THERMAL-STABILITY AND DEGRADATION MECHANISMS OF POLY(ACRYLIC ACID) AND ITS SALTS .2. SODIUM AND POTASSIUM-SALTS

The polymers of the sodium and potassium salts of acrylic acid have been prepared by free radical polymerisation of the respective monomers in methanol solution. Both polyacrylate salts were also synthesised by neutralisation of the appropriate metal hydroxide solutions in methanol by addition of a solution of poly(acrylic acid) in the same medium. The degradation of sodium and potassium polyacrylate was studied under programmed heating conditions using thermogravimetry (TG), differential thermal analysis (DTA) and thermal volatilisation analysis (TVA). These materials are stable up to about 400°C under programmed heating at 10° per min in vacuo. The degradation products have been investigated by IR spectroscopy, mass spectrometry and GC-MS techniques, the volatile product fraction having first been separated by subambient TVA. Degradation of these polymers leads to a wide range of products, which include dimer and trimer fragments but only traces of monomer. A mechanism has been proposed which involves both homolysis of the chain, which may be followed by intramolecular transfer and scission, and side group scission. © 1990.