Bis(2-ethylhexyl) terephthalate commonly abbreviated DEHT (Dioctyl terephthalate or DOTP), is an organic compound with the formula C6H4(CO2C8H17)2. It is a non-phthalate plasticizer, being the diester of terephthalic acid and the branched-chain 2-ethylhexanol, which is often generically referred to as octyl. This colorless viscous liquid is used for softening PVC plastics and is known for chemical similarity to general purpose phthalates such as DEHP and DINP, but without any negative regulatory pressure. It possesses very good plasticizing properties and may be used as a direct replacement for DEHP and DINP in many applications.
One method of manufacture entails the transesterification of dimethyl terephthalate with 2-ethylhexanol:
C6H4(CO)2(OCH3)2 + 2 C8H17OH → C6H4(CO2 C8H17)2 + 2CH3OH
A second method of manufacture is a direct esterification of terephthalic acid with 2-ethylhexanol:
C6H4(CO2H)2 + 2 C8H17OH → C6H4(CO2 C8H17)2 + 2H2O
DEHT is a general purpose plasticizer that is considered safer than ortho-phthalate plasticizers due to its reduced toxicity profile. The terephthalates exhibit none of the peroxisome proliferation of liver enzymes that some ortho-phthalates have shown in several studies.[1] It has uses in applications like extrusion, calendering, injection molding, rotational molding, dip molding, slush molding and coating.[2]
Several plasticizers offer similar technical properties to DEHT. These alternatives include phthalates such as DINP, DOP, DPHP, DIDP as well as non-phthalates such as DINCH and citrate esters.
According to a panel appointed by the French Agency for the Safety of Health Products (ANSM), there is very little clinical assessment data regarding the toxicity, migration from Medical Devices, and population exposure of alternative plasticizers (e.g. DEHT/DOTP) and their metabolites.[3] The French government report concludes: "The presently available information indicates that DEHTP is not expected to pose any health or environmental risks. DEHTP is not considered as toxic for reproduction and no alert was found on potential endocrine disruption properties of the substance."[4]
Researchers from Korea state that: "DEHT, a phthalate ester stoichiometrically eqivaluent to DEHP, has been shown to have potential reproductive and developmental toxicity."[5] The NOAELs quoted are actually quite high, indicating the potential for reproductive toxicity is low. The same paper further states: "The ability of DEHT to induce anti-androgenic effects in male offspring was assessed by giving pregnant rats 750 mg/kg/d DEHT; no changes were observed." And further: "Results of a uterotrophic assay in which immature females were given up to 2,000 mg/kg/d DEHT indicate that this compound does not possess estrogenic activity."