Polyvinyl formal-phenolic resins

These are used in bonding metal or reinforced plastic facings to paper (resin impregnated) honeycomb structures, cork and rubber compositions, cyclized and unvulcanized rubbers, steel to vulcanized rubber, and electrical applications. They are also used as primer for metals to be bonded to wood with phenolics. Polyvinyl butyral-phenolics lack the shear strength and toughness of the polyvinyl formal-phenolic type. ... 

This includes wire enamels on a base of polyvinyl formal, polyurethane or epoxy resins as well as moulding powder plastics on phenol-formaldehyde and similar binders, with cellulose fillers, laminated plastics on paper and cotton cloth base, triacetate cellulose films, films and fibres of polyethylene terephthalate. 

Heat-setting resins cannot be plasticized by low molecular weight plasticizers. Polyvinyl acetals have been claimed for these products. American Cyanamid Co. has suggested polyvinyl acetals or butyrals in an amount of 10 to 25% of the resin for urea and melamine resins. For varnishes and adhesives, combinations of phenolic resins and polyvinyl formal are recommended. Polyvinyl acetals with higher alkyl radicals are suitable for cellulose esters and improve elasticity as well as resistance against water. 

The main use for phenolic resins is in oleoresinous varnishes. Apart from the chemical-resistant finishes produced with epoxy resins (Chapter 14), other outlets include modification of alkyds to improve resistance to water and alkali, combination with U/F resins (Chapter 13) to provide metal coatings and combination with polyvinyl formal or butyral resins to produce wire enamels. 

Uses Phenolic/polyvinyl formal resins (wire enamels, can coatings) mfg. of paints, adhesives, and films In food-pkg. adhesives In food-contact coatings In paper/paperboard in contact with aq./fatty foods Regulatory FDA 21CFR 175.105, 175.300, 176.170... 

N-(n-Butyl)-3-aminopropyltrimethoxysilane phenolic/polyvinyl formal resins, can coatings Polyvinyl formal... 

In the waterborne phenolic adhesives, a new dispersion system (98) has been reported. This system uses the solubility of some thermoplastics in phenol, and the subsequent polymerization takes place upon the addition of formaldehyde, an emulsifier, and water. The dispersion is then formed in situ. The versatility of this process is indicated by the use of many polymers with a wide range of properties, e.g., polyvinyl formal, polyvinyl butyral, acrylonitrile-butadiene copolymer, bisphenol-A resins, polyvinyl acetate, polycarbonate, polymethyl methacrylate, and nylons. 

In most widely used two-polymer adhesives, the thermosetting component is phenolic. Phenolic resins are generally compatible, although not easily miscible, with a number of thermoplastic polymers. Particularly good compatibility is demonstrated between conventional alcohol-soluble phenolic resins and polyvinyl esters and acetals. Epoxies are important in two polymer adhesive systems. The most important thermoplastic components are the polyvinyl acetals (polyvinyl formal and butyral) and synthetic rubber, particularly nitrile rubber. Soluble nylons are also an important class. ... 

Polyvinyl Alcohol and Acetals. Polyvinyl alcohol fibers are solution-spun, and then cross-linked with formaldehyde (Fig. 3.72) to make them resistant to water. Polyvinyl formal is cross-linked with phenolic resole to make baked coatings on electrical wire. Polyvinyl butyral is cross-linked with phenolic resin to make extremely tough bullet-proof helmets. 

Polyvinyl formal and butyral contain -OH groups that are cured by dialdehydes, diisocyanates, anhydrides, epoxy, melamine, and phenolic resins. 

The largest commercial use for polyvinyl formal is as wire enamel, usually in conjunction with cresylic phenolic resin. Similar resins are used also with phenolics as structural adhesives. They are very resistant to greases and oils. Some grades have been used as can coatings and wash primers. Although they can be molded, extruded, or cast, these grades have achieved little commercial significance. 

Figure 1 Polymer interpretation chart. PAI, polyamideimide PC, polycarbonate UP, unsaturated polyester PDAP, diarylate phtalate resin VC-VAc, vinyl chloride-vinyl acetate copolymer PVAc, polyvinyl acetate PVFM, polyvinyl formal PUR, polyurethane PA, polyamide PMA, methacrylate ester polymer EVA, ethylene-vinyl acetate copolymer PF, phenol resin EP, epoxide resin PS, polystyrene ABS, acrylonitrile-butadiene-styrene copolymer PPO, polyphenylene oxide P-SULFONE, poly-sulfone PA, polyamide UF, urea resin CN, nitrocellulose PVA, polyvinyl acetate MC, methyl cellulose MF, melamine resin PAN, polyacrylonitrile PVC, polyvinyl chloride PVF, polyvinyl fluoride CR, polychloroprene CHR, polyepichlorohydrin SI, polymethylsiloxane POM, polyoxy-methylene PTFE, polytetrafluoroethylene MOD-PP, modified PP EPT, ethylene-propylene terpolymer EPR, ethylene-propylene rubber PI, polyisoprene BR, butyl rubber PMP, poly(4-methyl pentene-1) PE, poly(ethylene) PB, poly(butene-l). (Adapted from Ref. 22, p. 50.)...

Vinyl-phenolic. Vinyl-phenolic adhesives are based on a combination of phenolic resin with polyvinyl formal or polyvinyl butyral resins. They have excellent shear and peel strength. Room-temperature shear strength as high as 5,000 Ib/in is available. Maximum operating temperature, however, is only 200°F, because the thermoplastic constituent softens at elevated temperatures. Chemical resistance and impact strength are excellent. 

Figure 14 Chemical structure of a typical phenolic resole and of polyvinyl formal resin.

Historically, the first structural adhesive successfully used was used in the aircraft industry for bonding aluminium to wood (Garnish, 1977). It was a polyvinyl formal composition with a phenol formaldehyde resin. 

Adhesives which incorporate phenol-formaldehyde resins are much used as structural adhesives for metals. They comprise the original polyvinyl formal/PF, and polyvinyl butyral/PF together with nitrile phenolics and epoxy phenolics. The ratio of non-phenolic polymer to the PF resin in the structural adhesives determines the morphology of the material, whether it is two-phased, and which phase is continuous and which discrete. This, in turn, influences the flexibility of the... 

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