A brief description of the high-frequency welding process and performance of multi-layer co-extruded TPU calendered film

Multi-layer co-extruded TPU calendered film, combined with high-frequency welding technology, achieves a balance between material performance and processing efficiency through functional layering design and molecular-level fusion. Its products possess wear resistance, weather resistance, and environmental friendliness, and are widely used in medical, industrial, and consumer electronics fields, becoming an ideal alternative to traditional materials.

I. Process Flow

1. Raw Material Selection and Co-extrusion Molding

Polyester or polyether-based TPU granules are used, with the formulation adjusted according to application requirements. Polyester-based granules offer superior heat resistance and chemical corrosion resistance, making them suitable for industrial applications; polyether-based granules offer stronger low-temperature resistance and hydrolysis resistance, making them suitable for outdoor or humid environments. Multiple extruders converge TPU melts with different functions into a single die, forming a multi-layer structure (e.g., an outer wear-resistant layer, a middle reinforcement layer, and an inner sealing layer). Co-extrusion technology enables functional layering to meet diverse needs. Molten TPU is extruded into continuous sheets through calendering rollers, resulting in high process efficiency suitable for large-scale production.

2. High-Frequency Welding Process

High-frequency current is used to generate polarized friction between TPU molecular chains, instantly heating them to their melting point, achieving molecular-level fusion. Short welding time, small heat-affected zone, and avoidance of material deformation. Complex shape welding (such as irregularly shaped bags and three-dimensional structures) can be achieved through mold design, combined with air pressure to ensure the weld strength is consistent with the film.

II. Performance Advantages

1. Excellent Physical Properties

Abrasion and Impact Resistance: TPU film combines high strength and high elasticity, resisting friction and impact for a long time, suitable for sports shoe materials, automotive interiors, etc.

Weather Stability: Wide temperature range, good flexibility at low temperatures, and does not easily soften at high temperatures; outdoor products do not age or crack after long-term use.

Environmentally Friendly and Biodegradable: Non-toxic when burned, biodegradable in soil, meeting the environmental requirements of medical and food packaging.

2. Outstanding High-Frequency Welding Performance

Strong Sealing: Weld strength is close to that of the base material, and airtightness is superior to traditional bonding, meeting medical-grade sterilization requirements.

High Efficiency and Low Cost: Welding speed far exceeds hot plate welding, energy consumption is low, and fully automated production is supported, significantly increasing production capacity.

Flexible Design: Supports multi-layer co-extrusion of transparent and matte finishes, combined with high-frequency welding to create highly transparent windows or complex three-dimensional structures.

III. Application Scenarios

1. Medical Field

Biofluid Bags: Utilizes antistatic and antibacterial co-extruded films, high-frequency welded to create blood bags or dialysis fluid bags, resistant to low-temperature transportation and reliably sealed.

Medical Dressings: Ultra-thin TPU film composited with non-woven fabric, welded edges form breathable and waterproof dressings, reducing the risk of clinical infection.

2. Industrial and Outdoor Applications

Flexible Storage Tanks: Multi-layer co-extruded films welded into large storage tanks, resistant to chemical corrosion, with a lifespan far exceeding traditional materials.

Inflatable Toys: Transparent TPU films welded into floating rafts, strong load-bearing capacity and safe, non-toxic.

3. Consumer Electronics

Mobile Phone Cases: Co-extruded TPU films welded into rugged shells, balancing protection and signal penetration.

Wearable Devices: Ultra-thin TPU films welded with sensors to create breathable and comfortable smart bracelet straps.