TPU Football Shoe Soles

Asterism's TPU football shoe sole QC protocol is structured for high-volume OEM brand programs, covering raw material grade verification, injection process control, full sole assembly bond integrity, and batch traceability.

Material grade verification. Each TPU resin lot is verified by melt flow index (190°C / 10 kg, ASTM D1238), FTIR spectral fingerprint matching against the approved grade specification, and Shore D hardness check. Polyester and polyether grades are differentiated by FTIR carbonyl peak position and hydrolysis test pre-screening. Glass-fiber content is confirmed by ash test (ISO 3451-1) for reinforced grades. Resin is dried at 95–105°C for 4 hours to moisture below 0.03% before processing.

Injection process control. Barrel temperature is profiled across 5 zones (feed 165°C → nozzle 205°C) within ±3°C, and mold temperature is held at 40–55°C by a dedicated chiller. Injection speed, holding pressure (80–110 MPa), and cooling time are locked per cavity and logged by the machine's process data system. Shot weight is auto-weighed to ±0.3 g per cavity, and any out-of-tolerance shot is diverted. For full sole unit assembly, EVA midsole bonding uses corona-treated TPU surface (≥ 38 dynes/cm) and solvent-free PU adhesive at 4–6 bar press for 15–20 seconds.

Physical destructive testing (per batch, AQL 2.5).

• Hardness - Shore D durometer, 5 readings per sole, ASTM D2240.
• DIN abrasion - 40 m travel, 10 N load, DIN 53516.
• Flex resistance - Ross flex tester, 120,000 cycles at 22.5°, SATRA TM161.
• Stud pull-out and shear - universal testing machine, custom fixtures, 50 mm/min.
• Hydrolysis - jungle test chamber, 70°C / 95% RH, periodic inspection for cracking, tackiness, and peeling.
• Sole unit bond peel - TPU outsole to EVA midsole, 25 mm strip, 300 mm/min, ≥ 6 N/25 mm after 24 h cure.
• Dimensional accuracy - CMM, stud height ±0.2 mm, sole curvature ±0.5 mm, last-fit verification on 3 consecutive sizes.
• Color consistency - spectrophotometer ΔE ≤ 1.2 against approved master.
• Weight - electronic scale, per-cavity sorting, cavity-to-cavity variation ≤ 3%.

Chemical and regulatory testing. Finished soles are screened by GC-MS for REACH SVHC and ICP-OES for RoHS restricted elements. Full sole units with EVA midsole are additionally tested for total VOC and formaldehyde content where required by brand specifications. Batch traceability records link resin lot, mold cavity, production date, and test results to every shipped carton. Third-party SGS or Intertek reports are issued on request.

Equipment backing production stability. The plant operates 14 vertical injection molding machines (200T–400T), 8 desiccant dehumidifying dryers, 2 CNC mold centers, a CMM inspection station, a Ross flex tester, a jungle test chamber, 2 sole-unit bonding press lines, and an automated per-cavity weight sorter. This setup supports batch-to-batch hardness variation below 2 Shore D points and consistent sole-unit bond strength across high-volume OEM programs.