Investigation of Shape Memory Polyurethane Properties in Cold Programming Process Towards Its Applications.

Area of Science:

• Materials Science
• Polymer Science
• Mechanical Engineering

Background:

• Thermoresponsive shape memory polymers (SMPs) offer shape recovery triggered by temperature changes.
• Traditional 'hot-programming' involves heating SMPs above their glass transition temperature (T), reshaping, and cooling, which can cause thermal degradation and limit applications.
• Limitations of hot-programming include temperature gradients, thermal expansion, and reduced shape recovery properties, hindering use in demanding fields.

Purpose of the Study:

• To investigate the cold programming approach for thermoplastic polyurethane shape memory polymers (PU-SMPs).
• To evaluate the structural, mechanical, and thermomechanical properties of PU-SMPs using cold programming.
• To determine the shape fixity and shape recovery ratios of PU-SMPs programmed at temperatures below T.

Main Methods:

• Comprehensive experimental investigation of thermoplastic polyurethane shape memory polymer (PU-SMP).
• Utilized the 'cold programming' approach, deforming the SMP below its glass transition temperature (T ≈ 65 °C).
• Performed structural, mechanical, and thermomechanical characterization to assess functional properties.

Main Results:

• Cold programming at room temperature yielded a shape fixity ratio of approximately 90% and shape recovery of 93%.
• Cold programming at 45 °C (T - 20 °C) resulted in a shape fixity ratio of approximately 97% and shape recovery of 90%.
• Compared to hot programming (98% fixity, 90% recovery), cold programming demonstrated competitive performance, especially at lower temperatures, without risking material degradation.

Conclusions:

• Cold programming is a viable and effective method for PU-SMPs with relatively high glass transition temperatures.
• This approach preserves material integrity by avoiding heating above T, making it attractive for sensitive applications.
• The study confirms good shape memory and fixity properties of PU-SMPs across a large strain range, suitable for electronics, aerospace, and aircraft structures.