Temperature Sweep Research Articles

Emulsions undergoing phase transition: Effect of emulsifier type and concentration

Pickering emulsion stabilized by cellulose nanocrystals (CNCs) during the phase transition of the dispersed oil is poorly understood. We investigated the capability of CNC in stabilizing Pickering emulsions during the temperature-induced phase transition. Paraffin wax emulsions stabilized by sodium dodecyl sulfate (SDS) were less stable than CNC stabilized emulsions. The relationship between droplet size and emulsifier content was examined, and a new model describing this relationship is proposed. The droplet size of CNC-based systems was not affected by temperature variation, even at low CNC concentrations. The minimum CNC content required to stabilize the paraffin wax emulsion was lower than SDS. DSC results indicated that higher droplet surface coverage with emulsifiers enhanced the deformation resistance of the crystallized droplets, which enhanced the emulsion stability. Temperature sweep viscosity measurements showed that the stability of CNC-based systems was not significantly impacted by the phase transition of the paraffin wax. Rheological amplitude sweep analysis indicated that emulsions above the melting point of paraffin wax were more stable at all strain levels. However, the SDS-based systems displayed substantial heterogeneity after the liquid-solid transition. Frequency sweep tests revealed that CNC-stabilized emulsions were more stable than SDS-stabilized emulsions.

Evaluation of the Physical Stability of Starch-Based Hydrogels Produced by High-Pressure Processing (HPP).

Starch-based hydrogels are natural polymeric structures with high potential interest for food, cosmeceutical, and pharmaceutical applications. In this study, the physical stability of starch-based hydrogels produced via high-pressure processing (HPP) was evaluated using conventional and accelerated methods. For this purpose, conventional stability measurements, namely swelling power, water activity, texture, and organoleptic properties, as well as microbiological analysis of rice, corn, wheat, and tapioca starch hydrogels, were determined at different time intervals during storage at 20 °C. Additionally, to assess the stability of these structures, accelerated tests based on temperature sweep tests and oscillatory rheological measurements, as well as temperature cycling tests, were performed. The experimental results demonstrated that the physical stability of starch-based HPP hydrogels was interdependently affected by the microorganisms’ action and starch retrogradation, leading to both organoleptic and texture modifications with marked reductions in swelling stability and firmness. It was concluded that tapioca starch hydrogels showed the lowest stability upon storage due to higher incidence of microbial spoilage. Accelerated tests allowed the good stability of HPP hydrogels to be predicted, evidencing good network strength and the ability to withstand temperature changes. Modifications of the rheological properties of corn, rice, and wheat hydrogels were only observed above 39 °C and at stress values 3 to 10 times higher than those necessary to modify commercial hydrogels. Moreover, structural changes to hydrogels after cycling tests were similar to those observed after 90 days of conventional storage. Data obtained in this work can be utilized to design specific storage conditions and product improvements. Moreover, the accelerated methods used in this study provided useful information, allowing the physical stability of starch-based hydrogels to be predicted.

Mixed-state Hall scaling behavior and vortex phase diagram in FeSe0.7Te0.3 thin films

We investigate the scaling behavior between Hall resistivity (${\ensuremath{\rho}}_{xy}$) and longitudinal resistivity (${\ensuremath{\rho}}_{xx}$) in the mixed state and the vortex phase diagram for ${\mathrm{FeSe}}_{0.7}{\mathrm{Te}}_{0.3}$ (FST) thin films. The ${\ensuremath{\rho}}_{xy}$ and the ${\ensuremath{\rho}}_{xx}$ are simultaneously measured as functions of temperature and magnetic field, and ${\ensuremath{\rho}}_{xy}(H,T)$ is expressed using the power law relation ${\ensuremath{\rho}}_{xy}(H,T)=A{\ensuremath{\rho}}_{xx}^{\ensuremath{\beta}}(H,T)$. Interestingly, FST thin films show a two-slope behavior in the power law relation with different exponent values of ${\ensuremath{\beta}}_{1}$ and ${\ensuremath{\beta}}_{2}$. For the temperature sweep ($T$ sweep) at a fixed magnetic field, ${\ensuremath{\beta}}_{1} (=2.0\ifmmode\pm\else\textpm\fi{}0.16)$ is insensitive to the magnetic field, whereas for the magnetic field sweep ($H$ sweep) at a fixed temperature, the value significantly increases from 1.93 to 3.82 with an increase in temperature. On the other hand, changes in the ${\ensuremath{\beta}}_{2}$ value are relatively small for both cases. Two ${\ensuremath{\beta}}_{1}$ and ${\ensuremath{\beta}}_{2}$ values result in two vortex liquid regimes, which could be ascribed to different pinning strengths within the ${\ensuremath{\beta}}_{1}$ and ${\ensuremath{\beta}}_{2}$ regions. In addition, the tangent of the Hall angle $(\mathrm{tan}{\ensuremath{\theta}}_{\mathrm{H}})$ with respect to the magnetic field exhibits a crossover behavior at the critical field ${H}^{*}$, which coincides with the magnetic field corresponding to the boundary of the ${\ensuremath{\beta}}_{1}$ and ${\ensuremath{\beta}}_{2}$ regimes. These results suggest that various \ensuremath{\beta} values are possible in FST thin films and are closely related to the flux pinning characteristics.

Influence of high content crumb rubber and different preparation methods on properties of asphalt under different aging conditions: Chemical properties, rheological properties, and fatigue performance

Asphalt pavements are prone to aging in construction and during service, which can affect the properties of the asphalt. The aging behaviors of high content crumb rubber modified asphalt (HCRMA) were investigated in this paper. The binders were aged in the laboratory and the performances before and after aging were tested using the attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) test, temperature sweep (TS) test, frequency sweep tests, multiple stress creep recovery (MSCR) test, zero shear viscosity (ZSV) test, bending beam rheometer (BBR) test, and linear amplitude sweep (LAS) test. The FTIR test result shows that as the aging progresses, the crumb rubber (CR) continues to undergo desulphurization and degradation reactions in the HCRMA, with the release of substances such as silica and S-C bonded material from the CR into the bituminous phase. The elasticity of HCRMA decreases and then increases as the degree of aging increases. Besides, the low temperature performance of HCRMA is controlled by the stiffness value, and the low temperature stress relaxation properties of HCRMA in the aging process are better than that of 20% content crumb rubber modified asphalt. Moreover, aging can reduce the integrity and fatigue resistance of HCRMA while increasing the compatibility of HCRMA.

Performance evaluation of hot-applied sealant for asphalt pavement with consideration of the ash content

The hot-applied sealant is widely applied for sealing the cracks of asphalt pavement, in which the filling equipment is always blocked during the installation. The high proportion of ash particles generating the high segregation and low liquidity of sealant is a critical reason for equipment blockage. Therefore, this study aims to explore the influences of ash content on the stability and fluidity of sealant. Six commonly used sealants following the specification requirements were selected in this study. The methodologies involve proposing an ash content test to enhance the calcination efficiency of sealant samples, conducting the segregation and rheological tests including amplitude sweep (AS), temperature sweep (TS) and multiple stress creep recovery (MSCR) tests to evaluate the stability and fluidity of sealants, and utilizing the gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR) tests to acquire the specific chemical properties of sealants. The results indicate that the modified ash content test protocol proposed, calcining the sealant by mixing with the steel balls, is effective for fully calcining. The sealants with high ash content values always exhibit severe segregation and low thermal stability. The complex modulus curves, phase angle curves, black space diagrams, Han curves, and non-recoverable creep compliance (Jnr) values derived from the rheological tests present that the ash particles lead to poor stability and high elasticity of sealants. Furthermore, the FTIR tests imply that the S1 sealant was modified with most additives among six sealants, while the GPC tests point that the ash particles are not related to the molecular size of sealants. Moreover, it is recommended that the ash content index should be included in the existing evaluation system after the weak correlations with other indexes were discovered.

Effect of montmorillonite modification on resistance to thermal oxidation aging of asphalt binder

Asphalt binder aging can cause various pavement diseases including cracking, stripping and pothole formation, which reduce the service life of asphalt pavements. Therefore, asphalt binder modification is regarded as an economical and effective method to improve its antiaging properties. In this paper, the Montmorillonite (MMT) modified asphalt binder with the additive amount of 2, 4, and 6 wt% were prepared. Rolling thin-film oven test (RTFOT) and pressure aging vessel (PAV) procedures were carried out respectively to simulate thermal oxidation aging in both short and long terms. Temperature sweep tests using a dynamic shear rheometer (DSR), Fourier transform infrared spectroscopy (FTIR), and atomic force microscopy (AFM) were performed on base and MMT-modified asphalt binders at different aging conditions. Antiaging behaviors were evaluated through the basic physical and rheological indexes, and FTIR and AFM indicators. The antiaging sensitivity and mechanism were also analysed. The results showed that 4 wt% MMT modified asphalt binder exhibits excellent antiaging properties.

Effects of tetraethyl orthosilicate on rheological behaviors of crumb rubber modified asphalt

The purpose of this work is to study the rheology, fatigue properties and physical changes of crumb rubber modified asphalt (CRMA) after pretreatment of rubber crumbs with tetraethyl orthosilicate (TEOS). Six weight ratios of TEOS to crumb rubber, 0%, 15%, 20%, 25%, 35%, and 50%, were chosen to prepare modified crumb rubber (CR) and use it to prepare CRMA. The effects of TEOS on the physical properties of CRMA were analyzed through softening point, penetration and ductility tests. Mechanical tests including multiple stress creep and recovery (MSCR) test, temperature sweep test, and linear amplitude sweep (LAS) test were conducted to evaluate rheological properties and fatigue resistance. The results show that TEOS addition can effectively improve the physical properties, rheological properties and high temperature stability of CRMA. However, the excessive addition of TEOS can decrease rheological properties and fatigue life of rubber-modified asphalt. The results of temperature scanning test and MSCR test show that CRMA has the best G* and δ under the condition that TEOS content is 25% of CR mass; and it has optimal non-recoverable creep compliance (J(nr)) and percentage of recovery (R%). LAS test results indicate that CRMA has better fatigue life when TEOS content is 25% of CR.

A Strong and Rigid Coordination Adaptable Network that Can Be Reprocessed and Recycled at Mild Conditions

A Strong and Rigid Coordination Adaptable Network that Can Be Reprocessed and Recycled at Mild Conditions

High-temperature rheological properties of waterborne epoxy asphalt emulsion mastic

In this study, Portland cement and limestone dust were added as mineral filler to anionic and cationic waterborne epoxy asphalt emulsion (WEA), respectively, and four types of waterborne epoxy asphalt emulsion mastics were prepared. A filler-WEA (F/WEA) ratio of each WEA mastic refers to the weight ratio of filler and WEA, ranging from 0.3 to 1.2 at 0.3 increments. Four WEA mastics with different F/WEA ratios were subjected to temperature sweep test, frequency sweep test, and multiple stress creep and recovery test by using a dynamic shear rheometer, and the rheological parameters (e.g., Superpave rutting parameter, non- recoverable creep compliance) were obtained. The results show that WEA-cement mastics, especially anionic mastics, had excellent high-temperature deformation resistance due to the existence of waterborne epoxy-cured products and cement hydration products in the mastics system. In contrast, non-chemical interaction between limestone dust and WEA resulted in a slight improvement in the high-temperature performance of WEA-limestone mastics. In addition, the rheological parameters of four WEA mastics all exhibited significant correlations with F/WEA ratio. The F/WEA ratio had more effect on the rheological properties of WEA-limestone mastics than that of WEA-cement mastics.

Rheological behaviors of asphalt binders reinforced by various fibers

Incorporating different fibers contributes to improving the properties of asphalt materials. In this study, chopped basalt fibers (CBFs), flocculent basalt fibers (FBFs), lignin fibers (LFs), and polyester fibers (PFs) were mixed into SBS modified asphalt at four contents (1%, 2%, 3%, and 4% by weight of SBS modified asphalt) to prepare fiber-reinforced asphalt (FRA) samples for dynamic shear rheology (DSR) tests, including temperature sweep, multiple stress creep recovery (MSCR), and linear amplitude sweep (LAS) tests. The microscopic characteristics of the incorporated fibers and those of the remnants of FRAs after screening out the fibers were also determined using scanning electron microscopy (SEM) and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR). The results demonstrated that the rheological behavior of FRA varied significantly with the type of fiber incorporated. Generally, the deformation recovery ability and anti-fatigue ability of SBS modified asphalt were improved by adding different fibers. With an increase in the fiber content, fiber network structures were gradually formed in the bundle fibers, including CBFs- and PFs-reinforced asphalt, resulting in an increase in the viscosity and high-temperature stability of FRA. Comparatively, flocculent fibers such as LFs and FBFs presented better improvements in terms of the elasticity, deformation recovery, and fatigue life (Nf) of FRA. The approximate characteristic peaks and values indicate that no chemical reactions were found between the fibers and the SBS modified asphalt. Property analysis revealed that the recommended content was 2%, 3%, 4%, and 4% for CBFs, PFs, LFs, and FBFs, respectively.

Interactions between RAP and virgin asphalt binders in field, plant, and lab mixes

Reclaimed asphalt pavement (RAP) has been used in asphalt mixes for several years in the United States. However, the interactions between the RAP binder and the virgin asphalt binder (VAB) need further investigations. Thus, the main objective of this study was to explore the rheological and chemical properties of extracted asphalt binders (EABs) from plant, field, and lab mixes. The plant mixes were collected from behind the paver, reheated to the compaction temperature, and compacted in the lab. The field mixes were collected as cores within two weeks after the end of the construction process. The lab mixes were fabricated in the lab using the same materials used in the plant and field mixes. The mixes contained high asphalt binder replacement percentages by RAP, which were greater than 30%. The EABs were treated as rolling thin film oven aged VABs (RTFO AVABs). The rheological properties of EABs and RTFO AVABs were analyzed using temperature sweep, frequency sweep, and multiple stress creep recovery tests. Chemical investigations of EABs and RTFO AVABs were carried out using Fourier transform infrared spectroscopy and thermogravimetric analysis. The EABs from plant or lab mixes showed higher stiffnesses than EABs from field mixes. This occurred because of the extra heating that was implemented for the plant mixes before the compaction in the lab, which caused more interactions between the RAP binder and VABs. The fabrication mechanism, mixing and short-term aging processes, used in lab mixes caused more interactions between RAP binder and VABs than in the field mixes.

Effect of low-frequency alternating magnetic field on the rheological properties, water distribution and microstructure of low-salt pork batters

The effects of different intensities of low-frequency alternating magnetic fields (LF-AMF) modification on gel characteristics, rheology, water distribution, secondary structure and microstructure were investigated. The results showed that application of LF-AMF exhibited a significant improvement of the water-holding capacity, gel strength, color, textural properties and acceptability of low-salt pork batter gels (P < 0.05). When the LF-AMF intensity reached 0.6 mT, the low-salt pork batters had the highest WHC, L*, gel strength, hardness, springiness, gumminess and chewiness and acceptability (P < 0.05). During the temperature (sample heated from 20 to 80 °C) and frequency (0–10 Hz) sweep, the storage modulus G′ first increased and then decreased with increasing of LF-AMF intensity. Low-field nuclear magnetic resonance (LF-NMR) showed that LF-AMF at an intensity of 0.6 mT shortened the T2 relaxation time of pork batter gel and increased the proportion of immobilized water. Fourier transform infrared spectroscopy (FTIR) showed that LF-AMF treatment significantly induced an increase of β-sheet structure and reduction of α-helix content in pork batter gels (P < 0.05). Scanning electron microscopy (SEM) results suggested that LF-AMF contributed to the formation of pork batter gels with a more uniform and orderly network structure.

Characterization of asphalt binders extracted from field mixtures containing RAP and/or RAS

The use of reclaimed asphalt pavement (RAP) and/or recycled asphalt shingles (RAS) in the asphalt mixtures is a common practice in the U.S.A. However, there is a controversy to date on how RAP/RAS interact with virgin asphalt binders (VABs) in asphalt mixtures. For mixtures containing RAP/RAS, the aged asphalt binders in RAP and air-blown asphalt binders in RAS alter the performances of the extracted asphalt binders (EABs). Thus, the rheological properties of EABs from these mixtures require more investigation. The focus of this paper was relating the high-temperature properties of EABs from field cores to the corresponding rolling thin film oven aged virgin asphalt binders (RTFO AVABs). Furthermore, a comparison of the effect of RAP and RAS on the high-temperature rheological properties of EABs was another objective. Different asphalt cores were collected from the field within two weeks after the pavement construction process in 2016. These cores represented eight asphalt mixtures with different asphalt binder replacement percentages by RAP, RAS, or both. The asphalt binders were extracted from these mixtures and considered as RTFO AVABs. The high-temperature rheological properties included the temperature sweep and frequency sweep testing and the multiple stress creep recovery testing. The EABs had higher stiffnesses and elasticates than the corresponding RTFO AVABs because of the aged binders in RAP/RAS. The binders in RAP interacted more readily with VABs than RAS binders.

Effects of waterborne polyurethane on storage stability, rheological properties, and VOCs emission of crumb rubber modified asphalt

Crumb rubber modified asphalt (CRMA) has been put forward and become a research hotspot due to the environmental pressure and the actual demand for road engineering. However, worrying issues such as poorer storage stability and more serious VOCs emissions have emerged one after another. In this work, waterborne polyurethane (WPU) was employed as the shell material to package the crumb rubber (CR) to prepare a porous composite modifier (CM) by solvent volatilization. The effects of WPU on storage stability, rheological properties, and VOCs release of CRMA were investigated. The experimental results indicate that the asphalt with CM as a modifier (CMMA) has better high temperatures storage stability than traditional CRMA. The temperature sweep experiment designates that CM can improve the high temperatures performance of the asphalt binder by increasing the rutting factor (G*/sin δ) and complex modulus (G*), but the fatigue performance is slightly weakened. The direct tensile tests (DTT) demonstrate that the fracture energy of CMMA is slightly lower than that of CRMA but still 2.3 times that of virgin asphalt. Moreover, GC-MS test results prove that the VOCs emission of CMMA is extremely lower than that of CRMA and virgin asphalt. The nitrogen adsorption test of CM and CM's SEM images suggest that the inhibition mechanism of VOCs by CM might be the synergistic effect of adsorption and shielding. The conclusions of this study can provide a new method of cleaner production with a lower carbon footprint for building materials such as asphalt.

Thermal storage stability and rheological properties of multi-component styrene-butadiene-styrene composite modified bitumen

It has been reported that a novel multi-component styrene-butadienestyrene composite (SBSC) modifier composed of the SBS as the main content and additional components including ethyl-vinyl-acetate (EVA), maleic anhydride grafted with ethyl-vinyl-acetate (MAH-g-EVA), naphthenic oil, and antioxidant can be produced by melt blending. This SBSC modifier can be directly mixed with bitumen and aggregate to prepare bitumen mixture, thus thoroughly addressing inferior thermal storage stability of SBS-modified bitumen. However, it is necessary to explore the efficient utilization of the SBSC modifier due to its inadequate engineering application and poor dispersion when the SBSC modifier was added directly to the bitumen mixture. The objective of this research was to investigate the feasibility of using the SBSC modifier to obtain modified bitumen with acceptable thermal storage stability and other enhanced properties. Modified bitumens (SBSC-modified bitumens with 3, 4, 5, 6, 7 % SBSC modifier content, SBS-modified bitumen with 4.5 % SBS modifier content as the control sample) were prepared. The thermal storage stability of modified bitumen was investigated by the segregation test. Besides, the basic physical properties of modified bitumen were tested, including penetration, softening point, and ductility. The rheological properties were evaluated by temperature sweep test, multiple stress creep recovery (MSCR) test, rotational viscosity (RV) test and bending beam rheometer (BBR) test, respectively. Meanwhile, fluorescence microscopy and Fourier transform infrared (FTIR) spectrometer were also applied to characterize the microproperties of the modified bitumen. Results show that the difference in softening point of SBSC-modified bitumens with modifier contents ranging from 3 % to 7 % is less than 2.5 °C after 72 h of high temperature storage at 163 °C. The softening point and ductility of SBSC-modified bitumen increase considerably with the addition of the SBSC modifier but the decrements of penetration are not significant. Besides, with the increasing addition of the SBSC modifier, complex modulus, average percent recovery, and viscosity of modified bitumen all improve. Meanwhile, phase angle, non-recoverable creep compliance of modified bitumen decrease. The flexural creep stiffness also decreases with the increasing content of the SBS modifier. When the SBS content is the same, the SBSC-modified bitumen gets better thermal storage stability, high and low temperature properties than the SBS-modified bitumen. The microproperties show that the SBSC modifier can be uniformly dispersed in base bitumen and physically mixed with the base bitumen. The SBSC-modified bitumen obtains preferable thermal storage stability. The high and low temperature properties of the bitumen are also enhanced by the addition of the SBSC modifier. Meanwhile, the melt blending method does not restrict the role of the additional components in the SBSC modifier to improve the performance of bitumen. Based on the above findings, it can be considered that the use of SBSC modifier to prepare modified bitumen with enhanced performance is a promising practice. This research may shed light on the application of SBSC modifier to bitumen pavements.

Spectrally-resolved ultraviolet absorption measurements of shock-heated NO from 2000 K to 6000 K for the development of a two-color rotational temperature diagnostic

In high-enthalpy air flows, nitric oxide (NO) formation and removal involves multiple, complex energy transfer processes that occur under nonequilibrium conditions, thus motivating the need for diagnostic methods to probe such flows in laboratory settings. In this work, a rotational temperature diagnostic for NO was developed using a spectroscopic model (Stanford NO model) of the γ-bands of NO to inform optimal wavelength candidates for absorption using two continuous-wave (CW), ultraviolet (UV) lasers. Absorption cross-sections of shock-heated NO were measured with two CW UV lasers over a range of temperatures and wavelengths, and results were compared to the Stanford NO model. All measurements were completed behind reflected shocks in 0.4% and 2% mixtures of NO in argon (Ar). Fixed-wavelength cross-section measurements from 2000 K to 6000 K between 1 atm to 0.085 atm were made at nominal wavelengths of 226.1026 nm and 224.8155 nm. Additionally, fixed-temperature measurements were made over the wavelength range 226.1013 nm to 226.1035 nm at 0.8 atm. The combination of experiments provided temperature and wavelength sweep cross-sections to compare against the Stanford NO model. The formulation for the collisional broadening parameter, 2γ, was divided into two temperature regimes, transitioning at 2500 K. Additionally, line positions of the R11(26.5), R12(34.5), Q21(26.5), and Q22(34.5) transitions around 224.8155 nm and the Q11(12.5), R12(19.5), P21(12.5), and Q22(19.5) transitions around 226.1026 nm were adjusted to best fit the cross-section data. A vibrational equilibrium assumption was used to determine the translational and vibrational temperatures at the point of cross-section determination, while a coupled vibration-dissociation (CVDV) model characterized the extent of dissociation at the point of cross-section determination. Data from both temperature-sweep and wavelength-sweep measurements agree to within ± 10% of the Stanford NO model, with most cross-sections falling within ± 5% of model predictions. Oxygen (O2) cross-sections measurements were also taken behind reflected shocks in dilute 2% O2 in Ar mixtures at 2000 K and 6000 K to quantify the interfering O2 absorbance at the chosen diagnostic wavelengths.

How hydrocolloids can control the viscoelastic properties of acid-swollen collagen pastes

The interactions between proteins and polysaccharides are of considerable importance in the food industry. In this study, the effect of adding non-charged methylcellulose (MC), hydroxypropylmethylcellulose (HPMC), medium (GM) and high (GH) molecular weight guar gum and negatively charged sodium carboxymethylcellulose (CMC) was investigated on the rheological and thermal properties of acid-swollen collagen pastes, as a function of collagen concentration. Dynamic frequency sweeps showed that the addition of the hydrocolloids, except for CMC, increased the storage modulus (G′) and loss modulus (G″) of collagen pastes at all collagen levels investigated. MC, HPMC, GH, and GM increased the collagen pastes' storage modulus to a similar extent. In contrast, the values of the loss moduli were found to be markedly different for each hydrocolloid. The loss factor (tan δ) showed that incorporating the hydrocolloids made the pastes less elastic than pure collagen pastes. The phase transition temperature of collagen measured during the temperature sweep tests was not affected by MC, HPMC, GH, and GM. However, CMC shifted the transition temperature of collagen to higher temperatures. Micro Differential scanning calorimeter (microDSC) results showed that the presence of MC, HPMC, and guar gums did not affect the denaturation temperature (Td) and enthalpy (ΔH). In contrast, the addition of CMC increased the denaturation temperature and denaturation enthalpy of collagen pastes. By fixing the hydrocolloids' viscosifying power and changing the collagen concentration, collagen pastes with different hydrocolloids show different viscoelastic properties.

Dynamic mechanical behaviour of graphene, hexagonal boron nitride reinforced carbon-kevlar, hybrid fabric-based epoxy nanocomposites

An emphasis on the development of lightweight structures in multitudes of engineering applications has broadened the scope for the continual development of fiber-reinforced composites due to their lightweight and superior strength. The current work is aimed to investigate the influence of fillers graphene and hexagonal boron nitride (h-BN) on carbon, Kevlar, and hybrid fabric when they form fiber-reinforced composites. In particular, the properties such as storage modulus, loss modulus, damping factor, and glass transition temperature were determined for various composites to understand the influence of fillers, fabric combinations, and their interaction in synergy. The unique contribution of this work also lies in the inter-correlation of Full width-half Maximum (FWHM) of loss modulus (E”) plots to understand the phenomena of abrasive wear. An inhomogeneity factor based on the Cole-Cole plots termed as circularity index was also calculated by using Full Maximum (F.M.) and the FWHM. Carbon, Kevlar, and hybrid fabric mat reinforced epoxy composites, with 0.1, 0.3 &amp; 0.5 wt% loadings of graphene and h-BN were prepared using the hand layup technique. The Dynamic mechanical analysis (DMA) was performed under temperature sweep (30–200°C). The results were analysed to understand the choice of h-BN with Kevlar fabric for applications needing high damping while graphene with carbon fabric for applications needing high tenacity. A hybrid fabric mat offers a balance of damping and tenacity. It was observed that the GC2 composite showed a 49% increment in storage modulus (E’), and GK2 composites showed a 38% increment in loss modulus (E”) compared to GC0 and GK0 composites.

An investigation into the viscoelastic response of chemically and physically crosslinked minimally invasive hydrogel scaffolds

We report development of injectable hydrogels as scaffolds for bone tissue regeneration. An integrated approach has been used to develop the bone scaffolds using nanocellulose (NC), synthesized from agricultural biomass, and poly(vinyl alcohol) (PVA). PVA based hydrogel was formed using physical crosslinking process involving multiple freeze–thaw cycles, while, NC based hydrogel was developed using chemical crosslinking mechanism in which epichlorohydrin was used as a crosslinker. Investigation of micro-structural surface topology was carried out using scanning electron microscopy which indicated favourable environment for cell adhesion. The viscoelastic response characterized using frequency, amplitude and temperature sweeps, demonstrated that within the experimental range, dynamic storage modulus (G’) was considerably higher than dynamic loss modulus (G’’) for all the hydrogel samples, indicating the formation of well-developed network and in turn structural integrity and dynamic stability of the injectable hydrogel scaffolds. Further, the injectable hydrogels demonstrated excellent injectability and self-standing behavior.

Comparisons of predictive ability of THAI in situ combustion process models with pre-defined fuel against that having fuel deposited based on Arrhenius kinetics parameters

Toe-to-heel air injection (THAI) is an in situ thermal-enhanced oil upgrading and recovery technology that makes use of a horizontal producer well for mobilised partially upgraded oil production to the surface. To design operation of the THAI process requires up-scaling lab-scale numerical model to field-scale reservoir numerical model. There are a number of up-scaling methods that were developed. However, these previous up-scaling methods only concentrated on the qualitative nature of the physicochemical processes. Furthermore, these methods have deficiencies ranging from assumption of 100% oxygen utilisation, failing to compare oil production rates for up-scaled reservoir models with and without fuel pre-defined, not reporting on the dynamics inside the reservoirs with and without fuel pre-defined, etc. As a result, this work provided in depth comparative studies of both the qualitative and quantitative physicochemical processes in numerical models containing Arrhenius-based coke deposition thermal cracking reaction (i.e. model A) and that having pre-defined fuel concentration (i.e. model F) as an initial parameter respectively. It is found that oil production started earlier in model A compared to in model F even though they have approximately similar trajectories. It is shown that by the end of the combustion period, oil recovery of 28.5% OOIP is achieved in model F which is greater than that in model A by an additional of 4.8% OOIP. It is found that the peak temperature, which indicates how healthy the combustion is at a single point only at different times, is generally considerably higher in model A than that in model F. It is further discovered that in some cases the combustion at all points might be stable and rigorous but in other cases the combustion might not be stable and rigorous at all points thereby implying that the peak temperature alone does not give the measure of the efficiency and spread of the combustion front. It is shown for the first time that pre-defining fuel concentration throughout the reservoir as is done in model F resulted in faster downward advancement and expansion of the combustion front compared to in the reservoir where the fuel is deposited based on the Arrhenius kinetics parameters (i.e. like in model A). It is also discovered that higher areal sweep of the reservoir is achieved in model F when compared to that achieved in model A. Overall, it then follows that higher volume of the reservoir of model F is combustion-swept, heat-affected, and oil-depleted compared to that in model A. These findings explain the reason why more oil is produced during the combustion period in model F than in model A. Conclusively, this first-of-a-kind study shows that pre-defining the fuel has no effect on the qualitative nature of the physicochemical processes, but has considerable influence on the quantitative parameters such as the rate of and cumulative oil production, peak temperature, areal and volumetric sweeps by the combustion zone, size of the oil-depleted zone, and size of the heat-affect zone. • Full analysis of predictive ability of THAI model F with pre-defined fuel is reported. • Model F predicted unrealistic high oil production rate & thus cumulative oil recovery. • Model F has faster downward-advancement & general expansion of the combustion fronts. • Higher reservoir volume is combustion-swept, heat-affected, & oil-depleted in model F. • Qualitative behaviours in model F are similar to those in the Arrhenius-based model A.