Thin Film Composite (TFC) hollow fiber membranes are essential for applications such as gas separation, water treatment, and wastewater purification. The increasing industrial demand for longer fibers necessitates a shift from laboratory-scale dip-coating methods to continuous coating techniques. The continuous coating process is crucial for achieving consistent and scalable application for both gutter and selective layers.
Transition from dip-coating to continuous coating can be achieved through the fine-tuning of critical parameters such as withdrawal speed, solution viscosity, and coating time, ensuring optimal coating uniformity and performance maintaining an optimal balance between permeance and selectivity to meet industrial requirements.
Dip coating to continuous coating
Dip coating is a simple method where a hollow fiber is immersed in a solution containing the coating
material and then withdrawn. A thin film adheres to the fiber and is cured by evaporating the solvent. This method allows for the preparation of very thin permeable layers by adjusting coating parameters and solution viscosity, but can only be used at laboratory scale. Its oftentimes challenging to achieve consistent coating quality on longer fibers or larger production volumes.
EMI Twente’s small scale Continuous Coating Setup:
- Features a 7-meter fiber path.
- A chimney for solvent evaporation
- Drying up to 60°C under N2 atmosphere.
- Winding capabilities.
EMI Twente’s role
EMI Twente played a key role in understanding our Thin Film Composite (TFC) hollow fiber membrane upscaling. With their expertise, we successfully transitioned from laboratory-scale dip-coating to a continuous roll-to-roll coating process.
Their team worked meticulously to fine-tune critical parameters such as withdrawal speed, solution viscosity, and coating time. This ensured uniform coating application for both gutter and selective layers, achieving the perfect balance between permeance and selectivity.
EMI Twente helped us to understand the requirements to allow further coating of our hollow fibers.
Emanuele Di Nicolò
Leader of the Polymer membrane labs & of the Advanced Separation Initiative
