TPU (Thermoplastic Polyurethane) is a high-performance material that combines the mechanical strength of plastics with the elasticity of rubber. Characterized by high elasticity, wear resistance, waterproof and breathable properties, weather resistance, and eco-friendliness, TPU films are widely used in sectors such as apparel fabrics, industrial sealing, medical consumables, automotive interiors, and electronic packaging. They are available in customizable hardness levels to meet diverse composite molding requirements.
There are currently three main processing methods for TPU films:
1. Cast film process: Uses high-precision T-die extrusion to produce films with a smooth, clear surface and uniform thickness; it is the preferred choice for high-end waterproof, breathable films and composite substrates.
2. Blown film process: Offers superior cost-effectiveness and high toughness due to biaxial stretching; commonly used for elastic packaging, airbag films, and similar applications.
3. Calendering process: Suitable for thicker TPU sheets with excellent flatness; frequently used for wear-resistant liners, industrial sheets, and the like.
Common issues and solutions regarding TPU film processing are summarized below:
1. Issue: Air bubbles on the film surface. Causes: ① High moisture content in TPU pellets; ② Excessive processing temperature.
Solutions: ① Thoroughly dry the raw material to keep moisture content below 0.03%; ② Appropriately lower the processing temperatures across the barrel zones.
2. Issue: Unmelted particles or "fish eyes" (gel specks) on the surface. Causes: ① Incomplete melt plasticization; ② Localized crystallization in the die head (presence of cold material); ③ Impurities in the raw material.
Solutions: ① Increase the plasticization temperature appropriately and use a screw specifically designed for TPU; ② Raise the die head temperature to purge the material, then lower it to the appropriate operating temperature; ③ Install an 80–120 mesh screen to filter out impurities.
3. Issue: Uneven film thickness. Causes: ① Non-uniform die gap; ② Significant fluctuations in die head pressure; ③ Unstable haul-off speed. Solutions: ① Calibrate the die gap across its entire width; ② Use a melt pump to maintain stable pressure; ③ Employ a closed-loop speed control system to ensure a constant haul-off speed.
4. Common Issue: Surface flow lines or streaks. Cause Analysis: ① Dead zones with material buildup in the die flow channel; ② Improper die head temperature; ③ Excessive moisture content in the raw material.
Solutions: ① Disassemble and clean out residual material from the die flow channel, or purge the channel by raising the temperature; ② Adjust the die head temperature to the appropriate range; ③ Thoroughly dry the raw material (including any masterbatch or regrind).
5. Common Issue: Yellow/black impurities or black specks. Cause Analysis: ① Carbonized material deposits on the screw or die head; ② Excessive processing temperature causing localized thermal decomposition of the TPU; ③ Contamination by foreign impurities.
Solutions: ① Regularly clean the barrel, screw, and die head; ② Lower the processing temperature appropriately to prevent localized overheating; ③ Inspect the raw material packaging before opening and implement dust-prevention measures during the feeding process.
6. Common Issue: Screen Clogging. Causes: ① Excessive impurities in raw materials rapidly accumulate on the screen surface; ② Screen mesh size is too fine, overloading the filtration capacity per unit area; ③ Localized low melt temperatures create high-viscosity clumps that quickly clog the mesh; ④ Hard carbonized particles resulting from thermal degradation rapidly block the screen. Solutions: ① Improve raw material pretreatment; if using regrind, minimize or eliminate material with high impurity content; ② Select an appropriate screen mesh combination (40–120 mesh) based on material properties to avoid excessively fine mesh; ③ Adjust barrel and die temperatures to ensure uniform melt plasticization and eliminate localized low-temperature, high-viscosity melt; ④ Lower processing temperatures slightly to reduce material degradation; replace the screen promptly if pressure exceeds normal levels by 15%.
7. Common Issue: Rough, Dull Film Surface. Causes: ① Insufficient plasticization temperature; ② Low die head temperature; ③ Improper cooling rate. Solutions: ① Increase plasticization temperature; ② Increase die head temperature to ensure melt flowability; ③ Adjust cooling water temperature to the appropriate level.
8. Common Issue: Film Blocking (Sticking) During Winding. Causes: ① Excessive melt temperature at the die exit; ② Inadequate cooling and setting of the film.
Solutions: ① Lower the melt temperature at the die exit; ② Improve the cooling efficiency of the chill roll; ③ Add an appropriate proportion of TPU-specific anti-blocking agent.
To be continued...
Yantai Leo New Materials offers high-quality TPU films at reasonable prices. We welcome your inquiries and orders!
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