a synthetic adhesive based on polyamides. Polyamides are used as adhesives both alone, as liquid resins with various viscosities or in solid form (powders, sticks, films, and fabrics), and in the form of solutions or emulsions in organic solvents or water.
Polyamide adhesives may be thermoplastic or thermosetting. Thermoplastic adhesives are made, for example, from homo-polyamides or copolyamides, whereas thermosetting adhesives are made from methylolpolyamides. Phenol-formaldehyde, epoxy, and coumarone-indene resins, polyacetals, and rubbers, as well as plasticizers and fillers, are added to polyamide adhesives to improve the mechanical and thermophysical properties of the adhesive bond. The compositions are supplied in ready-to-use form or are prepared before use. Liquid and powder polyamide adhesives are applied to the surfaces to be joined using a brush or roller or by spraying. Polyamide films or fabrics are placed between the surfaces to be joined after application of, for example, a solution of phenol-formaldehyde resin. The thermosetting adhesive bonds harden at room temperature, in which case curing agents are used, or upon heating up to 120°–160°C with a slight contact pressure. Hot-melt adhesives (powders or sticks) are applied to preheated surfaces or through special nozzles in which the adhesive is melted by passing through a stream of hot gas. The bond is formed by cooling the layer of adhesive below the melting point of its main components.
Polyamide adhesives have good adhesion to metals, plastics, ceramics, wood, leather, and fabrics. The adhesive bonds are resistant to mechanical loads, including peeling and impact as well as to the action of fuels, oils, and mold. Most of the joints are stable to 80°-100°C, and in some cases to 125°–150°C. Polyamide adhesives are used in the manufacture of machines and instruments, and the hot-melt adhesives are used in the production of packaging materials, as well as in printing.
REFERENCEEntsiklopediia polimerov, vol. 2. Moscow, 1974.
See also References under ADHESIVES.
A. B. DAVYDOV