Synthesis,characterization, and flocculation characteristics of hydrolyzed and unhydrolyzed polyacrylamide grafted xanthan gum

The partial hydrolysis of xanthan gum‐g‐polyacrylamide was carried out in alkaline medium. Four grades of partially hydrolyzed products were synthesized by varying the reaction parameters. The neutralization equivalents of these products were determined by titration with standard sodium hydroxide solution. The flocculation characteristics of all the hydrolyzed graft copolymers and the unhydrolyzed xanthan gum‐g‐polyacrylamide were determined in 5 wt % iron ore and kaolin suspensions. The partially hydrolyzed product with neutralization equivalent of 1000 g showed better performance than that of other partially hydrolyzed products, but all hydrolyzed products exhibited poorer performance than that of the unhydrolyzed product in flocculation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1411–1419, 2004     

Water soluble acrylamide polymers, 2. Aging and viscous flow of aqueous solutions of polyacrylamide and hydrolyzed polyacrylamide

The aging of aqueous solutions of polyacrylamide which appears experimentally as a decrease of solution viscosity and which is probably caused by microorganisms may be prevented by the addition of a small amount (0.02 wt.-%) of an antimicrobial agent such as sodium azide. Aluminium chloride causes a very strong decrease of the viscosity during a prolongated storing time. The addition of aluminium ions to the polymer solution leads to a complexing of amidic groups with aluminium cations and probably also to decrease of the dimensions of individual polymer coils. The viscous flow of aqueous solutions of polyacrylamide and hydrolyzed polyacrylamides was studied as a dependence of the shear gradient D on the shear stress τ and was described by the relation D = k · τⁿ, where k and n denote constants. Both constants depend on the polymer concentration, the degree of polymerization and the content of carboxylic groups in the polymer. The greatest deviations from the Newtonian behaviour were found in the range of molecular weights over 2 · 10⁶ g/mol and practically no deviations were observed for polyacrylamide with molecular weights below 1 · 10⁶ g/mol. The dependence of the viscosity on the shearing time at different shear rates (300, 600 and 1200 s^?1) which was observed in solutions of polyacrylamide, hydrolyzed polyacrylamide and poly-(N,N-dimethyl)-acrylamide was explained by an entanglement model.     

Gel permeation chromatography using controlled-porosity glass. II. Polyacrylamide aqueous solutions

In a study of polyacrylamide in solutions we have required the rapid characterization on chromatographies. The application to the aqueous solution of the GPC using controlled-porosity glass has been examined from both the viewpoint of the effect of salt addition and the GPC mechanism. An adequate addition to neutral salt, 0.005M KCI to the eluent, gave rise to the elution behaviors being in accord with the hydrodynamic volume concept of the GPC separation.     

Molecular weight characterization of poly(acrylamide-co-sodium acrylate). I. Viscometry

Mark–Houwink constants for polyacrylamide and poly(acrylamide-co-sodium acrylate) in 0.2M Na₂SO₄ were measured using eight fractionated samples of polyacrylamide and 26 hydrolyzed polyacrylamide samples. The dependence of K and a on the copolymer compositions was found for the range of acrylate content 6 ～ 40 mol %. A relationship between intrinsic viscosity and acrylate content in the form of square root law was found. Molecular weights of copolymer samples with various compositions were estimated using viscometry with Mark–Houwink equations established in this work. The molecular weights of narrow MWD copolymer samples could be measured with an error of ±5%, whereas those of broad MWD copolymer samples with an error of ±8%.     

耐温耐盐复合交联调剖体系实验研究

使用部分水解聚丙烯酰胺、有机铬和水溶性酚醛为主剂,制备了一种复合交联调剖体系,考察了聚合物及交联剂浓度、矿化度、温度等因素对体系成胶性能的影响。结果表明,体系在矿化度为15 000 mg/L,温度低于90℃的条件下,仍可生成较高强度的凝胶,具有良好耐温耐盐性能。通过单管和双管并联岩心封堵实验来模拟体系对地层的调剖过程,结果表明,体系对单管岩心的封堵率高于96%,突破压力梯度大于35 MPa/m;双管并联岩心实验时,体系对高渗管岩心的封堵率在95%以上,而对低渗管岩心的封堵率低于15%。     

Crosslinking reaction of polyacrylamide with chromium(III)

Summary The crosslinking of initially non-hydrolyzed polyacrylamide with chromium in its +3 valence state was investigated in this work. IR spectra showed that the gelation occurred when the polyacrylamide was hydrolyzed, which implies that the gelation should take place at elevated temperature under neutral condition. The gelation process was monitored by means of viscosity measurement. The addition of acetic acid to the system might lead to the delay of gelation, owing to the synergistic effect of chelating with Cr(III) and acidity.     

Partially imidized,water-soluble polymeric amides. I. Partially imidized polyacrylamide and polymethacrylamide

Five to six million molecular weight polyacrylamide and polymethacrylamides of comparable post-alkaline hydrolysis viscosities were imidized by dissolution and heating in 6N HCl. After alkaline hydrolysis, the imidized polymers demonstrated significantly better retention of viscosity to 2% NaCl than did similar partially hydrolyzed polymers. Viscosities in 0.01% NaCl and resistance to shear were not markedly affected by this modification. It is assumed that this improved performance in brine is the result of chain stiffening due to intrachain imide rings.     

Study of the rheological properties and solution microstructure of progressively cross-linked aqueous gels

A stepwise cross-linking polyacrylamide hydrogel was prepared using the laboratory homemade stepwise crosslinker PVC-PP-Cr and partially hydrolyzed polyacrylamide. The microstructure was investigated by using the scanning electron microscope and dynamic light scattering. The results show that the system has a controllable cross-linking time of 4 ~ 6 h, good heat resistance, and maximum gel strength of >300,000 mPa.S. In terms of viscoelastic behavior, a stepwise cross-linking process between crosslinker and hydrolyzed polyacrylamide (HPAM) is presented, and the viscoelasticity is increased step by step. During the stepwise cross-linking process, the dendritic structure, network structure and lamellar structure to a stable spatial network structure is obtained. Here, the cross-linked structure between polymer molecular chains is formed after addition of the crosslinker, which increases the steric hindrance of macromolecular chains and further enhances the stability of the system. With the gradual release of chromium ions from the PVC-PP-Cr stepwise crosslinker, the gel system is formed continuously. When intermolecular friction stopped increasing, intermolecular entanglement and interaction are enhanced, and elasticity is also increased.     

Partially hydrolyzed polyacrylamide–poly(N-vinylpyrrolidone) copolymers as superabsorbents synthesized by gamma irradiation

Partially hydrolyzed polyacrylamide-co-poly(n-vinyl pyrrolidone) used as a superabsorbent was prepared from acrylamide monomers exposed to γ-rays to become polyacrylamide that was subsequently partially hydrolyzed and was then copolymerized with n-vinylpyrrolidone to obtain a terpolymeric superabsorbent with a water retention value of 1100 times its dried weight. The total dose and dose rate along with the appropriate degree of hydrolysis were investigated for percentage conversion in each polymerization and the extent of water absorption. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:191–203, 1998     

Sedimentation of coal-clay dispersions with a binary polymeric flocculant (short communication)

It was found that a binary flocculant as a composition like block copolymers from partially hydrolyzed polyacrylamide (PAA) and an amidoimide polymer (AIP) effectively forms sediments in coal-clay dispersions, and it can be successfully used for the clarification of process water.     

二氧化氯对部分水解聚丙烯酰胺的降黏作用

研究了二氧化氯对部分水解聚丙烯酰胺（HPAM）的降黏作用,探讨了pH值、温度及其他氧化剂及复配体系对黏度的影响及其降黏作用机理。结果表明,pH值对HPAM黏度的影响较大,复配硫酸亚铁或过氧化氢可明显降低黏度。提出了水解反应和氧化反应都是引起HPAM溶液黏度大幅下降的原因。     

N-叔丁基丙烯酰胺、AMPS与丙烯酰胺共聚物及其水溶液特性的研究

高分子量部分水解聚丙烯酰胺（HPAM）分子结构为线性柔性长链构型。在盐溶液中．由于盐离子的存在减弱了基团间的排斥作用．使分子主链卷曲．流体力学体积减小．导致粘度急剧下降。当分子链上有支链结构的侧基时．由于空间位阻效应,使分子的内旋转受到阻碍,分子链的卷曲度受到限制．使得分子链相对更为伸展．刚性相对更强．分子链流体力学尺寸更大．宏观上表现出高分子聚合物的抗盐增粘性越好．从而提高了聚合物的耐温抗盐性能。     

次氯酸钠氧化法测定聚丙烯酰胺浓度的研究

阐述了次氯酸钠氧化法（浊度法）测定部分水解聚丙烯酰胺浓度的反应机理，研究了聚丙烯酰胺的相对分子质量、次氯酸钠溶液浓度、反应时间对吸光度值的影响，针对大庆油田杏二中三元复合驱采出水中含有碱和表面活性剂、pH值高、黏度大、富集硫化物和亚硫酸根等特点，提出采用过硫酸铵一浊度法检测三元复合驱采出水中聚丙烯酰胺浓度。     

Mark–Houwink–Sakurada constants and dilute solution behavior of heterodisperse poly(acrylamide-co-sodium acrylate) in 0.5M and 1M NaCl

Mark Houwink coefficients and molecular size parameters are presented for 31 unfractionated samples of polyacrylamide and hydrolyzed polyacrylamide in 0.5M and 1M aqueous NaCl. Polymers investigated include polyacrylamide, plus 10, 20, 50, 70, and 100 mol % poly(sodium acrylate). Their solution characteristics were studied by gel permeation chromatography, intrinsic viscosity, and light scattering techniques. A density function and heterodispersity index was assigned to each polymer sample due to the polydispersity of the molecular weight distributions. This technique improves the intrinsic viscosity–molecular weight correlation for heterodisperse commercially synthesized polymer systems. The intrinsic viscosity of these commercial compounds will yield useful estimates of their molecular weight, in spite of their obvious heterogeneity.     

Polyampholyte Hydrogels Based on Aliphatic Diamines

Fibre Chemistry - Polyampholyte hydrogels based on hydrolyzed polyacrylamide and aliphatic diamines (ethylenediamine and 1,3-diaminopropane) with various ratios of starting components were studied....     

pH effects on the solubility of polyacrylamides in hard brines

Solubility tests have been conducted on hydrolyzed polyacrylamide (PAAm) polymers to define the pH range for solubility as a function of the salinity of the solutions. These tests show for the first time that pH is a critical variable determining the solubility of extensively hydrolyzed PAAm in brines containing divalent cations. The pH range for solubility of PAAm and an acrylamide copolymer as a function of aging in synthetic seawater at elevated temperature is also reported. The underlying mechanisms for the pH-dependent solubility behavior observed and the implications for petroleum applications of acrylamide polymers are discussed. © 1995 John Wiley & Sons, Inc.     

Coupled column chromatography for copolymer characterisation

Coupled column chromatography has been performed with two chromatographic systems in which fractions from a size exclusion column are injected into a second column where retention is determined by non-exclusion mechanisms. This has been accomplished by directing the eluent from the first column system through the injection valve of the second column system. The first column system contained crosslinked polystyrene gel with the eluent tetrahydrofuran as good solvent. The second column system contained crosslinked polystyrene gel (or crosslinked polyacrylamide gel) with a mobile phase consisting of a solvent/non-solvent mixture which is a poor solvent promoting non-exclusion mechanisms for statistical copolymers of styrene and n-butyl methacrylate. Separations dependent on copolymer composition as a function of the non-solvent component in the mobile phase and the polarity of the stationary phase in the second column system have been accomplished by isocratic elutions.     

耐温抗盐HPAM/Al~(3+)弱凝胶调剖体系的研制及评价

针对深部调剖对化学剂耐高温抗高盐的要求,采用水解聚丙烯酰胺与实验室自制的交联剂和稳定剂以及一些助剂组成耐温抗盐弱凝胶体系。实验表明,该体系能够耐温100℃,抗盐250 g/L[其中ρ(Ca2+)=4 g/L];对高低渗透层的吸水剖面调整能起到明显的作用,高低渗透层的级差越大,则剖面改善效果越明显;在室内实验条件下,该种调剖剂可以较大幅度地提高采收率(平均提高采收率程度为16.1%)。该体系已经在现场调剖施工中成功应用,效果明显。     

高铁酸钾滤液氧化降解HPAM的研究

采用次氯酸盐法制备高铁酸钾纯品所得高铁酸钾一次滤液,是饱和高铁酸钾和次氯酸钾的碱性混合溶液。直接用于去除废水中部分水解聚丙烯酰胺(HPAM)时,由于二者之间存在着协同作用比单独使用相同当量高铁酸钾或者相同当量次氯酸钾效果更佳。用于高浓度的油田含HPAM废水,COD Cr去除率达70％。     

Rheology of Water-Soluble Polymers: A Comparative Study on the Effect of Monovalent Salt

A comparative study was conducted on three commercial water-soluble polymers: partially hydrolyzed polyacrylamide (Separan AP30—Dow Chemicals), polyethylene oxide (Polyox Coagulant—Union Carbide), and xanthan gum (Keltrol—Kelco). Both the steady shear and the dynamic properties were examined. The presence of salt significantly reduces the viscous and elastic properties of Separan AP30. Negligible changes were observed for Polyox Coagulant. However, some marginal reduction in these properties was evident for xanthan gum at low salt concentration up to c_s of 0.05 M, beyond which no effect was observed. The relationship between the rheological properties of the polymers and the salt concentration is governed by the charged characteristics of the polymer chains. The present study suggests that it is more desirable to use xanthan gum than polyacrylamide in a high-salt environment. Polyethylene oxide is usually avoided due to its cost and low resistance to mechanical degradation.