Sand production is one of the major problems in sandstone reservoirs. Different mechanical and chemical methods have been proposed to control sand production. In this paper, we propose a chemical method based on using...Sand production is one of the major problems in sandstone reservoirs. Different mechanical and chemical methods have been proposed to control sand production. In this paper, we propose a chemical method based on using polyacrylamide/chromium triacetate hydrogel to investigate sand production in a synthetic sandpack system. To this end, a series of bulk experiments including the bottle test and rheological analysis along with compression tests were conducted. Experimental results indicated that the compressive strength of the sandpack was increased as much as 30 times by injecting 0.5 pore volume of hydrogel. Also, it was found that the increases in cross-linker and polymer concentrations exhibited a positive impact on the compressive strength of the sandpack, mostly by cross-linker concentration(48 psi). Hydrogel with a higher value of cross-linker could retain its viscoelastic properties against the strain which was a maximum of 122% for 0.5 weight ratio of cross-linker/polymer. The presence of salts, in particular divalent cations, has a detrimental effect on the hydrogel stability. The maximum strain value applied on hydrogel in the presence of CaCl_2 was only about 201% as compared to 1010% in the presence of distilled water. Finally, thermogravimetric analysis and its derivative showed that the hydrogel could retain its structure up to 300 °C. The results of this study revealed the potential application of the hydrogel to control sand production.展开更多
Double network(DN)hydrogels as one kind of tough gels have attracted extensive at-tention for their potential applications in biomedical and load-bearing fields.Herein,we import more functions like shape memory into t...Double network(DN)hydrogels as one kind of tough gels have attracted extensive at-tention for their potential applications in biomedical and load-bearing fields.Herein,we import more functions like shape memory into the conventional tough DN hydro-gel system.We synthesize the PEG-PDAC/P(AAm-co-AAc)DN hydrogels,of which the first network is a well-defined PEG(polyethylene glycol)network loaded with PDAC(poly(acryloyloxyethyltrimethyl ammonium chloride))strands,while the second network is formed by copolymerizing AAm(acrylamide)with AAc(acrylic acid)and cross-linker MBAA(N;N′-methylenebisacrylamide).The PEG-PDAC/P(AAm-co-AAc)DN gels exhibits high mechanical strength.The fracture stress and toughness of the DN gels reach up to 0.9 MPa and 3.8 MJ/m^3,respectively.Compared with the conventional double network hydrogels with neutral polymers as the soft and ductile second network,the PEG-PDAC/P(AAm-co-AAc)DN hydrogels use P(AAm-co-AAc),a weak polyelectrolyte,as the second network.The AAc units serve as the coordination points with Fe^3+ions and physically crosslink the second network,which realizes the shape memory property activated by the reducing ability of ascorbic acid.Our results indicate that the high mechanical strength and shape memory properties,probably the two most important characters related to the potential application of the hydrogels,can be introduced simultaneously into the DN hydrogels if the functional monomer has been integrated into the network of DN hydrogels smartly.展开更多
New IPN hydrogels composed of diallyldimethylammonium chloride (DADMAC) and natural macromolecule, kappa-carrageenan (KC) were prepared by gamma irradiation and their properties were studied, The results show that bot...New IPN hydrogels composed of diallyldimethylammonium chloride (DADMAC) and natural macromolecule, kappa-carrageenan (KC) were prepared by gamma irradiation and their properties were studied, The results show that both the gel strength and the swelling capacity of the IPN hydrogels were enhanced significantly as compared with those of the pure hydrogels of PDADMAC.展开更多
Contemporary dental adhesives show favorable immediate results in terms of bonding effectiveness. However, the durability of resin-dentin bonds is their major problem. Materials and Methods: Preparation of 3 chitosan-...Contemporary dental adhesives show favorable immediate results in terms of bonding effectiveness. However, the durability of resin-dentin bonds is their major problem. Materials and Methods: Preparation of 3 chitosan-antioxidant hydrogels was achieved using modified hydrogel preparation method. Their effect on the bond strength to dentine both short term (after 24 hours) and long term (after 6 months) were evaluated using shear bond strength measurements using Instron Universal Testing Mascine). The SEM was used to study the surface of the hydrogels. The cell survival rate (cytotoxicity) of the antioxidants resveratrol, β-carotene and propolis towards Balb/c 3T3 mouse fibroblast cells was also assessed using the standard MTT assay. Results: It was found that chitosan-H treated dentine gives significantly (p β-carotene (92%) > propolis (68%) > resveratrol (33%). Conclusion: the antioxidant-chitosan hydrogels significantly improved bonding to dentine with or without phosphoric acid treatment. The pH of the growth medium had a high influence on the cell survival rate of Balb/c mouse 3T3 fibroblast cells. The release of the antioxidant β-carotene would not have an influence on the pulp cells. These materials might address the current perspectives for improving bond durability.展开更多
Objectives: To investigate the water sorption, solubility, bond strength and biocompatibility of a new kind of compound autopolymerizing hydrogel [polyhydroxyethyl methacrylate (PHEMA) and polybutyl methacrylate (PMBA...Objectives: To investigate the water sorption, solubility, bond strength and biocompatibility of a new kind of compound autopolymerizing hydrogel [polyhydroxyethyl methacrylate (PHEMA) and polybutyl methacrylate (PMBA)] designed for denture soft lining material. Methods: According to ISO standard, the water sorption, solubility, bond strength and a series of biological evaluation for this hydrygel were tested, and in bond strength, the plasticized acrylic and SDG-A silicone denture soft lining materials were used for comparative materials. Results: It showed that hydrogel had much higher bond strength with denture base acrylic resin (7.984 Mpa) when compared with plasticized acrylic and SDG-A silicone soft lining material. There was a good biocompatibility in all biological tests. No cytotoxic, allergic, acute systemic toxic, oral mucous membrane irritant, genotoxic and heamolysis activity was demonstrated. It also indicated the absorption and solubility in distilled water were higher than those in artificial saliva at the same stage (at 7 d and 28 d ). There was statistical significance between them (P<0.01). It had higher water sorption (24.96%) and lower solubility (0.51%) at 28 d. Further clinical study is needed to verify the dimensional stability. Significance: It is to develop a kind of denture soft lining material which presenting a good bond strength with base resin and keeping soft properties for a long time.展开更多
基金support of the Iran National Science Foundation(INSF)with Project No.of 95849122
文摘Sand production is one of the major problems in sandstone reservoirs. Different mechanical and chemical methods have been proposed to control sand production. In this paper, we propose a chemical method based on using polyacrylamide/chromium triacetate hydrogel to investigate sand production in a synthetic sandpack system. To this end, a series of bulk experiments including the bottle test and rheological analysis along with compression tests were conducted. Experimental results indicated that the compressive strength of the sandpack was increased as much as 30 times by injecting 0.5 pore volume of hydrogel. Also, it was found that the increases in cross-linker and polymer concentrations exhibited a positive impact on the compressive strength of the sandpack, mostly by cross-linker concentration(48 psi). Hydrogel with a higher value of cross-linker could retain its viscoelastic properties against the strain which was a maximum of 122% for 0.5 weight ratio of cross-linker/polymer. The presence of salts, in particular divalent cations, has a detrimental effect on the hydrogel stability. The maximum strain value applied on hydrogel in the presence of CaCl_2 was only about 201% as compared to 1010% in the presence of distilled water. Finally, thermogravimetric analysis and its derivative showed that the hydrogel could retain its structure up to 300 °C. The results of this study revealed the potential application of the hydrogel to control sand production.
基金supported by the National Natural Science Foundation of China (No.51273189)the National Science and Technology Major Project of the Ministry of Science and Technology of China (No.2016ZX05016),the National Science and Technology Major Project of the Ministry of Science and Technology of China (No.2016ZX05046)
文摘Double network(DN)hydrogels as one kind of tough gels have attracted extensive at-tention for their potential applications in biomedical and load-bearing fields.Herein,we import more functions like shape memory into the conventional tough DN hydro-gel system.We synthesize the PEG-PDAC/P(AAm-co-AAc)DN hydrogels,of which the first network is a well-defined PEG(polyethylene glycol)network loaded with PDAC(poly(acryloyloxyethyltrimethyl ammonium chloride))strands,while the second network is formed by copolymerizing AAm(acrylamide)with AAc(acrylic acid)and cross-linker MBAA(N;N′-methylenebisacrylamide).The PEG-PDAC/P(AAm-co-AAc)DN gels exhibits high mechanical strength.The fracture stress and toughness of the DN gels reach up to 0.9 MPa and 3.8 MJ/m^3,respectively.Compared with the conventional double network hydrogels with neutral polymers as the soft and ductile second network,the PEG-PDAC/P(AAm-co-AAc)DN hydrogels use P(AAm-co-AAc),a weak polyelectrolyte,as the second network.The AAc units serve as the coordination points with Fe^3+ions and physically crosslink the second network,which realizes the shape memory property activated by the reducing ability of ascorbic acid.Our results indicate that the high mechanical strength and shape memory properties,probably the two most important characters related to the potential application of the hydrogels,can be introduced simultaneously into the DN hydrogels if the functional monomer has been integrated into the network of DN hydrogels smartly.
文摘New IPN hydrogels composed of diallyldimethylammonium chloride (DADMAC) and natural macromolecule, kappa-carrageenan (KC) were prepared by gamma irradiation and their properties were studied, The results show that both the gel strength and the swelling capacity of the IPN hydrogels were enhanced significantly as compared with those of the pure hydrogels of PDADMAC.
文摘Contemporary dental adhesives show favorable immediate results in terms of bonding effectiveness. However, the durability of resin-dentin bonds is their major problem. Materials and Methods: Preparation of 3 chitosan-antioxidant hydrogels was achieved using modified hydrogel preparation method. Their effect on the bond strength to dentine both short term (after 24 hours) and long term (after 6 months) were evaluated using shear bond strength measurements using Instron Universal Testing Mascine). The SEM was used to study the surface of the hydrogels. The cell survival rate (cytotoxicity) of the antioxidants resveratrol, β-carotene and propolis towards Balb/c 3T3 mouse fibroblast cells was also assessed using the standard MTT assay. Results: It was found that chitosan-H treated dentine gives significantly (p β-carotene (92%) > propolis (68%) > resveratrol (33%). Conclusion: the antioxidant-chitosan hydrogels significantly improved bonding to dentine with or without phosphoric acid treatment. The pH of the growth medium had a high influence on the cell survival rate of Balb/c mouse 3T3 fibroblast cells. The release of the antioxidant β-carotene would not have an influence on the pulp cells. These materials might address the current perspectives for improving bond durability.
文摘Objectives: To investigate the water sorption, solubility, bond strength and biocompatibility of a new kind of compound autopolymerizing hydrogel [polyhydroxyethyl methacrylate (PHEMA) and polybutyl methacrylate (PMBA)] designed for denture soft lining material. Methods: According to ISO standard, the water sorption, solubility, bond strength and a series of biological evaluation for this hydrygel were tested, and in bond strength, the plasticized acrylic and SDG-A silicone denture soft lining materials were used for comparative materials. Results: It showed that hydrogel had much higher bond strength with denture base acrylic resin (7.984 Mpa) when compared with plasticized acrylic and SDG-A silicone soft lining material. There was a good biocompatibility in all biological tests. No cytotoxic, allergic, acute systemic toxic, oral mucous membrane irritant, genotoxic and heamolysis activity was demonstrated. It also indicated the absorption and solubility in distilled water were higher than those in artificial saliva at the same stage (at 7 d and 28 d ). There was statistical significance between them (P<0.01). It had higher water sorption (24.96%) and lower solubility (0.51%) at 28 d. Further clinical study is needed to verify the dimensional stability. Significance: It is to develop a kind of denture soft lining material which presenting a good bond strength with base resin and keeping soft properties for a long time.
