What are D4, D5 and D6?
D4, referred to as octamethylcyclotetrasiloxane, is a colorless transparent or milky white liquid, flammable, and has no peculiar smell. obtained compound. It is an important intermediate in the silicone industry, mainly used in the preparation of silicone polymers such as methyl silicone oil and other materials. D4 is also one of the important raw materials for textile silicone softeners. D5 is decamethylcyclopentasiloxane. D6 is dodecamethylcyclohexasiloxane, its appearance is colorless transparent oily liquid, volatile, low viscosity silicone oil.

The latest requirements of D4, D5 and D6 in REACH regulations
REACH is the abbreviation of "Registration, Evaluation, Authorization and Restriction of Chemicals", which is a European Union regulation on registration, evaluation, authorization and restriction of chemicals. REACH regulations apply to all chemical substances, including not only substances used in factories, but also chemicals in our daily life, including chemicals in clothes, furniture and electronic products.
On June 27, 2018, the European Chemicals Agency (ECHA) officially issued a notice that the SVHC candidate list added the 19th batch of 10 substances, including octamethylcyclotetrasiloxane (D4), decamethylcyclotetrasiloxane Pentasiloxane (D5), Dodecamethylcyclohexasiloxane (D6).
SVHC is Substance of Very High Concern (substance of very high concern), which generally has one or more of the following hazardous characteristics (Article 57 of the REACH Regulation):
According to the CLP regulations, substances with class 1 or class 2 carcinogenicity, mutagenicity or reproductive toxicity, that is, CMR 1A/1B substances;
Persistent, bioaccumulative or toxic substances, i.e. PBT substances;
Highly persistent, highly bioaccumulative substances, i.e. vPvB substances;
There is evidence of equally harmful substances, such as endocrine disruptors.

REACH regulations require silicone suppliers: the content of SVHC (substances of very high concern) in silicone chemicals is higher than 1000ppm (0.1%), and the export volume to the EU is greater than 1 ton/year, you need to notify the European Chemicals Agency; In addition, it is necessary to submit D4, D5 and D6 information in the supply chain, such as updating the relevant information of D4, D5 and D6 in the Material Safety Data Sheet (MSDS).

More details please click here.