Coating is an important material widely used in construction, industry and home decoration. The problem of skinning has always been a serious challenge during the production and storage of Coating. Skinning refers to the drying film formed on the surface of Coating. It appears when it is uncomfortable during storage or use, which may cause the Coating mass to decrease and affect the construction effect. This article will discuss the skinning properties and control methods in oxidation drying varnishes and Paints.
The skinning tendency of oxidation drying varnishes and Paints in storage is a key test item for storage stability. Skinning is not only an Appearance problem, but more importantly, it will affect the composition and color base ratio of Coating, thereby directly affecting the film formation performance of Coating. In addition, skinning may also lead to Miscellaneous problems in Coating, such as gel, deterioration, etc., which further reduces the mass of Coating, which may lead to a decrease in construction mass and increase production costs.
The measurement of skinning usually involves two aspects: one is to measure the skinning possibility of Coating under closed conditions, and the other is to measure the skinning speed under open cover conditions.
Closure test
The airtight test is usually carried out using a 125mL wide-mouth grinded glass bottle or a 0.33L lacquer can. The sample is loaded into a bottle or lacquer can, the volume is about 95mL, and the sample in the lacquer can should be 15mm away from the top of the can. Afterwards, store it in the dark at 23 ℃ ± 2 ℃ for 48 hours, and then open the bottle or can cap to check for skinning. If no skinning is observed for three consecutive 48-hour periods, it can be confirmed that the Coating is not skinning. Alternatively, the lacquer can can be stored in the natural environment at room temperature for one year in the dark, and then checked for skinning to more fully assess skinning.
Open tank test
The open tank test is a more on-the-spot test method in which the specimen is loaded into a paint can to half the depth of the paint can and the lid is kept open. During the test, it is necessary to observe from time to time until skinning is observed. To better assess skinning, it is best to test with samples of known properties at the same time and compare the skinning of the two at different stages.
To control skinning in oxidation drying varnishes and Paints, the following measures can be taken:
Use anti-skinning additives
Adding anti-skinning additives to the formulation of Coating can effectively reduce the occurrence of skinning. These additives can interfere with the chemical reactions in which skinning is formed, thereby delaying or preventing the formation of skinning.
Optimize storage conditions
Closed storage and protection from light are important factors in reducing skinning. Ensuring that storage containers are sealed and protected from light, avoiding direct sunlight and high temperature environments, can reduce the risk of skinning.
Regular inspection and testing
Regular closed test and open tank test of Coating can detect skinning problems in time and take measures to repair or improve the formula.
Adopt a stable production process
During the production process, controlling factors such as the pH value of the Coating, solvent selection and additive usage can help reduce the risk of skinning.
Skinning is an important mass problem in oxidation drying varnishes and Paints, which will affect the stability and construction effect of Coating. Through appropriate test methods and control measures, the occurrence of skinning can be reduced or prevented. This is essential to ensure Coating mass and improve construction effect, and needs to be paid attention to during Coating production and storage. Through continuous research and practice, we can continuously improve Coating formulations and production processes to meet the challenges posed by skinning and provide more possibilities for the development of the Coating industry.