Leveling agent is a kind of coating additive, which can make the surface of the coating smooth and smooth after application, and reduce defects such as waves and bubbles on the coating surface. Leveling agent is generally a kind of polymer organic compound, its function is to reduce the surface tension of the coating, thereby reducing the liquid aggregation and bubble formation on the coating surface, and making the coating surface smoother. The amount of leveling agent used in coatings is small, usually only 0.1% to 1% needs to be added, but for some high-demand coating products, the selection and addition of leveling agent are very important.
Testing performance and standards
The following are the properties that leveling agents need to detect and the corresponding detection methods, as well as possible detection standards:
| performance | Detection method | Testing Standard |
|---|---|---|
| Exterior | Observe the appearance of the sample | - |
| viscosity | Rotational viscometer, trickle method, direct stretching method, etc. | - |
| density | Density meter | - |
| Solubility | Solubility test | - |
| volatility | oven method | ISO 3251, ASTM D2369, GB/T 1728, etc. |
| drying time | Oven method, touch dry method | ASTM D1640, ASTM D869, ISO 9117, etc. |
| Leveling | Colorimeter, observation method, patch method, etc. | ISO 2813, ASTM D523, JIS K 7105, GB/T 9754, etc. |
| Adhesion | Cross-hatch method, peel test | ASTM D3359, ASTM D6677, GB/T 9286, etc. |
| wear resistance | Abrasion testing machine | ISO 7784, ASTM D4060, JIS K 7204, GB/T 1768, etc. |
| chemical resistance | Chemical Resistance Test | - |
| heat resistance | Constant temperature oven method, high temperature expansion test | ASTM D2485, ISO 10524, GB/T 19547, etc. |
| Moisture resistance | Constant temperature and humidity test | ASTM D2247, GB/T 1740, etc. |
| Lightfastness | Light aging test, ultraviolet aging test, artificial weather aging test, salt spray test, etc. | ASTM G154, ASTM G155, GB/T 1865, etc. |
| Antioxidant | High temperature oxidation test | ASTM D7528, GB/T 21774, etc. |
| low temperature flexibility | Low temperature bending test | ASTM D522, GB/T 6742, etc. |
It is necessary to select appropriate detection methods and standards according to different types of leveling agents and application scenarios, and pay attention to the accuracy and repeatability of detection.
Detection method
The following are the properties and corresponding detection methods that need to be tested for leveling agents:
Appearance: Observe the appearance of the sample and check whether there are any adverse phenomena such as color difference, suspended solids, and precipitation.
Viscosity: It can be measured by various methods such as Rotational Viscometer, trickle method, direct stretching method, etc. The Rotational Viscometer can measure the viscosity, fluidity and other properties of the leveling agent; the trickle method can be used to test the flow performance of the coating, usually using a centrifugal drip meter or a tube drip meter; the direct stretching method is suitable for the measurement of high viscosity coatings.
Density: Use a density meter to measure the density of the leveling agent, usually a metering tube type density meter or an electronic density meter.
Solubility: Solubility test can be carried out, the leveling agent is mixed with the solvent and observed and judged, and it can also be analyzed by GC-MS and other instruments.
Volatility: The oven method can be used to measure the volatility of the coating. According to certain temperature and time conditions, the quality change of the coating can be measured, and the volatile content can be calculated. Testing standards include ISO 3251, ASTM D2369, GB/T 1728, etc.
Drying time: It can be measured by oven method, touch drying method and other methods, and the drying time can be evaluated according to the degree of drying of the paint. Testing standards include ASTM D1640, ASTM D869, ISO 9117, etc.
Leveling: It can be measured by color difference meter, observation method, patch method and other methods to evaluate the flatness and gloss of the coating surface. Testing standards include ISO 2813, ASTM D523, JIS K 7105, GB/T 9754, etc.
Adhesion: It can be measured by cross-cut method, peel test and other methods to evaluate the bonding strength between the coating and the substrate. Testing standards include ASTM D3359, ASTM D6677, GB/T 9286, etc.
Abrasion resistance: It can be measured by an abrasion testing machine to evaluate the abrasion resistance of the coating. Testing standards include ISO 7784, ASTM D4060, JIS K 7204, GB/T 1768, etc.
Chemical resistance: The chemical resistance test can be used to test the resistance of the coating to chemical reagents by soaking in chemical reagents.
Water resistance: It can be measured by immersion test, spray test and other methods to evaluate the resistance of the coating to water. Testing standards include ISO 2812-2, ASTM D2247, JIS K 5600-7-1, GB/T 1733, etc.
Weather resistance: It can be measured by artificial weather aging test, natural weather aging test and other methods to evaluate the durability of the coating under different climatic conditions. Testing standards include ASTM D4587, ISO 11507, JIS K 5600-5-7, GB/T 1865, etc.
Fire resistance: It can be measured by flammability test, combustion test and other methods to evaluate the fire resistance performance of coatings. Testing standards include ASTM E84, GB/T 8626, etc.
VOC content: It can be measured by gas chromatography to evaluate the content of volatile organic compounds in the coating. Testing standards include ASTM D6886, JIS K 0561, GB/T 23985, etc.
