STUDY OF TENSILE DEFORMATION MECHANISM OF SOFT COLLOIDAL CRYSTALLINE LATEX FILMS BY SYNCHROTRON SMALL-ANGLE X-RAY SCATTERING

摘要

The deformation mechanism of a styrene/n-butyl acrylate copolymer latex films with polycrystalline and fiber symmetry crystalline structure, respectively, subjected to uniaxial tensile stress was studied by small angle X-ray scattering (SAXS) technique. Firstly, the influence of annealing on microscopic deformation processes was elucidated. The polycrystalline latex films were annealed at 23, 60, 80, and 100 °C for 4 hours, and latex films with fiber symmetry structure were annealed at 23 and 100 °C for 4 hours. It was demonstrated that the microscopic deformation mechanism of the latex films transformed gradually from non-affine deformation behavior to affine deformation behavior with increasing annealing temperature. This behavior was attributed to the interdiffusion of polymeric chains between adjacent latex particles in the film, the extent of which increases with annealing temperature.1-8 The crystalline structure of latex films was preserved even after annealing for 4 hours at temperatures 80K above the glass transition temperature, I.e. The structure is not completely homogenized by interdiffusion. Secondly, the structure evolution of fiber symmetry crystalline latex films of the tensile direction dependence was studied. The films were drawn along directions that were 0, 35 and 55 degrees inclined with respect to the fiber axis of crystallites, respectively. In all cases, the microscopic deformation ratio of crystallites was found to deviate from the affine deformation behavior with respect to the macroscopic deformation ratio. Moreover, the extent of this deviation is different in the three cases. This peculiar behavior is attributed to the relative orientation of (111) planes, the densest planes, with respect to the stretching direction in each case. When the stretching direction coincides with the crystallographic (111) plan, which is the case for stretching direction 0 and 55 degrees inclined with respect to the fiber axis, the system exhibits much more pronounced affinity of the microscopic deformation of crystallites with respect to the macroscopic one than when the stretching direction is arbitrarily oriented with respect to the crystallographic (111) plan as in the case that the sample was stretched 35 degree inclined.