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UnsaturatedPolyester Resins
Fundamentals,Design, Fabrication,andApplications
UnsaturatedPolyester Resins
Fundamentals,Design, Fabrication,andApplications
Editedby SabuThomas
SchoolofChemicalSciences,MahatmaGandhiUniversity,Kottayam,India InternationalandInteruniversityCentreforNanoscienceandNanotechnology, MahatmaGandhiUniversity,Kottayam,India
MaheshHosur DepartmentofMaterialsScienceEngineering,TuskegeeUniversity,Tuskegee, AL,UnitedStates
CintilJoseChirayil DepartmentofChemistry,NewmanCollege,Thodupuzha,India
Elsevier
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ListofContributors
BasimAbu-Jdayil
ChemicalandPetroleumEngineeringDepartment,UnitedArabEmiratesUniversity,AlAin, UnitedArabEmirates;EmiratesCenterforEnergyandEnvironmentResearch,UnitedArab EmiratesUniversityAlAin,AbuDhabi,UnitedArabEmirates
M.Alagar
CentreofExcellenceforAdvancedMaterials,Manufacturing,ProcessingandCharacterisation (CoExAMMPC),Vignan’sFoundationforScience,TechnologyandResearch(VFSTR), Vadlamudi,India
AndreaC.Alexander
CenterforPolymersandAdvancedComposites,AuburnUniversity,Auburn,AL,UnitedStates
NimaAlizadeh
CenterforPolymersandAdvancedComposites,AuburnUniversity,Auburn,AL,UnitedStates; DepartmentofChemicalEngineering,AuburnUniversity,Auburn,AL,UnitedStates
SandroC.Amico
Post-GraduationPrograminMechanicalEngineering,UFRGS,PortoAlegre,Brazil; Post-GraduationPrograminMining,MetallurgicalandMaterialsEngineering,UFRGS, PortoAlegre,Brazil
M.Arous
DepartmentofPhysics,LaMaCoP,FacultyofSciencesofSfax,UniversityofSfax,Tunisia
AnjaliA.Athawale
DepartmentofChemistry,SavitribaiPhulePuneUniversity,Pune,India
MariaL.Auad
CenterforPolymersandAdvancedComposites,AuburnUniversity,Auburn,AL,UnitedStates; DepartmentofChemicalEngineering,AuburnUniversity,Auburn,AL,UnitedStates
D.Bachtiar
StructuralMaterialsandDegradationFocusGroup,FacultyofMechanicalandManufacturing Engineering,UniversitiMalaysiaPahang,Pahang,Malaysia
NilRatanBandyopadhyay
Dr.M.N.DasturSchoolofMaterialsScienceandEngineering,IndianInstituteofEngineering ScienceandTechnology,Shibpur,Howrah,India
MattiaBartoli
DepartmentofAppliedScienceandTechnology(DISAT),PolitecnicodiTorino,Torino,Italy
DibakarBehera
SchoolofAppliedSciences(Chemistry),KIITUniversity,Bhubaneswar,India
SamanthaA.Bird
CenterforPolymersandAdvancedComposites,AuburnUniversity,Auburn,AL,UnitedStates
BhabatoshBiswas
Dr.M.N.DasturSchoolofMaterialsScienceandEngineering,IndianInstituteofEngineering ScienceandTechnology,Shibpur,Howrah,India
DanielH.Builes
ResearchandDevelopmentCenter-Andercol,AndercolS.A.S,Medellı´n,Colombia
ShaliniChaturvedi
SamarpanScienceandCommerceCollege,Gandhinagar,India
CintilJoseChirayil
DepartmentofChemistry,NewmanCollege,Thodupuzha,India
Ang ´ elicaColpo
Post-GraduationPrograminMechanicalEngineering,UFRGS,PortoAlegre,Brazil
PragneshN.Dave
DepartmentofChemistry,SardarPatelUniversity,VallabhVidyanagar,India
VirginiaA.Davis
DepartmentofChemicalEngineering,AuburnUniversity,Auburn,AL,UnitedStates
EduardoA.W.deMenezes
Post-GraduationPrograminMechanicalEngineering,UFRGS,PortoAlegre,Brazil
S.Devaraju
PolymerCompositesLab,DivisionofChemistry,DepartmentofScienceandHumanities, Vignan’sFoundationforScience,TechnologyandResearch(VFSTR),Vadlamudi,India
HomNathDhakal
SchoolofMechanicalandDesignEngineering,AdvancedMaterialsandManufacturing(AMM) ResearchGroup,UniversityofPortsmouth,Portsmouth,UnitedKingdom
JohnR.Ebdon
InstituteforMaterialsResearchandInnovation,UniversityofBolton,Bolton,UnitedKingdom
MarcoFrediani
DepartmentofChemistry“UgoSchiff”,UniversityofFlorence,SestoFiorentino,Florence,Italy
LeandroFriedrich
Post-GraduationPrograminMechanicalEngineering,UFRGS,PortoAlegre,Brazil
CincyGeorge
DepartmentofChemistry,NewmanCollege,Thodupuzha,India
Z.M.Hafizi
AdvancedStructuralIntegrityandVibrationResearch(ASIVR),FacultyofMechanicaland ManufacturingEngineering,UniversitiMalaysiaPahang,Pahang,Malaysia
M.H.M.Hamdan
StructuralMaterialsandDegradationFocusGroup,FacultyofMechanicalandManufacturing Engineering,UniversitiMalaysiaPahang,Pahang,Malaysia
MedBenHassen
CollegeofEngineering,IndustrialEngineeringDepartment,TaibaUniversity,SaudiArabia; DepartmentofTextileEngineering,TextileEngineeringLaboratory,HITSofKsarHellal, UniversityofMonastir,Tunisia
MaheshHosur
DepartmentofMaterialsScienceEngineering,TuskegeeUniversity,Tuskegee,AL,UnitedStates
SikiruOluwarotimiIsmail
Manufacturing,Materials,BiomedicalandCivilDivision,SchoolofEngineeringandTechnology, HuttonBuilding,UniversityofHertfordshire,Hertfordshire,UnitedKingdom
KeilashC.Jajam
DepartmentofMechanicalEngineering,AuburnUniversity,Auburn,AL,UnitedStates
JoseJames
DepartmentofChemistry,St.Joseph’sCollege,Moolamattom,Idukki,India;Internationaland InteruniversityCentreforNanoscienceandNanotechnology,MahatmaGandhiUniversity, Kottayam,India;SchoolofChemicalSciences,MahatmaGandhiUniversity,Kottayam,India
J.Jamiluddin
StructuralMaterialsandDegradationFocusGroup,FacultyofMechanicalandManufacturing Engineering,UniversitiMalaysiaPahang,Pahang,Malaysia
J.Jayapriya
DepartmentofAppliedScienceandTechnology,A.C.Tech.,AnnaUniversity,Chennai,India
BaljinderK.Kandola
InstituteforMaterialsResearchandInnovation,UniversityofBolton,Bolton,UnitedKingdom
EktaKhosla
DepartmentofChemistry,HansRajMahilaMahaVidyalaya,Jalandhar,India
QiongLi
KeyLaboratoryofBio-BasedPolymericMaterialsTechnologyandApplicationofZhejiang Province,NingboInstituteofMaterialsTechnologyandEngineering,ChineseAcademyof Sciences,Ningbo,P.R.China;UniversityofChineseAcademyofSciences,Beijing,P.R.China
SongqiMa
KeyLaboratoryofBio-BasedPolymericMaterialsTechnologyandApplicationofZhejiang Province,NingboInstituteofMaterialsTechnologyandEngineering,ChineseAcademyof Sciences,Ningbo,P.R.China
RicardoBallesteroMendez
CenterforPolymersandAdvancedComposites,AuburnUniversity,Auburn,AL,UnitedStates; DepartmentofChemicalEngineering,AuburnUniversity,Auburn,AL,UnitedStates
SmitaMohanty
SchoolforAdvancedResearchinPolymericMaterials(SARP) LARPMCentralInstituteof PlasticsEngineering&Technology(CIPET)-IPT,Bhubaneswar,India
SanjayK.Nayak
SchoolforAdvancedResearchinPolymericMaterials(SARP) LARPMCentralInstituteof PlasticsEngineering&Technology(CIPET)-IPT,Bhubaneswar,India
MedAminOmri
DepartmentofPhysics,LaMaCoP,FacultyofSciencesofSfax,UniversityofSfax,Tunisia
ShivkumariPanda
SchoolofAppliedSciences(Chemistry),KIITUniversity,Bhubaneswar,India
JyotiA.Pandit
SchoolofChemistry,Dr.VishwanathKaradMITWorldPeaceUniversity,Pune,India
V.Ramamurthy
DepartmentofBiotechnology,PSGCollegeofTechnology,Coimbatore,India
M.R.M.Rejab
StructuralMaterialsandDegradationFocusGroup,FacultyofMechanicalandManufacturing Engineering,UniversitiMalaysiaPahang,Pahang,Malaysia
EmmanuelRichaud
PIMM,UMR8006,ENSAM CNRS CNAM,HESAMUniversit ´ e,Paris,France
LucaRosi
DepartmentofChemistry“UgoSchiff”,UniversityofFlorence,SestoFiorentino,Florence,Italy
SushantaK.Samal
SchoolforAdvancedResearchinPolymericMaterials(SARP) LARPMCentralInstituteof PlasticsEngineering&Technology(CIPET)-IPT,Bhubaneswar,India
S.M.Sapuan
DepartmentofMechanicalandManufacturingEngineering,UniversitiPutraMalaysia,Selangor, Malaysia
N.Saranya
DepartmentofAppliedScienceandTechnology,A.C.Tech.,AnnaUniversity,Chennai,India
AruniShajkumar
SchoolforAdvancedResearchinPolymericMaterials(SARP) LARPMCentralInstituteof PlasticsEngineering&Technology(CIPET)-IPT,Bhubaneswar,India
ArijitSinha
Dr.M.N.DasturSchoolofMaterialsScienceandEngineering,IndianInstituteofEngineering ScienceandTechnology,Shibpur,Howrah,India
J.P.Siregar
StructuralMaterialsandDegradationFocusGroup,FacultyofMechanicalandManufacturing Engineering,UniversitiMalaysiaPahang,Pahang,Malaysia
PavleM.Spasojevic
FacultyofTechnicalSciences,UniversityofKragujevac,Cacak,Serbia;InnovationCenterof FacultyofTechnologyandMetallurgy,UniversityofBelgrade,Belgrade,Serbia
AgnieszkaTercjak
Materials+Technologies Group(GMT),DepartmentofChemicalandEnvironmentalEngineering, FacultyofEngineeringGipuzkoa,UniversityoftheBasqueCountry(UPV/EHU),Donostia-San Sebastian,Spain
C.Tezara
DepartmentofMechanicalEngineering,FacultyofEngineeringandQuantitySurveying,INTI InternationalUniversity,NegeriSembilan,Malaysia
GeorgeV.Thomas
DepartmentofChemistry,St.Joseph’sCollege,Moolamattom,Idukki,India
SabuThomas
SchoolofChemicalSciences,MahatmaGandhiUniversity,Kottayam,India;Internationaland InteruniversityCentreforNanoscienceandNanotechnology,MahatmaGandhiUniversity, Kottayam,India
HareeshV.Tippur
DepartmentofMechanicalEngineering,AuburnUniversity,Auburn,AL,UnitedStates
A.Triki
DepartmentofPhysics,LaMaCoP,FacultyofSciencesofSfax,UniversityofSfax,Tunisia
JacquesVerdu
PIMM,UMR8006,ENSAM CNRS CNAM,HESAMUniversit ´ e,Paris,France
XiweiXu
KeyLaboratoryofBio-BasedPolymericMaterialsTechnologyandApplicationofZhejiang Province,NingboInstituteofMaterialsTechnologyandEngineering,ChineseAcademyof Sciences,Ningbo,P.R.China;SchoolofMaterialsScienceandEngineering,ZhejiangUniversity ofTechnology,Hangzhou,P.R.China
JinZhu
KeyLaboratoryofBio-BasedPolymericMaterialsTechnologyandApplicationofZhejiang Province,NingboInstituteofMaterialsTechnologyandEngineering,ChineseAcademyof Sciences,Ningbo,P.R.China
UNSATURATEDPOLYESTER
RESINS,BLENDS,
INTERPENETRATINGPOLYMER NETWORKS,COMPOSITES,AND NANOCOMPOSITES:STATEOFTHE
ARTANDNEWCHALLENGES
AnjaliA.Athawale1 andJyotiA.Pandit2
1DepartmentofChemistry,SavitribaiPhulePuneUniversity,Pune,India 2SchoolofChemistry,Dr.Vishwanath KaradMITWorldPeaceUniversity,Pune,India
1.1 INTRODUCTION
Unsaturatedpolyesters(UPs)aresyntheticcopolymershavingapplicationsasfibers,plastics,composites,andcoatings.Dependingonthechoiceofmonomers,initiators,curingagents,additives, andmodifiersused,differentvarietiesofproductscanbeproducedexhibitingawiderangeof chemicalandmechanicalproperties.Thelowcostinvolvedintheirproductionmakesthemattractive.Theirmainapplicationisasmatricesinthecompositeindustry.Amongthecomposites,fiber glass reinforcedcompositesareofprimeimportance.
1.2 TYPESOFUNSATURATEDPOLYESTERRESINS
Basedontheirstructure,unsaturatedpolyestersresins(UPR)canbeclassifiedas:(1)orthoresins; (2)isoresins;(3)bisphenolAfumarates;(4)chlorendics;or(5)vinylester(VE)resins.
1.2.1 ORTHORESINS
Orthoresinsarealsoreferredtoasgeneral-purposepolyesterresinsandarebasedonorthophthalic acid,namely,phthalicanhydride(PA),maleicanhydride(MA)/fumaricacid,andglycols.PAisrelativelycheapandprovidesrigiditytothebackbone.However,ithaslimitedthermalandchemical resistanceandprocessability.Amongtheglycols,resinsformedusing1,2-propyleneglycol(PG) aremoreimportantincomparisontootherglycols.ThependantmethylgroupinPGlowersthe crystallinityofresinandimprovesitscompatibilitywithcommonlyusedreactivediluents(suchas
UnsaturatedPolyesterResins.DOI: https://doi.org/10.1016/B978-0-12-816129-6.00001-6 © 2019ElsevierInc.Allrightsreserved.
styrene).NeopentylglycolorhydrogenatedbisphenolAyieldsresinswithhighheatandchemical resistance.
1.2.2 ISORESINS
Isoresinsarepreparedusingisophthalicacid,MA/fumaricacid,andglycol.Theyarerelatively expensiveandhaveconsiderablyhighviscosities.Hence,theyrequirealargeproportionofreactive diluent,whichalsoimpartsimprovedwaterandalkaliresistancetocuredresins.Theyfindapplicationsasgelbarriercoatsinmarineenvironmentssincetheyhavebetterthermalandchemicalresistanceandmechanicalproperties.
1.2.3 BISPHENOLAFUMARATES
Thesearesynthesizedusingethoxy-basedbisphenolAandfumaricacid.Thoughexpensive,they exhibitsuperiorchemicalpropertiesaswellascorrosionresistanceascomparedtoorthoandiso resins.ThepresenceofbisphenolAinthebackbonerendersahigherdegreeofhardnessandrigidityandimprovedthermalperformance.Duetothereducednumberofinteriorchainestergroups, theirhydrolysisresistanceisbestamongcommercialunsaturatedresins.
1.2.4 CHLORENDICS
Chlorine/bromine-containinganhydridesorphenolsareusedforpreparingchlorendics.They exhibitflameresistancealongwithgoodchemicalandcorrosionresistance.Forexample,thereactionbetweenchlorendicanhydride/chlorendicacidandMA/fumaricacidandglycolyieldsresin withbetterflameretardancythangeneral-purposeUPR.Othermonomersusedincludetetrachloroortetrabromophthalicanhydride.Thebrominecontentmustbeatleast12%inordertoobtaina self-extinguishingpolyester.
1.2.5 VINYLESTERRESINS
VEresinscontainunsaturatedsitesonlyattheterminalpositionasbisacryloxyorbismethacryloxy derivativesofepoxyresins.Theyarepreparedthroughthereactionofacrylicacidormethacrylic acidwithepoxyresin(e.g.,diglycidyletherofbisphenolA(DGEBA),epoxyofthephenolnovolac type,orepoxybasedontetrabromobisphenolA).Theseresinswerefirstcommercializedin1965 byShellChemicalCompanyunderthetradenameEpocryl [1].In1966DowChemicalCompany introducedasimilarseriesofresinsformoldingpurposesunderthetradenameDerakaneresins [1].Theviscosityofneatresinsishigh;hence,reactivediluents(e.g.,styrene)areaddedtoobtain solutionswithlowerviscosities(100 500poise).NotableadvancesinVEresinformulations includelow-styrene-emissionresins,automotivegradeswithhightensilestrengthandheatdeflectiontemperature,hybridgradesthatbalanceperformanceandeconomy,andmaterialsforcorrosion resistance.
1.3 SYNTHESISOFUNSATURATEDPOLYESTERRESINS
UPisoftensynthesizedasaviscousliquidthroughthemeltcondensationofanaromaticdicarboxylicacidsuchasphthalicacidoranhydridewithpolyhydricalcoholandunsaturateddicarboxylic acidoranhydride.Theviscosityofthereactionproduct/oligoester(OER)isreducedusingareactivediluentsuchasavinylmonomer,usuallystyrene.FreeradicalcopolymerizationbetweenstyreneandthedoublebondsofUPresultsinarigidthree-dimensionalcross-linkedstructure,which isaheterochainthermosettypeofpolymer.Methylethylketoneperoxide(MEKP)isastandard catalystthatinitiatesthecuringreactionincombinationwithacobaltorcobalt-amineactivatorsystem/acceleratoratroomtemperature.OtherfreeradicalsusedforcuringUPRsincludebenzoylperoxide(BPO)orcumenehydroperoxide [2].Aftersynthesis,aninhibitorisaddedtotheresinto providealongstoragelife,fastcure,andtominimizecatalyzedoruncatalyzeddrift,undesirable colors,odors,orsideeffects.Hydroquinone,4,4-dihydroxybiphenyl,andsubstitutedcatecholsare someexamplesofinhibitors [3].
Attemptshavebeenmadebyvariousresearcherstotailorthemechanical,thermal,corrosion, andfireresistancepropertiesofUPRsforvariousapplications.Parkeretal.suggestedtheuseof isophthalicacidforimprovedmechanicalpropertiesandcorrosionresistance [4].Atwo-stagesynthesisprocesswaspatentedbyWatanabeetal.toaddressthenecessaryimprovementsusing dimethylterephthalateinsteadofisophthalicacid [5].Styrene,vinyltoluene,tert-butylstyrene, chlorostyrene,anddiallylphthalatehavebeenusedasreactivediluents.Theeffectsofvariousconcentrationsofanhydride(PAandMA)onmechanicalpropertieswerereportedbyThomasetal., with60% 70%MAshowingthebestmechanicalproperties [6].Theyalsosynthesizedvariousformulationsbyvaryingboththeanhydrideandthealcoholconcentration.Amixtureof60%MA withPAyieldedanUPRwiththebestmechanicalproperties.However,resinwithahigherproportionofPAwasfoundtobetoughandflexible.Similarly,diethyleneglycol(DEG)increasedthe toughness,impactstrength,andflexibility,whichwaslostonstanding.Optimalpropertiesare observedwitha20/80ratioDEG/PGresintogetherwithanequimolaramountofMAandPA [7] UPRshavealsobeensynthesizedfrombio-deriveddiestersofunsaturateddiacidssuchasitaconic, succinic,andfumaricacidswithvariousdiolsandpolyolstoaffordresinsof M n B480 477,000 andglasstransitiontemperature(Tg)ofbetween 30.1 Cand 16.6 Cwithsolubilitiesdiffering basedonthestartingmonomersused [8].Yoonetal.regeneratedUPRafterrecyclingcuredUPR. TherecycledUPRexhibitedafastercuringratethanthatofneatresin.Acomparisonofthe mechanicalpropertiesoftheneatresinandthemixtures(neatresinandrecycled)revealedthat althoughthepropertiesofneatresinweresuperior,thoseofthemixturesweredependentoncompositionandwerefoundtobesuitableformanyapplications [9].
Differentproportionsofcobalt(Co)curingagentwereused(0.05% 1%).Anincreaseinthe concentrationofCofrom0%to1%ledtoadecreaseincuringtime.Thiswasreducedtohalfin thepresenceof0.05%Co [10].Theeffectofvolumeratiosofcuringagents,viz.,cobaltoctoateas anacceleratorandMEKPasaninitiator,ongelationtimeandexothermbehaviorofaUPRhas alsobeenstudied.Thegelationoftheresinwasfoundtocorrespondwiththeonsetofanincrease intemperatureduringresincuring.Thegelationtimewasfoundtovaryinverselywiththeconcentrationsofacceleratorandinitiator [11].Theviscosityoftheliquidsystemwasfoundtodecrease withincreasingtemperature,butincreasedatthecuringtemperature.ThequalityofthecuredUPR
waspredictedonthebasisofitsfragilityparameter(Mc).IntheUPR MEKPsystem,thesmaller theMcthelargerthe Tg andthebettertheheatresistance [12]
ThecuringbehaviorofUPRwasstudiedusinganexperimentalandtheoreticalmodelbyKosar andGomzi [13].Thekineticbehaviorofthecuringsystemwasinvestigatedusingbothdynamic andisothermalmeasurementsandagoodagreementwasestablishedbetweenthetwo(intermsof presentedkineticparametersandreactionheat).Heatgeneratedfromthecurereactionwasmeasuredinmoldsofcylindricalshape.Thedifferenceinheatconductivitybetweenglassandcopper wasthemainreasonforthegreaterheatgeneratedintheglassmold.
Controloverresinshrinkageofresidualmonomersisanimportantconcerninlow-temperature moldingprocesses.Thepresenceoflow-profileadditives(LPAs)canreducetheshrinkageofUPR/ styreneresinsunderproperprocessingconditions,butmayincreasetheresidualstyrenecontent.A systematicstudywascarriedouttoinvestigatetheeffectoftheinitiatorsystemandreactiontemperatureonthesamplemorphology,finalresinconversion,andresinshrinkageofUPRwithLPA. Theresultsshowedthatthefinalconversionoftheresinsystemcouldbeimprovedbydualinitiators,withtheeffectbeingprominentatlowtemperatures.Thestudyonshrinkagecontrolreported thatgoodLPAperformanceswereachievedatlow(35 C)andhigh(100 C)temperatures,but worseperformanceswereobservedintheintermediatetemperaturerange(e.g.,60 C 75 C) (Fig.1.1).Thefinalshrinkageisinfluencedbytheeffectoftemperatureonthemorphology,the relativereactionrateintheLPA-richandUPR-richphases,andmicrovoidformation [14].The samplemorphologyshowsatwo-phasecocontinuousstructureat35 C(Fig.1.2).Oneisaparticulatephase(LPA-rich)havinglooselypackedsphericalparticleswithdiametersrangingfrom1to 5mm.Theotherphaseisaflake-likeregion(UPR-rich)withdomainsizesrangingfrom10to 20mm.Atacuringtemperatureof60 C,asimilartwo-phasestructureisobserved,butitisnolongercocontinuous.Theparticulateregionissmallerandbecomesthedispersedphasewithadomain
VolumeshrinkageofUP/St/LPAsystemscuredatdifferenttemperatures(3.5%LPA,0.5%CoOct.,1.3% MEKP,0.4%TBPB,300ppmBQ).
FIGURE1.1
FIGURE1.2
MorphologyofSt/UP/LPAsamplescuredatdifferenttemperatures(3.5%LPA,0.5%CoOct.,1.3%MEKP, 0.4%TBPB,300ppmBQ).
sizeoflessthan20mm,whiletheflake-likeregionformsthecontinuousphase.Onincreasingthe temperatureto75 Cand100 C,thesizeoftheparticulateregionisfurtherreduced.Thevarious morphologicalstructuresresultindifferentinterfaceareas,stronglyaffectingtheshrinkagecontrol.
CommercialUPRscontain30% 40%styrenebymass.Themiscibilityofresinandstyrene dependsontheresincomposition.Phaseseparationisreportedwithanincreaseinstyreneconcentration.Thermalstabilityandmechanicalpropertiesaregovernedbythephasebehaviorofthemixtureandcan,therefore,becontrolledbystyrenecontent [15].Dynamicmechanicalanalysis(DMA) testshaveshownphaseseparationincuredresinwithhighstyreneconcentrations. Tg isalsodependentonstyreneconcentrationtogetherwiththermalstabilityandmechanicalbehavior [16].
1.3.1 LOW-STYRENE-EMISSIONUNSATURATEDPOLYESTERRESIN
StyrenehasremainedapreferredreactivediluentforaddingtoUPduetoitscostandavailability. Itcontrolstheviscosityandfacilitatesthecuringofpolyestersatroomtemperature.However,the useofstyreneisassociatedwithserioushealthproblemssuchasrespiratorydiseasesandskin
irritation.Itiscarcinogenicandalsoattacksthecentralnervoussystemonexposureoveralong periodoftime,leadingtopossibleheadachesanddepression.Theminimizationofstyrenevolatilizationoritseliminationusingalternativemonomersisbeingattemptedtoovercomethese problems.
Thevolatilizationofstyreneisreducedbyparaffinicwaxeswhichactasabarrier.However, thewaxlayerneedspriorremovaltoavoidproblemsofadhesiontootherparts.Theambientconcentrationofstyrenevaporcanbereducedusingspraygunsthatcanmonitortheamountofresin sprayed.Sincealternativessuchasvinyltoluene,alpha-methylstyrene,anddiallylphthalatesuggestedforstyrenealsoinvolvehealthhazards,PoillucciandHansenproposedtheuseofbioderivedlimoneneoilandpetroleum-derivedvinylneodecanoateandvinyllauratesasothersubstitutesforstyrene,buttheyexhibitlimitedchemicalcompatibility.Thestyrenecontentwasreduced by50%usingtrimethylolpropanediallylether [17].Marianiusedvariouscross-linkingagentssuch as2-hydroxyethylacrylates(HEA)oramixtureconstitutedofdiurethanediacrylateandstyreneor HEAforfrontalcuringofUPRderivedfromthereactionofMAand1,2propanediol [18].Zang etal.reportedabenzylend-cap-UPresinwithlowstyreneemissionusingbenzylalcoholasthe end-capper [19]
Fornonhalogenatedresins,amarkedrestrictioninstyreneemissionisachievedbyincluding long-chainalpha-olefinswith18 40carbon(C)atomswithouttheadditionofwax.Theseolefins ontheirownwillnotusuallyprovidesuchamarkedrestrictioninstyreneemission,butwillallow fortheincorporationofawaxycompoundinanamountsufficientlylargetoachievethedesired styreneemissionrestrictionwithoutincurringtheexpecteddisadvantagesassociatedwiththeincorporationofsuchlargeamountsofwaxycompound [20]
1.3.2 STYRENE-FREECOMPOSITIONSFORCURABLECOATINGS
WhenUPRsareusedascoatings,styrene-freecompositionsarefavoredsincevolatileemissionsby suchcompositionsareexpectedtobelow.Anexampleofsuchaformulationconsistsofonecomonomerselectedfromthe(meth)acrylatesofcycloaliphaticalcoholsandoptionalcomonomerscould betetrahydrofurfuryl(meth)acrylate,methoxypolyethyleneglycol,mono(meth)acrylate,ethylene glycoldimethacrylate,anddi(ethyleneglycol)di(meth)acrylatewhilethecuringcanbedoneby radiationand/orthroughtheperoxideorthermalroutes.Morespecifically,curingcanbeperformed byadoptingaprocesscomprisingatleastonestepofradiationand/orperoxidecuring [21].
Styrene-freeUPRcoatingscuredbyinfraredradiationsaredescribedascontaininganunsaturatedethercomponentaswellassaturatedmonohydricalcoholalongwithdicarboxylicacidand dihydricalcohol [22].Also,radicallycurablestyrene-freecoatingsareclaimedtobecomposedof compoundscontaininga(meth)acryloylgroupand/orvinylethergroupsalongwithparaffin,aplasticizer,andcarbamicacid [23].Styrene-freecompositionsarereportedbyusingvariousreactive diluentssinglyorincombinationsuchas2-hydroxyethylmethacrylate,2-hydroxypropylmethacrylate,2-HEA,2-hydroxypropylacrylate,andrelatedcompounds [24]
UPRcanalsobeobtainedasareactionproductofatleastonediolhaving2 8Catoms,one monoalcoholwithatleastoneallylicunsaturation,andatleastonesaturatedaliphaticmonoalcohol having4 10Catomsoronearomaticmonoalcoholhaving7 10Catoms.Thecoatingormolding compositionofsuchaUPRiscurablebyradiationand/orthroughtheperoxideorthermalroutes [25].McAlvinreportedUPRderivedfrombiologicallyrenewableresourcesandrecycledmaterials,
whicharestyrene-freeandultralowvolatileorganiccompound(VOC)resinsthatprovidematrix materialstoproducemoreecologicallyfriendlycomposites [26].Astyrene-freeUPRforminga stabledispersioninwaterhasbeenreported.Themodificationwasdonebyintroducingpolar hydrophilicgroupssuchascarboxylicandsulfonicgroups(sodium5-sulfonatoisophthalicacid) intotheresinmolecule,whichensuregoodtolerancetowater.Styrenehasbeenreplacedwiththe glycerolmonoethersofallylalcoholandunsaturatedfattyalcoholsasreactivebuilt-incross-linking monomersforresinmodification [27].
1.3.3 MODIFICATIONOFUNSATURATEDRESINFORVISCOSITYCONTROL
UPRshavereplacedsheetmetalinmanyapplicationssuchasintheautomotive,electric,andhome applianceindustriesasaconsequenceoftheirpropertiessuchasbeinglightweight,havinghigh strength,andtheirnoncorrosivenature.UPRcompositeproductsaremanufacturedbycompression moldingintheformofsheetmoldingcompounds(SMCs)orbulkmoldingcompounds(BMCs), throughinjectionmoldingintheformofBMC,resintransfermolding,casting,andhandlayup. Chiuetal.attemptedtodevelopUPRsystemsexhibitingviscosityprofilepropertiessuchasrapid increaseduringmaturation/thickeningandmoldfillingsothattheycanbehandledeasily,have goodfibercarryingcharacteristics,andlong-termstability.Forgoodmaterialflow,asignificant reductioninviscosityisrequiredduringmoldingwhichfacilitatesthecompletefillingofthemold aswellasthecompletewettingofthefillerandotheringredientsinthesystembytheUPR [28].
Fig.1.3 showstheidealviscosityprofilesforSMCsandBMCsduringmolding.
Chemically,thickeningor“maturation”occursbylinkingupvariousUPRmoleculestogetherto formpolymerchainsofconsiderablyhighermolecularweights.Usually,thisisdonebyaddinga
FIGURE1.3
IdealviscosityprofileforSMCsorBMCsduringmolding:(I)thickening;(II)storage;(III)moldfilling;and(IV) curing.
di-ormultifunctionalcompoundtothesystemwhichcouplestwoormorepolyestermolecules togetherviatheirterminalhydroxyland/orcarboxylgroups.AsUPRmoleculesusuallycontain morethantwofunctionalgroups,theactualproductformedisacomplexnetworkofinterconnected polymerchainsratherthandiscreteindividualchains.CompoundsusedforthickeningUPRsare knownas“thickeningagents”or“maturationagents.”Twotypesofcompoundsareusedasthickeningagents.ThefirsttypecomprisesGroupIIAmetaloxidesandhydroxides,forexample,MgO [29].MaturationwiththistypeofagentoccursviatheformationofionicbondsthroughthereactionofMgOwiththecarboxylicacidendgroupsofpolyestermolecules.Theothertypeofmaturationagentisdiisocyanate [30].Diisocyanatesoperatebyformingcovalentbonds,specifically urethanelinkages,withtheterminalhydroxylgroupsofpolyestermolecules.Eachtypeofmaturationagenthasitsownadvantagesanddisadvantages.ThematurationprocesswithMgO-typeagents isslow.Theyformionicbondswhichweakenatelevatedtemperaturesencounteredduringmolding.Thisresultsinareducedcompoundviscosityandhencethedesiredmaterialflow. Diisocyanatematurationagentsexhibitrapidthickening.Thecovalentbondsformedwith isocyanate-typethickenersdonotweakenatmoldingtemperaturesandhencematerialflowismore difficult.MgO-typematurationagentsarehighlysensitivetohumidityaftermaturation,whereas diisocyanatesarenot.Athermallybreakabledi-ketogroupcanbeintroducedontotheUPRmoleculebeforecuringthroughsaltformation.Thisgroup,alongwiththesalt,maybreakatelevated temperatureinmostUPRmoldingoperationsandthereforereducethecompoundviscosityupon heating;hencethedesiredamountofmaterialflowisrealized.ModifiedresinsarefurtherthickenedwithMgOordiphenyldiisocyanate.Thisexhibitsafastviscosityriseduringmoldinganda stableviscosityduringroomtemperaturestorage [28]
MoldedarticlesmadewithconventionalUPRsoftenexhibitpoorsurfacefinishes.ThisisprobablyduetoshrinkageoftheUPRduringthemoldingoperation.LPAsareusedtoovercomethis problem.AlongwithLPAs,goodmaterialflowduringmoldingisalsonecessarytoobtainfinishes ofthehighestquality.ThereducedmaterialflowencounteredwhendiisocyanatesareusedasthickenersreducestheeffectivenessofLPAinthesesystems,whichinturnmayleadtosignificantfinishproblems.OneproposaltoovercomethislimitationistouseacombinationofbothMgO-type anddiisocyanate-typethickenersinthesamesystem [31].
1.4 UNSATURATEDPOLYESTERSRESINBLENDS
Polymerblendsaremadebythephysicalmixingoftwoormoredifferentpolymersorcopolymersto produceamixturewithdesirablemechanicalandphysicalproperties.Usually,the Tg ofcuredUPRs arehighandtheirbrittlenesspresentsanobstaclefortheiruseinengineeringapplications [32].The mechanical,physical,andthermalpropertiesofUPRcanbeimprovedbyblendingwithotherpolymersorbyreactingthemwithdifferentadditivesormodifierswhichgenerallyformaseconddispersedphaseaftertheresiniscured.Blendsshowthedemandedperformanceatlowcost.
1.4.1 UNSATURATEDPOLYESTERSRESIN ELASTOMERBLENDS
TheadditionofelastomericphasestoUPRsusuallyimprovestheiroverallductilityoverawide rangeoftemperatures,toughness,andimpactresistances.ElastomersareblendedwithUPRbefore
curingbyphysicalandchemicalmethods.Whenblendsareformedbythephysicalmixingoftwo ormorepolymersatleast5%ofanotherpolymerisnecessarytoformablend.Ifthecomponent polymersaremiscible,asingle-phaseblendisobtained.Iftheyareimmiscible,amultiphaseblend isformed.Evenifrubberadditivesaresolubleinuncuredresin,phaseseparationduringcuringis advantageoussincetheseblendsaretougherthanhomogeneousblends [33,34].Thepresenceof elastomericdomainsincreasestheabsorptionanddissipationofmechanicalenergy.Various mechanismsproposedfortougheningbyblendingwithrubberincludethedebondingoftherubber matrixinterphase,energyabsorptionbyrubberparticles,matrixcrazing,shearyielding,andcombiningshearyieldingandcrazing [32,33].
Essentialcharacteristicsofelastomersfortougheningare [35]:
1. Thepresenceofasufficientnumberofpolargroupstoenhancesolubilityintheresin.
2. Theelastomershouldhaveaslowrateofcross-linkingcomparedtotheUPRusedtofacilitate thedistributionofdiscreteelastomericparticlesduringcross-linking.
3. Theweightoftheelastomershouldberelativelyhigh.
4. Themajorpartoftheelastomershouldbethermodynamicallyincompatiblewithresin.
1.4.1.1 Unsaturatedpolyestersresin naturalrubberblends
Naturalrubberisanelasticmaterialpresentinlatexfromrubbertrees.Itseasyavailability,low cost,andexcellentphysicalpropertiessuchasgoodresilience,hightensilestrength,superiorresistancetotearandabrasion,goodtack,andself-adhesionhaveledtoitsuseinpreparingblends.On theotherhand,ithaspoorageresistanceandoilresistance.
BlendsbasedonUPRfromrecycledpoly(ethyleneterephthalate)(PET)wasteswithvarying percentages(0% 7.5wt.%)ofliquidnaturalrubber(LNR)havebeenpreparedbyHishametal. Theyarefoundtoexhibitgoodcompatibilitycomparedtocommercialresins,butshowhigher Tg. Ablendwith2.5wt.%LNRrenderedthehigheststrengthandbestdispersionofelastomerparticles whilecommercialresinrequired5%ofLNRtoachieveoptimumproperties [36].Studiesonthe influenceofthesourceofwaterandimmersiontimeonthemechanicalpropertiesofUPR natural rubberblendshaverevealedincreasesintheimpactstrengthandstrainratesanddecreasesinthe Young’smodulusofpolymerblendsunderidenticalconditions [33].HybridprotonexchangemembranesasanalternativeforNafioninpolymerelectrolytemembranefuelcell(PEMFC)weredevelopedbyJimenezetal.UPR naturalrubberblendswerepreparedandsubjectedtotheprocessof vulcanizationandTiO2 wasaddedasaninorganicload.TheblendsexhibitedhigherYoung’smoduliandstrainscomparedtocommercialNafionmembranes.Thewateruptakeaswellasion exchangecapabilitiesofthevulcanizedmembranewasfoundtobesuperior [37].Naturalrubber latex(NRL)whenblendedwithUPRinthepresenceofdispersionaidssuchassodiumlaurylsulfate(SLS),toluene,andammonialedtoanimprovementinimpactstrength.However,theflexural strengthdecreasedwithNRLcontentintheblend(Fig.1.4).Theimpactstrengthwashighestwhen NRLandtoluenewere15phrand20wt.%,respectively [38].
1.4.1.2 Unsaturatedpolyestersresin-syntheticrubberblends
SyntheticrubbershavealsobeenusedforblendingwithUPRs.BinarypolymerblendsofUPRand differentweightratios(0%,5%,10%,and15%)ofnitrilebutadienerubber(NBR)havebeenpreparedbymechanicalmixingusingtolueneasasolvent.However,theyshowedpoormechanical
FIGURE1.4
ImpactstrengthofpureUPRandUPR/NRLblendsusingdifferentdispersionaids:(A)usingSLSasadispersion aid;(B)usingtolueneasadispersionaid;and(C)usingliquidammoniaasadispersionaid.
properties,exceptfortheirstrainrateswhichwerehigher.Thewearratesoftheblendswerefound todecreasewithincreasingNBRcontent [39].CherianandThachilpreparedblendsofUPRwith elastomersbearingreactivefunctionalgroupssuchashydroxy-terminatedpolybutadiene,epoxidizednaturalrubber,hydroxy-terminatednaturalrubber,andmaleatednitrilerubber.Theseelastomersshowbettercompatibilitywithresinandimpartsuperiortoughness,fractureresistance,and impactresistanceascomparedtounmodifiedelastomers [34].TheauthorsalsosynthesizedUPR blendsusingtwodifferentstrategiesforincorporatingrubber.Thefirstmethodinvolvesthedissolutionofmasticatedelastomerssuchasnaturalrubber(NR),styrenebutadienerubber(SBR),NBR, butylrubber(IIR),andchloroprenerubber(CR)instyrenefollowedbyblendingwithUPR,while inthesecondmethod,elastomersaremodifiedwithMAandthendissolvedinstyreneandblended withUPRtogetmaleatedelastomers.BlendshavingelastomersmodifiedwithMAshowimproved mechanicalproperties(toughness,impactresistance,andtensilestrength)comparedtounmodified rubbers(Tables1.1and1.2).Theperformanceofnitrilerubberisfoundtobefarsuperiorin
Table1.1SummaryofPropertiesofUPRModifiedWith0%
5%Elastomers
MaximumImprovementAchieved(%)/Elastomer Concentration(%)
PropertyUPR
Tensilestrength(MPa)33.357.8/2.553.9/283.4/2.540.8/2.516.4/2
Modulus( 3 102 MPa)14.124.2/2.515.1/28.6/2.521.3/2.52.9/2
Elongationatbreak(%)2.2544.4/2.533.8/288.9/2.524.4/2.57.1/1
Toughness(MPa)0.36136/2.5111/2286/2.597.2/2.541.7/2
Impactstrength( 3 10 2 J/mm2)1.21150/2.5107/2239/2.590.1/2.550.4/2
Hardnessshore D 88 0.6/1 0.6/10/1 1.1/1 1.7/1
Abrasionloss(cc)0.3732.4/518.9/521.6/527.0/537.8/5
Waterabsorption(%)0.2190.5/538.1/547.6/557.1/576.2/5
Table1.2SummaryofPropertiesofUPRModifiedWith0% 5%MaleatedElastomers
Tensilestrength(MPa)33.2884.0/2.563.0/297.8/2.571.5/2.535.0/2
Modulus( 3 102 MPa)14.124.8/2.510.8/28.9/2.515.2/2.56.0/2
Elongationatbreak(%)2.2558.7/2.558.2/295.6/2.564.9/233.8/2
Toughness(MPa)0.36214/2.5161/2303/2.5184/2.588.9/2
Impactstrength( 3 10 2 J/mm2)1.21203/2.5116/2.5247/2.5136/366.9/2
Hardnessshore D 88 0.6/1 0.6/10/1 1.1/1 1.1/1
Abrasionloss(cc)0.3737.8/518.9/527.0/532.4/548.6/5
Waterabsorption(%)0.21100/542.9/557.1/571.4/590.5/5
comparisontoallotherrubbers [32].Tougheningagentslikecarboxylandvinylterminatednitrile rubbersaswellasurethanerubbershavealsobeenusedforpreparingblends.Theincorporationof flexiblepolyorganosiloxanesegmentsintheUPRnetworkenhancesitsflexibility [34].Thethermal stabilityoftoughenedUPR NBRimprovedonreinforcingitwithslagpowder.Thesamplemodifiedwithstearicacidshowedbettermechanicalproperties.Afireresistancetestshowedreduced masslosswhenexposedtodirectopenflame [40].
Suspeneetal.observedanimprovementinthecompatibilityofaUPR carboxyl-terminated butadiene-acrylonitrilerubber(CTBN)blendbyexchanging10%CTBNforepoxy-terminatednitrile rubber(ETBN)inablendwith5phrofrubber.Intheresultingtriblockcopolymeradecreasein particlesizeofthedispersedrubberyphasefrom12to5 μmwasobservedandtheinterfacialtensionbetweenUPRandCTBNisalsoreduced.Theimpactbehaviorofthetriblockcopolymerwas enhancedduetoareductioninfailurescausedbythepresenceoflargeparticles [41].
1.4.2 UNSATURATEDPOLYESTERSRESIN PHENOLFORMALDEHYDERESIN BLENDS
UPRsarehighlyflammableandproducelargequantitiesofsmokeandtoxicgasesonburning.The flameresistanceofUPRcanbeimprovedbyaddingflame-retardantadditivesorbyblendingit withotherpolymerssuchasphenolicformaldehyderesins(PF).Theadditionofadditivesusually leadstounfavorablereactionsbetweenthepolymerandadditivesresultinginthedeteriorationof themechanicalpropertiesofpolymerstosomeextent.BlendsofUPRandPFshowgoodfireretardantabilitiesduetothehighcharringtendencyofPF.PFisknowntogeneratelesstoxicgasesand smokeandleavealargeamountofcarbonresidue [42]
Amongphenolicresins,resolesandnovolacsareimportant;oncuring,theyproducehighly cross-linkedthermallystablenetworkstructures,whichonexposuretohighheatorfire,char,thus producingrelativelylowlevelsofcombustiblevolatiles [43].Kandolaetal.usedethanol-soluble epoxyandallyl-functionalizedphenolicresolestoovercometheincompatibilityofUPRandPF resinsresultingfromtheirchemicalstructuresandcuringmechanisms.Theydemonstratedan increaseincompatibilitywithfunctionalization.Allyl-functionalizedresoleexhibitedthebestcompatibilitywithUPR.Amechanismhasbeenproposedfortheirdecompositionandinteractionsand theireffectsonflammabilitybasedonthermalbehaviorandinfraredspectroscopicanalysisofvolatiledegradationproducts [44].Mahadaretal.blendedUPRwithresoletoproducematerialswith goodflameretardancy.Theblendsshowedgoodcompatibilitywhencompoundedwithkenaffiber, whichisanaturalfiber.Althoughthethermalstabilityoftheblendswasimproved,themechanical propertieswerefoundtobeslightlyinferior [42].Novolacresinwasmodifiedwithfree-radically curablemethacrylategroups(M-Nov)withstyrenetogiveamaterialwithahigher Tg,betterthermalandthermo-oxidativestabilities,andbetterflameretardancythancuredUPR,withanapproximately20%lowermodulusatroomtemperature(RT) [43].Analternativemodificationofnovolac withthevinylbenzylgrouptoobtainahomogeneous,free-radicallycocuredphenolic/UPRblend withbetterflameretardancythanthosemadeusingM-Novhasalsobeenattempted.Thecured vinylbenzylatednovolacanditscocuredblendswithUPRexhibitedsuperiorflameretardancyin comparisontocuredUPRandhavepotentialapplicationsasmatrixresinsinglass-reinforcedcompositelaminates,especiallyformarinestructures [45]
1.4.3 UNSATURATEDPOLYESTERSRESIN EPOXYRESINBLENDS
UPRandepoxyresinaremisciblewitheachotherandshowgoodcompatibility.Hybridpolymer networks(HPNs)basedonUPRandepoxidizedphenolicnovolacs(EPNs)havebeenprepared throughreactiveblending.EPNshowsgoodmiscibilityandcompatibilitywithUPR.Theblend showssubstantiallyimprovedtoughnessandimpactresistancealongwithbetterthermalstability. Blendswith5wt.%ofEPNexhibitthehighesttensilestrength [46,47].HPNswerealsosynthesized bycoreactingUPRwithepoxidizedcresolnovolacandDGEBA.Cocuredblendedresinsshowed substantialimprovementsintoughnessandimpactresistancealongwiththermalstabilityand dampingproperties.TheperformanceoftheblendswithEPNwasfoundtobesuperior [47].
AnewbioresinwasproducedbyMustaphaetal.byblendingUPRwithepoxidizedpalmoil (EPO)in10,20,and30wt.%.TheadditionofEPOinUPRresinloweredthe Tg at20wt.%loadingofEPO, Tg decreasedby 6 5 C,andthestoragemodulusdecreasedbyabout20%incomparisontoUPR.However,theimpactpropertiesincreasedwiththeamountofEPOadded.EPO providesarubberyphaseandabsorbstheenergyappliedbytheimpactloadings.Bio-basedthermosetUPRblendedwithEPOmayreducethedependencyonconventionalcompositematrixsystems madefrompetrochemicals [48]
UPRswerepreparedbyreactingbisphenolAepoxyresinwithvariousglutaconicacidsusinga basecatalyst.Theywerefunctionalizedbytreatmentwithacryloylchloridetoyieldacrylated polyesters(APEs).BlendingoftheseAPEswerecarriedoutwithstyrenemonomers.Incomparison toAPEs,theseblendsexhibitedhighcuringtemperatures,slowdegradationofproducts(i.e.,low weightloss),goodchemicalresistances,andgoodmechanicalandelectricalstrengths [49]
1.4.4 UNSATURATEDPOLYESTERSRESIN ESTERSBLENDS
ArdhyanantablendedVEandUPRcontainingaromaticbenzenerings(10% 80wt.%).TheUPR/ VEblendswerepreparedbymechanicalblendingandcuredatroomtemperatureusing4%of MEPKintheabsenceofanaccelerator.Themechanicalandthermalpropertiesoftheblendswere foundtobesuperior [50].Polymerblendsofunsaturatedpolyetheresterresinsanddicyclopentadienepolyesterresinsyieldcuredthermosetresinshavinghightensileandflexuralstrengths.The coactionresultingfromblendedpolymersprovidesaneconomicwaytoimproveboththestiffness andstrengthofcuredpolyetheresterresins [51]
Styrenatedpolyesterresinswereblendedwithpoly(vinylacetate)(PVAc).Acocontinuous phasemorphologywasobservedinblendscontainingPVAcwithconcentrations $ 6%andstyrene levels $ 40%.Anincreaseinthestyrenecontentfrom20%to80%resultedinthesharpeningof theprincipaldynamiclosspeak,andthepeaktemperaturereachedamaximumataconcentration of40%.ThechangefromparticulatePVActococontinuousstructurewasassociatedwithasharp dropinGBcandKBc.Parallelstudieshaveshownthistransitiontobeimportantin“low-profile” behavior [52].
1.4.5 UNSATURATEDPOLYESTERSRESIN POLYSACCHARIDEBLENDS
ModifiedUPwasblendedwithcelluloseandethylcellulose(5% 25%)atambientconditionsin thepresenceofMEKPasacuringagent.TheblendsshowedcompatibilitywithmodifiedUPasa
resultofthepolar OHgroupsintheirstructure.Theresultsindicatethatcelluloseincreasesthe impactstrength,hardness,anddielectricconstantanddecreasesthebendingoftheblends,while ethylcellulosecausesanincreaseintheimpactstrength,hardness,andbendingbutadecreasein thedielectricconstantoftheblends [53].TheworkdonebySalihetal.involvestheblendingof UPRwithstarchpowder(0 3wt.%fraction)withparticlesizeslessthan45 μm.Theblendswere furtherirradiatedbyUVacceleration.TheUVirradiationshadanoticeableeffectonmostofthe mechanicalpropertiesoftheblends.ThemechanicalpropertieswerefoundtobeafunctionofparticlesizeandthedispersionofstarchpowderintheUPmatrix.Asignificantdecreasewasobserved intheultimatetensilestrengthandelongationpercentagewithincreasingweightfractionsofstarch powder,whilethemodulusofelasticityoftheblendshowedasignificantincrease.Othermechanicalpropertiesoftheblendssuchashardness,impactstrength,fracturetoughness,andflexural strengthalsoincreasedwithincreasingweightfractionsofstarchpowder(1%),excepttheflexural modulusat1.5%,followedbyadecreaseathigherpercentagesofstarch [54].
1.4.6 THERMOPLASTICBLENDS
XanthosandWanreportedthemeltblendingofpolypropylene(PP)withanonconventionallow molecularweightUPR(5:3PP/UPRwt.ratio)inthepresenceoforganicperoxidebyreactiveprocessing.Thereactedblendexhibitedafinerandmoreuniformmorphologyanddifferentproperties.The resultsindicatethepossibilityoftheformationofblockand/orgraftPP/UPRcompatibilizingcopolymers [55].UPRblendsofdifferentcompositionswerepreparedwithtwodifferentthermoplastics, polystyrene(PS)andpolycarbonate(PC),bymixingsolutionsofthepolymersinchloroform.Amiscibilitystudyofthesesolutionblendswascarriedoutusingsimpleandinexpensivetechniques.The UPR/PSblendwasfoundtobemisciblewhiletheUPR/PCblendwasimmiscible [56]
Hydrogenbondinginteractionsbetweenthetwocomponentsinpoly(ethyleneoxide)(PEO)/ OERblendsandPEO/cross-linkedUPRblendswereunderstoodbyFouriertransforminfraredspectroscopy(FTIR)study.Thesehydrogenbondinginteractionsareresponsibleforthemiscibilityof theblends.ThecrystallizationkineticsandmorphologyofPEOinthePEO/UPRblendwasfound tobedependentoncross-linking.Atthecrystallizationtemperature,theoverallcrystallizationrate ofPEOinthePEO/UPRblendwaslargerthanthatinPEO/OERblend [57].Lietal.usedan improvednuclearmagneticresonance(NMR)methodtomeasuretheinterphasethicknessandto interpretthephasebehavior,miscibility,heterogeneousdynamics,andmicrodomainstructureofa thermosetblendofUPRwithacotriblockpolymerofPEO-block-poly(propyleneoxide)-block-PEO (PEO-PPO-PEO).Theresultsindicatedthatthermodynamicinteractionbetweentheblockcopolymerandthecross-linkedthermosetresinisakeyfactorincontrollingthephasebehavior,domain size,andinterphasethicknessoftheseblends [58].Althoughpoly(ε-caprolactone)(PCL)wasfound tobemisciblewithuncuredpolyester/OER,itispartiallymisciblewithcrosslinkedpolyesterresin (PER).ThemiscibilityofPCLandOER/PERwasfoundtobeaconsequenceofintermolecular hydrogenbondingbetweenthecomponentsoftheblend.Theimportanceofthecontributionof entropytothemiscibilityofthermosettingpolymerblendsisalsoshownfromFTIRresults.The spheruliticmorphologyoftheblendswasremarkablyaffectedbycross-linking.BirefringentspheruliteswereobservedinuncuredPCL/OERblends,whereasadistinctpatternofextinctionrings, whichwasabsentbothinthepurePCLorintheuncuredPCL/OERblends,wasapparentinthe cross-linkedPCL/PERblends [59]
1.4.7 SIMULATIONSTUDIESONBLENDS
Ruffieretal.performedasimulationtoshowtheconnectionbetweenvoidsscatteredinsidethe UPR polyvinylacetateblendandtheblendphaseseparationmechanism [60].Theeffectofcuring temperatureonthemorphologyofUPR/styrene/PVAcblendswith5%and10%PVAccured between75 Cand150 Cwasstudied.Acocontinuousphaseseparatedstructureresultedfor10% PVAc.Aninsignificantchangeinmorphologywithcuringtemperaturewasobservedforthiscomposition [61].
Acomputersimulationmodeltoanalyzethereactioninjectionmoldingprocessofpolyurethane andUPblendshasalsobeenproposed [62].Mezzengaetal.modeledthefreeenergyofmixing duringpolymerizationinblendsofUPR,styrene,andallyletherfunctionalizedhyperbranched polyesters.TheycombinedtheFlory Hugginstheoryandgelpermeationchromatography(GPC) molecularweightmeasurementsduringmodeling.ThecurebehaviorsofUPR,phenol,andUPR/ phenolblendsweredetectedandsimulatedusingdifferentialscanningcalorimetry(DSC)and DMA.Curebehaviorwasusedtocalculateandpredictthecurerate,curetemperature,conversion, andchangesinthe Tg alongwithvariouscureordersinordertoobtaintheoptimumparametersfor processing [63].Withdynamicscanning,isothermalDSCprocedures,andBorchardt Daniels dynamicsoftware,curedatafortheUPresinwereobtained;90%oftheconversionrateat100 C beingachievedafter15minutes.However,forthephenolandUPR/phenolblends,gradually increasingthetemperaturewasfoundtobethebestforcuringaccordingtotheDSCandDMAtest results [64]
1.5 INTERPENETRATINGNETWORKSOFUNSATURATEDPOLYESTER RESIN
Thesearearelativelynewtypeofpolymerblendswhichconsistsoftwoormorecross-linkedpolymersinwhichatleastonenetworkissynthesizedinthepresenceoftheother.Althoughdifferent modificationprocessesarereported,theformationofinterpenetratingpolymernetworks(IPNs)isa promisingmethod.
1.5.1 UNSATURATEDPOLYESTERSRESIN POLYURETHANEINTERPENETRATING POLYMERNETWORKS
Mutuallypermeablesemi-IPN-typenetworksconsistingofUPRandpolyurethaneresin(PUR) (semi-IPNUPR/PUR)havebeenpreparedusinganewmethodofaddingPURtostyrene.Both resinsformdispersedphaseswithheterogeneousmicrostructures.PURseemstoaffectthemechanicalpropertiessignificantly,buttheeffectceasesonincreasingthePURcontentabove10%.The dynamicelasticitymodulusdependsonlyoncomposition [65].IPNswithfourdifferenttypesof UPRs(commerciallyavailableunsaturatedpolyester(UPE),partiallyendcappedUPE,OH-free, andhavingacetatelinkagesattheend)andPUwerecuredwithUV.Thereactionsequencewas foundtobeanimportantfactorindeterminingthephasemixing,phasemorphology,andhence,the
mechanicalpropertiesoftheIPNs.Thesimultaneousreactionofthetworeactingsystemsresulted inacocontinuousstructurethatprovidedenhancedtensilepropertiesandimpactstrengths [66]
AseriesofBaTiO3 fiberandnanopowderunfilledandfilledIPNscomposedofpolyurethane (PU)andUPRwerepreparedusingasimultaneouspolymerizationprocess.Thedampingbehaviors anddegreeofphaseseparationoftheunfilledandfilledIPNswerestronglydependentonthePU/ UPcomponentratios,typesoffiller,andtheamountofnanopowderadded.ThefilledIPNsexhibitedsynergisticeffectsondampingproperties.Performingapolarizingprocessenhancedtheproperties.Thetemperaturerangesexhibitedexcellentconsistencyofmaximumdielectriclossand dielectricconstantwithdampinglossfactor [67].
1.5.2 UNSATURATEDPOLYESTERSRESIN ACRYLATEINTERPENETRATING POLYMERNETWORKS
Polyester poly(ethylacrylate- co-styrene)IPNsweresynthesizedusingatwo-stepinsitusequential technique.Bothsemi-andfullIPNsweresynthesized.Poly(ethylacrylate-co-styrene)actsasthe rubberyphaseandpolyesterasahardphase.Withincreasingproportionsofethylacrylateinthe IPN,theelongationatbreak,toughness,andmolecularweightbetweencross-linkswashigher,but tensilestrength,modulus,tearstrength,anddensitywerelower.ThefullIPNsshowedhighertensilestrength,modulus,tearstrength,density,andhardness,butlowerelongationatbreakand toughnesscomparedtosemi-IPNs.Thesemi-IPNsshowedhighertoughnessandelongation.The extentofcross-linkingoftheelastomerhadadeterminingroleinthemechanicalpropertyprofile. Thediameterofthedomaindependedontheamountofelastomeradded [68].Acrylate-modified PURresinwasfirstpreparedandthenaddedtoUPRtoobtainanIPNthatcouldbecuredatRT. Animprovementinmiscibilityledtohigherdegreeofpenetrationandentanglement,thusresulting inimprovedmechanicalproperties [69].Aseriesofsemi-IPNsbasedondifferentcompositionsof anacyclicPEToligomerandUPRwerepreparedwithstyreneasacross-linker,MEKPasacatalyst,andcobaltnaphthenateasapromoter.ThemixturewascuredatRT.Thetensilestrengthof theIPNsdecreased,whereastheelongationatbreakincreasedwiththeconcentrationofPET oligomer [70].
1.5.3 UNSATURATEDPOLYESTERSRESIN EPOXYRESINSINTERPENETRATING POLYMERNETWORKS
SimultaneousIPNsbasedonepoxy(DGEBA)andUPwerepreparedusing m-xylenediamineand BPOascuringagents.Single Tg suggestedgoodcompatibilityofepoxyandUP.Interlockbetween thetwogrowingnetworksledtoaretardedviscosityincrease.ThehydroxylendgroupsintheUP catalyzedthecuringreactionofepoxy;leadingtorapidincreaseinviscosity.Entanglementaffected thecrackingenergyabsorptionandwasreflectedinanimprovementintoughness [71].The Tg of simultaneousIPNswasfoundtoincreasewiththeEP(epoxypolyester)content(10% 90wt.%). IPNscontaininghigherEPcontentsexhibitedhighervaluesoftan δ (max.)(Fig.1.5)andlower cross-linkingdensitiesintherubberystateprobablyduetotheplasticizationeffectoftheEPcomponentalongwiththeheterogeneousnetworkstructure [2].StudiesonthecuringkineticsofsimultaneousUP/DGEBAIPNsshowedlowertotalheatofreactioncomparedtothatobservedwhile curingpureresins.Thiscouldbeaneffectofnetworkinterlockthatcouldnotbecompensated
100EP
10UPR:90EP
30UPR:70EP
50UPR:50EP
70UPR:30EP
90UPR:10EP 100UPR
FIGURE1.5 tan δ versustemperatureofBPO/THPA-curedIPNs,BPO-curedUPR,andTHPA-curedEP.
completelybyanincreaseincuringtemperature.Incompletecuringinisothermalmodeiscaused bybothnetworkinterlockandthevitrificationofDGEBA.Therateconstantfor50/50ofUP/ DGEBAwashigherwhiletheactivationenergywaslowerpresumablyduetothecatalyticenvironmentprovidedbythehydroxylendgroupofUPintheIPN [72,73].
AseriesofIPNswithexcellentflame-retardantanddampingpropertiesweredeveloped.The flexibilityandrangeofthermaltransitionincreasedasthecontentofUPRincreasedintheIPNs whilethehomogeneitydecreased.Theheatresistance,damping,andmechanicalpropertieswereall improvedsimultaneouslywiththeadditionofplate-shapedcarbonblack(CB)intotheUPR/epoxy IPNs [74].ShinandJengalsopreparedUPR/epoxyIPNs.AseriesofIPNsbasedonUP/epoxy weredeveloped.PhaseseparationwasobservedwhentheUPRcontentwashigherthan30%.The bestmiscibilityforIPNwasobtainedforacompositionwithsimilaramountsofhydrogendonors andcarbonylgroup [75].FromakineticstudyofEP/UPRitwasfoundthattheheatresistanceof UPwasenhancedwiththeadditionofaflame-retardantorepoxyresin [76].
Aseriesoftranslucent,compatibleIPNswerepreparedbyShakeretal.usinganelastomeric amine-curedepoxyandUPR.A45%increaseintoughnesswasobservedforoneofthecompositions.Thiswasareflectionofthehomogeneousdistributionoftherubbercomponent [77].SemiIPNsofepoxyandUPRhavebeensynthesizedwithdifferentproportionsofUPR(0% 50%). Trimethylenetetraminewasusedasaroomtemperaturecuringagent.IPNswith11.1%ofUPR exhibitedimprovedmechanicalproperties.Theblendswerefurthermodifiedbyaromaticamines suchasbenzidineanddiphenylamine.Themechanicalpropertiesoftheblendmodifiedwithdiphenylaminewerefoundtobesuperior [78].
1.5.4 UNSATURATEDPOLYESTERSRESIN PHENOLANDUNSATURATED POLYESTERSRESIN NYLONINTERPENETRATINGPOLYMERNETWORKS
IPNsofUPRandseveralphenolicresoleshavebeenreportedbyAvendanoetal.TheseIPNswere foundtoshowbothphysicalandchemicalcompatibilityastheycocuresuchthattheyresultin
cocontinuousIPNs.Theparticipationoftheallylgroupsofresoleinthecross-linkingprocessof IPNscouldbeconfirmedfromthesolid-state 13C-NMRspectra [79]
Novelsemi-IPNsofUPRandnylonhavebeenproducedbymixingdifferentamountsofNylon 66oligomers(residuesofindustrialNylon66polymerization)intoUPRandheatingfollowedby cross-linking.Nylon66wasobtainedfromindustrialwaste.Threeimportantaspectsofthiswork include(1)thepossibilityofproducingnewmaterialswithimprovedimpactstrengths,(2)theplastifyingeffectofNylon66oligomersontheUPresin,and(3)ecologicallymoreimportant,thefeasibilityofreutilizingwastematerialsforproducingengineeringmaterialswithtailoredproperties [80].
1.6 UNSATURATEDPOLYESTERSRESINCOMPOSITES
Compositesareheterogenousmaterialsmadeupoftwoormorechemicallydistinctconstituents. Thebasiccomponentsareareinforcementandamatrix.Eachoftheseshouldhaveappropriate characteristicsandfunctionbothindividuallyandcollectivelysothatcompositesattainthedesired superiorproperties.Thereinforcementcontributestothestrengthandmodulustothecomposite, whilethemainroleofthematrixistotransmitanddistributestressesinthereinforcement. Reinforcementsareoftwotypes,namelyparticulateandfibers.Commercially,glassfiber(GF)reinforcedpolyestercompositesareimportantduetotheirhighstrength-to-weightratio,lowcost, andeasymanufacturingmethods.Incomparisontoparticulate-filledcomposites,manyfiber-filled compositesareanisotropicwithtremendousstrengthinonedirection;althoughuniaxiallyoriented fibercompositeshaveveryhighmoduliinonedirection,theothermoduliarelow.Thereforetoget goodpropertiesinatleasttwoorthreedirections,fiberscanberandomlyorientedsuchthatcompositesarenearlyisotropicinaplane.Inthecaseoffibersasareinforcement,italsoprovidesprotectionagainstbothfiberaberrationandfiberexposuretomoistureorotherenvironmentalconditions.
1.6.1
CommercialinterestinGF-reinforcedUPRcompositesisduetotheirhighstrength-to-weightratio, andlowcost.
E-GFcompositespreparedusingahandlayuptechniquewithconcentrationsvaryingbetween 15and60wt.%renderedexcellentmechanicalproperties. Table1.3 showstheimprovementinthe mechanicalpropertiesasafunctionoffillercontent [81] Table1.3EffectofGlassFiberofFabricatedCompositesContentsonTensileStrength
