Diffusion-Controlled Oxidative Degradation of Isotactic Polystyrene at Elevated Temperatures. I. Experimental Procedure and Results

Abstract

The utility of energy transfer processes for the stabilization of polymers will depend to a large extent on the lifetime of the excited states involved. In the present instance involving aliphatic carbonyl groups, the excited state lifetimes, t, are so short that excessive concentrations of the stabilizer molecules would be required to obtain an economically desirable effect. However, other polymers, particularly those containing phenyl groups, might be expected to have longer lifetimes and hence would be easier to stabilize by this mechanism. In view of this, the study of energy transfer processes in other polymers may well lead to important advances in the development of stabilizer systems.

Thermooxidation rate of diacetate terminated polyoxymethylene with various morphological structures

“…The rate of molecular chain scission (correlated with the rate of main weight loss) is proportional, according to the accepted reaction mechanism, to the concentration of oxygen in the sample and is 3 times faster for sample I than for sample 5. This is related to the fact that thermooxidation occurs mainly in the amorphous phase of semicrystalline polymers but oxygen solubility and path for diffusing oxygen molecules depend also on the morphological structure of the polymers, such as spherulite size [20][21][22][23].…”

Temperature Limit of Inhibition of Thermo- oxidative Degradation of Polystyrene and Poly(methyl methacrylate) by Antioxidants

“…As mentioned above, the value of To for PMMA is 55°C higher. It seems to be generally agreed that in the case of PS, initiation of the oxidative process is due to abstraction of hydrogen atoms near the tertiary carbon atoms [7, 81. In the papers [7,8] the thermo-oxidative aging of PS over a temperature range from 249°C to 300°C has been studied. It has been shown that water is the main volatile product.…”

“…It has been shown that water is the main volatile product. In the thermo-oxidative degradation of PS at elevated temperatures, the mechanism of oxidation of hydrocarbons in the liquid phase is believed to be operative [7,8]. The thermo-oxidative degradation of PMMA has been investigated up to 320°C [9,10].…”

Oxygen uptake by isotactic polypropylene of different morphological structure

“…The oxygen uptake method was applied to study thermooxidation of semicrystalline polymers such as isotactic polypropylene [5], polyethylene [6], poly(4-methyl pentene) [7] and isotactic polystyrene [8]. It is recognized that the oxidation rate is a first order reaction in relation to oxygen pressure [7][8][9] and depends on sample thickness up to its critical value. For thicknesses lower than the critical one, the rate of oxidation does not depend on the oxygen pressure and sample thickness [7,9,10].…”