Structural Viscosity Index Research Articles

Influence of Complex Plasticizer on Plasticizing Effects and Rheological Properties of Plasticized Poly(Vinyl Alcohol)

AbstractPoly(vinyl alcohol) (PVA) was modified using D‐mannitol (DM) and 1‐butyl‐3‐methylimidazole bromide (BMIMBr) as the complex plasticizer (DB), and PVA/DB composite was prepared. The plasticizing effect of DB on PVA was studied by Fourier transform infrared spectroscopy (FT‐IR), differntial scanning calorimetry (DSC), thermos gravimetric analysis (TGA) and melt flow indexer (MI). FT‐IR analysis indicated that Br− of BMIMBr and OH of DM could form H‐bonds with OH of PVA. With the increase of DB, the melt temperature (Tm2) and crystallization temperature (Tc1) of PVA/DB composite decreased, the initial thermal decomposition temperatures (Td), thermal processing window (ΔT) and MI values increased respectively. Based on above studies, the influence of DB content on rheological properties of PVA/DB composite was investigated by the capillary rheometer. The result displayed that apparent viscosity of PVA/DB composite decreased with increasing DB content, shear rate and measured temperature. The non‐Newtonian index (n) increased and structural viscosity index (Δη) decreased with the increase of measured temperature and DB. The viscous flow activation energy (Eη) decreased as the shear rate and DB content increased. When the measured temperature, DB content and shear rate were in the range of Tm2+30 −Tm2+35 °C, 40–50 wt% and 764.8–1504.9 s−1, respectively, the spinnability of PVA/DB composite was optimal, which will lay a theoretical foundation for the exploration of melt spinning process in the future.

Effect of Ultrasound and Salt on Structural and Physical Properties of Sodium Alginate/Soy Protein Isolates Composite Fiber.

Recently, there has been a growing interest in advancing plant-based or cultured meat substitutes as environmentally and ethically superior alternatives to traditional animal-derived meat. In pursuit of simulating the authentic meat structure, a composite fiber composed primarily of soy protein isolates (SPIs) was fashioned, employing a fiber-based plant-based analog meat construct. To refine the spinning process and enhance fiber quality, we employed ultrasound treatment, a physical modification technique, to scrutinize its influence on SPI protein structure. This inquiry extended to the examination of the interplay between sodium alginate (SA) and SPI, as well as the impact of salt ions on the SA and ultrasound soy protein isolates (USPI) interaction. A comprehensive exploration encompassing ultrasound treatments and salt concentrations within the composite solution, along with their repercussions on composite fiber characterization, with a rise in negative zeta potential value, states the ultrasound treatment fosters protein aggregation. Moreover, the introduction of salt augments protein aggregation as salt content escalates, ultimately resulting in a reduced structural viscosity index and improved spinnability. The presence of Ca2+ ions during the coagulation process leads to interactions with SA. The involvement of ultrasound prompts the exposure of hydrophilic amino acid segments in the protein to water, leading to the development of a more porous structure. Solely under the influence of ultrasound, the fiber exhibits 5% higher water-holding capacity and superior mechanical properties while maintaining comparable thermal stability.

Rheological behavior of PES/PVP/DMAc solution and PVP structural regulation for hollow fiber membrane

AbstractRheological study plays a significant role in hollow fiber membrane spinning process and membrane structure regulation. In this work, the rheological behaviors of polyethersulfone (PES) spinning solutions added the polyvinylpyrrolidone (grade of PVP‐K30, PVP‐K60, and PVP‐K90) were systematically investigated by rotational rheometry to understand how the PES membrane structure changes. Results show that PVP of variable molecular weights change the rheological properties of PES spinning solution, such as the viscosity (ηa), non‐Newtonian index (n), flow activation energy (Eη), structural viscosity index (∆η), storage modulus (G′), and loss modulus (G′′). The mixture with PVP‐K30 exhibits optimal spinnability but the finger‐like membrane structure is undesirable for the hemodialysis. The rheological behaviors of PES/PVP‐K60 and PES/PVP‐K90 reveal that increasing shear rate and temperature are effective ways to improve the spinnability of the mixture and the membrane structure is regulated. Meanwhile, the addition of PVP‐K60 or PVP‐K90 at their critical concentration to the PES solution can fabricate a hollow membrane with a sponge‐like structure. Combining spinnability and membrane structure, PVP‐K90 is a suitable additive for the hemodialysis membrane.

Characteristics of Sodium Alginate/Antarctic Krill Protein Composite Fiber Based on Cellulose Nanocrystals Modification: Rheology, Hydrogen Bond, Crystallization, Strength, and Water-Resistance.

The purpose of adding cellulose nanocrystals (CNCs) into sodium alginate (SA) and Antarctic krill protein (AKP) system is to use the ionic cross-linking of SA and AKP and the dynamic hydrogen-bonding between them and CNCs to construct multiple cross-linking structures, to improve the water-resistance and strength of SA/AKP/CNCs composite fiber. Based on the structural viscosity index in rheological theory, the ratio of spinning solution and temperature were optimized by studying the structural viscosity index of the solution under different CNCs content and temperature, then the composite fiber was prepared by wet spinning. We found that when the content of CNCs is 0.8% and 1.2%, the temperature is 45 °C and 55 °C, the structural viscosity is relatively low. Under the optimal conditions, the intermolecular hydrogen bonds decrease with the increase of temperature. Some of the reduced hydrogen bonds convert into intramolecular hydrogen bonds. Some of them exist as free hydroxyl; increasing CNCs content increases intermolecular hydrogen bonds. With the increase of temperature, the crystallinity of composite fiber increases. The maximum crystallinity reaches 27%; the CNCs content increases from 0.8% to 1.2%, the breaking strength of composite fiber increases by 31%. The water resistance of composite fiber improves obviously, while the swelling rate is only 14%.

The effect of liquid crystalline graphene oxide compared with non-liquid crystalline graphene oxide on the rheological properties of polyacrylonitrile solution

Abstract In this article, polyacrylonitrile (PAN) and two kinds of graphene oxide (GO) with different structural properties are blended in dimethyl sulfoxide (DMSO) according to a certain ratio to prepare stable-spinning solution. One kind of GO is purchased, and we call it GO1. The other is a kind of self-made GO with liquid crystal property in solution, which is called GO2. The effects of two kinds of GO on the rheological properties of PAN/GO spinning solution (15 wt%) were studied. The results show that the viscous activation energy of the liquid crystal GO2/PAN blend solution is significantly higher than that of the nonliquid crystal GO1/PAN blend solution. Moreover, the liquid crystal system is more obviously affected by temperature. The structural viscosity index of the liquid crystalline GO2/PAN solution is obviously lower than that of the GO1/PAN solution. It indicates that the existence of liquid crystallinity is beneficial to the spinning of the solution. In the low-frequency region, the addition of GO1 makes the solution more elastic, and the addition of GO2 makes the solution more viscous.

Influence of surfactants on rheological behaviors of polyacrylonitrile/dimethyl sulfoxide/silicon blending polymer solutions

AbstractKH550, KH560, CTAB, and F127 were adopted to modify silicon (Si) to improve the dispersity and stability of Si in the polyacrylonitrile/dimethyl sulfoxide (PAN/DMSO) polymer solutions. The influence of surfactants on rheological behaviors of PAN/DMSO/Si blending polymer solutions was investigated by an advanced solution and melt rotation rheometer. The homogeneity and stability were also studied. The results showed that the surfactants could change the viscosity dependence of blending polymer solutions on shear rate, temperature and storage time by increase the steric hindrance of Si. Among the four solutions, PAN/DMSO/Si blending polymer solution with F127 exhibited the lowest viscosity, activation energy and the smallest structural viscosity index and exhibited the trend close to the Newtonian fluids. Moreover, PAN/DMSO/Si blending polymer solution with F127 exhibited the best dispersity and stability, indicating its best physical properties and machinability.

Study of structural and mechanical properties of bases in the development of dental gel with combined composition

Aim. The development of the composition of the dental gel for the treatment of infectious and inflammatory diseases of the oral cavity, taking into account the physicochemical properties of the active pharmaceutical ingredients, namely the justification of the type and concentration of the gelling agent and other excipients.Methods. The determination of organoleptic characteristics, uniformity of gel samples, pH of aqueous extract, and structural viscosity index was carried out according to the methods of the State Pharmacopoeia of Ukraine. Rheological studies were carried out using a rotational viscometer of the rotating type BROOKFIELD DV-II + PRO (USA) with a coaxial cylinder system.Results. In order to choose the optimal composition of the gel base, experimental samples with various gelling agents were developed (Carbopol 974P, Carbopol 934P, Carbopol Ultrez 10, xanthan gum, sodium alginate, sodium carmellose) and their organoleptic characteristics, structural viscosity and colloidal stability were studied. The physicochemical and rheological studies that were carried out, allowed us to conclude that it is rational to use the Carbopol Ultrez 10 gel former at a concentration of 1.1 %. When choosing neutralizing agents, sodium hydroxide and trometamol were used in the studies. According to the results of studies, sodium hydroxide at a concentration of 0.32 % was selected as a neutralizer, which provides maximum, stable viscosity in the pH range from 5.0 to 7.0.Concusions. The composition of the basis of a dental gel for the treatment of infectious and inflammatory diseases of the oral cavity has been developed: Carbopol Ultrez 10 - 1.1 %, sodium hydroxide solution 10 %–0.32 %

The cyclization index and toughness of gel spun polyacrylonitrile (PAN) proportionality with its heat of stabilization

The spun tapes of synthesized PAN, its copolymer with 1 wt% itaconic acid, and doped version with 1 wt% sodium dodecyl sulfate (SDS) all showed stripy, even, and compact cross-sections as the hallmark of gel forming products. PAN doping with SDS and acrylonitrile copolymerization with itaconic acid reduced its dimethylformamide (DMF) solution structural viscosity index (Δη) by 50% and 30%, respectively, at 675 s− 1. In addition, the modification of synthesized PAN through doping and acrylonitrile copolymerization with itaconic acid led to severe and mild gelation temperature decrease, respectively. The stabilization peak of the synthesized PAN tape was enhanced as much as 25 °C by 900% hot drawing, decreased by about 10 °C through copolymerization, while experienced small temperature changes through doping. The second derivative of Fourier transform infrared and Gaussian fitting was used to analyze the tapes cyclization due to stabilization treatment through introducing Isd index. 10 min Isd index was raised as much as 430% and 800% in comparison with the synthesized PAN through its doping or acrylonitrile copolymerization with itaconic acid, respectively. Further 180 min of Isd index, however, showed the same proportional increase as toughness of the drawn tapes versus their heat of stabilization through their physical and chemical modifications.

Rheological Behaviors of Graphene Oxide/Polyacrylonitrile Spinning Solutions

The rheological behaviors of polyacrylonitrile (PAN) in NaSCN aqueous solutions containing different amount of Graphene oxide (GO) were investigated through both steady-state and dynamic rheological measurements. The parameters such as apparent viscosity (ηα), flow activation energy (Eη), structural viscosity index (Δη), storage modulus (G’), loss modulus (G’’) and mechanical loss factor (tanδ) were measured to illustrate the rheological behaviors of these solutions. The results showed that the apparent viscosity decreased with adding appropriate amount of GO, while the structural viscosity index, the flow activation energy and the mechanical loss factor of GO/PAN spinning solutions increased. Accordingly, a possible mechanism of GO effect on rheological behaviors of PAN solution was proposed in this work.

The rheological properties of bamboo cellulose pulp/ionic liquid system

In this study, two kinds of spinning solutions were prepared by dissolving bamboo cellulose pulp into 1-ethyl-3-methyl imidazole chloride salt ([EMIM] Cl) and 1-butyl-3-methyl imidazole diethyl phosphate salt ([BMIM]DEP) ionic liquids, respectively. Furthermore, the rotational rheometer was used to test the steady-state rheological properties of above as-prepared spinning solutions. The research results show that both of these two ionic liquids exhibit better solubility to the bamboo cellulose pulp. The apparent viscosities(ηa) decrease with the increased temperature(T) and shear rate(γ) and increase with the increased concentration. The non-Newtonian index(n) declined with the increase of both shear rate and concentration, as well as increased with the build-up temperature. The structural viscosity index(Δη) increased with the increased concentration and tended to decrease with temperature rise. Meanwhile, viscous flow activation energy(Eη) decreases with the increased share rate as well as the concentration. According to the results, it can be seen that the bamboo cellulose pulp/[EMIM]Cl with the concentration of 6% at 70°C exhibits better spinnability.

Efficient preparation of high concentration cellulose solution with complex DMSO/ILs solvent

The development of a low-cost and efficient solvent for cellulose has been a longstanding challenge in the field of cellulose chemistry. In this paper, we further studied a highly effective cellulose solvent composed of a large amount of dimethyl sulfoxide (DMSO) and a small amount of 1-ethyl-3-methylimidazolium acetate ([C2mim][CH3COO]). The fact that DMSO/[C2mim][CH3COO] can dissolve cellulose more efficiently than pure [C2mim][CH3COO] was fully confirmed with a combination of polarized light microscope and turbidimetric measurements. 1H-NMR spectrographs and conductivity results indicated that an increased concentration of free [CH3COO]− was the main reason for this enhanced dissolution ability. Rheology results revealed that cellulose-DMSO/ionic liquids (ILs) solution had lower zero shear viscosity, structural viscosity index, and viscous flow activation energy, which would contribute to its outstanding spinning property compared to other cellulose solutions. These advantages combined with the low cost of this proposed complex cellulose solvent make it promising to promote its industrial applications.

Effect of coupling agent on crystallization and rheological properties of poly(ethylene terephthalate) composite masterbatches

Poly(ethylene terephthalate)/carbon black/coupling agent composite masterbatches were fabricated using separate feeding technique. The effect of coupling agent on crystallization of composite masterbatches was investigated by differential scanning calorimetry, wide‐angle X‐ray diffraction, and Fourier transform‐infrared spectroscopy, respectively. The results show that the strong interfacial interaction among poly(ethylene terephthalate) (PET), coupling agent and carbon black hinders chains mobility in process of PET crystallization, which is illustrated by interfical structure model. Whereas, the crystallinity of composite masterbatch increases due to uniform dispersion of carbon black modified by coupling agent. Activation energy of viscous flow of the composite masterbatches is closer to that of virgin PET, so the spinning parameters can be controlled according to each other. Besides, structural viscosity index of composite masterbatches is greater due to strong interfacial interaction among PET, coupling agent and carbon black. Thus, in order to smooth spinning, the composite masterbatches need greater shear rate compared with PET/carbon black masterbatch. POLYM. COMPOS., 38:2358–2367, 2017. © 2015 Society of Plastics Engineers

A comparative study of rheological behavior of PET and PET/carbon black composite masterbatch

In order to explore the process of masterbatch dilution technique, the performance differences between poly(ethylene terephthalate) (PET) and PET/carbon black (CB) masterbatch were investigated. Scanning electron microscopy images of PET/CB masterbatch display a homogeneous dispersion status of CB particles in PET matrix. Besides, the improvement in heat resistance of masterbatch was confirmed by thermogravimetric analysis. The rheological measurement demonstrates that compared with PET the shear thinning effect of PET/CB masterbatch is more remarkable. The non-Newtonian index (n), activation energy of viscous flow (∆E) and structural viscosity index (∆η) can provide much important information for understanding the blending mechanism between PET and the masterbatch, which is valuable for spinning composite fiber with masterbatch dilution technique. According to the results of rheological measurement, the temperature is optimized to 280 °C and simultaneously the shear rate should be exceed to 1,150 s−1 on the basis of the theory of similarity and intermiscibility.

Surface acetylation of bamboo cellulose: Preparation and rheological properties

In this study, purified bamboo cellulose was used to synthesize cellulose diacetate (B-CDA). The synthesis was controlled by determination of the degree of substitution and insoluble residue content. The product then was characterized by FTIR. The rheological properties of B-CDA solutions in acetone/N,N-dimethylacetamide (DMAc) solvent system were systematically investigated on an advanced rheometer, including the dependence of apparent viscosity ηα, non-Newtonian index n, and structural viscosity index Δη on the concentration and temperature of the solutions. B-CDA–acetone/DMAc solution is a shear-thinning fluid. With increasing solution concentration and decreasing temperature, Δη increased, whereas n decreased, which indicates a deteriorating spinnability. Moreover, the values of the viscous flow activation energy Eη based on the Arrhenius equation increased when the shear rate γ was enhanced, which indicates that the ηα of the solution is more sensitive to temperature in the higher γ values. The results are favorable for predicting the B-CDA solution spinnability.

Study on antibacterial activity of O-carboxymethyl chitosan sodium salt and spinnability of O-carboxymethyl chitosan sodium salt/cellulose polyblends in N-methylmorpholine-N-oxide system

O-carboxymethyl chitosan sodium salt (NaCMCh), which has good antibacterial activity and solubility in N-methylmorpholine-N-oxide (NMMO) after being treated by sodium hydroxide solution, was blended with cellulose NMMO/H2O solution to study the spinnability. The effect of molecular weight on antibacterial activity and solubility was discussed. The optimal range of molecular weights is from 8×104 to 1.9×105. The rheological properties of NaCMCh/cellulose polyblends in steady-shear were investigated. The results are presented using appropriate master curves for the temperature and concentration effects. The flow behavior index of the polyblends increase with increasing temperature and NaCMCh content. Apparent viscosity and zero-shear viscosity decrease, but the critical shear rate increases due to the addition of NaCMCh. The polyblends with NaCMCh display a lower structural viscosity index. Finally, the fibers were successfully spun using the lyocell process with NMMO/H2O and the fibers with NaCMCh exhibit good mechanical properties and moisture absorption.

Rheological Behaviors of Polyacrylonitrile Melt Using Ionic Liquids as a Plasticizer

The rheological behaviors of polyacrylonitrile/ionic liquids (PAN/ILs) melt were investigated to determine the general processing parameters and offer an important theoretical foundation of plasticized melt spinning. A step was carried out to decide the accurate temperature through the temperature sweep and time sweeps. The impacts of the concentration and temperature on the modulus of PAN/ILs samples were studied by dynamic sweeps. The three-parameter Carreau viscosity model was used to predict the zero-shear viscosity from the apparent viscosity data. The PAN/ILs melt showed shear-thinning behaviors. The melt with higher PAN concentration was found to be more sensitive to the temperature. However the structural viscosity index of the melt first decreased and then increased with the increase of temperature.

Rheological Properties of Blend Spinning Solution of Sodium Alginate and TiO<sub>2</sub> Nanoparticles

Rheological properties of blend spinning solution of sodium alginate and TiO2 nanoparticles (SA/nano-TiO2) were investigated. The rheological parameters, structural viscosity index (Δη) and flow activation energy (Eη) of spinning solutions were calculated. The results reported that the blend spinning solutions were non-newtonian fluids. The apparent viscosity, consistency index (k) and Eη increased with increasing nano-TiO2 content in SA spinning solution, but the degradation degree of apparent viscosity decreased, flow behavior index (n) only slightly decreased and the Δη had no significantly change. The apparent viscosity (ηa) of spinning solutions could be regulated by changing temperature under 50oC. Blend spinning solution had good stability and practical applicability.

Preparation and rheological properties of cellulose/chitosan homogeneous solution in ionic liquid

Cellulose/chitosan homogeneous solutions were prepared in 1-ethyl-3-methylimidazolium acetate ([EMIM]Ac) ionic liquid. Steady and oscillatory dynamic rheological properties were studied with a Haake Mars-ΙΙΙ rotational rheometer. Rheological results show that cellulose/chitosan [EMIM]Ac solutions are a pseudoplastic liquid, and the viscosity of the solution decreases with increasing of chitosan content. The zero shear rate viscous activation energy of solution is about 52.10 to 62.50KJ/mol, calculated from the Cross and Arrhenius equation. The structural viscosity index of the solution is similar to that of cellulose/N-methylmorpholine-N-oxide solution, which indicates a potential spinnability. The dynamic rheological responses reveal that the Cox-Merz rule holds well with the solutions, and the crossover point of loss modulus and storage modulus shifts to a higher frequency range with increasing temperature.

Rheological Behavior of Blend Spinning Solution of Sodium Alginate and Carbon Black

Rheological properties of blend spinning solution of sodium alginate and carbon black (SA/CB) were investigated. The results reported that blend spinning solutions were non-newtonian fluids. The apparent viscosity and structural viscosity index increased with increasing CB content in SA spinning solution, but the non-newtonian index decreased, both demonstrated the blend solution was sensitive to shear rates. Blend spinning solution with 6% CB had large flow activation energy (Eη), so the temperature must be controlled exactly in spinning. Temperature had similar impact on sample spinning solutions: the apparent viscosity decreased when it increased. Study on dynamic rheological behavior shows SA/CB blend spinning solutions had greater die swell ratio and worse flowability than pure SA solution, but the flowability of blend solutions could be regulated by changing temperature.

Research on the Rheological Properties of Polyphenylene Sulfide<i> (PPS)</i> Resin

Using capillary rheometer to study PPS temperature, shear rate, activation energy of viscous flow. Experiments show that with the increase of shear rate, apparent viscosity decreased. As the apparent viscosity is affected by temperature, so when the temperature increased, the apparent viscosity also decreased. It also indicates that the higher the shear rate comes, the lower the impact of temperature on the apparent viscosity is. As the temperature increased, non-Newtonian index (n) increased and tended to 1, PPS melt is pseudoplastic fluid. The activation energy of viscous flow of PPS decreased with the increasing of the shear rate. In addition, with the increasing of temperature, structural viscosity index felt regularly.