Surface Treatment Helps to Improve the Performance of Exhaust Filter Materials

Fibers need to undergo pre-treatment before becoming exhaust greige fabric (unfinished fabric just made from the machine). When exhaust greige fabric is prepared for use as filter material, certain post-treatment or surface treatment must be applied to improve its filtration performance and dust cleaning (peeling) performance. It will also enhance the lifespan and strength of the exhaust greige fabric. The surface treatment methods for exhaust filter materials include heat setting treatment, singeing treatment, hot rolling treatment, impregnation treatment, coating treatment, etc.

Surface Treatments

Heat Setting Treatment

Heat setting refers to the process of maintaining the filter material in a tensioned state at a specific temperature for a certain period. Synthetic fabrics often use heat setting methods to relax the yarns in the fabric, eliminate residual stress from the manufacturing process, and improve the dimensional stability of the fabric..

Singeing Treatment

Singeing involves melting or thermally decomposing the loose fiber ends on the surface of the needle felt to eliminate dust condensation at the fiber ends; burning off the fuzz on the surface of the filter material helps in cleaning the filter material. The singeing process only removes the fibers on the surface of the filter material, leaving the entire filter material unaffected.

Hot Rolling Treatment

Hot rolling treatment can make the surface of the filter material smooth and flat, with uniform thickness; although the resistance is slightly higher after hot rolling treatment, it is less prone to dust penetration, which is beneficial for dust filtration; the steel roller and cotton roller can eliminate the rolling marks on the surface of the cotton roller.

Impregnation Treatment

The process of soaking the filter material in an impregnation tank with a liquid containing specific properties and then drying the impregnated filter material is called impregnation treatment. Impregnation treatment can endow the filter material with certain special properties, such as hydrophobicity, oleophobicity, and flame retardancy.

Coating Treatment

Coating treatment is the process of uniformly applying a certain material to the surface of the filter material. Through coating, the appearance, feel, and intrinsic quality of the filter material can be improved on one side, both sides, or the entire surface. It can also make the product performance meet certain specific requirements, such as making needle felt oil-resistant and wear-resistant.

Other Surface Treatments

The purpose of hydrophobic treatment is to enhance the hydrophobicity of the filter material, preventing dust from adhering to the surface of the filter bag when condensation occurs inside the dust collector. Silicone is used as a water repellent for treatment, offering excellent hydrophobic effect.

Oleophobic Treatment

The purpose of oleophobic treatment is to enhance the oleophobicity of the filter material, which can be treated with fluorides.

Flame Retardant Treatment

Fibers with a limiting oxygen index (LOI) greater than 30%, such as PPS, P84, PTFE, are safe. For fibers with an LOI less than 30%, such as polypropylene, polyamide, polyester, the filter material can be treated with a flame retardant impregnation process.

Anti-Static Treatment

Conductive fibers are added to the filter material or fibers to provide conductivity in the warp or weft direction (with a volume resistivity of less than 109 Ω). Common conductive fibers include stainless steel fibers, carbon fibers, and modified chemical fibers.