Evaluation of sealands using infrared spectroscopy

Abstract

High performance sealants are widely used in joints of curtain walling on building facades. Although highly polymeric, these sealants are susceptible to degradation due to environmental factors such as ultraviolet, moisture, heat and others. The most important property being the mechanical elastic recovery. The degradation under various accelerated weathering conditions of one and two part polyurethane, one and two part polysulphide was studied using Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy. Sealants were cast in a rectangular aluminium mould and cured under ambient conditions. The sealants were then exposed to four accelerated weathering conditions, namely weatherometer (QUV), oven aging at 70°C, water-immersion at 25°C and 70°C. FTIR spectra and elastic recovery were taken at a time up to 35 days. The results show considerable degradation and reduction in elastic recovery after weathering. For polyurethane (one and two parts), the FTIR spectra show that the degradation of sealant as indicated by the reduction of elastic recovery could be due to hydrolysis of urethane linkage and chain degradation. On the other hand, polysulphide (one and two parts) degraded extensively with the formation of epoxy ring and broadening of CH 2 deformation band indicating chain degradation.