Registration Dossier

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

Additional information

The test substance (CAS No. 100-20-9) is a solid. The melting point is 83°C, measured using a capillary apparatus. The boiling point is 269°C and was measured according to ASTM Method D1120. Bulk density is 0.872 g/mL at 22°C and was measured according to ASTM method No. E-727. Granulometry measurements have been conducted. Approximately 8.2% of the particles were less than 180 µm by sieving. Particle-size distribution measurements of the particles that passed through the sieve demonstrated that all of the sieved particles were less 5 µm. The vapour pressure is 0.149 Pa at 20ºC and was measured according to OECD Guideline 107 by the spinning rotor method. The octanol-water partition coefficient experiment was waived since it was technically not feasible. Since the test substance is hydrolytically unstable at pH 4, 7 and 9 (t ½ < 12 hr), the partition coefficient (-2.13 at pH 7) will be based on the primary degradate, terephthalic acid. The water solubility measurement was waived. Since the test substance is hydrolytically unstable at pH 4, 7 and 9 (t ½ < 12 hr), the water solubility will be based on the primary degradate, terephthalic acid. Under environmental conditions, the TPA will exist primarily in anionic form and the water solubility (15 mg/L at 20°C) will be higher than reported. The surface tension measurement was waived, since surface activity is not a desired property of the molecule. No flash point measurement was conducted, as the substance is a solid. No auto-ignition study was conducted, since the substance is a solid with a melting points less than 160°C. The test substance is not highly flammable as it did not ignite during the full 2 minutes of heating when tested according to EC Method A.10. Based on structural assessment, the test substance is non-explosive and non-oxidising. Measurement of stability in organic solvents was waived, since the stability in organic solvents is not considered critical. This would be assessed in individual studies where organic solvents are used. The dissociation constant measurement was waived, as the test substance is hydrolytically unstable at pH 4, 7 and 9 (t ½ < 12 hr), and the dissociation constant will be based on the primary degradate, terephthalic acid. Measurement of viscosity is technically not feasible, as the test substance is a solid.

 

Due to the instability of the test substance in water, selected physical and chemical properties of the main degradation product (CAS No. 100-21-0, terephthalic acid) are provided. The vapour pressure of the degradation product is reported as 1.2E-03 Pa (9.2E-06 mmHg) at 25°C. At environmentally relevant pH, the degradation product will exist predominantly in its anionic form. The logD, apparent partition coefficient D for dissociative systems is a more appropriate description of the complex partitioning equilibria. The logD value, as computed by ACD Labs v11.0, provided an estimate of -2.13 at pH 7. The water solubility of the degradation product at 20°C is reported as 15 mg/L in the AQUASOL dATAbASE of Aqueous Solubility. This solubility reflects the water solubility of the neutral form of terephthalic acid. Under environmental conditions, the hydrolysis product will exist primarily in anionic form and the water solubility will be higher than reported. The degradation product has 2 pKa values at 20°C, the pKa1 value is 3.5 and the pKa2 value is 4.34. Therefore, the degradation product will exist as the anionic species in the environment.