POROUS STRUCTURE AND FUNCTIONAL PROPERTIES OF HIGHLY-PERMEABLE POLYPROPYLENE FILMS

 The porous polypropylene films, containing through channels and permeable for liquids, have been prepared by the method based on extrusion of polymer melt with subsequent annealing, uniaxial extension and thermofixation. We studied the effect of film preparation conditions on the characteristics of porous structure and functional properties of the films (porosity and permeability) at the stages of extension at room temperature ("cold" drawing) and the additional stage ("hot" drawing). Permeability, size and the number of through pores were measured by filtration porosimetry. Overall porosity is determined as a portion of the sample volume occupied by pores by measuring the density ratio of porous and nonporous films. The film surface images, which demonstrate the characteristic features of the porous structure, have been obtained by scanning electron microscopy. The effect of melt orientation degree during extrusion (spin draw ratio) on the films porous structure is determined. It was found that the increasing of spin draw ratio leads to the growth in through permeability, overall porosity and pore sizes of the films. It was shown that the growth of orientation degree at the additional "hot" drawing stage gives the possibility to increase the functional characteristics of porous samples. In the films preparation process, which includes two stages of extension ("cold" and "hot" drawing), the values of overall porosity and permeability of 60 % and 400 l/(m²×h×atm), respectively, were reached. They are ones of the highest values as compared with values of these characteristics presented in the scientific and patent literature for polymer porous films and they determine the efficiency of their practical application as filtration materials

1. Kesting R.E. Synthetic Polymer Membranes: A Structural Perspective. 2^nded. NY: John Wiley & Sons, 1985. 368 p.
2. Mulder J. Basic Principles of Membrane Technology. Springer, 1991. 363 p.
3. Passaglia E. Crazes and fracture in polymers // Journal of Physics and Chemistry of Solids. 1987. V. 48. N 11.
   P. 1075–1100. doi: 10.1016/0022-3697(87)90119-3
4. Волынский А.Л., Ярышева А.Ю., Рухля Е.Г., Ефимов А.В., Ярышева Л.М., Бакеев Н.Ф. Деформационное размягчение стеклообразных и кристаллических полимеров // Успехи химии. 2013. Т. 82. № 10. С. 988–1006.
5. Флеров Г.Н., Апель П.Ю., Дидык А.Ю., Кузнецов В.И., Оганесян Р.Ц. Использование ускорительной техники для изготовления ядерных мембран // Атомная энергия. 1989. Т. 67. С. 274–280.
6. Park I.K., Noether H.D. Crystalline "hard" elastic materials // Colloid and Polymer Science. 1975. V. 253. N 10. P. 824–839. doi: 10.1007/bf01452402
7. Ельяшевич Г.К., Курындин И.С., Лаврентьев В.К., Бобровский А.Ю., BukosekV. Пористая структура, проницаемость и механические свойства микропористых пленок из полиолефинов // ФТТ. 2012. № 9. С. 1787–1796.
8. Курындин И.С., Лаврентьев В.К., BukosekV., Ельяшевич Г.К. Перколяционные переходы в пористых пленках полиэтилена и полипропилена с ламелярной структурой // ВМС. Серия А. 2015. Т. 57. № 6. С. 497–503. doi: 10.7868/S2308112015060139
9. Zhang S.S. A review on the separators of liquid electrolyte Li-ion batteries // Journal of Power Sources. 2007. V. 164. N 1. P. 351–364. doi: 10.1016/j.jpowsour.2006.10.065
10. Ельяшевич Г.К., Курындин И.С., Розова Е.Ю. Светопропускание пористых полиолефиновых пленок в иммерсионных средах // Оптический журнал. 2017. Т. 84. № 7. С. 64–69.
11. Шибаев В.П., Бобровский А.Ю., Ельяшевич Г.К. Жидкокристаллические и фотохромные композиты на основе пористых пленок полиэтилена // Жидкие кристаллы и их практическое использование. 2006. № 4. С. 107–118.
12. Bobrovsky A., Shibaev V., Elyashevitch G. Photopatternable fluorescent polymer composites based on stretched porous polyethylene and photopolymerizable liquid crystal mixture // Journal of Materials Chemistry. 2008. V. 18. P. 691–695. doi: 10.1039/B711929A
13. Bobrovsky A., Shibaev V., Elyashevich G., Rosova E., Shimkin A., Shirinyan V., Cheng K.-L. Photochromic composites based on porous stretched polyethylene filled by nematic liquid crystal mixtures // Polymers for Advanced Technologies. 2010. V. 21. N 2. P. 100–112. doi: 10.1002/pat.1404
14. Bobrovsky A., Shibaev V., Abramchuk S., Elyashevitch G., Samokhvalov P., Oleinikov V., Mochalov K. Quantum dot–polymer composites based on nanoporous polypropylene films with different draw ratios // European Polymer Journal. 2016. V. 82. P. 93–101.doi: 10.1016/j.eurpolymj.2016.06.017
15. Pozhidaev E., Bobrovsky A., Shibaev V., Elyashevich G, Minchenko M. Ferroelectric liquid crystal composites based on the porous stretched polyethylene films // Liquid Crystals. 2010. V. 37. N 5. P. 517–525. doi: 10.1080/02678291003681386
16. Ельяшевич Г.К., Козлов А.Г., Розова Е.Ю. Оценка размеров сквозных каналов в микропористых пленках из полиэтилена // ВМС. Серия А. 1998. Т. 40. № 6. С. 956–963.
17. Ельяшевич Г.К., Розова Е.Ю., Карпов Е.А. Микропористая полиэтиленовая пленка и способ ее получения // Патент РФ №2140936. 1997.
18. Курындин И.С., Розова Е.Ю., BukošekV., Ельяшевич Г.К. Влияние ориентационных воздействий на структуру и физико-механические свойства пористых пленок полиэтилена // ВМС. Серия А. 2010. Т. 52. № 12.
    С. 2123–2130.
19. Stauffer D., Aharony A. Introduction to Percolation Theory. London: Taylor and Francis, 1994. 180 p.
20. Bukošek V., Elyashevich G.K., Novikov D.V., Kuryndin I.S., Jelen A. Ordering effects and percolation in the structure formation process of the oriented polyolefin porous films // Acta Chimica Slovenica. 2017. V. 64. N 4. P. 980–987. doi: 10.17344/acsi.2017.3696

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