Polysulfides, bis[3-(triethoxysilyl)propyl]

Endpoint summary

Description of key information

Abiotic degradation

The substance is a multi-constituent substance containing S2-S4 as the main constituents with S5 identified as a named impurity. The constituents of the substance, bis[3-(triethoxysilyl)propyl]polysulfides, hydrolyse with a hydrolysis half-life of greater than 40 hours. The hydrolysis products, bis[3-(trihydroxysilyl)propyl]polysulfides, are:

 

• (3-{[3-(trihydroxysilyl)propyl]disulfanyl}propyl)silanetriol
• (3-{[3-(trihydroxysilyl)propyl]trisulfanyl}propyl)silanetriol
• [3-({[3-(trihydroxysilyl)propyl]disulfanyl}disulfanyl)propyl]silanetriol
• (3-{[3-(trihydroxysilyl)propyl]pentasulfanyl}propyl)silanetriol

 

The other hydrolysis product is ethanol. Given the slow rate of hydrolysis, the environmental hazard assessment is based on the properties of the parent substance in accordance with REACH guidance for Chemical Safety Assessment (Chapter R16).

 

The silanol hydrolysis products listed above are the expected final products of hydrolysis reactions under conditions of a hydrolysis laboratory study. However, other biotic or abiotic reactions may occur over longer time-scales in the environment.

 

Biotic degradation

A guideline GLP biodegradation study for the substance indicates limited biodegradability; 5-15% in 28 days. This biodegradation is likely to be mostly due to the ethanol hydrolysis product, which is expected to biodegrade rapidly. The risk characterisation ratios (RCRs) for the aquatic, sediment and terrestrial compartments, based on the assumption that the parent constituents and their corresponding silanol hydrolysis products are not biodegradable, are < 1, and so it is not necessary to obtain further information on biodegradation via simulation tests in water, sediment or soil.

 

Table 4.1‑5: Degradation rates

Degradation rate in water:	Hydrolysis (t1/2 > 40 h) to ethanol, which is expected to biodegrade fast, and the silanol hydrolysis products, which are not expected to biodegrade.
Degradation rate in sediment:	The silanol hydrolysis products are not expected to biodegrade in sediment.
Degradation rate in soil:	The silanol hydrolysis products are not expected to biodegrade in soil.
Degradation rate in air:	The constituents and named impurity, and their silanol hydrolysis products may undergo indirect phototransformation; calculated half-lives for reaction with hydroxyl radicals in air are 0.1 days (S2 and its silanol hydrolysis product), 0.03 days (S3 and S4 and their corresponding silanol hydrolysis products) and 0.02 days (S5 and its silanol hydrolysis product).