Strong Thermo-tolerant Silicone-Modified Waterborne Polyurethane/Polyimide Pressure-Sensitive Adhesive.

A waterborne polyurethane pressure-sensitive adhesive (WPUPSA) has the advantages of low pollution and good viscoelasticity. However, its poor thermo-tolerance limits its application in the field of high temperatures. Hence, a novel silicone-modified strong thermo-tolerant waterborne polyurethane/polyimide pressure-sensitive adhesive is developed as a way to remedy this problem. The single-chain structure of waterborne polyurethane (WPU) is transformed into a network structure by introducing the three-position network structure to increase the cohesive energy and heat resistance of the WPUPSA. Meanwhile, the primary chain of waterborne polyurethane (WPU) is modified by the reaction between pyromellitic dianhydride (PMDA) and isophorone diisocyanate (IPDI) to include an imide ring and a benzene ring with more stable structures and heat resistance. Characterization results of the prepared WPUPSA show that the thermo-tolerance index of the WPUPSA increases by 15.2% and the room temperature 180° peel strength and shear resistance of the WPUPSA increase by 80.9 and 231.8%, respectively. Meanwhile, the temperature corresponding to the maximum thermal decomposition rate of the samples is improved. More importantly, at 80 and 100 °C, the 180° peel strength and shear resistance of the modified samples are stronger than those of the unmodified samples. In addition, the energy storage modulus of WPUPSAs is also greater than the loss and increases with the increase of the frequency. Viscoelasticity dominates in the samples. This will provide new insight for the development of WPUPSAs in the field of high-temperature resistance.

Solubility of dicarbohydrazide bis[3-(5-nitroimino-1,2,4-triazole)] in common pure solvents and binary solvents at different temperatures.

The solubility of dicarbohydrazide bis[3-(5-nitroimino-1,2,4-triazole)] (DCBNT) was first measured under the different pure solvents and binary solvents by the dynamic method over the temperature range of 290-360 K at atmospheric pressure. Results in all the solvents were positively correlated with temperature, namely increased with increasing temperature. The experiment data were correlated by the Apelblat equation, the Yaws equation and the polynomial equation. The conclusion showed that these three models all agreed well with the experimental data. Simultaneously, the dissolution enthalpy, dissolution entropy and Gibbs free energy of DCBNT in different solvents were calculated from the solubility data by using the Apelblat model. The results indicate that the dissolution process of DCBNT in these solvents is driven by entropy, which provides theoretical guidance for further research on the crystallization of DCBNT.