Relative oxygen permeation

They have also modeled a perfectly mixed membrane reactor for the same reaction. For this membrane configuration, the C2 selectivity is essentially 1(X)% for a jo value of less than 0.2 and drops off rapidly with increasing The yield becomes greater as the relative oxygen permeation rate increases. The yield reaches a maximum and then decreases with the permeation rate. There is only a limited range of Jo in which the yield can reach beyond 20%. 

Figure 1.1 (a) Relative oxygen permeation and (b) relative tensile modulus of various polymer... 

Figure 8.16 Relative oxygen permeation and water vapor transmission through the epoxy nanocomposites (montmorillonite filler) as a function of filler volume fraction [13].

Li et al. [107] also reported the change in residual radical concentration vs oxygen permeation time for a homopolymerization of EGDMA. At 110°C, the radical concentration decreased by approximately 12.5% in 90 min. While at 180 °C, the radical concentration dropped nearly 62.5% over the same time period. While these reactions occurred over a relatively short time period, the temperatures were quite high and certainly one would expect significantly reduced rates at lower temperatures below the glass transition temperature of... 

Polyvinylidene chloride (PVDC), polyethylene (LDPE and HDPE), polypropylene (PP), PVC, and polystyrene all have excellent resistance to oxygen permeation. Polyethylene also has relatively good resistance to the permeation of water, which makes it an excellent choice for bread bags. 

In this figure the oxygen permeation is plotted as a function of the relative pressure of cyclohexane. The curve, which was obtained from the membrane before the CVI-experiment, shows a clear transition point. This is indicative of a mesoporous material, in this case with a calculated Kelvin radius of 2.5 nm. For the membrane after CVI no such curve could be obtained and no clear transition point could be observed. This behaviour is representative for microporous materials. 

If the oxygen permeation constant and the rate of oxygen consumption for the material remain relatively constant as a function of total absorbed dose, a steady state in heterogeneous oxidation will be approached. If the rate of oxygen consumption by reaction with free radicals generated by the radiation exceeds the rate of supply of oxygen from the edges of the polymer sample, distinct... 

Barrier resins, polymers which have relatively low rates of small molecule permeation, have revolutionized the packaging industry in recent years. For food packaging applications, it is specifically desirable to impede oxygen permeation. Each food type has its own particular packaging requirements, which leads to the use of many polymer classes at a variety of temperatures and relative humidities in these applications. 

Figure 1 shows the effect of relative humidity (RH) upon the oxygen permeation values (OPV) of a few representative polymers. This data is reported in the units of cc-mil/(100 sq.in.-day-atm). For many polymers such as polyethylene, OPV is essentially unaffected by changes in RH. 

A Mocon (Modern Controls, Inc.) instrument modified for accurate humidity control was used to measure the oxygen permeation value (OFV) on film structures. These were generally measured at 30°C and 80% relative humidity and are reported as cm3 O2/100 in2-day-atm. 

Figure 1 shows the oxygen permeation values for a series of blends of aluminum, mica and talc in an EVOH resin containing 44 mole % ethylene. The relative effectiveness of the three fillers are proportional to their aspect ratios as predicted by theory. 

These blends exhibit improved barrier to oxygen permeation even at high relative humidity... 

Relative oxygen permeability of nanocomposites with imidazolium modified montmorillonite as a function of filler volume fraction. The permeation behavior is compared with composites containing dioctadecyldimethylammo-nium ions [22] ( ) Ammonium and (a) Imidazolium composites. The dotted lines only serve as guides. (Reproduced from Mittal, V., Eur. Polym. /., 43, 3727, 2007. With permission from Elsevier.)... 

Polyamide MXD-6 is the product of condensing metaxylylene diamine with adipic acid. This polymer has proved to be an outstanding gas barrier for example, at 100% relative humidity, it has lower oxygen permeation than ethylene-vinyl alcohol copolymer (30% ethylene). Otherwise, it is similar to... 

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