Energy Storage Modulus Research Articles

Effects of ultrasonic treatment on the structure and rehydration peculiarity of freeze-dried soy protein isolate gel

• The structure of freeze-dried SPI gel was affected by ultrasonic treatment. • The storage modulus of freeze-dried SPI gel was affected by ultrasonic treatment. • Ultrasonic treatment affects network structures of freeze-dried SPI gel. • Ultrasonic treatment affects the rehydration peculiarity of freeze-dried SPI gel. Different levels of ultrasonic power (0, 100, 200, 300, 400, and 500 W) were applied to soybean protein isolate [SPI] solution to evaluate the effects of ultrasonic treatment (4°C) on the microstructure and rehydration peculiarity (rehydration kinetics, texture profile analysis [TPA], water-holding capacity, and water distribution) of freeze-dried SPI gel. Suitable ultrasonic treatment (4°C) reduced the average size and increased the energy storage modulus of SPI solution relative to those of untreated SPI solution. The formed gel has a uniform and dense network structure. The improved the water-holding capacity and texture, and enhanced the capillary percolation of freeze-dried SPI gel during rehydration. And enlarged the size of holes in rehydrated SPI gel and made the water release rate, relaxation time T 22 , M 22 , gel hardness of rehydrated SPI gel were significantly higher than that of fresh SPI gel ( P < 0.05). Therefore, freeze-dried SPI gel with a fine texture and high rehydration rate can be prepared when ultrasonic power of 300 W.

Synthesis, processing and characterization of impact hardening gel (IHG) reinforced Kevlar fabric composites

The impact hardening gel (IHG) reinforced Kevlar fabric composite is a new type of protective material prepared by Kevlar fabric as dispersed phase and IHG as matrix. In this paper, IHG was strengthened by SiO2 and T-ZnOw particles, and then the Kevlar fabric was compounded by dipping and sandwich lamination. With the help of rheological testing and yarn pull-out testing, the relationship between microscopic shear rate and the macroscopic linear velocity was established. To verify the enhancement effect of the material, the low velocity impact testing was used to analyze the impact response and damage morphology. And the energy dissipation mechanism of the material was obtained. As a result, the reinforcing particles significantly increased the energy storage modulus of IHG, and the friction between the fibers of Kevlar/IHG impregnated composites. The structure-optimized sandwich material had a significant energy absorption effect, which was 41.9% higher than that of the untreated Kevlar fabric. This provided the theoretical basis and reference for the optimal development of lightweight anti-impact flexible protection materials.

High flow polypropylene composites reinforced by glass filaments: Manufacturing process and property evaluations

High flow (hf)-modified polypropylene (PP) fibers and glass filaments (GFs) were made into webs, which were then laminated orthogonally and needle punched to make GF/PP-hf preforms. These preforms were then hot pressed to produce GF/PP-hf composites. Similarly, GFs and nonmodified PP were made into GF/PP composites with the aforementioned process to serve as the control group. The structure, morphology, and mechanical performances (i.e. tensile, bending, and impact strength) of GF/PP and GF/PP-hf composites were characterized and tested using differential scanning calorimeter and dynamic mechanical analysis. The test results showed that the GF/PP-hf composites are composed of reinforcing filaments at a weight ratio of 43.40% and an average length of 22.9 mm. Consequently, they had advantages of high fiber content, long fiber length, and adjustable fiber orientation. Compared to GF/PP composites, GF/PP-hf composites exhibited good dispersion of GFs in the matrices, good bonding between filaments and the matrix, and a relatively lower porosity factor of 2.92%. Moreover, the glass transition temperature and crystallinity were improved by 15.2°C and 10.42%, respectively. When the temperature was lower than 160°C, GF/PP-hf composites preserved a higher energy storage modulus and a lower loss factor. Furthermore, GF/PP-hf composites exhibited good static mechanical properties, including the tensile strength of 118 MPa, the tensile modulus of 5830 MPa, the bending strength of 180 MPa, the bending modulus of 780 MPa, and the impact strength of 33 KJ m−2, which are 30, 29.6, 78.2, 68.3, and 32%, respectively, higher than those of the control group.

Relationship between the Molecular Coil Dimension and the Energy Storage Modulus of Polymer Solution Configured with Oilfield-Produced Sewage.

Polymer viscoelastic solution is the non-Newtonian fluid and widely used in oil production. In the process of seepage, the mechanism of the polymer solution with different molecular coil dimensions (Dh) flooding on remaining oil is unknown. By using the dynamic light scattering instrument, the molecular coil dimension of the polymer solution is tested. By using the HAAKE rheometer, the creep recovery test data of the polymer solution under the same creep time condition are obtained. The effects of polymer solutions with different Dh on residual oil are observed, by using the visible pore model. The results show that the higher the molecular weight (Mw) of the polymer, the larger the size of the molecular coil dimension. The elasticity characteristics of the polymer solution are sensitive to the molecular coil dimension. As Dh of polymer molecules becomes larger, the contribution of the elastic portion to the viscosity of the polymer solution increases. The higher the Mw of polymer is, the longer the molecular chain is and the size of Dh is larger. On the condition of the polymer solution with different Mw with 2.5 g/L, when Dh is between 320.0 nm and 327.8 nm, the ratio of the elastic part in the apparent viscosity exceeds the proportion of the viscous part, and the polymer solution composition after these data can be used as a comparative study of elasticity for residual oil use. In the visible pore model, the pore-throat ratio is 3.5, the ER of water flooding is 54.26%, the ER of the polymer solution with Dh = 159.7 nm is 75.28%, and the increase of ER is 21.02% than that of water flooding. With the increase of Dh to 327.8 nm, the final ER of the experimental polymer solution is 97.82%, and the increase of ER of the polymer solution than that of water flooding is 43.56%. However, in the model with a pore-throat ratio of 7.0 and the same polymer solution with Dh = 327.8 nm, the increase of ER of the polymer solution is only 10.44% higher than that of water flooding. The effect of the polymer solution with the same Dh is deteriorated with the increase of the pore-throat ratio.

Epoxy nanocomposites with high thermal conductivity and low loss factor: Realize 3D thermal conductivity network at low content through core-shell structure and micro-nano technology

Dielectric polymers with high thermal conductivity are very promising in the fields of aerospace and electronic device packaging. However, composites with excellent dielectric properties usually have low thermal conductivity. It is usually to fill the polymer with thermal conductivity particles to improve the thermal conductivity, but the high content of filler often reduces the mechanical properties of the polymer. In this paper, the traditional insulating polymer epoxy resin was used as the matrix, by covering the surface of silicon carbide with graphene to form a core-shell structure and co-filled with nano diamonds to achieve the preparation of high-performance epoxy resin at low content. The results showed that at the filling content of 30 wt%, the thermal conductivity of epoxy nanocomposites showed a dramatic thermal conductivity enhancement of 1263%, the energy storage modulus increased by 1.1 GPa, and the dielectric loss remained unchanged at 50 Hz. The advantages of the composite are the structural design and surface modification of the filler, which not only take advantage of its inherent advantages, but also improve the interface area with the epoxy matrix. The composite materials with excellent properties are expected to provide theoretical guidance for the application of high thermal conductivity dielectric materials.

Photosensitive supramolecular hydrogel based on biaryltetrazole modified with short peptide

Here we report a photosensitive supramolecular hydrogel formed by MeO-Tet-GA. MeO-Tet-GA can self-assemble to form supramolecular hydrogel in neutral buffer. The formed hydrogel has good mechanical properties, and the dynamic energy storage modulus G ′ is above 500 Pa. Based on the intermolecular photo-click reaction between biaryltetrazole and the terminal alkene, we could further modify the hydrogel with hydrophilic sodium 4-vinylbenzenesulfonate to disturb the hydrogel and induce the degradation of hydrogel. We also tried to use this supramolecular hydrogel for three-dimensional culture of mouse breast cancer 4T1 cells. We found that MeO-Tet-GA has excellent biocompatibility and did not cause significant 4T1 cell death after three days of culture. Overall, this work demonstrates that supramolecular hydrogel formed by MeO-Tet-GA holds great promise in long-term three-dimensional cell culture and in studying cell behaviors through photo-modulation of cell microenvironment.

Studies on the curing behavior, thermal, and mechanical properties of epoxy resin‐co‐amine‐functionalized lead phthalocyanine

AbstractA high performance copolymer was prepared by using epoxy (EP) resin as matrix and 3,10,17,24‐tetra‐aminoethoxy lead phthalocyanine (APbPc) as additive with dicyandiamide as curing agent. Fourier‐transform infrared spectroscopy, dynamic mechanical analysis (DMA), differential scanning calorimetric analysis (DSC), and thermogravimetric analysis (TGA) were used to study the curing behavior, curing kinetics, dynamic mechanical properties, impact and tensile strength, and thermal stability of EP/APbPc blends. The experimental results show that APbPc, as a synergistic curing agent, can effectively reduce the curing temperature of epoxy resin. The curing kinetics of the copolymer was investigated by non‐isothermal DSC to determine kinetic data and measurement of the activation energy. DMA, impact, and tensile strength tests proved that phthalocyanine can significantly improve the toughness and stiffness of epoxy resin. Highest values were seen on the 20 wt% loading of APbPc in the copolymers, energy storage modulus, and impact strength increased respectively 388.46 MPa and 3.6 kJ/m2, Tg decreased 19.46°C. TGA curves indicated that the cured copolymers also exhibit excellent thermal properties.

A novel method to produce sustainable biocomposites based on thermoplastic corn-starch reinforced by polyvinyl alcohol fibers.

Adding reinforced fiber or cross-linking agent into thermoplastic starch (TPS) is an effective method to improve its performance. Herein, biodegradable polyvinyl alcohol fiber (PVAF) and sodium hexametaphosphate (SHMP) were not added into TPS directly; the PVAFs were preliminary treated (pre-soaking) by an SHMP solution, and then mixed with starch and glycerol to prepare 2 wt% PVAF/TPS composites through extrusion and injection molding. This process promoted crosslinking action between PVAFs and starch, and as a consequence enhanced the mechanic and dynamic mechanic behavior. The PVAFs with different immersion times were characterized by SEM, FTIR, and WAXD. The results confirmed that the SHMP coating was formed by a chemical bond connection on the surface of the PVAFs, particularly for the PVAFs soaked for 1.5 h, which produced a corresponding PVAF/TPS composite with a maximum tensile strength of 9.18 MPa and an impact strength of 21.29 kJ m−2. The corresponding tensile fractured cross-section images were shown by SEM. The DMA curves indicated that the pre-soaked PVAFs effectively improved the energy storage modulus and transition temperature of composites, and the activation energy of the starch macromolecules reached a maximum of 349.9 kJ mol−1 during the dynamic mechanic process. The contact angle attained a maximum of 66.25°. Compared with TPS, the pre-soaked PVAF-reinforced PVAF/TPS composites had better mechanical properties, good processability through traditional extrusion and injection molding, reduced water wettability, and potential applications for packaging and catering.

Study of the addition of the hybrid sisal fibers on the dynamic mechanical property of SFs reinforced polylactic acid (PLA) composites

When sisal fiber (SF) is added into polylactide (PLA) matrix, the storage modulus of PLA/SF composites increases greatly which indicate the rigidity of the composite material increases obviously. Comparing PLA composites with pure PLA, it can be found that the glass transition temperature (Tg) of PLA composites is significantly higher than that of PLA which showed the heat resistance of the PLA composites can be improved obviously because of the addition of SFs in PLA matrix. The energy storage modulus of PLA/HSFs is the highest of all PLA composites. HSFs could improve the dynamic mechanical properties of PLA composites more significantly than ASFs and USFs.

Styrene Butadiene Rubber/Silicone Rubber Blends Filled With Dough Moulding Compound

Blends of styrene butadiene rubber (SBR)/methyl-vinyl silicone rubber (MVQ) filled with dough molding compound (DMC) were prepared and the effects of various amounts of the SBR, as a compatibilizer of MVQ and DMC, on the mechanical properties and the oxygen index of the DMC filled SBR/MVQ blends were investigated. Dynamic mechanical analysis (DMA) and infrared spectrum analysis (IR) of the DMC/SBR/MVQ blends were also investigated. The results showed that the mechanical properties of the DMC filled MVQ blends were improved when SBR was used as a compatibilizer; the best mass ratio was 60 phr (parts per hundred total rubber) DMC, 25 phr SBR and 75 phr MVQ. The volume electric resistivities of the DMC filled SBR/MVQ blends with various DMC mass ratios were all above 5.8 × 1012 Ω•m; i.e., the electrical insulating property of the blends was excellent. Compared with the blends without DMC and the blends without SBR, the energy storage modulus and the peak area of the loss factor tan δ of the DMC reinforced SBR/MVQ blends were largest; the addition of DMC and SBR improved the thermal properties of the blends.

Effect of molecular weight of side chain liquid crystalline polymers on properties of liquid crystal physical gels

A series of side chain liquid crystalline polymers (SCLCPs) poly[ω-4′-cyano-(1, 1′-biphenyl)] acrylate (P0ACB) with different molecular weight were prepared and used as gelator to fabricate liquid crystalline physical gels (LCPGs). The relationship between molecular weight of side chain liquid crystalline polymers and the properties of liquid crystalline physical gels were also discussed in detail. Testing results showed that when the molecular weight of polymers was less than 3.61 × 104, the minimum gelation concentration (MGC) of liquid crystalline physical gels decreased from 3 wt% to 0.2 wt% and gel-sol phase transition temperature (TGS) increased from 99 °C to 185 °C with increasing molecular weight. The driving voltage and contrast ratio increased obviously and the off state response time decreased with increasing molecular weight. However, when the molecular weight of polymers was greater than 3.61 × 104, the stability and the electro-optical response properties of the liquid crystalline physical gels basically unchanged. The mechanical properties of liquid crystalline physical gels were affected significantly by the molecular weight of polymers. The energy storage modulus of liquid crystalline physical gels increased from 1.6 × 103 Pa to 3.1 × 104 Pa with increasing molecular weight when the gelator concentration is 6.0 wt%.

Internal friction analysis for the viscoelastic constitutive models

In this paper, the internal friction for the viscoelastic materials such as asphalt is analyzed theoretically. The variation of the strain energy and internal friction per period when an alternating stress is applied to the viscoelastic material is discussed which shows that the storage and release of the strain energy are alternately carried out. The internal friction per period is related to the loss modulus. However, it is independent of the energy storage modulus. In addition, the energy storage modulus, loss modulus, tangent of loss angle and internal friction for four viscoelastic constitutive models, i.e., Maxwell model, Kelvin model, Lessersichi model and Jeffreys model, are calculated from which we know that they are all the functions of frequency. When the frequency is zero, the internal friction for the Kelvin model and Jeffreys model are zero, while the Maxwell model and Lessersichi model are infinity.

Preparation and properties of graphene oxide–carbon fiber/phenolic resin composites

Graphene oxide–carbon fiber/phenolic resin, chemically-reduced graphene oxide–carbon fiber/phenolic resin, and thermally-reduced graphene oxide–carbon fiber/phenolic resin composites were prepared by blending a graphene oxide suspension in an ethanol solution of phenolic resin with carbon fibers, followed by vacuum drying and hot pressing. The effects of the type of graphene oxide on structure, compressive performance and friction properties of the composites were investigated. Results showed that the compressive properties of the composites were greatly improved with a 0.1 mass graphene oxide % loading compared with the pure carbon fiber/phenolic resin composite. The compressive strength and modulus of the thermally-reduced graphene oxide/phenolic resin/carbon fiber composites were increased by 178.9%, 129.5%, respectively, and the highest energy storage modulus of the chemically-reduced graphene oxide/phenolic resin/carbon fiber composite was increased by 75.2% compared with the pure carbon fiber/phenolic resin composite. The glass transition temperatures of all the composites containing graphene oxide decreased. [ New Carbon Materials 2012;27(5):377–84 ]

Graphene coating makes carbon nanotube aerogels superelastic and resistant to fatigue

Lightweight materials that are both highly compressible and resilient under large cyclic strains can be used in a variety of applications. Carbon nanotubes offer a combination of elasticity, mechanical resilience and low density, and these properties have been exploited in nanotube-based foams and aerogels. However, all nanotube-based foams and aerogels developed so far undergo structural collapse or significant plastic deformation with a reduction in compressive strength when they are subjected to cyclic strain. Here, we show that an inelastic aerogel made of single-walled carbon nanotubes can be transformed into a superelastic material by coating it with between one and five layers of graphene nanoplates. The graphene-coated aerogel exhibits no change in mechanical properties after more than 1 × 10(6) compressive cycles, and its original shape can be recovered quickly after compression release. Moreover, the coating does not affect the structural integrity of the nanotubes or the compressibility and porosity of the nanotube network. The coating also increases Young's modulus and energy storage modulus by a factor of ∼6, and the loss modulus by a factor of ∼3. We attribute the superelasticity and complete fatigue resistance to the graphene coating strengthening the existing crosslinking points or 'nodes' in the aerogel.

Nanoindentation testing of SU-8 photoresist mechanical properties

In this work, quasi-static and dynamic tests for the mechanical properties of SU-8 using a nanomechanical triboindenter were performed. Load–displacement data for the indenter as it is driven into and withdrawn from the photoresist patterns are reported. Berkovich-shaped indenter was used in the experimental measurements of the following mechanical properties: reduced elastic modulus, hardness, energy storage modulus and energy loss modulus. The Young’s modulus of the SU-8 photoresist was also determined.