Dynamic Rheological Parameters Research Articles

A conceptual design of two-stream alkali-activated materials

To properly control the reaction kinetics and fresh properties evolution in conventional alkali-activated materials (AAMs), a conceptual design of two-stream AAMs has been proposed in this study. This is achieved by dividing the solid and liquid components in AAMs, including blast furnace slag (BFS) and electric arc furnace slag (EFS) precursors, as well as aqueous sodium hydroxide and silicate activators into two separate streams A and B, where a very limited reactivity is expected in individual streams to ensure sufficient workability retention. Moreover, a final-stage intermixing is required to combine individual stream mixtures and trigger the major activation reaction. Fresh and hardened properties of combined mixtures were checked at different stages. The microstructure and reaction products were investigated to understand the strength development. Low dynamic rheological parameters and good workability retention have been detected in all individual stream mixtures, accompanied by limited exothermic heat flows after the initial dissolution confirmed by calorimetry tests. Further, Portland cement (PC) is partially blended into stream A to alter the early stiffening process in combined mixtures and meet various setting demands after intermixing. However, this might lead to a reduction in mechanical properties, associated with the formation of porous microstructures and an increase in the Ca/Si ratio in reaction products. Eventually, the conceptual design is validated in different scenarios including self-compacting and 3D-printing concrete applications.

Impact of multi‐pin atmospheric cold plasma on dynamic rheological characteristics of kodo millet starch

AbstractKodo millet's popularity grows due to its diverse applications and health benefits, primarily as a starch source for industries like food processing, requiring modifications to overcome raw starch limitations. In this study, raw kodo starch underwent treatment with cold plasma, varying in voltage (10, 20, and 30 kV) and duration (10, 20, and 30 min). The treated samples were designated as S1 to S9. The results showed that the modified starch exhibited significantly higher G' and G" values compared to the control sample. Three different models were attempted to describe the flow behavior, with the most suitable model selected. This analysis led to an increase in yield stress from 86.55 to 217.98 Pa and an increase in the flow index from 0.31 to 0.56 for the modified starch. This understanding of the rheological characteristics of modified starch can be invaluable for innovating new products, blending novel ingredients, and optimizing manufacturing processes.Practical applicationsKodo millet has gained significant popularity in recent times owing to its high fiber content and low glycemic index. In this research, starch extracted from kodo millet underwent plasma treatment, resulting in a modified starch with enhanced functional properties. The study focused on exploring the rheological properties of this treated starch, and the findings revealed notable improvements in dynamic rheological parameters, including the storage modulus, loss modulus, and viscosity of the starch, all of which increased due to the plasma treatment. The enhanced viscosity makes kodo millet starch particularly suitable for a wide range of food applications. This modified starch finds practical use in the preparation of porridges, soups, and as a reliable filling agent in various food products. This emerging technology has captured the attention of food manufacturers in the grain processing sector, offering a means to elevate the quality and desirability of new food products.

Rheology of ultrafine tailings cemented paste backfill: The effect of the aqueous solution pH and superplasticiser dosage

pH is an important factor affecting the rheology of fresh ultrafine tailings cemented paste backfill (UTCPB). In this study, the effect of solution pH on the packing density of fresh UTCPB containing polycarboxylate superplasticizer (PCE) was investigated experimentally. The effect of PCE dosage on the dynamic rheology and thixotropy of the UTCPB at both pH 2 and 7 of the aqueous solution was investigated. A relationship model between water film thickness (WFT) and dynamic rheological parameters of UTCPB was constructed. In addition, the improved model for predicting rheological parameters considering flocs was developed. The results show that the packing density and WFT of the ultrafine tailings cemented paste are significantly influenced by the pH of the mixture and the PCE dosage. The packing density and WFT at pH 2 were greater than those at pH 7. For aqueous solution pH 2, the critical micelle concentration (CMC) was approximately 0.05% and the thixotropic index decreased with increasing PCE dosage. For aqueous solution pH 7, the CMC is between approximately 0 and 0.05%. The relationship between WFT and the rheological parameters of UTCPB is exponential. The proposed rheological parameter prediction model has high accuracy and applicability. The results of this study could provide guidance for the design and application of UTCPB in mines.

Fabrication of double nano-emulsions loaded with hyssop (Hyssopus officinalis L.) extract stabilized with soy protein isolate alone and combined with chia seed gum in controlling the oxidative stability of canola oil

The aim of this study was to encapsulate hyssop (Hyssopus officinalis L.) extract obtained through ultrasound-assisted cold plasma pretreatment extraction within a double emulsion stabilized by soy protein isolate alone (SPI) and combined with chia seed gum (CSG) in the external aqueous phase on the stabilization of canola oil. FTIR analysis verified that there were electrostatic interactions between CSG and SPI. The SPI/CSG-stabilized emulsion demonstrated lower viscosity, smaller droplets, higher ζ-potential, and encapsulation efficiency compared to the SPI-stabilized emulsion. Non-Newtonian, pseudoplastic behaviors were shown by emulsions. Also, according to the dynamic rheological parameters (G' and G''), the SPI/CSG-stabilized emulsion had elastic behavior with weak gel properties. The antioxidant activity of the encapsulated extract at 1500 ppm during the storage in canola oil was investigated and compared to unencapsulated extract and TBHQ. The results showed that oil containing encapsulated extract had lower oxidative alterations than the unencapsulated form.

Rheological and textural properties of heat-induced gels from pulse protein isolates: Lentil, mungbean and yellow pea

The molecular structure and conformation of the plant-based proteins dominate their gelation behaviour. These aspects have been mostly overlooked for underutilised pulse proteins such as lentils and mungbean that differ structurally with soy and pea proteins. Rheological and textural properties of heat-induced gels of lentils (LPIs) (green, red and black lentils), mungbean (MBPI) and yellow pea (YPPI) were compared with commercial soy (CSPI) and pea (CPPI) protein isolates. On investigation of the dynamic rheological parameters, the critical protein concentration (CPC) of MBPI was the lowest (14% w/v) followed by LPIs (18% w/v) and YPPI (22% w/v). Also, vicilin-rich MBPI showed a lower gelation temperature (Tgel 77 °C) and developed stronger gels compared to LPIs and YPPI. On the other hand, commercial isolates with larger particle size, water holding capacity and denatured state showed lower CPC (CPPI, 14% w/v) than their folded and more soluble counterparts (YPPI 22% w/v). Hence, the study of thermo-rheological properties of pulse proteins with distinct molecular and conformation characteristics has yielded a structure-gelation paradigm. These findings support the development of plant protein-gelled products not limited to meat and dairy analogues.

The Effects of Surfactant and Metal Ions on the Stability and Rheological Properties of Nanoemulsions Loaded with Gardenia Yellow Pigment

The present work reports the preparation of gardenia yellow pigment containing paraffin oil nanoemulsions stabilized by Span80 and Tween80. The preparation of the required nanoemulsions was optimized by testing different conditions, such as varying the hydrophilic–lipophilic balance (HLB), the emulsifier concentration (EC), the oil–water ratio (OWR), and the temperature (T), as determined by the average droplet diameter (ADD) and polydispersity index (PDI). Our results indicated that a minimum ADD of 65.9 nm and PDI of 0.116 were obtained at an optimum HLB value of 6.0, EC of 10% (w/w), OWR of 2:1, and T of 40 °C. Both the steady-state and dynamic rheological parameters were further investigated, revealing that the emulsions exhibited pseudoplastic behaviors. The long-term stabilities of the nanoemulsions after the addition of inorganic salts were monitored by observing their visual appearances. It was found that the emulsions containing pure water or 0.1 M CaCl2 and AlCl3 became slightly separated, while the emulsions containing 0.1 M KCl and NaCl showed no separation after 30 days of storage at room T. This difference among different salts could be related to the number of valence electrons of their cations. The spatial electrostatic effects of the monovalent cationic (KCl and NaCl) and the nonionic surfactants were greater than the delamination/sedimentation forces of the system, which was better than the salt based on the cations with valences greater than one (CaCl2 and AlCl3). In conclusion, the present work illustrated the formation, rheological properties, and stability of water containing gardenia yellow pigment in paraffin oil nanoemulsions, which can be of great significance for the application of gardenia-yellow-pigment-based formulations.

Addition of Amaranth Flour of Different Particle Sizes at Established Doses in Wheat Flour to Achieve a Nutritional Improved Wheat Bread.

Amaranth is an underutilized pseudocereal that can be used to supplement wheat flour (WF) in order to improve the nutritional quality of bread. Bread digestibility is impacted by particle size which produces different nutritional properties. This research aims to evaluate the baking characteristics of optimal wheat−amaranth composite flour for each studied amaranth flour (AF) particle size at doses previously established based on an optimization process and to characterize from a physical, textural, nutritional, and sensorial point of view the obtained bread. The results revealed that the optimal wheat−amaranth composite flour with medium and small particle size, respectively showed a slightly lower α-amylase activity, while dough development time was significantly higher compared to the WF. A significant (p < 0.05) decrease was observed in the elasticity, deformation energy, and dynamic rheological parameters of the optimal composite dough for all the particle sizes, whereas fermentation parameters showed higher values compared to the control, indicating the ability of the gluten structure in large, medium, and small particle sizes of AF to hold the gas and to expand without collapsing. The physical, textural, and especially nutritional characteristics of the optimal WF-AF bread were enhanced. The sensory evaluation results revealed high scores (8.70) for the acceptability of optimal bread with a medium particle size as compared to wheat bread (8.25). The protein and ash content of the optimal breads with large, medium, and small AF particle sizes, respectively, increased significantly, from 8.92 to 10.58%, and 0.82 to 0.99%, respectively, relative to the wheat flour bread (8.35% and 0.72%, respectively). The mineral content was up to two times higher in the optimal breads compared to wheat flour bread. The findings generated from this study are helpful in bakery industry for designing products with enhanced nutritional properties and for introducing new products to the market.

Effect of annealing and α-amylase extract on the rheological properties, syneresis, and water holding capacity of different starches

The objective of this study was to determine the impact of annealing and enzyme extract on the gel properties of chickpea (C.P), corn (C.S), Turkish bean (T.B), sweet potato (S.P.S), and wheat starches (W.S). Starches were annealed at different temperatures and times in excess water with or without germinated sorghum extract (GSE). The concentration of α-amylase in the GSE was 5 mg/10 mL. Dynamic rheological properties, freeze-thaw stability and water holding capacity (WHC) were investigated. The dynamic rheological parameters of the native or GSE-treated starches varied significantly (p < 0.05), while the G` of some starches were frequency-independent others exhibited sharp increase in G` at low frequencies. Unlike T.B and S.P.S, the G` of the native C.P and C.S starches was significantly (p < 0.05) reduced by annealing, whereas GSE-treatment reduced G` of all gels regardless of annealing temperature or time. Starch gels demonstrated significant (p<0.05) reduction in freeze thaw stability and increase in water holding capacity after annealing and GSE treatment.

Rheological behaviour of low-heat Portland cement paste with MgO-based expansive agent and shrinkage reducing admixture

The combined use of low heat Portland cement (LHC), MgO-based expansive agent (MEA) and shrinkage reducing admixture (SRA) is beneficial to reduce the cracking risk of concrete. In this study, the effects of MEA and SRA on the rheological behaviour of LHC paste were investigated using dynamic and static shearing tests. The response surface methodology was used to estimate the effects of MEA, SRA, and superplasticizer on dynamic rheological parameters, while the zeta potential, calorimetric, and solid phases tests were conducted to explore the mechanisms of time-dependent rheological behaviour. Results indicate that MEA contributes to higher dynamic yield stress and plastic viscosity, while the effect of SRA is dependent on its dosage. MEA promotes the static yield stress development for accelerating the hydration of blends and the formation of Mg(OH)2. SRA retards the hydration of LHC and blended paste and reduces the number of main hydration products. However, the static yield stress is further increased by SRA, showing a consistent changing trend with the surface area of hydrated particles.

Effects of cold atmospheric-pressure plasma on the rheological properties of gum Arabic

The main focus of current research was on the effect of cold atmospheric-pressure plasma (CAP) on the rheological properties of gum Arabic (GA). GA powder was treated by dielectric barrier discharge (DBD) plasma with ambient air at different times (20, 40, and 60 min). The rheological properties of both natural and treated-gum dispersions were specified. The results showed the CAP treatment time had a notable and non-linear effect on the rheological parameters of the treated gums. Compared with control, all treated-gum dispersions showed higher apparent viscosity within the applied shear rate range (0.01–400 s−1). The highest viscosity (50 s−1) belonged to the dispersion of the gum treated for 20 min. CAP treatment significantly (p < 0.05) increased the shear-thinning behavior of the treated-gum dispersions. Power-law was the best model for describing the flow behavior of natural GA and treated-gum dispersions. The obtained dynamic rheological parameters (G′ and tan δ) revealed that CAP treatment reinforced the elastic properties of treated-gum dispersions, and the shortest treatment time, 20 min, was more effective in this case. Overall, it was found that the CAP-treated gums by strengthening the elastic features of dispersions could be obtained for new applications in the production of foodstuffs especially beverages.

Rheological properties of thickened barium liquids prepared with xanthan gum‐based thickener and barium powder used in the diagnosis of dysphagia: Effect of thickener concentration and serving temperature

In this study, thickened barium liquids (TBL) were prepared by mixing a xanthan gum (XG)-based thickener at different concentrations (1.0%–3.0%) with a barium powder. The rheological properties of TBL and thickened non-barium liquids (TNL) at different thickener concentrations were examined under steady and dynamic shear conditions. The values of flow and dynamic rheological parameters (K, σoc, G′, and G″) of TBL were considerably higher than those of TNL. The extents of the TBL thixotropy loops decreased with an increase in thickener concentration, showing that at higher concentrations, the degree of shearing-induced structure breakdown was lower than at lower concentrations. Compared with those of TNL, the rheological characteristics of TBL were more strongly dependent on thickener concentration, indicative of a strong molecular interaction between XG and barium at high thickener concentrations. These results could facilitate the development and preparation of videofluoroscopic contrast media with rheological properties suitable for the diagnosis of dysphagia. Practical applications Thickened liquids (TL) prepared with XG-based food thickeners are widely used for the effective management of patients with dysphagia (difficulty of swallowing). In terms of clinical practice, the rheological characteristics of thickened barium liquids (TBL) prepared with both XG-based thickener and barium powder are very important for the preparing the contrast media used for videofluoroscopic swallow study (VFSS) which the swallowing safety and efficiency with a bolus are assessed. Our results showed that compared with those of TL without barium, the rheological characteristics of TBL were more strongly dependent on thickener concentration, indicative of a strong molecular interaction between XG and barium at high thickener concentrations. These results presented in this study will be useful for the development and preparation of videofluoroscopic contrast media with rheological properties suitable for the diagnosis of dysphagia.

Investigation on the creep behavior of PA6 film based on the fractional differential model

A fractional Burgers model was proposed to investigate the creep behavior of Polyamide 6 (PA6) film. The creep tests at various conditions were conducted on dynamic mechanical analysis (DMA) tester, and the strain-time ( ∊- t) curves of deformation were analyzed by the derived model. The results indicated that the fractional Burgers model had a better performance than the classical integer-order model in simulating the deformation of PA6 film. Parameters analysis showed that the stress facilitated the transformation from viscoelastic deformation to the viscoplastic one under ambient condition. Whereas, at the state of higher temperature, the deformation could be directly activated as the viscoplastic deformation. The softening effect of PA6 film was found to be related to the expansion of viscoplastic units during stretching. Also, the fluidity of the viscoelastic units was greater than that of the viscoplastic units. Through the analysis of dynamic rheological parameters, we speculated that the variation of loss factor may come from the evolution of viscoelastic units.

Rheology and in vitro release properties of thermosensitive in situ gel of Yihuang Decoction and its common gel for vaginal use

To evaluate the traits and rheological properties of thermosensitive in situ gel of Yihuang Decoction and its common gel for vaginal use, and predict the release behavior of Yihuang Decoction in situ gel in vitro. Poloxamer was used as thermosensitive material to prepare Yihuang Decoction vaginal in situ gel, and Yihuang Decoction common gel was prepared with carbopol. Then the differences of the two gels before and after diluting with vaginal fluid were compared. The rheological parameters of Yihuang Decoction in situ gel and its common gel were determined with Anton Paar MCR102 rheometer. In addition, berberine hydrochloride was selected as an index component to evaluate the in vitro release properties of Yihuang Decoction vaginal thermosensitive in situ gel. Yihuang Decoction vaginal thermosensitive in situ gel was Newtonian fluid under low-temperature conditions, which was yellow and transparent. After reaching the gelling temperature of 24.5 ℃, it became semi-solid, pseudoplastic fluid. The gelling temperature was predicted to be 37 ℃, and the phase transition time was 30 s after diluting with simulated vaginal fluid. However, the rheological properties of Yihuang Decoction common gel had no significant changes with temperature. Compared with in situ gel, the color of common gel was darker and more translucent. Besides, its mobility was stronger after diluting with simulated vaginal fluid. The in vitro release study showed that the kinetic behavior of berberine hydrochloride in Yihuang Decoction vaginal thermosensitive in situ gel was matched with the Higuchi equation. Through simulation of vaginal administration, physical properties and dynamic rheological parameters were used to intuitively and scientifically evaluate the two gels. Compared with the common gel, the thermosensitive in situ gel could quickly attached to the vaginal mucosa and release drug, and thus was more suitable for developing vaginal administration of Yihuang Decoction, which also provides references for studying new vaginal preparation of Yihuang Decoction.

Controlling the rheological properties of wheat starch gels using Lepidium perfoliatum seed gum in steady and dynamic shear

In the present work, the influence of Lepidium perfoliatum seed gum (LPSG) addition in varied concentrations (0%, 0.25%, 0.5%, 0.75% and 1%, w/w) on dynamic and steady shear rheological properties of wheat starch dispersion (4%, /w) was examined. Comparison of the values of dynamic (G′, G″, τy, τf, tan δ), shear-dependent (ηa,50, η0, η∞, τ, m) and time-dependent (ηa,3s, k, η0, η∞) rheological parameters of the WS-LPSG mixtures with WS alone, indicated that the viscoelastic and flow properties of the mixtures were greatly affected by the addition of LPSG. According to the standard method provided by the National Dysphagia Diet (NDD), the WS and WS-LPSG gels were placed in the category of nectar-like (WS), honey-like (WS-0.25%LPSG, WS-0.5%LPSG and WS-0.75%LPSG) and spoon-thick (WS-1%LPSG) viscosity. In the simulated oral condition (SOC), the presence of saliva caused the increase of k value (10–81%), whilst decreased the values of η0 (43–95%) and η∞ (68–96%). As the concentration of LPSG increased, less decrease in value of ηa,3s in the SOC was observed. The results of present study demonstrated the feasibility of manipulating the viscosity of the WS gels by addition of LPSG to be suitable for the individuals with varying degrees of swallowing difficulty.

Evaluation of Rheological Properties of Cohesive Ophthalmic Viscosurgical Devices Composed of Sodium Hyaluronate with High Molecular Weight-2019

Ophthalmic viscosurgical devices (OVDs), mainly containing sodium hyaluronate (HA), are used in cataract surgeries to protect the cornea endothelium. In this study, the rheological properties of 9 launched products (containing 1% HA) were evaluated. The molecular weights (MWs) of HA estimated based on intrinsic viscosity varied widely, between 1100-2500 kDa, and showed a particular value for each product. Of the 9 products, 6 are classified as cohesive OVDs and their product specifications show the same value for intrinsic viscosity (25-45 dL/g), with high MW HA (>2000 kDa); however, the MW of each HA showed a particular value (2200-2500 kDa) within the range of the product specification. As with the MW of HA, apparent viscosity and dynamic rheological parameters showed particular values for each OVD. The product Opegan-Hi exhibited the highest value of apparent viscosity at low shear rate, and a solid-like behavior among the OVDs. In a questionnaire survey among 198 cataract surgeons, 42% of surgeons had experienced a difference in ability to maintain the depth of anterior chamber during surgery among the different cohesive OVDs used. This suggested that surgeons select OVD properties based on surgical procedure and patient cases. In conclusion, we demonstrated that each OVD has particular rheological properties within the range of the product specification defined by the intrinsic viscosity. The results might provide useful information for surgeons in their selection of OVDs based on their experience.

Rheological and Adhesive Properties to Identify Cohesive and Dispersive Ophthalmic Viscosurgical Devices.

The purpose of this study is to evaluate the usefulness of the rheological properties and adhesive force of ophthalmic viscosurgical devices (OVDs) as parameters for understanding and identifying the surgical behavior of cohesive and dispersive OVDs. The apparent viscosity, and the storage and loss moduli (dynamic rheological parameters) of 50% chondroitin sulfate (CS), 3% sodium hyaluronate (HA), Shellgan (the combination of 3% HA and 4% CS), Opegan (1% HA with a low molecular mass) and Opegan-Hi (1% HA with a high molecular mass) were obtained with a rheometer. The adhesive force of each sample was measured by using a texture analyzer. Opegan-Hi showed a solid-like behavior, while 50% CS showed a fluid-like behavior from their apparent viscosity and dynamic rheological parameters. Shellgan, 3% HA, and Opegan exhibited similar rheological properties and intermediate characteristics between Opegan-Hi and 50% CS, although their respective values were slightly different. Among these OVD samples, the adhesive force was higher in the order of 50% CS > Shellgan, 3% HA > Opegan > Opegan-Hi. The adhesive force of dispersive OVDs tended to be higher than that of cohesive OVDs, which correlated well with the removal times of OVDs from the eye that have previously been reported. In conclusion, we demonstrated that cohesive OVDs and dispersive OVDs have particular rheological and adhesive properties that can be applied to identify both types. These parameters obtained in this study provide useful information for a greater understanding and prediction of the behavior of OVDs in the eye during surgery.

The effects of different gums and their interactions on the rheological properties of instant camel yogurt: a mixture design approach

In this study, the dynamic rheological properties of the instant camel yogurt samples containing carboxyl methyl cellulose (CMC), konjac gum (KG) and sage seed gum (SSG) and their combinations were investigated in a model system, and mixture design was utilized to observe the effects of these gums and their interactions. Storage modulus (G′) was greater than the loss modulus (G″) at all samples and the yield stress of the samples varied between 0.0285 Pa and 0.185 Pa. Within the linear viscoelastic region (LVR), the loss tangent values of the samples were not significantly different, indicating that the nature and type of the interaction forces were similar. Frequency sweep results showed that samples had a typical weak gel-like structure behavior at any given frequency and complex viscosity (η*) had a linear correlation with frequency. All the linear terms in the predicted models for the n′, n″ and n* parameters were insignificant (P < 0.01) and it was observed that each gum had an identical effect on these parameters. SSG was the most effective hydrocolloid on all dynamic rheological parameters of the instant camel yogurts. Based on the optimization criteria, the most excellent combination was 35% CMC, 10% KG and 55% SSG at the concentration of 1%.

Effects of Electronic Waste Powder on Asphalt Binder Properties

Asphalt binders for various types of pavement construction that were modified with various contents of electronic waste powder (EWP) were characterized. The effects of EWP content on asphalt physical properties, storage stability at high temperatures, dynamic rheological parameters, and low-temperature cracking resistance were studied. Chemical properties of modified mixtures were studied using IR spectroscopy. Experimental results showed that EWP did not react chemically with the asphalt binder Studies of the physical properties of mixtures showed that EWP additives could increase significantly the high-temperature asphalt performance. Studies of storage stability showed that modified mixtures were highly stable with EWP contents <20%. If the EWP content was increased, the complex shear modulus of modified asphalt increased whereas the phase angle decreased significantly. On the other hand, bending beam rheometer (BBR) tests showed that EWP additives did not improve the low-temperature performance of asphalt binder.

Cellulose nanocrystals from Miscanthus fibers: insights into rheological, physico-chemical properties and polymer reinforcing ability

Cellulose nanocrystals (CNC) were extracted from Miscanthus (MST) fibers using a sulfuric acid hydrolysis process. The results showed that the obtained CNC exhibit a needle-like shape with an average aspect ratio of 37. The surface charge density was measured at 1.99 sulfate groups per 100 anhydroglucose units while the zeta potential value was found to be -38 mV. The crystallinity of the extracted CNC was 76%, and the cellulose I type crystal structure was predominant. Due to its high importance for potential application of CNC in aqueous systems, the rheological behavior of CNC aqueous suspensions at various CNC concentrations was determined. The CNC suspensions showed gel-like behavior at very low CNC concentrations ranging from 0.1 wt% up to 0.6 wt%, as confirmed by the steady shear viscosity measurements and the oscillatory dynamic tests. The dynamic rheological parameters of CNC suspensions were slightly affected by the temperature profile. At high temperature up to 80 °C a stronger CNC network is formed by increasing the relative motion resistance of CNC macromolecules and the entanglement. In order to identify the reinforcing ability of the newly extracted CNC, starch-based nanocomposite films were produced with various CNC contents (1, 3, 5 and 8 wt%) and their tensile properties were investigated. It was found that the addition 8 wt% CNC within starch matrix increased the Young’s modulus by 150% and the tensile strength by 118%, resulting in mechanically strong and eco-friendly nanocomposite materials.

Rheological characterizations of concentrated binary gum mixtures with xanthan gum and galactomannans

The steady and dynamic shear rheological properties of binary gum mixtures with xanthan gum (XG) and galactomannans (guar gum (GG) and locust bean gum (LBG)) were examined in a concentrated solution (1% w/w) as a function of gum mixing ratio (100/0, 75/25, 50/50, and 0/100). All samples, except for individual GG and LBG, showed high shear-thinning behavior with yield stress. The values of flow (K, ηa,50, and σoc) and dynamic rheological parameters (G′ and G″) of XG-GG and XG-LBG mixtures were significantly higher compared to XG alone, indicating that the flow and viscoelastic properties of binary gum mixtures were greatly affected by the addition of GG and LBG. The maximum elasticity synergistic interaction for XG-galactomannans mixtures was observed at a mixing ratio of 50/50, showing a greatly positive deviation between measured and calculated values of G′. These results suggest that the synergistic effect of GG and LBG addition on rheological properties of XG appears to be due to intermolecular interaction occurred between XG and galactomannans, as confirmed by dynamic rheological properties.