Photoacoustic signal normalization method and its application to the measurement of the thermal diffusivity for optically opaque materials

A normalized photoacoustic method, especially suitable for thermal diffusivity measurements of highly optically opaque materials, is described. The photoacoustic signal for normalization in this case, unlike other normalized photoacoustic methodologies, corresponds to a semi-infinite reference material in the front photoacoustic configuration. The amplitude and phase of the sample's photoacoustic signal, in transmission, are normalized with the corresponding ones of the reference. The normalization methodology yields, in this way, two independent thermal diffusivity values. This thermal property was measured for two polymers (black paint and black plastic tape); good agreement between the two thermal diffusivities measured for each material was obtained.