| 摘要 |
An improved method is described for the solvent casting of ultrathin non-porous membranes having surface areas of greater than one square foot. Film thicknesses of less than 200 Angstroms are routinely obtained, because the solidified film remains substantially free of tensile stress during the formation and removal thereof from the liquid casting substrate. The casting solution used comprises polymer dissolved in a solvent system and is characterized by being able to spontaneously spread over the surface of the liquid casting substrate. The casting solution is deposited in a narrow, longitudinally-extending defined region at the surface of the casting substrate; the surface area and perimeter of the defined region are enlarged over the surface of the casting substrate in a manner whereby only casting solution is moved relative to the casting substrate and, once desolvated, the polymer film formed remains stationary relative to the casting substrate and substantially free of tensile stress.
|
