Resorcinol-formaldehyde polymers

In the manufacture of pure resorcinol resins, the reaction can be violently exothermic unless controlled by the addition of alcohols. Because the alcohols perform other useful functions in the glue mix, they are left in the liquid adhesive. PRF adhesives are generally prepared firstly by reaction of phenol with formaldehyde to form a PF resol polymer, that has been proved to be in the greatest percentage, and often completely, linear [95], In the reaction step that follows the resorcinol chemical is added in excess to the PF-resol to react it with the PF-resin -CH2OH groups to form PRF polymers in which the resorcinol groups can be resorcinol chemical or any type of resorcinol-formaldehyde polymer. 

The resorcinol-formaldehyde polymers have been used to prepare highly porous carbon materials, by controlled pyrolysis in an inert atmosphere [144,154], The microstructure of the carbon is an exact copy of the porous polymer precursor. Poly(methacrylonitrile) (PM AN) PolyHIPE polymers have also been used for this purpose. These monolithic, highly porous carbons are potentially useful in electrochemical applications, particularly re-chargeable batteries and super-capacitors. The RF materials, with their very high surface areas, are particularly attractive for the latter systems. 

Tao et al. [85] synthesized zeolite Y with a significant portion of mesopores by adding the resorcinol-formaldehyde polymer to the zeolite synthesis mixture. Nitrogen adsorption isotherms showed the presence of mesopores with a pore diameter close to 10 nm and a pore volume of 1.37 cm3/g. The presence of mesopores was also confirmed by field-emission scanning electron microscopy. 

Fig. 2. Morphology of resorcinol-formaldehyde polymers prepared in water and in the presence of NaOH at various pH values. Synthesis temperature = 70°C, dilution ratio = 5.7.

Fujikawa D, Uota M, Yoshimura T, Sakai G, Kijima T (2006) Surfactant-templated synthesis of resorcinol-formaldehyde polymer and carbon nanostructures nanospheres and nanowires. Chem Lett 35 432 33... 

Xu J, Wang A, Zhang T (2012) A two-step synthesis of mdered mesoporous resorcinol-formaldehyde polymer and carbon. Carbon 50 1807-1816... 

The resorcinol-formaldehyde polymer is classified as a phenolic resin. In fact, phenol-formaldehyde condensates are the first synthetic polymers introduced commercially (Bakelite) in the beginning of the twentieth century. Thus, the phenolic resin chemistry, on which there is a vast amotmt of information, can be used to understand the chemistry of the RF aerogel synthesis. In the first step, resorcinol reacts with formaldehyde to form hydro-xymethylated resorcinol in the second step, the hydroxymethyl groups condense with each other to form nanometer-sized clusters, which then crosslink by the same chemistry to produce a gel. The formation of clusters is influenced by typical sol-gel parameters such as the temperature, pH, and concentration of reactants. Though the first RF aerogel is synthesized by the aqueous polycondensation of resorcinol with formaldehyde with the use of sodium carbonate as catalyst [6, 12, 13], now several literature reports exist for aerogels made from phenol and formaldehyde [14—16]. 

Tungsten carbides were fabricated via polymer-induced carburization of the mixture of a tungsten salt (ammonium metatungstate) and carbon polymer structures (resorcinol-formaldehyde polymer) by Lee and co-workers (33-35). The polymer intermediate, in which the metal salt was trapped, was annealed at 1173 K under Ar and H2 gas. Various phases and morphologies of WC were prepared by control of polymerization conditions. The surface areas of obtained hep W2C and hex WC were 176 and 77 m /g, respectively. However, these high surface areas contained some contribution from the unreacted carbons. 

Wattle tannin-based plywood adhesives were also crosslinked with 10% to 20% (by weight of solids) of either a phenol-formaldehyde resol or a phenol-resorcinol-formaldehyde polymer with approximately 20% resorcinol, to which paraformaldehyde was added to provide crosslinking between the resorcinol and... 

Tire Cord. Melamine resins are also used to improve the adhesion of mbber to reinforcing cord in tires. Textile cord is normally coated with a latex dip solution composed of a vinylpyridine—styrene—butadiene latex mbber containing resorcinol—formaldehyde resin.. The dip coat is cured prior to use. The dip coat improves the adhesion of the textile cord to mbber. Further improvement in adhesion is provided by adding resorcinol and hexa(methoxymethyl) melamine [3089-11 -0] (HMMM) to the mbber compound which is in contact with the textile cord. The HMMM resin and resorcinol cross-link during mbber vulcanization and cure to form an interpenetrating polymer within the mbber matrix which strengthens or reinforces the mbber and increases adhesion to the textile cord. Brass-coated steel cord is also widely used in tires for reinforcement. Steel belts and bead wire are common apphcations. Again, HMMM resins and resorcinol [108-46-3] are used in the mbber compound which is in contact with the steel cord to reinforce the mbber and increase the adhesion of the mbber to the steel cord. This use of melamine resins is described in the patent Hterature (49). 

We are applying the principles of statistical experimental design to the development of low-density polymer foams for use as direct-drive high-gain targets for Laser Inertial Confinement Fusion (ICF). Both polystyrene (PS) and resorcinol-formaldehyde (RF) foams are being developed. 

An emulsion polymer-isocyanate adhesive, a crosslinked polyvinyl acetate adhesive, a resorcinol-formaldehyde adhesive, a phenol-resorcinol-formalde-hyde adhesive, and an acid-catalyzed phenolic-formaldehyde adhesive developed bonds of high shear strength and wood failure at all levels of acetylation in the dry condition. A neoprene contact bond adhesive and a moisture-curing polyurethane hot-melt adhesive performed as well on acetylated wood as untreated wood in tests of dry strength. Only a cold-setting resorcinol-formal-... 

The phosphorylation of phenol-furfural condensate affords a cation-exchange resin with improved thermal and chemical reristance. The heat treatment of phosphonic add resins from furfural redns, phenol-resorcinol-formaldehyde resin, and polystyrene at 100-180 °C for 10-48 h shows that the furfural-based phosphonic acid resins possess higher thermal stability than those from the other two polymers. 

Dihydric phenolic lipids of the cardol type are the most abundant in plant, fungal and bacterial kingdoms. The first species in which the members of the title subclass of phenolic lipids, resorcinolic lipids, were found was Ginkgo biloba (Ginkgoaceae) [6,9,10,17]. Later, the presence of resorcinolic lipids (5-n-alk(en)ylresorcinols) was shown also in other species, first, in the Anacardiaceae [14], which is an important source of various phenolic lipids, not only of alkylresorcinols but also of alkylphenols and alkylcatechols. For example, the cashew and the processing of cashew nuts are the main source of phenolic lipids for the formaldehyde-polymer industry. Aspects of Anacardium occidentale in relation to synthesis, semi-synthesis and chemical industry have been reviewed Tyman [1,11,14] as well as a recent book [2]. 

Recently, we have synthesized microporous carbons [6] and Pt particles supported on microporous carbon [7] by carbonization of cationic surfactant-anionic resorcinol/formaldehyde (RF) composites. The porous structure produced by decomposition of the surfactant plays an important role for the gasification of the RF polymer at higher temperatures. However, the average pore size of the microporous carbons obtained with this method is smaller than... 

Studies on the behavior of chromium, molybdenum and tungsten oxide-doped monolithic carbon aerogels in the isomerization of 1-butene have been carried out by the group of Moreno-Castilla [38]. Samples were prepared by polymerization of a resorcinol-formaldehyde mixture which contained metallic salts of the elements and then the polymer was carbonized at both 500 and 1000 °C. The catalyhc performance of the samples was studied at temperatures ranging from 50 to 425 °C. 

So, in this chapter the interest and importance of the polymer gel theory approach to the formulation of adhesives will be briefly shown and, in particular, we will limit this to thermosetting wood adhesives obtained by polycondensation such as phenol-formaldehyde-, urea-formaldehyde-, melamine-formaldehyde- and resorcinol-formaldehyde-based adhesives. The same approach is, however, very valid for other polycondensation resins, and also for adhesives obtained by routes other than polycondensation. 

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