With water-based paints increasingly becoming part of our daily lives, most people are familiar with them. Here are some tips on using water-based paints, hoping to be helpful.
1. Types and Application Techniques of Water-Based Wood Coatings
Through analysis of water-based wood coatings sold on the market, the application techniques of water-based wood coatings can be roughly categorized by the type of base material as follows:
① Acrylic type: including styrene-acrylic emulsion and (modified) acrylic emulsion, suitable for primers and matte topcoats. Coatings made from this base material are relatively low in cost and have moderate hardness. They are not prone to shrinkage, but their film-forming properties are poor, the gloss is poor, and they are not suitable for high-gloss paints. The abrasion resistance is poor, and defoaming is difficult. They are generally used in blends; ② Polyurethane dispersions: including aromatic and aliphatic polyurethane dispersions. The latter has excellent yellowing resistance and is more suitable for outdoor use. They all have good film-forming properties, high self-crosslinking gloss, good abrasion resistance, and are not prone to bubbles and shrinkage. However, the hardness is moderate, and the price is relatively high. They are suitable for high-gloss topcoats, floor paints, etc.; ③ Acrylic-modified polyurethane dispersions: including mixtures of aromatic and aliphatic polyurethane and acrylic dispersions, combining the advantages of the above two types. The cost is moderate, and they can be self-crosslinking or used in two-component systems. They have good hardness, fast drying, abrasion resistance, good chemical resistance, low or no yellowing, and are suitable for bright semi-gloss paints, primers, and outdoor paints;
④ Water-based polyurethane oil: a single-component type, similar to oil-based polyurethane oil, oxidation-reduction drying type. A drier needs to be added during film formation. It dries quickly, has good gloss, good hardness, abrasion resistance, and good water resistance, suitable for high-gloss surfaces and floor paints; ⑤ Two-component water-based polyurethane: one component is a polyurethane dispersion with -OH; the second component is a water-based curing agent, mainly aliphatic. After mixing these two components for application, crosslinking reaction can significantly improve its water resistance, hardness, fullness, and gloss. It has good comprehensive performance, and the coating is not prone to yellowing, especially suitable for outdoor coatings.
2. Current Status of Product Technology
Water-based wood coatings on the market are divided into single-component and two-component types in terms of packaging, with single-component types accounting for the vast majority. In terms of sources, there are original imported products, products produced by foreign brands in China, and products independently researched and developed by domestic manufacturers. The former two are more common, while the latter has a smaller market share. Through analysis and testing of foreign brands, joint venture brands, and domestic products, their comprehensive product performance is as follows.
① Product appearance: There are milky white, slightly yellow, and slightly red viscous substances;
② Solid content: Generally 30%～45%, much lower than solvent-based types;
③ Water resistance: Aliphatic polyurethane dispersions and water-based polyurethane oils are much better than aromatic/acrylic emulsion types;
④ Alcohol resistance: The trend is basically the same as water resistance;
⑤ Hardness: Acrylic emulsion type is the lowest, followed by aromatic polyurethane as moderate, aliphatic polyurethane dispersions and their two-component polyurethane and polyurethane oil are the highest. The hardness gradually increases over time, especially for two-component crosslinking types. However, the hardness increase is slow and relatively low, far inferior to solvent-based types. There are very few that can reach H in pencil hardness;
⑥ Gloss: High gloss is difficult to achieve the gloss of solvent-based wood coatings, generally 20% lower. Among them, two-component types are higher, followed by polyurethane oil and polyurethane dispersions, and acrylic emulsion types are the lowest;
⑦ Fullness: Due to the influence of solid content, the difference is large. In addition, the solid content itself is low, and the fullness is poor. The higher the solid content, the better the fullness. Two-component crosslinking types are better than single-component types, and acrylic emulsion types are poor;
⑧ Abrasion resistance: Polyurethane oil and two-component crosslinking types are the best, followed by polyurethane dispersions, and then acrylic emulsion types;
3. Application Technology of Water-Based Polyurethane Paint
Water-based polyurethane paint, as a new type of green and environmentally friendly product, has only entered the Chinese market in recent years. Its greatest advantage is that it solves the problems of film fullness, feel and hardness, heat resistance, scalding resistance, alcohol resistance, water resistance, and pollution resistance that domestic consumers are concerned about from the application technology perspective;
It has overcome the weaknesses of water-based wood coatings; moreover, water-based polyurethane paints are not prone to bubbles during construction, are easy to sand, and are not easily affected by temperature and humidity, laying a solid foundation for comprehensively solving the market application of water-based wood coatings.