrecommendtheNBR compositesformagnetorheologicalapplications.Lietal.[28]reviewedthemagnetorheologicalelastomersanddiscussedtheirpotentialapplicationinsensors,isolators,and absorbers.Themagnetorheologicalelastomersarehavingmanypotentialfunctionalities whencomparedwithMRfluids,suchasparticlesettling,sealingproblems,environmentalcontamination,etc.,andarepotentialcandidatesforvibrationcontrolapplications.Inarecentstudy,naturalrubberlatexwasmodifiedwithgrapheneoxideand zwitterionicchitinnanocrystalsisolatedfromcrabshellpowder[4].Thereinforcement causedanenhancementintensilestrengthandelongationatbreak.Theincreasein tensilepropertieswasduetothehydrogenbondingbetweenthenaturalrubberlatexand
zwitterionicchitinnanocrystalsandzwitterionicchitinnanocrystalsandgrapheneoxide. Thisapproachpavesanewmethodforthedevelopmentofhigh-performanceelastomericcompositeswithoutsulfurvulcanizationforadvancedapplications.
High-performancePP/NR/MWCNTscompositeswithsuperiorelongationatbreak, tensiletoughness,andimpactstrengthhadbeendeveloped[29].Itwasobservedthatthe TgoftheNRphaseincreasedbyapproximately10 CwithMWCNTsloadingduetothe selectivelocalizationofnanofillersintheNRphase.ThedielectricpropertiesofNR/ millablepolyurethanecompositeswithnonblackandblackfillersreportedimproved dielectricproperties[30].Theimprovementinpropertieswasduetothefillernetwork formedinthecomposites.Zhangetal.[31]developedanewmethodforthefabrication ofNR/CNTscompositeswithsuperiorconductivityandmechanicalproperties.The methodoffabricationofthecompositesinvolvesthefollowingsteps.Inthefirststep highlycross-linkedNRwasfirstpreparedandmadeintogranulesusingatwo-rollmill. ThesecondstepinvolvesmixingNR þ CNTmasterbatch,NRgum,NRgranules,and curingadditivesusingatwo-rollmillfollowedbythehotpressing.Theincorporationof theNRgranulescausedselectivedispersionoftheCNTsinNRcontinuousphase resultinginanincreaseintheconductivity.Also,thedisulfidesandpolysulfidespresent intheNRgranulesinteractwithNRcontinuousphaseenablingstronginterfacial adhesionresultingingoodmechanicalproperties.
1.4.2EPDM-basedelastomers
Thereuseandrecyclingofcross-linkedrubberareamajorenvironmentalproblem,and devulcanizationisoneofthegreensolutionsforit.PirityiandPoloskei[32]devulcanized sulfurcuredEPDMusingatwo-rollmillatvarioustemperatures.Itwasobservedthatat lowtemperaturesofmilling,thedegradationcanbereduced.LatertheauthorssuccessfullyreusedthedevulcanizedEPDMby(1)addinganextracuringagent,(2)mixingit withvirginrubber.TheadditionofrecycledEPDM(25and50wt%)invirginrubber showedreasonablygoodmechanicalproperties.Liuetal.[33]studiedandcomparedthe agingbehaviorofEPDMcross-linkedwithsulfurandEPDMcross-linkedwithperoxide inacidsolution(fuelcellenvironment).TheEPDMcross-linkedwithperoxideundergoeschainbreakageduringaginginacidicsolution(after10weeks)resultingin deterioratedmechanicalpropertiesafteraging.Ontheotherhand,theEPDMcrosslinkedwithsulfurwasmorestableinanacidicmedium,andnosuchmolecularbackbonebreakagewasobserved.
ThevariationsinrelaxationmodulusandcreepofEPDMatdifferenttemperatures andstrainconditionswerestudiedandmodeledusingthetime temperaturesuperpositionprinciplebyWangetal.[34].Accordingtothetime temperaturesuperposition principle,therelaxationmodulusmayreducetoca.45% 10%strain,whilecreepincreasesby191%at1MPastressafter100yearsofservice.Shafranskaetal.[35]studied theplasticizingeffectofsaturatedandunsaturatedsoybeanoilonEPDM/carbonblack composites.Itwasobservedthattheoilwiththehighestdegreeofunsaturationgivesthe
highestplasticizingeffect;however,thecross-linkdensityandmechanicalproperties werereduced.Ontheotherhand,oilwithall-saturatedfattyacidchainsshowsapoor plasticizingeffect,butthecross-linkdensityandmechanicalpropertieswerenot affected.Suetal.[36]studiedthetribologyofEPDM/carbonblackcomposites.The authorsobservedagoodimprovementintribologicalpropertiesofEPDMwiththe incorporationofcarbonblack.Salimietal.[37]observedthattheincorporationof reclaimedEPDMinvirginEPDMreducedthemechanicalandviscoelasticproperties duetothebreakageoftheEPDMchainsduringthereclaimingprocess.
1.4.3Siliconerubber
Thesiliconerubberismostlypreparedbythehydrolysisofdimethyldichlorosilane[38]. Asignificantdevelopmentinthecommercialmanufacturingofsiliconehasbeenreportedoverthelastfewdecades.Thesiloxanebondsbetweenthepolymerunitspermit flexibilityandviscoelasticity.Thesiliconerubberassuchhasverylowcross-linked networks;therefore,thereinforcementwithnanoparticlesisrecommendedtoenhance thestrength,stiffness,andotherproperties[39].Demandforflexible,thermally conductive,andinsulativematerialisgrowingespeciallyintheelectricalandelectronic industry.Siliconerubberisaflexiblepolymerwithexcellentweatherresistance.Ina recentstudy[40],Al2O3 wasgraftedwithboronnitridesheetstoformheterostructured fillerwithexcellentthermalconductivity.Theheterostructuredfilleristhenincorporated inroom-temperaturevulcanizedsiliconerubbertoimproveitsfunctionality.The compositesshowedenhancedthermomechanicalproperties,electricalinsulation property,andthermalconductivityandwereanidealcompositematerialforelectrical andelectronicapplications.Inasimilarstudy,Kumaretal.[41]modifiedroomtemperaturevulcanizedsiliconerubberwithcarbonnanotube(CNT),nanographene, andCNT-GRhybridfillers.Theincorporationoffillerimprovedthemodulusofthe compositesandactuationdisplacementintheorderCNTs > CNT-GR > GR.TheCNTs andCNT-GR-basedcompositesshowedgoodstretchabilityanddurability.Thus,these compositesareagoodchoiceforsensorsandactuators.
Thedegradationofhigh-temperaturesiliconerubbermodifiedwithnano/microsilica fillersunderlong-termenvironmentalagingconditionswasstudiedbyRashidetal.[42]. Thecompositeswith2wt.%nano/20wt.%microsilicafillersshowedthebestresistance toacceleratedenvironmentalagingconditions.Theflameretardancyofsiliconrubber foammodifiedwithexpandedgraphite(EG)andmodifiedHNTswasstudiedbyPang etal.[43].Thelimitingoxygenindex,peakheatreleaserate,smokeproductionrate,CO andCO2 production,etc.,ofsiliconrubberfoam,werereducedwiththeincorporationof expandedgraphiteandmodifiedHNTs.Thatmeanstheflameretardancyofsilicon rubberfoamcanbesignificantlyimprovedbythesynergisticeffectofexpandedgraphite andHNTs.Inrecentwork,Guoetal.[44]developedself-healingPDMSbyincorporating hydrogenanddisulfidebonds.Thepolymershowedhighstretchabilityandautonomous healingunderuniversaltemperatureconditions. Chapter1
1.4.4Olefinthermoplasticelastomer
ThermoplasticelastomerconsistsofpolyolefinthermoplasticssuchasPPandPEand olefincopolymerssuchasEPDM,SEBS,andNR.Thecontinuousthermoplasticpart providedthestrengthandmodulus,whiletheolefincopolymerpartprovidedflexibility andtoughness[45].Dynamicvulcanizationofethylene-octenecopolymer(POE)and polypropylene(PP)wascarriedoutforformulatingolefinthermoplasticelastomer[46]. Thevulcanizingagentbis(1-(tert-butylperoxy)-1-methylethyl)-benzene(BIPB)wasused. Theolefinthermoplasticelastomerwith0.6phrBIPBand60/40PP/POEcomposition showedthehighesttensilestrengthandmodulus.Further,thesiliconepowderwas introducedin60/40olefinthermoplasticelastomercontainingbromine-phosphorus flame-retardantmaterial.Theincorporationofsiliconepowder(3phr)improvedthe flowproperties,limitingoxygenindex,andagingresistance.
Kiziltasetal.[47]utilizedrecycledPPandguayulelatexforthepreparationofthermoplasticelastomer.ThePP-g-MAwasusedasthecouplingagent.Graphenenanoplatelets (2.5 10wt.%)wereusedasareinforcement.Itwasobservedthatthethermalandmechanicalpropertiesofthermoplasticelastomerimprovedwiththeincorporationofgraphenenanoplatelets;10wt%offillergivesthebestresults.Themechanicalpropertiesofthe compositeswerecomparedwithFord’smaterialsspecification“WSS-M4D954-AandCA 387A(usedinautomotiveapplications).Comparedtothematerialsusedinautomotive applications,thegraphenenanoplatelets-basedcompositesshowedbettermechanical properties.Wangetal.[48]modifiedthepropertiesofSBSbymodifyingitwith3,6-di(2pyridyl)-1,2,4,5-tetrazine(DPT)andCuSO4.TheSBS-DPT/CuSO4 compositepresented goodtensilestrength,toughness,andshapememoryeffectwithashapefixityratioof78% 82%.Inanotherwork[49],atwo-wayshapememoryeffectwasobservedinolefinblock copolymer/siliconeelastomerwith70/30composition.DHBPwasusedastheflexibilizer.
1.4.5Biodegradableelastomers
Wangetal.[50]synthesizedpoly(glycerol-sebacate),abiodegradableelastomer,and observedgoodmechanicalpropertiesandbiocompatibilitybyinvitroandinvivo studies.Severalotherbiodegradableelastomerssuchaspoly(glyceroldodecanoate)[51] poly(3-hydroxybutyrate-co-3-hydroxyvalerate)[52],polyurethanes[53],andtheirpotentialapplicationshavebeenreported.
1.5Conclusion
Elastomersanimportantpolymermaterialwithinterestingpropertiessuchasflexibility, highelongationatbreak,andelasticity.However,theelastomerinitspureformpossessespoorelasticity,strength,andresilience.Therefore,onemustcross-linkelastomer withsulfurornonsulfurcomponentstohavedesirableproperties.Theblendingallowsto developmentofnewsystemswithinterestingpropertieswithlittleeffort.Blendsof elastomerwithotherplasticssuchasPP,PEarewellknown.Recentlyseveralnanofillers andothermodifiersareusedwidelyalongwithneatelastomerorwithelastomeric blendstoenhancethepropertiesoftheelastomer-basedcomposites.
Chapter1 Introductiontoelastomers7
Acknowledgments
ThisworkwassupportedbyKingMongkut’sUniversityofTechnologyNorthBangkokhasreceived fundingsupportfromtheNationalScience,ResearchandInnovationFund(NSRF)withGrantNoof KMUTNB-FF-65-19.
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