Лако-красочные материалы — производство

A. Hybrid Adhesives Over the last four decades there have been a number of attempts to wed the unique benefits of polyurethane adhesives with the benefits of other adhesive systems. These attempts have led to the reporting of a variety of urethane hybrids. Early work focused on simple blends; for example, in 1964 Union Carbide […]

The second major classification of common polyurethane adhesives is the two-component system. Two-component polyurethane adhesives are widely used where fast cure speeds are critical, as on OEM (original equipment manufacturers) assembly lines that require quick fixture of parts, especially at ambient or low bake temperatures. Two-component urethanes are required in laminating applications where no substrate […]

Proper surface preparation is the key to obtaining good adhesive bonds having a predict­able service life. Substrate surfaces may have dirt, grease, mold-release agents, processing additives, plasticizers, protective oils, oxide scales, and other contaminants that will form a weak boundary layer. When the adhesive fails it is usually through this region, giving a low-strength bond. […]

Fillers are used in adhesives to improve physical properties, to control rheology, and to lower cost. The most common polyurethane fillers are calcium carbonate, talc, silica, clay, and carbon black. A more rigorous treatment of this subject can be found in Katz and Milewski [47]. Fumed silicas and carbon blacks are used primarily as thixotropes […]

Polyether polyols are generally considered to be low in toxicity with respect to eye and skin irritation; however, amine-initiated polyether polyols have been found to be more irritat­ing to the skin and eyes. The manufacturer’s material safety data sheet (MSDS) should always be consulted before use. Oral toxicity is generally a secondary concern in an […]

Toluene diisocyanate (TDI) is a colorless, volatile, low-viscosity liquid commonly used in the adhesives area to manufacture low-viscosity prepolymers for flexible substrates. The structure of TDI is shown in Fig. 18. TDI is typically supplied as an 80:20 mixture of the 2,4 and 2,6 isomers, respectively, with two grades of acidity available. Type I TDI […]

Polyols for adhesive applications can be generally broken down into three main categories: (1) polyether polyols, (2) polyester polyols, and (3) and polyols based on polybutadiene. Polyether polyols are the most widely used polyols in urethane adhesives because of their combination of performance and economics. They are typically made from the ring­opening polymerization of ethylene, […]

Most urethane adhesives are based on urethane prepolymers. A prepolymer is made by reacting an excess of diisocyanate with a polyol to yield an isocyanate-terminated urethane as shown in Fig. 11. Prepolymers may have excess isocyanate present (“quasi­prepolymers”) or they may be made in a 2:1 stoichiometric ratio to minimize the amount of free isocyanate […]

One of the advantages that a formulator has using a polyurethane adhesive is the ability to tailor the adhesive properties to match the substrate. Flexible substrates such as rubber or plastic are obvious matches for polyurethane adhesives because a tough elastomeric pro­duct can easily be produced. Polyurethanes derive much of their toughness from their morphology. […]

As noted previously, strong or weak bases that are sometimes present in the polyols will catalyze the urethane reaction. The effect of catalysts on the isocyanate reaction is well documented. Indeed, the first reported examples occur in the literature well before urethanes became a commercially significant class of compounds. The first use of a catalyst […]