Chemiluminescence photon-counting system

A unique chemiluminescence photon-counting system, designed specifically for measurement of stress-enhanced polymer reactions, was used for the studies described here. This system Includes a miniature tensile stress device, a controlled environment chamber and a luminescence detection system and associated optics Integrated Into a single unit. 

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. 

Chemiluminescence and photoluminescence are other forms of interference that can reduce the accuracy of LS techniques. Chemiluminescence describes the emission within the scintillation cocktail of photons that result from a chemical reaction common initiators are samples with an alkaline pFl or the presence of peroxides. Photoluminescence can occur when the scintillation cocktail is exposed to ultraviolet light. Some substances in the cocktail, notably the scintillator, are excited and then emit light when the species return to ground state. The effect of photoluminescence is reduced in LS systems by decay when the sample train is held in a dark environment for a few minutes prior to counting. On the other hand, chemiluminescence may have a slow decay rate that requires a change in sample preparation to eliminate the chemical that causes it. Some LS systems identify luminescence by pulse shape and indicate its relative extent. 

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