Biopolymer-based gels have a significant impact on controlling rheological properties in a number of industrial processes. Many natural polymers such as animal and plant proteins are used as gelling ...agents. In particular, zein is a biocompatible protein that embraces almost 80% of the whole protein content of corn. The current study was designed to characterize various gels made up of zein, in order to provide useful formulations for various applications. Diffusing wave spectroscopy in association with dynamic rheology was used to obtain a full physico-chemical characterization of the zein dispersions. Zein gels were prepared using different amounts of protein (10%, 12.5%, 15% and 20% w/v) and their stability was evaluated by Turbiscan Lab®. The microrheological parameters e.g. SLB (solid-liquid balance), EI (elasticity index), MVI (macroscopic viscosity index) and the storage (G′) and loss (G″) moduli were evaluated as a function of strain, frequency, time, and temperature providing information on the linear viscoelastic region, structural assembly, and thermal characteristics. The formulations containing 15% and 20% w/v of zein formed stable dispersions especially at 37 °C. The high protein concentration showed storage moduli values significantly greater than those of viscous moduli, demonstrating that the elastic character became dominant. These findings were confirmed up to 50 °C. The viscosity of these samples decreased as the shear rate increased, thus demonstrating a typical pseudoplastic or shear thinning behavior. Our findings showed that dispersions containing 20% w/v of zein are promising low-cost formulations to be used as a gel in various fields of application.
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•The formulations containing 15% and 20% w/v of raw zein formed stable dispersions.•The high protein concentration promoted a typical pseudoplastic behavior.•Gels containing 20% w/v of raw zein are promising low-cost formulations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Linear models are commonly used to describe the early structural build-up of cement-based materials. However, some studies have shown that there exists a faster non-linear phase before the linear ...phase. In this study, a simple non-linear thixotropy model is presented to describe the structural build-up process. It was quantified using static yield stress and storage modulus, which are measured through the stress growth protocol and small amplitude oscillatory shear (SAOS) tests, respectively. The effect of pre-shear, rest condition and viscosity modifying admixtures (nanoclay and diutan gum) on the build-up behavior are studied. The results showed distinctly different trends between static yield stress and storage modulus. This may be attributed to the two different structures of fresh cement pastes, i.e. floc structures and C-S-H structures, measured by the stress growth protocol and SAOS test, respectively.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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Bioprinting technologies have tremendous potential for advancing regenerative medicine due to the precise spatial control over depositing a printable biomaterial, or bioink. Despite ...the growing interest in bioprinting, the field is challenged with developing biomaterials for extrusion-based bioprinting. The paradigm of contemporary bioink studies relies on trial-and-error methods for discovering printable biomaterials, which has little practical use for others who endeavor to develop bioinks. There is pressing need to follow the precedent set by a few pioneering studies that have attempted to standardize bioink characterizations for determining the properties that define printability. Here, we developed a pentenoate-functionalized hyaluronic acid hydrogel (PHA) into a printable bioink and used three recommended, quantitative rheological assessments to characterize the printability: 1) yield stress, 2) viscosity, and 3) storage modulus recovery. The most important characteristic is the yield stress; we found a yield stress upper limit of ∼1000 Pa for PHA. Measuring the viscosity was advantageous for determining shear-thinning behavior, which aided in extruding highly viscous PHA through a nozzle. Post-printing recovery is required to maintain shape fidelity and we found storage modulus recoveries above ∼85% were sufficient for PHA. Two formulations had superior printability (i.e., 1.5 MDa PHA − 4 wt%, and 1 MDa PHA − 8 wt%), and increasing cell concentrations in PHA up to 9 × 106 cells/mL had minimal effects on the printability. Even so, other factors such as sterilization and peptide modifications to enhance bioactivity may influence printability, highlighting the need for investigators to consider such factors when developing new bioinks.
Bioprinting has potential for regenerating damaged tissues; however, there are a limited number of printable biomaterials, and developing new bioinks is challenging because the required material physical properties for extrusion-based printing are not yet known. Most new bioinks are developed by trial-and-error, which is neither efficient nor comparable across materials. There is a need for the field to begin utilizing standard methods proposed by a few pioneering studies to characterize new bioinks. Therefore, we have developed the printability of a hyaluronic acid based-hydrogel and characterized the material with three quantitative rheological tests. The current work impacts the bioprinting field by demonstrating and encouraging the use of universal bioink characterizations and by providing printability windows to advance new bioink development.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The structural build-up of cement-based materials is often characterized by the determination of the evolution of static yield stress with time. This property is crucial to many applications of ...concrete. However, the measurement of static yield stress may disturb the structure of cement-based material. As a consequence, the true structural build-up of the materials may not be detected. In this paper, the evolution of static yield stress and storage modulus (G′) determined by small amplitude oscillatory test was determined to characterize the evolution of the structural build-up of cement pastes. Results showed that G′ and static yield stress developed similarly with time. When the tests were carried out on the same sample, the measurement of static yield stress disturbed the structure of cement paste and had a significant effect on the following measurement of G′, but a slight effect on the following measurement of static yield stress.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This study combines vinylogous urethane (VU) and β-amino ester chemistry for the synthesis of covalent adaptable networks (CANs). The resulting CANs are synthesised using a range of diacetoacetates ...and commercially available diacrylates along with tris(2-aminoethyl)amine, which functions as both amine and crosslinker. The CANs are extensively analysed to determine both their thermal and rheological properties. Several re-processable elastomeric materials are obtained, thanks to the use of polypropylene glycol-containing diacetoacetates of varying molecular weights and are analysed in more detail and compared with VU and amino-ester reference materials. Frequency sweep measurements show no noticeable drop in storage modulus of these CANs between 100-180 °C, indicating a maintained crosslink density. The elastomeric CANs are recycled multiple times, exhibiting no clear loss of dynamic behaviour or any obvious side-reactions.
This study describes covalent adaptable networks with enhanced processability and creep resistance by combining vinylogous urea/urethane and β-amino ester based dynamic covalent motifs.
Amide bioconjugation and interfacial enzyme polymerization are designed to provide a general strategy for regulating the mechanical strength (storage modulus from 3 kPa to 100 kPa) of printable ...hydrogel inks.
Structural colors have profound implications in the fields of pigments, displays and sensors, but none of the current non‐iridescent photonic materials can restore their functions after mechanical ...damage. Herein, we report the first self‐healable organogel nanocomposites with angle‐independent structural colors. The organogel nanocomposites were prepared through the co‐assembly of oleophilic silica nanoparticles, silicone‐based supramolecular gels, and carbon black. The organogel system enables amorphous aggregation of silica nanoparticles and the angle‐independent structural colors in the nanocomposites. Moreover, the hydrogen bonding in the supramolecular gel provides self‐healing ability to the system, and the structural colored films obtained could heal themselves in tens of seconds to restore storage modulus, structural color, and surface slipperiness from mechanical cuts or shear failure repeatedly.
Colors, the director′s cut: Organogel nanocomposites capable of fast self‐healing are prepared. The gels can form films that have angle‐independent structural colors and are water‐repellant, properties that are restored on self‐healing.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Aromatic N-heterocyclic compounds are very important chemicals, which are currently produced mostly from petroleum. Here we report that a pyridazine-based compound ...6-(4-hydroxy-3-methoxyphenyl)pyridazin-3(2H)-one (GSPZ) can be efficiently synthesized by the Friedel-Crafts reaction of guaiacol and succinic anhydride, both of which can be derived from biomass. GSPZ is then treated with bio-based epichlorohydrin to prepare the epoxy resin precursor GSPZ-EP. With 4,4'-diaminodiphenylmethane as curing agent, GSPZ-EP possesses higher glass transition temperature (187
C vs. 173
C) and shows a 140%, 70 and 93% increase in char yield (in N
), storage modulus (30
C) and Young's modulus, respectively when compared with a standard petroleum-based bisphenol A epoxy resin. Moreover, the cured GSPZ-EP shows good intrinsic flame retardancy properties and is very close to the V-0 rating of UL-94 test. This work opens the door for production of aromatic N-heterocyclic compounds, which can be derived from biomass and employed to construct high performance polymers.
•Proportion of fly ash in the GGBFS-fly ash mixture governs the setting time of AASF.•The mechanical evolution of network in AASF mixtures was studied by storage modulus.•The rate of coagulation and ...rigidification is higher in AASF when compared with OPC.•Quick setting of AASF mixtures is due to rapid formation of hydration products.
This study aims to investigate the setting of alkali activated ground granulated blast furnace slag and fly ash mixtures by following the mechanical and chemical evolution of structure of the precursor-activator suspension during early ages. The mechanical evolution was followed by measuring the evolution of storage modulus. The chemical evolution was followed by measuring the amount of hydrates formed at different times. The dependence of setting time of alkali activated slag mixtures on the amount of incorporated flyash, molar modulus and activator dosage was also studied. This study shows that the quick setting of alkali activated slag mixtures is due to rapid coagulation followed by rapid rigidification of network with the formation of hydration products. In comparison, the setting in OPC systems is due to a network formed by partially hydrated or anhydrous cement particles. The proportion of fly ash in GGBFS-fly ash mixture and molar modulus of the activator were found to have a significant effect on the setting time of alkali activated ground granulated blast furnace slag and fly ash binders.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Vitrimers have been emerged as a new class of polymers with many attractive properties of material processing such as reshaping, recycling and repairing. Herein, a new type of vitrimers (BDSER) based ...on thermosetting dynamic epoxy network with double disulfide bonds was synthesized by the reaction of a difunctional epoxy monomer containing disulfide bonds with 4,4′-disulfanediyldianiline (4-AFD). Our results demonstrated that the relaxation time of BDSER at 200 °C was as short as 9 s without any catalyst. The storage modulus of BDSER was up to about 2.2 GPa and its glass transition temperature was higher than 130 °C. Additionally, the thermodynamic and chemical properties of BDSER were no significant loss after 3 cycles of continuous breaking/compression molding. Furthermore, the resistance of CNT/PPy/Vitrimer composites (CPV), synthesized by doped BDSER with the polypyrrole (PPy) decorated multi-walled carbon nanotubes (WMCNTs), was decreased to 109 Ω even the mass ratio was only 1%wt, which could be used a promising candidate as self-repairing materials in the field of antistatic.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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