Thermal degradation behavior of polyamide 6/clay nanocomposites

Abstract

This paper focuses on the study of thermal degradation and evolved gas analysis using thermogravimetric analysis (TGA) coupled to Fourier transform infrared (FTIR) spectroscopy, i.e., TG-IR, to study polyamide 6 (PA6) and PA6-clay nanocomposites prepared by melt compounding. The thermal decomposition of PA6 and its clay nanocomposites takes place with the evolution of the cyclic monomer (caprolactam) first, followed by other volatile gases like CO2 and NH3, which are characterized by the presence of oligomeric products with nitrile and vinyl chain ends in the infrared (IR) spectra. The onset temperature for degradation is 12 °C higher for PA6 with 2.5 wt.% of clay loading than that for neat PA6, whereas, the onset temperature for degradation remained almost unchanged for samples with higher clay loading (i.e. 5, 7.5 and 10 wt.% clay). The above findings are related to the morphological observations that show an optimal exfoliated structure only for the nanocomposite with 2.5 wt.% clay, and distinct clay agglomeration in those with higher clay loadings. Our study suggests that only exfoliated polymer/clay nanocomposites exhibit improved thermal stability. Agglomerated clay particles do not significantly affect thermal stability of the polymer matrix. The activation energies for degradation, Ea, estimated by Kissinger method, for PA6 and PA6-2.5 wt.% clay nanocomposite were found to be 175 and 199 kJ/mol in N2, and 228 and 223 kJ/mol in air, respectively. © 2003 Elsevier Science Ltd. All rights reserved.