High-Strength Heat-Elongated Thermoplastic Polyurethane Elastomer Consisting of a Stacked Domain Structure

Abstract

We found that a high-strength elastomer was obtained by the heat elongation of a thermoplastic polyurethane (TPU) film consisting of a high content of crystalline hard segments (HS). The stress upturn continuously increased with the elongation ratio without a decrease in the strain recovery by heat elongation, i.e., the stress at break of a quenched TPU film was increased from 55 to 136 MPa by heat elongation at an elongation ratio of 300%. The results of small-angle X-ray scattering, DSC, and AFM observations revealed that: (1) anisotropically shaped HS domains were stacked at a nanometer scale and the longer direction of the HS domains was arranged perpendicular to the elongated direction due to the heat elongation, (2) the densification of the HS domains increased with increases in the elongation ratio without a significant increase in the crystallinity, and (3) the stacked domain structure remained during the stretching at 23 °C. Thus, the strengthening of the elongated TPU might be attributed to the densification of the HS domains in the stacked structure, which prevents the fracture of the HS domains during the stretching.

Thermoplastic Azobenzene Polyurethanes with Both Efficient Photomediated Migration and Excellent Mechanical Strength

“…Another feature of the stress–strain curves in Figure S3 is the stress upturn for azo TPU06 and azo TPU03. Stress upturn is a result of limited chain extensibility under external force, − for TPU the soft chain between hard microdomains is fixed and gradually reaches the limit of extensibility under external force. For stress upturn to develop, the hard phase must be strong and stable under external force, if the hard phase disassembles or reorganizes under external force, the stress would be released and negligible or no stress upturn could be observed.…”

Preparation of polyborosiloxanes with systematically changed mechanical properties and correlation of their structure/property relationship

“…Another feature of stress–strain curves in Figure 8a is the upturns before fracture. Stress upturn is known to improve material toughness and has been observed for different elastomers such as polyurethane, 49–51 natural rubber 52 and multimodal silicone rubbers 53 . In these networks stress upturn at high strain is due to the non‐Gaussian statistics of chain at large deformability 39 .…”

Strength Enhancement of Aliphatic Polyurethane Film by Solution Annealing

“…Polyurethane elastomer (PU) has attracted more and more attention due to its excellent optical properties, water resistance, and endurance depending on its microphase separation structure between the soft and hard domain. − Based on this, PU has been widely used in automobile windshields, military engineering, aerospace, and other fields. − Several methods have been reported to enhance the strength and bearing capacity of PU, because of its application need. − Sacrificial bondsare has been introduced to improve the mechanical properties and toughness of PU. − A transparent degradable polyurethane elastomer (PHI) with excellent fracture strength and toughness was successfully prepared, in which energy was dissipated by using imidazolidinyl urea (IU) as a multihydrogen bond motif . The mechanical strength and elasticity of PU crosslined with pseudorotaxane (PS) were significantly improved by the effective cooperation of the ring sliding effect and hydrogen bond stacking network .…”