Structure and Mechanical Properties of an Injection‐Molded Thermoplastic Polyurethane as a Function of Melt Temperature

Abstract

Abstract Thermoplastic polyurethanes (TPUs) molded at 205, 215, and 235 °C are monitored by SAXS and WAXS during straining. A non‐affine nanostructure deformation and related evolution mechanisms are found. DSC and microscopy are applied. DSC shows two melting endotherms. The results indicate that melts kept below the second peak stay phase‐separated. The orientation parameter f ( ϵ ) and d f /d ϵ from WAXS are related to chain orientation mechanisms (strain ϵ ). SAXS shows hard domains that are only correlated to a next neighbor (“sandwich”). Thick sandwiches lengthen more than thin ones. Thin‐layer sandwiches feature a strain limit. Some are converted into thick‐layer sandwiches. Two materials have tough hard domains. Material processed at 235 °C is soft and contains weak hard domains that fail for ϵ > 0.75.