Phenol-formaldehyde casting resin

It is likely that the quinone methide and related structures formed at these temperatures account for the dark colour of phenolic compression mouldings. It is to be noted that cast phenol-formaldehyde resins, which are hardened at much... 

The importance of the nature of the catalyst on the hardening reaction must also be stressed. Strong acids will sufficiently catalyse a resol to cure thin films at room temperature, but as the pH rises there will be a reduction in activity which passes through a minimum at about pH 7. Under alkaline conditions the rate of reaction is related to the type of catalyst and to its concentration. The effect of pH value on the gelling time of a casting resin (phenol-formaldehyde ratio 1 2.25) is shown in Figure 23.15. 

Finally, metal- and resin-bonded composites are also classified as particulate composites. Metal-bonded composites included structural parts, electrical contact materials, metal-cutting tools, and magnet materials and are formed by incorporating metallic or ceramic particulates such as WC, TiC, W, or Mo in metal matrixes through traditional powder metallurgical or casting techniques. Resin-bonded composites are composed of particulate fillers such as silica flour, wood flour, mica, or glass spheres in phenol-formaldehyde (Bakelite), epoxy, polyester, or thermoplastic matrixes. 

Processing of phenol-aldehyde oligomers into various articles is based on a polycondensation reaction which leads to solidification of the material at temperatures below 200°C and pressures exceeding 10 MPa. The process is accompanied by volatile product formation. However, phenol-formaldehyde resins of the resol type can be cast without additional pressure and heat. The raw molding reactants contain different organic and mineral fillers and other additives in addition to the basic resin. 

One of the earliest commercial plastics was Bakelite , formed by the reaction of phenol with a little more than one equivalent of formaldehyde under acidic or basic conditions. Baeyer first discovered this reaction in 1872, and practical methods for casting and molding Bakelite were developed around 1909. Phenol-formaldehyde plastics and resins (also called phenolics) are highly cross-linked because each phenol ring has three sites (two ortho and one para) that can be linked by condensation with formaldehyde. Suggest a general structure for a phenol-formaldehyde resin, and propose a mechanism for its formation under acidic conditions. (Hint Condensation of phenol with formaldehyde resembles the condensation of phenol with acetone, used in Problem 26-17, to make bisphenol A.)... 

Phenolic and Other Tar Acid Resins Casting. Phenolic and other tar acid resins for casting are disclosed from 1934 to 1937, and phenol-formaldehyde for casting is disclosed from 1938 to 1941 and for 1943 (11). 

The potential applications for conducting polymers are enormous and this has stimulated a large amount of research into this area. Not surprisingly, solid-state NMR spectroscopy has been applied to study these amorphous, insoluble and in many cases crosslinked materials [24]. Looking at the CP/MAS spectra of a series conducing polyacenic polymers, some of which were doped with iodine, it was possible to see the effect of the halogen upon conductivity. These resins were prepared by a conventional procedure for the preparation a Novolak-type phenol-formaldehyde resin. After synthesis, the phenol-formaldehyde resin were dissolved and solutions were cast as a film and heat treated to between 590-670°C in a N2 atmosphere to form the polyacenic film. The electrical conductivity of the films was shown to increase... 

Phenol-formaldehyde resin Phenolic resin cast goods... 

To avoid corrosion, cast iron, enamel or nickel-clad reactors, and plastic HCl pipelines (e.g. from phenol-formaldehyde resins or polyvinylidene fluoride) or glass or enamel pipes are employed iron Raschig rings are used as the catalyst, placed as a layer on the reactor base. 

Cast phenolics. Phenolic casting resins are available as syrupy liquids produced in huge kettles by the condensation of formaldehyde and phenol at high temperature in the presence of a catalyst and the removal of excess moisture by vacuum distillation. These resins, when blended with a chemically active hardener, can be cast and cured solid in molds constructed from various materials and of a variety of mold designs. They will exhibit a broad-based property profile as described in Table 2.14. 

Molding Compounds, Phenol-formaldehyde (Cont d) Casting Resins Nylon Alloys Nylon, Type 6... 

In 1872, Baker found that the reaction between phenol and formaldehyde yielded a resinous product. The resin could be formed and cured and thus used for the production of a variety of moulded and cast plastic products. Baekland made the first successful commercial exploitation and the product entered the market in 1909 under the name of Bakelite. This was the first wholly synthetic polymer. Fillers and other additives were used to improve the product. From these first resins, other varieties have been developed so that phenol-formaldehyde resins now designate a group of resins with varying properties made from different phenols and aldehydes. 

Previously, phenol-formaldehyde resins were often used as casting compounds for products such as knobs, electrical switches, ash trays and many others. This use has diminished and, nowadays, the resins are mainly used as binders in different products. Large quantities are used, for example, in building, construction, car, leather, shoe, moulding and electric industries. 

Phenol-formaldehyde resin Cast epoxy resin Nylon 6,6... 

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