Study on thermal degradation of poly (1,4 phenylene terephthalamide) and its volatile products by unadorned setup of Pyrolysis and subsequent UV–VIS spectroscopy

Abstract

Pyrolysis involves the elimination of moisture and volatile components from fibrous materials by cleavage of molecular bonds to finally obtain carbon-rich residues. Over the years, there have been numerous studies on the pyrolysis of poly (1,4 phenylene terephthalamide) (Kevlar) and characterization of volatile products by using various analytical techniques. The main objectives of this work were to exhibit a simple and straightforward pyrolysis method using a smelting furnace, concurrently condensing the volatile products on a cold surface, followed by acquiring information on progressive changes in concentrations of decomposition products and their difference in volatility using UV-Vis spectroscopy, and to subsequently demonstrate an interesting algorithm for separation of mixture spectra. Variations in concentration of major elements (C, N, S, and O) were also monitored as a function of pyrolysis temperature. An increase in the concentration of volatile products was observed above 500 °C, reaching maximum at 700 °C and then progressively decreases towards the final temperature of 1100 °C. Separation of mixture spectra was attempted using the concept of spectral matrix decomposition to decompose measured spectra into possible spectra of individual components with the objective of proposing a fast and inexpensive method coupled with computational aid that contributes to kinetic studies of pyrolytic processes.