Novolac phenol formaldehyde resins

Novolac resins (phenol/formaldehyde condensates). were characterized on a 50°C C g column (A = 280nm) using a 40-min 40/60 -> 100/0 methanol/water gradient... 

Novolac type phenol formaldehyde resins are generally used as binders in these applications. This mechanism is shown in the scheme ... 

Phenol formaldehyde resins (pol3miethylene phenylene) are polymers with irregular cross-linked structure. During friction of resol- and novolac-t3rpe phenol formaldehyde pol3miers two processes take place simultaneously, namely structuring (aftercure) via recombination of weak ester groups... 

Leo Hendrik Baekeland s process for the phenol-formaldehyde polycondensation resin that he called Bakelite was patented in 1907 and commercialized by his General Bakelite Company, established in Perth Amboy, New Jersey, in 1910. A British factory, a subsidiary of Bakelite s German holding company, was opened at Cowley, Middlesex, in 1914. Baekeland also coined the name Novolac, which at one time was used as the trade mark for Novolak phenol-formaldehyde resins, following his observation that they behaved like lac resins. Phenol-formaldehyde resins were found to be thermosetting (hard and unmouldable when heated), and formed by condensation ... 

Phenol-formaldehyde resin. See Novolac resin Phenolic resin... 

SiC nanofibers by melt-spinning of polymer blends have been prepared from PCS as a SiC ceramic precursor and a novolac-type phenol-formaldehyde resin [121]. These nanofibers were amorphous, about 100 nm in diameter, more than 100 (un long, and were rich in oxygen. 

Novoloid fiber A phenolic fiber made by cross-linking a melt-spun novolac resin with formaldehyde. Novoloid fibers have good flame resistance, can serve at temperatures to about 220°C, and are used as reinforcement in a range of thermosetting matrices. 

Synonyms P-F-R-2 resol phenol formaldehyde resin phenol formaldehyde phenol polymer with formaldehyde formaldehyde-pnenol polymer paraformaldehyde-formaldehyde-phenol polymer paraformaldehyde-phenol polymer phenol-formaldehyde polymer Novolac Resole resol based on phenol, resorcinol, and formaldehyde... 

There are two types of phenol-formaldehyde condensation polymers resoles and novolacs (117). Phenol-formaldehyde polymers prepared from the base-catalyzed condensation of phenol and excess formaldehyde are called resoles. In most phenolic resins commonly used with epoxies, the phenolic group is converted into an ether to give improved alkali resistance. At elevated temperatin-es (>150°C), resole resins react with the hydroxyl groups of the epoxy resins to provide highly cross-linked polymers. 

Being a glycidyl ether of a novolac type phenol formaldehyde resin, epoxy phenol novolac resins (Figure 2.39 (a)) are the polymeric multifunctional counterpart of bisphenol F resin. They are supplied as highly viscous through semisolid to solid resins. They are generally prepared by reacting epichlorohydrin with novolac type phenol formaldehyde resins. 

Epoxy novolac resins are produced by glycidation of the low-molecular-weight reaction products of phenol (or cresol) with formaldehyde. Highly cross-linked systems are formed that have superior performance at elevated temperatures. 

Two-Stage Resins. The ratio of formaldehyde to phenol is low enough to prevent the thermosetting reaction from occurring during manufacture of the resin. At this point the resin is termed novolac resin. Subsequently, hexamethylenetetramine is incorporated into the material to act as a source of chemical cross-links during the molding operation (and conversion to the thermoset or cured state). 

I ovolac Synthesis and Properties. Novolac resins used in DNQ-based photoresists are the most complex, the best-studied, the most highly engineered, and the most widely used polymers in microlithography. Novolacs are condensation products of phenoHc monomers (typically cresols or other alkylated phenols) and formaldehyde, formed under acid catalysis. Figure 13 shows the polymerization chemistry and polymer stmcture formed in the step growth polymerization (31) of novolac resins. 

Most processors of fiber-reinforced composites choose a phenol formaldehyde (phenoHc) resin because these resins are inherently fire retardant, are highly heat resistant, and are very low in cost. When exposed to flames they give off very Htde smoke and that smoke is of low immediate toxicity. PhenoHc resins (qv) are often not chosen, however, because the resole types have limited shelf stabiHty, both resole and novolac types release volatiles during their condensation cure, formaldehyde [50-00-0] emissions are possible during both handling and cure, and the polymers formed are brittle compared with other thermosetting resins. 

A hard carbon with high capacity can be made from epoxy novolac resin [12]. The epoxy resins used cost about US 2.50 per pound and give pyrolysis yields between 20 and 30%. However, it is well known that phenolic (or phenol-formaldehyde) resins can be pyrolyzed to give hard carbons with a yield of over 50% [42]. In addition, these resins cost about USSl.OO per pound. Phenolic resins therefore offer significant cost advantages over epoxy resins, so we... 

The term novolac refers to the early use of phenolic to replace expensive shellac-based coatings. Novolacs are now those resins made at formaldehyde-to-phenol molar ratios of less than one-to-one. They are generally, though not always, manufactured under acidic conditions. Sulfuric or oxalic acids are most often chosen as catalyst though aromatic sulfonic acids and phosphoric acid are also quite common. Many other acids are used for special purposes. The finished novolac resin is incapable of further polymerization or crosslinking and therefore... 

Phenolics or phenol-aldehydes include the important commercial phenolic resin bakelite based on phenol and formaldehyde. A one-step process produces resol resin from more than one molecule of formaldehyde per phenol molecule. A two-step process uses an excess of phenol to produce novolacs - resins that have no reactive methylol groups and must be mixed with an aldehyde o undergo further reaction. 

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). ... 

Linear novolac resins prepared by reacting para-alkylphenols with paraformaldehyde are of interest for adhesive tackifiers. As expected for step-growth polymerization, the molecular weights and viscosities of such oligomers prepared in one exemplary study increased as the ratio of formaldehyde to para-nonylphenol was increased from 0.32 to 1.00.21 As is usually the case, however, these reactions were not carried out to full conversion, and the measured Mn of an oligomer prepared with an equimolar phenol-to-formaldehyde ratio was 1400 g/mol. Plots of apparent shear viscosity versus shear rate of these p-nonylphenol novolac resins showed non-Newtonian rheological behavior. 

The most common crosslinking agent for novolac resins is HMTA which provides a source of formaldehyde. Novolac resins prepared from a phenol-formaldehyde (F/P) ratio of 1/0.8 can be cured with 8-15 wt % HMTA, although it has been reported that 9-10 wt % results in networks with the best overall performance.3... 

Since a small amount of water is always present in novolac resins, it has also been suggested that some decomposition of HMTA proceeds by hydrolysis, leading to the elimination of formaldehyde and amino-methylol compounds (Fig. 7.15).42 Phenols can react with the formaldehyde elimination product to extend the novolac chain or form methylene-bridged crosslinks. Alternatively, phenol can react with amino-methylol intermediates in combination with formaldehyde to produce ortho-or para-hydroxybenzylamines (i.e., Mannich-type reactions). 

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

Novolac resins are condensation products of phenol and formaldehyde made in the presence of an acid catalyst such as hydrochloric acid, sulfuric acid or oxalic acid. For novolac resins, mole ratios of phenol to formaldehyde vary from 1 0.5... 

Fig. 13. Polymerization chemistry of phenol—formaldehyde condensation synthesis of novolac resin. The phenol monomer(s) are used in stoichiometric excess to avoid gellation, although branching invariably occurs due to the multiple reactive sites on the aromatic ring.

For example, novolacs are phenolic resins obtained by the condensation of phenol (trifunctional monomer) and formaldehyde (bifunctional monomer), using a stoichiometric excess of phenol so that formaldehyde is completely consumed without leading to gelation. In a second step, instead of directly adding the necessary formaldehyde, the polymer network is formed by reaction with hexamethylenetetramine (a condensation product of formaldehyde and ammonia usually called hexa), through a complex set of chemical reactions (Chapter 2). 

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). 

Trimethylsilylmethylphenol and o-cresol were obtained from Petrarch Systems, Inc. and Aldrich Chem. Co. Inc., respectively. Silylated novolac (Sl-novolac) resins were prepared by condensation polymerization of p-trimethylsilylmethyl phenol, o-cresol and formaldehyde. Poly(2-methyl-l-pentene-sulfone) (PMPS) was prepared as described in the literature (12). 

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