Alkyds coatings

Alkoxysilanes Alkyd coatings Alkyd paints Alkyd resins... 

PhenoHcs that are not heat-reactive may be incorporated into both air-dried and baked oleoresinous coatings. AppHcations vary widely and include clear and pigmented exterior varnishes, aluminum-maintenance paints, 2inc-rich primers, can coatings, insulation varnishes, and concrete paints. As modifiers in a great variety of appHcations, they enhance the performance of oleoresinous and alkyd coatings. 

TrimeUitic anhydride is converted to PVC plasticizers, polyesters, water-soluble alkyd coatings, and polyamide—imide resias. The trimellitate plasticizers have a lower volatility than those derived from phthaUc anhydride (see Plasticizers). 

Chlorendic anhydride is the common name of the Diels-Alder adduct of maleic anhydride and hexachlorocyclopentadiene, 3,4,5,6,7,7-hexachloroendomethylene-l,2,3,6-tetrahydrophthahc anhydride (HET). The resultant resins from HET contribute to the flame retardancy of the alkyd coatings. HET gives a greater reaction rate than phthaUc anhydride, to the extent that at 204—210°C the reaction rate approximates that of phthaUc anhydride at a temperature of 238°C (8). However, the resins tend to develop darker color, particularly at high processing temperature. Tetrachlorophthahc anhydride [117-08-8] made by conventional chlorination of phthaUc anhydride, would also impart flame retardancy to its alkyds. However, it is appreciably less soluble in the usual processing solvents than is phthaUc anhydride, and is reported to be of appreciably lower chemical reactivity (8). 

Another approach to high soHds alkyd coatings is the partial replacement of solvent in a conventional long-oil alkyd with a reactive diluent. Eor example, dicyclopentenyloxyethyl methacrylate [70191-60-9J, mixed amides from the condensation of acrylamide (qv) (2-propeneamide)... 

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). 

Fig.12. Comparison between a conventional high solid alkyd coating ( ) and an alkyd based on a hyperbranched aliphatic polyester ( ). Drying time as a function of molar mass [123]...

Pettersson and Sorensen have described a number of different thermoset resin structures based on hyperbranched aliphatic polyesters [123]. Their results can best be exemplified by a study on hyperbranched alkyd coating resins. A comparative study was performed between an alkyd resin based on a hyperbranched aliphatic polyester and a conventional high solid alkyd, which is a less branched structure. The hyperbranched resin had a substantially lower viscosity than the conventional resin of comparable molecular weight, that is, less solvent was needed to obtain a suitable application viscosity. The hyperbranched resin also exhibited much shorter drying times than the conventional resin, although the oil content was similar. These achievements would not have been possible without a change in architecture of the backbone structure of the resins (Figs. 12,13). 

The interfacial chemistry of corrosion-induced failure on galvanized steel has been investigated (2) adhesion of a polyurethane coating was not found to involve chemical transformations detectable by XPS, but exposure to Kesternich aging caused zinc diffusion into the coating. Similar results were obtained with an alkyd coating. Adhesion loss was proposed to be due to formation of a weak boundary layer of zinc soaps or water-soluble zinc corrosion products at the paint metal Interface. 

At least one study has compared vemonia oil to partially epoxidized soybean and linseed oils, to investigate claims that vemonia oil is advantaged due to inherently lower viscosity. Authors conclude that partially epoxidized soybean and linseed oils have viscosity and reactivity that are similar to vemonia oil in formulated coating systems, and provide improvements to viscosity, content of volatile organic compounds (VOCs), and curing time in alkyd coatings when compared to conventional formulations and formulations containing fully epoxidized soybean oil [116]. 

Fire-retardant coatings currently in use contain a number of ingredients that are either considered to be toxic heavy metals or on the hazardous air pollutants (HAPs) list. In addition, there is concern that the use of halogenated chemicals in these coatings and other products will be banned in the future. A recent paper contains the details of two reformulations programs. The first is a reformulation of a low VOC chlorinated alkyd coating and the second is a reformulation of a chlorinated emulsion system. Both programs successfully reduced the heavy metals and lowered the HAPs to an acceptable level (Dahm, 1996). 

Flame retardancy -alkyd coatings [ALKYD RESINS] (Vol 2)... 

Keyvrords Zircoaluminates adhesives polyester coating alkyd coating rubber high shear mixer. 

Alkyd coatings. A medium oil conventional solids alkyd (52.5% solids by weight, Reichhold Beckosol 11-070) was prepared and spray-applied as already described to both CRS and phosphatized steel (Table 6). 

Solvents are selected such that some will escape relatively quickly from paint films to prevent excessive flow, while others will escape slowly to provide film leveling and adhesion. With typical alkyd coatings, the first 30% of solvent has been observed to evaporate as quickly as the neat solvents, essentially at a constant rate which is dependent on volatility. Later stage evaporation occurred several times more slowly and was rate-controlled by solvent diffusion to the surface of the paint film. The transition point between this behavior was defined as the resin solids content at which the evaporation rate due to volatility equaled that due to diffusion. Transition points have been observed to typically occur at a resin solids content of 40-50% v/v. Thus alkyd paints, normally formulated at 27-40% v/v resin solids, generally exhibit rapid initial solvent-release driven by volatility while high solids coatings (usually 65-75% v/v resin solids) dry solely by a diffusion-controlled process with negligible influence by solvent volatility (Ellis, 1983). 

Noise resistance monitoring has been used to track the long-term degradation of marine coatings under laboratory exposures (153), and remotely under natural exposure conditions (154). In studies of epoxy and alkyd coatings on steel... 

The largest use for styrene (over 70%) is to make homopolymer polystyrene. The U.S. production volume reached 6.3 billion lb in 1998. Other major uses are in plastics, latex, paints, and coatings, synthetic rubbers, polyesters, and styrene-alkyd coatings. In these applications styrene is used in copolymers... 

Owing to wide variations in composition, alkyd coatings vary widely in performance during application, service and also in cost. Selection of alkyd coatings thus depends upon ... 

Chemical, 1958 Patton, 1962 Payne, 1965). The properties of alkyd coatings are given in Table 8.1. 

Alkyd coatings are widely used for wood and steel substrates (Figure 8.1). Pure alkyd coatings when applied on concrete and masonry have the danger of oil saponification. However, modified alkyds can be used on concrete substrates without too much risk. 

Figure 8.1 Portacabins painted with alkyd coating...

Alkyd coatings are not recommended for immersion service or for use in areas which are routinely subject to accidental immersion. 

One major use of polyesters, the alkyd coating resins, is based on random prepolymers reacted with unsaturated fatty acids. Gelation phenomena have been studied extensively and the gelation theories of Carothers, Flory, and Stock-mayer were developed with polyester random prepolymers. Only recently, Gordon (iJ, 12) has extended the gelation theory to the structopendant polyester system cross-linked by vinyl monomers. 

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