Dissertation > Industrial Technology > Chemical Industry > Reagents and the production of pure chemicals > Colloid and hemicolloid substances > Basic theory

Polyvinyl alcohol hydrogel stability studies

Author LiMingJuan
Tutor YangRongJie
School Beijing Institute of Technology
Course Materials Science
Keywords Polyvinyl alcohol Hydrogel Swelling Crystallinity Microstructure
CLC TQ427.1
Type Master's thesis
Year 2008
Downloads 815
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This article first comprehensive overview of the types of polyvinyl alcohol (PVA) hydrogel and preparation at home and abroad, the nature of the hydrogel, characterization, and hydrogel applications. The two systems PVA hydrogel swelling, degradation of water status and network structure, degree of crystallinity, gel system, all the work is divided into six parts: 1 twin-screw extruder Preparation of the hydrogel of the two systems, respectively, with water as solvent PVA/H2O gel and a mixture of DMSO and water to as solvent PVA/DMSO/H2O gel. And systematically investigated these two systems of the hydrogel is immersed at different temperatures and different solvents in the quality, volume and mechanical properties change with time. The data show that: Swelling kinetics of the two systems is very different, but the mechanical properties are better. The same concentration, the mechanical strength of the two systems close, but the fluctuation range are larger, have a larger impact on the molding extrusion of the gel state its mechanical properties. Within a certain range, to improve the concentration of the polymer in the gel will increase in its mechanical properties. However, the hydrogel of the high concentration of the two systems after prolonged immersion in water, and brine, the mechanical strength will be a sharp decrease. 2 contains a large amount of DMSO solvent the PVA/DMSO/H2O gel when soaked in water for a long time, have a certain toxicity of DMSO to move out to the water, be interested in the internal structure and stability of the hydrogel impact . Therefore, by UV-visible spectrophotometer quantitative analysis, the establishment of a standard curve DMSO / water solution UV absorption analysis of DMSO PVA/DMSO/H2O gel soaked in distilled water removal rates. The results show that: the DMSO from the hydrogel vacate rate quickly, within a few already vacate about 80%, a few days when 10, has close to equilibrium. Viscosity method the measured viscosity average molecular weight of the PVA PVA/H2O gel, and study the impact of different factors on the degree of degradation of PVA PVA/H2O gel. 4 using X-ray diffraction method, the degree of crystallinity of the two systems before and after the hydrogel soaked, and studied the influence of the concentration on the degree of crystallinity of the PVA/H2O gel. The results showed that: As the concentration of PVA in the two systems the gel increases, the degree of crystallinity of the two systems have improved, but not the same as the variation of the degree of crystallinity of the two systems gel soaked after. 5 using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TG) of the state of water in the gel of the two systems. The results show that: with the increasing concentration of PVA gel two systems, the increase in non-freezing water, and the total amount of bound water decreases, while the amount of free water and freeze combined with little change in the water content of certain fluctuations within the range. Two systems gel Central Africa proportion of frozen water and Ganjiao substantially close to nothing to do with the literal value of 0.5, and the concentration of 1 to 1.6 per mole of light in the gel base the number of moles of the corresponding non-frozen water. The PVA hydrogel in the amount of non-frozen water with respect to the PVA itself is unchanged. 6 critical point drying - scanning electron microscopy in conjunction with technology carried out to characterize the the micro network structure of the gel. When the field emission scanning electron microscope magnification under observation, the network structure of the hydrogel of the two systems are very similar. Just PVA/DMSO/H2O gel network structure seems to be closer. The results prove the theoretical literature gel in different length scales within a complex hierarchy.

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