Polyvinyl formal plastic

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 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. 

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. 

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. ... 

Vinyl resins (1934) n. According to common chemical nomenclature, all resins and polymers made from monomers containing the vinyl group, H2C=CHX. In the chemical literature, polystyrene, polyolefins, polymethyl methacrylate and many other styrenic, ethenic, and acrylic co-polymers are classified as vinyls. In the plastics literature, the above materials are given their own classifications and the term vinyl is restricted to compounds in which X, above, is not H, a hydrocarbon radical, nor an acrylic-type ester. In daily use, the term vinyl plastics refers primarily to polyvinyl chloride and its co-polymers, and secondarily to the following polyvinyl acetal, polyvinyl acetate, poly-vinyl alcohol, polyvinyl but-yral, poly(n-vinylcar-bazole), polyvinyl dichloride, polyvinyl formal, polyvinylidene chloride, polyisobutylvinyl ether, and poly (1-vinylpyrrolidone). Mishra MKM, Yagd Y (1998) Handbook of vinyl polymerization. Marcel Dekker, New York. 

Plastic, carbon and metal films (Section 4.7) are used as specimen supports on TEM grids. There are two plastic support materials in use collodion, 0.5% solution of nitrocellulose in amyl acetate and formvar, 0.25% polyvinyl formal in ethylene dichloride. These polymers are available as powders, solutions or prepared films on TEM grids. Formvar films, especially holey ones, are used as substrates for the formation of holey carbon films. Today, collodion is not used too often, as it is not as stable in the electron beam as formvar or carbon films. 

The joint shown in Fig. 103(b) failed in the neighbourhood of 70MN.m (data from Foulkes et al., 1970) whilst the yield stress in uniaxial tension of polyvinyl formal at room temperature is given by Whitney and Andrews (1967) as 78MN.m". The uncertainty in the stress failure of torsional test pieces arises from differences in calculation of stress from failure torque. Either plastic or elastic failure must be assumed to make the calculation and which is assumed can only be decided from an examination of the appearance of the failed test piece. 

Those ubiquitous plastics polythene (polyethylene), polystyrene, and PVC (polyvinyl chloride) are made in this way. In the case of polythene the molecule M, which in this context is called a monomer, is ethylene, H2C=CH2. The outcome of the polymerization is a long chain, a polymer, of hundreds of-CH CH - units. Chemists have found that by starting with different versions of ethylene, such as H C=CHX, where X can be a group of atoms, they can form polymers with a wide range of properties. Thus, when X is a benzene ring, the polymer is polystyrene and when X is a chlorine atom the polymer is PVC. To obtain the non-stick Teflon all the hydrogen atoms are replaced by fluorine atoms that is why its more formal name is polytetrafluoroethylene (PTFE). 

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