In this article, frequency analysis of multi-sized hybrid nano-composites (MHC) disk (MHCD) resting on elastic media and located in an environment with gradually changed temperature feature is ...presented. Carbon fibers (CF) or carbon nanotubes (CNTs) in the macro or nano sizes respectively are responsible for reinforcing the matrix. For prediction of the efficiency of the properties MHCD's modified Halpin-Tsai theory has been presented. The strain-displacement relation in multi-sized laminated disk's dynamics through applying third-order-shear-deformation-theory is determined. The energy methods called Hamilton's principle is applied for deriving the motion equations along with boundary conditions, which has ultimately been solved using generalized differential quadrature method. The deflection as the function of time can be solved by the fourth-order Runge-Kutta numerical method. At the final stage, the outcomes illustrate that patterns of FG, fibers' various directions, the W
CNT
and V
F
factors, top surface's applied temperature have considerable impact on the MHCD's dynamics. Another important consequence is that MHC structure with FG-A and UD patterns have a similar effect on the dimensionless natural frequency of the GPLRC disk, while FG-X has the lowest stability and natural frequency. A useful suggestion is that increasing the value of the length to thickness ratio of MHC not only decreases the central deflection of the structure through time but also causes to decrease real-time domain changes for the MHC viscoelastic annular plate. Numerical results declare that viscoelastic disks fabricated from the hybrid nanocomposites can endure higher frequencies compared with those consisted of conventional composites.
The aim of this research work is to develop high performance structural composites using Kevlar 29 (K) and Cocos nucifera sheath (CNS). The Kevlar and CNS laminates were fabricated by using hand ...lay-up method followed by hot pressing. The weight ratios of Kevlar/CNS are as follows 100/0 (S1), 75/25 (S2), 50/50 (S3), 25/75 (S4), 0/100 (S5). Thermal and viscoelastic properties of laminated composites were investigated as a function of temperature using thermogravimetric (TGA) and dynamic mechanical analyzer (DMA). The obtained results revealed that the thermal stability, char residue of S2 laminate was higher compared S3, S4 and S5 laminates. Moreover, S2 laminates showed comparable thermal stability with Kevlar/epoxy composites (S1). Differential scanning calorimetry (DSC) results revealed that hybrid composite (S2) offers a virtuous resistance or stability towards heat in the epoxy composites. Viscoelastic analysis results showed that the storage modulus (E′) and loss modulus (E″) of S2 composites were higher among the laminates due to improved interfacial interactions and effective stress transfer rate. Moreover, the damping of hybrid laminates (S2) almost closer to Kevlar/epoxy laminates (S1). Hence, it was observed that hybrid Kevlar/CNS composites (S2) can be efficiently utilized for advanced structural applications where rigidity, thermal stability along with renewability are prime requirements.
Protein-polysaccharide complex coacervates self-assembled via electrostatic interactions generally exhibit superior functional properties than the individual biopolymer. Herein, the main objective of ...this work was to investigate physicochemical properties of complex coacervates formed with ovalbumin (OVA) and carboxymethylcellulose (CMC) with two different charge densities (CMC0.7, CMC1.2) at pH 3.0, 3.5, and 4.0 and the properties of coacervates stabilizing emulsions with a high oil content. The results showed that the contents of protein and polysaccharide in OVA/CMC complex coacevates decreased with the increase of pH, and the microscopic network structure of the complex coacervates changed from compact to loose, which was mainly due to the weakening of the electrostatic attraction between OVA and CMC. With the higher charge density of CMC1.2, the OVA/CMC1.2 complex coacervates exhibited a denser microscopic network structure and higher storage and loss moduli and complex viscosity than OVA/CMC0.7. The stronger electrostatic attraction between OVA and CMC led to poorer oil binding ability and emulsion stability when coacervates were used to prepare emulsions with 80% v/v oil, particularly evident for OVA/CMC1.2 coacervates. With moderate electrostatic attraction at pH 4.0, OVA/CMC coacervates exhibited an outstanding ability to form and stabilize the emulsions. These findings indicate that OVA/CMC complex coacervates can be used as a new option for food texture manipulation and as a stabilizer for high oil phase food systems.
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•Viscoelasticity of complex coacervates depend on the pH and charge density of CMC.•Composition and microstructure of coacervates were significantly affected by pHs.•OVA/CMC complex coacervates exhibited outstanding HIPEs stabilization at pH 4.0.•Charge density of CMC has significant effect on the HIPEs stability of coacervates.
Methods for mechanical assembly can form structures with elaborate 3D configurations, and broad potential applications in advanced microsystems technologies. In article number 2100026, John D. Finan, ...John A. Rogers, and co‐workers demonstrate soft, transparent 3D structures designed to gently constrain organoids for studies of their mechanical properties. Measurements reveal that the effective moduli of these systems depend on age and exposure to drugs.
•The effect of NaOH concentration on the flow and viscoelastic properties of fly ash-based geopolymers was studied.•The dissolution and geopolymerization kinetics strongly depended on the NaOH ...concentration.•Two domains of NaOH concentration were defined based on the rheological behavior and FTIR spectroscopy.•Increasing the temperature of fly ash-based geopolymer at fresh state enhanced its rigidification rate and storage modulus.
The objective of this paper is to study the flow and viscoelastic properties of fly ash-based geopolymers activated at different concentrations of NaOH. Although the investigated geopolymers exhibited a shear thinning behavior, their rheological properties are greatly affected by the NaOH concentrations. Increasing the concentration of NaOH up to 7 mol/L resulted in an increase of the yield stress, the storage modulus, and the rigidification rate of the geopolymers. However, the use of higher concentrations resulted in lower yield stress, storage modulus, and rigidification rate. The competition between dissolution and geopolymerization processes seems to be the key parameter affecting the evolution of rheology of the investigated geopolymers. In the case of a NaOH concentration lower than 7 mol/L, the geopolymerization process is accelerated. However, when the concentration exceeds 7 mol/L, the geopolymerization is delayed despite the higher dissolution. This is probably due to the dominance of the repulsive forces between particles, thus preventing the network formation. Geopolymers activated at a NaOH concentration of 2 mol/L and a temperature around 40 °C exhibited comparable rheological and viscoelastic properties than those activated at higher concentration of 7 mol/L and a temperature of 25 °C.
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In the preparation of oleogels based on Pickering-emulsions, the choice of the preparation route is critical to withstand drying under ambient conditions, as it conditions the ...composition of the interfacial layer at the oil-water interface.
Hexadecane and olive oil oleogels were prepared using an emulsion-template approach from oil-in-water emulsions formulated with cellulose nanocrystals (CNC) and sodium caseinate (CAS) added in different orders (CNC/CAS together; first CAS then CNC; first CNC then CAS). The oleogels were formed from preconcentrated emulsions by drying at ambient temperature. The structure of the gels was characterised by confocal laser scanning microscopy, and the gels were assessed in terms of viscoelastic properties and redispersibility.
The properties of oleogels were controlled by 1) the composition of the surface layer at oil-water interface; 2) the amount and type of non-adsorbed stabilizer; and 3) the composition and viscosity of oils (hexadecane vs. olive oil). For the oleogels prepared from starting emulsions stabilized with CNC with subsequent addition of CAS, and free CAS present in aqueous phase, the elastic component was prevalent. Overall, the dominating species at the oil-water interface controlled the emulsion behaviour and stability, as well as viscoelastic behaviour of the resulting oleogels and their redispersibility.
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This review discusses the physicochemical and mechanical properties of porcine gastrointestinal mucus from a rheological point of view. Considering mucus as a viscoelastic gel that ...functions as a biological barrier by limiting particles passage, lubricating the gastrointestinal tract, and protecting the stomach from gastric acids. The viscoelastic and protective properties of mucus are mainly produced by its mucin network, which is stabilized through electrostatic, hydrophobic and hydrogen bonding interactions. Otherwise, mucus rheology is determined by its polyanionic nature at physiological pH. At neutral pH, mucus presents a viscous behavior produced by chains crosslinking. While, at acidic pH, mucus exhibits an elastic behavior related with the extended conformation that produces mucus gelation at the stomach. Additionally, rheology studies the degree of adhesion between a polymer-mucus mixture through rheological synergism, and how it varies at different pH conditions. Finally, mucoadhesion phenomenon is exemplified with chitosan (cationic) and poly (lactic-co-glycolic) acid (anionic) polymers.
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•The higher degree of PVA hydrolysis had better foaming properties.•The entanglement of starch and PVA increased the melt strength of the foam.•The density of the foams was equivalent ...to that of EPS foams.
Growing global awareness of environmental issues has led to increased research interest in starch-based foams as a biodegradable packaging material. However, limitations such as low foaming ratio and poor water resistance hinder their development and industrial application. This study aimed to address these challenges by investigating the effect of the polyvinyl alcohol (PVA) content and hydrolysis degree on foam properties, providing insight into the intricate interplay between melt viscoelasticity and foam characteristics. The results demonstrated that the foaming behaviors, viscoelastic properties, thermal stabilities and mechanical performances of the foams were significantly improved with increasing hydrolysis degrees of PVA. These enhancements were attributed to hydrogen bonding interactions and intermolecular entanglements between starch and PVA chains. Additionally, the incorporation of PVA resulted in a remarkable reduction in the water absorption capacity (WAC) of the foams. Specifically, the foam containing 20% PVA with a hydrolysis degree of 98% exhibited the lowest WAC of 7.46% at 75% RH, the lowest bulk density of 12.42 kg/m3, the highest foaming ratio of 54.66, and the highest porosity of 99.39%. These properties were equivalent to those of commercially available expanded polystyrene (EPS). Furthermore, the addition of 20% PVA yielded the highest compressive strength of 110.58 MPa and the highest recovery of 92.75%, indicating great potential for diverse cushioning applications. Overall, this work highlights the significant potential for wider application of starch-based foams in large-scale industrial settings.
The objective of this study was to investigate the complex coacervation between ovalbumin (OVA) and carboxymethylcellulose (CMC) with different degrees of substitution (CMC 0.7 and CMC 1.2). ...Turbidity titration showed that complexes or coacervates could form between OVA and CMC by electrostatic interactions depending on pH changes. Specially, the critical pH values (pHc, pHφ1) increased with the salt ion concentration raising from 0 to 20 mM, while further increasing the ionic strength reduced the formation of complex coacervates. The ITC results also showed that when CNaCl = 20 mM, the complex coacervation between OVA and CMC exhibited the highest stoichiometric ratio and binding constant. When CNaCl≥200 mM, the complex coacervation changed from spontaneous exothermic (ΔG<0, ΔH<0) to endothermic (ΔG<0, ΔH>0) due to the shielding effect by high concentration of salt ions. In addition, dynamic rheological properties showed that the OVA/CMC coacervates displayed the strongest elastic modulus at CNaCl = 20 mM, and the elastic modulus of all samples were greater than the viscous modulus. These findings all suggested a salt-enhanced effect at lower salt concentrations or a salt-reduced effect at higher salt concentrations. On the other hand, the stoichiometric and viscoelastic properties of OVA/CMC 1.2 coacervates were greater than OVA/CMC 0.7 coacervates, indicating that CMC 1.2 had stronger protein binding capacity owing to higher charge density.
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•The complex coacervation of OVA/CMC were investigated.•The formation of OVA/CMC complex coacervates can be promoted with CNaCl<20 mM.•The highest binding constant and enthalpy changes were observed at CNaCl = 20 mM.•The OVA/CMC coacervates displayed the strongest elastic modulus at CNaCl = 20 mM.•CMC 1.2 had stronger protein binding capacity owing to the higher charge density.
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