Ultimate Guide to Oil Absorption Value: The Key Indicator Deciding the Performance and Cost of Inorganic Powders
Oil absorption value refers to the volume (in milliliters) of a specific liquid (commonly linseed oil or castor oil) absorbed by 100 grams of powder material when it reaches a specific viscous state (such as forming uniform clumps). The unit is usually mL/100g.
This indicator is generally determined according to standard methods (such as GB/T 5211.15 or ASTM D281), by adding liquid dropwise while stirring until the powder and liquid are completely mixed into a uniform, non-dispersed, and non-sticky agglomerate.
The significance of oil absorption value in inorganic powder materials: Oil absorption value is a key indicator reflecting the physical properties and surface properties of inorganic powders, and it has a significant impact on their application performance, mainly in the following aspects:
Specific surface area and pore structure
The larger the specific surface area and the higher the porosity (especially open pore structure) of the powder, the higher the oil absorption value usually is.
For example, nano-sized powders (such as nano-calcium carbonate) have significantly higher oil absorption values compared to products with ordinary particle sizes.
Particle Morphology and Aggregation State
Particles with irregular shapes, rough surfaces, or multiple edges have higher oil absorption values; spherical or dense surfaces have lower oil absorption values.
Porous, hollow, or loosely aggregated powders (such as precipitated silica and porous silica) have significantly higher oil absorption values than solid, dense particles.
Surface Properties
Surface energy, polarity, and whether or not surface treatment is performed all affect oil absorption values.
For example, after surface modification with organic substances such as stearic acid, the powder changes from hydrophilic to hydrophobic, and the oil absorption value usually decreases.
Importance in Practical Applications
Oil absorption value is one of the core parameters for downstream product formulation design and production processes, directly affecting the following aspects:
Processing and Performance of Composite Materials (Plastics, Rubber, etc.)
High oil absorption value powders require more resin or polymer for wetting and encapsulation; otherwise, it will lead to increased system viscosity, poor flowability, increased energy consumption, and potentially reduced mechanical properties of the final product.
Low oil absorption value powders are easy to disperse, helping to reduce resin usage, lower costs, and improve processing flowability.
Performance Control of Coatings and Inks
Oil absorption value affects the critical pigment volume concentration (CPVC), gloss, flowability, hiding power, and durability of coatings. Excessively high oil absorption value can lead to excessive viscosity and poor color development.
Cost Control
Oil absorption value is directly related to the amount of matrix materials (resins, oils, etc.) used in the formulation and is a key factor affecting overall cost.
Evaluation of Surface Modification Effects
Changes in oil absorption value are often used to evaluate the effect of powder surface modification; successful modification usually reduces the oil absorption value.
Summary
Oil absorption value can be considered a "physical fingerprint" of inorganic powders, comprehensively reflecting their particle size distribution, specific surface area, particle morphology, pore structure, and surface properties. When selecting powders, it is necessary to consider the downstream application's process requirements and product performance, and reasonably refer to the oil absorption value index to achieve optimized formulation design, processing performance, and cost control. Generally speaking, the lower the oil absorption value, the less liquid the powder requires in the matrix, resulting in better processing flowability and facilitating high-filling and low-cost production.
