(380n) Cellulose Nanocrystal (CNC) Nanocomposite Membranes for Gas Separations

Separation of gases is ubiquitous in industrial processes for both the purification of feedstocks and products. Membrane based separations are often the most efficient separation technique leading to decreased energy consumption and operating costs when compared to other separation techniques. Membrane separations have limitations including a tradeoff between permeability and selectivity and poor mechanical properties in many of the materials with desirable separation properties. In this work we fabricated dense film nanocomposite membranes containing CNCs and investigated the impact on mechanical properties, gas transport, and morphology.

Nanocomposite films were made using Covestro Texin Rxt 70A thermoplastic polyurethane (TPU) or one of three Kuraray Kurarity poly(methyl methacrylate)/poly(n-butyl acrylate)/poly(methyl methacrylate) triblock copolymers with 20% PMMA (LA2140), 33% PMMA (LA2250), or 50% PMMA (LA4280), with as received CNCs. Mechanical strength of CNC-TPU composites increases as the CNC loading level increases for all loading levels below the point at which the CNCs begin aggregating. Conversely the permeability of all gases tested decreased when CNCs were added to the TPU; however, that decrease was constant for all loading levels tested and did not affect the selectivity of the membrane. For the block copolymer membranes, a lamellar morphology was present for all PMMA levels confirmed through AFM and SAXS with LA4280 showing the largest d-spacing and LA2250 exhibiting the smallest d-spacing. For LA2140-CNC the lamellar d-spacing increased. while the permeability of nitrogen was unchanged from the unloaded LA2140 membrane.