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TPU waterproof film for footwear: 0.02–0.30mm, hydrostatic head 10,000–30,000mm, MVTR 5,000–15,000 g/m²/24h. Polyether vs. polyester data, HF welding parameters, delamination prevention, and factory QC standards from a TPU film factory.
TPU waterproof film is a thermoplastic polyurethane elastomer film extruded to thicknesses of 0.02–0.30mm, engineered for footwear waterproof lining applications with hydrostatic head ratings of 10,000–30,000 mm H₂O (ISO 811) and moisture vapor transmission rates (MVTR) of 5,000–15,000 g/m²/24h (ASTM E96-BW). Unlike expanded PTFE (ePTFE) membranes, TPU film is fully recyclable, resistant to detergent and hydrocarbon degradation, and compatible with high-frequency welding and heat-press lamination without additional adhesive layers. For footwear brands and assembly factories sourcing waterproof lining material, the critical procurement parameters are hydrolysis resistance (≥80% tensile retention after 5 weeks at 70°C / 95% RH), elongation at break (≥400%), and delamination resistance - all of which vary significantly between polyether-based and polyester-based TPU formulations.
Physical Properties: Hydrolysis & Elongation
The choice between polyether-based and polyester-based TPU is the single most consequential formulation decision in footwear waterproof film sourcing. Polyether TPU offers superior hydrolysis resistance and low-temperature flexibility; polyester TPU delivers higher tensile strength, oil resistance, and lower raw material cost. Polycaprolactone-based TPU occupies a balanced mid-tier position.
| Parameter | Polyether-Based TPU | Polyester-Based TPU | Polycaprolactone-Based TPU | Test Method |
|---|---|---|---|---|
| Thickness range | 0.02–0.20mm | 0.05–0.30mm | 0.05–0.25mm | In-line beta-ray gauge |
| Hydrostatic head | 10,000–20,000 mm H₂O | 15,000–30,000 mm H₂O | 12,000–25,000 mm H₂O | ISO 811 |
| MVTR (breathability) | 8,000–15,000 g/m²/24h | 3,000–8,000 g/m²/24h | 5,000–10,000 g/m²/24h | ASTM E96-BW |
| Tensile strength at break | 30–50 MPa | 40–60 MPa | 45–55 MPa | ASTM D412 Die C |
| Elongation at break | 500–700% | 400–550% | 400–500% | ASTM D412 Die C |
| Hydrolysis resistance (5 wk, 70°C/95% RH) | ≥90% tensile retention | ≥70% tensile retention | ≥85% tensile retention | ISO 105-S03 |
| Melting point | 100–160°C | 120–200°C | 130–180°C | DSC (ISO 11357-3) |
| Shore hardness | 70A–90A | 80A–98A | 85A–95A | ASTM D2240 |
| Low-temp flexibility | −50°C (no cracking) | −30°C (no cracking) | −40°C (no cracking) | ASTM D1003 cold flex |
| Oil / fuel resistance | Fair | Good | Very good | ASTM D471 (IRM 903, 70h) |
【💡 Sourcing Tip for Bulk Buyers】 Always specify hydrolysis grade and elongation minimums in your purchase order - not just thickness and width. A 0.05mm polyester TPU film with 400% elongation and ≥70% hydrolysis retention is not equivalent to a polyether film with 600% elongation and ≥90% retention. Solamni, a TPU film factory, provides a batch-specific Certificate of Analysis with every shipment. Request a free material sample swatchbook to compare formulations side by side.
Processing: High-Frequency Welding vs Heat Lamination
TPU waterproof film is bonded in footwear production via two methods: high-frequency (HF) dielectric welding for TPU-to-TPU seams (waterproof bootie construction), and heat-press lamination for TPU-to-fabric bonding (waterproof-breathable linings). The two methods are not interchangeable, and the film's melting point must match the chosen process.
| Parameter | High-Frequency (HF) Welding | Heat-Press Lamination |
|---|---|---|
| Bonding mechanism | Dielectric heating of TPU molecules (27.12 MHz) | Thermal conduction + pressure |
| TPU melting point requirement | 100–150°C (lower-melt preferred) | 120–180°C (10–20°C below film mp) |
| Typical film thickness | 0.08–0.20mm | 0.05–0.15mm |
| Bond peel strength | 8–15 N/25mm (cohesive failure) | 4–10 N/25mm (adhesive failure) |
| Cycle time per seam | 3–8 seconds | 15–30 seconds |
| Seam width | 2–5mm (precise die control) | 5–15mm |
| Seam hydrostatic head | ≥20,000 mm H₂O | ≥10,000 mm H₂O |
| Suitable substrates | TPU-to-TPU, TPU-to-PVC | TPU-to-mesh, TPU-to-T/C, TPU-to-leather |
| Primary footwear application | Waterproof bootie seam sealing | Lamination to shoe lining / upper |
| Equipment capital cost | $25,000–$80,000 (HF welder) | $5,000–$20,000 (heat press) |
Peel strength tested per ASTM D903 at 200 mm/min crosshead speed. Cohesive failure = film tears before bond fails; adhesive failure = bond separates cleanly.
HF welding creates a molecular-level bond (cohesive failure mode) because the 27.12 MHz electromagnetic field excites polar molecules in the TPU, generating internal heat that fuses the two film layers. This is the specified method for waterproof bootie construction - the inner sock that determines a shoe's waterproof rating. Heat-press lamination uses external thermal conduction to activate the TPU surface, bonding it to a fabric substrate. This method is used for waterproof-breathable linings where the TPU film is laminated to mesh or T/C fabric before upper assembly.
Processing windows must be controlled precisely. For HF welding: 27.12 MHz frequency, 2–5 kW power, 3–8 second weld time, 2–5 bar pressure. For heat lamination: platen temperature 130–160°C (always 10–20°C below the film's melting point to avoid film distortion), 3–5 bar pressure, 15–30 second dwell time. Corona treatment of the film surface to ≥38 dyn/cm is mandatory before heat lamination to ensure adequate peel strength.
Avoiding Delamination
Delamination - the TPU film separating from its substrate or a TPU-to-TPU weld failing - is the most common field failure in waterproof footwear. It is detectable before shipment with three incoming-QC tests and preventable by specifying the correct film grade and processing parameters.
| Delamination Mode | Root Cause | Detection Method | Corrective Action |
|---|---|---|---|
| TPU-to-fabric delamination | Insufficient corona treatment (<36 dyn/cm) | Corona dynamometer; peel test ASTM D903 | Specify corona ≥38 dyn/cm; verify per roll at winder |
| TPU-to-fabric delamination | Lamination temperature too low (<120°C) | Infrared pyrometer on heat-press platen | Increase platen temp to 130–160°C; verify with thermocouple |
| TPU-to-fabric delamination | Contaminated fabric surface (silicone, oil) | Contact angle measurement; water break test | Pre-treat fabric with plasma or solvent wipe before lamination |
| TPU-to-TPU HF weld delamination | HF power too low / weld time too short | Peel test; visual weld-line inspection | Increase power 10–20% or weld time 1–2 seconds |
| TPU-to-TPU HF weld delamination | Melting point mismatch (>30°C between film lots) | DSC test per film lot (ISO 11357-3) | Specify melting point tolerance ±10°C in PO |
| Hydrolysis-induced delamination | Polyester TPU used in humid / outdoor application | 5-week 70°C/95% RH aging (ISO 105-S03) | Use polyether TPU (≥90% retention) for outdoor / humid use |
| Flex-induced delamination | Film elongation <400% | SATRA TM60 flex test (50,000 cycles, −20°C) | Specify elongation ≥450% for footwear lasting |
| Thermal-cycling delamination | Poor low-temp flexibility (rated above −20°C) | ASTM D1003 cold flex; thermal cycling −30°C to +60°C | Use polyether TPU (rated −50°C) for cold-climate footwear |
The three incoming-QC tests that prevent 90% of delamination field failures are: (1) corona level verification at ≥38 dyn/cm using a corona dynamometer, performed on every roll before release to production; (2) melting point verification by DSC (±10°C of specification), performed on every resin lot; and (3) peel strength verification at ≥4.5 N/25mm for laminated film or ≥8 N/25mm for HF-welded film (ASTM D903), performed on the first production panel of each batch.
Factory Testing Standards
A qualified TPU film factory operates a documented QC protocol with defined test standards, sampling frequency, and acceptance criteria. The table below specifies the minimum test battery for footwear-grade TPU waterproof film.
| Test | Standard | Sampling Frequency | Acceptance Criterion | Equipment |
|---|---|---|---|---|
| Thickness | In-line beta-ray gauge | 100% (250 Hz sampling) | ±0.005mm (≤0.10mm); ±5% (>0.10mm) | Beta-ray thickness gauge |
| Tensile strength / elongation | ASTM D412 Die C | 1 sample per 1,000m | ≥30 MPa; ≥400% elongation | Universal tensile tester |
| Hydrostatic head | ISO 811 | 1 sample per 2,000m | ≥10,000 mm H₂O (polyether); ≥15,000 (polyester) | Hydrostatic head tester |
| MVTR | ASTM E96-BW | 1 sample per 5,000m | ≥5,000 g/m²/24h | MVTR environmental chamber |
| Hydrolysis resistance | ISO 105-S03 (5 wk, 70°C/95% RH) | 1 sample per production batch | ≥80% retention (polyether); ≥70% (polyester) | Environmental aging chamber |
| Corona treatment level | ASTM D2578 (dyne test) | Every roll at winder | ≥38 dyn/cm | Corona dynamometer / test inks |
| Melting point | DSC (ISO 11357-3) | 1 sample per resin lot | ±10°C of specified range | Differential scanning calorimeter |
| Peel strength (laminated film) | ASTM D903 | 1 sample per 2,000m | ≥4.5 N/25mm | 180° peel tester |
| Cold flex resistance | ASTM D1003 / SATRA TM60 | 1 sample per batch | No cracking at −20°C, 50,000 cycles | Flex tester + cold chamber |
| Color fastness to rubbing | ISO 105-X12 | 1 sample per color lot | Grade ≥4 (dry); ≥3 (wet) | Crockmeter |
Every shipment should carry a batch-specific Certificate of Analysis (CoA) summarizing test results, a REACH SVHC 233-substance declaration, RoHS 2.0 compliance statement, and a Safety Data Sheet (SDS). For brands requiring social compliance, the factory should hold SGS SMETA 4-pillar, BSCI, or Sedex membership, with audit reports available on request.
【Factory Assistance】Solamni New Material is a TPU film factory producing waterproof TPU film at 0.02–0.30mm with hydrostatic head 10,000–30,000 mm H₂O and MVTR 5,000–15,000 g/m²/24h. Polyether, polyester, and polycaprolactone formulations are available, with IATF 16949 and ISO 9001 certification. Every batch ships with a Certificate of Analysis and full QC test data. Review our quality control protocols or request a free material sample swatchbook for formulation comparison and processing trials.
FAQ
Q1: Which TPU formulation should I specify for waterproof hiking boots versus safety work boots?
Q2: What are the recommended high-frequency welding parameters for TPU waterproof film in footwear bootie construction?
Q3: What is the MOQ and lead time for TPU waterproof film, and does Solamni provide test reports with each shipment?
A3: Stock thicknesses (0.05, 0.08, 0.10, 0.15mm) ship in 3–5 working days, MOQ 500m. Custom formulation or color requires 12–18 working days, MOQ 2,000m. Every batch includes a Certificate of Analysis with tensile, hydrostatic head, MVTR, hydrolysis, and corona test data.
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Require immediate engineering consultation or custom specification development for upcoming footwear material programs? Contact our technical sales engineering team directly at ace01@eurus-cn.com or call +86 13459576329 for 24/7 technical support, physical swatchbooks, and direct factory quotation matrices.