Gamma-Radiometric Study Of Thermal Decomposition

An investigation into using the absorption of gamma-radiation as a non-destructive analysis method for the study of thermally decomposing woods and polymers. A comparison of the decomposition characteristics of flame retarded materials has also been undertaken.
A narrow, collimated beam of '137’Cs gamma-rays are passed through 50 mm cubes of wood or polymer, perpendicular to one-dimensional heat flow from a bank of well characterised infra-red heaters. The resultant gamma-rays are analysed, and the thermal degradation is indicated by the decrease in absorption of the sample as it decomposes. Moving the sample relative to the y-ray beam allows local densities to be determined throughout the bulk of the material. Simultaneously, temperatures are measured at various points within the samples, and these are used in conjunction with the absorption data to describe the overall decomposition with a first order kinetic model. This allowed the calculation of activation energy E, and pre-exponential factor A.

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