Measurement of orientation crystallization rates of linear polymers by means of dynamic X-ray diffraction technique. II. Frequency dispersion of strain-induced crystallization coefficient of natural rubber vulcanizates in subsonic range

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Abstract
The orientation crystallization behavior of natural rubber vulcanizates was investigated by means of a dynamic X-ray diffraction technique utilizing the half-circle sector technique. The frequency dependence of dynamic diffraction intensities from diatropic and paratropic crystal planes, (002) and (200) planes, was observed over a frequency range from 10−3 to 101 Hz as a function of temperature, degree of cross-linking, static extension ratio, and dynamic strain amplitude. The frequency dependence of the dynamic X-ray diffraction gives two dispersion regions around 10−2 and 10−1 Hz. The phase angle between the dynamic X-ray diffraction and dynamic strain of a bulk specimen is definitely positive; i.e., the dynamic strain of the specimen is always behind the dynamic orientation crystallization. The frequency dispersion at low frequencies, around 1WZ Hz is very obvious for the (200) crystal plane and shifts somewhat to higher frequencies under those conditions that increase the mobility of self-diffusion of rubber molecules, i.e., increase of temperature and decreases of extension ratio and degree of cross-linking. The frequency dispersion at high frequencies, around 101 Hz, is rather obvious for the (002) crystal plane and does not shift appreciably under the experimental conditions.

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