Лако-красочные материалы — производство

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 in application areas that require a nonsagging bead. Calcium carbonates, clays, and talcs are used to improve the economics of an adhesive formulation. A major concern using fillers with urethane prepolymers is the moisture content associated with the fillers. Fillers typically must be dried prior to use with urethane prepolymers or isocyanates. Hygroscopic fillers should be avoided, as moisture introduced by the filler can lead to poor shelf stability of the finished product.

Pigments are sometimes used in polyurethane adhesive systems, but since most adhesives are generally hidden from view, pigments do not play major roles. Pigments may be used to color the adhesive to match the substrate. Pigments are more typically used to color one side of a two-component system to help the user distinguish between the isocyanate and the polyol. They are also sometimes used as an aid to judge mix ratios. Carbon black and titanium dioxide are two commonly used pigments.

Plasticizers can also be used in polyurethane adhesives to lower viscosity, improve filler loadings, improve low-temperature performance, and plasticize the polyurethane adhesive. Phthalate esters, benzoate esters, phosphates, and aromatic oils are common examples [48]. Plasticizers should be used sparingly, as adhesion will generally decrease as levels increase.