Measurement of crystallization in stretched rubber by rapid-passage NMR

✍ Scribed by E. Von Meerwall; R. B. Creel; C. F. Griffin; E. DiCato; F. T. Lin; F. M. Lin

• Publisher: John Wiley and Sons
• Year: 1977
• Tongue: English
• Weight: 530 KB
• Volume: 21
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1977.070210605

✦ Synopsis

Synopsis

Continuous-wave rapid-passage proton NMR (30 MHz) was performed on lightly crosslinked natural cis-polyisoprene a t elongations up to 720%, at temperatures between -100" and 1OO"C, and after delays of up to several weeks after stretch. A method of separating the spectra into a narrow and a wide component was developed and applied. The results are interpreted in terms of the effects of a glass transition and strain-induced crystallinity and are in general agreement with results by other methods. The degree of crystallinity is found to increase strongly with strain (from zero for unstretched samples to 31% a t elongations of 720% a t room temperature), to increase with time, reaching equilibrium most rapidly in the most highly strained samples, and to decrease approximately linearly with temperature above about 20°C.