What is Media?

Filter media is the permeable barrier through which fluid passes and contaminant is retained.

The filter media used in a filtration system has a direct and significant impact on the particulate removal efficiency, the vulnerability to element failure, and the pressure drop across the system. Filter media is available in a wide range of materials, forms, retention ratings and characteristics. Selection of the appropriate filter media is one of the most important steps in designing a filtration system.

Membranes are flexible fixed pore size barriers that provide a high level of filtration efficiency. Filters utilizing membrane media are rated at or above 99.97% efficient and can pass several challenge tests including bubble point, bacteria challenge, and pressure hold. Membranes can be constructed from a number of materials including Nylon, PTFE, Polypropylene, and Polysulfone. Filter media is considered any barrier placed in the path of fluid with the purpose of intercepting particles. A membrane can be considered the filter media. Filter media is not necessarily a membrane.

Acrylic
A man-made fiber made from acrylonitrile and spun into fibers. In filtration it is primarily used to manufacture resin bonded depth type filter cartridges. Common applications include paints, coatings, inks and adhesive component manufacturing. Acrylic provides good chemical resistance to most acids, but is primarily used because of its high temperature compatibility (up to 275° F). Acrylic is also referred to as orlon.

Activated Carbon
Activated Carbon can also be called Activated Charcoal, or Granular Activated Carbon (GAC). Because of its adsorbent properties, it is most often used in filtration for removal of taste, odors and chlorine from water. Activated Carbon has an affinity for hydrocarbons and most organics and will remove particulate as well. Activated Carbon is often used in the plating industry to remove trace organics that can contaminate the plating bath. It is also used in the pharmaceutical industry and food and beverage industry for color and taste removal. Activated Carbon is usually encased in a polypropylene support.

Cellulose
Cellulose is the generic term for the carbohydrate that is the chief component of the cell wall of plants. In filtration cellulose is generally combined with a resin to make a sheet and pleated or molded into a depth cartridge. Pleated cellulose cartridges are used extensively in the metal working industries on coolants and oils. They are also used for filtering fuels and process liquids. Cellulose provides good chemical resistance to most alcohols, aromatic hydrocarbons, ketones, ethers, glycols, amines, and esters. It is also effective at high temperatures. Most pleated cellulose filter cartridges are supported by electro-tin-plated core and scrim. Resin bonded cellulose cartridges have no support core.

Cellulose-Fiberglass
This media is a combination of cellulose and fiberglass fibers to provide the best attributes of each media. The cellulose media provides loft and high dirt holding capacity while the fiberglass media provides high filtration efficiency. This media type is used primarily in hydraulic/lubrication filtration.

Cellulose/Polyester
This combination of filter media is often used in air filters. It is economical and also works well in coolant applications.

Cotton
Cotton is most often used in wound filter cartridges. It accommodates high temperatures well. Cotton stringwound filters offer a very economical choice for non-critical filter applications where solids loading is not extremely high. In some applications the oil used to lubricate the cotton can extract into the solution being filtered causing foaming. The cotton media is typically supported with a polypropylene or steel core.

Cotton/Polyester
This blend is often used in air filters because of the low cost, and good dirt holding capacity. Caution must be taken to avoid fungal growth on the filter media.

Glass Fibers/Fiberglass
Filters using a fiberglass media typically are string wound or pleated. The fiberglass filter media provide high solids holding capabilities and good chemical resistance even at temperatures up to 750° F. Fiberglass filters are used extensively on aviation fuels, air filtration, coolants and oil filtration. Fiberglass filters are used extensively to filter hydraulic lubricant.

Nylon
Nylon is used in a wide variety of filters. Filter bags, wound cartridges, pleated cartridges and membrane cartridges all use Nylon as the filter media. It has good chemical resistance, low extractables and is naturally hydrophilic. Nylon cartridges are rated at 250° F.

Polyester
Polyester is a manmade fiber produced by the reaction of ethylene glycol and terephthalic acid. Polyester is commonly used as a filter media in bag filters, pleated filter cartridges and depth filter cartridges. The media can be spun bonded or melt blown. Because of this flexibility, strength and economical cost it has proved to be a popular filter media. Polyester offers higher temperature capabilities than polypropylene and does not adsorb oil to the same degree. It has excellent chemical resistance. Polyester fibers have a tendency to fibrillate. Fibrillating is an advantage in coarse filter applications, but contributes to shedding in fine sub-micronic filter applications.

Polyethylene
Polyethylene is similar to polypropylene but has a higher temperature rating. Polyethylene is most often used in critical filtration applications.

Polyolefin
Polyolefin is a bicomponent mix of polypropylene and polyethylene. Filters manufactured from this material demonstrate excellent chemical compatibility with acids and other aggressive chemicals. The media is melt blown to form a depth cartridge typically used in beverage filtration, plating solutions, magnetic media manufacturing, potable water applications and organic solvents. Temperature limitations are similar to polypropylene.

Polypropylene
Polypropylene is the most broadly used filter media. It is used in filter bags, cartridges, air filters, and absolute rated membranes. The fibers can be wound spun, melt blown, hydro-entangled or cast for a membrane. It is used in almost all industries. Polypropylene has excellent chemical compatibility and will adsorb oil. Melt blown polypropylene filters are often used in coolant and parts washing applications because of its ability to remove tramp oils. FDA grade polypropylene is approved for food contact and can be used in food and beverage applications. Polypropylene is naturally hydrophobic making it a good choice for non-critical vent filtration applications.

Polysulfone/PES
Polysulfone is a popular choice for filter membranes in the pharmaceutical and electronics industries because of its low protein binding characteristics, low extractable levels and hydrophilic nature. Because it can be cast extremely thin reducing pressure drop and is resistant to chlorine it is often used as a reverse osmosis membrane in potable water applications. Polysulfone can handle a wide range of liquids across the full pH range including most organic solvents. Most polysulfone membranes have an asymmetrical pore structure (the pore is larger one side of the membrane than the other). The asymmetrical pore structure, combined with an extremely thin membrane increases the flow rate and reduces the pressure drop. Polysulfone has good temperature and chemical resistance and can be sterilized with hot water, steam, sodium hypochlorite, chlorine or alcohol.

PTFE
Polytetrafluoroethylene (PTFE) is a fluorine containing manufactured fiber characterized by high chemical stability, relative inertness, high melting point and extreme hydrophobicity. PTFE filter media can be cast as a membrane and pleated or formed into fibers and felted to make filter bags. PTFE membranes make excellent vent filters, allowing air to be vented but preventing particulate, moisture, and microorganisms from leaving or entering the tank. Because PTFE is so chemically inert it is excellent in high temperature and corrosive chemical service and can be sterilized with steam, sodium hypochlorite, alcohols, or hot water.

Rayon
Rayon is derived from regenerated cellulose (wood fibers). The cellulose wood fibers are combined with sodium hydroxide, shredded and reacted with carbon disulfide to produce fibers. It is the oldest commercial manmade fiber. The fibers are used to make string wound filter cartridges or felt filter bags. Rayon filters readily adsorb water and are acceptable in most applications up to 250° F. They are not recommended in mineral acid applications; however, Rayon is recommended in organic solvent applications. In applications where bacterial growth is a concern avoid using Rayon.

Stainless Steel
Stainless steel media can take many forms. Stainless steel wire cloth is woven wire made to a particular wire count and pattern. Examples include 100 mesh (100 wires per inch in both the warp and fill directions) and 165 x 1400 twilled weave that contains 165 wires per inch in the warp direction and 1400 wires per inch in the fill direction. These media have a rigid, uniform pore size. Wire cloth media is sometimes sintered to "lock-in" the pore size by sintering the wires together at all crossover points. Stainless steel wire cloth is typically made from 304 or 316 stainless steel. The fine wire cloth is normally made from 316L stainless steel, a low-carbon (<.03% C) grade.

Sintered powdered metal media is made from compacted powered metal particles that have been sintered to form a rigid, porous media. This media has a tortuous flow path and is usually used when high temperature and high differential pressure resistance is required. Generally sintered powdered metal is made from 316 or 304 stainless steel.