Лако-красочные материалы — производство

Reactive acrylate and methacrylate adhesives are solvent-free 100% polymer systems that comprise one-part and two-part systems, as well as anaerobic and UV-setting

adhesives. Reactive acrylate/methacrylate systems differ from physically setting acrylates/methacrylates by their curing mechanism, although they have a similar chemical base.

Acrylates and methacrylates are monomers or prepolymers with vinyl group-containing double bonds; these double bonds are subsequently attacked by free radicals to initiate the polymerization reactions in different ways (Figure 5.22).

The monomers are clear, colorless, low-viscosity liquids, while the prepolymers are highly viscous (sometimes solid) resins the homopolymers of which have character­istic properties that are used to generate the final properties of an adhesive system. The adhesive developer is able to identify a wide variety of monomer and prepolymer types which allow the final properties of the adhesive to be tailored for desired applications.

With regard to their chemistry, methacrylates differ from acrylates only by the presence of an extra methyl group (Figure 5.23).

The physical properties of the methacrylate homopolymers differ considerably from those of acrylate polymers (see Table 5.3). The main difference between one — part and two-part acrylate/methacrylate adhesives and UV-setting adhesives on the one hand and anaerobic adhesives on the other hand is the functionality of the monomers. While anaerobic adhesives are mostly based on bifunctional, trifunc­tional or tetrafunctional systems, the one-part, two-part and UV-setting adhesives are mostly based on monofunctional compounds. Owing to their high function­ality, anaerobic systems react to yield highly crosslinked, brittle polymers with high dimensional stability, whereas the properties of the polymers of the one-part, two-part and UV-setting systems range from extremely strong and impact-resis­tant to highly flexible. These systems therefore belong to the class of structural adhesives.

Table 5.3 Comparison of the properties of acrylate polymers and similar methacrylate polymers.

Acrylate polymer Methacrylate polymer

Velocity of reaction High

Glass transition temperature Often lower

Strength High

Chemical resistance Good

Flexibility Good

Prize of the monomers High