Spin diffusion in relaxation methods for polymers

They showed that such a model could reproduce the kind of behaviour observed experimentally in samples of polypropylene. The question of the kind of behaviour to be expected from such a system had previously been addressed mathematically by Cheung [80], but the results he had obtained were not accessible except in the two limits mentioned above. Although the form of the mathematical equation involved was already well known from the study of conduction of heat in solids [15], the work of Packer et al, [79] was the first approach that allowed the relationship between the observed relaxation behaviour and the intrinsic relaxation and spin diffusion properties of the different regions to be explored between the two limits of slow and 

This new understanding of the role of spin diffusion in determining the observed H relaxation behaviour, particularly in structurally heterogeneous polymer systems can perhaps be briefly summarised as follows. The idea that a simple 1 1 correlation can be made between the number of observed relaxation components and the number of phases or regions present in the material has been shown to be false, but it has also been shown that in favourable cases, measurements can yield valuable information about the size of regions present in the sample. 

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