Phenolic resole resins

Macrospheres made from resol phenolic resins, with diameters of 0.2-5.0 mm, are also used for syntactic foams118). 

Using the classical resol chemistry, Asai and coworkers patented new molded materials.Added to the resol phenolic resin are inorganic fiber, a silica powder, and a rubber component. The prepared phenolic resin composition was noted to have excellent resistance to abrasive wear and to heat shock, as well as excellent mechanical strength. As such, this material is very suitable for the fabrication of engine parts such as pulleys. These pulleys are currently fabricated from heavier and more expensive materials. 

Fig. 14 3-D chromatogram from a diode-array UV absorption detector (a) blended vegetable oil (b) the blended vegetable oil after reaction with a resole phenolic resin. (From N Hessefort, M Hedstrom, W Greive. LC-GC 7 130, 1989. Reprinted courtesy of Aster Publishing Company.)...

Phenolic Resins. Phenolic resins (qv) are formed by the reaction of phenol [108-95-2], C H O, and formaldehyde [50-00-0], CH20. If basic conditions and an excess of formaldehyde are used, the result is a resole phenolic resin, which will cure by itself liberating water. If an acid catalyst and an excess of phenol are used, the result is a novolac phenolic resin, which is not self-curing. Novolac phenolic resins are typically formulated to contain a curing agent which is most often a material known as hexamethylenetetraamine [100-97-0], C6H12N4. Phenolic resin adhesives are found in film or solution... 

In the case of a resole phenolic resin, the presence of trisilanolphenyl PGSS markedly increased the thermal stability of the phenolic nanocomposites. The... 

Figure 2.7 Structural formula for two-stage resole phenolic resin.

Phenolic-modified alkyds are made by heating the alkyd with a low molecular weight resole phenolic resin based on p-alkylphenols. Presumably, the methylol groups on the phenols react with some of the imsatmated groups of the alkyd to form chroman structures. The resins give harder films with improved water and chemical resistance as compared to the immodified alkyd. 

Phenolic resins, which are formed as condensation products of formaldehyde and different phenols, form the basis of a unique class of rigid, cross-linked polymers. From a structural point of view, these resins are categorized into two types, one-step (resole) resins and two-step (Novolac) resins. One-step (resole) phenolic resins are formed from phenol and an excess of formaldehyde, in an aqueous catalytic medium. The reaction is terminated before the completion to produce a resin material that may be cross-linked in its final application. Both liquid and solid forms of these resins are available, and are formed by removing water or retaining water from the reaction. Phenolic resole resins are a mixture of the following compounds ... 

Rapidly curing resole phenolic resins have been reported to use barium acetate and zinc nitrate and organic peroxides [105],... 

Uncatalysed resole phenolic resins have excellent storage stability, but add catalysed ones have only a limited life at room temperature. Latent add catalysts have been developed to overcome this problem. They are used in readion injection moulding (RIM) and in resin transfer moulding (RTM) processes. Examples are phenyl hydrogen maleate, phenyl trifluoroacetate and butadiene sulfone. At elevated temperatures these catalysts generate the corresponding acids, which catalyse the resole reactions. A cycle time of one to two minutes at 150°C is achievable. The choice of a suitable latent catalyst can also reduce the peak exotherm temperature. 

The most common types of adhesives used today in coated products are hide glues, varnishes, urea-formaldehyde, radiation-curable, and resole phenolic resins. Depending on the severity of the applications, the make and size bond formulations are modified to suit the job at hand. Combinations of the above systems are used to achieve special properties which may give certain products economic and performance advantages. 

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