Dioctyl terephthalate
[CAS# 6422-86-2]

Identification

• Classification: Chemical reagent >> Organic reagent >> Ester >> Octyl ester
• Name: Dioctyl terephthalate
• Synonyms: Bis(2-ethylhexyl) terephthalate; 1,4-Benzenedicarboxylic acid bis(2-ethylhexyl) ester
• Molecular Formula: C₂₄H₃₈O₄
• Molecular Weight: 390.56
• CAS Registry Number: 6422-86-2
• EC Number: 229-176-9
• SMILES: CCCCC(CC)COC(=O)C1=CC=C(C=C1)C(=O)OCC(CC)CCCC

Properties

• Density: 0.986 g/mL (25 °C) (Expl.)
• Melting point: -48 °C (Expl.)
• Boiling point: 400 °C (Expl.)
• Flash point: 212 °C (Expl.)
• Refraction index: 1.49 (Expl.)
• Water solubility: insoluble

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H302-H315-H319-H335
• Safety Statements: P261-P280-P301+P312-P302+P352-P305+P351+P338

Discovery and Applications

Dioctyl terephthalate (DOTP) is an ester of terephthalic acid and 2-ethylhexanol, classified as a plasticizer. It is a clear, colorless, and non-volatile liquid with excellent flexibility-enhancing properties when added to polymers. Its molecular structure is based on terephthalic acid, a benzene ring substituted with two ester-linked octyl groups, which contributes to its stability and compatibility with various materials.

The discovery and commercial development of dioctyl terephthalate emerged as part of the broader search for effective and less toxic plasticizers to replace phthalates such as di(2-ethylhexyl) phthalate (DEHP). Due to increasing health and environmental concerns associated with some phthalate plasticizers, dioctyl terephthalate has gained importance as a safer alternative with comparable performance characteristics.

Dioctyl terephthalate is widely used in the production of flexible polyvinyl chloride (PVC) products, where it enhances the material’s flexibility, durability, and processability. It improves the softness and elongation of PVC, making it suitable for applications such as flooring, cables, wires, automotive interiors, and synthetic leather. The plasticizer’s high molecular weight and chemical stability contribute to the improved resistance of the polymer products to heat, light, and extraction by oils or solvents.

Apart from PVC, dioctyl terephthalate is compatible with other polymers, including polyvinyl acetate, acrylates, and some rubbers, which broadens its range of industrial uses. Its low volatility reduces plasticizer loss during processing and product use, contributing to longer-lasting flexibility and stability.

The compound’s resistance to hydrolysis and oxidation makes it well-suited for outdoor and demanding applications, including coatings, adhesives, and sealants, where durability and performance over time are essential. Furthermore, dioctyl terephthalate is known for its good electrical insulation properties, which is important in electrical cable and wire manufacturing.

Environmental and health evaluations have shown that dioctyl terephthalate exhibits low toxicity and minimal bioaccumulation potential compared to traditional phthalates. This profile has encouraged its adoption in products that require compliance with stricter regulatory standards, including toys, medical devices, and food-contact materials.

In manufacturing, dioctyl terephthalate is typically produced by esterification of terephthalic acid or dimethyl terephthalate with 2-ethylhexanol in the presence of acidic catalysts. The process yields a high-purity product that meets industrial specifications for performance and safety.

In summary, dioctyl terephthalate is a widely used plasticizer derived from terephthalic acid and 2-ethylhexanol. It was developed as a safer alternative to certain phthalate plasticizers and finds extensive application in flexible PVC and other polymers. Its chemical stability, low toxicity, and excellent plasticizing properties make it a preferred choice in many industrial sectors including construction, automotive, electronics, and consumer goods.

References

2022. Time-trends in human urinary concentrations of phthalates and substitutes DEHT and DINCH in Asian and North American countries (2009-2019). Journal of Exposure Science & Environmental Epidemiology, 33(2).
DOI: 10.1038/s41370-022-00441-w

2023. Contaminants of emerging concern in urine: a review of analytical methods for determining diisocyanates, benzotriazoles, benzothiazoles, 4-methylbenzylidene camphor, isothiazolinones, fragrances, and non-phthalate plasticizers. Environmental science and pollution research international, 30(40).
DOI: 10.1007/s11356-023-29070-y

2024. Synthesis and properties of an eco-friendly bio-based plasticizer for PVC with enhanced migration resistance. Journal of Materials Science, 59(36).
DOI: 10.1007/s10853-024-10092-x