Properties and Influencing Factors of Photosensitive Coatings
Polymer photosensitive coating, also known as polymer photocurable coating, contains photosensitive components or structures, using light as the initiator to initiate polymerization or crosslinking reactions, so as to achieve the purpose of photocuring.Compared with the problems of environmental pollution and long curing time existing in the use of ordinary coatings, polymer photosensitive coatings can be quickly dry film formed by light irradiation of appropriate wavelength, and can reduce environmental pollution and reduce material consumption. Therefore, it is widely used in wood and metal surface protection and decoration, as well as the printing industry and other fields, and is increasingly widely used in optical devices, liquid crystal display and other special fields.
Structure types of photosensitive coatings prepolymer
Photosensitive coating is the main component of prepolymer, other also include crosslinking agent, thinner, photosensitive agent or photoinitiator.Prepolymers are usually oligomers of small molecular weight, generally including:
- Epoxy oligomer: Common photosensitive coating prepolymer, strong adhesion, corrosion resistance.
- Unsaturated polyester: Tough, high hardness, good solvent resistance.
- Polyurethane: Strong adhesion, wear resistance, tough, but easy to yellowing under ultraviolet radiation.
- Polyether: Intermolecular force is relatively small, belongs to low viscosity coating, the price is lower.
Main properties and influencing factors of photosensitive coatings
- Flow performance: coating viscosity, surface tension, moisture are the main factors affecting flow performance. Add surfactant to adjust surface tension and moisture content.
- Mechanical properties: mainly depends on the type of resin in the coating and the degree of polymerization and crosslinking of the curing film.
- Chemical stability: depends on the chemical composition of the paint. For example, polystyrene systems have good corrosion resistance to polar solvents and aqueous solutions.
- Coating gloss: the main factor that affects glossiness is the content of extinction agent and the surface tension of coating. Reducing gloss can add dimming agent, increase surface tension can improve the finish of the coating.
- Binding force: the factors affecting the binding force include the compatibility between the coating and the substrate, the interface contact degree, the surface tension of the coating, curing conditions, etc.
Factors affecting curing of photosensitive coatings
Photosensitive coating solidify is to point to fall in illumination, the monomer in coating, oligomer, polymer matrix produces crosslinking reaction below the action of photosensitive agent, make coating becomes film quickly. The factors affecting the curing of photosensitive coatings are as follow:
- Light source: the selection parameters of light source include wavelength, power and illumination time. It is common to use ultraviolet light as the light source for most photoinitiators. Increasing the power of light source can accelerate the curing speed. The time of illumination depends on the curing rate of the coating and the thickness of the coating.
- Mechanical properties: mainly depends on the type of resin in the coating and the degree of polymerization and crosslinking of the curing film.
- Photoinitiator and photosensitizer: according to the wavelength of the light source and the type of paint to be considered comprehensively.
- Influence of environmental conditions: oxygen in the air has the effect of blocking polymerization, so it is conducive to curing reaction in inert atmosphere.The curing speed and degree are also affected by temperature.
