Dynamic X-ray diffraction technique for measuring rheo-optical properties of crystalline polymeric materials

Abstract

A dynamic X-ray diffraction technique, which can follow the responses of polymer crystals (crystallization, orientation, and lattice deformation) to mechanical excitation of sinusoidal strain induced to bulk specimen, was described. The descriptions for such responses are qualitatively made by using a narrow sector technique, which can measure the X-ray diffraction intensity distribution at a particular phase angle of the sinusoidal strain as a function of static and dynamic strains, temperature, and angular frequency. A typical result is demonstrated in terms of the investigation of orientation crystallization phenomena of natural rubber vulcanizates. More quantitative descriptions can be made by using a half-circle sector technique, which can measure the in-phase and out-of phase components of the dynamic X-ray diffraction intensity distribution. From these, one can obtain the dynamic strain-induced crystallization and orientation coefficients and the dynamic response of lattice deformation of specific crystal plane both as function of temperature and frequency. After a brief survey of the principle of the half-circle sector technique, frequency dependence of the dynamic strain-induced crystallization coefficients of the (002) and (200) crystal planes of natural rubber vulcanizates is demonstrated in terms of the two frequency dispersion regions around 10−2 and 101 Hz at a room temperature. The former and latter dispersions must be correlated with the crystallization processes of the so-calledα- andγ-filaments, respectively. In addition, frequency and temperature dispersions of the dynamic strain-induced orientation coefficient and the dynamic response of lattice deformation of the (110) crystal plane of polyethylene are demonstrated in relation to the so-calledα 1 andα 2 dispersions of dynamic mechanical modulus function of this material.