Analysis of deteriorated rubber-based pressure sensitive adhesive by pyrolysis-gas chromatography/mass spectrometry and attenuated total reflectance Fourier transform infrared spectrometry

Rubber-based pressure sensitive adhesives of three packing tapes were exposed to sunlight for 6 months to accelerate the oxidation of the adhesives. The exposed adhesives and the unexposed adhesives were analyzed by attenuated total reflectance Fourier transform infrared spectrometry (ATR/FT-IR) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The ATR/FT-IR spectra and the pyrograms changed drastically after the exposure. The pyrolyzate peaks of elastomers and an aliphatic petroleum resin disappeared from the pyrograms of the exposed adhesives, while those of a coumarone resin and a β-pinene resin were still detected. One of the adhesives in which rosin-glycerin ester was used as a tackifier was also analyzed by thermally assisted hydrolysis and methylation (THM) GC/MS using tertramethylammonium hydroxide (TMAH). Methyl dehydroabietate, methyl levulinate, dimethyl succinate and methyl benzoate were identified in the THM products of the exposed adhesive, while methyl abietate was not detected. Aromatic constituents showed higher resistance to oxidation than the unsaturated ones.