Mechanism for “remembering” original shape and transient shape.
Common mechanisms: Entanglements, Crosslinks and hard-domains.
Transient shape fixed usually with crystalline phase or the glassy state.
Revert back to original shape by heating.
Heating above Tm (if the crystalline phase is used to fix the transient shape)
Heating above Tg (if the glassy phase is used to fix the transient shape)
How Shape Memory Polymers Work Original: Chemical Cross-Links Temporary: Glassy Phase Lendlein et al. Original: Crystalline Hard domains (Physical cross-links) Temporary: Crystallites Original: Chemical Cross-Links Temporary: Crystallites
Shape Memory Polymers Representative Application Time series photographs that show the recovery of a shape-memory tube. (a)- (f) Start to finish of the process takes a total of 10 s at 50°C (Marc Behl et al 2007).
Shape Memory Mechanism in CSMP’s Deform Cool Unload Heat Amorphous polymer Cross-link Crystallite Legend Melting Crystallization T > T r T < T r State 1 State 4 State 2 State 3 Stretch Nominal Stress 1 2 3 4
Shape Memory Mechanism in GSMP’s Deform Cool Unload Heat Amorphous polymer Cross-link Glassy polymer Legend Glass Transition T > T r T < T r State 1 State 4 State 2 State 3 Stretch Nominal Stress 1 2 3 4