Modifications of Epoxy Resins and their Influence on their Viscosity

Abstract

The material engineering of composites is currently one of the fastest growing fields of the technology. Research in this discipline currently focuses on two basic directions: a search for completely new materials and methods of modifying the properties of already known materials. Among the study belonging to the second group, research on the properties and modifications of polymers is a particularly dynamically developing field. Commonly, the most often used polymer types in construction engineering are: construction, coating, and adhesive polymers. The last group includes the so-called resins, e.g., epoxy, phenol, polyester, formaldehyde, and mixtures of these polymers. Their use is focused at combining construction materials, i.e. to strengthen structural elements. Their hardening process can be caused by two factors – the hardener (chemohardening polymers) or higher temperature (thermohardening polymers). These processes cause its cross-linking, i.e. the production of a crystallized resin structure to a permanent form. The conditions in which the resin was prepared have a big impact on its adhesion to the substrate during its application on the glued surfaces (early resin adhesion). This parameter largely depends on two important factors: the chemical composition of the resin and its viscosity. Changes of viscosity can have a measurable effect on the final effect of gluing. The following elaboration includes the results of modification tests of an epoxy resin with the addition of two inorganic fillers: microsilica (in the amount of 0.5% of resin weight) and carbon nanotubes (in the amount of 0.1% of resin mass). The epoxy resin commonly used in engineering for joining steel, concrete, carbon fiber, and glass elements was used. In addition, the ultrasound energy was used as a factor, which disintegrated the initial structure of the resin in liquid form and allowed the efficient mixingofthe resin with the filler. The influence of sonication and filler additives on the viscosity of the resin at temperature of 22 °C was determined. Based on the results obtained and observation of the ultrasound effect, the phenomena occurring at the interface of the liquid phase of the resin and the phase of individual fillers were explained. The increase of temperature of the resin under the influence of a dynamic action occurring during sonication was taken into account. The study conducted was the preliminary phase before investigating the influence of the modifications applied on the physical and mechanical parameters of the hardened resin.