Лако-красочные материалы — производство

The most widely used polyols employed in polyurethane adhesives are mainly polyether polyols and polyester polyols. The synthesis of polyether polyols takes place via a ring-opening polymerization of ethylene, propylene or butylene oxides, respectively, with an initiator in the presence of a strong base. Polyether polyols can be obtained with different functionalities, molecular weights and […]

Both, aromatic and aliphatic isocyanates, are used for the synthesis of polyurethanes. The most popular aromatic isocyanates are 2,4-toluene diisocyanate (TDI; an isomeric mixture of 2,4- and 2,6-toluene diisocyanate at an isomer ratio of 80 : 20 or 65 : 35), 4,4-methylene dip(henyl isocyanate) (MDI), and the oligomeric form of MDI, a phosgenized aniline formaldehyde […]

5.6.1 Chemistry of Polyurethanes As the chemistry and reactivity of isocyanates are described in detail in several textbooks of organic chemistry, only those reactions relevant to polyurethane adhesives will be detailed in the following sections. The reactivity of isocyanates is based essentially on the electrophilic character of the carbon atom in the cumulated double-bond system […]

A typical impact toughness-modified, one-part epoxy resin adhesive consists of 45% epoxy base resin, 17.5% crosslinking agent (e. g. novolac resin), 27.5% additive to improve the impact toughness, 2.5% pyrogenic silicic acid as rheology additive, 5.5% hardener (e. g. dicyandiamide), and 2% accelerator (e. g. a urea derivative). The typical parts A and B of […]

The build-up ofadhesive forces towards certain substrates can be improved by using further additives, such as functional silanes. Anticorrosive agents are used to improve the corrosion characteristics, and small amounts of glass beads with defined diameter are used to generate a minimum bond-line thickness. By regulating the density, the glass bubbles ensure that the components […]

Chalk, aluminum oxide, silicates and kaolin are used as fillers to reduce costs and shrinkage during the curing process. Pyrogenic or precipitated silicic acids or bentonites allow the flow characteristics of epoxy resins to be regulated.

Flexibility may be improved by using amine compounds as hardeners. Flexibilization and an increase in impact toughness are also obtained by incorporating suitable polymers on the epoxy resin side. Whilst flexibilizers are incorporated into the epoxy matrix and decrease the Tg-values, polymer modifiers that improve impact toughness are in solution with the epoxy resin from […]

Epoxy resin adhesives are cured with primary or secondary diamines. Epoxy-amine adducts are produced by the reaction of bis-phenol-A diglycidyl ether with a six — to eightfold molar excess of diamine. One-part systems are generally cured with dicyandiamide. A flexibilizing effect is obtained using longer-chain diamines such as polypropylene glycol diamine, amino terminated acrylonitrile-butadiene copolymers […]

Higher-functional resins, such as phenol or kresol novolaks, are used to increase the crosslinking density. Higher-functional epoxy resins may also be incorporated, such as tetra-functional N, N’-tetraglycidyl-4,4′-diaminodiphenylmethane. The crosslink­ing rate may also be increased by the addition of higher-functional hardener — components such as tetraethylene pentamine.

Epoxy resin adhesives are composed of an epoxy resin and a hardener. In order to generate a high-performance adhesive, ten or more additives are included in the formulation; these additives must be carefully adjusted to each other because of their mutual interactions. 5.5.4.1 Epoxy Resins The primary epoxy resins used are bis-phenol-A diglycidyl ether (BDGE) […]