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Hydroxy silicone oil — also known as hydroxyl-terminated polydimethylsiloxane (PDMS) — is a reactive silicone fluid featuring hydroxyl (–OH) groups at both ends of its polymer chain. These terminal hydroxyl groups give the molecule exceptional reactivity and surface-bonding capability, making it one of the most versatile functional silicone intermediates in industrial chemistry.
In the context of mold release agents, hydroxy silicone oil functions as either a standalone release lubricant or a key reactive component in formulated release coatings. Its Si–O backbone provides inherently low surface energy, excellent thermal stability (stable from –50°C to +200°C), outstanding chemical inertness, and a non-toxic, non-flammable safety profile — all critical requirements for high-performance mold release systems.
The reactive –OH terminals allow hydroxy silicone oil to cross-link with metal mold surfaces, silane coupling agents, or other silicone polymers, forming a durable, thin-film release layer that resists repeated molding cycles without frequent reapplication. This cross-linking capability differentiates it from standard linear PDMS fluids and underpins its growing adoption across rubber, plastics, composites, and die-casting industries.
| Property | Typical Value / Range | Significance for Mold Release |
|---|---|---|
| Appearance | Colorless to light yellow transparent liquid | No staining of molded parts |
| Viscosity (25°C) | 50 – 20,000 mPa·s (grade-dependent) | Adjustable film thickness & coverage |
| Hydroxyl Content | 0.1% – 3.5% (by weight) | Controls cross-link density & adhesion |
| Thermal Stability | –50°C to +200°C (continuous use) | Suitable for high-temp molding processes |
| Surface Tension | ~20–21 mN/m | Excellent wetting & spreading on mold surfaces |
| Flash Point | >300°C | Safe for hot-mold environments |
| Refractive Index | 1.400–1.405 | Optically clear films for precision optics molding |
The –OH end groups enable covalent bonding to mold metal surfaces and cross-linking into semi-permanent release films, dramatically extending mold release intervals compared to conventional oils.
Stable performance from –50°C to over 200°C makes hydroxy silicone oil the preferred release agent for high-temperature rubber vulcanization, die-casting, and composite curing processes.
With a surface tension of approximately 20 mN/m, the silicone film prevents adhesion of virtually all polymer, rubber, and metal substrates, ensuring clean, damage-free part ejection.
The Si–O–Si backbone is inert to most acids, alkalis, and solvents encountered in industrial molding environments, providing long-lasting mold protection and reduced maintenance costs.
Available from low-viscosity (50 mPa·s) spray-grade fluids to high-viscosity (20,000 mPa·s) coating grades, enabling precise formulation for every mold geometry and production speed.
Meets RoHS, REACH, and major international safety standards. Non-flammable, non-corrosive, and low-VOC, supporting sustainable manufacturing and worker safety compliance.
In tire and technical rubber molding, hydroxy silicone oil forms a thermally stable, cross-linked release film that withstands vulcanization temperatures above 160°C, preventing rubber adhesion to mold cavities while maintaining precise tread detail and surface finish.
Carbon fiber reinforced polymer (CFRP) and epoxy composite parts require zero-contamination release agents that do not interfere with subsequent bonding or painting. Hydroxy silicone oil's thin, reactive film meets aerospace-grade cleanliness requirements for autoclave and RTM processes.
In aluminum and zinc die-casting, hydroxy silicone oil-based release agents provide thermal protection to mold surfaces, reduce thermal fatigue, and enable higher cycle rates by improving part ejection reliability even at mold temperatures exceeding 180°C.
PU foam and reaction injection molded (RIM) parts are notoriously difficult to release due to isocyanate adhesion. Hydroxy silicone oil, formulated with silane coupling agents, creates a barrier film that eliminates sticking while preserving the fine surface texture of the molded foam.
Ultra-low refractive-index variation and optical clarity of hydroxy silicone films make them ideal for glass lens molding and precision optics manufacturing, where surface contamination or micro-scratches are unacceptable.
Applied to steel and plastic formwork in precast concrete production, hydroxy silicone oil release agents reduce adhesion, improve surface quality of finished panels, and extend formwork service life by protecting against alkaline concrete chemistry.
The global mold release agent market was valued at approximately USD 3.5 billion in 2023 and is projected to grow at a CAGR of 4.8% through 2030, driven by expanding automotive production, aerospace composite manufacturing, and the booming electric vehicle (EV) battery enclosure and structural component molding sectors. Silicone-based release agents — with hydroxy silicone oil at the core — account for the fastest-growing segment due to their superior performance profile over traditional wax, fluoropolymer, and petroleum-based alternatives.
The shift to electric vehicles is accelerating demand for precision-molded composite battery housings, structural foam parts, and rubber sealing components — all requiring advanced silicone release systems. Hydroxy silicone oil formulations are increasingly specified in EV supply chains for their compatibility with epoxy, polyurethane, and thermoplastic composite processes.
The industry is moving away from single-use, solvent-based release sprays toward semi-permanent reactive coatings based on hydroxy silicone oil cross-linked systems. These coatings survive 50–200+ release cycles per application, dramatically reducing downtime, waste, and production costs in high-volume molding operations.
Tightening global environmental regulations (REACH, EPA VOC limits, China GB standards) are driving formulators to replace solvent-borne release agents with water-based emulsions featuring hydroxy silicone oil as the active ingredient. These emulsions deliver equivalent release performance with significantly reduced environmental impact and workplace hazard.
China, India, South Korea, and Southeast Asian nations are rapidly expanding their rubber goods, electronics encapsulation, and automotive parts manufacturing capacity. This regional growth is creating substantial demand for cost-competitive, high-quality hydroxy silicone oil supply chains, with Chinese producers like Bayee Chemical well-positioned to serve both domestic and global markets.
Manufacturers are demanding release agents tailored to specific substrates and processes — from ultra-low-viscosity spray grades for complex geometries to high-viscosity brush-applied grades for large precast molds. Hydroxy silicone oil's tunable viscosity and hydroxyl content make it uniquely adaptable to this trend toward application-specific product development.
As Industry 4.0 transforms production floors, automated release agent application systems (robotic spraying, precision dosing) are replacing manual application. Hydroxy silicone oil's consistent rheology and predictable film-forming behavior make it highly compatible with these automated dispensing systems, supporting zero-defect manufacturing initiatives.
Traditional wax and petroleum-based release agents degrade rapidly at elevated temperatures, require frequent reapplication, and often contaminate part surfaces — compromising downstream bonding, painting, and coating operations. Hydroxy silicone oil's reactive chemistry, thermal resilience, and ultra-low surface energy deliver a step-change improvement in mold release efficiency, part quality, and total production economics.
View OH-Hydroxy Terminated Silicone Fluid Request Technical DatasheetHangzhou Bayee Chemical Co., Ltd. started chemical products exporting from 2001, manufacturers based exporter focused in chemical products covering Silicone series, Phosphorus series including Silicone Monomers, Cyclosiloxane, Silicone Oils, Agro Chemicals, Fire Retardants & Auxiliaries etc. Company has direct Import & Export right, Dangerous Cargo Permission Certificate.
Based on 20+ years exporting history and persistent improvements, we have now grown and developed into a well known & good reputation exporter with ISO 9001:2015, AAA Credit certified company, also granted by local government as Healthy Enterprise, and A level Tax Ranking.
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Based on strategic factories in Zhejiang, Jiangsu, Shandong, Anhui, Jiangxi, Hubei, Hunan, Hebei and Henan provinces, we export not only good quality products and competitive EXW costs, but also honesty, safety and international philosophies to customers. We work tightly with competitive production sites across whole China, who have special advantages, located in professional industrial areas, close to raw material bases, locally supplied with energy — gas or steam pipe connected with neighbour enterprises in same areas to reduce transportation costs.
Our factories have advanced ideas in technique crafts for higher yield production, unit consumption reducing from raw materials, also re-used the by-products for own downstream production for other products. We always keep close observation about raw material changing trend, react actively with factories shoulder by shoulder from organizing raw material at good times to secure more competitive production costs and share spaces with customers helping win their market shares. At the same time, we have wide connection with Chinese powerful chemical institute organizations for testing and supervising quality control in production process.
Up till now we've developed and supplied to many countries and areas all over the world, with main markets in European countries (Germany, Italy, UK, Spain, Ukraine, Russia, Poland, etc.), USA, South America, Mid East, South-east Asia, Australia, etc. Also seeking more strategic partners and customers under mutual benefits and work through the whole purchasing chain.
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