Studies on the swell-wet process stretching of polymer materials - Part 7 - Uni- and bi-axial stretching of cellulose acetate films by swell-wet process

Cellulose acetate films were uni- and bi-axially stretched at room temperature in swell-wet agent bath, and the effects of stretching conditions on the molecular orientation and mechanical properties of the films were examined. Following results were obtained: (1)The molecular chain of the films uniaxially stretched with free width was uniaxial orientation with cylindrical symmetry around the stretcing axis, and the anisotropy of mechanical properties in the mechine direction was greater than that of the other samples. (2) For the uniaxially stretched films with constant width, the molecular chainshowed a uniplanar-axial orientation, which are uniaxial to stretching axis along with parallel to the film surface, and the anisotropy of mechanical properties was smaller than that films uniaxially stretched with free width. (3) For the simultaneous biaxially stretched films, the molecular chain showed a uniplanar orientation, which are random orientation within the film along withparallel to film surface at all stretch ratios. The balanced mechanical properties, which were isotropic in the film plane regardless of at all stretch ratio, and improved by stretching.