Thermogelation of methylcellulose from solution in N,N‐dimethylformamide and characterization of the transparent gels

A transparent gel was prepared through the cooling of a methylcellulose (MC) solution in N,N‐dimethylformamide (DMF) at 80°C to a lower temperature. The temperature at which gelation occurred was dependent on the concentration of the solution. The gel temperature increased with an increase in the concentration of MC. The gelation of MC in DMF was studied by means of optical microscopy (OM), differential scanning calorimetry, and dynamic mechanical analysis (DMA). The OM studies revealed the presence of loosely bound beads of MC with DMF at a lower concentration. These beads became interconnected to rods, and subsequently, a continuous, thick gel was formed as the concentration increased. From DMA studies, it was observed that the loss modulus of the gel crossed over the storage modulus at two different frequencies. This indicated the presence of two types of network structures generated from the weak and strong associations of MC with the organic solvent DMF. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Studies on rheological,thermal, and morphological properties of methylcellulose gel in aqueous medium

The rheological, morphological, and thermal behavior of aqueous methylcellulose (MC) gels was investigated by optical microscope, dynamic mechanical analyzer (DMA), and differential scanning calorimeter. The double crossover between the storage modulus and loss modulus during the frequency scan in DMA suggests the transition from gel to sol state. These gel networks are comprised of bead‐rod structures, which is visible under the optical microscope. Furthermore, the degelation mechanism of gels comprises of the thermodynamic viable bead burst phenomenon. The reheated samples of MC under dynamic compression show partial irreversibility of the MC aqueous system, indicating the possible presence of weakly coupled random coils and helix. The phenomenon of turbidity of MC aqueous gels is discussed with the help of a large bead model, in which the small‐sized beads present in aqueous solution collide with each other to form large beads. POLYM. ENG. SCI., 59:2024–2031, 2019. © 2019 Society of Plastics Engineers     

Micelle formation in mixtures of nonionic and cationic detergents

The effect of a homologous series of polyoxyethylene n-dodecanols on the critical micelle concentration (cmc) of mixtures with n-dodecyl trimethyl ammonium bromide (DTAB) and of polyoxyethylene n-hexadecanols on the cmc of mixtures with n-hexadecyl trimethyl ammonium bromide (CTAB) has been studied in terms of the composition of the mixtures. The cmc of the nonionic component of the mixed micelles is approximately one hundredth of that of the cationic component. Only a gradual increase in the cmc values of the mixed micelles above the values of the nonionic components was observed in the composition range of 0–75 mole % or 0–90 mole %, respectively, of cationic detergent. This is followed by an abrupt transition to the high cmc values of the cationic component. This abrupt transition is considerably reduced by addition of NaBr. It is postulated that in the absence of added electrolyte the degree of ionic repulsion of the cationic component in mixed micelles is markedly decreased as the proportion of nonionic component reaches a threshold range of 25 or 10 mole %, respectively. Swamping of charges reduces ionic repulsion in NaBr solutions and, consequently, the abrupt transition in the cmc vs. composition curves is reduced.     

Rheological properties of methylcellulose aqueous gels under dynamic compression: Frequency sweep and validity of scaling law

The aqueous methylcellulose (MC) gels are characterized with a dynamic mechanical analyzer (DMA) under dynamic vertical compression. During the frequency sweeps of MC gels at different temperatures, the storage modulus is observed to be higher than loss modulus at lower frequencies. Both of the storage and loss modulus increases with frequency, but the rate of increase is higher for loss modulus. This leads to the first crossover between E′ and E″ during the frequency scan. For the frequency scan at a high temperature (80°C), a higher rate of increase is observed in storage modulus beyond the first crossover frequency. This leads to the second crossover between storage and loss modulus. Optical microscopy results indicate the presence of core–shell microstructure in aqueous MC gels. The first crossover is possibly due to the shell–sol transition, whereas the second crossover is due to the sol–shell–core transition. The validity of scaling laws at and around the first‐crossover point (shell–sol transition) is checked. The scaling law is valid at the first‐crossover point, but it is invalid around it. Alternate scaling equations based on reduced parameters are also used to check the universality. Irrespective of temperature, scaling laws are valid for reduced parameters. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of Hydrophobic Modification on the Properties of Polymer‐Blended Microemulsion Gels

Phase behavior of sodium oleate (NaOl)/isoamyl alcohol‐based lamellar gel phase in cedar oil/water medium in the presence of the nonionic polymer hydroxyethyl cellulose (HEC) and its hydrophobic modified product (HMHEC) is investigated for the development of polymer‐embedded surfactant gels. HMHEC is more soluble in oil‐in‐water (o/w) microemulsions, but nonionic HEC shows limited solubility in the lamellar microemulsion (o/w type). Quantitative estimation of rate of adsorption of the polymer on lamellae bilayers can be easily done by Sudan solubilization and methylene blue complexation methods. Addition of HMHEC to the lamellar gel phase increases the polymer solubilization limit of lamellar gels as well as the viscoelasticity and thermal stability. The polymer‐embedded microemulsion gel acts as a “clean gel” since it exhibits good solubilization in different hydrocarbon media at ambient conditions. Elastic modulus of the polymer‐embedded gel influences directly the suspension performance of gels at high temperature and yields a reasonable sand‐settling velocity acceptable according to fracturing standards. The thermal characteristics and viscoelastic properties of polymer‐embedded gel were found to be suitable for moderate‐temperature reservoir stimulation where the bottom hole temperature is in the range 70–75 °C. Already a large amount of experimental data on pure microemulsions (without polymer) exists. Our studies indicate that the developed polymer‐embedded microemulsion gel has great potential as a model system for the study of polymer–microemulsion interactions.     

Effects of surfactants on rheological properties of a dispersed viscoelastic microsphere

The swelling ratio is an important performance for the application of viscoelastic microsphere. The reduction of swelling ratio can affect the particle size. The compatibility between particle size and formation pore can affect the plugging performance and EOR capability. Adsorption characteristics of cationic surfactant cetyltriethylammnonium bromide (CTAB), anionic surfactant petroleum sulfonate applied in GangXi oilfield (GXPS), and nonionic surfactant nonylphenol ether (TX‐10) onto viscoelastic microspheres and the effect of the three types of surfactant on swelling ratio of viscoelastic microspheres were investigated. Effects of surfactants on rheological properties of viscoelastic microspheres were researched in two different modes referring to steady shear and dynamic shear, respectively, using Physica MCR301 Rheometer. The results showed that the interactions between viscoelastic microsphere and surfactants CTAB were electrostatic attraction and hydrophobic association, that the interaction between viscoelastic microsphere and surfactants TX‐10 was just hydrophobic association, and that the interactions between viscoelastic microsphere and GXPS were electrostatic repulsion and hydrophobic association. At the same initial surfactant concentration, all these three types of surfactant could be adsorbed onto the surface of viscoelastic microspheres and reduce its swelling ratio and storage modulus. Because of different amount of adsorption, the extent of reduction order on swelling ratio and storage modulus was CTAB>TX‐10>GXPS. In addition, the yield stress of viscoelastic microspheres which was obtained from modeling the data to Herschel‐Bulkley model decreases with the increase of surfactant adsorption. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42278.     

Some Surface Properties of Polysorbates and Cetyl Trimethyl Ammonium Bromine Mixed Systems

Mixed surfactant solutions consisting of cationic/nonionic surfactants were prepared in different compositions of the components in aqueous solution in order to determine the surface properties. The critical micelle concentration (CMC) of aqueous solutions of the individual surfactants cetyl trimethyl ammonium bromide (CTAB) and polysorbate nonionics, and their mixtures are determined at different proportions. The results show that there is synergistic behavior in mixtures at higher mole fraction of nonionic surfactant. The effect of the alkyl chain on the CMC is also determined.     

Thermoreversible hydrogels. XVIII. Synthesis,swelling characteristics,and diffusion behaviors of porous,ionic, thermosensitive hydrogels

Porous, ionic, thermosensitive hydrogels were prepared from N‐isopropylacrylamide, a cationic monomer [trimethyl (acrylamido propyl) ammonium iodide (TMAAI)], an anionic monomer [acrylic acid (AA)], a zwitterionic monomer [N′,N′‐dimethyl (acrylamido propyl) ammonium propane sulfonate], or a nonionic monomer [poly(ethylene glycol) methyl ether acrylate], and a pore‐forming agent [poly(ethylene glycol) (PEG)] of different molecular weights. Some fundamental properties and dynamic swelling kinetic parameters and solute permeation for these porous gels were investigated. The results showed that the gel containing the cationic monomer TMAAI had a higher equilibrium swelling ratio. The diffusion coefficients showed that the swelling rates for the gels with the anionic monomer AA and PEG with a higher molecular weight (20,000) were faster. The results showed that the fast swelling–deswelling behavior for the porous structure gels was due to them being more available than the gels with long hydrophilic side chains. In addition, the interactive force between the solutes and gels and the solute permeation through the porous gels were investigated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2214–2223, 2003     

Synthesis and rheological properties of polystyrene/layered silicate nanocomposite

Exfoliated polystyrene (PS)/organo-modified montmorillonite (MMT) nanocomposites were synthesized through in situ free radical bulk polymerization by dispersing a modified reactive organophilic MMT layered silicate in styrene monomer. The original MMT was modified by a mixture of two commercial cationic surfactants, [2-(acryloyloxy)ethyl](4-benzoylbenzyl)dimethylammonium bromide (ADAB) and cetyltrimethylammonium bromide (CTAB), with the former containing a polymerizable vinyl group. The exfoliating and intercalating structures were probed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Comparing with pure PS, the nanocomposites show much higher decomposition temperature, higher dynamic modulus, stronger shear thinning behavior and a smaller die swell ratio. The leveling-off of the storage modulus at low frequencies in the oscillatory shear measurements, as well as the observed yield like behavior, implies that the formation of a percolating nanoclay network is the origin of the enhanced viscoelasticity in these composites.     

Effect of Surfactants on Catalytic Activity of Diastase α-Amylase

The enzyme amylase is one of the hydrolyzing enzymes used in detergent formulation in order to remove soil based on polysaccharides. The effectiveness of the enzyme depends on its compatibility with other ingredients of the formulation. Among the studied additives, comprising anionic surfactants sodium dodecyl hydrogen sulfate (SDS) and dioctyl sodium sulfosuccinate, the cationic surfactant cetyl trimethyl ammonium bromide (CTAB), nonionic surfactants polyoxyethylene sorbitan monooleate and polyoxyethylene octyl phenyl ether, carboxy methyl cellulose and sodium sulfate, only the anionic surfactant SDS and cationic surfactant CTAB showed catalytic enhancement of α-amylase. The kinetic parameters, K _m and k _cat, showed an increase in catalytic activity in the micellar pseudophase. The decrease in optimum temperature from 55 to 30 °C and the shift in optimum pH from 5.5 to 7 on the addition of SDS and CTAB for the hydrolysis of starch are very favorable to enhance the washing characteristics.     

Effects of modified attapulgite on the properties of attapulgite/epoxy nanocomposites

The aim of this work is to figure out the true effects of filler modification in attapulgite (ATP)/epoxy (EP) nanocomposites through comparing the properties of composites containing pristine or modified ATP clay. ATP particles were first pretreated by a silane coupling agent KH550 and cationic surfactant cetyl trimethyl ammonium bromide (CTAB) separately, and then a series of nanocomposites were prepared with varied clay loadings. Fourier transform infrared spectroscopy and thermogravimetric analysis were used to confirm the modification. The wicking experiment showed the compatibility of ATP with EP increased after modification, especially for CTAB‐ATP, which was discovered to exhibit the highest affinitive ratio. Mechanical and thermal properties of the composites were enhanced on the introduction of ATP. Regarding the efficiency of mechanical reinforcement, KH550 was superior to CTAB at lower ATP loadings (<2 wt%), whereas CTAB became relatively more effective at higher loadings. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers     

Synthesis and characterization of polyurethane/montmorillonite nanocomposites by in situ polymerization

In this paper, a new type of organophilic montmorillonite, co‐treated with cetyltrimethyl ammonium bromide (CTAB) and 4,4′‐diphenymethylate diisocyanate (MDI), was modified and applied to prepare polyurethane/montmorillonite nanocomposites via in situ polymerization. The nanoscale montmorillonite layers were exfoliated and dispersed relatively homogeneously in the polyurethane matrix, and characterized by X‐ray diffraction and transmission electron microscopy. The thermal degradation temperature of the nanocomposites increased, as compared with pristine polyurethane. Dynamic mechanical analysis confirmed the constraining effect of exfoliated montmorillonite layers on polyurethane chains, which benefited the increased storage modulus and increased glass transition temperature. Tensile tests showed that the exfoliated nanocomposites were reinforced and toughened by the addition of nanometer‐size montmorillonite layers. Copyright © 2006 Society of Chemical Industry     

Effect of organophilic montmorillonite on polyurethane/montmorillonite nanocomposites

Different kinds of organophilic montmorillonite cotreated by cetyltrimethyl ammonium bromide (CTAB) and aminoundecanoic acid (AUA) were synthesized and applied to prepare polyurethane/montmorillonite nanocomposites via solution intercalation. The results of wide‐angle X‐ray diffraction (WAXD) and transmission electron microscopy showed that, for the montmorillonite modified with CTAB and CTAB/AUA (molar ratio of 1/2), an ordered intercalated nanostructure was derived, while for the montmorillonite treated with AUA, a disordered nanostructure was derived. The tensile properties of the polyurethane (PU) nanocomposites showed higher enhancement relative to PU matrix. TG showed that there is some enhancement in degradation behavior between the nanocomposites and PU matrix. DMTA results showed that nanocomposites from some organophilic montmorillonites showed a much higher storage modulus below and above glass transition temperature, while the nanocomposites from montmorillonite treated by AUA show an even lower storage modulus. The loss curves showed that the main glass transition temperature of PU was improved to some extent for the nanocomposites. The water absorption of PU and nanocomposites was also studied and the difference in reduction was thoroughly analyzed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2536–2542, 2004     

Chemically modified oil palm ash‐filled natural rubber composites and its properties

Chemically modified Oil Palm Ash (OPA)‐filled natural rubber composites were prepared by modifying the functional group of OPA with cetyltrimethylammonium bromide (CTAB) prior to compounding by using laboratory conventional laboratory‐sized two‐roll mills. The functional groups of CTAB‐modified OPA were analyzed by using Fourier Transform Infrared (FTIR) and compared with those of non‐modified ones. The CTAB‐modified OPA‐filled NR composites showed shorter scorch time and cure time as compared to those of non‐modified OPA, which was attributed to the new functional groups occurred. The tensile test results showed that the OPA‐filled NR composites with CTAB modification exhibit improvement in tensile strength, tensile modulus, and hardness but lower elongation at break as compared to nonmodified ones. The tensile fractured surface of modified OPA filled NR composites revealed the well embedded and better distribution of CTAB‐modified OPA in NR matrix. The toluene uptake was also found to be lower for the modified OPA‐filled NR composites and showed better rubber–filler interaction; it further showed that surface modification with CTAB could compatibilize the OPA particles and NR matrix. POLYM. COMPOS., 35:691–697, 2014. © 2013 Society of Plastics Engineers     

Photopolymerization and characteristics of reactive organoclay–polyurethane nanocomposites

Polymerizable ammonium surfactants with two methacrylate alkyl chains were successfully synthesized via Michael‐Addition and quaternization reaction. Organoclays containing reactive methacrylate groups were prepared by cationic exchange process. Intercalated nanocomposites have been produced by UV initiated polymerization with different organophilic clay loading. X‐ray diffraction (XRD) spectroscopy showed that the d spacing of organoclay increased with increment of methacrylate alkyl chains length. When organoclay were dispersed in urethane acrylate resin, and photopolymerized, the d spacing increased, but the increasing extent decreased with increment of the methacrylate alky chains length. Thermogravimetric analysis indicated that incorporation of reactive organoclay had better thermal stablity than cetyltrimethylammonium bromide (CTMA)‐modified organoclay and dynamic mechanical analysis (DMA) showed nanocomposites containing reactive organoclay had high glass transition temperature and storage modulus. Tensile analysis implied that incorporation of reactive organoclay could enhance mechanical and tensile properties dramatically. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Rheological characterization of the gel point in polymer‐modified asphalts

In this work, the rheological characterization of the gel point in polymer‐modified asphalts is carried out. The viscoelastic properties of polymer‐modified asphalts, in which the polymer is styrene–ethylene butylene–styrene (SEBS) with grafted maleic anhydride (MAH), were measured as a function of MAH concentration. The crosslinking reaction that leads to gelation is characterized by power‐law frequency‐dependent loss and storage modulus (G″ and G′). The relaxation exponent n (a viscoelastic parameter related to the cluster size of the gel) and gel strength S (related to the mobility on the crosslinked chain segments) were determined. The value of the power‐law exponents depends on the composition of polymer, ranging from 0.30 to 0.56, while the value of the rigidity modulus at the gelation point (S) increases with the amount of reactive groups of the modifier polymer. Both n and S are temperature‐dependent in the blends. The blends containing gels present a coarse morphology, which is related to the rheological properties of the matrix and dispersed phase. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

不同因素对CTAB/TX-100微乳液相图的影响

用ε-β"鱼状"相图法研究了阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)与非离子表面活性剂辛基苯酚聚氧乙烯(10)醚(TX-100)以不同摩尔比复配形成的CTAB/TX-100/醇/油/NaCl水溶液微乳液体系的相行为和增溶性能.结果表明,随着醇浓度的增加,体系由水包油型(O/W)(winsor Ⅰ or (2-)...     

Effect of geometry and surface properties of silicates on nanostructuration of suspension in precursors of an epoxy/amine network

Several lamellar silicates (Montmorillonite, Hectorite, Mica) showing different host structures and aspect ratios were modified with octadecylammonium ions by a cationic exchange process. The resulting organoclays were characterized using thermal gravimetric analysis and X‐ray diffraction, which allowed us to estimate the amount of surfactants within the organoclays and their organization in the interlamellar spacing. Some local pseudo‐organizations were found and checked by differential scanning calorimetry (DSC). The interactions of organophilic silicates were evaluated, without any shear, with the precursors of a rubbery epoxy/amine network. These silicate/monomers interactions were monitored via the measurements of the interlamellar swelling, the surface energies and the physical gel formation. The organoclays used form gels in the monomers above the percolation threshold if no shear is applied and present a gel/sol transition at a critical shear stress. Gel strength determined from storage modulus and viscosity values determined at high shear rates reveal different organizations of clay in the monomers depending on the silicate aspect ratio and silicate/monomers interactions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1380–1390, 2006     

An experimental study of interaction between surfactant and particle hydrogels

Polyacrylamide gel was synthesized to study interaction between surfactant and particle hydrogel. Surfactants used in this study include cationic surfactants, n-dodecylpyridinium chloride, (1-hexadecyl) pyridinium bromide; anionic surfactants, sodium salt of dodecylbenzene sulfonic acid, sodium 4-n-octyl benzene sulfonate and sodium branched alcohol propoxylate sulfate; and nonionic surfactants, Igepal^® CO-530, Tergitol^® NP-10 and Neodol^® 25-12. It has been found that, after swelling of the dry particles, surfactant concentration shows a substantial increase. Meanwhile, dynamic modulus (G′ and G") of the gels shows a significant decrease in the surfactant solutions. Based on the experimental results, a mechanism has been proposed to elucidate the reduction of the gel dynamic modulus. Furthermore, this mechanism was discussed through surfactant critical packing parameters (CPP) at the interface of the hydrogel particle and surfactant aqueous solution, and confirmed by recovery of the gel dynamic modulus after removal of the surfactant from the hydrogels.     

乳化剂十六烷基三甲基溴化铵对木材用淀粉胶粘剂使用性能的影响

研究了乳化剂十六烷基三甲基溴化铵（CTAB）的添加对木材用淀粉胶粘剂粘接性能、粘度、流动性、贮藏稳定性的影响,并对其作用机理进行了初步探讨。实验结果表明,CTAB的添加会导致木材用淀粉胶粘剂压缩剪切强度的小幅下降,但可以降低淀粉胶粘剂的粘度,明显改善玉米淀粉胶粘剂的流动性,提高淀粉胶粘剂的贮藏稳定性;CTAB添加量以占淀粉干基质量1.5%为宜,其所改性的木材用淀粉胶粘剂具有良好的使用性能。差示扫描量热仪（DSC）和扫描电子显微镜（SEM）分析可知CTAB的作用机理可能是阻碍了淀粉分子的聚集,从而抑制了淀粉的短期回生和长期回生。