| Abstract: | Samples of ordinary “ash-free” cellulose papers and similar samples decrystallized by swelling in liquid ammonia were pyrolyzed in vacuo to a weight loss ranging from <0.1% to nearly 20%. The samples were then nitrated and their molecular weight distributions determined by gel permeation chromatography. When weight loss reached 1%, both the ordinary and the ammonia-swelled celluloses showed a large drop in average degree of polymerization (D.P.). However, the ordinary cellulose showed this sharp drop long before there was any measurable weight loss; the ammonia-swelled cellulose changed D.P. only gradually in the early stages. Further, x-ray diffraction measurements showed that by the time the D.P. of the ammonia-swelled cellulose had dropped appreciably, the material had developed a significant crystalline pattern. These results support the suggestion that initial rupture of the cellulose molecule occurs at strain points at the crystalline–amorphous boundaries. |
