Dioctyl terephthalate (DOTP, CAS 6422-86-2) is a high-temperature-resistant, non-phthalate plasticizer widely used in PVC cables, automotive interiors, food packaging, and synthetic leather. As one of the most cost-effective phthalate-free plasticizers, DOTP offers excellent durability, low volatility, and outstanding compatibility with PVC.
This DOTP plasticizer guide explains how DOTP is synthesized through esterification, its functional groups, mechanism of action as plasticizer, key applications, consumption calculation, and how it compares with other plasticizer esters. This guide is perfect for engineers, formulators, and researchers seeking reliable, in-depth information about dioctyl terephthalate.
What is Dioctyl Terephthalate (DOTP)
Dioctyl terephthalate (DOTP) is an aliphatic-aromatic diester derived from terephthalic acid. In the plasticizer industry, DOTP specifically refers to Di-(2-ethylhexyl) terephthalate (DEHT), rather than di-n-octyl terephthalate. As an eco-friendly, non-phthalate plasticizer, DOTP serves as a primary plasticizer in PVC wire and cable insulation, as well as in automotive interior materials.
If you are looking for technical specifications, this plasticizer guide also directs you to our DOTP Product Page for specifications and bulk order options.
How DOTP is Synthesized
DOTP is produced through an acid-catalyzed esterification of terephthalic acid (or dimethyl terephthalate) with 2-ethylhexanol, followed by purification. The key steps are:
- Esterification: Reaction of raw materials to form DOTP and water.
- Dehydration: Removal of water via azeotropic or vacuum distillation.
- Neutralization & Washing: Operators neutralize and wash out the acid catalyst.
- Purification: The process removes unreacted alcohol under vacuum and filters the product (decolorizing if necessary).
- Quality Control: Technicians test the final product (e.g., by GC, acid value) before storing and packaging it.
Synthesis Flowchart
Raw Materials → Pre-treatment → Esterification (Catalyst, Δ) → Dehydration → Neutralization/Washing → Alcohol Removal → Filtration → QC → Packaging
Reaction Equation
C₆H₄(COOH)₂ + 2C₈H₁₇OH → C₆H₄(COOC₈H₁₇)₂ + 2H₂O
(Terephthalic Acid + 2-Ethylhexanol → DOTP + Water)
Functional Groups of DOTP
Functional Groups of DOTP
The DOTP plasticizer guide also explores its molecular structure. DOTP is a diester formed from terephthalic acid and 2-ethylhexanol. Its key functional groups define its properties:
Ester Groups (-COO-): The most critical group. Each DOTP molecule has two, connecting the benzene ring to the branched alkyl chains.
Benzene Ring (Aromatic Ring): Provides structural stability and polarity.
Branched Alkyl Chains: Long, non-polar groups that separate polymer chains to impart flexibility.
DOTP achieves an optimal balance: its polar ester groups and benzene ring anchor it to the PVC matrix, while its non-polar, branched alkyl chains act as spacers, providing flexibility.
Mechanism of Action of DOTP as PVC Plasticizer
DOTP (Dioctyl Terephthalate) works by integrating into the PVC matrix and separating the polymer chains, which reduces the glass transition temperature (Tg) and imparts flexibility. This process occurs in four key steps:
- Compatibility and Mixing: During high-temperature processing (150-180 °C), the polar ester groups of DOTP are attracted to the chlorine atoms on PVC chains via dipole-dipole interactions. This allows DOTP to uniformly penetrate and form a homogeneous mixture with the PVC.
- Chain Separation and Shielding: The bulky, non-polar alkyl chains of DOTP physically force the PVC polymer chains apart. This separation increases the free volume between chains and shields the natural dipole-dipole interactions (“secondary crosslinks”) that make rigid PVC hard.
- Enhanced Mobility and Reduced Tg: By separating and shielding the chains, DOTP acts as a molecular lubricant. This enables PVC chains to move past each other easily, drastically lowering the material’s Glass Transition Temperature (Tg). As the Tg falls below room temperature, the PVC becomes flexible.
- Formation of a Stable Network: Upon cooling, the DOTP molecules are permanently immobilized within the PVC matrix. Held in place by polar interactions, their alkyl chains maintain polymer separation, resulting in a permanently flexible material.
Applications of DOTP
- PVC cable compounds
- Automotive interiors
- Food packaging
- Coatings, synthetic rubber
Our DOTP plasticizer guide details how DOTP improves heat resistance, reduces volatility, and maintains gloss in coatings, making it one of the most versatile non-phthalate plasticizers.
| Application | Benefits |
| PVC Cable Compounds | Heat resistance up to 70 °C, low volatility |
| Automotive Interiors | Low fogging, durable, odor-free |
| Food Packaging | FDA/EU compliant, phthalate-free |
| Synthetic Leather/Films | High flexibility, good migration resistance |
| Coatings & Adhesives | Good compatibility, maintains gloss |
| Synthetic Rubber | Improves processing and flexibility |
DOTP Consumption Calculation–DOTP plasticizer guide
This guide provides the theoretical mass ratios and molecular calculations for DOTP production, essential for plant engineers to plan raw material usage and optimize efficiency.
Theoretical Mass Ratio Summary
The stoichiometric reaction requires 1.000 kg of PTA and 1.568 kg of 2-Ethylhexanol (2-EH) to produce 2.352 kg of DOTP.
| Component | Molecular Weight (g/mol) | Molar Ratio | Mass Ratio (kg/kg PTA) | Mass for 1 ton DOTP (kg) |
|---|---|---|---|---|
| Terephthalic Acid (PTA) | 166.13 | 1 | 1.000 | 425.2 |
| 2-Ethylhexanol (2-EH) | 130.23 | 2 | 1.568 | 666.7 |
| DOTP | 390.56 | 1 | 2.352 | 1000 |
Theoretical vs. Practical Planning
| Parameter | Theoretical | Practical (Industrial) |
|---|---|---|
| Molar Ratio (PTA : 2-EH) | 1 : 2.0 | 1 : 2.2 to 1 : 2.5 |
| Mass Ratio (2-EH / PTA) | 1.568 | Initial Charge: ~1.85 Net Consumption: ~1.60 – 1.65* |
| Key Consideration | Perfect stoichiometry | Uses excess alcohol, which is recovered and recycled. |
**Net consumption accounts for recovery losses (~2-5%).*
Conclusion: For production planning, we recommend an initial charge of ~1.85 kg of 2-EH per kg of PTA. After recovery, the net consumption is closer to 1.60 – 1.65 kg of 2-EH per kg of PTA.
DOTP vs Other Plasticizers-Guide
The DOTP plasticizer guide compares DOTP with DOP, DINP, and TOTM.
| Plasticizer | Advantages | Limitations |
| DOTP | Non-phthalate, good performance | Slightly higher cost |
| DOP (DEHP) | Low cost, good efficiency | Restricted in many regions |
| DINP | Good all-around properties | Some regulatory concerns |
| TOTM | Best high-temp stability | More expensive, viscous |
Why DOTP is Superior to Traditional Phthalates
- Lower Volatility & Migration: The symmetric para-terephthalate structure and higher molecular weight lead to stronger van der Waals forces between DOTP molecules themselves and with PVC chains, making it harder for them to leach out or evaporate.
- Better Low-Temperature Performance: The branched alkyl chains effectively prevent the PVC chains from packing together closely, maintaining chain mobility even at low temperatures and preventing the material from becoming brittle.
- Superior Electrical Insulation: The symmetrical structure and larger molecular size result in lower dipole polarization, leading to a lower dielectric constant and dissipation factor compared to ortho-phthalates.
Frequently Asked Questions (FAQ)–DOTP plasticizer guide
Based on the chemical structure, esters can be classified according to different criteria:
1. By the Number of Ester Functional Groups:
Monesters
Diesters
Polyesters
2. According to the Nature of the Parent Carboxylic Acid:
Aliphatic Esters
Aromatic Esters
3. Based on the Molecular Structure:
Cyclic Esters (Lactones)
Accordingly, Dioctyl terephthalate (DOTP) is unequivocally classified as an aliphatic-aromatic diester.
In general, an ester name puts the group derived from the alcohol first (usually as an alkyl or substituted-alkyl name) and the part derived from the carboxylic acid second, with the acid suffix “-ic acid” replaced by “-ate.” For example, ethanol + acetic acid → ethyl acetate. We normally omit the word “alcohol” in the ester name.
For compounds derived from polyols or polyacids, indicate the number and (if needed) the positions of esterification. Common names often use prefixes such as mono-, di-, tri- or terms like “bis(…)”/“tris(…)” when identical groups are present. For example, people commonly call the diester of terephthalic acid with octanol as dioctyl terephthalate (DOTP).
Neutralization neutralizes and removes residual acidic catalyst (or other acidic species) by converting them into water-soluble salts, thus stopping further acid-catalyzed reactions.
Water washing removes water-soluble impurities — such as inorganic salts, neutralization products, residual acids/bases, and small polar organic by-products — from the organic layer into the aqueous layer.
Dioctyl terephthalate is an excellent primary plasticizer for polyvinyl chloride (PVC) plastics. Specifically, when compared with the commonly used di-2-ethylhexyl phthalate (DEHP, or called DOP), it has the advantages of heat resistance, cold resistance, low volatility, anti-extraction, flexibility and good electrical insulation properties.
Conclusion
Whether you are sourcing DOTP, formulating PVC compounds, or comparing plasticizer performance, this DOTP plasticizer guide is your go-to resource. It consolidates technical data, manufacturing steps, and performance insights into one comprehensive reference for formulators and procurement teams.
Category: Dicarboxylate
Hot Tags: factory, Cold-resistant Plasticizer, Dioctyl Ester
Related Links:Dioctyl Adipate (DOA), Dioctyl Terephthalate (DOTP) CAS 6422-86-2 | Non-Phthalate Plasticizer Supplier, Plasticizer for cellulose resins, PVC Plasticizer
