Ultraviolet photoacoustic spectroscopy evaluation of the distribution of ultraviolet absorber paint additives as a result of processing
The application of UV photoacoustic spectroscopy to the evaluation of UV-absorbing paint additives in clear paint layers is described. This technique enables the quantitative analysis of additive concentration and aids in determining the effects due to paint processes and substrate composition changes on additive concentration. The inclusion of photoacoustic phase information is essential to offset the saturation effects that dominate these strongly absorbing samples. Two analysis techniques are evaluated, both of which partially or totally utilize the phase data. When comparisons between samples on substrates with different heat capacities are needed, the phase-only method is preferred. Otherwise, the two methods give comparable results. Using these methods, two different paint/substrate/additive systems are easily evaluated for changes in process or changes in substrate materials. The instrumentation and interpretation methods are discussed in detail.