Analysis of Material Technology for Hepa Air Filters

The material technology of high-efficiency air filters can be seen as a precise system engineering from the surface to the inside. Its quality depends not only on the core filter material, but also on the synergistic effect of auxiliary materials such as sealants, separators, and frames. Below, I will start with these four core components to provide you with a detailed technical analysis.

• The filter material is the "heart" of the filter, directly determining the filtration efficiency, resistance, and service life. At present, the mainstream high-efficiency filter materials mainly include the following two types, which have significant differences in technical characteristics:
• Ultra fine glass fiber filter paper
• Core technical principle: Made of alkali free glass fiber with extremely fine diameter through wet forming process. The fibers are evenly distributed, forming dense and tortuous channels, mainly relying on inertial collision, interception, and diffusion effects to capture particles.
• Key performance characteristics:
• High efficiency and stability: It has a stable high capture efficiency for particles of 0.1-0.3 μ m, and the efficiency does not decay over time.
• Large dust holding capacity: The internal pore structure is well-developed, which can accommodate a large amount of dust and has a long service life.
• Temperature and corrosion resistance: Temperature resistance can reach 250 ℃ -400 ℃, acid and alkali resistance, strong adaptability.
• Brittle: The material is relatively brittle and not resistant to bending, so caution should be taken during operation.
• Typical application scenarios: General cleanrooms, pharmaceuticals, biosafety, general electronics factories, and most other occasions.
• PTFE (polytetrafluoroethylene) composite filter paper
• Core technology principle: PTFE resin is stretched and expanded to form a microporous membrane, which is composite on the substrate. Mainly relying on surface filtration mechanism, particles are intercepted on the membrane surface to achieve "one-time separation".
• Key performance characteristics:
• Extremely high filtration accuracy: separation accuracy can reach 0.01 μ m-0.3 μ m, surface filtration, less prone to deep blockage, and slow resistance growth.
• Strong chemical stability: inert material, resistant to strong acid and alkali, wear-resistant, and aging resistant (-180 ℃~260 ℃).
• Easy to clean dust: The surface is smooth, and dust is not easy to adhere, suitable for pulse back blowing cleaning.
• Typical application scenarios: Microelectronics, semiconductors, chip manufacturing, and other fields that require extremely high cleanliness, as well as highly corrosive gas environments.
• Frontier dynamics: The scientific research field is developing new composite filter materials, such as combining basalt fiber with biomass fiber. While improving the strength and heat resistance of the filter material, functional materials (such as ZIF-8) are grown on the surface to enable it to capture harmful gases and have multiple functions of antibacterial.

• If the filter material is responsible for "filtering", then the sealing material is responsible for "plugging" to prevent unfiltered air from bypassing the edge of the filter material. This is the key to ensuring that the overall efficiency of the filter reaches the H13/H14 level.
• PU Sealants
• Main technical function: Used for bonding and filling filter paper and frames. High quality polyurethane adhesive (such as HJ-1721) has excellent bonding strength, elasticity, and aging resistance, which can absorb the stress of thermal expansion and contraction without cracking, ensuring long-term leak free performance.
• Example of core performance parameters: tensile strength ≥ 0.7 MPa, adhesive strength ≥ 0.6 MPa, operating temperature -60 ℃ to 120 ℃, and possessing anti mold properties.
• sealing strip
• Main technical function: Installed on the outer frame of the filter, used for static sealing between the filter and the installation frame.
• Example of core performance parameters:
• Chloroprene rubber: universal type, temperature resistant to 80 ℃.
• Polyurethane foam strip: good elasticity, small compression deformation, commonly used in non partition filters.
• Silicone strip: used for high temperature (260 ℃) applications.
• Jelly glue (liquid tank glue): used for sealing filters in liquid tanks, it has excellent fluidity and can achieve blade insertion sealing, with excellent sealing effect.

• The function of the separator is to maintain the gap between adjacent filter papers after folding, forming a smooth airflow channel.
• Hot melt adhesive line
• Main technical function: Used for non partition filters. Apply on the crease when folding the filter paper, and provide support after curing. The technical key lies in the uniform height of the adhesive points to ensure the uniformity of the airflow channel and reduce resistance.
• partition board
• Main technical function: Used for filters with partitions.
• Aluminum foil partition: high strength, high temperature and humidity resistance, will not shrink or release particles due to temperature and humidity changes.
• Paper partition (laminated paper/kraft paper): Low cost, but attention should be paid to the possibility of shrinkage or particle formation during large temperature and humidity fluctuations.

• The framework provides structural support for fragile filter paper and ensures that the filter can be securely installed in the system.
• Common materials
• Aluminum alloy profiles: the most commonly used, with a corrosion-resistant surface after anodizing treatment, light weight, and good strength.
• Galvanized steel plate: high strength, mostly used in situations with high air volume or requiring higher structural strength.
• Stainless steel plate: used in environments with extremely high cleanliness levels or special requirements for corrosion resistance and cleaning resistance.
• Wooden/multi-layer panel frame: Low cost, but poor moisture and deformation resistance, prone to mold growth, should be avoided in high-end cleanrooms.
• Technical key point: The framework must have sufficient rigidity to ensure that it does not deform during transportation, installation, and long-term operation. Any slight distortion can cause the sealing of the frame to fail, resulting in leakage.

The material technology of high-efficiency air filters is a precision system composed of core filter materials, sealing systems, internal supports, and external frames.
The filter material determines the upper limit of filtration performance.
The sealant and rubber strip ensure that the performance is exerted without leakage.
The partitions and frames ensure the stability and long-term reliability of the structure.
Understanding the technical characteristics and interactions of these materials is the core prerequisite for correctly selecting, using, and maintaining efficient filters to ensure a dust-free and clean environment.