● High viscosity dope: Requires larger flow channels to reduce resistance, ensure stable extrusion, and enable stable hollow fiber formation. Larger orifices also reduce residence time, mitigating thermal degradation.
● Gen 4: Stepped needle with dowel-pin positioning.
● Gen 5: Independent spinning insert, pinless; ~80% lower maintenance cost.
● Gen 6: Independent feed control per channel.
● Gen 7: Screwless and pinless; size reduced by ~50%.
● Gen 8: On-line, non-stop insert changeover.
● Flow-path design: TIPS emphasizes insulation and anti-freezing/solidification, often with heating jackets; NIPS emphasizes precise bore/shell flow control and mixing.
● Bore fluid needs: NIPS usually requires a bore fluid (e.g., water or non-solvent) to support the lumen; some TIPS systems can self-support without a bore fluid.
● Orifice and finish: TIPS handles higher viscosity dopes; orifices are often larger with higher surface finish to reduce hang-up.
● TIPS (thermally induced phase separation): Melt or high-concentration solution cooled to form membrane; suitable for high temperature polymers (PP, PE, PVDF).
● Dry–wet spinning: Combines air gap (dry zone) with coagulation bath (wet zone) for enhanced structure control.
● Co-extrusion composite spinning: Produces multilayer or functional hollow fibers (e.g., liner-reinforced).
● Melt spinning: Polymer pellets melted and extruded through the hollow fiber spinneret, solidifying in air to form fibers.
● Alignment: Precisely align the hollow fiber spinneret with coagulation bath and take-up to ensure vertical fiber fall.
● Connect lines: Correctly connect bore fluid and shell dope (or single dope) feeds; ensure leak-free seals.
● Preheat and degas: Preheat to process temperature before feeding and purge all trapped air.
● Trial run and tuning: Start at low flow; observe filament formation (breakage, eccentricity, bubbles), then gradually adjust bore/shell flow ratio, temperatures, and take-up speed to stable operation.
● Operating temperature and pressure: Excessive temperature or pressure can cause deformation or fatigue. As a rule of thumb, <260°C and ≤10 bar generally have no adverse effect on stainless steel hollow fiber spinnerets.
● Cleaning and maintenance: Improper cleaning (e.g., scraping with hard tools) or frequent disassembly can damage sealing faces and compromise concentricity in Gen-1–4 designs; FCT Gen-5 is less affected.
● Material selection: Premium stainless steel or specialty alloys offer better corrosion and wear resistance, extending service life.
● Run continuity: Frequent starts/stops can cause dope to solidify or clog; improper cleaning thereafter will damage and shorten service life.
About Trustech