A Study of the Thermal Degradation of Several Halogen-containing Polymers by Torsional Braid Analysis

Abstract

Abstract The thermal degradation of several halogen-containing polymers in air was studied by means of the TBA(Torsional Braid Analysis) method and IR spectroscopy. The samples were poly(vinyl chloride)(PVC), vinylidene chloride-vinyl chloride copolymer(PVdC-VC), poly(vinyl fluoride)(PVF), poly(vinylidene fluoride)(PVdF), poly(vinyl bromide)(PVB), and poly (vinylidene bromide)(PVdB). The dynamic mechanical properties of these polymers are complicated at higher temperatures because of the thermal degradation, by, for example, dehydrohalogenation. The relative shear modulus (Gr) increases and then decreases through a maximum, accompanied by changes in the logarithmic decrement. The temperatures at which the changes in Gr occur become higher in the order of PVdB<PVB<PVdC-VC<PVC<PVdF<PVF. This order agrees with that of the bond energy in carbon-halogen bonds. The apparent activation energies of these reactions were obtained from the changes in Gr and from the relative absorbance ratio of the carbon-carbon double bond with time, respectively. In general, the values estimated by these two procedures agreed well in each case.