Abstract
In this thesis, efficient additives have been investigated to improve thermal stability of thermoplastic polyether-ester elastomer (TPEE). Butylated butylated hydroxytoluene (BHT), 2,6-di-tert-butyl-4-methylphenol (antioxidant 1010), butylated hydroxyanisole (BHA), tert-butylhydroxyquinone (TBHQ), propyl gallate (PrG), 4-hydroxybenzoic acid, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1076), tris(2,4-ditert-butylphenyl) phosphite (antioxidant 168), 4,4’-bis(α,α-dimethylbenzyl)diphenylamine (NG 445), 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene (antioxidant 330), N,N-hexane-1,6-dihylbis[3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide)] (antioxidant 1098), 4-[4-bis(2,4-ditert-butylphenoxy)phosphanylphenyl]phenyl]-bis(2,4-ditert-butylphenoxy)phosphane (PEPQ), pentaerythritol tetrakis (β-laurylthiopropionate) (412S) and 2,2'-methylenebis(4,6-di-tert-butyl-phenyl)-2-ethylhexyl phosphite (HP10) were selected as additives. TPEE pellets were dissolved in chloroform at 78 °C, and then 1wt% of these additives were added to the solution. The solutions were dried to produce testing films under ambient conditions. All of the TPEE’s testing films were systematically characterized and analyzed by UV-vis absorption spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy (XPS), and universal tensile testing. In the UV-vis absorption spectra, TPEEs with additives of antioxidant 1010 showed the best thermal stability. It showed less color change and the lowest absorbance at 400 nm compared with other samples after heating at 140 °C for 7 days. Mixture of antioxidant 1010 and BHT showed great performance on UV-vis absorption spectra, but not as good as antioxidant 1010 alone. In the TGA and DSC results, TPEE with additive antioxidant 1010 and NG 445 showed the highest decomposition temperature among all the additives. This is higher than the pure TPEE. Besides all the samples have similar melting point between 208 °C to 210 °C. In the X-ray photoelectron spectroscopy (XPS) analysis, bond cleavage was observed in C 1s spectra after heating at 140 °C for 7 days, and TPEE with antioxidant 1010 showed less peak change on 289.0 eV. This result suggests that the antioxidant 1010 can retard the bond cleavage. In the tensile tests, it was shown that TPEE with the additive NG 445 has a relatively high retention ratio of tensile strength (around 73%). TPEE with the mixture of NG 445 and antioxidant 1098 showed the best retention ratio (around 75%) after heating at 140°C for 7 days.