Permeability coating

To restrict water entry into certain parts of the delivery system and to separate the drug layer from the osmotic layer, different materials are used as barrier layers. In a multilayered reservoir, the water-permeable coat consists of hydrophilic polymers. In contrast, water-impermeable layers are formed from latex materials such polymethacrylates (Table 7.1). Further, a barrier layer can be provided between the osmotic composition and the drug layer that consists of substantially fluid-impermeable materials such as high-density polyethylene, a wax, a rubber, and the like.20... 

Liquid active formulation + — Barrier layer Water-permeable coat... 

Pennkinetic System Skye Pharma AG, Muttenz, Switzerland The system combines CR principles of ion exchange with membrane diffusion. The system is made up of an ion-exchange polymer-drug complex as a core material, which is subsequently coated with ethylcellulose to form a water insoluble but permeable coating. Release rates are relatively constant and unaffected by variable conditions of the GI tract. The system can be formulated in capsule form as well as suspensions. Delsym (Dextromethorphan), Corsym (Chlorpheniramine) and Cold Factor 12 (Phenylpropanolamine). 

BS. 3546, Part 4, Specification for water vapour permeable coated fabrics. 1991. 

BS - 546. Coated fabrics for use in the manufacture of water penetration resistant clothing Part 2. Specification for non water vapour permeable coated fabrics, 1993. Part 4. Specification for water vapour permeable coated fabrics. 1991. Part 5. Specification for coated fabrics for immersion suits. 1995. 

Chem. Descrip. Carboxyiated styrene-butadiene latex Uses S/B for low permeability coatings... 

P.S. Puri, Process for making highly permeable coated composite hollow-fiber membranes. US Patent No. 4756932, Assigned to Air Products and Chemicals, Inc., July 12, 1988. 

In this new approach, both electrodes are exposed to the same test gas, and separation of the working compartment from the reference compartment is not required. Sensors are fabricated by combining more than one solid electrolyte in an electrochemical chain and/or by using semi-permeable coating to allow one component (or impede the target component) for an alternate electrode reaction. 

For such hydrodynamicaUy soft particles having an impermeable core of radius a and a permeable coating of thickness d, quantitative theories have been developed, mainly by Ohshima. Here, we present the main features of a simple version. Under conditions of ka 1, Krf 1, and when pg, is constant throughout the permeable layer, Ohshima derived the following expression for the electrophoretic mobility ... 

The electric potential profile and the flow velocity profile for a particle with a soft permeable coating are qualitatively represented in Figure 10.9. The electrophoretic mobility comprises two terms The first term on the right-hand side of Equation 10.34 represents the contribution that is related to the potential /(x) across -d < x < 0. This term is sensitive to the ionic strength (through k and the / s). The second... 

FIGURE 10.9 Electric potential profile (—) and flow velocity profile (—) for a particle with a soft permeable coating. 

Epoxy coatings, generally crosslinked with amines or polyamines, are widely used as heavy-duty moisture and chemical-resistant coatings in atmospheric fume environments. When combined with approximately 50% of refined coal tar the amine- and polyamine-cured epoxies are one of the least water-permeable coatings available. However, coal tar epoxies are not normally used in atmospheric exposures because of their sensitivity to UV light. 

Permeable coating Selective layer Microporous support layer... 

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