Unlocking endless possibilities: Hexamethyldisiloxane (HMDS) (HC-YM9230) ------ Your innovative partner in materials science and fine chemicals

Ⅰ. Product Introduction

Hexamethyldisiloxane ( C₆H₁₈OSi₂ , MM for short) is the simplest linear siloxane and an important organosilicon compound. It is a colorless, volatile liquid with an ether-like odor. It is mainly used as an end-capping agent, silicone oil end-capping agent, silicone resin end-capping agent, etc. It is composed of two trimethylsilyl groups ( -Si(CH₃)₃ ) connected by oxygen atoms. Its molecular formula is (CH₃)₃Si-O-Si(CH₃)₃ , and it has the following core characteristics:

Low viscosity: 0.65–0.75 cSt at 25°C, close to water (1 cSt), with excellent fluidity;

High volatility: boiling point 99–101°C, easily volatile at room temperature, with very low residual content;

Chemical inertness: acid and alkali resistant (pH 2–12), antioxidant, and compatible with most organic substances;

Hydrophobicity: contact angle >100°, surface tension as low as 18–20 mN/m.

Key physicochemical parameters:

Ⅱ. Synthesis process and industrial production

MM is mainly prepared by the hydrolysis and condensation reaction of methylchlorosilane. The typical process is as follows:

Raw materials: trimethylchlorosilane ((CH₃)₃SiCl) and dimethyldichlorosilane ((CH₃)₂SiCl₂);

Hydrolysis: Hydrolysis in acidic aqueous solution to generate silanol intermediates;

Condensation: Control pH (3–5) and temperature (50–70°C) to promote linear condensation:

2(CH₃)₃SiOH →(CH₃)₃Si-O-Si(CH₃)₃+H₂O

Purification: MM is separated from other siloxanes (such as D4 and D5) by distillation, and the purity can reach 99.9%.

Ⅲ. Core application areas and technical cases

1. Personal Care and Cosmetics

Volatile carrier: used in spray-type products (sunscreen, antiperspirant), evaporates quickly without leaving residue;

Case: A brand of refreshing sunscreen spray , adding MM to improve skin feel and enhance the stability of SPF value;

Hair Conditioner : Reduces the coefficient of friction of hair (from 0.8 to 0.3), enhancing shine and smoothness.

2. Electronics and Semiconductors

Cleaning solvent: used for wafer cleaning and removal of photoresist residue (compatible with copper and aluminum metals);

Technical advantages: low surface tension, can penetrate nanoscale pores (<10 nm);

Heat dissipation medium: fills the gap between the CPU and the radiator, reducing thermal resistance by 30% (Intel laboratory data).

3. Industrial lubrication and demoulding

Precision machinery lubrication : used for high-speed bearings, with a friction coefficient as low as 0.05 (ASTM D5183);

Rubber release agent: compounded with fluorosilicone, demoulding efficiency is increased by 60% (applied in Michelin tire production line).

4. Medicine and pesticides

Drug synthesis intermediate: as a silanization reagent to protect hydroxyl/amino active groups;

Pesticide synergist : Reduces the surface tension of the pesticide solution and increases the leaf adhesion rate by 40% (Syngenta formulation formula).

5. Polymer material modification

Silicone rubber processing aid: improve mixing fluidity and shorten processing time by 20%;

Plastic antistatic agent: When compounded with quaternary ammonium salt, the surface resistivity is reduced to 10⁹ Ω/sq (GB/T 1410 standard).

Ⅳ. Safety and Environmental Protection

1. Toxicological data

Acute toxicity: oral LD₅₀ in rats＞5,000 mg/kg (low toxicity);

Skin irritation: No erythema/edema in rabbit skin test (OECD 404 standard);

Ecotoxicity: Fish 96h LC₅₀ ＞100 mg/L (low aquatic toxicity).

2. Environmental fate

Degradability: 28-day biodegradation rate <5% (OECD 301B), need to pay attention to persistence;

Mobility: Henry constant 0.03 Pa·m³/mol , half-life in the atmosphere is about 12 days.

3. Regulatory Compliance

EU REACH: registered, no SVHC (Substances of Very High Concern) restrictions;

China GB: Unlimited quantity requirement in cosmetics (use as needed);

US OSHA: The Permissible Exposure Limit (PEL) is 100 ppm (8-hour weighted average).

Ⅴ. Future trends and innovation directions

1. Green synthesis technology

Bio-based raw materials: Using lignin-derived methanol to replace fossil raw materials, reducing the carbon footprint by 40%;

Electrochemical process: Catalyst-free electrolytic synthesis, reducing energy consumption by 30%.

2. Functional modification

Fluorination modification: the introduction of trifluoropropyl improves the chemical resistance to 98% concentrated sulfuric acid;

Nanocomposite: Composited with SiO₂ nanoparticles for super hydrophobic coating (contact angle > 160°).

3. Expansion of emerging applications

Solid-state battery electrolyte: As a lithium salt solvent, the ion conductivity is increased to 10⁻³ S/cm;

3D printing support material: High volatility enables fast demoulding with an accuracy of ±0.1mm.

Ⅵ. Conclusion

With its low viscosity, high volatility and chemical inertness, hexamethyldisiloxane (MM) plays an irreplaceable role in personal care, electronics, medicine and other fields. With the rapid development of semiconductor and new energy industries, the demand for high-end applications of MM will continue to grow. In the future, through green process innovation and functional design, this "invisible hero" may open up a new era in sustainable materials and intelligent technology and become a key driver of cross-industry innovation.

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