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The phenol–formaldehyde reaction is usually carried out in aqueous solution. Under these conditions, formaldehyde adds water in an equilibrium reaction to form formaldehyde hydrate ( Eq. 21.29 ). 21.29 H 2 C = O formaldehyde + H 2 O ⇌ HOCH 2 OH formaldehyde hydrate
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2021-3-12 Phenolic resins: 1. Mechanisms and kinetics of phenol and of the first polycondensates towards formaldehyde in solution. Polymer 1994, 35 (14) , 3046-3054. https://doi.org/10.1016/0032-3861(94)90418-9; J. Reese. Reindarstellung der Polymethylol-Verbindungen des Phenols.
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Reaction rate con- stants were determined from measurements of the con- centrations of the phenolic compounds and formalde- hyde as functions of time. The reaction rate constants varied over a wide...
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The initial phenol-formaldehyde reaction products may be of two types, novolaks and resols. Phenol-formaldehyde reactions catalyzed by zinc acetate as opposed to strong acids have been investigated, but this results in lower yields and requires longer reaction
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2005-7-26 lar amounts of phenol and formaldehyde are consumed as the reaction proceeds as is expected for a reaction in which the stoichiometric coefficients of phenol and formaldehyde are identical. The reaction of phenol with formaldehyde corre- sponds to an electrophilic aromatic substitution (Fig. 3).
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2013-1-5 Phenol-formaldehyde resins These thermosetting resins are obtained by reacting phenol C 6 H 5 OH and phormaldehyde CH 2 O. Formaldehyde forms −CH 2 − bridges between two phenol molecules, producing chains. Linear chains are obtained
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In the sodium hydroxide‐catalyzed phenol‐formaldehyde reaction, it has now been possible to isolate the first two parallel reactions leading to the formation of o‐ and p‐methylol phenols and to study, by means of quantitative ascending paper chromatography, their kinetics and energetics. The reactions are kinetically of second order, one with ...
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The reaction of phenol with formaldehyde: II. The ratio of ortho‐ and para ‐hydroxymethylphenol in the base‐catalyzed hydroxymethylation of phenol.
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2019-5-26 The reaction of phenol with formaldehyde: II. The ratio of ortho- and para-hydroxymethylphenol in the base-catalyzed hydroxymethylation of phenol.. Recueil des Travaux Chimiques des Pays-Bas 1959, 78 (11) , 851-863. https://doi.org/10.1002/recl.19590781102; Noboru OOTA, Zyun'iti OOKUMA.
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The reaction between phenol and formaldehyde in . alkaline solution leads to the introduction of a hydroxy - methyl group into the aromatic nucleus at positions .
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2005-7-26 formaldehyde bears a positive charge, while the o- and p -positions of the aromatic ring bear negative charges. Because there are no apparent steric factors to prevent reaction, one predicts that formaldehyde will react with phenol at the o- and p -positions, as is observed experi- mentally. Thus, the electrons in the HOMO orbital of
Read MoreThe initial phenol-formaldehyde reaction products may be of two types, novolaks and resols. Phenol-formaldehyde reactions catalyzed by zinc acetate as opposed to strong acids have been investigated, but this results in lower yields and requires longer reaction
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The reaction mechanisms of phenol–formaldehyde polymerization are complicated in both acid- and base-catalyzed reaction systems. Furthermore, there is a considerable release of heat during their ...
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In the sodium hydroxide‐catalyzed phenol‐formaldehyde reaction, it has now been possible to isolate the first two parallel reactions leading to the formation of o‐ and p‐methylol phenols and to study, by means of quantitative ascending paper chromatography, their kinetics and energetics.
Read MoreRunway reactions: Phenol–formaldehyde low-temperature runaway reaction: A case study Published on March 4, 2021 March 4, 2021 • 29 Likes • 3 Comments
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A kinetic study of the first step in the reaction of phenol and formaldehyde, the formation of ortho‐ and para‐hydroxymethylphenol, is described.. It is found that when using NaOH or KOH as a catalyst under weakly alkaline conditions (pH = 8.5‐10.5) at 30° C, the para‐position in the phenolic nucleus is nearly twice as reactive as the ortho‐position (the ortho/para ratio being 1.10).
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2021-4-21 Phenol formaldehyde resins, as a group, are formed by a step-growth polymerization reaction which may be either acid or base catalysed. The pathway the reaction follows varies depending on the catalyst type used. Acid catalysed. Acid catalysed phenol formaldehyde resins are made with a molar ratio of formaldehyde to phenol of less than one and ...
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2021-4-15 epoxy phenol novolak resin: Phenol, polymer with formaldehyde, glycidyl ether or Epichlorohydrin-formaldehyde-phenol copolymer OR Formaldehyde, oligomeric reaction products with 1-chloro-2,3-epoxypropane and phenol
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2021-1-16 Phenol formaldehyde resins (PF) or phenolic resins are synthetic polymers obtained by the reaction of phenol or substituted phenol with formaldehyde.Used as the basis for Bakelite, PFs were the first commercial synthetic resins (plastics).They have been widely used for the production of molded products including billiard balls, laboratory countertops, and as coatings and adhesives.
Read MoreThe reaction between phenol and formaldehyde in . alkaline solution leads to the introduction of a hydroxy - methyl group into the aromatic nucleus at positions .
Read MoreThe initial phenol-formaldehyde reaction products may be of two types, novolaks and resols. Phenol-formaldehyde reactions catalyzed by zinc acetate as opposed to strong acids have been investigated, but this results in lower yields and requires longer reaction
Read MoreRunway reactions: Phenol–formaldehyde low-temperature runaway reaction: A case study Published on March 4, 2021 March 4, 2021 • 29 Likes • 3 Comments
Read MorePhenol–formaldehyde reaction The phenolic resin is prepared by the reaction of phenol or substituted phenol with an aldehyde such as formaldehyde, in the presence of an acidic or basic catalyst. Phenolic resins are used as adhesives for binding wood-particle boards, fibre boards, plywood, nonwoven textiles and insulation materials, coatings ...
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2013-9-18 Reaction of formaldehyde with both phenol and 2-tertiary bu tyl 4-methyl phenol (TBMP) catalysed by tetraethyl ammonium hydroxide, triethylamine, diethylamine and ethylamine follows an overall second order rate kinetics. Overall rate constant k in phe nol-HCHO reaction is resolved into stepwise rate constant k1 for
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2005-7-26 action of formaldehyde (i.e., methanediol) with phenol. The first was a 4-centered reaction mechanism, illus- trated in Figure 4 for the reaction of methanediol at the para-position of phenol. The second was an Sn2-like re- action mechanism, illustrated in Figure 5. The reaction mechanism necessitates two transition states:
Read More2021-4-21 Phenol formaldehyde resins, as a group, are formed by a step-growth polymerization reaction which may be either acid or base catalysed. The pathway the reaction follows varies depending on the catalyst type used. Acid catalysed. Acid catalysed phenol formaldehyde resins are made with a molar ratio of formaldehyde to phenol of less than one and ...
Read More2009-2-16 The reaction is faster as the media becomes more acidic. c. Due to use of acetic acid, a strong vinegar smell is associated with this experiment. Resole resin 1) Dissolve phenol crystals in formaldehyde (formaldehyde to phenol ~ 1.5 ratio) (4 gm phenol, 6-10 grams phenol formaldehyde) 2) Dissolve NaOH in water (concentrated). Add ~ 10ml.
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2016-2-20 Phenol-formaldehyde reactions are common industrial processes. The reaction of phenol or substituted phenol with an aldehyde, such as formaldehyde, in the presence of an acidic or basic catalyst is used to prepare phenolic resins. Phenolic resins are used in adhesives, coatings, and molding compounds. The type of catalyst used, the ratio of
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2021-1-16 Phenol formaldehyde resins (PF) or phenolic resins are synthetic polymers obtained by the reaction of phenol or substituted phenol with formaldehyde.Used as the basis for Bakelite, PFs were the first commercial synthetic resins (plastics).They have been widely used for the production of molded products including billiard balls, laboratory countertops, and as coatings and adhesives.
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الصين -تشنغ تشو -المنطقة الوطنية للتنمية الصناعية للتكنولوجيا المتطورة، جادة العلوم رقم 169.
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