Papers by Keyword: Swelling Kinetics

Abstract: A series of novel cross-linked poly N-isopropylacrylamide (PNIPAM)/poly diallyl dimethyl ammonium chloride (PDMDAAC) semi-IPN hydrogels were synthesized through free radical solution polymerization in water at 30°C. FTIR was used to characterize the structure of resultant hydrogels. The pH and temperature sensitivity of hydrogels were systematicly studied, and the swelling properties of hydrogels were also explored. The results show that the semi-IPN hydrogels have both temperature and pH sensitivities. The hydrogels exhibit fast swelling rate and excellent stimuli-responsive behavior.

Abstract: In this study the different finesses degree of the pulverized Eupatorium Adenophorum (EA) was evaluated as potential raw materials for the low-cost hydrogels whose the swelling behaviors were compared and studied at the same graft-copolymerization condition. The results are shown that the absorbency of EA hydrogels increased with decreasing the granule size of pulverized EA from 0.450mm to 0.063mm, while the swelling ratios gradually decreased with continuously reducing the particles size to 0.020mm, and the swelling exponents have been found to indicate non-Fickian mechanism for EA hydrogels at the all finesses range of 0.020~0.450mm. Moreover, to obtain better model for above 60% water uptake, the Beren-Hopfenberg differential model was applied, which also enabled to calculate the relaxation constants.

Abstract: Starch-g-poly(acrylic acid) (CSt-g-PAA) hydrogels were prepared from cassava starch and acrylic acid by graft polymerization. The hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric-differential scanning calorimetry (TG-DSC). Additionally, the water absorbency and hygroscopic swelling properties of the hydrogels were investigated respectively. The two processes were simulated using mathematical modes. The results revealed that the crystal structure of starch was destroyed. At 40°C and relative humidity 90% (90% RH), the samples (starch mass15%, 50%) have a better performance of the moisture absorption. Hygroscopic rate declined with the increase of relative humidity.