Liquid permeation testing

Gas permeation tests have been carried out for many carbon membranes. However, there is very limited data for the liquid permeation tests, especially for the application of carbon membranes for ultrafiltration (UF) or microfiltration (MF). Some studies [1,2] demonstrated that carbon UF membranes could be made by adding non-carbonizing polymers such as poly(ethylene glycol) (PEG) to the precursor solution. Encouraged by the findings of [3] and [4], Shah and co-woikers successfully made nanoporous carbon UF membranes suitable for bioprocessing applications [5]. 

Permeation rate Pure gas or liquid permeation test... 

Diffusion and Permeation Testing 23.4.4.1 Kinetics of Liquid Diffusion Tests... 

Water permeability is tested by transmission permeation tests, standard test ASTM E 96 being widely used. The water which permeates is absorbed in a desiccant and its weight—or alternatively, the loss of weight of the water supply from a container (or permeation cup ) sealed by the sheet test sample—is determined. The same procedure is applied for the transmission of volatile liquids in standard ISO 6179 (BS 903 A46)—see Eigure 23.7. 

Estimations of Liquid-Permeation Rates from Absorption Testing... 

The results indicate that Sudan black penetrated into the bulk phase of lens. The dye permeation test of LBL-coated lens in wet conditions did not show stain. However, when a thin layer of liquid water exists on the surface, the dye test losses validity in terms of evaluating the barrier property of the coating because the oil spreads on the water layer, which acts as a barrier to oil-soluble dye. Wet uncoated lens did show the dye stain, which probably indicates that water on uncoated lens is not as strongly held by the surface as LBL-coated surface. The dye permeation test of LBL-coated lenses under blotted and dried conditions showed stain. The stain in blotted sample was spotty and the color intensity is less than that for the dried surface, which is more intense than that for uncoated lens, i.e., dried LBL-coated lens has the strongest dye absorption. 

When the test piece is removed from the liquid, the volume or mass will decrease with time as the liquid permeates back out. For volatile liquids this dictates that the time between removal and test is critical and it may be necessary- to extrapolate back to zero time. It is also possible to dry the test piece and by further weighing estimate the amount of matter extracted, but this is liable to be inaccurate. The physical properties after drying can be measured and may be particularly relevant for some applications. 

One of the important requirements of any packaging material is that it should not release any component into the drug product. Preparation of containers free of any leachables such as monomeric component is especially important for the containers of ophthalmics, parenteral products, and any liquid products. It was shown that di(2-ethylhexyl) phthalate was released from the PVC bags and that caused haziness of the taxol solution (37), USP/NF offers the protocol of chemical, spectral, and water vapor permeation tests and tolerances for plastic containers (55). Among those, chemical test is designed to give a quantitative assessment of the extractable materials in both organic solvents and water. 

Swelling or sorption test of liquids and vapours through the rubber is obtained by the standard method of ASTM D 814 and ISO 6179 2010 as a general method for various types of rubber. Other standard methods to test liquid and water vapour transmission rate are displayed in Table 27.1. Gas permeation test is obtained by the standard method of ASTM D 1434-82 and ISO 2782 as a general method, especially for oxygen gas mostly using ASTM D 3985 as a protocol for measurement. Table 27.2 exhibits the standard methods of gas permeability test. 

Some special test methods which have illuminated the applications of polymer blends are grouped together towards the end, viz., aroma barrier test, permeation test for liquids, and environmental stress cracking, which are special in nature but not really obtained the status of ASTM or BS methods. Nevertheless, they are used in industry as they meet the special application requirements of these wonderful materials. The chapter concludes with a discussion of these aspects. 

Permeation tests by pouring liquids in bottles and monitoring the weights of the bottles with regard to time have been practiced in many laboratories (Armstrong 1968a, b Mesrobian et al. 1968 Subramanian 1983, 1984, 1985, 1987 Jen-Taut 1997 Xavier and Pendyala 2008). 

Table 7.3. Diffusion coefficients of substances in three different HDPE geomembranes (see caption of Table 7.1) obtained from immersion and permeation tests with pure test liquids (Muller et al. 1997b) ...

Test liquid Immersion test Sample 48 D (10- m /s) Immersion test Sample 139 D (10" m2/s) Permeation test Sample a D (10 m2/s)... 

Fig. 7.2. Sketch of test cell assembly for permeation tests with a mixture of 9 liquid organic components (methanol, acetone, tetrahydrofurane, isooctane, trichloroethylene, toluene, tetrachloroethylene, chlorobenzene, xylene) (August et al. 1992). The diameter of the cells is 30 cm, the thickness of the mineral liners 7.5 cm, 15 cm, 30 cm and, in two cases, as much as 60 cm...

F1407-12 Standard Test Method for Resistance of Chemical Protective Clothing Materials to Liquid Permeation-Permeation Cup Method... 

Wipe sampling involves swiping a dry or wet (use of a solvent or other liquid besides water in eommonplaee) eloth, glass fiber filter paper, or swab over the surfaee of a potentially eontaminated objeet and performing a laboratory analysis. Both the inner and outer surfaees of PPE should be tested to eheek for permeation. Skin ean also be tested using this wipe sampling [1]. 

ASTM D-3536-91, Standard Test Method for Molecular Weight Averages and Molecular Weight Distribution by Liquid Exclusion Chromatography (Gel Permeation Chromatography-GPC), ASTM Annual Books of ASTM Standards, Vol. 08.02, P. 349—359. This method was deleted in the 1997 edition of the ASTM book. 

The problem of permeability exists whenever a plastic material is exposed to vapor, moisture, or liquids. Typical cases are electrical batteries, instruments, components installed underground, encapsulated electrical components, food packaging, and various fluid-material containers. In these cases, a plastic material is called upon to form a barrier either to minimize loss of vapor or fluid or to prevent the entrance of vapor or fluid into a product. From the designers viewpoint, the tolerable amount of permeation established by test under conditions of usage with a prototype product of correct shape and material is the only direct answer. 

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