furan resin[′fyu̇r‚an ‚rez·ən]
any of a series of oligomeric products prepared from compounds containing a furan ring that are capable, on heating or in the presence of catalysts, of converting into cross-linked polymers. The most important resins are obtained from furfuryl alcohol and from the products of the interaction of furfu-ryl alcohol with furfural (furfuryl furfural) and furfural with acetone. The last two, given an alkaline medium and a molar ratio of 1:1, form the monomer FA, which is mainly a mixture of mono-furfurylidene (50–65 percent) and difurfurylidene acetone (40–25 percent). Furan resins are generally formed during the preparation of compound materials from the indicated products. All resins harden slightly upon heating; the process is accelerated in the presence of acid catalysts, especially aromatic sulfo acids and mineral acids.
The hardening products are known for their high resistance to heat, acids, and alkalies, as well as their high coking values (85–90 percent). The monomer FA is used as a binder in the manufacture of polymer concrete and polymer mortars, which, unlike concrete, contain finely dispersed powders (sand, powdered andésite combined with carbon-graphite powder) as a filler. The mortars have higher mechanical strength, plasticity, and corrosion resistance and lower friability than polymer concrete; they are used to protect concrete building structural members in chemical plants and as refractory lining for chemical equipment, especially equipment used in the pulp and paper industry. Furfuryl alcohol polymers are used as binders in the manufacture of glass plastics, which are known for their extremely high resistance to alkalies and heat; furfurylfurfural resin, which contains benzenesulfonic acid as a hardening agent, is used as a binder for cold-hardened glass plastics. Furan resins are also used as binders in molded materials containing asbestos fiber and graphite.
G. M. TSEITLIN