Polyurethane (PU) wood coatings dominate the wood finishing market due to their excellent hardness, abrasion resistance, and chemical resistance. Based on the classic formulation provided, this article details the main components, functions, and key mixing ratios of PU Wood Paint. This information is vital for small-to-medium paint manufacturers looking to optimize their products and for purchasers seeking stable, quality suppliers.
The Classic Three-Component Structure of PU Wood Paint
PU wood coatings typically exist as Two-Component (2K) systems, consisting of the Main Agent, Hardener, and Thinner, which must be mixed in the specified ratio before application.
Core Mixing Ratio: Main Agent : Hardener : Thinner = 1 : 0.5 : 0.9
PU Wood Paint Main Agent
The Main Agent contains the film-forming material, solvents, and various additives, which determine the final performance and appearance of the paint film.
| Component | Function | Key Insight |
| Alkyd Resin | Film-forming substances provide basic hardness and adhesion. | Alkyd resins are the main resins that provide the skeleton of the paint film. |
| Xylene & BAC | Dissolve the solid components in the main agent and adjust the viscosity. | They are the main active solvents in the main agent. |
| Matting Powder | Reduce gloss to achieve a matte or semi-matte finish. | Determines the gloss level of the final paint film |
| Additives: Leveling Agent & Defoamer | Improve the application properties of coatings, such as preventing defects like pinholes and bubbles. | High-performance wood coatings have extremely high requirements for additives. |
PU Wood Paint Hardener
The Hardener contains Isocyanate components, which react with the hydroxyl groups $(\text{OH-})$ in the Main Agent to form a robust polyurethane network, giving the film excellent durability.
| Component | Function | Key Insight |
| TDI Adduct Hardener | Provides active isocyanates to participate in cross-linking. | Commonly used curing agents are characterized by high reactivity and fast curing. |
| Trimer Curing Hardener | Provides a more stable cross-linking structure | The type of hardener affects the hardness and yellowing resistance of the paint film. |
| BAC | diluent for curing agent | Ensure the curing agent is evenly dispersed in the base agent. |
PU Wood Paint Thinner
The Thinner is used to adjust the viscosity of the mixed Main Agent and Hardener to a range suitable for spraying or brushing, and to control the drying rate of the paint film.
| Component | Function | Key Insight |
| BAC | Active diluent, providing good solubility | |
| Xylene | The main diluent affects drying speed and cost. | A high proportion of solvent helps with rapid drying, but attention should be paid to ambient temperature and leveling. |
| CYC | High-boiling-point cosolvents help with leveling and improve gloss. | High-boiling-point solvents help with paint film leveling. |
Focus Points for Purchasers and Manufacturers
- Performance Balance: Purchasers should pay attention to the type of hardener (such as anti-yellowing hardener) and the quality of additives (such as leveling agents and defoamers), as these directly determine the final coating effect and service life.
- Cost vs. Solvents: The high proportion of xylene in the diluent can reduce costs, but its ratio must be strictly controlled to balance drying speed, environmental impact, and leveling effect.
- Environmental Compliance: The formula contains organic solvents such as xylene and methyl ethyl ketone (MEK), which fall under the category of VOCs (Volatile Organic Compounds). Small and medium-sized factories must strictly comply with local VOC emission regulations during production.
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