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 a mechanical excitation of sinusoidal strain induced to a 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 orientationcrystallization 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 a specific crystal plane both as functions 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-called α- and γ-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-called a₁ and a₂ dispersions of dynamic mechanical modulus function of this material.