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Chain Extenders, SSP Accelerators, Nucleating agents for pet

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Chain extenders are used for used for improving the melt-strength for EBM grade PET and also used in PCR PET flakes moulding to minimize the IV drop.
SSP accelerators are used to reduce the SSP time by increasing IV fast
Hope the document may help for Polyester R&D chemist

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Chain Extenders, SSP Accelerators, Nucleating agents for pet

  1. 1. 25.05.2015 CHAIN EXTENDERS Chainextenders(orcouplingagents) canserve to reversethe MW damagecaused by hydrolysisof polyestersor can modify therheology of the polymerto increaseits melt strength. Pyromelliticdianhydride (PMDA) The mostcommon chain extendersarethe dianhydrides (alsoknownastetracarboxylicdianhydrides). The most commonof these ispyromelliticdianhydride(PMDA).The lattercanbe usedinsynergistic combinationswithhinderedphenolicaromaticphosphatessuchasIRGANOX1425 manufacturedby CibaGeigyThe hinderedphenolicaromaticphosphateisusedatlevelsof 0.1–2.5 wt%.The hindered phenolicaromaticphosphate isanadvantageousco-synergistsince itservesbothasa solid-state- polymerizationcatalyst andaheatstabilizertoprotectthe PET fromoxidationduringsolid-state polymerization. Anotherhighlyeffectchainextenderistrimelliticanhydride (TMA) whichgivesrise tobranchingof the PET structure. Figure 14.1 Reactionof pyromelliticdianhydride (PMDA) chainextenderwithPETendgroups(hydroxyl and carboxylicacidgroups) togive chainextensionandbranchingof PET
  2. 2. PMDA isan effective chainextensionadditive forthermoplasticpolyesterssuchasPET andPBT. It is suitable forthe followingapplications:  Enhancementof the intrinsicviscosityof PETand PBT  Reactive extrusionof PETand PBT  Melt strengthenhancement of PETand PBT for the productionof blownpolyesterfoams  As a meltviscosityandmelt-strength-enhancingadditive formodifyingPETforfilmblowingand extrusion blowmoulding applications  Tensile strengthenhancementof PETandPBT for strappingapplicationswithoutthe needfor solid-state polycondensation  Upgradingof recycledPETflake toresinsuitable forbottlingapplications(>0.80dL/g)  As an additive toreduce the time necessaryforsolid-phase polymerizationof PETandPBT resins  To increase the elongational viscosityof PETandPBT resinsbyfacilitatingextendedand branchedarchitectures One of the maincommercial usesof PMDA is to improve the meltstrength PHENYLENEBISOXAZOLINE Both 1,3-phenylenebisoxazoline (1,3-PBO)and1,4-phenylenebisoxazoline (1,4-PBO) are effectivechain extenders PBO isa veryreactive compoundtowardsPETcontainingcarboxyl endgroupsbutnothydroxyl end groups. PBO alsoacts as a carboxyl groupscavengerandindoingso increasesthe hydrolyticstabilityof the resultantPET.
  3. 3. SSP ACCELERATOR Solid-state polycondensationof PETis bothtime-consumingandenergy-intensive.Recently,additives have beendevelopedtoaccelerate thisprocess SuchadditivesenablePETwitha veryhighIV to be producedat reducedresidence timesinthe solid-state reactor,withenhancedoutputsandata reduced cost. Suchadditivesacceleratethe IV enhancementof PETat low cost. One suchSSP acceleratoris Irgamod1425 whichwhenusedinPET at levelsof between0.1–0.5 wt%givesanSSP accelerationof approximately50% Effectof a commercial solid-statingaccelerator(Irgamod1425) on the rate of intrinsicviscosity enhancementof PET Irgamod1425 alsocontributes to reduced yellowingofthe PET resin
  4. 4. Nucleating agents for PET Quickcoolingof the PET meltresultsinthe formationof small spherulitesbutthe crystallinity,however, remainslowbecause the polymerispractically‘frozen’initsamorphousstate.Slow coolingof the PET, on the otherhand,leadsto a highdegree of crystallinity;however,the spherulitesgrow toa large size at whichoptimummechanical propertiesare notattained.Inaddition,anunevenspherulitesize distributionresults.Achievingahighdegree of crystallinityandsmall spherulitesinPETsimultaneously requiresthe use of nucleatingagentsandcrystallizationpromoters. NucleatingagentsinPETserve twomainfunctions,asfollows: • To induce asmall and regularcrystalline structure. • To suppresslarge crystal growthwhichcauses brittleness. Additional functionsof the nucleatingsysteminclude the following: • To decrease demouldingtime (i.e.decrease cycle time forthe part). • To allowthe material tocrystallize atauniformrate in the mouldwhichtendstoresultinlower moulded-instresses. The nucleatingsystemforcommercial PETinjectionmouldingcompoundsisthustypicallybasedona three-componentpackage comprisingthe following: (i) sodiumstearate (chemical nucleatingagent) (ii) sodiumionomer(melt-miscible nucleatingagent) (iii) poly(etherester) (plasticizertofacilitate chainfolding) Dr. K MuniswamyReddy

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