Study Of Thermal-healing Properties Of Polyurethane Containing Dynamic Polyurea Chains

Most reparable polymer materials have serious problems like long healing process, poor healing efficiency, low glass transition temperature (Tg), weak mechanical properties, nonrepeatability, and high cost. These shortcomings limited practical applications of the reparable polymers. In the present work, a dynamic chain, which contains a number of sequential dynamic urea bonds, are proposed. By the incorporations of the dynamic polyuria chains into a polyurethane network, their influence on healing speed, healing efficiency, and mechanical properties of the polyurethane material were studied.Four kinds of polyurethanes, PU, PU1, PU3, and PU5, are synthesized. PU1 has discrete dynamic urea bonds in the network, while PU3 and PU5 contain the dynamic trimer and pentamer chains, respectively. PU, the blank control, is not of dynamic urea bond. The polyurethanes are characterized by optical microscope observing, tensile, shearing, and thermal extrusion tests, and the results indicated a consistent performance order:PU5> PU3> PU1> PU, meaning that more the dynamic urea bonds, higher the healing efficiency and the healing speed. Moreover, dynamic mechanical analysis (DMA) test demonstrated that Tg and modulus of the polyurethane network increase with the increasing of the urea bonds in the dynamic polyurea chains as well. The simultaneous enhancement on both thermal healing capability and mechanical properties is an important advantage distinguished from other healable materials.In summary, the concept of healable materials containing dynamic polymer chains is firstly proposed. The healing mechanism and the superiority of the novel healing polymer are demonstrated. The results presented in this work will provide new theoretical basis for future development of the reparable polymers.