Ensuring the airtightness of the lumbar support airbag is the key to ensuring its normal function, extending its service life and ensuring the safety of the user. The following systematically explains the specific measures from the aspects of materials, design, manufacturing, testing and maintenance:
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1. Material selection and quality control
Select high airtightness materials
TPU (thermoplastic polyurethane): wear-resistant, oil-resistant, good elasticity, and can balance flexibility and support by adjusting the hardness (such as 85A-95A).
PVC composite materials: low cost, but plasticizers need to be added to improve flexibility, and attention should be paid to plasticizer migration.
Rubber-coated fabrics: such as chloroprene rubber (CR) coated nylon, which has both strength and sealing properties and is suitable for high-pressure environments.
Material performance test
Tensile strength: ≥20MPa (TPU), to ensure that it does not deform after inflation.
Tear strength: ≥50kN/m, to prevent rupture when the airbag is inflated.
Airtightness test: According to ASTM D1434 standard, the material permeability is ≤0.1cm³/(m²·24h·atm).
2. Structural design and optimization
Reduce stress concentration
Rounded transition: airbag edge R≥5mm to avoid local high-pressure rupture caused by right angles.
Rib design: Add longitudinal or transverse ribs in the inflation area to improve the pressure resistance.
Nozzle and connector design
One-piece nozzle: Use TPU to heat-seal with the airbag body to reduce the risk of leakage.
Quick connector: Use metal or high-strength plastic connectors with O-rings to ensure the connection is tight.
Multi-layer composite structure
Outer layer: wear-resistant TPU, scratch-resistant.
Middle layer: high-strength nylon fabric, providing structural support.
Inner layer: low-friction TPU, reducing inner wall friction during inflation.
III. Manufacturing process control
High-frequency heat-sealing process
Parameter optimization: High-frequency machine frequency is 27.12MHz, and the power is adjusted according to the material thickness (such as 8-10kW for 1.5mm TPU).
Mold design: Use a mold with cooling water channels to control the heat-sealing temperature at 180-200℃ to avoid material degradation.
Air nozzle welding process
Ultrasonic welding: frequency 20kHz, amplitude 50-70μm, welding time 0.5-1s, ensure that the air nozzle and the airbag body are fused.
Pressure test: After welding, inflate to 1.5 times the working pressure, maintain pressure for 30 seconds, leakage ≤0.1cm³/min.
Cleaning and pollution prevention
Dust-free workshop: Control the cleanliness of the workshop to ISO Class 7 to avoid micro-leakage caused by dust particles.
Mold release agent selection: Use silicone oil-based mold release agent, the residual amount is ≤0.5mg/m².
IV. Quality inspection and verification
Air tightness test
Pressure decay method: Inflate to the rated pressure (such as 0.2-0.3MPa), maintain pressure for 24 hours, and the pressure drop is ≤2%.
Helium mass spectrometer leak detection: sensitivity reaches 1×10⁻⁹ Pa·m³/s, detects tiny leaks.
Durability test
Cyclic inflation and deflation: According to ISO 16840-4 standard, there is no leakage after 50,000 cycles.
High temperature and humidity test: Placed in 85℃/85%RH environment for 168 hours, the airtightness retention rate is ≥95%.
Destructive test
Burst pressure test: Record the pressure when the airbag ruptures (usually ≥3 times the working pressure).
Tear extension test: Apply tension at the pre-cut and record the tear extension length.
V. Usage and maintenance recommendations
Installation specifications
Avoid contact with sharp objects: Use a protective cover to cover the surface of the airbag during installation.
Fixed method: Use Velcro or buckle to fix to avoid glue corrosion of materials.
Daily maintenance
Regular inspection: Visually check the airbag surface for wear or scratches every month.
Cleaning method: Wipe with a damp cloth and avoid using organic solvents.
Troubleshooting
Leak repair: Small area damage can be repaired with TPU patch heat seal.
Replacement standard: Replace when obvious deformation occurs or pressure drops by more than 10%.
VI. Case Analysis
A car seat manufacturer: By optimizing the TPU material formula (adding 10% nanoclay), the air tightness is improved by 30%, and the number of durability test passes is increased from 30,000 times to 50,000 times.
A medical lumbar support brand: adopting a three-layer composite structure, the bursting pressure is increased from 0.8MPa to 1.2MPa, and the user complaint rate is reduced by 60%.
Through the above measures, the air tightness of the lumbar support airbag can be systematically guaranteed to meet the stringent requirements for safety and reliability in the automotive, medical and other fields.