Hollow Fiber Porous Nanocomposite Membranes Produced via Continuous Extrusion: Morphology and Gas Transport Properties

Abstract

In this work, hollow fiber porous nanocomposite membranes were successfully prepared by the incorporation of a porous nanoparticle (zeolite 5A) into a blend of linear low-density polyethylene (LLDPE)/low-density polyethylene (LDPE) combined with azodicarbonamide as a chemical blowing agent (CBA). Processing was performed via continuous extrusion using a twin-screw extruder coupled with a calendaring system. The process was firstly optimized in terms of extrusion and post-extrusion conditions, as well as formulation to obtain a good cellular structure (uniform cell size distribution and high cell density). Scanning electron microscopy (SEM) was used to determine the cellular structure as well as nanoparticle dispersion. Then, the samples were characterized in terms of mechanical and thermal stability via tensile tests and thermogravimetric analysis (TGA), as well as differential scanning calorimetry (DSC). The results showed that the zeolite nanoparticles were able to act as effective nucleating agents during the foaming process. However, the optimum nanoparticle content was strongly related to the foaming conditions. Finally, the membrane separation performances were investigated for different gases (CO2, CH4, N2, O2, and H2) showing that the incorporation of porous zeolite significantly improved the gas transport properties of semi-crystalline polyolefin membranes due to lower cell wall thickness (controlling permeability) and improved separation properties (controlling selectivity). These results show that mixed matrix membranes (MMMs) can be cost-effective, easy to process, and efficient in terms of processing rate, especially for the petroleum industry where H2/CH4 and H2/N2 separation/purification are important for hydrogen recovery.

Examining the Influence of Re–Used Nanofiller—Pyrolyzed Montmorillonite, on the Thermal Properties of Polypropylene–Based Engineering Nanocomposites

“…MMT layers, due to the ‘labyrinth’ effect, limit the oxygen diffusion into the polymer bulk and hinder volatile decomposition products to escape. Moreover, the motion of macrochains in the presence of MMT layers is considerably reduced [17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36].…”

Gas transport properties of cellular hollow fiber membranes based on LLDPE/LDPE blends

“…In our case, the selectivities (separation efficiency) were around 1.2 and 2.0 under the same conditions for the neat membranes, but the permeances (separation rates) are very high (10-80 GPU compared to 0.5-15 Barrer) due to the porous structure of the membranes (for a comparison between flat membranes and hollow fibers, see Chen et al 36 ). When zeolite 5A porous particles were added in a subsequent study, 56 the selectivities obtained were 8.5 and 2.0, respectively. These results clearly show that specific membranes (formulation and structure) are mainly suitable for specific gas separations (molecules and conditions) and there is no "universal" material for all the situation, that is, there is a need to select the right membrane for the application to perform.…”

The State-of-the-Art Functionalized Nanomaterials for Carbon Dioxide Separation Membrane

“…NCM is prepared by dispersing nano-sized material into the polymeric network of a membrane. The logic to this combination is that the membrane can benefit from the inherent advantages of both materials, i.e., (i) the superior separation property of inorganic nanomaterials [26,51,52], and (ii) the ease of processing polymeric materials that is widely available at relatively low cost [53,54]. Moreover, the incorporation of nanomaterials, also referred to as nanofiller, can boost the performance of a membrane beyond the selectivitypermeability limit [55,56].…”