Resin coating systems, thermoset acrylic

Uses Crosslinking agent in melamine resin coating systems, general industrial finishes, coil-coating enamels, appliance finishes, useful with alkyd, polyester, thermosetting acrylic, epoxy, and cellulose resins Properties Gardner 2 max. clear, vise, liq. limited water-sol. dens. 10.0 Ib/gal vise. (G-H) X-Z2 flash pt. > 180 F 98% NV Cymel 350 [Cytecind.j... 

Conventional industrial coatings materials of the thermoset type are usually acrylic, polyester, epoxy, polyurethane or silicone resins dispersed or dissolved in organic or water/ether-alcohol coupling solvents. They are cured with gas convection or electric IR ovens. The raw materials for the polymers come from petroleum feedstocks which are processed or manufactured into a finished coating system. 

Continuing development in the field of acrylic polymers for surface coating applications during the SO s led to the commercialisation of heat curing, thermosetting acrylic (TSA) resins for use in high quality industrial coating systems for both interior and exterior applications. 

As a one coat finish for plastics, acrylic urethanes have one major limitation, the aggressive solvent content of the acrylic and the polyisocyanate resins themselves. This limits their use to coatings for thermosetting substrates and a small number of TPA substrates such as ABS, PA (polyamide), RIM polyurethane and PPO (jmlyphenylene oxide). Even then, the system should be evaluated to ensure that no degradation of the plastic s impact resistance has taken place. Consult the TPA chapter for discussion on plastic substrates. 

Water reducible acrylic resins are available to the coatings formulator as both thermoplastic, and thermosetting types. The thermoplastic acrylics film form by simple solvent evaporation and, therefore, cosolvent and amine selection are important. One of the cosolvents used must be a true solvent for the system and be less volatile. It must evaporate more slowly than water. This is to minimise the potential for blushing or flocculation that could be caused by having water as the last solvent to leave the film. The amine should also be volatile at ambient temperatures to minimise the retained water solubility, or sensitivity of the film after drying. This is particularly important since there is no curing reaction with thermoplastics. 

Whilst there are some thermoset acrylic emulsions cormnerdally available, the bulk of the thermoset resins, used as the main binder system, are produced in solution. Some may then be made waterborne by neutralisation and inversion (dispersion) into a water phase. Lower molecular weights favour this qrproach. The rate of conversion from solvent based to waterborne industrial thermoset coating systems has been, and is, much slower than the conversion from architectural alkyd paints to emulsion altonatives. There are two principle reasons for this. Firstly there are problems of application and substrate wetting of many waterborne systems. Secondly, the modifications frequently required to induce water dispersibility reduce one or more of the essential performance properties required from the cured film, compared to a solvent based system. Water resistance, with many films having an increased tendency for blushing is one example. However, for some applications, such as electrodeposition, only waterborne systems will work. 

A wide variety of other specialty monomers are also used to provide specialized performance properties for coating applications. For example, amine functional monomers can be used to improve adhesion to aged alkyd substrates. Specialized monomers can also be used to improve exterior durability, for example VEOVA (vinyl ester of vesatic acid) monomers can improve the hydrolysis resistance of vinyl acetate polymers, and n-butyl methacrylate can be used to enhance the durabiHty of BA-MMA acrylics. Polymer hydrophobicity can be fine tuned by varying the levels of hydrophobic and hydrophilic monomers in the composition and styrene or ethyl hexyl acrylate are used to increase film hydrophobicity and reduce water permeability in BA-MMA systems. Specialty monomers are also used to provide specific chemical functionality to polymer compositions. For example, hydroxyethyl methacrylate can be used to provide hydroxyl functionality to acrylic resins, allowing these polymers to be used in cross-linkable thermoset coatings which cure via melamine chemistry. While specialty monomers are used at relatively low levels in polymer compositions, they frequently provide the performance features needed for the successful application of emulsion polymers in many coating areas. 

Additives and comonomers in thermoset, moisture, UV, and catalytically curing resins or coatings (e.g., acrylic, epoxy, melamine, and unsaturated polyester systems)... 

Uses Fluorescent optical brightener for nonaq. systems, acrylics, epoxies, other solv.-based coatings, thermoset and thermoplastic resins, plastics, films, and molded goods fabric brightener or whitener for detergent systems for nylon, silk, wool, and acetates (for use with nonionic, anionic, or cationic surfactants)... 

Chem. Descrip. y-Methacryloxypropyltrimethoxysilane CAS 2530-85-0 EINECS/ELINCS 219-785-8 Uses Adhesion promoter for adhesives and coatings coupling agent for glass-reinforced and min.-filled thermosetting resins blend additive in resin systems (polyester, acrylic), and filled or reinforced thermoplastic polymers (polyolefins, polyurethanes)... 

Conversion. The cure of many oxidative thermosetting coatings is accelerated by heating. In other resin systems, such as thermosetting acrylics and alkyd melamines, the reactions do not occur below tern-... 

The most used thermosetting resins for powder coatings are EP (18%), acrylics (2%), unsaturated polyesters (28%), PU (7%), and hybrid systems (45%) and among thermoplastics, PA, polyolefins, PVC and poly vinyl fluoride are preferred [110, 111]. 

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