Phenoplast

Cross-linking with aminoplasts and phenoplasts constitutes an important class of hardeners for high molecular-weight epoxy resins that require elevated temperature cures (see Amino 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. 

Lignins from waste hquors are also used as extenders for phenoplasts and in adhesives for laminated paper and board, hnoleum pastes, animal feedstuff pellets, etc. 

Another POLIDCASYR extension ensures that structural features of the backbone can be distinguished from those occurring in side chains. The system furthermore augments structure codes for polymers using a controlled vocabulary of keywords, such as epoxy resin , aminoplast or phenoplast . 

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. 

Phenoplasts manufactured on tlie basis of thermoreactive phenolformalde-hyde resin, harden on heating up to 120-170°C and then become insoluble. They are usually reinforced witli asbestos fiber. 

IIIA poor 175 CTI < 400 Polycarbonate, phenoplast (with inorganic fillers)... 

IIIB very poor 100 CTI < 175 Phenoplast (with organic fillers, e.g. wood, textile fibres, cellulose)... 

Strength, fire resistance and apparent density of polyfuran foams depend on the composition of the mixture, amount and type of filler. By varying these parameters, foamed materials may be obtained with 7 = 20-100 kg/m or higher. The fire resistance of these materials is better than that of foamed phenoplastics and polyiso-cyanurate foams, and the mechanical strength is higher than that of carbamide foams. 

Chem. Anlagen Bischo (Reut) Foams Prepared from Phenoplast and Di- and/or polyisocyanates. BDR Pht. 2,542,900 (1977)... 

At present, most chemical construction grouting in the United States is done with silicates. This is not because other materials are not available. By way of contrast, phenoplasts, aminoplasts, chrome lignins, and acrylamides are all used in Europe. These products are well known to American grouting firms. However, in the United States, Terra Firma and Terranier (chrome lignin and phenoplast) fell by the wayside some years ago, primarily due to the toxic properties of the dichromate catalyst. Herculox and Cyanaloc (aminoplasts) had limited application to begin with because they require an... 

Phenoplasts always contain a phenol, a formaldehyde, and an alkaline base. All three components are health hazards and potential environmental pollutants. Resorcinol is a phenol, and although not as hazardous as some phenols, it is still toxic and caustic. Formaldehyde is considered a dangerous material and at low atmospheric concentrations can lead to chronic respiratory ailments. Sodium hydroxide is, of course, well known as a caustic material. 

Phenoplast gels, if proportioned properly, will not leave an unreacted excess of either of the major components. (Excess of either resorcinol or formaldehyde can free itself into groundwater or air and become a potential hazard.) Thus, only the catalyst could possibly leach out to cause environmental pollution. Gels from properly proportioned constituents are generally inert (i.e., nontoxic and noncaustic). 

Urea solutions have very low viseosities, similar to the acrylics and phenoplasts. The reaction with formaldehyde, in addition to requiring elevated temperatures, is rapid and difficult to control. However, there are intermediate stages in the reaction when the urea is still soluble in water. Such materials, called precondensates or prepolymers, are readily available from industry, since urea formaldehydes are used in large quantities as adhesives. Of course, prepolymers are more viscous than the initial urea solution, but products are made which permit the final grout to be used at viscosities in the 10 to 20 cP range. The trade-off in viscosity is made to obtain a product easy to handle, with good gel time control. 

Soils stabilized with urea-formaldehyde have strengths comparable to the phenoplasts and like those materials are less sensitive to testing strain rate than other chemical grouts. (For optimum mechanical properties and to keep free formaldehyde levels low, one molecule of urea should be provided with three molecules of formaldehyde.) Little data are available, but it is probable that aminoplasts break down comparatively quickly under cyclic wet iry and freeze thaw conditions. The creep endurance limit is probably a relatively high percentage of the UC. Except as noted above, the resins have good stability and are considered permanent. 

The grout solutions become less viscous as they mix with water. Additives may be used to prevent an immediate reaction. The resulting product, such as Chemical Grout 5610, has a low enough viscosity to penetrate sands. Typical properties are shown in Fig. 11.46. Strength of the diluted grout is low, comparable to those of the phenoplasts. 

Combining two available grouts so as to obtain simultaneously the optimum properties of each is an idea which occurs naturally when trying to select a material for a specific job. To do so, the materials must of course be chemically compatible, particularly in the pH criterion for reaction. Thus, phenoplasts and aminoplasts may be combined, and in fact these... 

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