Carbon dioxide, photoacoustic

Conventional rigid polyisocyanurate foams blown with HCFC-141b often suffer from poorer compressive strengths, dimensional stability and inferior inflammability properties when compared to foams blown with CFC-11. An improved isocyanurate conversion test by photoacoustic Fourier Transform Infra Red technique is introduced. The method is not limited to polyisocyanurate foam, as isocyanate conversion is an important parameter to follow in PU foams as well, especially in all carbon dioxide blown foams. The method is found to be quite reproducible and further statistical analysis to ensure the validity of this technique is under way. 8 refs. 

The methodology involved the monitoring of diffused gas by a photoacoustic analyser. Diffusion coefficients measured for carbon dioxide and oxygen were 2.77 X 10 cmVs and 1.68 x 10 cmVs, respectively. To support the gas diffusion results, thermal properties were studied using photoacoustic spectroscopy and... 

Permeation studies of carbon dioxide and oxygen were performed using a sample holder which, has its sides sealed off one from another. The permeate gas being studied was introduced on one side and kept at a constant pressure of 0.10 MPa. On the other side the concentration of the gas was measured using photoacoustic gas analyser. The gas concentration (C), in these conditions, is given by [62] ... 

TIRES and TIRTS have many of the same properties as photoacoustic spectrometry (see Chapter 20), in that they are largely insensitive to sample morphology and to the optical properties of the sample, such as scattering coefficient and front-surface reflection. Similarly, TIRES and TIRTS spectra are also largely unaffected by the sample backing (if any) and the surrounding atmosphere, although emission from hot water vapor and carbon dioxide must sometimes be subtracted from the spectrum after the measurement. 

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