Rheology Modifiers Research Articles

3D Printed Architectured silicone composites containing a UV-curable rheological modifier with tailorable structural collapse

3D printed silicones, combining the unique physiochemical performances of silicones with the attractive design freedom of additive manufacturing, have aroused intensive interest from academia and industry owing to their attractive applications. Direct writing (DW) was the most used method to enable the 3D printing of silicones, but it was limited by its conflicting rheological requirements. Herein, we present novel design of an ultraviolet (UV)-thermal dual-cure ink for UV assisted DW of silicone composites. A UV curable rheological modifier was key to the ink design, which would not only increase the ink viscosity and yield stress substantially at low contents, but also further enhance its shape-retaining capability during printing by UV-assisted curing. As a result, challenging structures with good mechanical performances and isotropy were printable. Interestingly, the degree of structural collapse for the product could be controlled by tailoring the printing parameters, which proved to be a new design dimension for property manipulation of 3D-printed cellular architectures. Rheology of the inks and boundary conditions for structural collapse were discussed in detail. This work will open new opportunities for the development of 3D-printed silicones with customized architectures and tailored performances.

Eco-Designing Cosmetic Products while Preserving the Sensorial-Application Properties: An Instrumental Approach toward Sustainable Formulations

Driven by growing environmental concerns and regulations, cosmetic companies are seeking reliable methods to promptly assess the possibility of replacing high-impact ingredients with sustainable alternatives. In this work, we exploited rheological and texture analyses to evaluate the possibility of using natural and biodegradable raw materials for reformulating three commercial oil-in-water skin care emulsions from an eco-design perspective. Synthetic texturizers, like nylon-12 and PMMA, were replaced with starch, maltodextrin, and silica, while acrylic rheological modifiers were substituted with polysaccharide associations of sclerotium gum, xanthan gum, diutan gum, and carrageenan. Plant-based emollients and a biodegradable elastomer were used as alternatives to silicone oils. The flow and viscoelastic properties of the samples were characterized using rheological tests under continuous and oscillatory flow conditions. The immersion/de-immersion texture analysis allowed us to measure the mechanical properties of firmness, adhesiveness, and stringiness. A double-blind sensory test assessed the products’ application and sensory characteristics. The results revealed that rheology and texture analysis are complementary and correlated techniques, useful for predicting cosmetics’ sensory characteristics. While perfect replication of the original formulas might not be achievable, this protocol can aid formulators in selecting new eco-friendly ingredients ensuring the products’ desired application and sensory properties without compromising consumer experience.

All‐Printed Electrically Driven Lighting via Electrochemiluminescence

AbstractElectrochemiluminescence (ECL) has attracted significant attention as a promising light‐emitting technology owing to its simple configuration and solution processability. ECL has wide applications in biological and chemical sensors, lighting, and displays. ECL lighting devices are fabricated as sandwiched structures with a transparent electrode on top, which limits their widespread adoption. Intricate structures with high precision and customizable designs can be directly fabricated using 3D printing. However, 3D printing of ECL devices is challenging because of poor printability and structural integrity of ECL luminophore inks. Here, all‐printed electrically driven lighting is demonstrated using the direct ink writing method. The ECL reactive layer and electrodes are directly printed using a side‐by‐side electrode configuration. A 3D printable ECL ink is developed by incorporating silica nanoparticles as rheological modifiers to realize well‐defined patterns with high structural integrity. Graphene is introduced on Ag multilayer electrodes to embrace both the electrical conductivity and electrochemical stability for efficient ECL operation. This all‐printing approach allows the fabrication of ECL devices with complex designs, such as combs and spirals. Moreover, it facilitates seamless printing on various substrate materials, making this technology an asset in the fields of biology, chemistry, and electronics.

Kinetic stability of Fe-based nanoparticles with rheological modification by xanthan gum: A critical stabilization concentration and the underlying mechanism

Enhanced kinetic stability of Fe-NPs in groundwater is a focus in application of Fe-NPs for groundwater remediation. The effect of surfactants (Triton X-100 and SDBS) and polymers (XG, SA, CCS, PSS and PVP) on the kinetic stability of Fe-NPs were studied with sedimentation experiments. Polymers improved stability of nFe3O4 and XG had the best effect, while surfactants had minimal effect. There was a critical concentration (CSC) for XG to stabilize nFe3O4, which was 2.0 g/L. At such a concentration nFe3O4, nFe2O3, and nCuO did not settled in 10 h, while the settlement occurred below the concentration and increased with decreasing XG concentration. At CSC XG could stabilize 20 g/L of nFe3O4 for >30 days and 8.0 g/L of nZVI for 13 days. Rheology studies indicated that the enhanced stability was due to the entanglement of XG molecules in the concentration range of 0.5–2.8 g/L and the formation of a uniform entangled network at CSC concentration was responsible for non-sedimentation of Fe-NPs. At hyper-CSC concentrations under the regime of concentrated network (>2.8 g/L), the stability of nFe3O4 and nFe2O3 decreased due to depletion interaction. The rules for XG to stabilize particles and information about the critical concentration will improve XG application in groundwater remediation using Fe-NPs.

Investigation of rheological properties and modification mechanism of SBS-modified asphalt with different warm mix additives

ABSTRACT The application of warm mix asphalt (WMA) technology in polymer-modified asphalt becomes increasingly widespread, but it lacks thorough investigation on the interaction mechanism between warm mix additives and polymers. Accordingly, two new warm mix additives, an organic viscosity-reducing modifier (A) and a surfactant-based modifier (C), were selected to prepare the warm mix SBS-modified asphalt. The basic properties, viscosity-temperature characteristics, ageing resistance and rheological properties of modified asphalt were tested. At last, the modification mechanism was elucidated through a series of microscopic tests. The results indicated that A could more effectively enhance the construction workability of SBS-modified asphalt, while C had little effect on its basic properties. Both new modifiers, especially A, reduced the high-temperature property of asphalt, with partial recovery after short-term ageing. The microstructure test results indicated that the two modifiers were physically modified with SBS-modified asphalt. Both additives improved the dispersion uniformity of SBS particles in asphalt, and the microscopic morphology parameters obtained from quantitative analysis reflect the macroscopic properties of asphalt. Moreover, the light components and rubber powder of A improved the flexibility of asphalt, and C enhanced its low-temperature performance, which demonstrated that these two modifiers were more suitable for asphalt pavements in cold regions.

A new generation of fully-printed electrochemical sensors based on biochar/ethylcellulose-modified carbon electrodes: Fabrication, characterization and practical applications

Biochar is a material prepared by biomass pyrolysis, representing a more sustainable and efficient alternative to commonly used conventional carbon materials in electroanalysis. The aim of this paper is to point out that it can also show significant potential in the mass screen-printing production of miniaturized, low-cost, disposable and sensitive electrochemical sensors. Herein, a new generation of fully screen-printed electrochemical sensors is introduced, based on biochar/ethylcellulose-modified carbon working electrodes. The optimization in the sensor fabrication, involving the variability in the concentration of a binder and rheology modifier (ethylcellulose) and its impact on biochar inks from the viewpoint of viscoelasticity, printability and thermal stability, was performed to obtain the carbon-based electrochemical sensors with favourable robustness. The viability of these electrochemical sensors was demonstrated by the development and full validation of a new and sensitive differential pulse voltammetric method for the fast and reliable determination of paracetamol in pharmaceutical formulations. Within the method development, all necessary aspects, such as a study of the effect of ethylcellulose concentration, pH study of supporting electrolyte, selection of pulse parameters and analytical performance, were investigated. The obtained results allow us to predict the production and subsequent use of new, printable, cheap and environmentally friendly sensor platforms, which will exhibit convenient analytical performance with the possibility of commercialization.

3D printing of cyanate ester resins with interpenetration networks for enhanced thermal and mechanical properties

AbstractCyanate ester (PT‐30) resin possesses exceptional thermal and mechanical properties, including high heat distortion temperature, high glass transition temperature (Tg), and outstanding mechanical characteristics. Conversely, the Tg of the homopolymer of tris(2‐hydroxyethyl)isocyanurate triacrylate (T‐acrylate) surpasses that of other acrylates. The combination of PT‐30 and T‐acrylate results in the formation of an interpenetrating polymer network (IPN) through a dual curing mechanism. Furthermore, the combination of these two polymers enables the tuning of rheology for shear thinning behavior for Ink Extrusion 3D printing technology by adjusting the amount of photoinitiator and rheological modifier. Here, 3D printable ink was formulated using PT‐30, T‐acrylate with a higher Tg, a photoinitiator, and a powdered rheological additive. The printed structures underwent a dual‐curing process involving exposure to UV light and thermal curing. Thermomechanical properties of the printed samples were characterized using dynamic mechanical analysis, thermogravimetric analysis, and tensile testing. The successful formation of an IPN structure through the polymerization of T‐acrylate and PT‐30 was observed, resulting in improved mechanical properties and an elevated Tg. The Fourier transform infrared spectroscopy analysis verified the formation of cross‐linked samples. Overall, this study demonstrates the feasibility of Ink Extrusion 3D printing, using a cyanate ester resin and tris(2‐hydroxyethyl)isocyanurate triacrylate with a dual‐curing mechanism. The enhanced mechanical properties at elevated temperatures (~80% retention of room temperature tensile strength at 200°C for sample with 70/30 wt%) and high Tg of 349 ± 3°C for printed structures shown in this study make them suitable for high‐performance structural applications in industries such as aerospace, defense, and microelectronics.

Structural and flow rheological properties of pumpkin pectic polysaccharide extracted by citric acid

The present study aimed to investigate the structural and physicochemical characteristics of acid-extracted pumpkin pectic polysaccharide (AcPP) and to evaluate their flow rheological properties. AcPP was extracted from pumpkin pulp using the citric acid extraction method. The physicochemical and structural properties were analyzed by chemical methods and instrumental analyses. The obtained results showed that AcPP consisted predominantly of GalA (85.99 %) and small amounts of Rha, Gal, and Ara, with the ratio of HG/RG-I being 81.39/16.75. In addition, AcPP had medium DE (45.34 %) and contained four macromolecular populations with different Mw of 106.03 (main), 10.15, 4.99, and 2.90 kDa. The NMR analysis further confirmed that AcPP contained a linear backbone consisting of α-1,4-linked GalA residues, some of which were partially methyl-esterified. Furthermore, AcPP was amorphous in nature and had favorable thermal stability. The effects of extrinsic factors on the flow rheological properties of AcPP were evaluated. In particular, the high concentrations of CaCl2 (8 mM) and MgCl2 (10 mM) were effective in enhancing the viscosity and non-Newtonian shear-thinning behavior of the AcPP solution. This study elucidates the unique molecular structure of AcPP and suggests the potential of AcPP as a rheology modifier in low-viscous and mineral-reinforced beverages.

Nanomaterials in 4D Printing: Expanding the Frontiers of Advanced Manufacturing.

As an innovative technology, four-dimentional (4D) printing is built upon the principles of three-dimentional (3D) printing with an additional dimension: time. While traditional 3D printing creates static objects, 4D printing generates "responsive 3D printed structures", enabling them to transform or self-assemble in response to external stimuli. Due to the dynamic nature, 4D printing has demonstrated tremendous potential in a range of industries, encompassing aerospace, healthcare, and intelligent devices. Nanotechnology has gained considerable attention owing to the exceptional properties and functions of nanomaterials. Incorporating nanomaterials into an intelligent matrix enhances the physiochemical properties of 4D printed constructs, introducing novel functions. This review provides a comprehensive overview of current applications of nanomaterials in 4D printing, exploring their synergistic potential to create dynamic and responsive structures. Nanomaterials play diverse roles as rheology modifiers, mechanical enhancers, function introducers, and more. The overarching goal of this review is to inspire researchers to delve into the vast potential of nanomaterial-enabled 4D printing, propelling advancements in this rapidly evolving field.

Porous Polymer Structures with Tunable Mechanical Properties Using a Water Emulsion Ink.

Recently, the manufacturing of porous polydimethylsiloxane (PDMS) with engineered porosity has gained considerable interest due to its tunable material properties and diverse applications. An innovative approach to control the porosity of PDMS is to use transient liquid phase water to improve its mechanical properties, which has been explored in this work. Adjusting the ratios of deionized water to the PDMS precursor during blending and subsequent curing processes allows for controlled porosity, yielding water emulsion foam with tailored properties. The PDMS-to-water weight ratios were engineered ranging from 100:0 to 10:90, with the 65:35 specimen exhibiting the best mechanical properties with a Young's Modulus of 1.17 MPa, energy absorption of 0.33 MPa, and compressive strength of 3.50 MPa. This led to a porous sample exhibiting a 31.46% increase in the modulus of elasticity over a bulk PDMS sample. Dowsil SE 1700 was then added, improving the storage capabilities of the precursor. The optimal storage temperature was probed, with -60 °C resulting in great pore stability throughout a three-week duration. The possibility of using these water emulsion foams for paste extrusion additive manufacturing (AM) was also analyzed by implementing a rheological modifier, fumed silica. Fumed silica's impact on viscosity was examined, revealing that 9 wt% of silica demonstrates optimal rheological behaviors for AM, bearing a viscosity of 10,290 Pa·s while demonstrating shear-thinning and thixotropic behavior. This study suggests that water can be used as pore-formers for PDMS in conjunction with AM to produce engineered materials and structures for aerospace, medical, and defense industries as sensors, microfluidic devices, and lightweight structures.

Limiting coarsening of a two-bubble foam with viscosity

Foams age as gas diffuses from smaller bubbles to larger ones. This results in an increase of the average bubble size, which leads to a modification of the foam rheology and overall stability. This is why understanding coarsening is crucial for the creation of aerated materials. The coarsening rate is affected by various mechanisms, which are impacted by geometry (bubble size and bubble size distribution), liquid fraction, air solubility in the liquid phase, permeability of the interfaces, mechanical properties of the liquid phase and of the interfaces. In many real systems changing a single parameter will impact several mechanisms. In this work, we use a two-bubble experiment to isolate and explore the impact of bulk and surface viscosity on the rate of bubble coarsening. The experimental set-up allows us to decouple the impact of viscous dissipation from the rate of gas diffusion. We build a model in which the gas transfer is driven by Laplace pressure differences and hindered by viscous stresses. We need to take into account gravitational stresses, and dissipation in the connections, with which our model is fully predictive of the experimental data.

Mist-control of polyalphaolefin (PAO) lubricants using long pairwise end-associative polymers

Accidental release of pressurized hydrocarbon fuels and lubricants are a major fire hazard due to the formation of small droplet mists that can readily evaporate and ignite. Mist control through increasing droplet size and suppressing droplets has been previously demonstrated with high molecular weight polymer additives, but traditional long polymer additives do not survive the pumping that would usually precede accidental release. This constraint inspired associative polymer additives that can transiently form the high molecular weights needed for mist control, while reversibly breaking during pumping. A prior study demonstrated the efficacy of such a system in fuel: long telechelic polycyclooctadiene (PCOD) with pairwise associating acid and base end-groups. Here, we address an obstacle to applying this same polymeric system in a polyalphaolefin (PAO) solvent—its poorer solvent quality for PCOD than fuel. We measured the effects of the end-associative PCOD compared to a non-associative control on the rheological properties of solutions in both PAO (a common lubricant and heat transfer fluid) and decahydronapthalene (decalin, a solvent with PCOD solubility similar to fuel) in shear and extension, and connect those rheological modifications to observed changes in PAO spray under simulated accidental release conditions. The PCOD additives demonstrated substantial mist control in PAO, both in terms of reduced spray angle and droplet suppression. Despite the worse solubility in PAO and thus smaller effective coil size, these associative PCOD additives are effective at the low concentrations (¡0.1 wt %) necessary for practical use as a safety measure.

Effect of Molecules' Physicochemical Properties on Whey Protein/Alginate Hydrogel Rheology, Microstructure and Release Profile.

The encapsulation of molecules with different physicochemical properties (theophylline, blue dextran, salicylic acid and insulin) in whey protein (WP) and alginate (ALG) microparticles (MP) for oral administration was studied. MP based on WP/ALG were prepared by a cold gelation technique and coated with WP solution after reticulation. Molecules influenced polymer solution viscosity and elasticity, resulting in differences regarding encapsulation efficiency (from 23 to 100%), MP structure and swelling (>10%) and in terms of pH tested. Molecule release was due to diffusion and/or erosion of MP and was very dependent on the substance encapsulated. All the loaded MP were successfully coated, but variation in coating thickness (from 68 to 146 µm) and function of the molecules encapsulated resulted in differences in molecule release (5 to 80% in 1 h). Gel rheology modification, due to interactions between WP, ALG, calcium and other substances, was responsible for the highlighted differences. Measuring rheologic parameters before extrusion and reticulation appeared to be one of the most important aspects to study in order to successfully develop a vector with optimal biopharmaceutical properties. Our vector seems to be more appropriate for anionic high-molecular-weight substances, leading to high viscosity and elasticity and to MP enabling gastroresistance and controlled release of molecules at intestinal pH.

Synthesized silica-coated iron oxide nanoparticles and its application as rheology modifier in water-based drilling fluid

Synthesized silica-coated iron oxide nanoparticles and its application as rheology modifier in water-based drilling fluid

Assessment of the acetylation process of wheat straw pulp as sustainable rheological modifier for non-polar fluids

The main aim of this work was to study the role of the acetylation process of wheat straw pulp on its ability to rheologically modify two of the most important non-polar engineering fluid: bitumen and oil. Pulp was produced by a pilot-scale kraft pulping process from local wheat straw. Pulp was functionalized with acetic anhydride and sulfuric acid as a catalyst by modifying (temperature, pulp/acetic anhydride mass ratio, and reaction time. Further, chemical, morphological and thermal changes induced by the acetylation process were properly assessed. Acetylated wheat straw pulp dispersions in oil showed gel-like behaviour, with a mechanical spectrum characterized by higher values of the storage modulus (G′) and a minimum in the loss modulus (G″) at intermediate frequencies. The complex modulus (G*) for bitumen dispersions formulated with acetylated samples was up to 4 times higher than neat bitumen, and the phase angle (δ) indicated an enhancement in the elastic behavior parameters. The rheological response of these systems was associated with the microstructural network formed by pulp fibers and the balance between the physical and chemical changes of wheat straw fibers. According to the experimental results obtained, it can be concluded that acetylation is a relevant chemical treatment to modulate the rheological properties of wheat straw pulp dispersions in non-polar fluids, improving the compatibility between pulp fibers and these engineering fluids. Accordingly, this study provides valuable insights into the development of sustainable multiphasic materials (bitumen binders and semi-solid lubricants) for industrial applications.

On rheological properties of disc-shaped cellulose nanocrystals

The rheological properties of a substance depend greatly on its morphology, and rod-shaped cellulose nanocrystals (RCNCs) and cellulose nanofibrils (CNFs) have been extensively studied for their rheological properties. Nevertheless, the rheological properties of disc-shaped cellulose nanocrystals (DCNCs) with crystalline allomorph II derived from mercerized cellulose remain unknown yet. This work investigated the DCNCs' rheological properties in depth using steady-shear and oscillation measurements. At the same concentration, DCNC's suspension viscosity is lower than that of RCNC; RCNC has an instinct viscosity of 258.2, while DCNC has 187.9. Comparing RCNC suspensions with cellulose nanorods, DCNC has a lower aspect ratio and exhibits a distinct steady shear behavior. Under polarized film, DCNC suspension cannot self-assemble into chiral or liquid crystal phases, and with increasing concentrations, the system transitions from an isotropic phase to a gel phase. Oscillation sweeps demonstrate that the gel transition occurs at 7 %–8 %. Based on thixotropic recovery sweep outcomes, the high-stress oscillations enhance the network structure of DCNC suspensions, which is significantly different from that of RCNC suspensions. Results demonstrate the unique properties of DCNC, highlighting its application as a rheological modifier.

Gıda atıklarının bakteriyel selüloz üretiminde kullanımı

Cellulose is defined as a polymer that exists in the cell walls of plant tissues and is widely used in many industrial fields. However, the recent threat of deforestation has led researchers to find alternative wood sources for cellulose production. For this reason, literature studies have focused on certain types of bacteria known to be capable of producing cellulose, such as Acetobacter, Gluconobacter, Alcaligenes, etc. It is stated that cellulose of plant origin and bacterial origin have a similar structure. Bacterial cellulose possesses a big economic and commercial potential depending on the purpose and the production method and is generally used in food applications as a fat substitute, rheology modifier, immobilization material for probiotics and enzymes, stabilizer of pickering emulsions, component of food coatings and green packaging film. Recently, it has become more prominent to use food waste as production inputs, such as beet and sugar cane molasses, fruit waste, dairy industry waste, etc. So, the utilization of industrial by-products, agro-forestry, and food industry residues as carbon sources has been providing significant advantages, such as increasing yield and reducing cost. The objective of this study was to present a general look related to bacterial cellulose production in combination with the use of food waste and future trends.

Preparation of Cationic Polyacrylamide Suspension and Its Application in Oilfield Wastewater Treatment.

Cationic polyacrylamide (CPAM) solid particle is one of the most commonly used organic polymer flocculants in oilfield wastewater treatment, but it poses some problems, such as a slow dissolution rate and an easy formation into a "fish-eye" in the process of diluting into aqueous solution. However, the current liquid CPAM products also have some problems, such as low effective content, poor storage stability, degradation in a short time, and high preparation costs. In this paper, a CPAM suspension was successfully prepared with 50.00% CPAM fine powder, 46.87% oil phase solvent, 0.63% separating agent, 1.56% emulsifying and dispersing agent, and 0.94% rheology modifier. This suspension has an effective content of 50.00%. It also showed no separation in 7 days of storage at room temperature, no separation in 30 min of centrifugation at a speed of 2000 rpm, and diluted to a 0.40% solution in just 16.00 min. For 1000 NTU of diatomite-simulated wastewater, the optimal turbidity removal rate of the suspension was 99.50%, which was higher than the optimal turbidity removal rate of 98.40% for the inorganic flocculant polymeric aluminum chloride (PAC). For oilfield wastewater, the optimal turbidity removal rate of the CPAM suspension was 35.60%, which was higher than the optimal turbidity removal rate of 28.40% for solid particle CPAM. In a scale-up test, the CPAM suspension achieved a good application effect.

RAFT/ROP binary polymerization towards well-defined graft copolymers

The RAFT/ROP binary polymerization enables the efficient synthesis of controlled and well-defined poly(N-hydroxyethyl acrylamide)–poly(ε-caprolactone) (PHEAA-g-PCL) as compared to the conventional “two-step” method.

Compatibility and efficiency of hydrophilic/hydrophobic nano silica as rheological modifiers and fluid loss reducers in water-based drilling fluids

Nano-silica (nano-SiO2), as the most widely used nanometer-sized additive, exhibits various functions in water-based drilling fluids (WBDFs), such as rheological adjustment, filtration control, and shale inhibition. However, the exertion of these functions greatly depends on their type, concentration, and other characteristics. In this study, typical hydrophilic nano-SiO2 (phi-SiO2) and hydrophobic nano-SiO2 (pho-SiO2) have been utilized as the research samples. Their compatibility and efficiency in four different WBDFs containing sodium carboxymethyl cellulose (CMC), potassium humate (KHm), sulfonated phenolic resin (SMP), and white asphalt (NFA) were investigated by measuring their influence on the filtration and rheological properties. Results indicated that these nano-SiO2 displayed different effects in WBDFs and didn't always have a positive effect. At room temperature and 150 °C, both phi-SiO2 and pho-SiO2 had a thickening and shear force-increasing effect. The viscosity and yield point of four WBDFs improved with increasing the concentration of these two nano-SiO2, whereas the enhanced degree of pho-SiO2 was stronger than that of phi-SiO2. Meanwhile, phi-SiO2 hasn't decreased the fluid loss of WBDFs while pho-SiO2 could be applied as a fluid loss reducer and performed good compatibility with CMC and KHm, even at 150 °C. However, the filtration control performance of pho-SiO2 was also dependent on its concentration and the additive type in WBDFs. The analysis based on microstructure demonstrated that phi-SiO2 were easy to agglomerate and much sediment was formed after the filtration measurements, leading to more permeation channels and an increase in fluid loss volume. The improved viscosity, enhanced shear force, stable colloidal structure as well and the formation of a hydrophobic barrier after adding pho-SiO2 contributed to reducing the fluid loss volume of WBDFs. It was suggested that the use of nano-SiO2 should be determined according to the characteristics of nanoparticles, types of used additives, and other formation conditions.