Dioctyl Sebacate (DOS): Technical Specifications and High-Performance Industrial Applications

1. Technical Overview

Dioctyl Sebacate (DOS), also known as Bis(2-ethylhexyl) sebacate ($C_{26}H_{50}O_4$), is a high-performance, bio-based ester produced by the esterification of Sebacic acid with 2-ethylhexanol. It is a clear, colorless liquid recognized for its exceptional low-temperature properties and high thermal stability. In industrial R&D, DOS is a critical additive for formulations that must withstand extreme environments. As a plasticizer, it provides the highest level of cold-flexibility for PVC and synthetic rubbers. As a synthetic lubricant base oil, it offers an outstanding viscosity index and low volatility, making it the industry standard for aerospace, military, and high-end automotive lubricants.

2. Chemical Structure & Composition

The molecular structure of DOS features a long, linear 10-carbon sebacate backbone with two branched 2-ethylhexyl groups.

• Molecular Weight: 426.67 g/mol.

• High Purity: Typically >99% diester content.

• Structural Benefit: The linear sebacate chain provides flexibility, while the branched octyl groups lower the pour point and reduce volatility.

This specific molecular arrangement allows DOS to remain liquid at temperatures as low as -50°C, a property that few other plasticizers or mineral oils can match.

3. Physical & Chemical Properties

• Appearance: Colorless to pale yellow transparent liquid.

• Viscosity: 18.0 – 24.0 cSt at 20°C.

• Flash Point: ~215°C (Open Cup), ensuring safety in high-temperature environments.

• Pour Point: Below -50°C.

• Refractive Index: 1.448 – 1.452 at 20°C.

• Solubility: Insoluble in water; soluble in hydrocarbons, alcohols, and chlorinated solvents.

4. Reaction Chemistry

DOS is chemically inert under standard operating conditions but offers specific processing advantages:

1. Solvating Efficiency: At processing temperatures, DOS acts as a powerful solvent for PVC, leading to rapid gelation and a more uniform polymer matrix.

2. Oxidative Stability: The saturated nature of the sebacate chain provides inherent resistance to oxidation compared to unsaturated vegetable oils.

3. Hydrolytic Stability: While an ester, its long hydrocarbon chains provide a steric shield that improves resistance to hydrolysis compared to shorter-chain esters.

5. When to Use vs. When NOT to Use

Use Dioctyl Sebacate when:

• Manufacturing wire and cable insulation for arctic or aerospace conditions.

• Formulating synthetic greases and jet engine lubricants requiring a low pour point.

• Producing high-durability automotive interior parts that must resist “fogging” and embrittlement.

Do NOT use Dioctyl Sebacate when:

• The application is strictly cost-driven and low-temperature performance is not required (use general-purpose phthalates or adipates).

• The application involves contact with highly aggressive alkaline cleaners that could promote ester hydrolysis.

6. Compatibility Profile

DOS is highly compatible with:

• Polymers: Polyvinyl Chloride (PVC), Polyvinyl Butyral (PVB), and Nitrocellulose.

• Synthetic Rubbers: Nitrile (NBR), Neoprene (CR), and EPDM.

• Base Oils: Miscible with Mineral Oils, Polyalphaolefins (PAO), and other synthetic esters.

7. Manufacturing Process (Product Focus)

Nova Industries utilizes a precision esterification process:

1. Reaction: High-purity Sebacic acid is reacted with 2-ethylhexanol under a vacuum in the presence of an organometallic catalyst.

2. Neutralization & Washing: Residual acidity is removed through a multi-stage neutralization and deionized water wash.

3. Vacuum Stripping: Excess alcohol is stripped away to ensure a high flash point and low odor.

4. Final Purification: The oil is passed through activated carbon and multi-stage fine filtration to achieve ultra-low color and ash levels.

8. Technical Specifications Table

Parameter	Specification (High Purity)
Appearance	Colorless Transparent Liquid
Purity (by GC)	99.0% Min
Color (APHA)	30 Max
Acid Value (mg KOH/g)	0.05 Max
Moisture Content	0.10% Max
Specific Gravity (at 20°C)	0.912 – 0.918
Flash Point (COC)	210°C Min

9. Quality Grade Analysis

Nova Industries monitors Acid Value and Flash Point as primary markers of quality. An ultra-low acid value is mandatory for lubricant applications to prevent metal corrosion. A consistently high flash point confirms the complete removal of light-end alcohols, ensuring the material does not evaporate during high-temperature service.

10. Impact of Impurities

• Residual Alcohol: Lowers the flash point and increases the “fogging” effect in automotive interiors.

• Trace Metals: Can act as pro-oxidants, reducing the shelf life and performance of synthetic greases.

11. Industry-Wise Application 1: Aerospace & Military Lubricants

DOS is a primary base oil for MIL-spec lubricants. Its ability to maintain a lubricating film at extreme altitudes and sub-zero temperatures makes it indispensable for flight control systems and cold-weather military equipment.

12. Industry-Wise Application 2: Wire & Cable Insulation

In the cable industry, DOS is used for high-end insulation that must remain flexible in arctic conditions or in specialized industrial freezers. It ensures that cables do not crack when flexed at low temperatures.

13. Industry-Wise Application 3: Automotive Industry

Used in dashboard materials and upholstery to prevent “windshield fogging.” Its low volatility ensures that the plasticizer stays within the plastic, maintaining the soft-touch feel for the life of the vehicle.

14. Industry-Wise Application 4: Synthetic Rubbers

In the production of gaskets and seals for the oil and gas industry, DOS provides excellent swelling resistance and maintains seal integrity in high-pressure, low-temperature environments.

15. Formulation Guide

• Dosing: In PVC, typical loading ranges from 15 to 50 phr depending on the target “brittle point.”

• Blending: For lubricants, DOS can be blended with PAO to improve additive solubility and seal swell characteristics.

16. Sustainability Data

Dioctyl Sebacate is a bio-based product. By utilizing Sebacic acid derived from castor oil, it helps manufacturers reduce their dependence on petroleum-derived plasticizers like DOA (Dioctyl Adipate) while offering superior performance.

17. Packaging & Logistics (Technical)

• Standard: 190kg HDPE or Epoxy-lined MS Drums.

• Bulk: 1000kg IBC Tanks or ISO Tanks.

• Logistics: Non-hazardous for transport. Ensure containers are tightly sealed to prevent moisture absorption.

18. Storage Science

DOS should be stored in a cool, dry area. It is chemically stable but, like all esters, should be protected from long-term exposure to high humidity. Stainless steel tanks are recommended for bulk storage to maintain the ultra-low color specifications.

19. Troubleshooting Guide

• Problem: Plastic parts becoming brittle over time. Solution: Check the volatility of the DOS lot; residual alcohol may be causing the plasticizer to evaporate.

• Problem: Poor electrical resistance in cables. Solution: Verify the moisture and acid value; these must be at their absolute minimum for electrical grade applications.

20. Regulatory Compliance

Our DOS is REACH Compliant, TSCA listed, and meets the criteria for various international aerospace and automotive standards.

21. Safety (SDS Summary)

• Handling: Wear protective gloves and eyewear.

• Toxicity: Classified as non-toxic; however, standard industrial hygiene practices should be followed.

• Fire: High flash point; use CO2, dry chemical, or foam. Do not use direct water streams on burning oil.

22. Sample Validation Process

Verify the Flash Point and Acid Value. For lubricant manufacturers, a “Four-Ball Wear Test” in a finished formulation is recommended to confirm the lubricity performance.

23. Commercial Efficiency

Direct sourcing from Nova Industries ensures a consistent, high-purity product that meets both plasticizer and lubricant specifications. The high degree of refinement reduces the risk of additive fallout in complex lubricant formulations.

24. Technical FAQs

1. What is the difference between DOS and DOA? DOS has a longer carbon chain, providing lower volatility and better high-temperature stability than DOA (Dioctyl Adipate).

2. Is DOS biodegradable? Yes, it is derived from vegetable-sourced Sebacic acid and exhibits good biodegradability.

3. Can it be used in food-contact plastics? Yes, depending on local regulations, it is often used in specialized food-packaging films.

25. Contact CTA

For Technical Data Sheets (TDS), customized specifications, or to request a sample of our High-Purity DOS, please contact our technical export team: export@novaind.in

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