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Shape recovery and irrecoverable strain control in polyurethane shape-memory polymer.
Hisaaki Tobushi1, Syunichi Hayashi2, Kazumasa Hoshio3
1Department of Mechanical Engineering, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota 470-0392, Japan.
Science and Technology of Advanced Materials
|November 24, 2016
Summary
Controlling irrecoverable strain in polyurethane shape-memory polymers allows for complex shapes. Higher temperatures and longer holding times increase irrecoverable strain, enabling easier fabrication.
Area of Science:
- Materials Science
- Polymer Science
- Mechanical Engineering
Background:
- Shape-memory polymers (SMPs) exhibit large, recoverable strains, fixing shapes at low temperatures and recovering them at higher temperatures.
- Uncontrolled high-temperature exposure can lead to intermediate shapes due to irrecoverable strain, complicating fabrication.
- Irrecoverable strain control offers a method for fabricating complex SMP elements.
Purpose of the Study:
- To investigate the influence of strain-holding conditions on shape recovery and irrecoverable strain in polyurethane SMPs.
- To establish a method for controlling irrecoverable strain for complex shape fabrication.
- To formulate an equation describing irrecoverable strain control characteristics.
Main Methods:
- Tension tests were performed on polyurethane SMP films.
- Three-point bending tests were conducted on polyurethane SMP sheets.
- Varying strain-holding temperatures and times were applied to assess their effects.
Main Results:
- Increased shape-holding temperature and duration resulted in higher irrecoverable strain rates.
- A direct correlation was observed between strain-holding conditions and the extent of irrecoverable strain.
- An equation was formulated to quantify the relationship between holding conditions and irrecoverable strain.
Conclusions:
- Strain-holding temperature and time are critical parameters for controlling irrecoverable strain in polyurethane SMPs.
- This control enables a simplified fabrication process for complex SMP components.
- The formulated equation provides a predictive model for irrecoverable strain behavior.
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