Polyvinyl formal

JCinjlec, Polyvinyl Formal Resins, Technical Bulletin, Chisso America Corp., New York, 1994. 

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. 

The viscosity of most adhesives increases with time as they set by cross-linking, cooling from the melt or loss of solvent. The cross-linking of a phenolic-polyvinyl formal adhesive and of cold-setting epoxies was found by de Bruyne [41] to be represented adequately by an exponential relationship ... 

Polyvinyl acetate and derivatives Polyvinyl acetate is used largely for coating applications, but the derivative polyvinyl alcohol, will, providing there are some residual acetate groups, dissolve in water. Reaction products of polyvinyl alcohol with aldehydes such as polyvinyl formal and polyvinyl butyral are highly specialised materials. 

It is customary to stop the hydrolysis of PVAc before all the acetyl groups are removed. Thus the commercial product, with a degree of hydrolysis of about 88%, is readily soluble in water but is resistant to less polar solvents, such as benzoie and gasoline. PVA fibers (Kuralon) are strong and insoluble in water because of a surface treatment with formaldehyde which reacts with the surface hydroxyl groups to produce polyvinyl formal on the polymer surface. 

These products are produced by the reaction of partially hydrolyzed PVAc with aldehydes. The acetal rings on these random amorphous polymer chains restrict flexibility and increase the heat deflection temperature to a value higher than that of PVAc. The heat deflection temperature of polyvinyl formal is about 90 C and is dependent on the specific composition of this complex polymer. Because of the presence of residual hydroxyl groups, commercial polyvinyl formal has a water absorption of about 1%. Polyvinyl formal has a Tg of 10S . It has a solubility parameter of about 10 H and is soluble in solvents with similar solubility parameters, such as acetone. 

PVF PVP Q R Polyvinyl formal Polyvinyl fluoride Polyvinyl pyrrolidone Charge (electric) Heat flow Universal gas constant Stress relaxation modulus Weight change per day Resistance... 

The advanced applications for nitrocellulose plastisol propellants require that they be integrally bonded to the motor case. Successful case bonding for the multiyear storage life of a rocket calls for special adhesives and liners which are completely compatible with these highly plasticized propellants. Best results have been obtained with a combination of an impervious rubber liner and a crosslinked adhesive system with a limited affinity for the plasticizers used in the propellants. Examples of effective liners are silica-filled butyl rubber and chlorinated synthetic rubber. Epoxy polyamides, isocyanate-crosslinked cellulose esters, and combinations of crosslinked phenol-formaldehyde and polyvinyl formal varnishes have proved to be effective adhesives between propellant and impervious liners. Pressure curing of the propellants helps... 

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. 

Polyvinyl Formal, Grade 7/955(of Shawinigan Resins Corp) 24%, with 1% DPhA added. The 2nd type, designated as XM-157 for use in XM81 152mm Gun consisted of NC (12.3%N)65, Northern Kraft fiber(bleached) 15 Polyvinyl Formal(same as above) 19%, with 1% DPhA added... 

Epoxy resins may be blended with certain vinyl polymers to improve the impact strength and peel strength of the adhesive. Polyvinyl acetals, such as polyvinyl butyral and polyvinyl formal, and polyvinyl esters are compatible with DGEBA epoxy resins when added at concentrations of 10 to 20% by weight. The addition improves the resulting impact resistance and peel strength of the cured adhesive. However, temperature and chemical resistance are sacrificed by the addition of the low-glass-transition-temperature vinyl resins. 

Polyglycidyl ether of l,l,2,2-tetrakis-(4-hydroxyl phenyl) ethane Tetrahydrofuran Solid epoxy resin Polyvinyl formal resin Aluminum dust Diaminodiphenyl sulfone 80 55 20 10 100 24.5... 

In the second major use of VAM, PVA is converted to poly(vinyl alcohol) (PVOH) by a transesterification reaction with methanol, giving methyl acetate as coproduct. PVOH finds its major end use in textile sizing and adhesives. Further reaction of PVOH with butyraldehyde or formaldehyde gives polyvinyl butyral (PVB) or polyvinyl formal, which together constitute the third largest consumption of VAM. PVB is used almost exclusively in the adhesive laminating inner layer in safety glass. 

Since most materials are opaque to the electron beam, even when only a few hundred nanometers thick, special problems arise in the production of suitable mounted specimens. Specimen support films are usually made of plastic or carbon, though other materials have also been used. Suitable film solutions may be made up of 2% w/v formvar (polyvinyl formal) in ethylene dichloride or chloroform. 

Plastic films can be formed from a number of polymers two of the most common are collodion (nitrocellulose) and polyvinyl formal (Formvar). A number of other plastic materials can be used for thin films, some with specific advantages (101). Plastic films are usually prepared either by spreading a drop of solution of the plastic (in an appropriate solvent) onto a clean water surface, or by stripping off a film that has been coated onto a clean, flat surface (such as a glass slide) onto the surface of clean water. 

Formation of condensation structures is the reason for gelation of solutions of various natural and synthetic polymers. Gelation may be accompanied by conformational changes of macromolecules, which occur in the case of gelling of gelatin and other biopolymers, or in the course of chemical reactions. For instance, according to Vlodavets, partial acetalization of polyvinyl alcohol with formaldehyde in acidic medium under the conditions of supersaturation yields fibers of polyvinyl formals which further undergo coalescence and form a network with properties similar to those of leather (and artificial leather substitute). 

Polyvinyl acetate Polyvinyl alcohol Polyvinyl butyral Ethylene vinyl acetate Ethylene vinyl alcohol VCM-VAM copolymers Polyvinyl formal... 

Polyvinyl formal (PVF) is used to manufacture magnetic wire insulation as well as metal coatings and can linings. The quantities of PVF used are small and thus is a minor use for VAM. 

Polyvinyl butyral (PVB), 183, 261 Polyvinyl formal (PVF), 184 Polyvinylidene chloride, 168 Postreforming, 57, 58, 60 Potassium carbonate, 52, 140, 185, 186 Prereformer, 57, 58 Pressure build-up coil, 116 Pressure swing adsorption ... 

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