Positron lifetime measurements have been made in natural polymer-Nistari silk fibers as a function of isochronalannealing temperature in the range of 27℃ to 280℃. The variations in the positron results indicate the structural changesoccurring in the Nistari silk fibers and determine the glass transition temperature as 170℃. Activation energies weremeasured separately for the crystalline and amorphous regions indicating the versatility of the technique. These values areclose to the N--H bond dissociation energy
suggesting N—H bond dissociation as the most probable process occurring during thermal treatment.As an extension of the positron results
the molecular weight of the Nistari silk fibers was determined to be 10.7×105 based on free volume
which lies within the range suggested for the silk fibers.There seems to be an indication that cross-linking changes the spiral structure of cotton fibers to network type.However
this needs to be validated by other techniques.
Abstract
Positron lifetime measurements have been made in natural polymer-Nistari silk fibers as a function of isochronalannealing temperature in the range of 27℃ to 280℃. The variations in the positron results indicate the structural changesoccurring in the Nistari silk fibers and determine the glass transition temperature as 170℃. Activation energies weremeasured separately for the crystalline and amorphous regions indicating the versatility of the technique. These values areclose to the N--H bond dissociation energy
suggesting N—H bond dissociation as the most probable process occurring during thermal treatment.As an extension of the positron results
the molecular weight of the Nistari silk fibers was determined to be 10.7×105 based on free volume
which lies within the range suggested for the silk fibers.There seems to be an indication that cross-linking changes the spiral structure of cotton fibers to network type.However
this needs to be validated by other techniques.
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