Novel unfilled polycarbonate diol based elastomeric polyurethane sealants for civil engineering with enhanced damping proberties and improved degradation resistance

 
Adhesives and sealants are often used for filling gaps and control the shrinkage in joints made with concrete, ceramics or metals in construction, building and Civil Engineering. The advantages of using adhesives and sealants in these applications include good outdoor resistance, good behavior under broad temperature fluctuations, good resistance to severe pavement deflection or vibrations due to heavy truck traffic, and reasonable stability against moisture and solvents exposure, among other [1]. Polysiloxane and polyurethane sealants are the most commonly used, although polysulfides and acrylic foam tapes are also used in minor extent [2]. In recent years polyurethane sealants have become more common due to their versatile chemistry. Because of their relatively good resistance to hydrolysis two-component polyurethane sealants formulated with polyether or polyester polyols are used in building and construction [3]. The most commercial polyurethane sealants in the market contain fillers for enhancing the mechanical and rheological properties, among other. Carbon blacks are added for promote slump resistance of the polyurethane sealant. Clays (i.e. kaolin), aluminosilicates, talc or fumed silicas are added for controlling sag in the polyurethane sealants [4]. However, due to its low cost, calcium carbonate is the most common filler used in polyurethane sealants although it can cause moisture sensitivity and reduced resistance to degradation because of its hydrophobicity [5]. Therefore, it is desirable avoid the addition of fillers in polyurethane sealants for reducing cost and improving resistance to degradation. In fact, the resistance of the current polyurethane sealants in the market to oils and solvents is limited and, according to previous studies [6], the use of polycarbonate diol in their formulations could lead to significant improvement of these properties. The polyurethanes prepared with polycarbonate diol show virtual cross-linkings due to hydrogen bond interactions between the urethane and/or urea groups and the C=O group of the carbonate, and, as a consequence, improved mechanical and resistance to ageing can be expected [7]. Furthermore, the carbonate groups in the polyol produce higher number of interactions by hydrogen bond in the polyurethanes than the ether or ester groups because of their higher molar attraction constant [8]. Therefore, in this study, novel polyurethane sealants for Civil Engineering were prepared by using polycarbonate diols of different molecular weights. These polyurethane sealants were intended to avoid the addition of fillers but maintaining or improving their resistance to degradation by prolonged immersion in different chemicals and solvents. The performance of the new polyurethane sealants was compared with that of benchmark polyurethane sealant in the marked.