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.
Pulse hulls are composed of cell wall polysaccharides and are a concentrated source of dietary fibre. However, the dense microstructure hinders their industrial application, resulting in poor ...techno-functional properties. To improve their functionality, the cell wall (cellulose, hemicellulose, and pectin) is disrupted by combining enzymatic pre-treatments and microfluidization. This work aims to study the impact of a fixed reduction of the insoluble mass by selective enzymatic pre-treatment of pulse hulls on the composition, microstructure, water binding, and rheological properties of microfluidized suspensions. To that end, enzymatic pre-treatments using cellulase, hemicellulase, pectinase, and their binary and ternary mixtures were conducted to reduce insoluble mass content. The combined treatment improved the water-binding properties, leading to the formation of viscoelastic gels. Microfluidized suspensions enzymatically pre-treated with a binary mixture of cellulase and hemicellulase presented the highest water binding capacity, viscosity, and viscoelasticity. The partial enzymatic degradation of the cellulose-hemicellulose network weakened the interactions between both polysaccharides. It facilitates the disruption of the particles and the release of high molecular weight soluble dietary fibre (HMWSDF), which are gelling substances. On the contrary, an enzymatic pre-treatment using only cellulase increased the content of low molecular weight soluble compounds, resulting in low viscous and viscoelastic suspensions. Thus, the concentration of remaining microfibrillated cellulose and HMWSDF are key parameters controlling the rheological behaviour of the suspensions. This study enhances comprehension regarding pea hulls' molecular and macromolecular modifications, potentially enabling the production of tailor-made pulse hull suspensions.
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•Enzymatic pretreatment and microfluidization form viscoelastic gels from pulse hulls.•Intense cellulosic hydrolysis reduces viscoelasticity by loss of fibrillated cellulose.•Simultaneous hydrolysis of hemi- and cellulose boosts viscoelasticity.•Viscoelasticity increases with size reduction and release of gelling-substances.•Enzymatic pretreatment defines particle size, composition, and microstructure.
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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•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.
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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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