In coatings, inks and related industries, non-volatile content is a key physical parameter in product technical data sheets and formulation analysis. It describes the proportion of the solid portion of the product that can be retained on the substrate to form a paint film or coating after curing under specified conditions. This parameter is not directly equivalent to the final performance of the coating, but it is the basic data for connecting liquid products with solid paint films, for construction calculations and cost assessments.
This article will systematically explain the definition of non-volatile content, standard measurement methods, data interpretation and its application points in industry.
1. Definitions of terms
Non-volatile content, also known as solids or solid content, refers to the mass fraction of non-volatile substances remaining after physical drying or chemical curing of coatings, inks, or similar materials under specified conditions, usually expressed as a percentage.
Two related but different concepts need to be clearly distinguished -
Mass solids —— The non-volatile content expressed as a mass fraction is a commonly used indicator in daily production and quality control.
Volume solids —— The non-volatile content expressed as a volume fraction has direct application value for calculating the dry film thickness, theoretical coating rate and covering area.
The values of the two are usually not the same due to the difference in material density. For systems with high gloss or high pigment content, volumetric solids may be a more concerned indicator.
2. Measurement methods and instruments
Domestic and foreign standards have strict regulations on the determination conditions of non-volatile content to ensure the repeatability and comparability of the results. Core standards include the international standard ISO 3251, the Chinese national standard GB/T 1725, and the American Society for Testing and Materials standard ASTM D2369.
1. Principle of general measurement method
The basic principle of determination is to place a sample of a certain mass in an oven at a specified temperature and time to evaporate the volatile components, and then weigh the mass of the residue. The calculation formula is——
NV = (m₁ / m₀) × 100%
Among them, NV is the non-volatile content, m₀ is the initial mass of the sample, and m₁ is the residue mass after drying.
2. Key test conditions and equipment
Strict control of test conditions is a prerequisite for obtaining reliable data.
Temperature and time – different product types correspond to different combinations of standards. For example, for conventional solvent-based coatings, the common condition is to bake at 105℃ or 120℃ for a period of time. The baking time must be sufficient for constant quality.
Ovens – Precision ovens with forced convection or ventilation are used to ensure uniform temperatures and accelerate the escape of volatile substances.
Weighing equipment – Balances with sufficient accuracy are used, typically 0.1 mg or higher.
Specimen containers – flat-bottomed plates made of metal or glass, the size and material of which must comply with the standard.
| Examples of standard test methods | Main applicable objects and conditions |
| GB/T 1725 | It is suitable for color paints, varnishes and related products, and the sampling, weighing, baking and calculation methods are specified in detail. |
| ISO 3251 | The international common method, where the choice of conditions depends on the type of product, emphasizes the importance of achieving constant quality. |
3. Testing considerations for special materials
For some heat-sensitive materials, such as certain emulsions or UV curing systems, standard baking conditions can cause the resin to break down, resulting in low results. Therefore, the use of lower temperatures or different test methods (e.g. using infrared dryers, etc.) may be specified in the relevant standards or product specifications.
3. Data interpretation and analysis of influencing factors
The value of non-volatile content does not exist in isolation, and its interpretation needs to be combined with the material system and test conditions.
1. Relationship with formula composition
Non-volatile components mainly include film-forming substances (resins, polymers), pigments, fillers and non-volatile additives. The value directly reflects the total amount of active ingredients in the product that can form the final coating. In the same type of product, a higher non-volatile content usually means that more solids can be deposited per unit coating area.
2. Impact on construction and film formation
The non-volatile content, especially the volumetric solids, is the direct basis for calculating the theoretical coating rate and predicting the dry film thickness. Through its relationship with the thickness of the wet film, the thickness of the construction wet film required to achieve the target dry film thickness can be calculated backwards.
3. Key influencing factors in the test
Sampling and weighing accuracy - whether the specimen is uniform and whether the weighing is accurate is the basis.
Baking condition control – whether the temperature is uniform and the time is sufficient directly affects whether the volatile substances are completely removed.
Nature of residues – Some resins may experience slight oxidative weight gain during baking, or certain additives may volatilize and need to be considered when interpreting results.
4. Application points in all links of the industrial chain
The parameter of non-volatile content has different concerns in different industries.
Coatings and inks manufacturers – it is one of the core indicators of product formulation control, batch consistency quality inspection and cost control. By monitoring this parameter, you can ensure that the product meets specifications and control the cost of raw materials.
Coating construction and engineering acceptance party - The construction party mainly calculates the amount of material, estimates the coating area and controls the thickness of the dry film based on the volume of solids. In engineering, it is a key conversion factor that converts "price per liter" into "effective cost per square meter".
Research and Developers – When developing new products or performing reverse engineering analysis, non-volatile content is one of the basic data for analyzing formulation composition and estimating resin pigment ratios.
Summary
The value of non-volatile content as a fundamental and critical physical parameter is to provide a quantitative bridge from liquid products to solid paint films. Although it does not directly describe the gloss, hardness or durability of the coating, it is the material basis for achieving these properties. Accurately understanding its definition, standardizing its measurement method, and combining it with volumetric solids for rational application have clear practical value for the production, construction, R&D and trade of the coating ink industry. The standardized measurement of this parameter ensures the objectivity and consistency of technical exchanges and business activities in the industry.