How Do You Choose the Right Filter Bag Material for Your Process?
From heat and chemical resistance to base fabric vs. membrane and industry-specific criteria
01 · FILTER BAG STRUCTURE
What is a filter bag made of?
A filter bag is a replaceable filter element installed inside a fabric filter dust collector to capture dust from flue gas. A collector fitted with many filter bags is called a baghouse, and the bags repeatedly collect dust and release it through cleaning during operation.
To understand filter media, distinguish the type of base fabric from whether a membrane is laminated. The base fabric is the fiber layer that forms the body of the filter bag, and it affects heat resistance, chemical resistance, and mechanical strength. It is made as nonwoven felt or woven fabric and may be combined with a reinforcing scrim or surface treatment.
An ePTFE membrane is a microporous film laminated onto the surface of the base fabric. A filter bag with a PTFE base fabric and a filter bag with an ePTFE membrane laminated onto a different base fabric are therefore different specifications.
What names are used on site and in quotations?
The same material is often called by an abbreviation or a fiber brand name. When comparing quotations and specifications, first check whether the names below refer to the same material.
| Material | Abbreviations and other names |
|---|---|
| Polyester | PE, PET |
| Polypropylene | PP |
| Acrylic | PAN, homopolymer acrylic |
| Meta Aramid | m-Aramid, Nomex® |
| PPS | Polyphenylene sulfide |
| Polyimide | PI, P84® |
| PTFE | Polytetrafluoroethylene, Teflon® |
| Fiberglass | Glass, glass fiber, FG |
Nomex®, P84®, and Teflon® are registered trademarks of their respective owners.
02 · MATERIAL COMPARISON
What are the key properties and limitations of each material?
A material with high heat resistance can still be vulnerable to acid gases, and one with good acid resistance may still need review for oxidizing atmospheres or repeated abrasion. Look at chemical and mechanical limits along with the usable temperature range.
Key properties of major filter bag materials and selection considerations
| Material | Operating temperature* | Acid/alkali resistance and cautions | Abrasion and mechanical considerations |
|---|---|---|---|
| PTFE | Continuous 232–260°C Peak 260–280°C | Acid: Excellent · Alkali: Excellent Suitable even for humid, strongly acidic gas | Check dust abrasion, cage support, and cleaning conditions |
| PPS | Continuous 190°C Peak 200–218°C | Acid: Excellent · Alkali: Very good Vulnerable at high O₂ and NO₂ levels | With heavy or abrasive dust loads, review media construction together with operating conditions |
| Meta Aramid (Nomex®) | Continuous 190–200°C Peak 218–240°C | Acid: Good · Alkali: Good Use caution where strong acids coincide with high temperature and humidity | Select with repeated cleaning and contact abrasion in mind |
| Polyimide (P84) | Continuous 216–260°C Peak 232–260°C | Acid: Very good · Alkali: Fair Vulnerable to hot alkaline conditions | Multilobal fiber cross-section gives a large surface area that helps capture fine dust[1] |
| Fiberglass (glass fiber) | Continuous 260°C Peak 288°C | Acid: Good · Alkali: Fair Vulnerable to hydrofluoric acid (HF); check suitability for the surface finish | Weak in flex abrasion; design and handling must account for bending, impact, and friction |
| Polyester (PE) | Continuous 130–150°C Peak 150–180°C | Acid: Good · Alkali: Fair Hydrolyzes at high temperature and humidity | Review dust abrasion and surface treatment along with cost |
Material images are generated for illustration only. They do not guarantee the color, texture, or thickness of actual products and are not a basis for identifying materials.
* Temperatures are for dry gas and vary with fabric specification. Normal operating temperature should stay within the continuous operating temperature, and the maximum temperature during startup or upset conditions should stay within the peak temperature. Ratings rank Excellent > Very good > Good > Fair.[2] A table comparing 8 materials, including PP and acrylic, is available in the DuraFill™ filter bag material selection guide. On small screens, scroll the table sideways.
Figure 7. Upper limits of continuous operating temperature and peak temperature by material. Values are for dry gas and vary with fabric specification. For P84, both upper limits are 260°C. See below for why PTFE, shown in green, stands out.
Source: Micro-one Co., Ltd., DuraFill™ filter bag material selection guide
Hydrolysis resistance is a material's resistance to chemical breakdown when exposed to hot moisture. PPS and PTFE have excellent hydrolysis resistance, while polyester and Aramid require care in how they are applied. For PPS, check oxidation resistance separately from acid resistance.[3]
Abrasion resistance cannot be ranked by material name alone. Damage is also influenced by fiber layer construction, reinforcement, and surface treatment, as well as the velocity and direction of incoming dust and the contact between the bag and its cage.
03 · ePTFE MEMBRANE
What changes when an ePTFE membrane is laminated?
If choosing the base fabric is about withstanding the flue gas environment, deciding whether to laminate a membrane is about where dust is captured and how it is released. An ePTFE membrane is a surface filtration layer that reduces dust penetration into the base fabric so dust is captured at the surface. The difference between surface and depth filtration, and how differential pressure changes over operating time, are covered in our earlier article “Depth Filtration vs. Surface Filtration: What Is the Difference?”.
Conceptual diagrams to explain the structure; they do not represent actual thickness, pore size, or color.
A polyester filter bag with an ePTFE membrane must still be reviewed against the operating conditions polyester can withstand. Nor does a membrane alone determine differential pressure or bag life: dust stickiness, moisture condensation, filtration velocity, and cleaning conditions all have to be right.
04 · INDUSTRY CONDITIONS
What should you review first for each industry's flue gas conditions?
Even within one industry, temperature, dust properties, and gas composition vary by source process and collector location. Industry is a starting point for review; the final material should be selected from the operating data of the actual process.
Industry images are generated for illustration and do not depict any specific site or supply record.
Which materials are typically considered for each process?
The table below groups, by process, the materials commonly cited in Micro-one's material guide and in data from overseas filter and fiber manufacturers. The choice varies with collector location and operating conditions even within the same process, so use it as a starting point.
| Process | Flue gas and dust characteristics | Materials typically considered |
|---|---|---|
| Waste incinerator (waste-to-energy) | Acid gases (HCl, SOx), temperature swings, sticky dust | PTFE, P84 / ePTFE membrane where fine dust limits are strict[1][4][5][6][7] |
| Cement kiln | High temperature, heavy fine dust, alkaline components | P84, fiberglass[1][4][5][6][7] |
| Cement clinker cooler and mill | Abrasive dust, hot or at ambient temperature | P84, Meta Aramid, polyester (including blends)[1][4][6] |
| Coal and biomass boilers (power) | SOx, moisture, fly ash | PPS, P84, fiberglass[1][4][5][6][7] |
| Steel and metal smelting | High-temperature flue gas, fine metal dust | Meta Aramid, P84, PTFE (nonferrous metals)[1][6] |
| Asphalt plant | Hot and dry, abrasive aggregate dust | Meta Aramid[4][5][6] |
| Carbon black | High temperature, fine dust | Fiberglass, P84[4][6] |
| Chemical processes | Acids, alkalis, and solvents that vary by process | PTFE, polypropylene (low temperature)[4][6] |
| General dust collection (food, feed, wood, etc.) | Ambient to moderate temperature, dry dust | Polyester, polypropylene (moist dust)[4][5] |
| Spray dryer | Low-temperature humid gas | Acrylic[4] |
PTFE can be considered for processes where high temperature and acid gases occur together. PPS can be considered for acid gas and moisture conditions, but temperature and oxidizing atmosphere must be checked as well. Meta Aramid (Nomex®) is used for high-temperature dust, but strongly acidic conditions or hot, humid environments call for further review. P84 is used in processes that are hot and carry heavy fine dust, such as cement kilns, but hot alkaline conditions should be avoided.
Fiberglass can be an option for high-temperature processes, but mechanical damage and chemical exposure must be considered. Polyester can be an economical choice for relatively low-temperature, dry dust. Gas composition differs from one chemical process to another, so check chemical resistance to each individual component first.
05 · FAILURE & DIFFERENTIAL PRESSURE
Why does a mismatched specification cause early failure or rising differential pressure?
A filter bag has to match operating conditions, not just dimensions. Even with the same length and diameter as the existing bag, a different base fabric, membrane, seam construction, or surface treatment can change operating results.
Loads the material cannot withstand can lead to early failure
Temperatures outside the allowable range, unsuitable gas composition, and repeated contact abrasion can cause damage. Repeated cleaning while the material is weakened can make the damage spread.
Dust that builds up and is not removed increases flow resistance
Differential pressure can rise when sticky dust adheres, the dust cake hardens from moisture condensation, or dust that has penetrated the media is not sufficiently removed. Equipment and operating factors such as increased gas flow, insufficient filter area, and poor cleaning should also be checked.
| Problem | What to check |
|---|---|
| Early tears or holes | Temperature history, chemical degradation, cage contact, dust impingement |
| High ΔP even after cleaning | Internal blinding, sticky dust, condensation, cleaning conditions |
| Higher-than-expected ΔP after replacement | Media permeability, gas flow, filter area, installation condition |
06 · SELECTION CHECKLIST
In what order should you select the material?
Material selection is more accurate when you provide startup, shutdown, and upset conditions along with normal operating values.
- Temperature: normal operating temperature, peak temperature, temperature swings and their duration
- Gas composition: acid gases, oxygen, moisture, and other components that affect the material
- Dust properties: concentration, particle size, abrasiveness, stickiness, hygroscopicity
- Equipment conditions: actual gas flow, filter area, filtration velocity, cleaning method
- Operating history: ΔP trend, damage locations, reasons for replacement, any condensation
- 1STEP 01Operating temperatureKeep only materials whose continuous operating temperature covers normal operation and whose peak temperature covers the maximum during startup and upsets.→ Narrow candidates with the chart
- 2STEP 02Acid gases and moistureIf SOx and HCl levels are high and you operate near the dew point, choose a material with high acid resistance.→ PPS · P84 · PTFE
- 3STEP 03Oxygen and alkalisAvoid PPS where oxygen is high, and P84 under hot alkaline conditions.→ Check whether to rule out PPS or P84
- 4STEP 04Fine dust and NOxIf emission limits are strict, consider an ePTFE membrane; if NOx must also be reduced, consider a catalytic filter bag.→ ePTFE membrane · CataFill™
Source: Micro-one Co., Ltd., DuraFill™ filter bag material selection guide
With this information, the base fabric, membrane, surface treatment, and seam and mounting construction should be decided together. The right filter bag is a specification that withstands the thermal, chemical, and mechanical conditions of the process while maintaining the required dust capture and cleaning performance.
FAQ
Frequently asked questions
Is the material with the highest heat resistance always the safe choice?
No. Heat resistance alone does not determine suitability. Acid gases and moisture, oxidizing conditions, and dust abrasion must also be reviewed, and peak temperature and exposure time must be checked, not just normal operating temperature.
Are all filter bags with an ePTFE membrane PTFE filter bags?
No. The ePTFE membrane is the surface layer, and the base fabric can be PTFE, PPS, P84, Meta Aramid, fiberglass, polyester, or another material. An accurate specification lists the base fabric material and whether a membrane is laminated as separate items.
Can I replace a filter bag as long as it is the same size as the existing one?
Not on size alone. Material, operating temperature, chemical resistance, permeability, cleaning method, and mounting construction must also match. Before replacing, check the existing bag's specification together with actual operating conditions.
- Evonik, P84® Fibres brochure (multilobal cross-section; applications in cement, waste-to-energy, coal-fired boilers, and steel).
- Micro-one Co., Ltd., DuraFill™ filter bag material selection guide (in Korean) (continuous and peak temperatures, acid and alkali resistance by material).
- BWF Envirotec, Filter Media for Industrial Filters (comparison of hydrolysis and oxidation resistance by fiber).
- Micro-one Co., Ltd., DuraFill™ filter bag material selection guide, “Typical applications” (in Korean).
- CPE Filters, Filter Media (applications by material).
- Aokai, PTFE vs PPS vs Aramid vs P84 Filter Bags (industries by material).
- Albarrie, P84 Polyimide Technical Felts (applications).