Polyester finishes unsaturated

Unsaturated polyester finishes of this type do not need to be stoved to effect crosslinking, but will cure at room temperature once a suitable peroxide initiator cobalt salt activator are added. The system then has a finite pot life and needs to be applied soon after mixing. Such a system is an example of a two-pack system. That is the finish is supplied in two packages to be mixed shortly before use, with obvious limitations. However, polymerisation can also be induced by ultra violet radiation or electron beam exposure when polymerisation occurs almost instantaneously. These techniques are used widely in packaging, particularly cans, for which many other unsaturated polymers, such as unsaturated acrylic resins have been devised. 

Fig. 16.1 The cross-linking of an unsaturated polyester finish. The broken rods symbolize portions of the polyester chains and the dashes represent styrene molecules.

Unsaturated polyester resin powders can provide a colored and finished exterior molded surface or a finish ready for painting. Normally, a primer/sealer must be appHed to molded articles prior to painting. In addition to the unsaturated polyester resin, multifimctional unsaturated monomers such as triaHyl cyanurate (TAC) [101-37-1] or diaHyl phthalate (DAP) [131-17-9] suitable peroxide initiators (qv) or mixtures thereof, and mold release agents (qv) are used to formulate the coating powder (46). 

Coating materials may be based on short or medium-oil alkyds (e.g. primers for door and window frames) nitrocellulose or thermoplastic acrylics (e.g. lacquers for paper or furniture finishes) amino resin-alkyd coatings, with or without nitrocellulose inclusions, but with a strong acid catalyst to promote low temperature cure (furniture finishes) two-pack polyurethanes (furniture, flat boards) unsaturated polyester resins in styrene with free-radical cure initiated by peroxides (furniture) or unsaturated acrylic oligomers and monomers cured by u.v. radiation or electron beams (coatings for record sleeves paperback covers, knock-down furniture or flush interior doors). 

Unsaturated polyester and methacrylate resins are frequently colored with pigment-plasticizer (DIDP) pastes. They have no measurable adverse effect on the important mechanical properties of the finished article. To a small extent pigments are also dispersed directly in one part of the monomer. 

Gel-coat resins are a particular class of unsaturated polyester resins. Gel coats provide finish appearance to the unsaturated polyester parts and may also provide... 

The most successful application of the RIM-process is in the production of polyurethane-based materials. Other systems, such as composites based on polycaproamide, epoxy resins, and unsaturated polyesters can also be processed by reactive injection molding. New reactive systems have also been specially created for the RIM-process260 because of the exceptional opportunities it offers for manufacture of finished articles from engineering plastics with a high modulus of elasticity and impact strength. The automotive industry, which is the main customer for RIM-articles, can utilize this technology to manufacture of massive parts such as body panels, covers, wings, bumpers and other made of newly developed plastics. 

Ludopal . [BASF AG] Unsaturated polyester resins for finishes, filling compds., elastifying other grades. 

The industrial production of an unsaturated polyester resin is controlled by several factors, whose levels confer on it certain properties that are important to other industries that use the resin as raw material for making finished products. In the curing stage, a catalyst is added to accelerate gel formation by the resin. The time when the gel starts to form, after the catalyst is added, is an important characteristic known as gel time. 

A more convenient method is not to decrease the elastic modulus of the whole adhesive but to form an elastic finish coat [182] not less than 30 pm thick [183] on the adhesive—substrate interface. With lower elastic modulus, the mobility of structural elements decreases. Application of an elastic sublayer decreased the internal stresses during the formation of coatings made of unsaturated polyester resins [185], epoxides [186], and polymer solutions [187]. The use of elastic finish coats found comparatively wide application for paint coatings but seems less promising for adhesive-bonded joints because of decrease of the adhesion strength due to the low cohesion strength of the finish coat itself and because of the labor requirements in producing the adhesive-bonded joints. 

Unsaturated polyester Wood finish Styrene acts as a solvent prior to taking part in the cross-linking reaction... 

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