Registration Dossier

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

Additional information

Bis(3,5,5-trimethylhexanoyl) peroxide is a colourless organic liquid. The substance has to be stored at -8 to 0 °C. The control temperature is 0 °C, the emergency temperature is 10 °C. The substance precipitates at -8 °C. The melting range of bis(3,5,5-trimethylhexanoyl) peroxide is outside the detectable range of -70 to 400 °C. It may be stated as −75.4 °C or lower. The boiling point could not be determined because the substance decomposes before boiling.

The density of bis(3,5,5-trimethylhexanoyl) peroxide is 890 g/L at 0 °C. The vapour pressure of bis(3,5,5-trimethylhexanoyl) peroxide at 25 °C was determined using available experimental data and calculations. The vapour pressure of bis(3,5,5-trimethylhexanoyl) peroxide at 25 °C is most likely in the range of 1.0E-02 to 1.0E-05 Pa. For the purpose risk assessment, a value of p = 0.001 Pa is used.

The QSAR estimation for the partitioning coefficient results in a log Pow of 7.0288 for bis(3,5,5-trimethylhexanoyl) peroxide (EPISuite, KOWWIN). However, the peroxide is hydrolytically unstable with a short half-life, probably less than one hour at 5 °C. At environmentally relevant temperatures, the substance will undergo hydrolytical degradation significantly faster. Therefore, the parent substance bis(3,5,5-trimethylhexanoyl) peroxide itself is not relevant since it will not be present in the environment.

Seven degradation products were detected in GC chromatograms but only the breakdown products 3,5,5-trimethylhexanoic acid (CAS no. 3302-10-1) and 2,4,4-trimethyl-1-pentanol (CAS no. 16325-63-6) could be identified with sufficient certainty.

Although the log Pow of bis(3,5,5-trimethylhexanoyl) peroxide can be estimated by QSAR at 7.03, the rapid hydrolysis of the peroxide requires using data on the hydrolysis products for the chemical safety assessment. The representative worst case figure is the log Pow for the breakdown product 3,5,5-trimethylhexanoic acid, which has been estimated by QSAR at 3.34. This figure is therefore adopted as the key value for the CSA.

The rapid hydrolytical degradation of di(3,5,5-trimethylhexanoyl) peroxide complicates determination of water solubility. This endpoint was determined in the course of a hydrolysis experiment. Due to lack of a specific analytical method for the test substance solubility was assessed using the fluorescein method, by visual observation in comparison to freshly prepared standard solutions of the test item (1 and 10 mg/L). Over the 24 h experimental period fluorescence increased from an intensity corresponding to a concentration of 1 mg/L after 1 h to 10 mg/L after 24 h. For assessment purposes, the water solubility can thus be assumed to range between 1 and 10 mg/L. A value of 10 mg/L is used in the risk assessment.

The flash point of bis(3,5,5-trimethylhexanoyl) peroxide was determined to be 61 °C.

The dynamic viscosity of bis(3,5,5-trimethylhexanoyl) peroxide is 12 mPa × s at 0 °C.

The substance has no explosive properties because it is not classified as “Organic Peroxide Type B” (reference CLP regulations and UN Recommendations on the Transport of Dangerous Goods, 16th revised edition, section; also see ECHA guidance on the application of the CLP criteria, section 2.14). The substance is an organic peroxide Type D.

The SADT of bis(3,5,5-trimethylhexanoyl) peroxide is +20 °C.

The stability in organic solvents is not considered critical and testing is therefore not required. This is due to the fact that for organic peroxides at the maximum market concentrations, there is extensive experience in handling and shipment, supporting the stability in the solvents used (or even needed for stabilising reasons). In some cases, approval by authorities is obtained (e.g. statements from German BAM) specifying suitable solvents. In addition, in the context of toxicity studies, analytical data support and confirm the stability of the substance in relevant solvents.