30 сентября, 2015 
Pokraskin Fillers are fine solid materials that are added to adhesives and are, at best, adhesively bound to the polymer. Generally, they have an inorganic nature, although organic material (e. g. rubber) is used in special cases. The importance offillers is also often underestimated, because they are believed to be used only to reduce the content ofthe costly polymer constituent of the adhesive.
Fillers offer more, however. If their chemical nature is similar to that of the adherents, then both the thermal conductivity and the coefficient of thermal expansion of the adhesive can be adapted to those of the adherents. Fillers in the form of flakes provide for electrical conductivity (see Section 8.7.2). The viscosity and thixotropy of uncured adhesives can also be significantly increased by using special fillers (e. g. Aerosil/silica), at only a very low volumetric content.
Finally, it must be noted that fillers can influence the kinetics of adhesive curing mechanisms and the structure ofthe polymer matrix if they have active surfaces. This is one of the reasons why fillers are also used in adhesives to improve resistance to
heat. The surface characteristics of nanoparticles seem to be primordial for their effect when they are used as fillers. Nanoparticles have a very low volume, but large surfaces, and consequently the addition of minor amounts of nanoparticles has a major effect on the polymer matrix; alternatively, it may induce the formation of domains with different polymer structures within the adhesive layer. An inhomogeneous adhesive layer is an advantage with regards to fracture mechanics, because the inhomogeneities can act as ‘crack stoppers’. Clearly, nanoparticles will undoubtedly play an important role in the future, particularly with regard to impact resistance, which is of utmost importance in the car manufacturing industry.
It has become clear that fillers play a very important role in the formulation of adhesives.
Опубликовано в рубрике 