The main component of composite materials is a binder that under the influence of hardeners or water passes from a liquid or dough to a solid state. For the production of KCM, a large group of inorganic and organic binders is used, chosen by operating conditions and product requirements. The greatest application is found on materials based on cement, gypsum, lime, bitumen and polymer binders. In some areas of construction, composites based on liquid glass, magnesian and sulfuric binders are promising.
The intensification of construction is accompanied by the continuous search for perfect KCM. An example of such a search can serve the work of recent years to improve the properties of concrete with the help of polymers. They are made on polymer binders in a mixture with chemically stable fillers and fillers without the participation of metallic components. By the form of the binder phenol-formaldehyde, furan, polyester, epoxy, urea, polyurethane, acetone-formaldehyde, polymethylmethacrylate, polyethylene and other polymer concrete are distinguished, as well as numerous varieties of composites on modified and combined resins.
Domestic and world practice shows that polymer concrete is often used in construction on epoxy, polyester and urea resins. Of the wide variety of epoxy resins manufactured by our industry, the most famous applications for the production of polymer concrete are epoxy diseases, which are the condensation products of epichlorohydrin with diphenylpropane in an alkaline medium. Depending on the quantitative ratio of the components entering into the polycondensation reaction, epoxy resins with a linear structure and different relative molecular weights are obtained, ranging from 340 to 4290. As this index increases, their viscosity increases and the reactivity decreases.
The conversion of solid epoxy resins to a liquid state is carried out with solvents or elevated temperatures. In the technology of polymer concrete, the use of solid epoxy resins is not efficient, since in one case the enzymes lower the density of the composites, while in the other, high temperatures are required – about 50-155 ° C, depending on the relative molecular weight of the resin. From this point of view, liquid resins of ED-16, ED-20, ED-22 and their compounds with rubbers, furan, and other resins are more suitable. The transition of epoxy resins to the non-melting and insoluble state is carried out under the action of hardeners, which facilitate the connection of linear resin molecules to the spatial formations in place of epoxy and hydroxyl groups. Curing is carried out with the help of ion-type catalysts (tertiary amines, piperidine, dimethylaminomethlphenol, antimony chloride, fluoride or other compounds) or crosslinking reagents (polyethylene polyamines, ethylenediamine, m-phenylene diamine, methylenedianiline, p-xylidenediamine, etc.). For the cold curing of epoxy resins, polyethylene polyamine, hexamethylenediamine, hexomethylenediamine bottoms remain predominantly used. In the manufacture of polymer concrete products in conditions of 100% humidity and under water, the aminophenol hardener AF-2 and aminoplast ASF-10 are preferred.