In physics and engineering, permeation (also called imbuing) is the penetration of a permeate (a fluid such as a liquid, gas, or vapor) through a solid. It is directly related to the concentration gradient of the permeate, a material's intrinsic permeability, and the materials' mass diffusivity. Permeation is modeled by equations such as Fick's laws of diffusion, and can be measured using tools such as a minipermeameter.
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👉 Permeation in the context of Vacuum chamber
A vacuum chamber is a rigid enclosure from which air and other gases are removed by a vacuum pump. This results in a low-pressure environment within the chamber, commonly referred to as a vacuum. A vacuum environment allows researchers to conduct physical experiments or to test mechanical devices which must operate in outer space (for example) or for processes such as vacuum drying or vacuum coating. Chambers are typically made of metals which may or may not shield applied external magnetic fields depending on wall thickness, frequency, resistivity, and permeability of the material used. Only some materials are suitable for vacuum use.
Chambers often have multiple ports, covered with vacuum flanges, to allow instruments or windows to be installed in the walls of the chamber. In low to medium-vacuum applications, these are sealed with elastomer o-rings. In higher vacuum applications, the flanges have knife edges machined onto them, which cut into a copper gasket when the flange is bolted on.
In this Dossier
- ⭐ Core Definition: Permeation
- 👉 Permeation in the context of Vacuum chamber
- Permeation in the context of Adsorption
- Permeation in the context of Vapor barrier
- Permeation in the context of Ultrafiltration
- Permeation in the context of Waterproof
- Permeation in the context of Hazmat suit
- Permeation in the context of Caprock
Permeation in the context of Adsorption
Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. This process differs from absorption, in which a fluid (the absorbate) is dissolved by or permeates a liquid or solid (the absorbent). While adsorption does often precede absorption, which involves the transfer of the absorbate into the volume of the absorbent material, alternatively, adsorption is distinctly a surface phenomenon, wherein the adsorbate does not penetrate through the material surface and into the bulk of the adsorbent. The term sorption encompasses both adsorption and absorption, and desorption is the reverse of sorption.
Like surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements (be they ionic, covalent or metallic) of the constituent atoms of the material are fulfilled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates. The exact nature of the bonding depends on the details of the species involved, but the adsorption process is generally classified as physisorption (characteristic of weak van der Waals forces) or chemisorption (characteristic of covalent bonding). It may also occur due to electrostatic attraction. The nature of the adsorption can affect the structure of the adsorbed species. For example, polymer physisorption from solution can result in squashed structures on a surface.
Permeation in the context of Vapor barrier
A vapor barrier (or vapour barrier) is any material used for damp proofing, typically a plastic or foil sheet, that resists diffusion of moisture through the wall, floor, ceiling, or roof assemblies of buildings and of packaging to prevent interstitial condensation. Technically, many of these materials are only vapor retarders as they have varying degrees of permeability.
Materials have a moisture vapor transmission rate (MVTR) that is established by standard test methods. One common set of units is g/m·day or g/100in·day. Permeability can be reported in perms, a measure of the rate of transfer of water vapor through a material (1.0 US perm = 1.0 grain/square-foot·hour·inch of mercury ≈ 57 SI perm = 57 ng/s·m·Pa). American building codes started classifying vapor retarders in the 2007 IRC supplement. They are Class I <0.1 perm, Class II 0.1 - 1 perm and Class III 1-10 perm when tested in accordance with the ASTM E96 desiccant, dry cup or method A. Vapor-retarding materials are generally categorized as:
Permeation in the context of Ultrafiltration
Ultrafiltration (UF) is a variety of membrane filtration in which forces such as pressure or concentration gradients lead to a separation through a semipermeable membrane. Suspended solids and solutes of high molecular weight are retained in the so-called retentate, while water and low molecular weight solutes pass through the membrane in the permeate (filtrate). This separation process is used in industry and research for purifying and concentrating macromolecular (10–10 Da) solutions, especially protein solutions.
Ultrafiltration is not fundamentally different from microfiltration. Both of these are separate based on size exclusion or particle capture. It is fundamentally different from membrane gas separation, which separate based on different amounts of absorption and different rates of diffusion. Ultrafiltration membranes are defined by the molecular weight cut-off (MWCO) of the membrane used. Ultrafiltration is applied in cross-flow or dead-end mode.
Permeation in the context of Waterproof
Waterproofing is the process of making an object, person or structure waterproof or water-resistant so that it remains relatively unaffected by water or resists the ingress of water under specified conditions. Such items may be used in wet environments or underwater to specified depths.
Water-resistant and waterproof often refer to resistance to penetration of water in its liquid state and possibly under pressure, whereas damp proof refers to resistance to humidity or dampness. Permeation of water vapour through a material or structure is reported as a moisture vapor transmission rate (MVTR).
Permeation in the context of Hazmat suit
A hazmat suit is a piece of personal protective equipment that consists of an impermeable whole-body or one piece garment worn as protection against hazardous materials.
Such suits are often combined with self-contained breathing apparatus (SCBA) to ensure a supply of breathable air. Hazmat suits are used by firefighters, emergency medical technicians, paramedics, researchers, personnel responding to toxic spills, specialists cleaning up contaminated facilities, and workers in toxic environments.
Permeation in the context of Caprock
Caprock or cap rock is a hard, resistant, and impermeable layer of rock that overlies and protects a layer of softer material. In petroleum geology the softer lower layer may be a reservoir of oil or natural gas. The caprock acts similarly to the crust on a pie where the crust (caprock) prevents leakage of the soft filling (softer material). In landforms like mesas and buttes the caprock consists of sturdy erosion-resistant rock like granite or basalt that resists weathering more strongly than its supporting rock and results in differential erosion. It also influences hydrology by creating waterfalls and aquifers where the movement of water is restricted and channeled by the harder layers. As petroleum reservoirs caprocks are often buried under other layers of rock and protected from weathering, they can consist of softer materials like sandstone, limestone, and evaporites, as long as they are highly impermeable and resist the flow of hydrocarbons through them.