PET Resin
Rigid enough to hold five bars of carbonation in a wall you can dent with a thumbnail. It also hydrolyses in its own melt, so every gram has to be dried before it goes near an extruder.
Molecular Structure
What is PET Resin?
PET is the polyester of terephthalic acid and ethylene glycol. The terephthalate unit is flat and rigid, the glycol segment is short and flexible, and the alternation between them produces a chain that crystallises slowly but thoroughly. That slow crystallisation is the whole trick behind a bottle: the preform is quenched amorphous and clear, then stretch blown, and the biaxial orientation develops strain-induced crystallinity that gives strength and gas barrier while staying transparent.
It is made in two stages. Terephthalic acid and glycol are esterified — or dimethyl terephthalate and glycol transesterified — to bis-hydroxyethyl terephthalate, which is then melt polycondensed under vacuum over an antimony, titanium or germanium catalyst. Fibre and film grades leave the melt line at final molecular weight. Bottle grade goes on to solid state polymerisation, where the chip is held below its melting point under vacuum or nitrogen for hours until the chains grow further and residual acetaldehyde is stripped out.
Molecular weight is quoted as intrinsic viscosity rather than melt flow, and it is the number that defines the grade. Fibre sits around 0.62, film around 0.64, water and carbonated drinks bottles at 0.76 to 0.84, and industrial yarn above 0.95.
PET must be dried to below about 50 parts per million of moisture before processing. Water in the melt hydrolyses the ester backbone, intrinsic viscosity falls, and the loss is permanent — no amount of downstream adjustment recovers it. A dryer that is not working is the most common cause of PET production failure, and it fails silently.
Quick Reference
Key Physical & Chemical Properties
Structure & Bonding
A rigid, flat terephthalate unit alternating with a short flexible glycol segment. That alternation is what lets PET crystallise under stretch rather than on cooling — the basis of a bottle that is both clear and strong.
Repeat unit — terephthalate diester linked through ethylene glycol
Structural Identity
- PolymerPoly(ethylene terephthalate)
- Repeat unit(C₁₀H₈O₄)ₙ
- Repeat unit mass192.17 g/mol
- Built fromTerephthalic acid + ethylene glycol
- LinkageAromatic diester
- CrystallisationSlow — strain-induced on stretch blowing
- Molecular weight measureIntrinsic viscosity, dL/g
- Bottle grade routeMelt polycondensation then SSP
- Key vulnerabilityHydrolysis of the ester backbone
- CAS Number25038-59-9
- Specified byIV, DEG, COOH ends, colour, AA
Product Specifications
Chelora supplies PET Resin in standard and custom grades. Contact us for specification sheets tailored to your process.
| Polymer | Poly(ethylene terephthalate) |
|---|---|
| CAS Number | 25038-59-9 |
| Repeat unit | (C₁₀H₈O₄)ₙ |
| Intrinsic viscosity — fibre grade | 0.60 – 0.68 dL/g |
| Intrinsic viscosity — film grade | 0.60 – 0.70 dL/g |
| Intrinsic viscosity — bottle grade | 0.76 – 0.86 dL/g |
| Intrinsic viscosity — industrial yarn | 0.90 – 1.05 dL/g |
| Diethylene glycol content | 1.0 – 1.6 mol% |
| Carboxyl end groups | 20 – 40 meq/kg |
| Melting point (DSC) | 250 – 260 °C |
| Colour L* (min) | ≥ 78 |
| Colour b* | −2.0 to +2.0 |
| Acetaldehyde in chip (max) | ≤ 1.0 ppm bottle grade |
| Acetaldehyde generation (max) | ≤ 8 ppm under standard test |
| Moisture as supplied (max) | ≤ 0.30 wt% — must be dried before use |
| Antimony (as catalyst) | 180 – 250 ppm; Ti and Ge grades available |
| Ash (max) | ≤ 0.05 wt% |
| Chip weight | ≈ 15 – 20 mg, uniform |
| Food contact | FDA 21 CFR and EU 10/2011 declarations available |
| Transport classification | Not regulated as dangerous goods |
Downstream Applications & Derivatives
Key derivative chains and industrial uses of PET Resin.
Bottles & Containers
Carbonated soft drinks, water, edible oil and hot-fill containers, using 0.76 to 0.84 IV chip stretch blown from injection moulded preforms.
Polyester Fibre
Staple fibre and filament yarn for apparel, home textiles and nonwovens. Polyester is the highest-volume textile fibre in the world and PET is what it is.
BOPET Film
Biaxially oriented film for flexible packaging, lamination, electrical insulation, imaging and solar backsheets — exceptional strength and dimensional stability at low gauge.
Sheet & Thermoforming
APET and PETG sheet for thermoformed trays, clamshells, blister packs and deli containers, where clarity and stiffness both matter.
Industrial Yarn
High IV grades for tyre cord, seat belts, conveyor belting, ropes and geotextile, where tenacity and dimensional stability under load are the specification.
Recycled PET
Bottle-to-bottle recycling by washed flake plus solid state polymerisation, and chemical routes via glycolysis or methanolysis for contaminated and coloured streams.
Why source PET Resin through Chelora Petrochem?
Verified Origin
Full origin certification and asset-backed supply chain documentation — no grey-market or off-spec prime passed as prime.
Grade Flexibility
Bottle, fibre, film and industrial yarn grades supplied. We match on intrinsic viscosity, DEG content, carboxyl end groups and acetaldehyde, not on IV alone.
Full Documentation
Technical data sheet, CoA including IV, acetaldehyde and catalyst metals, SDS, REACH compliance, and food-contact declarations with migration data for bottle grades.
Logistics Support
Experienced in polymer resin logistics — 25 kg bags, jumbo bags, containerised and bulk silo delivery with moisture-barrier packaging and pellet-loss controls, for Indian and international delivery.
Storage & Handling Guidelines
Always refer to the full SDS before handling. The following is a summary of key requirements.
- Dry before every processing run, without exception. PET must reach below about 50 ppm moisture for bottle grade and 100 ppm for most other applications — typically four hours at 160–170 °C in a desiccant dryer with a dew point of −40 °C or lower.
- Verify the dryer rather than trusting it. Check dew point and outlet temperature on every shift; a failed desiccant bed or a leaking return line degrades resin continuously while the process appears normal.
- Keep bags and silos sealed. PET chip picks up moisture from ambient air within hours of opening, and undried resin already at 0.3% water will lose significant intrinsic viscosity in the extruder.
- Crystallise before drying where the grade requires it. Amorphous chip and recycled flake soften and agglomerate in the dryer hopper if taken straight to drying temperature.
- Control melt temperature and residence time. PET generates acetaldehyde thermally, and in water and carbonated drinks the resulting off-taste is detectable at very low levels regardless of how clean the chip was.
- Segregate bottle grade from fibre and film grades. IV, catalyst system and acetaldehyde specification all differ, and cross-contamination is not recoverable in a food-contact chain.
- Contain pellets rigorously. Spilled chip travels through drains into watercourses and is a recognised marine litter source — catch trays, drain screens and Operation Clean Sweep procedures at every transfer point.
- Ground and bond pneumatic conveying, and control fines and angel hair, which cause gels, bridging in hoppers and dust explosion risk.
- Treat molten polymer as a serious thermal burn hazard at 270–290 °C, and provide extraction at the die where acetaldehyde and oligomer fume are generated.
Hazard Summary
Classification: PET resin is not classified as hazardous under CLP. It is inert, non-toxic and the dominant food and beverage packaging polymer worldwide. The risks are process-related and regulatory rather than toxicological.
Hydrolysis is the defining process risk: water in the melt cleaves the ester backbone and lowers intrinsic viscosity permanently. A preform moulded from inadequately dried resin looks acceptable and fails on burst pressure or stress cracking later. Drying is a quality control, and a dryer failure is a silent one.
Acetaldehyde: PET generates acetaldehyde by thermal degradation during processing. It is not toxic at the levels involved, but it migrates into the contents and gives still water in particular a detectable sweet off-taste. Bottle grade chip is held at or below 1 ppm and the specification also covers how much the resin generates under a standard melt test — both figures matter, and the second is the one processing conditions can ruin.
Catalyst residues: most PET is polymerised over an antimony catalyst, leaving roughly 200 ppm antimony in the resin. Migration into contents is far below regulatory limits under normal conditions, but antimony has attracted scrutiny in some markets and titanium and germanium catalysed grades exist where a customer or jurisdiction requires them.
Recycled content obligations: the EU Single-Use Plastics Directive requires PET beverage bottles to contain at least 25% recycled content from 2025, rising to 30% for all plastic beverage bottles from 2030, and comparable mandates exist elsewhere. Anyone contracting virgin PET for a beverage chain should be planning the rPET side of that supply at the same time.
Thermal burns: molten PET at 270–290 °C adheres to skin and retains heat. Purging and die work need forearm and face protection.
Dust, fines and pellet loss: chip fines are combustible and can form explosible clouds; spilled pellets persist in the marine environment. Both are controlled by containment discipline at transfer points.
PPE minimum: safety glasses and gloves for chip handling; heat-resistant gloves, arm protection and face shield for work on molten material.
Consult the full SDS and the grade technical data sheet for drying and processing conditions, and confirm food-contact status and recycled content obligations for your market before use.
Frequently Asked Questions
Technical and commercial questions about PET Resin sourcing and specifications.
What is PET used for?
Bottles and containers for carbonated drinks, water, edible oil and hot-fill products are the highest-profile use. Polyester fibre is larger by volume — staple and filament for apparel, home textiles and nonwovens. Beyond those, biaxially oriented PET film for flexible packaging, lamination and electrical insulation; APET and PETG sheet for thermoformed trays and clamshells; and high IV industrial yarn for tyre cord, seat belts and geotextile.
What is intrinsic viscosity and how do I choose a grade?
Intrinsic viscosity is a dilute-solution measurement that tracks molecular weight, quoted in decilitres per gram, and on PET it does the job melt flow index does for polyolefins. Higher IV means longer chains, more melt strength, better mechanical performance and harder processing. As a rough guide: 0.60 to 0.68 for fibre, around 0.64 for film, 0.76 to 0.80 for water and carbonated bottles, 0.80 to 0.84 for hot fill and larger containers, and 0.90 and above for tyre cord and industrial yarn. Specifying IV alone is not enough — diethylene glycol content affects melting point and dye uptake, and carboxyl end groups affect hydrolytic stability in service.
Why must PET be dried before processing?
Because the ester backbone hydrolyses in the melt. PET is mildly hygroscopic and picks up moisture from the air, and at 280 °C that water attacks the chain and cuts it, lowering intrinsic viscosity irreversibly. A drop of 0.02 dL/g is enough to compromise a bottle's burst strength. The standard requirement is below 50 parts per million moisture for bottle grade, which means four hours or so at 160 to 170 °C in a desiccant dryer running at a dew point of −40 °C or lower. The insidious part is that the process gives no visible warning: preforms mould normally, look normal, and fail later. Checking dryer dew point every shift is the control.
What is acetaldehyde and why does it matter for water bottles?
Acetaldehyde is a small molecule generated when PET degrades thermally during melting and moulding. It is not a toxicity concern at the concentrations involved, but it has an extremely low taste threshold in water — low enough that consumers detect it as a faint sweet or fruity off-note in still water. Carbonated drinks and flavoured products mask it; plain water does not. Bottle-grade chip is therefore stripped during solid state polymerisation to 1 ppm or below, and the specification also includes an acetaldehyde generation test showing how much the resin produces under standard melt conditions. Running the injection unit too hot or with too long a residence time creates fresh acetaldehyde regardless of how clean the chip arrived.
What are the recycled content requirements I should know about?
In the EU, the Single-Use Plastics Directive requires PET beverage bottles to contain a minimum of 25% recycled content from 2025 and all plastic beverage bottles to reach 30% from 2030, with the Packaging and Packaging Waste Regulation adding further targets. Several other jurisdictions, including a number of US states, have adopted their own minimum recycled content rules on beverage packaging. The practical consequence for a virgin PET buyer in the beverage chain is that rPET supply, and the food-contact approval behind it, needs to be contracted alongside the virgin material rather than treated as a separate problem later.
What documentation does Chelora provide?
Every shipment includes the grade technical data sheet, a Certificate of Analysis covering intrinsic viscosity, diethylene glycol content, carboxyl end groups, melting point, colour L* and b*, acetaldehyde in chip and on generation, moisture, catalyst metals and ash; a Safety Data Sheet to GHS and REACH format; REACH polymer compliance confirmation; food-contact declarations under FDA 21 CFR and EU Regulation 10/2011 with migration data for bottle grades; an origin certificate; and destination-market certificates where required.
Request a quote or specification sheet
Talk to Chelora's sourcing team about PET Resin grade, volume, logistics, documentation, and lead times. We respond within one business day.
