Low hydrogen silicone oil is defined relative to high hydrogen silicone oil (hydrogen value is 1.6). It contains silicon hydrogen bond with low activity. It is the basic raw material for synthesis of modified silicone oil, such as polyether modified silicone oil and alkyl modified silicone oil. It is also a cross-linking agent for addition silicone rubber and can also be used for hydrophobic treatment of materials. At present, the hydrogen value of the most common low hydrogen silicone oil on the market is generally 0.1/0.18/0.22/0.36/0.5/0.8. Different low hydrogen silicone oils can be used according to different applications.
There are three main methods for the synthesis of low hydrogen silicone oil：
First, halogenated silane method: the starting materials are methylhydrodichlorosilane, dimethyldichlorosilane, trimethylmonochlorosilane and solvent, which are hydrolyzed and decomposed in a reactor, and then polymerized with concentrated sulfuric acid or solid acid catalyst. After the reaction, the solvent and low boiling matter are removed from the oil layer, and then decolorized and filtered to obtain the finished product; (Disadvantages: violent reaction, difficult to control, complex process, large amount of HCl gas will be released in the reaction process, which is not environmentally friendly)
The second is ring opening copolymerization: octamethylcyclotetrasiloxane (D4) and tetramethylcyclotetrasiloxane (DH4) are used for ring opening copolymerization, and the reaction is generally conducted in nitrogen atmosphere. The catalyst can be sulfuric acid, p-toluene, sulfonic acid or acid clay; (Disadvantages: the reaction process is violent and the raw materials are expensive, which is currently limited to laboratory research.)
The third is the polymerization method of high hydrogen silicone oil: the high hydrogen silicone oil capped by trimethyl silicon is used to conduct the polymerization reaction with octamethylcyclotetrasiloxane (D4) and hexamethyldisiloxane (MM) under the acid catalytic condition, and the catalyst can be sulfuric acid, trifluoromethylsulfonic acid or solid heteropoly acid.
For methyl low hydrogen silicone oil, please check the details:
https://www.siliconerubbers.net/product-methyl-low-hydrogen-silicone-oil-my203.html 
