Лако-красочные материалы — производство

The UF adhesives for plywood generally contain less than 2 mole of formaldehyde per mole of urea, and most of them are condensed to a slightly viscous, hydrophilic stage and are quite soluble in water. The degree of polymerization, and hence the viscosity under comparable conditions of UF resins for plywood is generally higher than […]

It is very important in the commercial production of UF resins to be able to control the size of the molecules by the condensation reaction, since their properties change continuously as they grow larger. The most perceptible change is the increase in viscosity. Low-viscosity syrups are formed first. These change into high-viscosity syrups, which are […]

The reaction between urea and formaldehyde is complex. The combination of these two chemical compounds results in both linear and branched polymers, as well as tridimen­sional networks, in the cured resin. This is due to a functionality of 4 in urea (due to the presence of four replaceable hydrogen atoms) (in reality urea is only […]

A. Pizzi Ecole Nationale Superieure des Technologies et Industries du Bois, Universite de Nancy I, Epinal, France I. INTRODUCTION The urea-formaldehydes (UFs) are the most important and most used class of amino resin adhesives. Amino resins are polymeric condensation products of the reaction of aldehydes with compounds carrying aminic or amidic groups. Formaldehyde is by […]

From the above survey, it appears that the industrial use of furanic monomers such as furfuryl alcohol and furfural, i. e., chemicals based on renewable resources, as binders in foundry molds is highly successful. Similar furan-based resins can also be used as efficient adhesives in wood-particle composites and thus are interesting alternatives to petroleum-based counterparts. […]

Corrosion-resistant glass fiber reinforced composites were also produced on the basis of furfuryl alcohol thermosetting resins [3,16,60]. Thus, many furan-based glass fiber reinforced materials have been available for many years, particularly for the storage of chlorinated aromatic and aliphatic hydrocarbon solvents. Amongst the commercial units available one finds: (i) very large scrubbing towers packed with […]

Furan resins have also been extensively used in formulating mortars, grouts, and ‘‘setting beds’’ for brick lining destined to be exposed to highly corrosive environments, such as concentrated acids or highly alkaline cleaning solutions [3,16,60-62]. Two techniques are used in order to realize assemblies, namely tilesetter’s and bricklayer’s methods. The first method is based on […]

Regardless of the fact that numerous investigations exist about the possibility of incorpo­rating the furan heterocycle into wood adhesive formulations, their industrial exploitation is still modest. The first suggestion concerning the use of 1 in partial substitution of formaldehyde in phenolic resins was put forward in 1958 by Baxter and Redfern [18] who proposed that […]

Furan resins have been extensively used as foundry binders in combination with formaldehyde, urea, phenol, and casein, for decades [12,13]. The main two monomers used in this field are 1 and 2. Table 3 summarizes their proportions in different commercial phenolic resins [12]. The main advantages of furan resins are due to their excellent thermal […]

The acid — or heat-initiated cross-linking mechanisms of 1 were extensively studied for decades, but because of the complexity of the reactions involved and the effect of atmospheric conditions (e. g., light, oxygen, and water vapor) intermediate products were not identified until 1975. In that study, 1 was polymerized at 100-250°C in the absence of […]