This comparison highlights the difference between a chemically modified industrial oil and a high-purity, naturally refined base oil. Below is the professional, A-to-Z comparison between Blown Castor Oil and Castor Oil (PP Grade),
Choosing between Blown Castor Oil and Castor Oil (PP Grade) is a choice between a specialized industrial modifier and a high-purity base oil. While both come from the same seed, they perform entirely different roles in manufacturing.
This article breaks down the technical specifications, processing differences, and industrial applications of these two essential grades.
Executive Summary
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Castor Oil PP Grade (Pale Pressed Grade) is a premium, highly refined oil obtained from the first pressing of the castor seed.1 It is prized for its light color, clarity, and low acidity.
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Blown Castor Oil (also known as Oxidized Castor Oil) is a derivative created by blowing air through refined oil at high temperatures.2 This process causes oxidative polymerization, significantly increasing the oil’s viscosity and “body.
Technical Specification Comparison Table
| Parameter | Blown Castor Oil (Oxidized) | Castor Oil PP Grade (Pale Pressed) |
| Appearance | Viscous, Amber to Brownish Liquid | Clear, Pale Yellow Viscous Liquid |
| Processing | Air Oxidation / Polymerization | Mechanical Pressing & Refining |
| Viscosity (@ 25°C) | 15 – 100 Poise (depending on grade) | 6.3 – 8.9 Poise |
| Specific Gravity | 0.960 – 1.000 | 0.958 – 0.969 |
| Acid Value (mg KOH/g) | Max 6.0 – 18.0 (higher) | Max 2.0 (very low) |
| Iodine Value | 55 – 82 (lower) | 82 – 90 |
| Hydroxyl Value | 140 – 160 | 160 – 168 |
| Color (Gardner / Lovibond) | Darker (Gardner Max 7-13) | Very Light (Lovibond Max 10Y/1R) |
| Solubility | Soluble in alcohols/organic solvents | Soluble in alcohols/organic solvents |
Key Differentiators: From A to Z
1. Viscosity and “Body”
The defining feature of Blown Castor Oil is its thickness. Through the blowing process, the oil becomes much heavier and stickier than standard oil.4 PP Grade maintains the natural, fluid viscosity of castor oil, making it easier to pump and mix in standard formulations.
2. Chemical Structure (Oxidative Polymerization)
Blown Castor Oil is chemically modified.6 The oxygen introduced during processing creates “oxygen bridges” between molecules, increasing its molecular weight.7 PP Grade is a “pure” triglyceride that has not been chemically altered, retaining the natural integrity of the ricinoleic acid.
3. Plasticizing Properties
Blown Castor Oil is a superior non-migrating plasticizer. Because of its high viscosity and polarity, it stays within a coating or film without “leaking” out. While PP Grade can act as a plasticizer, it is more likely to migrate in certain resin systems.
4. Pigment Wetting
In the world of inks and paints, Blown Castor Oil is exceptional at “wetting” pigments.9 It helps grind and disperse solid color particles more effectively than standard PP Grade oil, leading to smoother, more consistent coatings.
Industry Applications
Where to use Blown Castor Oil:
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Printing Inks: Used as a binder and plasticizer to improve “tack” and adhesion.10
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Lacquers & Varnishes: Provides flexibility and prevents cracking in nitrocellulose lacquers.11
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Adhesives & Sealants: Increases the body and sticking power of industrial glues.12
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Hydraulic Fluids: Used in specialized heavy-duty fluids where high viscosity and lubricity are needed.13
Where to use Castor Oil PP Grade:
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Pharmaceuticals: Used as a high-purity excipient and carrier oil for medications.14
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Cosmetics: The light color and low odor make it perfect for lipsticks, lotions, and hair oils.15
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High-End Coatings: Used in white or clear paints where a darker oil (like Blown oil) would ruin the color.
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Polyurethane Synthesis: Serves as a high-quality polyol for making resins and foams.16
Pros and Cons
Blown Castor Oil
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Pros: Extremely high viscosity, excellent film-forming properties, superior pigment wetting, non-migrating plasticizer.1
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Cons: Darker color, higher acid value, and specialized handling required due to thickness.
Castor Oil PP Grade
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Pros: Exceptional color clarity, very low acidity, high purity, highly versatile across many industries.
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Cons: Lacks the extreme viscosity and “tack” required for heavy industrial adhesives or thick inks.
The Verdict: Which one should you choose?
If your goal is to thicken a formulation, disperse pigments, or plasticize a heavy industrial coating, Blown Castor Oil is the correct choice.
If your application requires visual purity, low acidity, or is intended for personal care or pharmaceutical use, Castor Oil PP Grade is the industry standard.
