Application of laser radiation for investigation of oriented polypropylene membranes

Abstract

The oriented microporous polypropylene film membranes have been prepared in the process based on the melt extrusion. Functional characteristics of the membranes (permeability, overall porosity, sizes of pores) were controlled by the parameters of the preparation process. The samples had a well-developed porous structure and contained a through flow channels. The structure of the films was investigated by laser light scattering in dependence on the orientation degree. Light scattering patterns have been obtained using a low-energy He-Ne laser with the power of 5 mW and the wavelength of 633 nm. The optical setup also included the beam-forming system, and the detection unit connected to a PC. To detect the light scattering pattern, a lens less CCD-camera was used. The scattering patterns have a developed speckle structure, and, therefore, to simplify further studies, intensity should be averaged over a sufficiently large number of patterns using a special computer program. These scattering patterns are characterized by a specific type of symmetry and differ from any patterns typical for oriented crystallizable polymers. It is found that similar patterns are observed for all porous samples regardless of their orientation degree. The size of central maximum of the scattering pattern is dependent on the polymer film orientation degree. The results correlate well with the dependence of the porous films overall porosity on orientation degree.

Ordering Effects and Percolation in the Structure Formation Process of the Oriented Polyolefin Porous Films

“…It should be noted that uniaxial extension of the annealed PE and PP films leads to the formation of pores even at small degrees of deformation ε, immediately from the beginning of the extension process that may be observed visually in the change of transparent annealed films to opaque milk-white microporous material because of the light scattering on the walls of pores. 22 Uniaxial extension of the polyolefin samples along the direction of extrusion initiates an ordering process of particles of the solid phase -crystalline lamellae -and the ties connecting them. The self-organization of solid phase particles is accompanied by the increase in anisotropy of mechanical properties of the samples, change in their texture from biaxial to axial, an increasing in the degree of homogeneity of the spatial structure and a significant growth in the permeability, which reaches a value of 250 l/ (m 2 h atm) that is characteristic for the membranes with a regular 3D lattice lamellae 2,5,17.…”

Рассеяние Света Пористыми Ориентированными Пленками Из Полипропилена

“…• C. Для изучения рассеяния когерентного излучения была собрана установка, аналогичная рассмотренной в рабо-те [18]. Установка (рис.…”