Exterior durability

Exterior durability. Corrosion control. Mechanical properties. Architectural coatings. Product coatings. 

Color Properties Required. Colorants must be chosen to permit formulation of a coating that can meet performance requirements such as exterior durability and resistance to solvents, chemicals, and heat. Health and safety regulations may also affect colorant choice. 

The two amino resins in common use are urea formaldehyde and melamine formaldehyde, and most stoving finishes contain one or the other. They have many properties in common urea formaldehyde, however, while substantially cheaper, has poor exterior durability, whereas melamine formaldehyde imparts excellent exterior durability. As they are both water white they give white finishes of excellent colour, with the additional advantage of retaining their colour on over-stoving. Urea formaldehyde is commonly used in conjunction with a lesser quantity of an alkyd to give finishes with excellent resistance to water and mild chemicals, which are therefore well suited to use on domestic equipment, e.g. washing machines. 

There are some similarities between coil finishing and original motor car finishes both are required to give good exterior durability and both can be... 

Topcoats over primer are often applied by airless spray. Trends to higher standards of exterior durability have encouraged the use of methacrylated alkyds and two-component urethane finishes. 

This is the last of the end usages in this section for which exterior durability is required from the painting system. The substrate here is mainly aluminium... 

There are important modifications of alkyds that help in specific applications. Phenolics can be added to improve film hardness and water resistance, but these confer increased yellowing tendencies on the final coating. Silicones impart heat resistance and exterior durability. Styrene increases the drying speed. Methyl methacrylate when added gives faster drying properties and improves the color and durability of the coating. 

Poiymers which are 100% acrylic are known for their outstanding exterior durability properties, as well as excellent alkali resistance and overall high performance. Styrene is generally lower-cost than many other monomers, so styrene-acrylics are lower in cost than all acrylics but have poorer exterior durability because styrene is a UV absorber and degrades. Styrene-acrylics, do, however, generally have very good water-resistance properties due to their hydrophobicity. Styrene acrylics are popular in some areas of Europe, Asia, and Latin America. Vinyl acetate is also somewhat lower in cost, so these polymers are popular for interior paints, particularly in the United States, where exterior durability and alkali resistance are not performance issues. 

The exterior durability of softwood veneer species in this country has been demonstrated. There have been some difficulties encountered in the long term exterior durability of some Asian veneer species when bonded with phenolic resins. Extractives interfering with the cure of the resin directly or the resin bonded to the extractives rather than the wood cause failures along the glue line. These species shrink and swell more than native softwoods. Stresses are greater and breaks in the wood hydrogen... 

None of these adhesives would be suitable for glue-lamina-ting using present procedures. Room temperature curing glues, with good exterior durability, are now almost exclusively used. Resorcinolic adhesives are the only type which meet the indus-... 

The lithol reds are bright reds with high tint strengths and moderate dispersion characteristics the barium salt is yellower in shade than the calcium salt, which may best be described as a medium red. The use of these pigments in the plastics industry is as a result of their low cost and ready availability. Neither pigment can be recommended for any polymer likely to experience outdoor exposure since the exterior durability of both calcium and barium lithol red is inadequate for such situations. Easy dispersing grades are available that find acceptance in the rubber industry. 

The moderate lightfastness and poor exterior durability in conjunction with a moderate, short dwell time and heat stability of 500°F (240°C) are the major factors restricting the more widespread use of this pigment. 

The incorporation of animal or vegetable protein constituents into phenolic resins to form exterior durable adhesives of fast-curing or special properties. 

Soybean-based, quick-clamping cold-press glues of exterior durability and mold resistance. 

Phenol-formaldehyde type polymers had been the only exterior-durable adhesives for wood bonding, until the recent limited use of isocyanates. Both systems are petrochemical-based. Several researchers substituted carbohydrates for part of phenolic adhesives (1-4) > producing solid, fusible novolak resins. Recently, reaction of carbohydrate acid-degradation products with phenol and formaldehyde has produced liquid resols (5). Gibbons and Wondolowski (6,7) replaced a considerable amount of phenol with carbohydrate and urea to pro-... 

Nondrying, short oil alkyds are generally based on castor or coconut oils. They are used with nitrocellulose for exterior lacquers. Coconut oil alkyds give the best exterior durability castor oil lacquers have the best film properties. 

Polyester resins possess premium performance properties such as exterior durability, gloss, flexibility hardness, color stability, and versatility of cure. Polyesters are used in product finishes for household appliances, food and beverage containers, aircraft and equipment, automotive primers and bake coats, metal furniture, and fixtures. For example, water-soluble saturated polyesters are used in industrial baking paints, and in combination with melamine resin. Polyesters can be formulated in high solids and waterborne formulations to meet the requirements for the low VOC coatings being mandated by the EPA. 

Alkyd paints are the most foolproof t5rpe of coatings and are often preferred for use because of their lower cost and relatively easy-to-make pigment dispersions that do not flocculate. The major limitation of alkyds is their hmited exterior durability as compared to latex coatings. 

Binders for thermosetting powder coatings are often called a hardener. The hardeners are a mixture of a primary resin and a cross-linker. The major types of binders can be limited to polyester, epoxy, hybrid epoxypolyester, acrylic, and UV cure types. Polyester binders are used for good exterior durability, retention of gloss, and resistance to chalking. 

Gloss retention Color retention Exterior durability... 

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