The Difference Between Hydrophilic and Hydrophobic Pleated Membrane Filters

In the field of industrial filtration, filter cartridges are the critical barrier safeguarding the purity of liquids and gases. Despite their small size, they embody sophisticated materials science. Today, we uncover a key characteristic determining filter performance: hydrophilicity and hydrophobicity. Consider industrial applications of pleated membranes, from ultrapure water for semiconductor cleaning to compressed air for pharmaceutical fermentation, and various acids, alkalis, and solvents – all rely on precision filtration. Pleated membrane filter cartridges, known for their large filtration surface area and high efficiency in particle retention, serve as the primary solution. But did you know that even among pleated filters, the core "membrane" can have vastly different "personalities" depending on the filtration task? This is primarily reflected in their "hydrophilic" and "hydrophobic" properties.

What Are They?

Imagine morning dew rolling off a lotus leaf, forming shimmering beads - this is a perfect display of hydrophobicity in nature. In simple terms, hydrophobicity means the material surface has a "repelling force" against water, resisting being wetted. Water molecules on such a surface strive to maintain their spherical shape, with a large contact angle.

Conversely, when a water droplet falls onto a clean glass slide, it spreads out quickly, making full contact with the surface. This phenomenon is hydrophilicity. Hydrophilic materials are very "friendly" to water molecules; there's a strong mutual attraction between their surface and water molecules, allowing easy wetting. In filtration, this "affinity or repulsion" property of the filter media directly determines whether it is best suited for handling liquids or gases.

How Do Hydrophilic and Hydrophobic Filters Work?

A hydrophilic filter acts like a "liquid pathway." When water or other aqueous solutions contact the hydrophilic filter membrane, the membrane allows the liquid to pass through smoothly while trapping suspended particles, bacteria (larger than the membrane pore size), and other contaminants. Its filtration targets are primarily various liquids, such as water, aqueous chemical reagents, pharmaceutical solutions, and beverages. Its advantage lies in its unobstructed liquid passage, typically featuring high flow rates, high dirt holding capacity, and a long service life.

In our Hongtek pleated membrane filter range, the HPT Series Hydrophilic PTFE Membrane Pleated Filters are an excellent representative of hydrophilic technology. The filter media in this cartridge uses high-quality hydrophilic Polytetrafluoroethylene (PTFE) microporous membrane. Driven by pressure, the liquid can directly wet and penetrate the membrane. The micropores on the membrane surface act like a fine sieve, retaining particles, bacteria, and other contaminants larger than its rated pore size, thereby producing clean liquid. Consequently, it is very suitable for filtering water, aqueous solutions, alcohols, photoresists, etchants, etc. It performs excellently in final liquid filtration and sterilizing-grade filtration within the electronics, food & beverage, and pharmaceutical industries.

Benefiting from the inherent properties of PTFE material and the hydrophilic modification, the HPT Series Filter Cartridges offer stable high filtration efficiency, high flow rates, long service life, and low pressure drop. Their broad chemical compatibility allows them to handle a variety of chemical reagents, and all materials comply with FDA regulations, making them suitable for the food and beverage industry.

A hydrophobic filter, on the other hand, acts like a "gas pass" and "liquid blocker." Due to its surface's water-repelling nature, liquids cannot spontaneously pass through its micropores. This means if a hydrophobic filter is immersed in water, the water is "blocked," while air and gases can pass freely.

This presents a core challenge: How can hydrophobic filters be used to filter liquids? Taking our Hongtek EPT Series Hydrophobic PTFE Membrane Pleated Cartridges as an example, these cartridges are made from naturally hydrophobic PTFE membrane. The working principle involves applying a sufficiently high external pressure to the cartridge itself to force the liquid to "squeeze through" the hydrophobic membrane network. This pressure must exceed the membrane's "breakthrough pressure." In practical applications, this is often used for specific membrane filtration processes where overcoming the resistance caused by its hydrophobic nature is necessary when filtering certain liquids.

Of course, the advantages of hydrophobic filters lie in their excellent chemical compatibility, outstanding temperature resistance, and ability to effectively block liquid water droplets, ensuring dry and pure gases. The EPT Series Filter Cartridges demonstrate excellent hydrophobic performance, along with exceptional chemical compatibility and temperature resistance, enabling them to handle harsh chemical environments and high-temperature sterilization processes. They are ideally suited for various gas filtration and venting applications, ensuring process gases are dry and sterile.

Conclusion

Finally, choosing between a hydrophilic or hydrophobic filter is not a simple either/or decision. It's about precise matching based on the physical state and chemical properties of the fluid being filtered. Understanding this "affinity relationship" is key to ensuring the efficient and stable operation of your filtration system. Whether you are processing a continuous stream of process liquids or require dry, clean compressed gases, manufacturers like Hongtek, which offer comprehensive hydrophilic and hydrophobic solutions, can tailor the most suitable filtration barrier for your needs.