X-Ray Diffraction Patterns of Hevea, Manihot and Other Rubbers

Abstract

Abstract When rubber from Hevea brasiliensis is stretched quickly and exposed to a beam of x-rays, a crystal fiber diffraction pattern is obtained.” During previous work, done jointly by the National Bureau of Standards and the University of Illinois on sol and gel fractions of this rubber, no pattern was produced by the stretched sol fraction. With the stretched gel fraction, however, the pattern was sharp and intense. Rubber from Manihot glaziovii also may be separated into sol and gel fractions, and in recent work they, too, have been stretched and examined by x-rays. With the stretched Manihot sol, a few interferences were obtained, but many more resulted with the stretched gel. When crystallized by “freezing” at low temperatures for 24 hours, the interferences from the gel again outnumbered those from the sol. The x-ray measurements of Manihot rubber agree with those of Hevea rubber and indicate that the same structure exists in each. Rubbers obtained from latices of Funtumia elastica, Cryptostegia grandiflora and Castilla elastica were also examined. Their structures, too, were like that of Hevea rubber, and the similarity confirms earlier observations made when x-ray technique was less highly developed. In crystallized specimens, the crystals melted within the range of temperatures previously observed with Hevea rubber. In earlier work a large spacing was observed in a specimen of unstretched Hevea gel rubber. This spacing has been observed also in a new specimen of stretched Hevea gel rubber, together with a second spacing approximately twice as large.