Phenol-formaldehyde novolac

An alternative copolymerization is illustrated by the method of Blasius. In this preparation, a phenol-formaldehyde (novolac) type system is formed. Monobenzo-18-crown-6, for example, is treated with a phenol (or alkylated aromatic like xylene) and formaldehyde in the presence of acid. As expected for this type of reaction, a highly crosslinked resin results. The method is illustrated in Eq. (6.23). It should also be noted that the additional aromatic can be left out and a crown-formaldehyde copolymer can be prepared in analogy to (6.22). ... 

Phenol-epoxy reaction. See also Epoxy-phenolic reaction entries tertiary amine-catalyzed, 412 triphenylphosphine-catalyzed, 412 Phenol-formaldehyde novolac resin, preparation of, 429... 

We now compare theoretical predictions with experimental results obtained using silica sand coated with a 4% resin consisting of 100 parts by weight of a phenol-formaldehyde novolac and 5, 10, or 15 parts of hexamethylenetetramine (hexa) as hardener (Aranguren et al., 1984). 

Fig. 15. Viscoelastic behavior of isocyanurate-oxazoiidone resins51). DEN 431 (polyglycidyl ether of phenol-formaldehyde novolac Dow Chemical Co.), EP 4080 (2,2-bis[p-(2,3-epoxypropyloxy)cyclo-hexane]propane Asahi Denka, Ltd.), EP 871 (diglycidyl ester of linoleic dimer acid Shell Chemical Co.), and L-MDI (modified diphenylmethane-4,4 -diisocyanate Desmodur CD Bater AG)...

All samples were prepared from a commercially available epoxy cresol novolac-phenol formaldehyde novolac-tertia-ry amine based molding compound. Pelletized preforms were heated to 85°C in a RF preheater prior to being transfer molded at 180°C/68 atm. for 90 sec. Molded samples were cooled in air to room temperature and stored in a desiccated environment until testing or subsequent thermal treatment. Post mold curing, PMC, was accomplished in a gravity oven at 175°C for a period of 4 hours. Samples without post mold curing are designated by NPMC. 

The chemistry was extended to phenol-formaldehyde novolac, trisphenol novolac and dicyclopentadiene-phenol novolac (12V Structures of these products are shown as follows ... 

Numata and Kinjo (52) have shown rubber-modified isocyanurate-oxazolidone resins may be effectively modified with carboxyl-reactive nitrile liquids. The viscoelastic behavior of models using a polyglycidyl ether of phenol-formaldehyde novolac resin and di-phenylmethane-4,4 -diisocyanate is discussed. Such resins have suggested utility in thin films as electrical varnishes. 

A second type of epoxy resin is made by reaction of phenol-formaldehyde novolacs with epichlorohydrin (Fig. 3.22). Using novolacs of DP 2-6 gives solid resins and permits much higher cross-linking, giving cured products of higher heat and chemical resistance. 

The condensation reaction of tetraethoxypolyphenykilsesqui-oxane with the excess of epichlorohydrin in the presence of catalysts Fe (III) and A1 chloride has been investigated and corresponding tetra epoxy-derivatives has been obtained. By polymerization reaction of tetraepoxypol5q)henylsilsesquioxanes with phenol-formaldehyde novolac oligomers epoxy-siliconorganic and phenol-formaldehyde novolac block-copolymers have been obtained. 

Phenol/formaldehyde novolac resins react with epoxy groups at elevated temperatures to give highly cross-linked systems, with a high service temperature >150°C and excellent chemical resistance. The typical epoxy/ novolac ratio is 0.9 to stoichiometric a tertiary amine accelerator is necessary for complete cure. 

The mechanism of the pyrolysis of phenol-formaldehyde novolac resins was studied in greater detail in [17]. A resin with labelled carbon in the methylene bridges was synthesized to determine from what structural elements of the resin the coke and gases are formed. 

Epoxy NovolaC Resins. Epoxy novolacs are multifunctional epoxies based on phenolic formaldehyde novolacs. Both epoxy phenol novolac resins (EPN) and epoxy cresol novolac resins (ECN) have attained commercial importance (53). The former is made by epoxidation of the phenol-formaldehyde condensates (novolacs) obtained from acid-catalyzed condensation of phenol and formaldehyde (see Phenolic Resins). This produces random ortho- and para-methylene bridges. 

Epoxy novolacs are made by glycidylation of phenol formaldehyde novolacs, the latter being the low molecular weight thermoplastic condensation products from phenol and formaldehyde that are formed under conditions of excess phenol and acidic catalysis (see Section 9.2.3.1). The resins are of the structural type shown in Structure 9.6, the methylene... 

Vinyl ester resins are based on the reaction product of an epoxy resin and an ethylenically unsaturated carboxylic acid which results in a terminal unsaturation. Various epoxy resins are used, such as the diglycidyl ether of bisphenol A or higher homologues and epoxylated phenol-formaldehyde novolac. The most commonly used acids are acrylic and methacrylic acid. 

Resins with improved flame-retarding properties were obtained from BMI containing phosphorus cured with different kinds of agents (Tsai et al. 2009) or by blending a commercial phenolic epoxy resin containing phosphorous and melamine phenol formaldehyde novolac with various amounts of BMI (Chiang et al. 2013). 

Figure 10.3 Shear modulus Cj and logarithmic decrement of a phenol-formaldehyde resin cross-linked with hexamethylene tetramine at stated concentrations. (Reproduced from Drumm, M.F., Dodge, W.H. and Nielsen, LE. (1956) Cross linking of a phenol-formaldehyde novolac - determination by dynamic mechanical measurements. Ind. Eng. Chem., 48, 76. Copyright (1956) American Chemical Society.)...

Zhang X, Hu H, Zhu Y, Zhu S (2007) Carbon molecular sieve membranes derived from phenol formaldehyde novolac resin blended with poly(ethylene glycol). J Membr Sci 289 (1-2) 86-91... 

Wei W, Hu H, You L, Chen G (2002) Preparation of carbon molecular sieve membrane from phenol-formaldehyde novolac resin. Carbon 40 (3) 465-467... 

Phenol-formaldehyde novolac resins are formed by the incomplete polymerization of phenol and formaldehyde. Insufficient formaldehyde is present to allow complete cme. Complete crosslinking can be achieved by adding a powdered methylene donor such as hexamethylenetetramine and heat. Resorcinol-formaldehyde novolac liquid resins can be eured by the addition of powdered paraformaldehyde. 

Using dynamic mechanical analysis the curing reactions of typical phenol-formaldehyde novolac resins were followed. The evolution of various rheological parameters was recorded for samples of the resins on cloth. A third-order phenomenological equation described the curing reaction. The influences of the structure, composition and physical treatment on the curing kinetics were evaluated. 20 refs. 

Phenol-formaldehyde Novolac resin Asymmetric tubular Wei et al. (2002)... 

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