Hydroxyl silicone oil refers to linear polydimethylsiloxanes with reactive hydroxyl groups (-OH) at the molecular chain ends or side chains. As one of the most fundamental and widely used varieties in the silicone material system, its properties and value stem entirely from its unique molecular structure. Compared with conventional silicone oils, the presence of reactive hydroxyl groups transforms it from a mere inert lubricant into a reactive, cross-linkable, and compoundable functional intermediate, making it a core raw material for numerous high-end silicone products.
From a molecular structure perspective, hydroxyl silicone oil features a Si-O-Si main chain with methyl side groups. The main chain delivers exceptional flexibility, high and low temperature resistance, weather resistance, and hydrophobicity. The hydroxyl groups at the chain ends or side chains possess favorable chemical reactivity, enabling condensation, grafting, and cross-linking reactions with various substances such as hydrogen-containing silicone oil, alkoxysilanes, epoxy resins, and polyurethanes to form elastomers, coatings, and composite modified materials. This is the key distinction from dimethyl silicone oil. Based on the position and content of hydroxyl groups, it can be classified into terminal hydroxyl silicone oil and side-chain hydroxyl silicone oil, among which terminal hydroxyl silicone oil dominates the market due to its controllable reactivity and mature synthesis process.
The core properties of hydroxyl silicone oil combine "inert advantages" and "reactivity". It retains the low surface tension, excellent electrical insulation, and physiological inertness of polysiloxane, while possessing the potential for room-temperature cross-linking and curing. It can form dense waterproof films and elastic layers without high temperature or pressure. It has a wide temperature resistance range, with a long-term service temperature span of -50°C to 200°C, and exhibits outstanding resistance to UV radiation, ozone, and aging, with slow performance degradation in outdoor environments. It is non-toxic and non-irritating, complying with safety standards for food contact, daily chemicals, textiles, and other fields. Currently, the mainstream preparation process of hydroxyl silicone oil is hydrolysis polycondensation. Using dimethyldichlorosilane or dimethyldimethoxysilane as raw materials, hydrolysis is carried out in water or alcohol media, followed by catalytic polycondensation, neutralization, removal of low-boiling components, and filtration and refining to obtain the final product. This process is mature and stable, allowing precise control of molecular weight, hydroxyl content, and viscosity by adjusting the hydrolysis degree, catalyst type, and reaction temperature to meet the requirements of different application scenarios. With the increasing environmental requirements, solvent-free, low-volatility, and continuous production processes are gradually popularized, effectively reducing by-product emissions and energy consumption, making the production of hydroxyl silicone oil more in line with green chemical standards.
As a "cornerstone material" in the silicone industry, the performance optimization and process advancement of hydroxyl silicone oil directly drive the upgrading of downstream products. From basic waterproofing agents and defoamers to high-end silicone rubbers and coating modifiers, hydroxyl silicone oil, with its stable structure and flexible reactivity, supports a huge silicone application system, making it an indispensable key variety in modern fine chemicals.