Degradation of acrylic-melamine based varnish containing Tinuvin 292 with accelerated exposure in fluorescent UV and condensation

Abstract

The durability of an acrylic-melamine (AC-ML) based varnish containing Tinuvin 292 when exposed to 100 cycles of accelerated exposure testing in fluorescent UV and condensation was investigated. Fourier-transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), and scanning electron microscope (SEM) were used to evaluate the changes between the initial and aged coatings. The obtained results showed that gloss loss, adhesion, flexibility, impact resistance, and relative hardness of the AC-ML varnish were enhanced with 2.5 wt.% of Tinuvin 292. FT-IR spectrums of the initial and aged samples without Tinuvin 292 illustrated strong changes in intensity of CH₂ and C=O (ester) groups. AC-ML varnish with 2.5 wt.% of Tinuvin 292 exhibited changes in the peaks of the CH₂ and ester groups after accelerated exposure testing. SEM images showed that the surface of the aged AC-ML varnish without Tinuvin 292 was rougher than that of the coating with Tinuvin 292. TGA results also showed that 2.5 wt.% of Tinuvin 292 had improved thermal oxidation stability of the AC-ML based varnish.