X-ray diffraction patterns of sol, gel, and total rubber when stretched, and when crystallized by freezing and from solutions

Abstract

Total, sol, and gel rubber were prepared under conditions which were selected to avoid oxidation and structural changes. Total rubber when stretched and exposed to an X-ray beam produced the characteristic crystal fiber pattern. Stretched sol rubber produced no evidence whatever of this pattern even at 1,000 percent elongation. With stretched gel rubber, the pattern was formed above 100 percent elongation, and at 200 percent was sharp and intense. A large interplanar spacing of 54 A, found in the unstretched gel, was absent in the sol. The patterns obtained with stretched gel, with frozen sol, gel, and total rubber, and with gel crystals produced from an ethereal solution were measured and analyzed.

Multi‐scaled microstructures in natural rubber characterized by synchrotron X‐ray scattering and optical microscopy

“…The scattering intensities of these spots are very strong and the scattering volumes are very small, as can be seen from the 3D relief plots of NR, DPNR, Gel, and Sol samples in Figure 7. In spite of extensive X‐ray analysis on NR during the last 80 years,22–34 the existence of these sharp diffraction spots has never been reported before. Because the crystalline reflections appeared too attenuated after a complete spherical powder average, we obtained the 1D WAXD curves shown in Figure 8(A) by integrating the 2D pattern over narrow angular sectors (2 degree each).…”

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

“…Rubber which has become hard and brittle, owing to oxidation, is also amorphous. Purified sol and gel rubber both give the same halo characteristic of total rubber (12). In addition, for gel rubber Clark observed a large spacing of 54 A.…”

Optical and dimensional changes which accompany the freezing and melting of Hevea rubber

“…With X-rays a crystal fiber pattern is obtained. It and the powder pattern obtained with frozen, compact rubber have been shown to indicate similar spacings and are assumed to be caused by the same type of crystal, [7] the differences being ascribed to conditions of orientation.…”

“…Dilute solutions of rubber hydrocarbon in ethyl ether yield small crystals of the hydrocarbon when they are subjected to temperatures between -35 0 and -60 0 C for several hours. 2 The optical properties and melting points of these crystals and their X-ray diffraction patterns [7] indicate their identity with the crystals in stretched and frozen rubber. Under the best conditions the crystals appear in spherulitic groupings, the individual needles in each spherulite having optical properties that closely approach those of a uniaxial crystal with negative elongation.…”