How to choose between glass fiber and PTFE ULPA?

This problem occurs frequently in semiconductor and precision manufacturing projects. The two names sound like different materials, but when actually selecting a model, there are many more things to compare than the material names.

Glass fiber and PTFE represent filter material types, not product grades. Under the same grade, both materials can be made into ULPA, and both can be made into U15 and U16. They differ in resistance characteristics, moisture resistance, outgassing behavior, compatibility with process environments, as well as cost and maintenance practices. Some of these differences can be compared quantitatively, while others can only be judged based on specific working conditions.

Unify the comparison conditions first

Compare two materials assuming product and service conditions are aligned.

The levels must be consistent. Comparing U15 and U16, the efficiency requirements are different, so the comparison results are meaningless. Unify the grade first, then compare the materials.

The appearance and structure should be comparable. If the outer frame size, thickness, sealing method, and presence of partitions are different, the difference in resistance may come from the structure rather than the material itself. For specific comparison methods, please refer to the relevant instructions on resistance comparison.

The test conditions must be consistent. The test air volume, test object (filter material or finished product), and test method must all be aligned. Out-of-condition efficiency or resistance numbers are not directly comparable.

The application conditions must be clear. Where it is used, what media it is exposed to, the temperature and humidity range, and whether there are any gas release requirements. Only when these information are determined can we know which differences are really important to the project. involving HEPA/ULPA air filter products of different grades are compared in the same way.

How to look at resistance characteristics

The difference in resistance between fiberglass and PTFE is not fixed.

PTFE membrane materials may exhibit lower resistance under certain structures. The porosity and surface properties of the membrane structure make it possible for smaller friction losses when airflow passes through. But this advantage depends on the design of the specific product. Not all PTFE models have lower resistance than glass fiber.

The resistance of fiberglass filter media is generally more stable. The diameter and distribution of glass fibers are relatively uniform, and their performance can be expected under normal working conditions. When designing pleats, the control of effective area and pleat distance is relatively mature.

The actual difference in resistance may come more from the structural design than the materials themselves. Under the same size and grade, the pleat density, effective area, and mesh design of a product may have a more obvious impact on resistance than the type of filter material. When comparing, use the resistance curve of the complete finished product rather than just comparing material data. Supporting FFU fan filter unit or For the system of the fan filter unit at the EFU equipment end , the filter element resistance and fan operating point must be calculated together.

How to judge suitability for working conditions

There are differences in the performance of the two materials in different environments, and this part is often more critical than resistance.

High humidity environment. PTFE has low hygroscopicity, and its performance stability may be more advantageous under working conditions with high humidity. After the glass fiber absorbs moisture, the resistance may change, depending on the fiber surface treatment and edge sealing material. If the project has a risk of condensation or cleaning operations, PTFE generally tolerates better. For specific selection methods, please refer to the relevant instructions for high-humidity environments.

Corrosive gas or solvent environment. PTFE is generally more chemically inert than glass fiber. If the gas stream is likely to be exposed to acidic, alkaline, or organic solvent components, PTFE may be a safer choice. However, it should be noted that the filter material is only a part of the entire material, and the treatment of the colloid, sealing gasket and outer frame must also be evaluated together.

Breathing requirements. Where the semiconductor process has strict requirements on material outgassing, the performance of the two materials may be different. You cannot judge based on the material name alone. You must confirm the applicability of the entire product under the target working conditions. involving The selection of ULPA ultra-high efficiency filter can be checked based on specific process requirements.

High temperature environment. The temperature resistance of fiberglass is generally better, but the specific upper limit depends on the edge sealing glue and outer frame material. PTFE has different temperature resistance ranges, and the entire product also needs to be checked. Don’t just look at the temperature resistance data of the filter material. The colloid and seals are often the weak links. For specific selection methods, please refer to the relevant instructions on high temperature resistance.

Material risks should be checked item by item

If the project has special requirements for materials—such as sensitivity to boron, metal ions, organic matter outgassing, etc.—confirm each item when selecting.

Don’t just look at the filter material statement. Just because a product is labeled 'PTFE filter material' or 'low outgassing' does not mean that the entire finished product meets the process requirements. The support layer, edge sealing glue, gasket, and outer frame surface treatment may all affect it. The entire material list must be checked in full.

The testing conditions must be clear. If the project requires outgassing testing of a certain material, confirm the testing method, sample range, and criteria. Only the filter material sample is tested and cannot represent the performance of the finished product. For specific verification methods, please refer to the instructions related to low outgassing.

Material changes are to be evaluated. If the change is from glass fiber to PTFE, or the PTFE supplier changes batches, the impact scope of the change should be assessed. It cannot be assumed that 'the material name is the same' means the performance is the same. For specific procedures, please refer to the instructions related to filter material batch changes.

Cost and maintenance should also be factored into the comparison

Procurement costs. PTFE filter media is usually more expensive, but the difference depends on specifications and usage.

Running costs. Differences in resistance will affect fan energy consumption. If the resistance of the two materials is close under the target working conditions, the difference in operating energy consumption will not be significant; if the resistance of PTFE is significantly lower, it may save energy in long-term operation. For specific accounting methods, please refer to the relevant instructions on operating energy consumption.

Replacement cycle. The dust holding capacity and tolerance of the filter material affect its service life. In high humidity or corrosive environments, PTFE may last longer, reducing replacement frequency and downtime costs. These differences should be evaluated based on actual working conditions and cannot be generalized.

Comprehensive cost. Only by comparing the purchase price, operating energy consumption, replacement cycle, and downtime costs together can we judge which solution is more economically suitable. Comparison of a single indicator may lead to one-sided conclusions.

Project judgment example

A certain semiconductor equipment needs to be equipped with an optional ULPA filter. The process environment contains trace amounts of acidic gas and the humidity is controlled at a low level.

The supplier provides two solutions: fiberglass U15 and PTFE U15, with the same size and similar resistance data.

Comparison process: First unify the grade and size and confirm that the resistance is comparable. Check the applicability of the working conditions again - in acidic gas environments, the chemical inertness of PTFE is more advantageous; but if the concentration is low, glass fiber combined with appropriate edge sealing materials may also meet the requirements. Finally, compare the comprehensive cost: the purchase price of PTFE is higher, but if the frequency of replacement can be reduced, the long-term cost may be similar.

The final selection depends on the project's assessment of material risks and budget constraints. This case illustrates: Material selection is not an absolute matter of 'which one is better', but 'which one is more suitable for this working condition'. involving HEPA/ULPA air filters is the same. The selection logic for

Selection and Acceptance Checklist

About Aili Industrial’s filter material selection packages

The choice of fiberglass and PTFE ultimately depends on the specific working conditions and the overall material configuration. The more complete this information is, the more targeted the selection will be.

Aili Industry has independent manufacturing capabilities in filters, fans, control systems and sheet metal processing, and can provide ULPA ultra high efficiency filter、HEPA high-efficiency filter and supporting air supply equipment. For projects that require material selection, we can assist in confirming the filter material type and overall material configuration based on the working conditions, gas release requirements and installation space. When the filter is matched with equipment such as FFU and EFU, the filter element resistance and fan operating point can also be checked together.

When enquiring, provide the usage environment, media conditions, gas release requirements and installation conditions to help confirm the appropriate filter material solution. The specific selection is subject to the technical documents and test results confirmed by the project.