Study On Micro-crosslinking, Properties And Structure Of Hydrophopbically Associating Acrylamide Copolymer

This paper research the hydrophopbically associating acrylamide Copolymer/phenol formaldehyde. After cross-linked, the molecular weight of hydrophopbically associating copolymer increase , hydrophobic association increases, this crosslinking system is the favorable polymer for flooding, which is of high viscosifying, salt-toleration, shear toleration, thermal and thermo toleration and long period stability.The hydrophobically associating water-soluble acrylamide-modified anionic copolymer (PASA) of acrylamide(AM) with butylstyrene (BST) and sodium-2-a-crylamido-2-methypropane sulphonate (NaAMPS) was synthesized by the micellar free radical copolymerization techniqe. The phenol formaldehyde resin of phenol and formaldehyde was synthesized by two-step technology, the optimum parameters of synthesis of phenol formaldehyde resin as crosslinker are obtained: P/F molar tation 1:2.5, pH in range 9-10, end reaction temperature 90℃, and synthesized time 50 min, in this synthesized condition, with PASA crosslinked ability of the phenol formaldehyde resin increase. Research on the crosslinked copolymer PASA-PF crosslink influencing factors, and choose out the best prescription is: 1.0 g/L PASA, 0.35 g/L crosslinker , 10 of pH value, 85℃and 96 hour. PASA and phenol and formaldehyde was proved to be the target product by FT-IR.After crosslinked, the critical aggregation concentration of copolymer is reduced to 1.5 g/L from 0.7 g/L. The solution viscosity of 0.7 g/L PASA-PF was increased form 6 mPa·s to15.3mPa·s. The NaCl concentration of corresponding the highest solution viscosity was reduced to 50 g/L form 10 g/L in 1.0 g/L PASA-PF solution., but the solution viscosity is still 84.6 mPa·s in 100 g/L brine solution and 57.2 mPa·s in 75℃. The crosslinking copolymer exhibits excellent shear toleration, shear thickening and aging resistance in 90℃. The apparent viscosity of 1.0 g/L PASA-PF in 50 g/L brine solution is 102.1 mPa·s after 60d aging and the viscosity retention is 85.7%.Based on dynamic viscoelasticity experiment, it shows that the crosslinking copolymer form more hydrophobic associative structure, which results in the viscoelasticity is obvious. The higher the polymer concentration is, the more obvious the viscoelasticity., and in 50 g/L brine solution copolymer form Supermolecular structure, leading to the solution exhibits the elastic characteristic fluid in testing frequency.The micro-circumstance polarity of hydrophobic association area of PASA-PF copolymer was researched by the fluorescence probe. It shows that the crosslinking copolymer form large numbers of hydrophobic association areas in the aqueous solution and salt solution, I₁/I₃ value of PASA-PF solution is reduced to 0.98 from 0.8, and the size and amount of hydrophobic association areas and nonpolarity of solution increase with the polymer concentration is increased from 1.5 g/L to 2.0 g/ L. I₁/I₃ value of 1.5 g/L PASA-PF is 1.028 in 5 g/L brine solution, I1/I3 value is 0.765 in 10 g/L brine solution, and the size and amount of hydrophobic association areas decrease in 30-50 g/L brine solution.Scanning electric microscope shows that rigid of molecular chains become stronger and still have extended molecular conformation in 5 g/L brine solution, leading to the copolymer form continuous associative structure, resulting in increase of the apparent viscosity of polymer solution. In 50 g/L brine solution, the size of associated cluster increase and associative structure become continuous aggregation structure without any pore from continuous supramolecular network with the polymer concentration is increased from 1.2 g/L to 1.5 g/ L, resulting in the remarkable increase of the apparent viscosity of polymer solution. PASA-PF copolymer crosslinks excessively to form jellylike particle when crosslinker concentration is 0.5 g/L. Solubility and stability of solution become worse, appear phenomenon like delamination, and the viscosity decrease. The SEM results reveal the relationship between the solution properties and aggregation of the crosslink polymer.