Thermal Oxidation of Polypropylene and Modified Polypropylene - Structure Effects

Abstract

Ageing and stabilization polymers is a major part of materials science. Aging of polymers defined as a set of chemical and physical transformations, leads to the loss of their set the desired properties. The main role in these transformations belong to chemical processes of degradation and crosslinking of macromolecules. Processes decomposition and structuring polymer conjugates include radical chain, ionic and molecular reactions. Traditionally, the distinction is made between thermal, thermal-, photo-and radiation-chemical aging. Thermal oxidation and thermal-oxidative destruction are the most common and important processes in which polymer materials participate. It accompanies the posed for chemistsexperimenters and producers engaged in polymer materials creation is the problem of maintenance of high quality of output, prolongation of its service life at conditions of thermal oxidation influence and thermal-oxidative destruction. Thermal oxidation of polymers leads to a modification and functionalization of the polymer chains. At the same time thermal oxidation is accompanied by the destruction of bonds in the macromolecules and influence the destructive processes. Thermal oxidation of polymers a radical chain process with degenerate branching of kinetic chains of oxidation. The structure of polymer significantly influences on chain oxidation and destructive processes. Heterogeneity of polymers structures, the presence of regions differing in amplitudes of molecular motions, decrease of segment mobility, reduction of oxygen diffusion coefficient underlie this effect. These factors change kinetics and mechanism of process. As new methods and polymeric materials, researchers returned to the discussion of the induction period of oxidation of polymers. However, often in the literature there is confusion in the very concept and definition of the period induction. For example, when studying the thermal oxidative degradation of PP with different tacticity by thermogravimetric analysis (Chan J.H., Balke S.T., 1997; Nakatani H. and al., 2005) determine the induction period as a time corresponding to the onset of weight loss. I.e in fact, the period induction regarded not as the beginning of oxidation in infancy kinetic chain, and the time corresponding to the branching of kinetic chains in the collapse of hydroperoxide. This is a fundamental difference, so it is important this issue be considered. Often thermal-oxidative degradation is identified with the thermal oxidation. However, in depending on the nature of the polymer,