Fibers

A felted fabric (also called felt) is a thicker, non-woven fabric of synthetic fibers produced by mechanical action, pressure, moisture and heat. One common type is needled felt which is formed when barbed needles move through batts or webs of loose fibers to interlock the fibers. During the needling, barbed needles punch the web fibers into the woven base to create the felted product. Increased felt thickness can be achieved by repeating this process. At Day Filters™ our filter bags are made in America, with top quality felts that provide longer bag life, meet strict emission standards, at the lowest installed costs.

Following is a list of our felt fabrics and their characteristics:

• POLYESTER Has good resistance to chemicals, abrasion and heat degradation. In addition, polyester fibers have excellent dimensional stability. It has the widest applications for dust collection; particularly in the wood industry, powder and grain handling, and general material handling. It is not recommended for moist, high temperature applications.
  
  
• POLYPROPYLENE Combines the virtues of strength and excellent resistance to most acids and alkalies. Having the lowest density of most synthetic fibers used in dust collection, it offers the greatest cloth yield per pound of yarn. As such, it is one of the more economical synthetics. The sleekness of the fiber yields a fabric that provides good cake discharge during pulse cleaning and a resistance to blinding. Since minimal moisture is absorbed, it can be used in many applications with high moisture.
  
  
• ACRYLIC Offers a good combination of abrasion resistance, and resistance to heat degradation under both wet and dry conditions. An outstanding characteristic is the ability of acrylics to withstand hot acid atmospheres, making this fiber a good choice in the filtration of exhaust gases. Acrylic fibers are used for dust collection in the manufacturing of ferrous and non-ferrous metals, carbon black, cement, and lime fertilizers.
  
  
• ARAMID Has good dimensional stability and excellent heat resistance. It can be used at temperatures up to 425º F (at which many other fibers melt). Unlike glass, it is resistant to fluorides and has good abrasion and flex resistance. It has a wide range of applications in the cement industry, non-ferrous metals and steel industries, and carbon black applications. It is also known as Nomex®.
  
  
• P-84® (Polymide) features high temperature resistant material with good chemical permeability and high filtration efficiency. It is mostly utilized in cement kiln, waster incinerator and coal boilers. It features high heat resistance, high acid resistance, low pressure dropy, and good dust cleaning.
  
  
• PPS (Polyphenylene Sulfide) is a high temperature thermoplastic fiber with excellent resistance to hydrolysis and so is a good complement to aramid fibers, being frequently used where susceptibility to moisture is a problem. PPS needlefelts can incorporate conductive fibers to reduce the possibility of static electricity build up, which help mitigate the potential of explosion with susceptible dusts. PPS properties include resistance to heat, acids and alkalies, and to mildew, to bleaches, aging, sunlight, and abrasion. Also known under brand names such as Ryton® or Techtron®.
  
  

Finishes

At Day Filters™, we have the capability to apply a variety of chemical treatments to our felt media. These finishes can considerably improve a felt’s performance, efficiency, and bag life. Treatments can be applied on each fiber individually, or by coating the filtration surface of the felt. Also a combination of both treatments can be done, depending upon the application requirements.

• SINGEING The melting of surface fibers with a gas flame to reduce the tendency of dust particles to stick to the surface. It is recommended for improved dust cake release. A singed finish is a common option for polyester felt.
  
  
• GLAZING Also known as the “eggshell” finish, is the melting and smearing of a microscopic layer of media fibers to form a slick surface for better dust release. A glazed finish is another common option for polyester felt made with fine fibers.
  
  
• EGGSHELL Like a singed treatment, but pressure is applied to produce a smoother, eggshell-like surface.
  
  
• SILICONE A treatment which is applied to all of the fibers individually. The presence of the silicone considerably reduces any cake cleaning problems associated with sticky, agglomerating dusts. Silicone treating also reduces moisture absorption; however, it is not advisable for food applications. Silicone treating is a standard option for polyester and acrylic felts.
  
  
• PTFE (Polytetrafluoroethylene) is a hydrophobic (water-repelling) material that is inert to concentrated mineral acids, organic acids, alkalies, oxidizing agents, and organic solvents at elevated temperatures. PTFE has a low coefficienct of friction resulting in good cake discharge during pulse cleaning. A common trade name is Teflon. PTFE can be applied to filter media as a membrane thermobonded on needled felts as an available standard. Or it can be applied as a spray (known as Teflon® coating) which is a lower cost alternative to PTFE membrane technology and is available as a special.
  
  
• ACRYLIC Involves a coating of porous acrylic foam which is applied to the felt surface to effectively simulate an instant dust cake. Via effective control of the foam cell "bubble" structure a very uniform pore structure is applied to the filtration surface. The benefits of this type of coating include improved filtration on the felt surface as well as improved filtration efficiencies without incurring increased filter pressure drop.