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Systematic Solution to The Risk of Sticking Mold in TPU Injection Molding

TPU material is prone to abnormal adhesion with molds during injection molding due to its high molecular polarity, low shrinkage rate, and strong melt viscoelasticity. Reducing the risk of mold sticking requires collaborative efforts from three aspects: material modification, mold engineering, and process control, to construct a dual isolation mechanism of physics and chemistry at the nanoscale interface.

1,Die Interface Nanoengineering

1-1.Surface energy manipulation technology

·Superhydrophobic coating: DLC like diamond coating (thickness 1-3 μ m) reduces surface energy to 18-22 dyn/cm, TPU contact angle>105 °

·Fluorinated nano film: Plasma assisted deposition of PTFE composite film (0.2 μ m) to form a molecular level anti sticking barrier

1-2. Micro nano topological structure design

·Laser micro texture engraving of 20-50 μ m honeycomb pit array reduces actual contact area by up to 85%

·Electrochemical polishing achieves a mirror surface with Ra ≤ 0.02 μ m and eliminates micro mechanical locking points

2,Collaborative optimization of material formula

3,Precise control of injection molding process

3-1.Triple temperature regulation

·The temperature control of the rear section of the material cylinder is ≤ 180 ℃ (to suppress degradation and adhesion)

·Mold temperature gradient control: front mold 80-85 ℃/rear mold 40-45 ℃ (balanced crystallization and shrinkage)

·Cooling water temperature difference ≤ 3 ℃ (to avoid local sticking)

3-2.Stress timing management

·Adopting three-stage injection: A (low-speed filling 90%), B (micro speed shrinkage 5%), C (zero pressure holding 5%)

·The holding pressure is ≤ 30% of the initial injection pressure, and the time is shortened to 15% of the cooling time

3-3. Optimization of Demoulding Dynamics

·The ejection speed is divided into two stages: initial 0.5m/s (breaking through the adhesive layer) → subsequent 2m/s (rapid separation)

·Nitrogen assisted ejection: 0.4MPa equal pressure lifting, increasing contact area by 5 times.