DOTP - Dioctyl Terephthalate — Frequently Asked Questions

Both are di(2-ethylhexyl) esters of benzene dicarboxylic acids with the same formula, C24H38O4. In DOP (DEHP) the ester groups sit side by side on the ring, making it an ortho-phthalate; in DOTP they sit opposite each other, making it a terephthalate. That difference gives DOTP a different toxicological and regulatory profile, and slightly lower plasticising efficiency with lower volatility.

DOTP is not an ortho-phthalate, which is the group restricted in toys and childcare articles and subject to authorisation under EU and UK REACH. Its chemical name still contains "phthalate", so some brand owners treat it separately from "phthalate-free" claims. Check how your customer's specification defines the term before describing a compound made with DOTP.

DOTP is slightly less efficient than DEHP, so matching the hardness of a compound typically takes a few per cent more plasticiser, often around 3–5% more by weight. The exact figure depends on the formulation and target hardness. Run a small trial and measure Shore hardness, then fine-tune the level. Fusion temperature may also rise slightly, so check gelation on your process.

Cable compounds must keep their flexibility at high service temperatures and retain good electrical insulation. DOTP's low volatility means less plasticiser is lost on heat ageing, and its volume resistivity is higher than that of many general-purpose plasticisers. For higher temperature ratings, formulators may combine it with a trimellitate. Specify a cable grade with a resistivity limit where electrical performance matters.

Ester content, colour, acid value and water are the core parameters. Ester content confirms purity, colour matters in clear and light-coloured products, acid value indicates hydrolysis or residual catalyst that can affect heat stability, and water can cause haze or processing problems. Density and flash point confirm identity and safety, and cable grades add volume resistivity.