Oxygen enrichment from air through multilayer thin low‐density polyethylene films

Abstract

Several multilayer thin low-density polyethylene (LDPE) films were fabricated by blown thin film having a thickness of 7 m and an area of 130 cm 2 . They were characterized for their oxygen-enrichment performance from air by a constant pressurevariable volume method in a round permeate cell with an effective area of 73.9 cm 2 . The relationship between oxygen-enrichment properties, including oxygen-enriched air (OEA) flux, oxygen concentration, permeability coefficients of OEA, oxygen, nitrogen, as well as separation factor through the multilayer LDPE films, and operating parameters, including transfilm pressure difference, retentate/permeate flux ratio, temperature, as well as layer number, are all discussed in detail. It is found that all of the preceding oxygen-enrichment parameters increase continuously with an increase of transfilm pressure difference from 0.1 to 0.65 MPa, especially for the trilayer and tetralayer LDPE films. The oxygen concentration and separation factor appear to rapidly increase within the retentate/permeate flux ratio below 200, and then become unchangeable beyond that, whereas the OEA flux and the permeability coefficients of OEA, oxygen, and nitrogen seem to remain nearly constant within the whole retentate/permeate flux ratio investigated, especially for the monolayer and bilayer LDPE films. The selectivity becomes inferior, whereas the permeability becomes superior, as the operating temperature increases from 23 to 31°C. The highest oxygen concentration was found to be 44.8% for monolayer LDPE film in a single step with air containing oxygen of 20.9% as a feed gas and operating pressure of 0.5 MPa at a retentate/permeate flux ratio of 340 and 23°C. The results demonstrate a possibility to prepare an oxygen-enriching membrane directly from air, based on the easily obtained thin LDPE films.

Is there a common water-activity limit for the three domains of life?

“…For the xerophilic fungi assayed, agar plugs (4-mm diameter) were taken from the periphery of actively growing cultures of A. penicillioides and X. bisporus and inoculated onto MYPiA supplemented with a range of stressors ( Supplementary Table S8 ). Petri plates were sealed using Parafilm (Neenah, WI, USA) and plates of the same water activity were incubated in bags of polyethylene that allows gaseous exchange but minimises water loss ( Ivanov, 2001 ; Huang et al , 2002 ; Hallsworth et al , 2003a , 2003b ). Colony diameter was measured daily (in perpendicular directions) and used to calculate rates for radial hyphal extension in mm per day (see Williams and Hallsworth, 2009 ).…”

Compatible Solutes Protect against Chaotrope(Ethanol)-Induced, Nonosmotic WaterStress

“…Aerial conidia were obtained from these cultures by incubation for 4 days (for cultures on PDA) or 8 days (for cultures on PDA plus glycerol and on PDA plus KCl) at 25°C. Plates of each medium were kept together in a sealed bag of low-density polyethylene to maintain a constant relative humidity and the medium a w while allowing gaseous exchange (17,20). Conidia from each medium were harvested into sterile AnalaR water (Merck, Poole, United Kingdom), the suspension was filtered through glass wool to remove any hyphal fragments, and the conidia were washed and freeze-dried as described previously (7).…”

Syndiotactic polypropylene copolymer membranes and their performance for oxygen separation

“…Other reports have also shown the possibility of preparing oxygen-enriching membranes based on multilayer low-density polyethylene (LDPE) films. The highest oxygen concentration obtained using LDPE three-layer membranes was 44.8% (permeability of 1 Barrer and O 2 /N 2 selectivity of 4.2) and for the monolayer it was 39% (permeability of 8.2 Barrer and O 2 /N 2 selectivity of 2.7) [10].…”