No abstract

A self-healing waterborne polyurethane (WPU) materials containing dynamic disulfide (SS) bond was prepared by introducing SS bond into polymer materials. The zeta potential revealed that all the synthesized WPU emulsions displayed excellent stability, and the particle size of them was about 100 nm. The characteristic peaks of N-H and S-S in urethane were verified by FTIR, and the chemical environment of all elements were confirmed by the XPS test. Furthermore, the tensile strength, self-healing process and self-healing efficiency of the materials were quantitatively evaluated by tensile measurements. The results showed that the self-healing efficiency could reach 96.14% when the sample was heat treated at 70 °C for 4 h. In addition, the material also showed a good reprocessing performance, and the tensile strength of the reprocessed film was 3.39 MPa.

The properties of waterborne polyurethanes were improved significantly by incorporating silane both in the backbone and side chains.

Proton exchange membranes consisting of Nafion V R and crystallized titania nanoparticles have been developed to improve water-retention and proton conductivity at elevated temperature and low relative humidity. The anatase-type titania nanoparticles were synthesized in situ in Nafion solution through sol-gel process and the size of the formed titiania nanoparticles is in the range of 3-6 nm. The formed nanoparticles are well-dispersed in Nafion solution at the titania concentration of 5 wt %. The glass transition temperature of the formed Nafion-titania composite membrane is about 20 o C higher than that of plain Nafion membrane. At elevated temperature (above 100 C), the Nafion-titania nanocomposite membrane shows higher water uptake ability and improved proton conductivity compared to pure Nafion membrane.

Polycarboxylic superplasticiser (PS) and naphthalene-based superplasticiser (NBS) were used to achieve a denser structure of α-hemihydrate calcium sulfate and better mechanical properties. The hydration process was investigated by thermogravimetric analysis (TGA), which showed that the PS decelerated the whole hydration process of α-hemihydrate calcium sulfate, whereas the NBS accelerated the process in the early stage and decelerated it in the late stage. It was noteworthy that they both could increase the highest hydration heat. The PS delayed the hydration heat peak whereas the NBS advanced it. Both scanning electron microscopy and pore property analysis confirmed the formation of a more compact structure of the hydration product. Optimal mechanical properties of α-hemihydrate calcium sulfate were obtained with 0·5% NBS or 0·4% PS by mass. Under the same conditions, the PS was more efficient at improving the properties of α-hemihydrate calcium sulfate than the NBS.