The identity of crystallization in a stretched smoked sheet of rubber, in pale crepe, and in frozen rubber was established. A small expansion by freezing was found in smoked sheet ribbons of rubber stretched to various degrees. Maximum expansion occurred with the stretching of about 200-300 percent of the original length, and there was no, or almost no expansion in the case of stretching which was higher than about 700 percent. From these facts a new theory was proposed to explain the crystallization of rubber by stretching, milling, freezing and compressing. In this theory long chain molecules of rubber are cousidered to form large irregular spirals having numerous isoprenes many more than two in one turn of the spirals.

View full abstract