Blown Castor Oil: Technical Specifications and Industrial Applications of Oxidized Triglycerides

1. Technical Overview

Blown Castor Oil, also referred to as Oxidized Castor Oil, is a specialized derivative produced by the controlled polymerization of refined castor oil through the introduction of air at elevated temperatures.² Unlike the parent oil, Blown Castor Oil features significantly higher viscosity, increased density, and enhanced pigment-wetting properties.³ During the “blowing” process, the double bonds in the ricinoleic chain undergo oxidative polymerization and cross-linking, creating complex molecular structures with higher molecular weights.⁴ In industrial R&D, it is primarily utilized as a non-migratory plasticizer, a high-tack lubricant additive, and a binder in printing inks and coatings where film durability is essential.

2. Chemical Structure & Composition

The chemical identity of Blown Castor Oil is defined by the degree of oxidation.

• Polymerized Triglycerides: The process creates intermolecular oxygen bridges (ether and peroxide linkages) between the fatty acid chains.

• Functional Groups: It retains its primary hydroxyl functionality while gaining hydroperoxide and carbonyl groups through oxidation.

• Molecular Weight: Significantly higher than standard castor oil, leading to its characteristic viscous nature.⁶

The resulting structure is highly polar, which ensures excellent adhesion to polar substrates and superior compatibility with a wide range of synthetic resins.

3. Physical & Chemical Properties

Blown Castor Oil is a heavy, viscous, transparent liquid with the following technical hallmarks:

• Viscosity: Highly customizable, ranging from 15 stokes to 100+ stokes at 25°C, depending on the blowing time.

• Color: Typically darker than refined oil, ranging from amber to deep brown (Gardner 5–9).

• Specific Gravity: Higher than refined castor oil, usually between 0.980 and 1.000.

• Acid Value: Tends to increase during the blowing process, typically ranging from 5 to 15 mg KOH/g.

• Solubility: Soluble in aromatic hydrocarbons, esters, and ketones; limited solubility in mineral oils without coupling agents.

4. Reaction Chemistry

The reactive nature of Blown Castor Oil stems from its oxidized structure:

1. Cross-linking: The remaining double bonds and hydroxyl groups can react with cross-linkers like isocyanates or amino resins to form tough, flexible films.⁷

2. Esterification: The increased acidity allows for targeted reactions in specialized resin synthesis.

3. Surfactant Synthesis: Can be further modified to create high-viscosity emulsifiers for oil-in-water systems.

5. When to Use vs. When NOT to Use

Use Blown Castor Oil when:

• You require a non-migratory plasticizer for nitrocellulose, especially in artificial leather or high-gloss lacquers.

• Formulating heavy-duty lubricants or “tackifiers” for open-gear systems.

• Manufacturing printing inks that require high gloss and superior rub resistance.

Do NOT use Blown Castor Oil when:

• The application requires a water-white or very light color (use PPG or FSG instead).

• Low-viscosity penetration is required (use Methyl Ricinoleate instead).

• The formulation is highly sensitive to acid value (unless neutralized during the process).

6. Compatibility Profile

Blown Castor Oil exhibits exceptional compatibility with:

• Polymers: Nitrocellulose (NC), Ethyl Cellulose, PVB, and chlorinated rubber.

• Resins: Shellac, Rosins, and Alkyds.

• Plasticizers: Synergistic when used with phthalate-free plasticizers to prevent migration and sweating.

7. Manufacturing Process (Product Focus)

Nova Industries utilizes a precision-controlled blowing process:

1. Heating: Refined castor oil is heated in a specialized reactor to temperatures between 80°C and 130°C.

2. Aeration: Compressed air is bubbled through the oil at a controlled rate.⁸

3. Oxidation Monitoring: The viscosity and acid value are monitored in real-time.

4. Quenching: The reaction is stopped abruptly once the target viscosity (e.g., Z2, Z5 on the Gardner-Holdt scale) is achieved to ensure batch-to-batch consistency.

8. Technical Specifications Table

Parameter	Specification (Standard Blown Grade)
Appearance	Amber to Brown, Clear Viscous Liquid
Viscosity (at 25°C)	15 – 50 Stokes (Customizable)
Acid Value (mg KOH/g)	5.0 – 15.0
Iodine Value (Wijs)	50 – 75 (Lower than refined oil)
Saponification Value	190 – 210
Hydroxyl Value	145 – 155
Color (Gardner)	9.0 Max
Specific Gravity (at 30°C)	0.985 – 0.995

9. Quality Grade Analysis

The primary indicator of quality in Blown Castor Oil is Viscosity Stability. Inferior blown oils often continue to polymerize in the drum, leading to “gelation” over time. Nova Industries uses specialized stabilization techniques to ensure that the viscosity remains constant throughout the shelf life of the product.⁹

10. Impact of Impurities

• Moisture: High moisture during the blowing process can lead to erratic acid values and poor clarity.

• Incomplete Oxidation: Results in an oil that acts like standard castor oil, which may migrate out of the polymer matrix in plasticizer applications.

11. Industry-Wise Application 1: Coatings & Lacquers

Blown Castor Oil is the industry standard plasticizer for Nitrocellulose (NC) Lacquers. It provides a “permanent” plasticity that does not evaporate or migrate, ensuring the coating remains flexible and crack-resistant for years.¹⁰ It is widely used in wood finishes and nail polishes.

12. Industry-Wise Application 2: Printing Inks

Used as a binder and pigment dispersant in lithographic and screen-printing inks.¹¹ Its high tack and viscosity improve the transfer of ink from the roller to the substrate and provide a high-gloss, durable finish.

13. Industry-Wise Application 3: Lubricants & Greases

Acts as a lubricity improver and tackifier in industrial lubricants.¹² It is particularly effective in “stay-put” lubricants for chains, open gears, and wire ropes where resistance to centrifugal slinging is required.

14. Industry-Wise Application 4: Caulks & Sealants

Incorporated into oil-based caulks and glazing compounds to provide flexibility and prevent the compound from becoming brittle over time.

15. Formulation Guide

• Dilution: If the viscosity is too high for handling, Blown Castor Oil can be thinned with aromatic solvents or esters before incorporation.

• Blending: For plasticizer use, typically 10–25% of the total resin weight is recommended, depending on the required flexibility.

16. Sustainability Data

Blown Castor Oil is 100% bio-based and renewable.¹³ It contains no volatile organic compounds (VOCs) and is a non-toxic alternative to petroleum-derived polymeric plasticizers.

17. Packaging & Logistics (Technical)

• Standard: 200kg New Steel or HDPE Drums.

• Bulk: 1000kg IBC Tanks.

• Storage Stability: Stable for 12 months; however, it should be kept in a cool area to prevent natural oxidative aging.

18. Storage Science

Due to its high viscosity, Blown Castor Oil can become difficult to pour at low temperatures. It is recommended to store drums in a warehouse maintained above 20°C. If the oil thickens due to cold, gentle warming (not exceeding 50°C) will restore its flow properties.

19. Troubleshooting Guide

• Problem: Haze in NC Lacquer. Solution: Ensure the solvent balance is correct; Blown Castor Oil requires sufficient active solvents (esters/ketones) for full integration.

• Problem: Unexpected viscosity increase in storage. Solution: Keep drums tightly sealed to prevent further atmospheric oxidation; avoid storage in direct sunlight.

20. Regulatory Compliance

Our Blown Castor Oil is REACH Compliant and meets the safety requirements for use in various industrial and consumer-facing applications globally.¹⁵

21. Safety (SDS Summary)

• Handling: Use standard industrial PPE. The oil is non-hazardous.

• Fire: Use foam or CO2 extinguishers. The high flash point (>280°C) makes it very safe against accidental ignition.

• Environment: Biodegradable; avoid large-scale spills into wastewater systems due to high viscosity.

22. Sample Validation Process

For procurement approval, we recommend testing the Viscosity and Acid Value. For plasticizer users, a “compatibility film test” with the target resin is recommended to verify that no migration occurs after 48 hours.

23. Commercial Efficiency

By sourcing stabilized Blown Castor Oil from Nova Industries, manufacturers eliminate the risk of “in-drum gelation.” This ensures that every drop of the material can be used in production without waste, reducing overall material costs.

24. Technical FAQs

1. What is the difference between Blown and Raw Castor Oil? Blown oil has a much higher viscosity and better non-migratory properties due to its polymerized structure.¹⁶

2. Does Blown Castor Oil yellow? It is naturally amber-colored; however, it has good color stability once incorporated into a cured film.

3. Can it be used in water-based systems? No, it is strictly for solvent-borne or 100% solid systems unless pre-emulsified.

25. Contact CTA

For Technical Data Sheets (TDS), specific viscosity targets (from 15 to 150 Stokes), or to request a sample, please contact our export department: export@novaind.in