resumo
Ellagic acid (EA) is a plant polyphenol with strong antioxidant properties. The stabilizing effect of EA on the thermo-oxidative degradation of the commercial thermoplastic poly(ester-ether urethane) (TPU) was studied for the first time and compared with effect of kraft lignin (KL), butylated hydroxytoluene (BHT) and pentaerythritol tetrakis (Irganox 1010). TPUs doped with antioxidants (ca. 20,000 ppm), were analysed for their oxidation induction time (OIT) at 200 degrees C and the oxidation onset temperature (OOT). The extent of TPU degradation with and without addition of antioxidants was studied by head space-gas chromatography-mass spectrometry (HS-GC-MS) at 200 degrees C under aerobic atmosphere. The highest stabilizing effect of EA was attributed primarily to its stronger antioxidant capacity when compared to KL and synthetic polyphenolic antioxidants (BHT and Irganox), which was corroborated by antiradical power studies with 2,2-diphenyl-1-picrylhydrazyl (DPPH). The analysis of the volatile products released under thermo-oxidative degradation showed the suppressive effect of EA on the thermally induced depolymerization of TPU occurring via homolysis. Furthermore, it has also been proposed that EA affects TPU degradation with the cleavage of urethane bonds in carbamates due to eventual coordination with the intermediate cyclic intramolecular transition complex involved in thermally induced depolymerization. Further studies in this area can prompt the performance improvements of TPU products, allowing them to be used in a wider range of durable goods applications.
palavras-chave
NATURAL ANTIOXIDANTS; THERMAL-DEGRADATION; MECHANISMS; POLYMERS; PHENOLS
categoria
Polymer Science
autores
Gama, N; Evtyugin, DD; Lourenco, A; Lopes, C; Evtuguin, D
nossos autores
Dmitry Dmitrievitch Evtyugin
Estudante de doutoramento
Dmitry Evtyugin
Professor Associado com Agregaçãoagradecimentos
This work supported by CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020 and CEF, UIDB/00239/2020, financed by national funds through the Portuguese Foundation for Science and Technology/MCTES. Dr. Ana Lourenco was also supported by FCT through a research contract (DL 57/2016/CP1382/CT0007).