Scanning Electron Microscopy Investigation for Monitoring the Emulsion Deteriorative Process and Its Applications in Site-Directed Reaction with Paper Fabric.

The O/W isocyanate emulsion can be used as a sizing agent to improve the waterproof performance of paper. However, the -NCO content in the emulsion diminishes with the prolongation of standing time. What is happening to this seemingly stable emulsion, especially concerning its microstructure evolution? We propose to monitor the emulsions deteriorative process by combining freeze-drying technique and SEM. Thus, the emulsion containing -NCO active group was obtained by the synthetic polymer emulsification of HDI trimers. The results of SEM demonstrate that the emulsion deteriorative process actually represents the collapsing and fusion of stable honeycomb structure with the prolongation of standing time and increasing temperature. This is possibly due to the fact that the inner aggregative HDI trimers are reacting with outside water to form urethane macromolecules, and this results in the collapsing and fusion of the honeycomb structure, as observed in SEM images. Moreover, the measurement results of -NCO content and FT-IR spectroscopy present the -NCO content as reducing with increasing standing time and temperature. This conclusion further proves our hypotheses. Additionally, the emulsions are used to treat the paper by site-directed reaction. The results show that the with the increase of the standing time and temperature, the contact angles and surface free energy show a decrease and an increase, respectively, whereas surface free energy appeared at a minimum of 29.19 mJ·m-2 when the standing time and temperature was 1 h and 25 °C.

Rheological and fracturing characteristics of a novel sulfonated hydroxypropyl guar gum.

A series of sulfonated hydroxypropyl guar gum (SHG) samples with different degrees of substitution (DSs) were prepared, and the SHG solution and SHG fracturing fluid were prepared and analyzed. The SHG aqueous solutions with different DSs all exhibit shear thinning behavior, which is well correlated with the Ostwald-deWaele model. Owing to the electrostatic repulsion of SHG molecular chains, SHG solutions with a higher DS will exhibit weaker thixotropic performance and strong anti-salinity ability. In addition, the SHG fracturing fluids, which were formed by interactions between SHG and organic zirconium, exhibit good temperature- and shear-resistant properties, proppant suspension properties, and salt tolerance. Furthermore, SHG gel-breaking fluids show low interfacial and surface tensions, with low residue content and small core permeability damage. These results provide useful indicators for the applications of SHG in the oil field industry.

Carboxymethyl fenugreek gum: Rheological characterization and as a novel binder for silicon anode of lithium-ion batteries.

The rheology of carboxymethyl fenugreek gum (CFG) is characterized and applied it as a binder for the silicon anode of lithium-ion batteries (LIBs). First, a series of carboxymethyl fenugreek gum (namely CFG-1, CFG-2 and CFG-3) was prepared and characterized by Fourier transform infrared spectrophotometer and hydrogen nuclear magnetic resonance spectrometry studies. In rheological measurements, the CFG solutions show higher flowability, weaker viscoelastic behavior and better thixotropy than that of fenugreek gum (FG) solution. Furthermore, the higher degrees of substitution (DS) of CFG solutions lead to lower apparent viscosity and higher flow index, weaker elastic effect and smaller relaxation time, and higher viscosity recoverability than those obtained for lower DS of CFG solutions. In electrochemical measurements, the polar hydroxyl and carboxyl groups in the CFG skeleton chain provide bonding points between the CFG binders and the silicon electrode to produce binder-silicon bonds, which cause strong hydrogen bonding, and resulted in excellent electrochemical stability and specific capacity. The electrochemical performances were measured via the silicon electrodes with FG and CFG at 5 wt% content. As the DS is increased, the initial Coulombic efficiency can increase from 88.74% to 91.3%. When the electrode undergoes a volume change, the CFG binder with silicon electrodes can hold high capacity of above 1500 mAh/g after 200 charge-discharge cycles. Therefore, the carboxymethyl fenugreek gum as a binder may also be a novel extended binder-design, with applications for silicon anodes of LIBs.

Thermosensitive behavior of hydrophobically associating anionic guar gum solutions and gels.

Herein, we describe the syntheses of novel thermoassociating anionic guar gums (TGGs) with long aliphatic and polyethylene glycol (PEG) segments and characterize these gums by Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. Additionally, we explore the properties of TGG solutions and gels by viscometry, dynamic light scattering, fluorescence spectroscopy, and rheometry, revealing the thermoresponsive behavior of these systems. Thus, TGG solution viscosity increases with decreasing PEG segment length below 35°C, with an opposite trend observed at 60°C. Similarly, the critical association concentration increases with increasing PEG segment length at room temperature, with an opposite dependence detected at 50°C. High temperature results in almost complete hydrophobization of PEG segments, endowing TGG solutions with unique thermoassociating behavior. Moreover, TGG gels feature both coordination and physical crosslinking, with the latter enhanced by increased hydrophobic group length, and therefore exhibit viscosities much higher than that of the parent sulfo-hydroxypropyl guar gum (SHG) gel. The storage moduli of TGG gels reach their maxima with increasing temperature. Additionally, the addition of NaCl increases the viscosities of TGG gels to maximum values exceeding that of the SHG gel.

Self-assembly and rheological behaviors of intermacromolecular complexes consisting of oppositely charged fluorinated guar gums.

We synthesized fluorinated cationic/anionic guar gums (FCGG and FAGG) and characterized these species using Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. The degree of fluorine substitution of FCGG (0.26%) and FAGG (0.21%) was calculated by elemental analysis. In addition, we explored the self-assembly and rheological behaviors of FCGG-FAGG complexes by viscometry, scanning electron microscopy, light scattering, fluorescence spectroscopy, and rheometry. The maximum viscosity and molecular weights were observed with a FAGG:FCGG mass ratio of 7.0:3.0, denoted by COMP. Moreover, FAGG-FCGG interactions in COMP led to the lowest shape factor and critical associating concentration. Additionally, the relaxation time and crossover modulus of COMP (6.65 s and 0.90 Pa, respectively) were remarkably higher than those of FCGG and FAGG alone. Finally, viscoelastic hysteresis loops emerged for FAGG and COMP. The results suggested that the self-assembly behaviors of FAGG-FCGG were influenced by both ionic and fluorinated groups.

Fluorinated anionic fenugreek gum: their self-assembly behaviors and use as a novel thickening agent in fracturing gel.

A novel fluorinated anionic fenugreek gum (FAFG) was obtained with excellent solution, gel, and broken-gel liquid properties in tertiary oil recovery, which were studied in detail and fenugreek gum (FG) and anionic fenugreek gum (AFG) were used as contrast samples. The results show that, compared to the FG and AFG solution properties, FAFG shows self-assembly properties, and inclusion of more fluorinated groups further reduced the critical associating concentration, yielding better associating properties. Compared to the FG and AFG gels, the FAFG gels exhibit good temperature resistance, shear resistance, rheological behaviors, and excellent salt tolerance. These improvements are attributed to the introduction of fluorinated groups and sulfonic groups. Compared to the FG and AFG broken-gel solutions, the FAFG broken-gel solutions presented slightly higher apparent viscosities. Moreover, the FAFG broken-gel solutions had profoundly lower surface tension and interfacial tension and extremely lower formation damage rates. They can hence serve as clean-up additives themselves after gel breaking. This automatically improves the flowback efficiency and reduces the formation damage. The residue rates of the FAFG broken-gel liquids were lower than those of the AFG and FG broken-gel liquids. Combined with its other excellent properties, FAFG would be an ideal component in fracturing gel.