The following is a comment on thermosetting acrylic resin. The thermosetting acrylic resin available now not only has typical acrylic resin functions, but also has higher construction solids and better chemical resistance compared with thermoplastic acrylic resin.
Acrylic resin is the second kind of resin commonly used in coatings because of its chemical characteristics, many monomers to choose from, and it can use a variety of polymerization methods and get different flexibility in design. It has the ability to use two or more monomers to get different copolymers, and then it can get new products with the same useful function. The function depends on the composition and share of monomers, and also depends on the preparation method.
Acrylic polymers can be synthesized by bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization. When water is used as solvent in suspension polymerization, the polymerization temperature should not exceed 100 ℃ °， However, the development of low solvent coatings requires resin with very low viscosity, so the reaction temperature should be 100 ℃ ° Therefore, bulk and solution polymerization are used in the production of low viscosity polymer. The main parameters determining the viscosity of the base material are the relative molecular mass and the relative molecular mass dispersion. The approximate solid composition of different molecular weight under construction viscosity is as follows:
In order to protect the environment, people have developed alkyd, vinyl compounds, acrylate, polyester, epoxy or polyurethane coatings with high solid content, which generally contain more than 70% solid content to meet the pollution constraints and reduce energy consumption. Although great progress has been made in waterborne systems and powder coatings, solvents are still indispensable in many applications.
In the development of high solid and high functional coating system, it is necessary to reduce the relative molecular weight of base material and develop and establish an oligomer system. The key is that the thermosetting acrylic acid should be a hybrid polymer, in which one component supplies hardness, another component supplies flexibility, and the third component contains active functional groups, which can be used for crosslinking. Sometimes other monomers can be introduced into the main chain of polymer to improve some special functions. They can be self reactive (e.g. resins containing glycidyl and hydroxymethyl groups) or potentially reactive (e.g. resins containing carboxyl and hydroxy groups)