Analysis of non-load bearing, 2 component epoxy-adhesive to the hemming process variations; Thermo-Gravimetric, Differential Scanning Calorimetry, and Fourier Transform Infrared Spectroscopy FT-IR analyses

This manuscript investigates the impact of automotive hemming-process variations on a 2K (2 component) non-load bearing adhesive. The investigated variations include the resin and the hardener mixing quality and ratio, the storage conditions prior to final curing, and the curing profile for Electro-Coat ovens. A Thermo-Gravimetric Analysis (TGA) provides information about the volatile evaporation percentiles in the final curing chamber, while a Fourier Transform Infrared Spectroscopy (FT-IR) is used to analyze the adhesive chemical groups mainly the hydroxyl and the epoxy groups. Additionally, this work validates the use of a Differential Scanning Calorimetry (DSC) procedure to determine such variations' impact on the glass transition T_g temperature, also on the thermo-set cure rate for different holding times. Results show that the 2K adhesive volatile content is sensitive to the curing profile (ramp-up rates) and to the holding-time variations; however the adhesive composition is insensitive to the holding-conditions, mainly the relative humidity.