Introduction

Hydrophilicity—the ability of a membrane to attract and interact with water—plays a critical role in filtration performance. Whether a membrane is hydrophilic or hydrophobic determines how easily fluids wet the surface, how the membrane handles aqueous or organic solutions and how quickly filtration can begin. This article explains how hydrophilicity shapes filtration behavior and why it is essential for choosing the right membrane.

1. What Is Hydrophilicity?

Hydrophilicity refers to how well the membrane surface absorbs and interacts with water. Hydrophilic membranes allow water to spread easily across the surface, while hydrophobic membranes repel water and require pressure or pre-wetting.

• Hydrophilic = water-attracting
• Hydrophobic = water-repellingli>

2. How Hydilicity Affectsting and Start

The most immediate impact of hydrophil is on membrane wetting.

• Hydrophilic: instantly wets, filtration starts immediately
• Hydrophobic membranes: require pre-wetting with alcohol or high pressure

This is why PES and MCE are widely used for aqueous filtration.

3. Flow Rate Behavior in Aqueous Filtration

Hydrophilicity significantly changes flow characteristics:

• Hydrophilic membranes: lower resistance and faster flow in water-based samples
• Hydrophobic membranes: high resistance unless fully pre-wet

The difference is especially visible in vacuum-driven filtration.

4. Solvent Compatibility and Chemical Behavior

Hydrophilicity also influences how membranes interact with solvents and chemicals:

• Hydrophobic membranes: ideal for strong organic solvents (PTFE)
• Hydrophilic membranes: better for aqueous buffers and biological samples

This is why hydrophobic PTFE is the standard for aggressive solvent filtration.

5. Influence on Air and Gas Filtration

Hydrophilic membranes block gas when wet, while hydrophobic membranes allow air to pass freely.

• Hydrophilic: act as liquid barriers
• Hydrophobic: used for venting and gas filtration

Hydrophobic PVDF and PTFE are commonly used in vent filters and air monitoring.

6. Interaction with Proteins and Biological Samples

Surface chemistry changes how samples bind to the membrane:

• Hydrophilic membranes: lower protein binding, ideal for biological work
• Hydrophobic membranes: may increase adsorption of biomolecules

PES is often selected for low-binding applications.

7. How to Choose: Hydrophilic vs Hydrophobic

• Aqueous filtration: use hydrophilic PES, Nylon or MCE
• Organic solvents: choose hydrophobic PTFE
• Venting or gas filtration: hydrophobic PTFE or PVDF
• Biological samples: hydrophilic PES for minimal protein loss

Selecting the correct surface property is as important as selecting pore size.

Conclusion

Hydrophilicity shapes almost every aspect of membrane performance—from wetting and start-up behavior to flow rate, chemical compatibility and sample binding. Understanding the difference between hydrophilic and hydrophobic membranes ensures more accurate results and more reliable filtration workflows.

Purchase Suggestion

We offer hydrophilic and hydrophobic membranes optimized for both aqueous and organic filtration. Contact our technical specialists for tailored recommendations.