Alkali-resistant resins

Terrazzo seal n. A composition of alkali-resistant resins or waves in solvent of water. 

Systems based on isophthalic acid often show better water and alkali resistance than those based on phthalic anhydride. This is not thought to be due to inherent differences between the phthalic and isophthalic structures but is ascribed to the fact that isophthalate resins have generally considerably higher viscosities which enable them to be diluted with greater amounts of styrene. It is the additional proportion of styrene which gives the improved water and alkali resistance. 

Whilst the properties of the cross-linked resins depend very greatly on the curing system used and on the type of resin, the most characteristic properties of commercial materials are their toughness, low shrinkage on cure, high adhesion to many substrates, good alkali resistance and versatility in formulation. 

The principal applications for furan resins are in chemical plant. Specific uses include the lining of tanks and vats and piping and for alkali-resistant tile cements. The property of moisture resistance is used when paper honeycomb structures are treated with furan resins and subsequently retain a good compression strength even after exposure to damp conditions. 

Oil-base (including oil-modified alkyd resin) paint films should not be used in alkaline environments as the paint will deteriorate owing to saponification alkali-resistant coatings are provided by some cellulose ethers, e.g. ethyl cellulose, certain polyurethane, chlorinated rubber, epoxy, p.v.c./ p.v.a. copolymer, or acrylic-resin-based paints. In particular, aluminium and its alloys should be protected by alkali-resistant coatings owing to the detrimental effects of alkali on these metals. 

Phenol-formaldehyde (phenolic) plastics The chemical resistance is affected by the phenol used, cresols giving the best acid resistance whilst xylenols are often used to obtain the best alkali resistance. For chemical-resistant applications the fillers used in moulding powder and reinforcing material in laminates should be inorganic, e.g. asbestos or glass. The resins are usually dark in colour. 

Uses Secondary plasticizer for polyvinyl chloride in polyester resins to increase strength of fiberglass varnish formulations to improve water and alkali resistance as an insulator fluid for electric condensers and as an additive in very high pressure lubricants. In fluorescent and high-intensity discharge ballasts manufactured prior to 1979 (U.S. EPA, 1998). 

To improve the weatherabihty of epoxies, which normally chalk and yellow, epoxy—polyester alloys or hybrids are used. These powders with improved overbake resistance cure at temperatures as low as 130°C. They have film flexibility similar to epoxy resins, but their hardness is slightly decreased. Corrosion resistance is equivalent to epoxy powders in most cases, although solvent and alkali resistance is inferior. 

Drastic alkali resistance tests consisting of heating wood specimens in boiling 10% NaOH for 16 days reduced the crushing strength at the elastic limit for untreated southern yellow pine from 620 to 80 psi and for the wood containing 71% furfuryl alcohol resin from 2650 to 890 psi (56). 

Copolymers of furfural with phenol or phenol-formaldehyde polymers have been available commercially for many years. Since the acid-catalyzed reaction of furfural and phenol has been difficult to control, most industrial applications involve the use of alkaline catalysts. Furfural-phenol resins are used for their alkali resistance, enhanced thermal stability, and good electrical properties compared to phenol-formaldehyde resins. 

Use Production of polyurethane foams and elastomers, in phenol-formaldehyde resins to improve water and alkali resistance bonding rubber to rayon or nylon. 

Uformite [Rohm Haas]. TM for synthetic resins based on urea-formaldehyde, melamine-formaldehyde, and triazine condensates. Supplied as colorless or light-colored aqueous solutions or solutions in volatile solvents. Solvent type produces hard, alkali-resistant, colorless coatings on curing with adhesion to a variety of surfaces. 

The coreaction of phenolic resins with alkyds is an "old timer" in which the excellent gloss retention and durability of alkyds are combined with the water and alkali resistance of phenolics. Alkyd resin can be designed to have compatibility with hydroxyl-modified vinyl chloride-vinyl acetate copolymer resins, and this combination of fast drying, adhesion, excellent water resistance, and durability is specified in a number of coatings for military and marine use. 

The first synthetic thermosets used as adhesives were phenol-formaldehyde resins produced at the end of the nineteenth eentury, historically linked to Baekeland s process which attained industrial status at the beginning of the twentieth century [4], Furanic condensates appeared mueh later as a result of the marketing of 2. They were first used as foundry binders by Quaker Oats in 1960. The use of furanic resins in the aerospace industry began ten years later. Although furanic resins represent a mere 1 % of the total thermoset produetion, the high added-value of these materials amply justifies their use. In fact, furan-based adhesives and binders are fire-, solvent-, and acid- or alkali-resistant. They are known, however, to display two main drawbacks related to their sensitivity to shrinkage and oxidation. 

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