Key Points Note
Paint is designed to “wetting, adhesion, and hardening” on any surface it’s applied to. As a result, paint technology has evolved to meet these necessary conditions.
The necessary requirements of paint
Paints are designed to flow, adhere, and solidify, which can be summarized as “wetting, adhesion, and hardening” They have different sufficient conditions related to film properties, durability, and weather resistance (maintainable physical properties over time). Here, we will explain these three conditions that paints require.
1. Wetting – Flowing
Paint is applied to the substrate, flowing to create a smooth appearance, but powder coatings struggle with leveling flow. “Orange peel” indicates insufficient leveling, while “runs” signify excessive flow. Therefore, achieving a finish just before runs occur is desirable. Additionally, paint encounters air during flow, making surface tension important.
The “adhesion” requirement of paint can be likened to how your finger sticks to ice when you press it against it, whereas oily fingers quickly come off.
Paint can be classified into two types: chocolate-type and cookie-type. These differences become evident when heated. When heated, chocolate-type paint becomes fluid, while cookie-type paint doesn’t flow and tends to burn. Similarly, when paint is heated, it can be categorized into chocolate-type and cookie-type. Chocolate-type paint dries quickly and can be easily removed with solvents. On the other hand, paint that forms a cookie-type film is typically a two-component or baked-type paint, where the main resin components or main resin and hardener undergo a chemical reaction after application, increasing the molecular weight of the paint film. There are also dispersion-type paints where particles fuse together.