What are the factors that affect the stain resistance of paint film?
Paint industry:
In contemporary coatings and painting processes, for coatings applied in environments such as architectural coatings, stain resistance has undoubtedly become a key indicator affecting the appearance, stain resistance, durability, and other key parameters of the paint film. This article will analyze the factors that affect the stain resistance of coatings.
1. Film forming material and stain resistance performance
Glass transition temperature (Tg): Tg is an important factor affecting the stain resistance of paint films, especially for thermoplastic coatings. A higher Tg indicates a higher hardness of the paint film and relatively better stain resistance.
Introduction of other compounds for modification: improve the stain resistance of the paint film through modification, such as the use of organic-inorganic composite coatings, the use of silica sol and styrene acrylic lotion or water glass styrene acrylic lotion combination, to improve the density of the paint film and reduce porosity.
2. Volume concentration of pigments in the coating system (PVC)
Usually, as the PVC content of the coating system increases, the dust accumulation and fouling of the paint film decrease. This characteristic continues until PVC equals CPVC (critical pigment volume concentration), which is consistent with the argument that "dust accumulation and fouling are caused by the adhesion of thermoplastic polymer film-forming substances in the coating". When PVC rises, the amount of polymer on the surface of the coating decreases accordingly; When PVC>CPVC, the paint film becomes porous and the stain resistance of the paint film significantly decreases.
3. Selection of additives
Emulsifier: Traditional emulsifiers may migrate to the surface of the paint film, causing it to become soft, sticky, and easily contaminated with dust. The new polymerizable emulsifier can react with monomer during lotion polymerization to improve the stain resistance of paint film.
Thickener (protective adhesive): such as polyvinyl alcohol (PVA) will remain in the paint film, making it sensitive to water, sticking back, and adsorbing dust. Using sodium polyacrylate as a protective adhesive can avoid these problems.
The addition of stain resistant agents: Adding stain resistant agents can improve the stain resistance of paint films, but due to their potential adverse effects on the physical and chemical properties of paint films and increased costs, caution should be exercised when using them.
4. Surface roughness of paint film
Many people intuitively believe that rough paint film surfaces are more prone to dust accumulation. However, experiments have shown that when other factors remain constant and surface roughness is only changed by altering the size of aggregate particles in the coating, this roughness change has little effect on dust accumulation and fouling. The main factor affecting the dust and dirt accumulation of paint film is still PVC rather than surface roughness.
Understanding these factors and mastering relevant processing techniques is beneficial for the paint coating industry to provide standardized references for the testing and evaluation of paint stain resistance performance, as well as to scientifically and effectively control various aspects such as research and development, production, and construction. At the same time, it enhances the professionalism of practitioners and provides support for building a good paint industry.
