Structure, Property Optimization, and Adsorption Properties of N,N'-methylenebisacrylamide Cross-Linked Polyacrylic Acid Hydrogels under Different Curing Conditions.

In this study, polyacrylic acid hydrogels were prepared by modulating the cross-linking agent mass ratio using UV and heat curing methods. The structures and properties of the hydrogels were characterized and analyzed using Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The results showed that the mechanical properties of the hydrogels prepared through UV curing were better than those prepared through heat curing. The maximum mechanical tensile strength of 139 kPa was achieved at a cross-linking agent mass ratio of 3.85% with 20 min of UV curing, and the maximum mechanical compressive strength of 0.16 MPa was achieved at a cross-linking agent mass ratio of 2.91% with 20 min of UV curing. However, the hydrogels prepared by heat curing had a higher tensile strength than those prepared using the heat curing method. In addition, the thermally cured hydrogels had higher water absorption and adsorption properties. Moreover, the PAA hydrogels prepared at cross-linking agent mass ratios of 1.91 and 2.91% with 2 h of the heat curing method had the best swelling properties. Moreover, the increase in the cross-linker mass concentration led to a decrease in the pore size and porosity and to a more compact structure.

High-Performance Optical PET Analysis via Non-Isothermal Crystallization Kinetics.

The optical properties of PET have always been a problem that related research has been trying to break through. In the previous work, we modified PET by adding PSLDH (phosphate antioxidant) to obtain a PET film with excellent optical properties. Through non-isothermal crystallization kinetic analysis of modified PET, we hope to verify the conclusion of optical properties by the effect of PSLDH addition on the crystallization properties of PET. PET and PSLDH modified PET were tested by DSC at different cooling rates. The non-isothermal crystallization kinetic process was calculated and analyzed by Jeziorny and Mo methods and the non-isothermal crystallization activation energy was analyzed by Kissinger and Friedman methods by analyzing the DSC curves. The results show that the addition of PSLDH at 0.05 wt% can make the crystallization of PET smaller and slower, which is the same as the case required for excellent optical properties. At the same time, the results can also guide the processing of the optical PET film.