Comparison and Analysis of PET and PETG Material Properties
Basic Definitions and Chemical Composition
Polyethylene terephthalate (PET) is a thermoplastic polyester material made from terephthalic acid (TPA) or dimethyl terephthalate (DMT) with ethylene glycol (EG) through a condensation reaction. This material was first invented by British chemists Whinfield and Dickson in 1941, and after decades of development, it has become one of the most widely used plastic materials globally. The molecular chains of PET have high regularity, allowing them to form crystalline regions that give the material excellent mechanical properties and thermal stability.
PETG (Polyethylene terephthalate glycol) is a copolymer modified version of PET, chemically known as cyclohexane dimethanol copolyester. Compared to standard PET, during production, 1,4-cyclohexanedimethanol (CHDM) is added as a third monomer; this structural change significantly affects the crystallization performance of the material. The introduction of CHDM disrupts the regularity of the PET molecular chain, making PETG an amorphous material with many unique performance advantages.
Environmental Protection and Food Safety Characteristics Comparison
In terms of environmental protection and food safety, PETG shows significant advantages. It fully complies with U.S. FDA standards for food contact materials, meaning it can be safely used in food packaging without harmful substance migration. In contrast, while standard PET also has FDA certification, there may be risks associated with trace oligomers leaching out under certain high-temperature applications.
From a sustainability perspective, the production process for PETG is more environmentally friendly. Traditional processes for producing PET involve energy-intensive steps like solid-state polymerization; however, the synthesis route for PETG is relatively simplified with lower energy consumption. Additionally, despite multiple recycling treatments maintaining good physical properties makes it an important choice in current global plastic sustainability strategies.
Differences in Physical Properties and Mechanical Characteristics
The most notable feature of PET materials is their excellent mechanical strength and rigidity. Biaxially stretched films can achieve tensile strengths exceeding 200 MPa—far surpassing most common plastics—and its elastic modulus typically ranges between 2-4 GPa making it an ideal engineering plastic choice. However，the impact toughnessofPETis relatively low，especially at low temperatures where brittle fracture easily occurs limiting its application scope in some areas.
While retaining excellent rigidity similar to thatofPET,PETGsignificantly improves toughness performance.Its notched impact strength can reach3-5 times thatofPETand maintains good impact resistance even at -40℃low temperature environments.PETGs bending modulusis approximately2 .1 GPa slightly lower than standardPETbut this moderate reduction enhances processing capabilitiesand product comfort notably.PETGalso exhibits exceptional stress crack resistance which makesit particularly suitablefor manufacturing structural components requiring long-term load-bearing capacity.
Thermal Performance & Processing Characteristics Comparison
nThe melting temperature rangeforP ETtypically liesbetween250-260℃with aglass transitiontemperature(Tg )around75℃This higher melting pointandTg confergood heat resistanceonPE Tproducts butalso poseprocessing challenges .Before processing ,P ETmust undergo strict drying treatment(usually driedat120-140 ℃for4 -6 hours),otherwise hydrolytic degradationmay occur easily.Additionally ,the crystallization rateofP ETis slowrequiring precise control over cooling conditionsduring processingto achieveidealcrystallinity . n nConversely ,thermalperformance characteristics differ significantlyin P E TG.Due toitsamorphous nature,P E TGdoesnot exhibitdistinctmeltingpoint ;softeningtemperature hovers around85 ℃This characteristic simplifiesprocessing since no need existsfor controllingcrystallinity issues.Theprocessing window widens considerablyallowing melt temperaturesflexiblyadjustedwithin220-260℃range.Comparedto P ET,P E TGexhibitslower moisture absorptionmakingdrying requirementsrelativelylooser(typicallyonly60 -80 °Cfordrying3 -4hours ),thereby reducingenergyconsumptionandcomplexitiesduringproductionprocesses . n n ### Optical Performance & Appearance Presentation nOpticalproperties representoneofthekey distinctionsbetween P ETandP E TG.StandardP Ematerials appear translucentwithout specialtreatment due tothe presenceofboth crystalline&amorphous structurescausinglight scattering.Although transparent productscanbe producedthroughrapidcooling,this transparencyoften deterioratesupon subsequent heatingdue toc rystallizationoccurring.PE T Gonother hand showcases outstandingopticalcharacteristics owingtototalamorphousstructure yieldingglass-like transmittance ratesover90% unaffectedbytemperature changes.Likewise,the haze value remainsbelow1%,color difference ΔE below0 .5Theseexcellent opticalmetrics positionPE T Gas apremierchoiceformid-range transparentpackagingaswellasdisplay equipment.Furthermore,P E Tgainsenhanced surface glossiness renderingproduct appearance refinedandsophisticated.In summary: n# Main Application FieldAnalysisPetmaterials dominatepackaging sectors accountingforapproximately70%globaloutputusedtomakebeverage bottles.Two-litercarbonated drinkbottles arealmostentirelymadefrom PE Twhich success stemsfromPE Ts superiorcost-effectiveness,greatgas barrierpropertie s,andmaturedmanufacturingtechniques.Beyondthis sector,itfinds extensiveapplicationsinfilm packaging(particularlybiaxialstretchBOPETfilms),synthetic fibers(polyester),andanengineeringplasticdomain.Recent yearswitness rapidgrowth inthe marketoffood traysformedviaheatforming techniques capable oftoleratingoven temperaturesupwards220°C.PE Tgainsbroader applicability acrossdiverse fields.Inmedical devices area,dueits remarkabletransparency chemicalresistance gamma-ray sterilizabilitywidely utilizedproducinginfusion bottles,pill containers,surgical instrumentpackaging.Consumer goods utilizePE Tinvarious forms includingcosmeticcontainers stationeryitems toycomponents.Buildings employ PE Trigid sheets constructpartitions skylights etc.Notably,in recenttimesmarket growthsurged within3D printing realmowingtoexcellentinterlayer adhesionminimalshrinkage renderingitideally suitedfused deposition modeling(FDM).ProcessingTechnologyKeyPointsTypicalmethods include injection molding extrusion blow molding.For injectionmolding,melttemperaturesgenerallymaintained270–290°Crangewhile moldtemp stays140–160°Cpromotingcrystal formation.Blow-molding technique holds particularimportancewhere stretch-blow technology produces lightweight containers boasting superbmechanical attributes.Carefulattention mustpay attentiontodryconditionssince residualmoisture exceeding0 .02%could leadseriousmaterialdegradation.Conversely,theprocessassociatedwithPT-Gissimpler.Melting temperaturesshouldremain230–250°Crangewith molds set20 –50 °Cadequately facilitatingproduction.Processingencompassesextrusion methods yieldingrigid sheet/filmstypicallyset220–240°.UnlikestandardPT-Gno precisioncontrol required duringthermoforming resulting wideroperational windows drasticallyreducingdefect rates.Additionally ,laser cutting CNC machining second-processing approaches suit well enablingcompetitive edge small-batchcustomized productions.【MarketDevelopmentTrendsProspects】Asglobalenvironmentalregulations tighten challenge sustainabledevelopment emerges confronting PT.Materialrecyclingtechnologies advancements presentnewopportunitiesparticularlyenzymaticrecycling technologies promisingunlimitedcircular utilizationpotential.Inapplicationfrontspecialty grades flame-retardant UV-resistant expandingelectronic automotive markets prospects.Growthprojectedat6%-8 %annually drivencontinuouslyexpandingmedical packaging sector risingconsumer electronics demandhigh-endtransparentmaterials.Newcopolymermodified variants suchasheat-resistantPT-GHT anti-staticPT-GES expand potentialusesNoteworthyprogress achievedbiobased PT-GR&D might pavewaytowardssignificantalternativesagainsttraditionalpetroleum-basedoptions.