The Contribution of X-ray Research to the Knowledge of Rubber.

Strain-Induced Crystallization of Natural Rubber: A Review of X-Ray Diffraction Investigations

“…31 Nevertheless, if crystallites appear to be more oriented with the stretch (and also with the time), their size seems to remain constant. 30 This last point is very important and was already suggested in 1926 by Hauser and Mark 62 who noticed that the "half-value width" of the spots did not change appreciably with stretch; consequently, these authors considered that the increase of crystallinity is explained by an increase in the number of crystallites rather than by an increase of their size. This idea is today widely accepted [except for the early stage of SIC (Ref.…”

“…Detailed review articles on this subject were published in 1939 and 1940 by Clark 29 and Gehman, 30 respectively. These authors pointed out that vulcanization of rubber does not affect its ability to crystallize.…”

Crystallization of Vulcanized Rubber

“…Previous work on unvulcanized rubber (S) showed that it can be crystallized at temperatures between +10°and -40°C ., the crystals melting in a range from about 6°to 16°C. Crystallization and fusion are accompanied by changes in volume (8), heat capacity (4), light absorption (IS), birefringence (14,15,16), x-ray diffraction (9), and mechanical properties such as hardness (IS). X-ray diffraction and birefringence, of course, give the most direct evidence of crystalline structure, but in the present work change of volume, as measured in a mercury-filled dilatometer, was chosen as the criterion of crystallization or fusion.…”

X-Ray Structure of Rubber-Carbon Black Mixtures

“…The photographic density of the Ai diffraction spot was then plotted against the elongation, and the curve was extrapolated a short distance to zero photographic density. The shape of the elongation-intensity curve was previously discussed (7). In general, it is not linear.…”

“…The disadvantage in depending on natural foods for a supply of vitamin-A-active material is that the activity declines rapidly under ordinary circumstances after the plant has been cut and stored (18). The destruction of the vitamin A activity is now thought to be due to an oxidation process, the factors influencing the reaction being the presence of air and enzymes, temperature, and light (7,8,9,21). This tendency to deterioration can be greatly reduced by dehydration at relatively high temperatures, but even the dehydrated tissue is subject to some loss of vitamin A activity, depending on storage conditions (7,21).…”