Membranes reinforced

EPDM is by far the most widely used material in the ballasted roofing system constmction. Because of EPDM s flexibiHty, very large sheets of up to 10,000 square feet (929 m ) can be deHvered to the job site in compact roUs that offer reduced labor on the roof in the seaming process. The typical EPDM sheet size used in ballasted systems is 12 by 30 m and 1.1 mm thick. EPDM is also widely used in both the fully adhered and mechanically fastened roofing systems. In these constmctions, both 1.1- and 1.5-mm thick material is used with widths from 2.1 to 15 m. A majority of the installations use nonreinforced sheet, although reinforced membrane can also be used in all of the system types. The majority of the reinforced sheets go into mechanically fastened systems. 

PVC. Poly(vinyl chloride) (PVC), a very versatile polymer, is manufactured by the polymerisation of vinyl chloride monomer, a gaseous substance obtained from the reaction of ethylene with oxygen and hydrochloric acid. In its most basic form, the resin is a relatively hard material that requites the addition of other compounds, commonly plasticisers and stabilisers as well as certain other ingredients, to produce the desired physical properties for roofing use. The membranes come in both reinforced and nonreinforced constmctions, but since the 1980s the direction has been toward offering only reinforced membranes. The membrane thickness typically mns from 0.8—1.5 mm and widths typically in the range of 1.5—4.6 m. 

Water uptake and swelling of reinforced PEMs have also been studied. It has been found that water uptake and water flux of Nafion/porous PTFE PEMs increases with increased ionomer loading and that the rate of water uptake as a function of temperature is actually higher for the reinforced membrane in comparison to Nation 112.2 However, it was also seen that the actual water uptake of a similar reinforced membrane was about half as much as a Nation 1135 sample with a commensurate lower degree of swelling.2 ... 

Although Tyrann-M/E and even conventional membranes are superior to the new polyamide and polyfvinylidene fluoride) membranes with respect to flow rates and filtration capacities, the latter two are more suitable for filtration of most (but not all) organic solvents and, partially as a result of their lower void volumes (Table IV) exhibit mechanical and thermal properties which are generally superior to those of the cellulosics. It should also be noted that in the special case of fiber-reinforced membranes, the mechanical properties are predominantly functions of the embedded fibers rather than of the membrane structu reverse. 

FIGURE 3.9 Circulating water photoreactor system for determination of photomicro-biocidal activity under water flow conditions, a, reinforced membrane used in the study b, water jacket, continuous flow, infrared filter c, light source d, air pump e, bacterial air filter f, 3-way tap/pressure release g, 2-way taps h, frit for aeration J, peristaltic pump k, reservoir 1, ground glass Joints for ease of cleaning and sterilization (Bonnett et ai, 2006). 

The sulfonated polysulfone as well as polyetheretherketone can be cast as a film on a screen. After the evaporation of the solvent a reinforced membrane with excellent chemical and mechanical stabilities and good electrochemical properties is obtained. 

Thin Reinforced Membrane for Improved Mechanical Properties... 

Ralph, T.R. and Barnwell, D., Extended PEMFC durability from MEAs based on a new reinforced membrane, ECS Trans., 3, 579, 2006. 

Most commercial systems like Mustang from Pall and Sartobind from Sartorius make use of functionalized microporous membranes. The fibrils reinforced membranes are (pleated) layered around a porous core. The feed is forced to permeate through the membranes in radial direction. This approach results in high area to volume ratio. The 3M and Mosaic Systems approach is different. Instead of functionalization of a porous support they make use of already functionalized beads, which are embedded in a porous support. In this approach, the beads are responsible for the capacity and selectivity where the porous matrix controls the hydrodynamics. The 3M modules consist of stacked flat sheet or pleated membranes, while Mosaic Systems makes use of porous fibers in which the active particles are embedded (Figure 3.23). 

FIGURE 27.41 (A) Schematic representation of a fibril-reinforced membrane and (B) a cross-sectional image after tearing. (Reproduced... 

S. Hommura, Y. Kunisa, I. Terada, and M. Yoshitake. Characterization of fihril reinforced membranes for fuel cells. Journal of Fluorine Chemistry 120, 151-155 2003. 

Nitrocellulose (reinforced) membranes with 0.45 p.m pores are usually chosen over nylon since false positives are the main problem. However, nylon is more flexible, more durable, can be used with TMAC and allows more reprobing with different probes to reduce... 

The sulfonated polysulfone can be cast into a film on a screen and precipitated after most of the solvent has been evaporated, leading to a reinforced membrane... 

Chil Glas. [Childers Prods.] Reinforcing membrane. 

Recently, DuPont has introduced a new membrane that is an improvement in comparison to earlier versions NR-111, NR-112, and NR-211. DuPont Nation XL membrane is an extended-lifetime reinforced membrane based on chemically stabilized PFSA/PTFE copolymer in the acid (H-f) form. The reinforcement improves the handling of the membrane and its physical properties. When the reinforcement is combined with the chemically stabilized polymer, the membrane... 

In order to improve the lifetime of the membrane, DuPont made efforts in the direction of mechanical reinforcement of the PFSA membrane. Generation A reinforced membrane performs better in OCV hold tests and RH load cycle tests compared to PFSA cast membranes. 

As can be seen in Figures 21.26 and 21.27, reinforced membranes show an increase in the OCV hold lifetime by a factor of 7. Although chemically stabilized ionomer was not yet used in generation A reinforced membranes, these improvements can still be attributed to improved chemical... 

FIGURE 21.26 OCV hold test comparison between Nafion cast membrane and reinforced membrane. (From Choudhury, B., Material challenges in proton exchange membrane fuel cells, International Symposium on Material Issues in a Hydrogen Economy, November 12-15, Richmond, VA, 2007.)... 

FIGURE 21.28 Relative PER comparison of Nation cast membrane, generating a reinforced membrane and chemically stabilized reinforced membrane during the accelerated OCV durability test. (DuPont, 2002.)... 

Currently, Nation is available in two forms extrusion-cast membranes and polymer dispersions. Nation polymer dispersions are used in the formulation of GDEs and reinforced membranes. Nation 117 is 7 mils thick (1 mil = 25.4 ttm) but can be obtained thinner. Table 1 illustrates the current offering of Nation from DuPont [75]. A number of excellent review articles exist that describe the structure, morphology, physical properties, and applications ofNation [56,76-81]. 

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