Actuator Behaviour of Tailored Poly(thiourethane) Shape Memory Thermosets

Area of Science:

• Materials Science
• Polymer Chemistry
• Actuator Technology

Background:

• Shape memory materials offer potential for advanced actuators.
• Thermosetting polymers provide robust mechanical properties.
• Poly(thiourethane)s are a versatile class of polymers.

Purpose of the Study:

• To develop and characterize a new family of poly(thiourethane) shape memory thermosetting actuators.
• To investigate the influence of formulation on material properties and shape memory behavior.
• To establish design guidelines for poly(thiourethane) based shape memory materials.

Main Methods:

• Synthesis of poly(thiourethane)s using aliphatic diisocyanates (hexamethylene diisocyanate, HDI, and isophorone diisocyanate, IPDI) and a trithiol.
• Rheological studies to confirm latent catalyst behavior and curing kinetics.
• Mechanical testing and shape memory evaluation under unconstrained, partially constrained, and fully constrained conditions using single cantilever bending and tensile modes.
• Modeling of work performed using Timoshenko beam theory.

Main Results:

• The poly(thiourethane) actuators are easily prepared with tunable glass transition temperatures and mechanical properties by adjusting the HDI/IPDI ratio.
• Shape memory behavior and recovery force/energy can be modulated by altering the diisocyanate proportion.
• The recovery process in bending mode differs from tensile mode, providing insights into complex thermomechanical actuation.
• A predictive model based on Timoshenko beam theory was successfully applied.

Conclusions:

• The developed poly(thiourethane) networks offer tunable shape memory properties.
• Formulation control, specifically the diisocyanate ratio, is key to tailoring actuator performance.
• These findings provide a foundation for designing customized poly(thiourethane) shape memory actuators for specific applications.