Water soluble copolymers. 54: N-isopropylacrylamide-co-acrylamide copolymers in drag reduction: Synthesis,characterization, and dilute solution behavior

Copolymers of N-isopropylacrylamide (IPAM) and acrylamide (AM) have been synthesized by free radical polymerization in deionized water using potassium persulfate as the initiator. Copolymer compositions were obtained by elemental analysis and ¹³C NMR. An r₁r₂ value of 0.99 indicates ideal copolymerization with random incorporation of the comonomers in the copolymers. Weight average molecular weights, second virial coefficients, diffusion coefficients, and average diameters were obtained via classical and quasielastic low angle laser light scattering. The molecular weights for all the copolymers and the homopolymers of IPAM and AM ranged from 2.2 × 10⁶ to 5.2 × 10⁶ g/mol. The second virial coefficients in deionized water increased with increasing acrylamide content in the copolymers. The dilute solution properties of the copolymers were studied by turbidimetry, microcalorimetry and viscometry. All the copolymers, with the exception of IPAM-40 (the copolymer synthesized with 40 mole% IPAM in the feed), showed lower critical solution temperatures below 100°C. The solution studies were performed in deionized water, 0.514 M NaCl, and 1 M urea. The properties of the IPAM copolymers were influenced by both hydrophobic associations and hydrogen bonding. In 0.2% (～7mM) sodium dodecyl sulfate, the alkyl chain of the surfactant molecules associates with the IPAM moieties on the copolymer backbone, leading to high intrinsic viscosities and the elevation of the LCST above 100°C.     

Drag reduction effectiveness,shear stability and biodegradation resistance of guargum-based graft copolymers

Guargum is a seed galactomannan and is known to be a shear stable drag reducing agent. However, the aqueous solutions of guargum are very susceptible to microbial degradation. In the present investigation, seven graft copolymers of guargum and polyacrylamide have been synthesized and their drag reduction effectiveness, shear stability, and biodegradation resistance have been determined. It has been shown that the drag reduction effectiveness and shear stability of the graft copolymer depend upon the length of the graft and number of grafts in the molecule. None of the graft copolymer solutions show any microbial degradation up to 10 days.     

Turbulent drag effectiveness and shear stability of xanthan-gum-based graft copolymers

A number of graft copolymers of xanthan gum and polyacrylamide have been synthesized by grafting acrylamide onto xanthan gum using the ceric-ion-initiated solution polymerization technique. The effects of various synthesis parameters such as amount of catalyst, reaction time, and ratio of xanthan and acrylamide on drag reduction effectiveness of the graft copolymers have been studied. The scaling up of grafting reaction has been accomplished in 40-L reactor. The drag reduction effectiveness of the graft copolymers is investigated over a wide range of concentrations and Reynolds numbers. It is shown that the maximum drag reduction obtainable in xanthan gum solutions above 300 ppm can be obtained in solutions of graft copolymers at concentrations of 100–150 ppm. The grafting also improves the shear stability at higher Reynolds numbers. The shear stability of the graft copolymers at constant wall stress has been found to be superior to polyacrylamide and the mixtures of polyacrylamide and xanthan gum. In general, the shear stability of graft copolymers and polyacrylamide is shown to increase with concentration. The drag reduction characteristics and shear stability have been discussed in terms of structural features of the graft copolymers. The drag reduction characteristics of the graft copolymers are found to be similar to those of flexible polymers.     

Effect of cationic surfactant addition on the drag reduction behaviour of anionic polymer solutions

Although extensive research work has been carried out on the drag reduction (DR) behaviour of polymers and surfactants alone, little progress has been made on the synergistic effects of combined polymers and surfactants. In this work, the interactions between drag‐reducing anionic polymer (copolymer of acrylamide and sodium acrylate, referred to as PAM) and drag‐reducing cationic surfactant (octadecyltrimethylammonium chloride, OTAC) are studied. Solutions are prepared using both deionised (DI) water and tap water. The measurement of the physical properties such as electrical conductivity and viscosity are used to determine the surfactant–polymer interactions. The addition of surfactant to the polymer solution has a significant effect on the properties of the system. The critical micelle concentration (CMC) of the mixed surfactant–polymer system is found to be different from that of the surfactant alone. With the addition of surfactant to a polymer solution, a substantial decrease in the viscosity occurs. The observed changes in the viscosity of mixed polymer–surfactant system are explained in terms of the changes in the extension of polymeric chains, resulting from polymer–surfactant interactions. The anionic PAM chains tend to collapse upon the addition of cationic OTAC. The pipeline flow behaviour of PAM/OTAC mixtures is found to be consistent with the bench scale results. The DR ability of PAM is reduced upon the addition of OTAC. At low concentrations of PAM, the effect of OTAC on the DR behaviour is more pronounced. The DR behaviour of polymer solutions is strongly influenced by the nature of water (DI or tap). © 2011 Canadian Society for Chemical Engineering     

Characterization of turbulent drag reduction in rotating disk system

Turbulent drag reduction in a rotating disk apparatus was characterized for a homologous series of polyethylene oxide (PEO) polymers covering a wide range of molecular weights. The concentration dependence of drag reduction in this system was shown to obey an empirical drag reduction equation which had been previously established by Virk et al. for flows in capillary tubes. The linear correlation between polymer concentration and C/DR for different molecular weights of PEO was also obtained. In addition, [C]. defined as a characteristic intrinsic concentration, was found to be extremely useful in normalizing the drag reduction data in one homologous series of PEO.     

Using water-miscible nonionic hydrophobic monomer associating HPAM as drag reducing agent

A water-miscible nonionic surfmer (AC-TX100) was synthesized based on Triton X-100 and acryloyl chloride. Then, a terpolymer P(AM/AA/AC-TX100) was synthesized by free radical polymerization in aqueous solution and intended to be used as drag reducing agent (DRA). The DRA was defined to be P(AM_87.32/AA_12.46/AC-TX100_0.22) according to ¹H NMR and elemental analysis, the molecular weight was 2.12 × 10⁶ g/mol according to scattering method. DRA shows excellent performance in drag reduction (DR). The highest DR rate of 76% can be obtained when DRA concentration is 0.023% in fresh water; while in brine containing 3% NaCl, DR rate decreases, and it is necessary to increase the concentration to 0.05% to ensure that DR rate is higher than 70%. SEM and cryo-TEM show that DRA forms a network structure in aqueous solution, and the tightness of this structure has a direct influence on DR performance. Specifically, DRA molecules stretch into the whirlpools generated by water at high flow rates, reducing the quantity and intensity of whirlpools, thereby lowering the energy loss and the friction. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48362.     

The turbulent drag reduction by graft copolymers of guargum and polyacrylamide

Commercial guargum is known to be a shear stable drag reducing agent. However, the aqueous solutions of guargum start degrading within 8 hrs. of their preparation and after 65 hrs., they degrade completely. In the present investigation, the graft copolymers of guargum and polyacrylamide have been prepared. It has been shown that the purification and grafting enhance the drag reduction effectiveness and biodegradation resistance considerably in guargum.     

The drag reduction of chrysotile asbestos dispersions

The drag reduction (DR) of dispersions of Chrysotile asbestos fibers in aqueous solutions of Aerosol OT and in ethylene glycol, and of glass microfibers in water at a pH of 3 were studied as a function of concentration and temperature with a rotating disc apparatus. Only the dispersions of asbestos in aqueous Aerosol OT showed DR comparable to poly(ethylene oxide) WSR 35 (～500,000 MW), and these dispersions were more fully studied. As was the case with Polyox WSR 35, the asbestos dispersions achieved maximum DR at a concentration of about 200 ppm. They showed no DR temperature dependence at constant Reynolds number at high concentrations but displayed a decreasing DR with increasing temperatures at low concentrations. However, the temperature effect was much smaller for the asbestos dispersions than for Polyox. The asbestos dispersions also showed a much smaller decrease of DR with time at a given disc rotation than was previously measured for poly(ethylene oxide). Electron microscope evidence indicated that less than 10% of the fibers were fully separated, and it is probable that these were the fibers which were primarily active in DR. Hence, if complete separation and dispersion could be accomplished without breaking the fibers, Chrysotile asbestos would be a most potent, not very shear-degradable DR species.     

Turbulent drag reduction by polymer-fiber mixtures

The turbulent drag reduction studies by asbestos fiber mixtures with purified guargum, purified xanthangum, and their graft copolymers have been conducted at low concentration and Re 14000 using turbulent flow rheometer designed by Hoyt. A method for making stock suspension of asbestos fibers is also suggested which gives better drag reduction. It has been found from the present studies that purified guargum–asbestos fiber mixtures give positive synergistic effect even at low concentration and synergism in drag reduction may be caused by a mixture when its constituents are rigid. A simple mixture rule equation having interaction parameter may be used for the prediction of drag reduction by the mixture.     

Influence of grafted copolymer structures (polyacrylamide‐g‐polyoxide) on drag‐reduction

This article reports the results of experiments to synthesize a family of copolymers based on polyacrylamide (PAAM), poly(ethylene oxide) (PEO), and poly(propylene oxide) (PPO) to obtain PAAM‐g‐PEO and PAAM‐g‐PPO copolymers with varied grafted chain lengths and contents. The influence of the chemical structure, composition, and molecular architecture on the drag‐reduction properties was evaluated. The PAAM‐g‐PEO systems were prepared by solution polymerization using hydrogen peroxide as initiator, whereas the PAAM‐g‐PPO systems were obtained by micellar polymerization using potassium persulfate as initiator and sodium dodecyl sulfate as surfactant agent. The synthesized polymers were characterized by carbon‐13 nuclear magnetic resonance (13 C‐NMR) and size‐exclusion chromatography. The drag‐reduction tests were carried out in a capillary viscosimeter in bench scale, and the performance was expressed in terms of drag‐reduction percentage (%DR). The results suggest that, a determined chemical structure for each copolymer family evaluated probably promotes the ideal conformation of the chains under flow, favoring each polymer's drag‐reduction action. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Drag reduction by polymer–polymer mixtures

An extensive study on the turbulent drag reduction caused by the various mixtures of polyacrylamide, purified guargum, xanthangum, and their graft copolymers has been conducted at low concentrations and Re = 14,000 using a turbulent flow rheometer. It has been found in most of the cases that the drag reduction caused by mixtures shows a positive deviation from the linearly additive straight line. This effect is more prominent when the drag reduction caused by both the constituents differ appreciably. In most of the cases, the drag reduction caused by the mixtures is higher than the DR caused by either of the constituent polymers; however, the drag reduction caused by the mixture is less than the sum of the drag reduction caused by both the constituents at their respective concentration in the mixture. It has also been noticed that there is no evidence of synergism in these mixtures at low concentrations.     

Fabrication,structures, and properties of acrylonitrile/methyl acrylate copolymers and copolymers containing microencapsulated phase change materials

The polyacrylonitrile‐methyl acrylate (AN/MA mole ratio 100/0–70/30) copolymers and copolymers (AN/MA mole ratio 85/15) containing up to 40 wt % of microencapsulated n‐octadecane (MicroPCMs) are synthesized in water. The MicroPCMs were incorporated at the step of polymerization. The effect of the MA mole ratio and MicroPCMs content on structures and properties of the copolymers were studied by using Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (¹H NMR), scanning electronic microscope (SEM), differential scanning calorimetry (DSC), thermogravimetry analysis (TG), gel permeation chromatography (GPC), and X‐ray diffraction (XRD). The feeding ratio agreed well with the composition of the AN/MA copolymers. The copolymers are synthesized in the presence of MicroPCMs. The melting point moves to lower temperature (206°C), while the decomposition temperature moves to higher temperature (309°C) with increasing of the MA mole ratio and microcapsules content. The number–average molecular weight of the copolymer is ～30,000. The crystallinity of the copolymer decreases with increasing of the MA mole ratio and microcapsules content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2776–2781, 2007     

Synthesis and characterization of waterborne polyurethane acrylate copolymers

Polyurethane acrylate copolymers were synthesized by emulsion polymerization process. To reduce the environmental hazards, organic solvents were replaced by eco-friendly aqueous system. Concentration of polyurethane and acrylate monomer was varied to investigate the effect of chemical composition on performance properties of copolymers. FTIR spectroscopy was used as a key tool to record the chemical synthesis route. The synthesized copolymer emulsions were characterized by evaluating their particle size, viscosity, dry weight content, chemical and water resistance. Thermal decomposition was studied by thermogravimetric analysis. Scanning electron microscope was used to visualize the morphological structure of copolymers. The experimental results indicate better polyurethane acrylate compatibility till the ratio of 30/70. However, these copolymers exhibited synergistic effects between the two polymers and revealed a remarkable improvement in numerous coating properties.     

壁面微沟槽与表面活性剂耦合对管道中湍流减阻特性的影响

通过矩形管道压降实验研究了壁面微沟槽和表面活性剂的减阻性能及联合减阻的增益效果,用粒子成像测速仪分析了流场特性。实验所用的微沟槽为3种不同结构的顺流向V形沟槽,表面活性剂为十六烷基三甲基氯化胺(CTAC),水杨酸钠(NaSal)作为补偿离子。结果表明,壁面微沟槽和表面活性剂溶液均有减阻效果,二者耦合后减阻率进一步提升,最高减阻率为48.26%。微沟槽的减阻性能主要作用在近壁区,通过影响边界层平均流速、速度脉动强度和涡结构,减少表面活性剂的湍动能损耗。当超过表面活性剂的临界雷诺数后,沟槽尖端的高剪切力会加剧胶束结构分解。表面活性剂能抑制湍流涡的演变,扩大微沟槽有效减阻的雷诺数范围。     

Synthesis and crosslinking of partially disulfonated poly(arylene ether sulfone) random copolymers as candidates for chlorine resistant reverse osmosis membranes

Biphenol-based, partially disulfonated poly(arylene ether sulfone)s synthesized by direct copolymerization show promise as potential reverse osmosis membranes. They have excellent chlorine resistance over a wide range of pHs and good anti-protein and anti-oily water fouling behavior. Crosslinking of these copolymers that have high degrees of disulfonation may improve salt rejection of the membranes for reverse osmosis performance. A series of controlled molecular weight, phenoxide-endcapped, 50% disulfonated poly(arylene ether sulfone)s were synthesized. The copolymers were reacted with a multifunctional epoxy resin and crosslinked thermally. The effects on network properties of various factors such as crosslinking time, copolymer molecular weight and epoxy concentration were investigated. The crosslinked membranes were characterized in terms of gel fraction, water uptake, swelling and self-diffusion coefficients of water. The salt rejection of the cured membranes was significantly higher than that for the uncrosslinked copolymer precursors.     

Copolymers of N‐alkyl‐ and N‐arylalkylacrylamides with acrylamide: influence of hydrophobic structure on associative properties. Part I: viscometric behaviour in dilute solution and drag reduction performance

BACKGROUND: Drag reduction properties from dilute aqueous polymer solution are obtained with very high molecular weight water‐soluble polymers. The aim of this work was to examine the potential of acrylamide polymers modified with small amounts of N‐alkyl‐ and N‐arylalkylacrylamides (0.5 and 1 mol%). RESULTS: The associative properties improve with the length of the graft alkyl chain, and with its proportion in the copolymer and with the presence of aromatic groups. The drag reduction efficiency of these copolymers in very dilute solution was measured to relate the activity to the molecular parameters. CONCLUSION: The results obtained indicate that the persistent drag reduction activity can be linked to the presence of strong intramolecular associations. Copyright © 2008 Society of Chemical Industry     

Study of oil soluble polymers as drag reducers

This investigation was undertaken to find the most effective material which would reduce the friction coefficient in turbulent flow when added in small quantities to oil pipelines. For this purpose, a series of oil-soluble polymers, namely homopolymers and copolymers of alkyl methacrylates, alkyl acrylates, and alkyl styrenes were synthesized. Emulsion polymerization techniques were used. Commercially available alkyl methacrylate and alkyl acrylate monomers were used in the synthesis. Monomeric alkyl styrenes were synthesized and structures established prior to polymerization. Intrinsic viscosities were measured and viscosity average molecular weights were calculated for several of the homopolymers synthesized in this study. Reduction of factional drag and resistance to shear degradation were measured by pumping a solution of the polymer in a hydrocarbon solvent through a pipe and recording the pressure drop across the pipe. Drag-reducing properties of several of the polymers were correlated in terms of their viscosity average molecular weights. Drag reduction of poly (isodecyl methacrylate) was studied in various hydrocarbon solvents. Drag-reducing behavior of polymers prepared in this study exhibited a strong dependence on molecular weight; increasing the molecular weight increased the drag reduction for a given polymer concentration and pipe size. Several of these polymers were found to be superior to commercially available polyisobutylene as drag reducers, especially in terms of shear stability.     

Polysulfone-based amphiphilic copolymers: Effect of hydrophilic content on morphology and performance of ultrafiltration membranes

A series of polysulfone (PSf)-based amphiphilic graft copolymers were synthesized to investigate the effects of copolymer composition on membrane morphology and performance. PSf-based ultrafiltration membranes were prepared by phase inversion method using the blends of PSf and PSf-g-poly(ethylene glycol) methyl ether methacrylate (PEGMA) copolymers. Membranes were evaluated in terms of pure water permeability, flux recovery ratio (FRR), protein rejection, and contact angle. The morphology of the membranes was investigated by scanning electron microscopy. Contact angle of membranes was decreased from 85.7° to 51.6°, while the FRR was greatly increased from 55 to 95% upon increasing the PEGMA content of copolymers from 20 to 70 wt %. Results indicated that the ratio of hydrophilic/hydrophobic segments in amphiphilic structures is one the key parameters that control the phase inversion process by altering miscibility, viscosity, and wettability of casting solutions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48306.     

Chemical synthesis,characterization, and properties of conducting copolymers of imidazole and pyridine

A series of conducting copolymers were synthesized by chemical oxidative polymerization of imidazole (Imi) and pyridine (Py) in acetonitrile medium at ambient temperature. The yield, solubility, and conductivity of the copolymers were measured by changing the Imi/Py molar ratio from 0/100 to 100/0. The as‐prepared Imi/Py conducting copolymers were characterized by UV‐Visible, FTIR, ¹H‐NMR, DSC, TGA, and XRD. The results suggest that the resulting copolymers were more easily soluble in most of the organic solvents than in polyimidazole. The polymer obtained is a real copolymer containing imidazole and pyridine units, but the Imi content calculated on the basis of the proton NMR spectra is lower than feed Imi content. The thermostability of the Imi/Py copolymer increases with increasing Imi unit content. The copolymers show comparatively higher conductivity and higher thermal stability than the homopolymer polypyridine and are lower than those of polyimidazole. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis,characterization, and aqueous solution behavior of copolymers of acrylamide and sodium 10-acryloyloxydecanoate

A new water-soluble monomer of sodium 10-Acryloyloxydecanoate (NaAD), which possesses a hydrophobic group and an ionizable group, was synthesized from acryloyl chloride and 10-hydroxydecanoic acid, and the series of copolymers of NaAD with acrylamide (AM) were prepared by the free radical polymerization in aqueous solution using ammonium persulfate as the initiator. The feed ratio of NaAD:AM was varied from 5:95 to 70:30 mol%, with the total monomer concentration held constant at 0.5 M. The copolymer compositions were determined from elemental analysis. The molecular weights of the copolymers were determined by gel permeation chromatography ranged from 0.76 × 10⁶ to 1.37 × 10⁶ g/mol. All copolymers were soluble in deionized water and salt solutions at pH > 5. The dilute and semidilute solution behavior of the copolymers was studied as a function of composition, pH, and added electrolytes, and the results indicated that NaAD30 exhibited much higher viscosity values. At moderate pH values, the copolymers coils become slightly more expanded and intermolecular association interactions occur, which was indicated by fluorescence and apparent viscosity measurements. Upon the addition of NaCl and in low pH, viscosities tended to decrease because of the disruption of the intermolecular associations.