Phenoplasts, Phenolic resins

Phenolic resins are also widely known as phenol-formaldehyde resins, PF resins and phenoplasts. The trade name Bakelite has in the past been widely and erroneously used as a common noun and indeed is noted as such in many English dictionaries. 

Carswell. T.S., Phenoplasts their structure, properties, and chemical technology. In Mark. H. and Melville, H.W. (Eds.), High Polymers. Interscience, New York, 1947, Chapter 1. Knop, A. and Pilato, L.A., Phenolic Resins. Springer-Verlag, Berlin, 1985, p. 3. 

In far too many instances trade-name polymer nomenclature conveys very little meaning regarding the structure of a polymer. Many condensation polymers, in fact, seem not to have names. Thus the polymer obtained by the step polymerization of formaldehyde and phenol is variously referred to a phenol-formaldehyde polymer, phenol-formaldehyde resin, phenolic, phenolic resin, and phenoplast. Polymers of formaldehyde or other aldehydes with urea or melamine are generally referred to as amino resins or aminoplasts without any more specific names. It is often extremely difficult to determine which aldehyde and which amino monomers have been used to synthesize a particular polymer being referred to as an amino resin. More specific nomenclature, if it can be called that, is afforded by indicating the two reactants as in names such as urea-formaldehyde resin or melamine-formaldehyde resin. 

The principal feature that distinguishes thermosets and conventional elastomers from thermoplastics is the presence of a cross-linked network structure. As we have seen from the above discussion, in the case of elastomers the network structure may be formed by a limited number of covalent bonds (cross-linked rubbers) or may be due to physical links resulting in a domain structure (thermoplastic elastomers). For elastomers, the presence of these cross-links prevents gross mobility of molecules, but local molecular mobility is still possible. Thermosets, on the other hand, have a network structure formed exclusively by covalent bonds. Thermosets have a high density of cross-links and are consequently infusible, insoluble, thermally stable, and dimensionally stable under load. The major commercial thermosets include epoxies, polyesters, and polymers based on formaldehyde. Formaldehyde-based resins, which are the most widely used thermosets, consist essentially of two classes of thermosets. These are the condensation products of formaldehyde with phenol (or resorcinol) (phenoplasts or phenolic resins) or with urea or melamine (aminoplastics or amino resins). 

Nitrile butadiene rubber (NBR), which is formaldehyde-resistant, is the predominantly used elastifying component for phenoplastics. The resin and rubber interreact during the curing process. Natural rubber is incompatible with phenolic resins. At a rubber content of 25 %, the modulus of elasticity, at 1,000 N mm , has already fallen into the middle range of unreinforced thermoplastics. The impact strength reaches the values of type 74 (fabric chips, reinforced). Their form stability when exposed to heat is below that of type 31 at temperatures below 100 °C. 

Phenolic resins are among the oldest and best-known general purpose molding materials. They were among the very first commercial polymers to be introduced at the turn of the twentieth century under the tradename Bakelite. These polymers are also known as phenoplasts. 

Phenol resins are generally identified by liberating phenol om ttie thermosetting sample by heat or hydrolysis and then applying rapid tests for it 24,9i) J ov, ever, detailed information about the presumed type of phenoplast can be obtained only by its thermal breakdown into the structural units and their separation and identification by or This led to the discovery fliat the pyrolysis... 

Historically, phenol-formaldehyde resins (phenolic resins, phenoplasts) are the oldest synthetic thermoset materials as early as in 1910 the first ones ( bakelite to their inventor Baekeland) were introduced. Who does not remember the black telephones and light switches that were popular in the 1930s and 1940s Phenolic resins are based on hydroxy-aromatic compounds (phenol and phenol derivatives) and aldehydes [2]. Furfural is occasionally used as aldehyde but by far the most widely used aldehyde is formaldehyde. Formaldehyde can be administered as an aqueous solution (formalin), polymeric solid (paraformaldehyde) or solid adduct with ammonia (hexamethylenetetramine, HMTA). The resins are formed by a step-growth mechanism in aqueous solution. 

Formaldehyde is employed in the production of aminoplasts and phenoplasts, which are two different but related classes of thermoset polymers. Aminoplasts are products of the condensation reaction between either urea (urea-formaldehyde or UF resins) or melamine (melamine-formaldeliyde or MF resins) with formaldehyde. Phenoplasts or phenolic (phenol-formaldehyde or PF) resins are prepared from the condensation products of phenol or resorcinol and formaldehyde. 

The most important resin types used in production of curable molding compounds are phenolic, urea, melamine, unsaturated polyester, epoxide and diallyl phthalate resins. Curable molding compounds built up with these bonding agents are described in DIN 7708" (Phenoplasts and Aminoplasts), DIN 16911 and 169132 (Polyester Molding Compounds and Polyester Resin Mats), and DIN 16912 (Epoxy resin Molding Compounds). There is as yet no standard for diallyl phthalate masses, for the test method see ISO 1385 - 1.02.1977. 

Phenoplast n. Another name for phenol-formaldehyde resin. 

Amino and phenoplast resins (like melamine, urea, and phenolic) can also be used for elevated temperature curing. They are cross-linked through the hydroxyl group of the epoxy and produce products with good chemical resistance. 

Phenoplast n Another name for Phenol-Formaldehyde Resin. 

PF Phenol-formaldehyde resins Phenoplasts Polycondensate, i.e., crosslinking by elimination of H2O... 

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