Phenol-formaldehyde resin-resorcinol

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. 

Furfural has replaced formaldehyde in phenol-resorcinol-formaldehyde resins.These formaldehyde-containing resins have been used as cold-set, exterior grade structural wood adhesives for almost half a century. The use of furfural to prepare these resins has several advantages. In addition to longer resin shelf life, when furfural is used, the emission of formaldehyde is lowered. To enhance the reaction rate when furfural is used, a small amount of formaldehyde is added to the furfural system. Hence, the furfural system is not formaldehyde-free, but nearly so. Finally, furfural has a higher molecular weight than formaldehyde. This results in a smaller amount of the expensive resorcinol being required in the system. 

Fire PRF2. [Indspec] Two-component phenol resorcinol-formaldehyde resin flame retardant thetmoset for fabricating fume and smoke exhaust ducts, fire-retardant components. 

Figure 9 depicts the somewhat similar behavior for a room-temperaturesetting, urea-formaldehyde or phenol-resorcinol-formaldehyde resin-based glue. However, no initial heat-related drop in viscosity occurs during clamping, and the final polymerization hardening proceeds at a slower rate because it occurs at room temperature. 

Two types of m-aminophenol modified adhesives have been reported. The first is a multicomponent system that is not too easy to handle. " " Part I is a slow reacting phenol-resorcinol-formaldehyde resin (A) mixed with paraformaldehyde (B) as hardener and Part II is a phenol-m-aminoph-enol-formaldehyde resin (C) at a high pH mixed with a very slow hardener (D). Each part is applied to one surface and, after mating, the reactive components are mixed by diffusion and a cure results within minutes. 

A-ring of the tannin (194). Resin synthesis conditions varied in the approach to addition of formaldehyde. For example, the tannins could be crosslinked by reaction of a phenol-resorcinol-formaldehyde resin carrying little or no methylol functionality by addition of paraformaldehyde or by reaction of a phenol-formaldehyde prepolymer carrying a comparatively high methylol functionality. Adhesive formulations were similar to those described above. Typically, 100 parts of a 55% solids content water solution of wattle tannin were combined with 0.25 parts of defoamer, 7 parts of paraformaldehyde and 9 to 10 parts of coconut shell powder the pH was adjusted to 6.5 to 7.4 by addition of 40% NaOH. These adhesives also provided exterior quality glue lines. They are exceptional in their tolerance to high moisture content veneer and permit fast curing rates, subjects of particular interest in the plywood industry today. 

Phenol-resorcinol formaldehyde resins Structure determination [123]... 

Most of the aramid adhesive systems initially used were based on a first-step dip of either an epoxide or a blocked polyisocyanate and then a second or top coat of RFL. Wenghoefer in his patent disclosed a somewhat different first step dip which consisted of bis(j3-azido-formyl oxyethyl)isophthalate. After drying, the cord thus treated, was then dipped in a phenolic adhesive and cured at 230 C for 60 seconds. A patent issued to Van Gils uses a one-step dip based on vinyl pyridine latex, trimethylol-phenol, resorcinol-formaldehyde resin, and... 

Nitrile rubber is compatible with phenol-formaldehyde resins, resorcinol-formaldehyde resins, vinyl chloride resins, alkyd resins, coumarone-indene resins, chlorinated rubber, epoxies and other resins, forming compositions which can be cured providing excellent adhesives of high strength, high oil resistance and high resilience. On the other hand, NBR adhesives are compatible with polar adherends such as fibres, textiles, paper and wood. Specific formulations of NBR adhesives can be found in [12]. 

Laminated beams (glulam), parallam (or LSL) and fingerjoints a flat pressed multilayer wood beam, thiek wood planks constituting the layers, used for structural exterior applications and bonded with PRF (phenol-resorcinol-formaldehyde) cold-setting resins, or MUF cold-setting resins, or even with certain types of polurethanes (although the use of these latter ones is only established in one country and can show creep and temperature-induced creep problems). The indi-... 

More recently, a modification of the system described by Kreibich has been used extensively in industry with good success. Part A of the adhesive is again a standard phenol-resorcinol-formaldehyde (PRF) cold-setting adhesive, with powder hardener added at its standard pH. Part B can be either the same PRF adhesive with no hardener and the pH adjusted to 12, or a 50 to 55% tannin extract solution at a pH of 12-13, provided that the tannin is of the condensed or flavonoid type, such as mimosa, quebracho, or pine bark extract, with no hardener [118,135-137], The results obtained with these two systems are good and the resin not only has all the advantages desired but also the use of vegetable tannins and the halving of the resorcinol content makes the system considerably cheaper [118,135-137]. 

An additional activating hydroxyl group on the phenolic ring allows resorcinol to react rapidly widi formaldehyde even in die absence of catalysts.8 Hiis provides a method for room temperature cure of resorcinol-formaldehyde resins or mixed phenol-formaldehyde/resorcinol-formaldehyde resins. Trihydric phenols have not achieved commercial importance, probably due to tiieir higher costs. 

Applications for cold-setting, wood-laminating adhesives initially followed the same approach (47) used for laminating resins from western hemlock (38) (i.e., reaction of tannin with phenol-resorcinol-formaldehyde prepolymers). Improvements resulted through the application of Kreibich s Honeymoon technique (48) wherein one side of the material to be bonded is treated with resin and the other with catalyst. One of the preferred systems (49) was phenol-resorcinol-formaldehyde or tannin-resorcinol-formaldehyde at pH 8 with extra paraformaldehyde on the A-side and tannin at 53% solids or tannin-resorcinol-formaldehyde at pH 12 on the B-side. Such resin systems are currently used to laminate eucalyptus or pine in most South African timber-laminating plants. 

In order to establish control values for the adhesives formulated using tannins, the initial work was done with phenol-resorcinol-formaldehyde (PRF) or resorcinol-formaldehyde (RF) resins on both surfaces, but modified for the honeymoon principle. The PRF resin chosen for this work was Borden s resin LT-75 with Borden s hardener FM-260. The RF resin used for a comparison was Chembond s RF-900. These resins have been used for wood gluing in the United States for more than two decades, especially for the manufacture of structural laminated timbers. 

Ultra thin microporous carbon films are derived via the pyrolysis of phenolic precursors. The latter can be prepared from resorcinol-formaldehyde resins using a base catalyst. After several hours at 50°C of curing, the solution forms a stable polymeric film. Followed by a solvent exchange and ambient pressure drying, the film is pyrolysed in argon atmosphere at temperatures above 800°C. The result is an electrically conducting polymeric carbon film, the structure of which resembles the organic precursor, but shows microporosity in addition. Hereby, films with thicknesses of > 5 microns and sufficient mechanical stability can be made. 

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