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Source: Industrial Materials Insights | October 2026
In modern industrial manufacturing and scientific research, achieving and maintaining a stable high-vacuum environment is fundamental to many critical processes. From vacuum coating to semiconductor fabrication, from optical lens production to metallurgical purification, the diffusion pump serves as a core component of high-vacuum systems — and the performance of its working fluid directly determines the attainable vacuum level and overall system efficiency.
IOTA 704 Silicone Diffusion Pump Oil, produced by Anhui Iota Silicone Oil Co., Ltd., is a purpose-engineered organosilicon working fluid designed for high-vacuum applications. With its low saturated vapor pressure, favorable thermal stability, and oxidation resistance, it has found broad adoption across electronics, optics, metallurgy, and other fields.
IOTA 704 is chemically identified as 1,1,5,5-Tetraphenyl-1,3,3,5-tetramethyltrisiloxane (CAS No. 3982-82-9), with a molecular weight of 484. It is a colorless, transparent, single-component fluid of high purity. Its homogeneous chemical composition contributes to stable vapor characteristics under sustained high-temperature operation.
| Parameter | Value |
|---|---|
| Appearance | Colorless transparent liquid |
| Kinematic Viscosity (25°C) | 38 ± 3 cSt |
| Refractive Index (25°C) | 1.5500 – 1.5600 |
| Specific Gravity (25°C) | 1.06 – 1.07 |
| Flash Point | ≥ 210°C |
| Congealing Point | -35°C |
| Saturated Vapor Pressure (25°C) | Approx. 2 × 10⁻⁸ torr |
| Ultimate Vacuum (untrapped) | 10⁻⁷ – 10⁻⁸ torr |
| Molecular Weight | 484 |
The above data are sourced from the manufacturer’s Technical Data Sheet (TDS). Users are advised to evaluate suitability based on their specific equipment operating conditions.
Low Saturated Vapor Pressure: At approximately 2 × 10⁻⁸ torr at room temperature, IOTA 704 minimizes back-diffusion of oil vapor into the vacuum chamber, supporting the maintenance of high vacuum levels.
Favorable Thermal Stability: With a flash point exceeding 210°C, IOTA 704 resists thermal decomposition during sustained high-temperature diffusion pump operation. The pump jet area remains relatively free of tar and hard carbon deposits, which can help extend maintenance intervals.
Oxidation Resistance: Even when briefly exposed to trace amounts of air at operating temperatures, IOTA 704 maintains chemical stability, effectively slowing fluid aging and reducing sludge formation.
Low-Temperature Fluidity: With a congealing point as low as -35°C, the fluid retains good liquid flow characteristics during cold storage and transportation.
Rapid Pump-Down Capability: The fluid delivers fast pump-down speeds even after exposure to air at operating temperatures, helping to reduce system recovery time.
IOTA 704 Silicone Diffusion Pump Oil is suited to a range of industrial scenarios requiring high-vacuum environments:
IOTA 704 is available in multiple packaging options: 1 kg plastic bottles, 5 kg / 25 kg / 50 kg plastic drums, and 200 kg steel drums — accommodating needs from small-scale research to large-scale production. The product is transported and stored as a non-hazardous material. Recommended storage conditions are cool, dry, and away from direct sunlight, with temperatures between -40°C and 50°C. Shelf life is 3 years under proper storage conditions.
Anhui Iota Silicone Oil Co., Ltd., based in Bengbu, Anhui Province, China, is a manufacturing enterprise specializing in the R&D, production, and sales of organosilicon materials. The company holds ISO 9001 quality management system certification and collaborates with multiple universities in Nanjing on industry-academia-research partnerships. Its product portfolio covers silicone oils, silicone rubber, fumed silica, silanes, platinum catalysts, and silicone resins.
Q1: What is the difference between IOTA 704 and IOTA 705? How should I choose?
A: The primary distinction lies in the vacuum level and application requirements. IOTA 704 is a high-vacuum grade product with a saturated vapor pressure of approximately 2 × 10⁻⁸ torr and an ultimate vacuum of 10⁻⁷–10⁻⁸ torr (untrapped), suitable for standard high-vacuum coating, lamp manufacturing, and similar applications. IOTA 705 is an ultra-high-vacuum grade product with a lower vapor pressure (approximately 3 × 10⁻¹⁰ torr) and an ultimate vacuum of 10⁻⁹–10⁻¹⁰ torr (untrapped), better suited for electron microscopes, mass spectrometers, particle accelerators, and other research equipment demanding higher vacuum levels. Selection should be based on the required operating vacuum level and process conditions of your equipment.
Q2: What is the recommended oil change interval for IOTA 704?
A: The oil change interval depends on specific operating conditions. For standard vacuum coating applications (operating temperature 150°C–200°C), a change interval of 12–18 months is recommended. For semiconductor equipment applications (180°C–220°C), 18–24 months is suggested. For high-temperature scenarios such as vacuum furnaces (200°C–250°C), the interval should be shortened to 6–12 months. In practice, adjustments should be made based on visual inspection of the fluid condition and the vacuum performance of the equipment.
Q3: What precautions should be taken when replacing diffusion pump oil?
A: The following guidelines are recommended when changing diffusion pump oil: (1) Allow the pump oil to cool below 60–70°C before shutting down the backing pump system; (2) After draining the old oil, inspect the pump body interior for visible deposits or carbonization, and clean if necessary; (3) Ensure containers and tools are clean when adding new oil, and avoid mixing different brands or grades; (4) After refilling, start the backing pump to establish vacuum and verify system integrity before activating the heater. Refer to the equipment manufacturer’s manual for detailed operating procedures.
Q4: Can IOTA 704 be mixed with diffusion pump oils from other brands?
A: It is generally not recommended to mix diffusion pump oils of different brands or grades. Although products designated as “704” share the same chemical structure (tetramethyl tetraphenyl trisiloxane, CAS 3982-82-9), differences in purity control and trace impurity levels among manufacturers may affect vapor pressure characteristics and thermal stability. When switching from another brand to IOTA 704, it is advisable to drain the old oil completely, clean the pump body, and then refill with fresh IOTA 704.
Q5: Are there any special requirements for transporting and storing IOTA 704?
A: IOTA 704 is classified as non-hazardous for transportation and storage, requiring no special hazardous materials handling credentials. Storage considerations include: (1) Store in a cool, dry, well-ventilated area; (2) Avoid direct sunlight and high-temperature heat sources; (3) Keep containers sealed to prevent moisture and contaminants from entering; (4) Maintain storage temperature between 0°C and 40°C and avoid prolonged freezing; (5) Keep away from strong acids, strong alkalis, and other aggressive chemicals. Under proper storage conditions, the product has a shelf life of 3 years.
Q6: How can I obtain samples and technical support for IOTA 704?
A: Users can contact the sales team through the Anhui Iota Silicone Oil Co., Ltd. official website (iotachem.com) to request product samples and Technical Data Sheets (TDS). The company can provide product selection guidance and on-site technical support based on the user’s equipment model and process requirements. Small-scale research users may start with 1 kg packaging for initial evaluation before proceeding to volume procurement once performance has been confirmed.
Disclaimer: The technical parameters cited in this article are sourced from the manufacturer’s publicly available Technical Data Sheet and are provided for reference purposes only. Actual product performance may vary depending on batch, operating conditions, and other factors. Users should conduct independent evaluation and verification based on their own equipment conditions. This article does not constitute any quality guarantee or performance warranty.
Silicone Diffusion Pump Oil IOTA 704 （Replacement for DC704）-IOTA
