Negative Enthalpy Variation Drives Rapid Recovery in Thermoplastic Elastomer

Area of Science:

• Materials Science
• Polymer Science
• Mechanics of Materials

Background:

• Resilience in polymeric materials is often explained by entropy elasticity, neglecting enthalpy variation (ΔH).
• This model inadequately explains reduced resilience in long-range stretchable thermoplastic polyurethane (TPU) due to physical crosslink network dynamics.
• Undesirable reduction in TPU resilience limits its application in long-range stretchable scenarios.

Purpose of the Study:

• To enhance the resilience of long-range stretchable thermoplastic polyurethane (TPU).
• To investigate the role of negative enthalpy variation (ΔH) in improving TPU recovery.
• To design TPU with superior resilience for demanding applications.

Main Methods:

• Constructed a reversible interim interface in TPU using strain-induced phase separation.
• Introduced a negative enthalpy variation (ΔH) effect to improve material recovery.
• Analyzed structural factors influencing resilience, including soft segment symmetry and hard segment content.

Main Results:

• Achieved resilience efficiency exceeding 95% in the newly developed dual soft segmental TPU.
• Demonstrated resilience comparable to biomaterials and superior to many synthetic high-performance TPUs (typically <80%).
• Observed a remarkable hysteresis loop ratio exceeding 50%, indicating significant energy dissipation and recovery.

Conclusions:

• The negative ΔH effect, facilitated by strain-induced phase separation, significantly improves long-range stretchable TPU resilience.
• The developed TPU exhibits high resilience and hysteresis, making it suitable for applications like artificial ligaments and buffer belts.
• Understanding structural factors like segment symmetry and content is crucial for designing advanced resilient elastomers.