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Self-Healing PAM Composite Hydrogel for Water Shutoff at High Temperatures: Thermal and Rheological Investigations


 Self-healing hydrogels have attracted much attention as they possess the ability to increase the lifetime of the materials and reduce the total cost during the process of long-term use. In this study, self-healing PAM-Zr(OH)4 hydrogel was prepared from acrylamide (AM) and Zr(OH)4 nanosheet filler using a free radical polymerization method. In addition, the polymerization of AM monomers was initiated by ammonium persulfate (APS) while tetramethylethylenediamine (TEMED) was used as a catalyst. The prepared composite hydrogel was cured at high temperature (i.e. 150°C) in order to simulate the conditions of the oil reservoirs. The thermal and rheological properties of the composite hydrogel were studied using thermogravimetric analyzer (TGA), differential scanning calorimetry (DSC) and dynamic mechanical analyzer (DMA). As observed from DSC, the free water (Wf) for PAM-Zr(OH)4 hydrogel was 0.39 and that of for neat-PAM was 0.34. The storage modulus (G′) and loss modulus (G″) for the PAM-Zr(OH)4 hydrogel were 2060 Pa and 644 Pa, whereas that of for neat PAM was 2000 Pa, 627 Pa respectively. From the results, incorporating fillers into the PAM matrix had significant improvements on the thermal and mechanical properties for PAM-Zr(OH)4 hydrogel in comparison to that of neat-PAM hydrogel. In addition, the composite hydrogel has demonstrated an excellent swelling behavior (i.e. swelling capacity up to 14,000%) while sustaining its gel strength (G′/G″). The kinetics of water absorption by the PAM-Zr(OH)4 hydrogel was pseudo-second-order with a second-order rate constant (k2) of 9.3×10−8 min g/g.