In this paper, a series of thermo- and pH-sensitive poly(vinyl alcohol)/poly(N, N-diethylacrylamide-co-itaconic acid) (PVA/P(DEA-co-IA)) semi-interpenetrating polymer network (semi-IPN) hydrogels were synthesized by radical polymerization and semi-IPN technology. The influence of PVA on the property of resulting PVA/P(DEA-co-IA) (PVA/PDI) semi-IPN hydrogels was investigated and characterized. The interior morphology observed by scanning electron microscopy (SEM) revealed that freeze-dried semi-IPN hydrogels had small pore size and interconnected porous network structures. X-ray diffraction (XRD) studies showed that a sharp characteristic peak of PVA in semi-IPN hydrogel could be observed at about 2θ = 20°. The incorporation of PVA decreased the equilibrium swelling ratio of modified hydrogels when compared with a usual PDI hydrogel. The semi-IPN hydrogels exhibited unconventional thermosensitive characteristics, such as faster deswelling rates and slower swelling rates in response to temperature change, and excellent mutative values in response to an alternation of the pH value, the changing degree of which depended on the PVA content. The release behaviors of the model drug, aminophylline, were found to be dependent on hydrogel compositions and the environmental temperature. Compared with the usual PDI hydrogel, the drug release rate of the semi-IPN hydrogel is slower, which could be expected to be useful in the biomedical and biotechnology fields.
Effect of corrosion duration on C110 casing steel was investigated in the stimulated gas field solution containing both 1 MPa CO2 and 1.5 MPa H2S at 90 °C by using a high temperature autoclave. And the corrosion rate prediction model was established based on the corrosion duration effect. In addition, effect of stress on corrosion of steel was analyzed from the thermodynamics and electrochemistry theories, moreover, the casing corrosion life prediction model was established under three axis stress state with considering the influences of stress and corrosion effect. The results reveal that the corrosion rate of C110 casing steel decreases significantly as corrosion time increases, then gradually tends toward stability. In addition, the casing steel is subjected to load and corrosion solution, the thermodynamic activity and the electrochemical reaction potential are changed, ultimately aggravating the process of corrosion. Compared to corrosion time and wall thickness, the internal pressure is the main factor governing the casing corrosion. Therefore, it is suggested that the synergistic effects of corrosion time and stress should be considered in casing safety design and operation.
The effect of element sulphur on the performance of corrosion inhibitor in H 2 S/CO 2 gas field solution was investigated at different velocities. The morphology and composition of corrosion products were characterised by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) methods. The results indicated that L360 QS steel surface suffered from sulphur-induced pitting corrosion at a low velocity due to insufficient sulphur-carrying fluid power. At high flow velocities, the steel surface is likely to be suffered high fluid power which can remove the inhibitor film and corrosion scales by the mechanical erosion effect. The sulphur corrosion mechanism model and the flow-induced corrosion model due to the high wall shear force have been proposed in the study. This work suggested that the gas production rate should be controlled at an acceptable level to guarantee the service safety of pipeline system.
In this study, poly(N,N-diethylacrylamide-co-(2-dimethylamino) ethyl methacrylate) (poly(DEA-co-DMAEMA)) hydrogels were synthesized by changing the initial DEA/DMAEMA mol ratio. The hydrogels were characterized by Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). In comparison with the PDEA hydrogel, the equilibrium swelling ratio (ESR) and lower critical solution temperature (LCST) of the hydrogels increase with the increase of DMAEMA content in the feed. The deswelling and reswelling kinetics and cytotoxicity of the different composition ratios of DEA to DMAEMA in the co-polymerized hydrogels were also investigated in detail. The absorption and release behaviour of the model drug, bovine serum albumin, were found to be dependent on hydrogel composition and environment temperature, which suggests that these materials have potential application as intelligent drug carriers.
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