# Shape Memory Polyurethane and its Composites for Various Applications
## 2 Shape Memory Polyurethane in Different Applications
### Self-Healing
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & \multicolumn{4}{c}{**Mechanical Properties**} & \multicolumn{4}{c}{**Transition Temperatures**} & \multicolumn{2}{c}{**Self-Healing Properties**} & \multicolumn{2}{c}{**Shape Memory**} & \multirow{2}{*}{**Ref**} \\ \cline{2-2} \cline{5-11}  & **Deformation** & & & & & & & & & & & \\ \cline{2-11}  & **Parameters** & **UTS** & **E (\%)** & **Tonghess** & **Impact** & **Resistance** & **Thermal** & **Tg** & **Tm** & **Parameters** & **Self-Healing** & **Recovery** & **Fixing** & **Ratio** & **Ratio** \\ \hline \multirow{5}{*}{SMPU-UT-DT} & **stretched into a** & & & & & & & & & & & & \\  & **length as long as** & & & & & & & & & & & & \\  & **possible at a** & & & & & & & & & & & & \\  & **sufficiently high temperature (\({}^{0}\))** & & & & & & & & & & & & \\  & **temperature (\({}^{0}\))** & & & & & & & & & & & & \\  & **\({}^{\circ}\)**/C for 1 min with** & & & & & & & & & & & & \\  & a hair dry** & & & & & & & & & & & & \\ \hline \hline \multicolumn{11}{l}{TPU/PCL/} & **under the external** & **–** & **–** & **–** & **–** & **–** & **–** & **–**60 \({}^{\circ}\)**/C** & **–** & **–** & **96\%** & **63.9**\%** & **96.8**\%** & **[71]** \\ \hline \multicolumn{11}{l}{**TTS: Ultimate tensile strength, PUVs: Polyurethane-wirches, PCL did: Polyf(-caprolactone) did, SHZPU: Self-healing writerionic polyurethanes, SMPL(U): Shape-memory polyurethane, IPNs: Interpretating polymer networks, PU: Polyurethane, SBS: Synene-butadiene-styrene, SMPU-COBA: Shape-memory polyurethane-4-octylydecyloybenzook acid, ZMSPU: Zsifferentiionic multi-shape-memory polyurethanes, +C-PCL-20H: Cyclic polyf(-caprolactone), J-PCL-20H: Linear polyf(-caprolactone), J-PNG: PolyIsobutyrate-functionalized graphene oxide, ITD: Toluene discourane, ITU: Dermosetting polyurethane, WONCN: Multi-walled carbon nanotubes, E (\%): Elongation at break.** \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._[PERSON] et al. [60] have developed a renewable castor oil based polyurethane vitrimers [72; 73]. Vitrimers are crosslinked thermosets which can easily be processed or recycled due to interchange transesterification process upon heating. In this study, the developed polyurethane vitrimers contain intrinsic carbamate bond which undergo transcarbamoyllation/transesterification reaction in the presence of dibutyltin dilaurate as a catalyst and govern the thermally induced dual shape memory and self-welding ability. They found an increase in the stress of the welded samples with welding time whereas higher temperature promoted the welding ability (Figure 10). Figure 9: Schematic representation of cooperative self-healing: (**a**) Alodine microcapsules loaded polyurethane coating on aluminum alloy, (**b**) release of Alodine from the microcapsules caused by defect, (**c**) formation of Alodine conversion coating on aluminum alloy, (**d**) shape memory effect of polyurethane stimulated by external heat, (**e**) completion of healing process of scratch [59]. In another work reported by [PERSON] et al. [71], the demonstration of the self-healing and shape memory ability of thermoplastic polyurethane and polycaprolactone blended with MWCNTs has been made using melt-blending technique. They disclosed that the addition of MWCNTs could allow the polyurethane blend to respond to near infrared (NIR) radiation and achieve healing repeatedly. Physical healing (nearly 96%) of sliced pieces of the developed blend was found to reach to its original flexibility after three minutes of NIR exposure (808 nm, 0.5 W) and the damaged surface was fully recovered (Figure 11). They also postulated that the use of NIR radiation could control the self-healing and shape memory capability remotely.