High-performance thermoplastic polyurethane (TPU) elastomers have long been the objective of numerous studies. In this work, thermoplastic polyurethane–urea (TPUU) elastomers with balanced superior mechanical and thermal properties, in comparison with the rare cases of high-performance TPU/TPUU elastomers with super-high tensile strength, were synthesized by the reaction of polycarbonate diols with excess alicyclic isophorone diisocyanate, followed by the chain extension of alicyclic isophorone diamine. When the content of hard segment was around 47%, the TPUU elastomer had super-high tensile strength of 51.7 MPa, initial elastic modulus of 698 MPa and elongation at break of 480%. The temperature range of this TPUU elastomer's rubbery state was up to 120°C with storage modulus above 200 MPa, and its rubbery flow state reached 200°C where the storage modulus was still as high as 100 MPa. Fourier transform infrared spectroscopy analysis indicated the presence of strongly hydrogen bonded urethane and urea groups in these TPUU elastomers. Atomic force microscopy and differential scanning calorimetry studies demonstrated significant and nearly perfect microphase separation in these TPUU elastomers when the hard segment content was around or below 47%. These noncrystalline TPUU elastomers could be thermally processed or processed in the form of a solution.
For self-healing polymers, obtaining excellent healing ability and mechanical properties usually need complex chemical structure , external healing conditions, and high manufacturing difficulty. Therefore, self-healing efficiency and rate, mechanical strength , and simple structure design as well as no additional healing conditions of the material are contradictory properties and are difficult to optimize simultaneously. Herein, self-healable thermoplastic poly (urethane urea) elastomers driven by surface energy were fabricated by the introduction of asymmetric alicyclic structures and the healing properties in polymers were optimized by regulating surface energy. The results showed that with the increasing of isophorone diamine contents, the surface energy driving force increased from 36 kPa to 149 kPa, the healing time decreased from 30d to 5d, and healing efficiency, and tensile strength reached 100.9% and 4.04 MPa at room temperature. At the same time, polymers also obtained a high healing efficiency under high-temperature healing conditions. The healing mechanism is that asymmetric alicyclic structures with steric hindrance and ring flip promote the dissociation of hydrogen bonds , provide sufficient chain mobility, decrease the junction density, and improve the surface energy as well as the dissociation and reconstruction of hydrogen bonds. Energetic polymer composites using thermoplastic poly (urethane urea) elastomers as matrix obtained excellent healing properties. This study will offer a novel healing approach for developing advanced self-healing polymer materials.
The efficient surface modification of titanium dioxide (TiO 2 ) particles with different sizes was first carried out with “water only method” (Appl. Surf. Sci. 2018, 447, 664–672) developed in our group using 12-hydroxy stearic acid (12-HSA) as the modifier. The 12-HSA-modified TiO 2 particles with different sizes were then used to explore their effect on the mechanical and thermal properties of a thermoplastic polyurethane urea (TPUU) elastomer with superior mechanical and thermal properties produced newly in our lab using nonsymmetric alicyclic diisocyanate and diamine. Orthogonal experimental results showed that the order of impact of each factor on the modification efficiency of TiO 2 particles was: Temperature > time > modifier content. It was found that, in the nanometer (≤100 nm) range, smaller particles were more helpful to enhance the tensile strength of the TPUU elastomer, while larger ones to increase more significantly the elongation at break. Besides, the TiO 2 /polyurethane urea nanocomposites exhibited much better thermomechanical performance than the pristine TPUU elastomer, and the thermomechanical performance of the nanocomposites increased with decreasing particle size.
危险品化学品经营许可证（带存储）