Registration Dossier

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

Additional information

Appearance

Dimethyl terephthalate is an organic substance. It is a solid under standard conditions, either in the form of crystalline flakes or as a white, crystalline powder. The powder form comprises particles ranging from needle-like crystals to dust. (Sheehan, 2005; Eastman, 2009).

Melting point

The melting/freezing point of dimethyl terephthalate under standard atmospheric conditions is 141 degrees C (Park & Sheehan, 1996; Eastman, 2009).

Boiling point

The melting/freezing point of dimethyl terephthalate under standard atmospheric conditions ranges from 284 to 288 degrees C (Park & Sheehan, 1996; Eastman 2009).

Density

The crystal density of terephthalic acid is 1.58 g/cubic cm at 25 degrees C. The specific gravity of terephthalic acid is 1.522 at 25 degrees C (Park & Sheehan, 1996; Eastman, 2009).

Granulometry

A determination of particle size distribution (granulometry) need not be conducted on substances that are marketed or used in non-solid or non-granular form. Dimethyl terephthalate is not marketed or used in powder or granular form: it is commonly produced, transported and used in the molten state. If allowed to cool and solidify, the melt forms a rigid, solid cake. Milling or grinding would be necessary to transform the cake to a granule or powder, but neither process is applied in the commercial production of DMT.

Vapour pressure

The MPBPVP v1.43 QSAR model provides a vapour pressure estimate of 0.0331 Pa at 25 degrees C for dimethyl terephthalate (Modified Grain method). Additionally, MPBPVP provides a measured vapour pressure value of 1.33 Pa at 25 degrees C for dimethyl terephthalate, retrieved from the database used to construct the QSAR model. The vapour pressure of DMT (based on extrapolation from reduced pressure boiling point measurements) is estimated to be 0.000139 kPa at 20 degrees C (Eastman, 2009).

Partition coefficient

The log octanol/water partition coefficient (log Kow) of dimethyl terephthalate has been determined according to the shake-flask procedure described in OECD Guideline 107. The log Kow of DMT (mean of six determinations) is 2.21 (Hirshen et al., 2009).

The log Pow of dimethyl terephthalate was estimated using the KOWWIN v1.67 QSAR model available from the US EPA. The estimated log Kow of dimethyl terephthalate is 1.66. Additionally, KOWWIN provides a measured log Kow value of 2.25 for dimethyl terephthalate, retrieved from the data base of experimental results used to construct the QSAR model, and this value corresponds closely to the result of the shake-flask determination performed according to OECD Guideline 107.

Wherever other models of the US EPA's EPISUITE QSAR programs have been used to generate estimates of physico-chemical or environmental fate and behaviour characteristics that require input of log Kow, these secondary models selected the database (measured) log Kow of 2.25 as the default value for dimethyl terephthalate.

Water solubility

The aqueous solubility of dimethyl terephthalate was determined according to the flask method of OECD guideline 105. Based on the mean measured concentration of DMT in filtered samples, the aqueous solubility of dimethyl terephthalate is 31 mg/L at 20 degrees C. (Hirschen et al., 2009).

Solubility in organic solvents

Limits of the solubility of dimethyl terephthalate at 25 degrees C are published for ten organic solvents: ethylene glycol (0.8 %, w/w), methanol (1.0 % w/w), carbon tetrachloride (1.5 % w/w), ethyl ether (1.6 %, w/w), methyl ethyl ketone (1.6% w/w), benzene (2.0% w/w), ethyl acetate (3.5% w/w), toluene (4.3% w/w), dioxane (7.5% w/w) and chloroform (10 % w/w) (Park & Sheehan, 1996).

Surface tension

In accordance with Column 2 adaptation statement of REACH Annex VII, information requirement section 7.6, this study does not need to be conducted if based on structure, surface activity is not expected and no surface-active properties would be predicted for this compound. Surface activity is not a desired property of the material.

Flash point

The flash point of dimethyl terephthalate corrected to 101.325 kPa is 151 degrees C.

Autoflammability

In accordance with Column 2 adaptation statement of REACH Annex VII, information requirement section 7.12, this study does not need to be conducted for solids with melting points < 160°C.

Flammability

A flammability screening test was performed by igniting a loosely-packed linear pile of DMT powder. Combustion self-extinguished without propagating along the pile. According to the UN Recommendations on the Transport of Dangerous Goods, dimethyl terephthalate is therefore classified as a non-readily combustible solid of Division 4.1 and further flammability testing is not required. (Lim, 2010).

Explosiveness

According to theoretical considerations based on chemical structure, dimethyl terephthalate does not to possess explosive or oxidising properties. Dimethyl terephthalate is unlikely to undergo rapid decomposition accompanied by the evolution of gases or release of heat and therefore does not present a risk of explosion (Curl & Wright, 2010a).

Oxidising properties

In accordance with Column 2 adaptation statement of REACH Annex VII, information requirement 7.13, this study does not need to be conducted based on structural assessment of the substance. The substance contains no oxidising groups and all oxygen atoms are bonded directly to carbon. 

Stability in organic solvents and identity of relevant degradation products

In accordance to REACH Annex XI Section 2, with reference to the guidance mentioned in REACH Art 13(3) the test guidance "ECHA guidance on Information requirements and chemical safety assessment Chapter R.7a Endpoint specific guidance" needs to be respected. This guidance indicates that this study does not need to be conducted since the stability in organic solvents is not considered critical. This would be assessed in individual studies where organic solvents are used.

Dissociation constant

SPARC predicts a log 10 dissociation constant of -5.29 for dimethyl terephthalate at 25 degrees C. DMT is not expected to undergo rapid or extensive dissociation.

Viscosity

A waiver has been proposed because terephthalic acid is a solid under standard conditions.