Formaldehyde polycondensation with

The Hock process includes the oxidation of cumene by air to hydroperoxides using large bubble columns and the cleavage of the hydroperoxide via acid catalysis, which is reaction [OS 82]. This process is used for the majority of world-wide phenol production and, as a secondary product, also produces large quantities of acetone [64]. Phenol is used, e.g., for large-scale polymer production when reacted in a polycondensation with formaldehyde. 

Conditions to be met in oven drying enamels depend also on the composition of the binder. Paint systems containing melamine-formaldehyde or urea-formaldehyde resins, for instance, harden by polycondensation with other resins, such as epoxy resins, short-oil alkyd or acrylic resins at elevated temperatures. Baking is carried out at temperatures between 100 and almost 200°C and may last from a few minutes to more than an horn. A general trend towards energy conservation has shifted public attention towards binders which require low baking temperatures. 

The unextractable acid in wood plays a major role in the catalysis of the urea-formaldehyde polycondensation reaction. The significance of this indication must be viewed in contrast to previous investigations which have attempted to correlate properties of wood with the properties or amounts of extractives. It would not be prudent to generalize regarding the effect of unextracted acids because only seven species were studied. However, in future studies these observations may be found to be generally true for most, if not all, species. 

The first membranes made by this procedure were prepared from phenol by polycondensation with formaldehyde according to the following reaction scheme 82... 

Figure 2.21 shows the heat flow development of cement pastes without and with 0.3% of superplasticiser in simultaneous and in delayed addition mode (Winnefeld 2008). Products based on polycarboxylate ether (PCE) and sulfonated naphthalene-formaldehyde polycondensate (SNF) were applied. Compared to the plain paste, the pastes with admixtures show a retardation of the setting and a delay of the main hydration peak. In... 

Tubular reactors are used for some polycondensations. Para-blocked phenols can be reacted with formalin to form linear oligomers. When the same reactor is used with ordinary phenol, plugging will occur if the tube diameter is above a critical size, even though the reaction stoichiometry is outside the region that causes gelation in a batch reactor. Polymer chains at the wall continue to receive formaldehyde by diffusion from the center of the tube and can crosslink. Local stoichiometry is not preserved when the reactants have different diffusion coefficients. See Section 2.8. 

Pekala RW. Organic aerogels from the polycondensation of resorcinol with formaldehyde J. Mat. Sci. 1989 3221-7. 

Tamon H, Ishizaka H, Mikami M, Okazaki M. Porous structure of organic and carbone aerogels synthesized by sol-gel polycondensation of resorcinol with formaldehyde. Carbon 1997 35 791-6... 

These are produced by the polycondensation of a phenol or a mixture of phenol with formaldehyde. This condensation reaction is catalysed by acids or alkalies. The nature of the product formed by this condensation reactions depends upon the type of catalyst and the mole ratio of the reactants. 

Thermosets are formed by crosslinking (curing) of reactive linear and branched macromolecules and can be manufactured by polycondensation, polymerization and polyaddition. Thermosets can therefore be processed once only with the application of heat and pressure to form semi-finished products or finished articles and cannot be recovered their processing is irreversible. Amongst the most familiar thermosets are the combinations of formaldehyde with phenol, resorcinol etc. (phenolics), urea, aniline, melamine and similar combinations (aminoplastics). 

Special type of template polycondensation product was obtained by Papisov at al Polycondensation of urea with formaldehyde in the presence of polyCacrylic acid) gives polycomplexes or polycomplex composites with various structures and properties. The... 

First step (a) represents the initial system - solution of the poly(acrylic acid) (urea and formaldehyde are not shown). Then, growing macromolecules of urea-formaldehyde polymer recognize matrix molecules and associate with them forming polycomplex. This process leads to physical network formation and gelation of the system (step b). Further process is accompanied by polycomplex formation to the total saturation of the template molecules by the urea-formaldehyde polymer (step c). Chemical crosslinking makes the polycomplex insoluble and non-separable into the components. In the final step (c), fibrilar structure can be formed by further polycondensation of excess of urea and formaldehyde. 

Another example of the use of deoxidation of oxygen-containing compounds for their structural analysis was given by Wi jnands et al.68, who investigated the structure of novolaks, prepared by polycondensation of formaldehyde with phenol, />-cresol and w-cresol. The novolaks were transformed into saturated hydrocarbon mixtures by direct hydrogenation. Ultimate analysis of the hydrocarbons confirmed the linear structure of the novolaks ... 

The influence exerted by the matrix on the direction of the elementary growth steps of the daughter chains was observed for the matrix polymerization of 4PV on polyacids when the daughter P4VP had ionene structure 81), and for the matrix polycondensation of urea and formaldehyde in water, with PAA being present 88,89). In the latter case, the daughter chains of PFU contained the structures... 

Homogeneous IEM are produced either by polymerization of functional monomers (e.g., polycondensation of phenol or phenol-sulphonic acid with formaldehyde) or by functionalization of a polymer film by sulphonation of a polystyrene film. 

---