The importance of the glass transition temperature (Tg) of acrylic resins, which are commonly used in coating formulations, is briefly described as an example
The glass transition temperature (Tg) is the lowest temperature at which the polymer chain segments can move, and is directly related to the flexibility of the molecular chains. For acrylic resins commonly used in coating formulations, the film becomes soft above its glass transition temperature, so they are usually used below the glass transition temperature, so we also want to use acrylic resins with a higher glass transition temperature. The glass transition temperature (Tg) of acrylic resins is a very important technical indicator, which must be designed and selected correctly, and its importance is mainly expressed in the following aspects.
One, the engineer in the design of paint formulations with acrylic resin, once the coating species, performance and other comprehensive requirements to determine the glass transition temperature of acrylic resin Tg, basically also determines the choice of synthetic resin monomer, but also basically determines the performance of acrylic resin and paint after the performance of the paint. The higher the Tg value of the acrylic resin, the better the solvent and corrosion resistance of the coating film; conversely, the lower the Tg value of the resin, the worse the corrosion and solvent resistance of the coating film. Therefore, among the many technical indicators of acrylic resins, the Tg value has a greater impact on the resin and the performance of the coating film.
Second, under the same acrylic resin synthesis reaction conditions, the higher the Tg of the resin, the greater the final viscosity of the resin reaction, that is, the higher the average molecular weight; conversely, the lower the Tg of the resin, the lower the final viscosity of the resin reaction, that is, the lower the average molecular weight.
The higher the Tg value, the harder the film and the stronger the scratch resistance, but care should be taken to adjust the paint formulation and not to make the film brittle; conversely, the lower the Tg value, the lower the film hardness and the worse the scratch resistance. We often encounter high temperatures in summer when the film is easy to become soft, back to sticky, easy to be contaminated phenomenon, which is the film-forming resin Tg high or low impact on the film hardness and scratch resistance of the visual performance.
Fourth, the higher the Tg of the acrylic resin, the better the solvent release of the coating, the better the dry rate of the film after painting; conversely, the worse the solvent release, the worse the dry rate of the film after painting the resin.