Solvent-based volatile acrylic paints rely on solvent evaporation to dry, while thermosetting paints have cross-linking reactions of functional groups in addition to solvent evaporation. Some require heating and baking for cross-linking, while others can cross-link at room temperature. Thermoplastic paints have a low solid content during construction, usually 15% to 25%, and a thin film. Their decorative and fullness rely on multi-layer coatings, and their physical properties are often slightly worse than the latter. However, their outdoor durability, gloss retention, and color retention are not inferior. Due to the ease of construction, they still have a large application area. Thermosetting paints have excellent performance in all aspects, so their application area is becoming increasingly broad. In short, solvent-based acrylic paints are booming based on their excellent performance.
(I) Thermoplastic acrylic paint
The copolymer resin used in thermoplastic acrylic paint will not further cross-link during film formation. In order to have better physical properties, the molecular weight is usually large, but in order not to make the solid content too low, it cannot be too large. It is generally between 75,000 and 120,000. Such a molecular weight often makes the solid content of the paint between 15% and 25% at the construction viscosity. In order to meet the performance characteristics required by various uses, thermoplastic acrylic paint must be adjusted by adjusting the monomer ratio in the resin formula, or modified by adding other film-forming materials that are compatible with it.
(1) Advantages
① Excellent weather resistance. Outdoor durability is far better than nitro, alkyd, vinyl and other products. When the monomer is properly formulated, it is not inferior to thermosetting acrylic paint.
② Excellent gloss and color retention. The resin is water-white and has high transparency. It is not easy to fade or change color under ultraviolet light. It is most suitable for making aluminum powder (metallic) topcoat and light-colored topcoat.
③ Good chemical and water resistance, good acid and alkali resistance; not contaminated by grease and road petroleum asphalt, and has strong resistance to detergents.
④ Good adhesion when matched with appropriate primer.
⑤ Good polishing properties.
2. Application of thermoplastic acrylic paint in industry
Although thermoplastic acrylic paint is slightly inferior to thermosetting varieties in some properties, its main performance of atmospheric aging resistance is very good, so it is widely used in various fields.
In terms of construction, whether it is exterior walls, aluminum frames, bridge railings, TV towers and other engineering facilities, they are all exposed to strong sunlight for a long time, and require excellent atmospheric aging resistant coatings for finishing. However, these engineering facilities and products cannot be baked and dried, and can only be finished with thermoplastic volatile self-drying coatings. Similarly, the renovation and repair of various vehicles cannot be baked at high temperatures because many rubber, plastic parts and instruments are already installed on the vehicle; in addition, there are secondary processed products of plastic products and wood products. If they are required to have certain atmospheric aging resistance, thermoplastic acrylic paint is the ideal coating.
Thermosetting acrylic paint
Compared with thermoplastic, the main advantage of thermosetting acrylic paint is that the molecules of the paint film are transformed into a huge mesh structure through curing and cross-linking, which is insoluble and insoluble, and improves its various physical properties and corrosion resistance and chemical resistance. In addition, since the original molecular weight of the coating resin is much smaller, a high-solid coating can be made at a not too high viscosity, thereby improving the fullness of the coating film, reducing the number of construction passes, and achieving the ideal film thickness. The molecular weight of thermosetting coating resin is usually below 30,000, generally between 10,000 and 20,000, and the resin used in high-solid coatings is often as low as 2,000 to 3,000.
The cross-linking reaction of thermosetting acrylic resin is through the active functional groups on the side chains of the resin that can react with other resins or react with themselves. Different active functional monomers are used in the manufacture of resins by copolymerization, so that the side chains of the resin have functional groups of various different cross-linking systems.
Our company has Weller thermoplastic saturated copolyester, which is very suitable for PET, PC, PA, TPU film products that require high tensile toughness and excellent adhesion, IMD/IML molding decorative panels, FPC flexible circuit boards, electronic touch screen conductive inks, various alloys and special oxidized metal nameplates, metal aluminum foil coloring inks and other fields. It has high and low temperature impact resistance, yellowing resistance, salt spray resistance, excellent physical properties and chemical corrosion resistance.
