Chemiluminescence, in polymer oxidation

Chemiluminescence in Thermal Oxidation of Polymers Apparatus and Method... 

Figure 7 Arrhenius plots for non-isothermal chemiluminescence runs of oxidized polymers, (1) polypropylene, (2) polyethylene, in oxygen, heating rate 2.5°C/min. 

K. Jacobsson, P. Eriksson, T. Reitberger, B. Stenberg, Chemiluminescence as a tool for polyolefin oxidation studies, In A.C. Albertsson (Ed.), Long Term Properties of Polyolefins, Advances in Polymer Science, Springer, 2004, Vol. 169, p. 151. 

G.A. George, Use of chemiluminescence to study the kinetics of oxidation of solid polymers. In N. Grassie (Ed.), Developments in Polymer Degradation-3, Applied Science Publishers, London, 1981, p. 173. 

Abstract The oxidation of polymers such as polypropylene and polyethylene is accompanied by weak chemiluminescence. The development of sensitive photon counting systems has made it comparatively easy to measure faint light emissions and polymer chemiluminescence has become an important method to follow the initial stages in the oxidative degradation of polymers. Alternatively, chemiluminescence is used to determine the amount of hydroperoxides accumulated in a pre-oxidised polymer. Chemiluminescence has also been applied to study how irradiation or mechanical stress affects the rate of polymer oxidation. In recent years, imaging chemiluminescence has been established as a most valuable technique offering both spatial and temporal resolution of oxidation in polymers. This technique has disclosed that oxidation in polyolefins is non-uniformly distributed and proceeds by spreading. 

The history of chemiluminescence from polymers is relatively short. In 1961 Ashby [3] reported that light was emitted from polymers heated in air. Because of the relationship between light and oxidation the term oxylumines-cence was used. Ashby saw the possibility of using chemiluminescence as a tool for testing the stability of polymers and studied the role of oxygen concentration and the effect of antioxidants. A few years later, Schard and... 

Chemiluminescence continues to be a topical probe for investigating oxidation processes in polymers. A number of imaging techniques are now available for... 

Inhibitors reduce oxidative chemiluminescence by reducing the rate of light-producing peroxyl self-terminations (Scheme 1), by quenching electronically excited states (9) or simply by absorption of emitted light. The second factor may be much less important in polymers because of lowered rates diffusion (10). The rate of diffusion of 2,4-dihydroxybenzophenone in polypropylene has been... 

The origin of chemiluminescence in polyolefins has been profoundly analyzed and it has contributed to the better understanding of their complex mechanism of thermooxidation The thermal oxidation of polyethylenes with different manufacturing histories has been compared, which allowed to establish a relationship between CL and some structural characteristics of the polymers. Modification of their stability in the presence of antioxidants, or other additives such as the activity of nano- and micron particles of pigments has been evaluated. 

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