Studies of the Thermal Stability and Degradation Mechanisms of Acrylic Acid Polymers and Ionomers

This research is concerned with the preparation, characterisation and thermal degradation of acrylic acid based polymers and copolymers. The alkali (Na and K), alkaline earth (Mg and Ca) and some transition metal salts (Zn and Co) of acrylic acid monomer and polymers together with the copolymers of styrene-acrylic acid and their sodium and potassium salts were prepared, characterised and their thermal behaviour were also studied under programmed and isothermal heating experiments using TVA, TG and DTA techniques. Degradation products were identified by spectroscopy, mass spectrometry, GC and GC-MS techniques. A brief discussion about ionic polymers including ionomers and polyelectrolytes is presented in Chapter One. This chapter also reviews briefly the definition and classification of polymer degradation. Chapter Two presents an introduction to the thermal analysis techniques mostly employed in this work, with emphasis on the thermal volatilisation analysis as a more sophisticated technique. The techniques which were used to identify the degradation products are briefly described. The preparation, characterisation and polymerisation of monomers, polymers and copolymers are explained in detail in Chapter Three. The thermal degradation of poly(acrylic acid) samples (lab-prepared and commercial sample) is the subject of Chapter Four. Programmed and isothermal heating experiments were employed to investigate the thermal behaviour of these materials. It is found that the thermal degradation of PAA commences with a dehydration reaction occurring by intramolecular cyclisation of adjacent monomer units to give six-membered anhydride ring structures. Decarboxylation becomes important under programmed heating conditions at about 25