High-frequency (HF) welding of TPU films: A Brief Description of Principles and Applications

I. Welding Principle
High-frequency (HF) welding utilizes a high-frequency electromagnetic field (typically 27.12 MHz) to excite polar groups (e.g., ester groups, ether bonds) in TPU molecules, causing rapid rotational friction and localized heat generation. The heat concentrates at the film contact interface, partially melting the material. After power shutdown, cooling solidifies the interface, forming molecular-level welds. Core advantages: High weld strength, small heat-affected zone, rapid efficiency, and no need for adhesives/solvents.

II. Welding Process

1. Material Compatibility: Both polyester-based TPU (heat-resistant) and polyether-based TPU (low-temperature resistant) are weldable; selection depends on application requirements.
2. Key Equipment:
   • HF generator: Provides stable electromagnetic field.
   • Electrode mold: Designed to match weld seam geometry.
   • Pressure system: Ensures tight film contact.
3. Procedure: Film positioning → HF heating activation → Pressure application → Cooling/solidification → Demolding and inspection.
4. Parameter Control: Adjust heating time, pressure, and power (no fixed values; optimized via trials) to balance weld strength and material deformation.

III. Key Applications

1. Medical: Sterile sealing for IV bags, blood bags, surgical gowns, etc.; HF welding ensures thin, high-strength seams compliant with medical standards.
2. Industrial: Waterproof membranes (tents, inflatable boats), airbag covers, electronics packaging – reliant on airtightness and weather resistance.
3. Consumer Goods: Athletic shoe air cushions, outdoor backpacks, inflatable toys – leverages lightweighting and waterproofing via HF welding.

IV. Technical Comparative Advantages

1. vs. Ultrasonic Welding: Superior for soft TPU with higher seam strength; eliminates mechanical vibration risks.
2. vs. Hot Plate Welding: Smaller heat-affected zone, faster cycle times; ideal for thin materials.
3. Limitations: Applicable only to polar polymers (e.g., TPU, PVC); non-polar plastics require pretreatment or alternative methods.