1. Technical Overview
Oxidized or Modified Castor Wax (often referred to as Polyamide-Modified Castor Wax) is a high-performance rheological additive engineered for modern, high-solids solvent-borne systems. While standard Hydrogenated Castor Oil (HCO) relies purely on hydrogen bonding between hydroxyl groups, Modified Castor Wax incorporates additional functional groups—such as amides or oxygenated structures—to enhance its efficiency. These modifications provide superior sag resistance, better thermal stability during processing, and a wider “activation window,” making it the ideal choice for heavy-duty industrial coatings, automotive underbody sealants, and marine paints where standard waxes might fail due to high processing temperatures.
2. Chemical Structure & Composition
The structure of Modified Castor Wax is more complex than simple HCO:
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Base Backbone: Fully hydrogenated castor oil (Tri-12-hydroxystearin).
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Chemical Modification: Often “polyamide-modified,” where the wax is reacted with diamines to create amide linkages.
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Oxidation: In the oxidized variant, controlled aeration introduces polar oxygen groups along the fatty acid chain.
The introduction of amide groups ($–CONH–$) creates much stronger intermolecular forces than the simple hydroxyl bonds found in standard castor wax. This results in a more robust and temperature-resistant thixotropic structure.
3. Physical & Chemical Properties
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Appearance: Off-white to pale yellow flakes or powder.
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Melting Point: 105°C to 125°C (Significantly higher than the 85°C of standard HCO).
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Acid Value: 5.0 – 15.0 mg KOH/g.
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Hydroxyl Value: 130 – 150 mg KOH/g.
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Active Content: 100% (Solids).
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Specific Gravity: ~0.98 at 25°C.
4. Reaction Chemistry (Thermostable Thixotropy)
The primary advantage of Modified Castor Wax is its Resistance to Seeding:
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High-Temperature Activation: Unlike standard HCO which can “over-activate” and dissolve at 60°C, modified waxes maintain their fiber network at temperatures up to 75°C–80°C.
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Fiber Formation: The amide groups facilitate the formation of long, needle-like crystals that interlock more effectively in polar solvents (like Xylene, Butanol, and Esters).
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Shear Recovery: The modified network recovers its viscosity almost instantly after high-shear application (like airless spraying), preventing “sagging” on vertical surfaces.
5. When to Use vs. When NOT to Use
Use Modified Castor Wax when:
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Formulating High-Solids (Low VOC) coatings where standard rheology modifiers cause excessive viscosity increase.
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The manufacturing process involves high-speed grinding where temperatures exceed 60°C (preventing “seeding” or grit).
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Formulating Marine or Protective coatings that require thick film builds (300+ microns) in a single pass.
Do NOT use Modified Castor Wax when:
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Formulating low-cost decorative paints where standard FSG or HCO flakes are economically sufficient.
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The solvent system is purely aliphatic (like mineral spirits) with no polar content; modified waxes require at least a small percentage of polar solvent (e.g., Alcohols or Glycol Ethers) for activation.
6. Compatibility Profile
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Resins: Highly compatible with Epoxy, Polyurethane (PU), Chlorinated Rubber, and Short-oil Alkyds.
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Solvents: Optimized for aromatic hydrocarbons (Xylene/Toluene) and oxygenated solvents (MEK, MIBK, Butanol).
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Pigments: Excellent wetting properties for heavy pigments like Zinc Rich primers or Micaceous Iron Oxide (MIO).
7. Manufacturing Process (Product Focus)
Nova Industries utilizes a multi-stage synthesis for Modified Castor Wax:
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Hydrogenation: Castor oil is fully hydrogenated to form HCO.
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Modification/Amidation: The HCO is reacted with specific amines or subjected to controlled oxidation under high pressure and temperature.
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Quenching: The molten modified wax is rapidly cooled to freeze the crystalline structure.
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Finishing: The product is either flaked or micronized according to the specific application requirement.
8. Technical Specifications Table
| Parameter | Modified Polyamide Grade | Oxidized Grade |
| Appearance | Pale Yellow Flakes/Powder | Amber Flakes |
| Melting Point | 115°C – 125°C | 100°C – 110°C |
| Acid Value | 5.0 – 10.0 | 12.0 – 20.0 |
| Amine Value | 2.0 – 5.0 | N/A |
| Specific Gravity | 0.98 | 0.99 |
| Hydroxyl Value | 130 – 150 | 140 – 160 |
9. Quality Grade Analysis
The critical differentiator for Nova Industries’ Modified Wax is the Narrow Activation Range. We ensure that the modification is uniform across batches, preventing the common industry problem of “Variable Sag Resistance” where one batch of paint performs well and the next “runs” off the wall.
10. Industry-Wise Application: Automotive & Sealants
Modified Castor Wax is the cornerstone of Automotive Underbody Sealants (PVC Plastisols). It allows the sealant to stay in place even when the car body moves through high-temperature curing ovens. It provides the “Tack” and “Thixotropy” needed for robotic spray applications.
11. Industry-Wise Application: Protective & Marine Coatings
In heavy-duty anti-corrosive coatings (like those used on ships or bridges), this wax allows for the application of high-thickness layers without dripping. It also prevents the “Hard Cake” settlement of heavy zinc dust during long-term storage in 20-liter pails.
12. Formulation & Activation Guide
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Pre-Gel Method: Many users prefer creating a 10–20% “Pre-gel” by dispersing the wax in a solvent/resin mix at 70°C before adding it to the main batch.
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Direct Addition: If adding during the grind, ensure the temperature reaches at least 55°C (for Xylene-based systems) to ensure full activation of the amide-modified fibers.
13. Troubleshooting Guide
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Problem: “Seeds” or grit in the paint. Solution: The processing temperature was either too low to activate the wax or exceeded the “Safe Temperature Limit.” Switch to a higher-melting modified grade.
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Problem: Low gloss in the finish. Solution: You may be over-dosing the rheology modifier. Reduce the dosage and increase the shear during dispersion.
14. Regulatory & Safety
Our Modified Castor Waxes are REACH Compliant and meet the safety requirements for industrial manufacturing. They are non-hazardous, but as with all waxes, they should be handled in well-ventilated areas to avoid dust inhalation.
15. Contact CTA
For technical comparison sheets between standard HCO and Modified Grades, or to request a sample for your lab trials, please contact our technical division: export@novaind.in
