Polyester is the most versatile, most cost effective and most widely used filter medium for dust collection. It is strong, abrasion resistant, can work up to 150°C and has good resistance to common acids, solvents and oxidising agents.
Polyester's only real weakness is a tendency to hydrolyse at elevated temperature which means that moisture can break down the fibres and cause them to revert to their basic constituents. This results in powdering of the fibres and a serious loss of strength.
Being a high volume fibre means that polyester filter felts can be produced from a wide variety of sizes from microdenier (typically 9 microns in diameter) up to 3 denier (18 microns). These finer deniers allow the collection of finer dusts (even sometimes replacing membranes) and/or the attainment of lower emission levels:
0.7 Denier
2.2 Denier
Many modest temperature applications are suited to polyester:
| Nuisance dusts | Lead |
| Fertiliser | Grain handling |
| Cement | Vacuum cleaners |
| Plaster | Polishing |
| Wood | Quarrying |
| Metal processing | Tobacco |
| Ceramics | Flour |
| Smelting | Milk |
Andrew Webron pioneered the superglaze finish for polyester which now is the standard treatment for effective filtration. Other finishes can include singeing and calendering to modify properties such as permeability.
Chemical enhancements are common with polyester fibres, particularly LR5 which is a powerful oleophobic and hydrophobic finish. These felts can also be FR treated and can have surface and embedded foams added to further modify collection efficiency, for example, in the attainment of BIA accreditation.
As polyester is essentially a 'plastic' it is prone to the build up of static charge because it doesn't dissipate electricity; so in applications where the dust may be explosive, conductive fibres can be added to reduce this risk. These range from epitropic fibres to copper sulphide to stainless steel.
Alternatively, we developed our range of checkstatic grid scrim products where conductive yarns are incorporated into the woven scrim. For the ultimate protection, we advocate our checkstatic grid scrim along with a small percentage of steel fibres intimately mixed with the polyester fibres.
Polyester particularly lends itself to the production of Fibrelox™ needlefelts. This innovative range of materials is produced on proprietary manufacturing equipment and obviates the need for a reinforcing scrim.
Well over a half of our company's output uses this technology testifying to its effectiveness, see these typical properties:
| Technology | g/m² | mm | dm³/dm²/min | MD N/5cm | XD N/5cm | |
|---|---|---|---|---|---|---|
| P0500P1G | Conventional | 500 | 1.7 | 150 | 1580 | 1750 |
| P0500ZZG | Fibrelox™ | 500 | 1.9 | 175 | 1145 | 1565 |
In conclusion, polyester is the workhorse of the dust filtration industry.
