Filter Media Treatments

Filter Fabric Finishes

Non-Fiberglass Finish Purpose Available For
Singe Recommended for improved cake release Polyester, Polypropylene, Acrylic, Aramid, PPS, P-84® (felts), PPS
Glaze Provides short-term improvements for cake release (may impede airflow) Polyester, Polypropylene (felts)
Silicone Aids initial cake development and provides limited water repellency Polyester (felts and wovens)
Flame Retardant Retards combustibility (not flame-proof) Polyester, Polypropylene (felts and woven)
Acrylic Coatings (latex base) Improves filtration, effeciency and cake release (may impede flow in certain applications) Polyester and Acrylic (felts)
PTFE Surface Treatments and Laminates For capture of fine particulate, improving filtration efficiency, cake release Aramid, Polyester, Acrylic, Polypropylene (felt) - Laminates available in Polypropylene, PPS, Polyester, and PTFE
PTFE or Flourocarbon Bath Treatments Improved water and oil repellency; limited cake release Aramid (felt), PE, PP, PPS
ePTFE Membrane (Mikrotex®) For capture of fine particulate, improved filtration efficiency, cake release and airflow capacity Cement/lime kilns, incinerators, coal-fired boilers, cupola, ferro/silica alloy furnace
Acid Resistant Improved acid resistance and water retardance Aramid (felt)
Fiberglass Finish Purpose Applications
ePTFE Membrane (Mikrotex®) For capture of fine particulate, improved filtration efficiency, cake release and airflow capacity Cement/lime kilns, incinerators, coal-fired boilers, cupola, ferro/silica alloy furnace
Silicone, Graphite Teflon® (Graf-O-Sil®) Protects glass yarns from abrasion, adds lubricity For non-acidic conditions, primarily for cement and metal foundry applications
Acid Resisant (Chemflex®) Shields glass from acid attack Coal-fired boilers, carbon black, incinerators, cement, industrial and small municipal boiler applications
Teflon B® (Tuflex®) Provides enhanced abrasion resistance and limited chemical resistance Industrial and utility base load boilers under mild pH conditions
Chemical Resistant Provides improved acid resistance and release properties, superior abrasion resistance, resistance to alkaline attack, improved fiber encapsulation Coal-fired boilers (high and low sulfur) for peak load utilities, fluidized bed boilers, carbon black, incinerators

Fiber Characteristics Chart

  Max Continuous Operating Temprature Abrasion Energy Absorption Filtration Properties Moist Heat Alkalines Mineral Acids Oxygen (15%+) Relative Cost

170° F    (77° C)

Excellent Good Good Excellent Excellent Excellent Excellent $
Polyester 275° F   (135° C) Excellent Excellent Excellent Poor Fair Fair Excellent $
Acrylic 265° F   (130° C) Good Good Good Excellent Fair Good Excellent $$
Fiberglass* 500° F   (260° C) Fair Fair* Fair Excellent Fair Poor** Excellent $$$
ARAMID 400° F   (204° C) Excellent Good Excellent Good Good Fair Excellent $$$$
PPS 375° F   (190° C) Good Good Excellnet Good Excellent Excellent Poor $$$$$$
P84*** 500° F   (260° C) Fair Good* Excellent Good Fair Good Excellent $$$$$$
Teflon*** 500° F   (260° C) Good Good Fair Excellent Excellent Excellent Excellent $$$$$$$

*Sensitive bag-to-cage fit        **Fair with chemical or acid resistant finishes        ***Must use oversized bag for shrinkage for temperatures above 450° F (232° C)     

Teflon is a trademark of E.I. DuPont Company
P-84 is a trademark of Evonik Corporation

Fabrics and Finishes

Felted Filter Fabric Construction

A felted fabric is a thicker, non-woven fabric of synthetic or fiberglass fibers produced by mechanical action, pressure, moisture and heat. One common type is needled felt. Formed when barbed needles move through batts or webs of loose fibers to interlock the fibers. A felt can use a scrim. A scrim is a reinforcing layer of woven fabric.

A web of carded fibers called the “batt” are placed on top of each other or upon a scrim and together, they are passed through the needling machine. 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. Fabric weights are usually expressed in ounces per square yard (OPSY). Standard filtration felts are 10 – 22 OPSY.

Felted Fabric Filter Finishes

A plain fabric is typically only heatset. In many cases a filter fabric is treated (finished) so that it can withstand various conditions, such as moisture or abrasion. Many of the treatments are mechanical surface treatments and others are chemical treatments of either the entire fabric or just the fabric surface.

Mechanical surface treatments generally improve the dust cake formation on the filter and filter cleaning. Common treatments include singed, eggshell, glazed, calender and ePTFE membrane. The first three smooth the surface of the needled felt to improve dust cake formation and filter cleaning.

Singed Running the fabric over an open flame to remove high points and fiber fuzz.
Eggshell Like a singed treatment, but pressure is applied to produce a smoother, eggshell-like surface.
Glazed Like a singed or eggshell treatment, but more pressure is applied to produce a high-sheen surface.
Calender (Acrylic) Compressing a needled felt between rollers, which improved the felt’s density.
Surfcoat Proprietary smooth, non-fibrous, micropermeable coating with excellent dust cake release and improved resistance to blinding.
ePTFE Membrane Laminating an expanded layer of polytetraflouroethylene (PTFE) to woven fabics or needled felts, which makes it easier to clean sticky or very fine dust from the fabric and reduces the required cleaning frequency.

In addition, various filter manufacturers offer proprietary mechanical treatments, depending on the application, to improve the fabric’s surface characteristics. Common chemical treatments include HCE and tricomponent finishes.

HCE™ Immersing the fabric in a noncuring silicone bath that impregnates the fabric so filter is tacky and easily forms a dust cake.
Tuflex® Adding a Teflon® compound to the fabric to improve the fabric’s ability to release dust.

Woven Fiberglass Filter Fabric

Woven fiberglass fabric is available in many weights, weaves and finishes, all of which have an effect on the filtration characteristics of the finished product. Menardi knows fiberglass filtration media better that anyone in the industry. In the 1950’s, it was Menardi that introduced high temperature fiberglass medias to the filtration market. Our groundbreaking research and development into applying finishes to the fragile glass fibers, allowing them to be successfully used in filtration applications, changed the industry. In the 1960’s, Menardi introduced GRAF-O-SIL®, a unique finish comprised of graphite, Teflon®, and silicone. This development has been so successful that GRAF-O-SIL® is the most widely used high temperature finish for fiberglass filter media today. Over the years, Menardi has introduced many of the products and finishes that are considered standards in the industry. To this day Menardi is the only filter bag manufacturer that finishes filtration media in-house, giving us 100% quality control and the ability to develop and custom blend finishes to fit a specific application.

Woven Fiberglass Filter Finishes

Tuflex® Proprietary 100% PTFE finish for improved chemical resistance, dust release, longer life and lower pressure drop. Minimum 10% finish by weight.
Chemflex® Proprietary acid resistance finish for use in chemically aggressive environments.
Graf-O-Sil® Proprietary tri-component all-purpose finish for general applications.
Mikrotex® High efficiency expanded PTFE membrane designed for surface filtration where optimum dust release and high efficiency are required.

Additional Items

Aramid High temperature felt. Sold under the tradenames Nomex® and Conex®. Operates continuously up to 375ºF (excursions up to 425ºF) and exhibits high tensile strength and excellent abrasion resistance.
PPS PPS (polyphenylene sulfide) is a high temperature felt. Widely sold in the past under the tradename Ryton® (no longer available), it is currently available under the tradenames Torcon® and Procon®. Operates continuously up to 375ºF (excursions up to 425ºF) and the same properties as aramid with the additional benefit of excellent acid and alkali resistance.
P-84® High temperature felt. Operates up to 500ºF (excursions up to 550ºF) and exhibits excellent abrasion resistance and good acid resistance. This is a very efficient felt, due to the irregular shape of the fibers, giving them greater surface area.
Micro-Denier™ Utilizes a surface layer of micro-denier fibers (fiber diameter of 10 microns or less) needled to a standard felt substrate where the consideration is to improve the filtration efficiency of the needlefelt without affecting the throughput of the gas-stream.