Trenntech’s filtration laboratory in Frankfurt, Germany, has long been dedicated to exploring the frontiers of materials science. Today, we demystify three mainstream filter media: the traditional king glass fiber, the new plasticized contender melt-blown polypropylene (PP), and the electrostatic magician electret, and discuss who will lead the future.
What is Glass Fiber?
Technical Characteristics
Glass fiber filter media are the foundation of the HEPA/ULPA field. By drawing molten glass into micron-sized fibers (typically 0.5-5 microns in diameter) and randomly stacking them to form a complex three-dimensional network structure, its filtration mechanism relies purely on physical interception.
Core Advantages:
- 1. Stability and Reliability: Glass fiber material is stable, resistant to high temperatures (usually able to withstand over 500℃), corrosion-resistant, and non-combustible, making it suitable for extreme environments such as nuclear facilities and high-temperature processes.
- 2. Predictable Efficiency: Its efficiency does not decay over time, and in ULPA level (such asISO 75 U) applications, it can maintain an efficiency of over 99.999995% for a long time, making it the “stabilizing force” in semiconductor cleanrooms.
- 3. No Concerns about Electrostatic Decay: As an inorganic material, its performance is completely unaffected by humidity and time, with no risk of electrostatic failure.
Technical Limitations:
- 1. High Resistance and Energy Consumption: The dense fiber structure leads to higher initial resistance, increasing system operating energy consumption.
- 2. Brittleness and Handling Difficulty: The fibers are easily broken, requiring extra care during production, transportation, and installation, and recycling is difficult after disposal.
- 3. Potential Fiber Shedding: Under extreme airflow impact, there may be a small amount of fiber release, posing a risk to certain precision processes.
What is Melt-blown Polypropylene (PP)?
Technical Characteristics
Melt-blown PP is produced by stretching molten polypropylene into ultra-fine fibers (up to 1-3 microns in diameter) under the action of high-speed hot air, and directly forming the filter media on a receiving device. Its fibers are finer and more uniform, enabling the design of more complex gradient structures.
Core Advantages:
- 1.Excellent Low-Resistance Characteristics: By controlling the fiber thickness distribution, a gradient filtration can be achieved, where “coarse fibers on the surface intercept large particles, and fine fibers inside capture small particles,” significantly reducing airflow resistance.
- 2. Good Flexibility and Processability: Not easily damaged, excellent foldability, supporting more complex pleat designs to increase the filtration area. Can be included in plastic recycling streams after disposal.
- 3.Strong Hydrophobicity: Polypropylene itself is water-repellent, making it less prone to microbial growth in high-humidity environments, and the resistance increases slowly.
Technical Limitations:
- 1. Limited Temperature Resistance: Long-term operating temperature usually does not exceed 80-90℃, making it unsuitable for high-temperature applications.
- 2. Limited Chemical Resistance: Relatively weak resistance to some strong organic solvents.
- 3. Bottleneck of Pure Physical Efficiency: To achieve efficiency above H13/H14, a denser fiber structure is often required, which may offset its low-resistance advantage.
What are Electret Filter Materials?
Technical Characteristics:
Electret filter materials (mostly PP or PET treated with special processes) acquire persistent electrostatic charge through corona discharge, triboelectric charging, etc. Their filtration mechanism is a dual action of “physical interception + electrostatic adsorption,” which is particularly effective for fine particles of 0.1-1 micron.
Core Advantages:
- 1. Revolutionary “Low Resistance and High Efficiency”: This is the core advantage. Utilizing the long-range adsorption effect of electrostatic force, a relatively loose fiber structure can achieve extremely high initial efficiency (up to H13/H14 level) while maintaining extremely low initial resistance, resulting in significant energy savings.
- 2. Dominant in the Consumer Market: It almost dominates the household air purifier market, providing users with a quiet, energy-efficient, and highly effective overall experience.
Technical Limitations:
- Risk of Electrostatic Decay: A fatal weakness. High temperature, high humidity, organic vapors, and prolonged use can all lead to electrostatic decay, resulting in a decrease in filtration efficiency, especially the stability at ULPA levels is questionable.
- 2. Unpredictable performance: The long-term efficiency curve is unstable, making it difficult for these filters to become mainstream in industrial scenarios requiring long-term consistency (such as pharmaceuticals and semiconductor manufacturing).
- 3.Challenges in testing methods: TraditionalDOP/PAO test droplets may neutralize static electricity, resulting in test efficiency far lower than the actual initial efficiency in use, complicating performance evaluation.
Trenntech ‘s engineers believe that the future “heart” of filters will be intelligent, functional, and deeply integrated with specific applications. We may see: “smart filter materials” that automatically adjust porosity based on the level of contamination; and photocatalytic composite filter materials that can capture and decompose viruses. The goal of this competition is not replacement, but evolution—allowing each material to perform at its best, protecting humanity with cleaner and safer air with every breath.