Few thermoplastic polyurethane (TPU) blending materials are reported to tune shape-memory capability, self-healing ability, and recyclability as well as mechanical property due to the different requirement of phase morphologies. This work focuses on how reversible epoxy domains affect the structures and properties of TPUs that contain disulfide bonds in main chains. The blended epoxy oligomers with dangling furan groups are miscible with the TPU. Self-healing efficiency can be improved by such miscible epoxy oligomers that are also beneficial for shape recovery but harmful for shape fixation. In the presence of bis(4-maleimidophenyl)methane (BMI), crosslinked epoxy domains phase separate from the TPU matrix to form microscale domains after the Diels–Alder (DA) reaction between furan groups and maleimide groups in BMI. Elastic modulus and tensile strength of TPU are greatly improved in comparison with pristine TPU and TPU/epoxy blends without BMI. The phase-separated domains deteriorate the self-healing, and the presence of phase-separated microdomains facilitates the shape fixation but deteriorates the shape recovery. This work is not only useful to further understand the relation between structures of polymer blends with intelligent features, but also offers a useful approach to adjust the properties and capabilities of TPU in a cost-effective manner.
Damping materials are used in many fields, and damping property within a wide temperature range is usually required. More importantly, the ability for damping materials to recover from damages can prolong the service life. In the present work, we prepared damping materials with loss factor beyond 0.3 within 80 ℃ and self-healing capability based on the gradient phase separated morphologies of epoxy domains in polyurea-urethane matrix. The epoxy oligomer ( E ) with dangling furan groups can be compatible with polyurea-urethane ( U ) that consisted of disulfide bonds in the main chains and intermolecular hydrogen bonding, but the reversibly crosslinked epoxy domains based on Diels-Alder reaction phase separated from the matrix. The gradient morphology, thus, was created by controlling the diffusions of 4,4′-methylenebis( N -phenylmaleimide) ( B ) and epoxy oligomer in the polyurethane matrix using multilayer assembly. The morphologies were determined by the weight ratios of the layers with U + E + B , U + E , and U , respectively. The increase in the ratio of layer U + E + B against layer U + E , more evident gradient morphology was found as well as the mechanical property, anti-solvent resistance, and noise absorption were increased. The loss factor was moved toward high temperature. The increase in the contribution of layer U + E reduced the temperature of the loss factor as well as increased the impact resistance and self-healing capability. The polyurea-urethane blends with gradient phase separated morphologies can be used as good damping materials for noise absorption and impact resistance, while the self-healing capability facilitated the recovery from fatigue, microcracks, or even damage due to frequent energy absorption and dissipation.
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