Pellet boundary disappearance temperature

Fig. 4. Observed pellet boundary disappearance temperature as a function of molecular weight. Points A and B are for the narrow MWD samples PS-55 and PS-118, respectively. Point C is for the broader MWD sample, PS-100. This data is compared to the Tn line drawn from the DSC data of Gillham and Boyer (ref. 4) and to the 7y and Tg hot stage microscope data of Denny et al. (ref. 5). 

Photographs of the reheated moldings of PS-100 are shown in Figure 5. Note that in the same molding temperature range that pellet boundaries disappeared in PS-118 (Fig. 5a vs. Fig. 2b), PS-100 continues to show distinctive pellet reformation. At higher temperatures (Fig. 5b) pellet boundaries are still evident. Indeed, the final disappearance does not occur until 168.0-175.5 C (Fig. 5c). This constimtes a very real difference in behavior from the narrow molecular weight distribution samples shown previously and is plotted as point C in Fig. 4. The reasons for this... 

The second boundary condition is dictated by the symmetry of the (idealized) pellet geometry, i.e. the concentration and temperature gradients must disappear at the pellet center (r = 0 eqs 9 and 10). 

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