Qualitative and quantitative evaluation of epoxy systems by Fourier transform infrared spectroscopy and the flexibilizing effect of mercaptans

Epoxy systems are widely applied as adhesives in the aerospace industry. They have excellent adhesion properties, however, being thermosetting, epoxy show fracture brittleness characteristics. Polysulfide and polymercaptans good options to increase flexibility of adhesive. Thermal analysis techniques generally used evaluate curing degree systems. In most cases, when infrared (IR) is used, it employed qualitatively. This paper presents reaction study a DGEBA prepolymer with diethylenetriamine (DETA) linear branched dodecyl mercaptans flexibilizers. Conversion data time were assessed qualitatively quantitatively by Fourier Transform Infrared Spectroscopy (FT-IR) medium region (MIR) near region, using reflectance accessory (NIRA). NIRA methodology showed satisfactory results, errors between 3 7%, especially samples lower amine contents. Mechanical tests confirmed flexibilization cured system addition mercaptans, indicating crosslinking matrix. Young’s modulus (E) significantly decreased from 2017 MPa 578 approximately 20 wt% normal mercaptan system.