Dioctyl Terephthalate (DOTP)
The same formula as DOP and the same two chains, with the esters moved from adjacent carbons to opposite ones. That single change removes the reproductive toxicity classification, which is why the market has moved.
Molecular Structure
What is Dioctyl Terephthalate (DOTP)?
Dioctyl terephthalate is the di(2-ethylhexyl) ester of terephthalic acid. It is an isomer of DOP in the strict sense — identical molecular formula, identical alcohol, identical molecular weight — differing only in that the two ester groups sit para to one another on the ring rather than ortho.
That difference is the entire commercial proposition. The reproductive toxicity associated with certain ortho-phthalates is attributed to the monoester formed on partial hydrolysis, and the para geometry does not produce a monoester with the same biological activity. DOTP is not classified as a reproductive toxicant and is generally not classified as hazardous under CLP.
It is made by esterifying purified terephthalic acid, or transesterifying dimethyl terephthalate, with 2-ethylhexanol. A growing volume is made by depolymerising post-consumer PET, which yields a plasticiser carrying certified recycled content — an increasingly specified attribute in packaging and automotive supply chains.
DOTP is a drop-in replacement chemically but not thermally. It fuses more slowly than DOP and needs a higher gelation temperature, so a compound switched across without adjusting the processing profile will show poor fusion, weak welds and inconsistent physical properties. Plan the trial, do not simply substitute.
Quick Reference
Key Physical & Chemical Properties
Structure & Bonding
Two ester groups on opposite carbons of a benzene ring, each carrying a branched eight-carbon chain. Identical in formula to DOP; the para arrangement is the whole difference, and it is enough to change the toxicological and regulatory outcome entirely.
Skeletal structure — para-diester with two 2-ethylhexyl chains
Structural Identity
- IUPAC NameBis(2-ethylhexyl) benzene-1,4-dicarboxylate
- Common namesDOTP, DEHT, dioctyl terephthalate
- Molecular FormulaC₂₄H₃₈O₄
- Molecular Weight390.56 g/mol
- SubstitutionPara (1,4) — the key difference from DOP
- Ester chains2-Ethylhexyl, branched C₈
- Made fromPTA or DMT + 2-ethylhexanol
- Recycled routeDepolymerised post-consumer PET
- EU classificationNot classified as hazardous
- CAS Number6422-86-2
- InChI KeySZQUEWJRBJDHSM-UHFFFAOYSA-N
Product Specifications
Chelora supplies Dioctyl Terephthalate (DOTP) in standard and custom grades. Contact us for specification sheets tailored to your process.
| Chemical name | Di(2-ethylhexyl) terephthalate |
|---|---|
| CAS Number | 6422-86-2 |
| Molecular formula | C₂₄H₃₈O₄ |
| Molecular weight | 390.56 g/mol |
| Ester content (min) | ≥ 99.50 wt% |
| Acid value as terephthalic acid (max) | ≤ 0.05 mg KOH/g |
| Colour (max) | ≤ 30 Pt-Co (Hazen) |
| Water (max) | ≤ 0.10 wt% |
| Specific gravity | 0.982 – 0.986 at 20/20 °C |
| Refractive index | 1.488 – 1.491 at 20 °C |
| Volatility / heating loss (max) | ≤ 0.15 wt% at 125 °C, 2 h |
| Free 2-ethylhexanol (max) | ≤ 0.10 wt% |
| Volume resistivity (min) | ≥ 2 × 10¹¹ Ω·cm |
| Flash point | 230 °C (closed cup) |
| Pour point | −48 °C |
| Recycled content | Declared where a PET-derived grade is supplied |
| 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 Dioctyl Terephthalate (DOTP).
Toys & Childcare Articles
The application phthalate restriction created. DOTP is the standard general purpose plasticiser for vinyl toys, teethers and childcare articles in regulated markets.
Food Contact PVC
Gaskets, closures, cling film and conveyor belting in food processing, where migration limits and food-contact approval both have to be satisfied.
Cable & Wire
Insulation and sheathing compound, with volume resistivity generally better than DOP at equal loading — an advantage rather than a compromise.
Flooring & Wallcovering
Vinyl flooring, wall covering and coated fabric, particularly for schools, healthcare and residential specification where phthalate-free is a requirement.
Automotive Interior
Instrument panel skin, door trim and sealant, where low fogging and low volatility matter as much as flexibility.
Recycled-Content Plasticiser
Grades made by depolymerising post-consumer PET, supplying certified recycled content into flexible PVC without any performance penalty.
Why source Dioctyl Terephthalate (DOTP) through Chelora Petrochem?
Verified Origin
Full origin certification and asset-backed supply chain documentation — no grey-market or off-spec material passed as prime.
Grade Flexibility
General purpose, electrical and food-contact grades supplied, plus recycled-content material with declared and certified rPET origin.
Full Documentation
CoA, SDS, REACH compliance, food-contact declarations under FDA 21 CFR and EU 10/2011, toy safety documentation, and recycled content certification where applicable.
Logistics Support
Experienced in bulk plasticiser logistics — ISO tanks, road tankers, drums and IBCs, with segregation for food-contact grades, for Indian and international delivery.
Storage & Handling Guidelines
Always refer to the full SDS before handling. The following is a summary of key requirements.
- Plan a processing trial rather than a direct substitution. DOTP gelates and fuses at a higher temperature than DOP, so a compound switched across on the old profile will under-fuse, giving weak welds, poor tensile strength and inconsistent results.
- Expect to raise plasticiser loading slightly. DOTP is marginally less efficient than DOP, so reaching the same hardness typically needs a few parts more per hundred resin — allow for that in costing rather than discovering it in the lab.
- Store in mild steel or stainless tanks at ambient. DOTP is stable and non-corrosive, and mild heating to around 40 °C eases pumping in cold conditions.
- Keep dry and clean, particularly for electrical grades. Water and ionic contamination degrade volume resistivity, which is one of DOTP's advantages over DOP and easily lost.
- Segregate food-contact and recycled-content grades with dedicated lines, and keep the recycled content documentation with the material.
- Protect from prolonged heat and air, which slowly raise the acid value through hydrolysis and degrade colour.
- Verify claims on incoming material where phthalate-free is the selling point. Cross-contamination with a phthalate plasticiser upstream defeats the purpose of specifying DOTP and is not visible on inspection.
- Contain spills and prevent release to drains and surface water, notwithstanding the favourable classification.
- Provide extraction where plasticiser is heated during compounding or calendering, since fume and mist are generated at process temperature.
Hazard Summary
Classification: DOTP is generally not classified as hazardous under CLP. It is not a reproductive toxicant, is not an SVHC, and carries none of the restrictions applied to DEHP. Acute toxicity is very low by all routes. This favourable position is the reason to specify it.
Do not assume it is a drop-in on the process side: chemically it substitutes for DOP one for one, but it fuses more slowly and needs a higher gelation temperature. Under-fusion produces compound that looks acceptable and fails on tensile strength, weld strength and long-term flexibility. This is the most common problem reported on conversion and it is entirely avoidable with a trial.
Slightly lower efficiency: a few more parts per hundred resin are typically needed to reach the same Shore hardness as DOP. Marginal, but it belongs in the cost comparison rather than being discovered later.
Migration still occurs: DOTP is not chemically bound to the PVC and will migrate over time, though its volatility is lower than DOP's and permanence is generally better. Food-contact applications still require migration testing against the applicable limits — a favourable classification is not the same as an unrestricted one.
Verify phthalate-free claims: where DOTP is specified precisely to satisfy a phthalate restriction, upstream cross-contamination defeats the purpose and cannot be detected by inspection. Segregated handling and analytical confirmation on incoming material are worth the effort.
Fire: a combustible liquid with a flash point of 230 °C. Not a flammable liquid and not regulated for transport, but heated handling during compounding should be assessed.
Environmental: low acute aquatic toxicity and low water solubility, but persistent enough that releases should be contained rather than discharged.
PPE minimum: safety glasses and gloves for routine handling, with extraction where plasticiser is heated.
Consult the full SDS and the grade technical data sheet, and confirm food-contact status for your specific application before use.
Frequently Asked Questions
Technical and commercial questions about Dioctyl Terephthalate (DOTP) sourcing and specifications.
What is DOTP used for?
Flexible PVC across the same range as DOP, with the emphasis on applications where phthalate restrictions apply. Toys and childcare articles are the segment the restrictions created. Food contact PVC — gaskets, closures, cling film, conveyor belting — is another. Beyond those, DOTP goes into cable insulation and sheathing, vinyl flooring and wall covering specified as phthalate-free, and automotive interior trim where low fogging matters.
How does DOTP compare with DOP in practice?
On regulatory grounds it wins outright: DOTP is not classified as a reproductive toxicant and carries none of DEHP's restrictions. On performance the picture is mixed but favourable. Permanence is better — lower volatility means less plasticiser loss and less fogging over the life of the article. Volume resistivity is generally higher, which is an advantage in cable. Low-temperature flexibility is comparable or slightly better. Against that, plasticising efficiency is marginally lower, so a few more parts per hundred resin are needed for the same hardness, and — the point that catches people out — it fuses more slowly and needs a higher processing temperature.
Why is DOTP not classified when DOP is, given they have the same formula?
Because the toxicity depends on geometry rather than composition. The reproductive effects associated with certain ortho-phthalates are attributed to the monoester that forms when one ester chain hydrolyses off in the body; that monoester interferes with testosterone production in the developing foetus. The para arrangement in a terephthalate produces a monoester with a different shape that does not have the same biological activity. So moving the two ester groups from adjacent ring carbons to opposite ones — with no change to the molecular formula, the alcohol or the molecular weight — changes the toxicological profile and therefore the regulatory classification completely. It is a striking illustration that structure, not composition, determines biological effect.
What has to change when converting a compound from DOP to DOTP?
Primarily the thermal profile. DOTP solvates PVC more slowly, so dry blend times, gelation temperature and fusion temperature all need to rise — typically by five to fifteen degrees depending on the process, more in calendering than in extrusion. Under-fused compound is the failure mode, and it presents as poor tensile and weld strength rather than as anything obvious in appearance. Secondly, expect to add a few parts per hundred resin to hit the same hardness. Thirdly, if the compound contains a secondary plasticiser or a stabiliser system tuned for DOP, check the interaction. None of this is difficult, but it is a formulation trial rather than a substitution.
Can DOTP be made from recycled PET?
Yes, and it is one of the more elegant routes in plastics recycling. Post-consumer PET is depolymerised — usually by glycolysis or methanolysis — to recover the terephthalate unit, which is then esterified with 2-ethylhexanol to give DOTP. The resulting plasticiser is chemically identical to virgin material and can carry certified recycled content. It appeals particularly where a brand has recycled content targets across its packaging or automotive supply chain but limited routes to use rPET directly. If recycled content is being claimed, the chain of custody certification should accompany the material.
What documentation does Chelora provide?
Every shipment includes a Certificate of Analysis covering ester content, acid value, colour, water, specific gravity, refractive index, volatility, free 2-ethylhexanol and volume resistivity; a Safety Data Sheet to GHS and REACH format; REACH compliance confirmation; food-contact declarations under FDA 21 CFR and EU Regulation 10/2011 and toy safety documentation where applicable; recycled content certification for PET-derived grades; an origin certificate; and destination-market certificates where required.
Request a quote or specification sheet
Talk to Chelora's sourcing team about Dioctyl Terephthalate (DOTP) grade, volume, logistics, documentation, and lead times. We respond within one business day.
