| TPU Chemistry | Polyether or polyester TPU selected according to humidity, hydrolysis, oil, and abrasion exposure. | Polyether grades generally provide better hydrolysis resistance, while polyester grades often offer strong mechanical and abrasion performance. | Supplier technical data sheet, accelerated aging, hydrolysis, chemical resistance, and abrasion testing. | Confirm the exact polymer family and grade rather than accepting the general term “skin-friendly TPU.” |
| Hardness | Common starting range: approximately Shore A 70–95 for flexible wearable and soft-touch parts. | Hardness affects pressure, flexibility, comfort, deformation, and the risk of edge irritation. | Shore hardness testing according to ASTM D2240 or ISO 48-4, using controlled specimen thickness and conditioning. | Specify hardness tolerance, test method, specimen thickness, and acceptable lot-to-lot variation. |
| Surface and Skin Comfort | Smooth, non-abrasive surface with rounded edges and controlled surface texture. | Surface roughness, seams, flash, and sharp edges can increase friction, pressure points, and irritation. | Visual inspection, tactile assessment, dimensional inspection, and friction or abrasion evaluation where applicable. | Approve production-intent samples, including colorants, coatings, adhesives, printing, and final surface finish. |
| Biocompatibility | Risk-based evaluation for the intended contact type and duration; relevant ISO 10993 testing may include cytotoxicity, irritation, and sensitization. | A TPU described as non-toxic or skin-friendly is not automatically proven safe for every duration, user group, or application. | Biological evaluation plan, accredited laboratory reports, and finished-product testing where formulation or processing may affect results. | Request reports for the exact grade, color, additives, processing method, and final article—not only a generic resin declaration. |
| Chemical Compliance | Screen for restricted substances applicable to the destination market, including REACH SVHC requirements and RoHS where relevant. | Residual monomers, additives, pigments, plasticizers, heavy metals, and processing contaminants may affect safety and market access. | Supplier declaration supported by current chemical analysis, restricted-substance screening, and traceable test reports. | Define the destination countries and product category before issuing the specification and purchase order. |
| Moisture and Hygiene | Low moisture retention at the finished surface, with a design that can be cleaned and dried effectively. | Sweat, occlusion, and trapped moisture can contribute to discomfort and skin problems even when the polymer itself is well tolerated. | Water absorption testing, repeated cleaning or wipe testing, dimensional stability, and surface inspection. | Validate the complete product design, including vents, seams, closures, liners, and cleaning instructions. |
| Mechanical Durability | Requirements should be defined for tensile strength, elongation, tear strength, compression set, and abrasion according to the application. | Cracking, tackiness, permanent deformation, or surface wear can expose rough areas and shorten safe service life. | ASTM or ISO mechanical testing, cyclic flexing, compression-set testing, abrasion testing, and aging simulation. | Set measurable acceptance criteria and compare samples after heat, humidity, sweat, UV, and cleaning exposure when applicable. |
| Colorants and Additives | Use documented pigments, stabilizers, lubricants, and other additives suitable for the intended contact and market. | The finished color or additive package can change chemical exposure, migration behavior, odor, and biocompatibility results. | Full formulation disclosure under confidentiality controls, migration or extractables assessment, and finished-part screening. | Do not substitute colorants, masterbatch, regrind, or additives without written approval and requalification. |
| Manufacturing Controls | Controlled drying, molding temperature, residence time, cleanliness, lot traceability, and documented change management. | Processing conditions can influence degradation, odor, surface defects, residuals, and final mechanical properties. | Process audit, batch records, incoming inspection, certificate of analysis, and retained production samples. | Include lot number, manufacturing date, shelf life, packaging requirements, and notification periods for formulation changes. |
| Documentation and Import Readiness | Technical data sheet, safety data sheet, certificate of analysis, compliance declarations, test reports, and product specification. | Complete documentation supports risk assessment, customer approval, customs review, and post-market traceability. | Document review against the final application, destination-market rules, and purchasing specifications. | Ensure documents identify the exact grade, revision date, test standard, laboratory, sample description, and validity period. |
| Sampling and Qualification | Use a staged process: document screening, material samples, production-intent prototypes, laboratory testing, and pilot-lot approval. | Performance and skin-contact behavior can differ between raw pellets, molded plaques, and finished multi-material products. | Pre-production approval, independent verification testing, accelerated aging, and periodic requalification. | Approve the complete supply chain and maintain a change-control process for material, tooling, color, and manufacturing-site changes. |