Dynamic Mechanical Techniques Research Articles

Structural and mechanical anisotropy in plant-based meat analogues

The rising demand for plant-based meat analogues as alternatives to animal products has sparked interest in understanding the complex interplay between their structural and mechanical properties. The ability to manipulate the processing parameters and protein blend composition offers fundamental insights into the texturization process and holds economic and sustainable implications for the food industry. Consequently, the correlation between mechanical and structural properties in meat analogues is crucial for achieving consumer satisfaction and successful market penetration, providing comprehensive insights into the textural properties of meat analogues and their potential to mimic traditional animal produce. Our study delves into the relationship between structural and mechanical anisotropy in meat analogues produced using high moisture extrusion cooking, which involves blending protein, water, and other ingredients, followed by a controlled heating and cooling process to achieve a fibrous texture akin to traditional meat. By employing techniques such as scanning small-angle X-ray scattering, scanning electron microscopy, and mechanical testing we investigate the fibrous structure and its impact on the final texture of meat analogues. We show that textural and structural anisotropy is reflected on the mechanical properties measured using tensile and dynamic mechanical techniques. It is demonstrated that the calculated anisotropy indexes, a measure for the degree of textural and structural anisotropy, increase with increasing protein content. Our findings have significant implications for the understanding and development of plant-based meat analogues with structures that can be tuned to closely resemble the animal meat textures of choice, thereby enabling consumers to transition to more sustainable dietary choices while preserving familiar eating habits.

Nanocomposites of low-density polyethylene and nanocellulose: An alternative route using bleached cellulose nanofibers gel suspension

The production of thermoplastic composites with nanocellulose has proven a great challenge due the tendency to form strong nanocellulose agglomerates during dispersion or when they are dried. In this research, an alternative method for preparing composites based on bleached cellulose nanofibers (CNF) gel suspension and low-density polyethylene (LDPE) using thermokinetic mixing (Drais mixer) is described. This process makes it possible to use cellulose nanofibers in gel suspension (pulp), without the need for prior drying. For that, a masterbatch was first prepared by mixing the CNF in gel suspension (95%wt moisture) with LDPE in a Drais type homogenizer. The masterbatch was then grinded and incorporated into the LDPE matrix at various contents using a co-rotating twin-screw extruder. The produced materials were characterized using thermal, mechanical and dynamic-mechanical techniques. Efficient incorporation of CNF into LDPE was obtained, that is, no traces of moisture or thermal and/or hydrolytic degradation were noticed, and similar mechanical and dynamic-mechanical properties compared to the neat polymer was obtained. The proposed method was found to have a relevant technological aspect with potential application in the cellulose/polymer industry, aiming to overcome the difficulty of working in water media.

Multiscale characterization of antimicrobial poly(vinyl butyral)/titania nanofibrous composites

Titania nanofillers were used to reinforce nanofibers in composite mats produced by electrospinning of poly(vinyl butyral) with two different concentrations of polymers. The titania nanoparticles and titania nanotubes were added into an acetic acid/ethanol solution in different contents of 3 and 1 wt%, respectively. The effect of the processing system on the morphology of the produced fibers was analyzed. The antimicrobial poly(vinyl butyral) composite fibers with titanium dioxide nanoparticles and titanium dioxide nanotubes were produced by single and multineedle electrospinning systems. This study reports fabrication of composite nanofibrous mats with significant mechanical and antimicrobial properties at a high production speed, which is promising for commercial applications (health care, photocatalysis, protective clothing, etc.). The reported result revealed an outstanding correlation between values of elastic modulus derived from nanoindentation and dynamic mechanical techniques. Copyright © 2017 John Wiley & Sons, Ltd.

Influence of cross-linking agents and curing condition on the performance of epoxy coating

Purpose The performance of epoxy coating on metal substrate at low temperature and high humidity application has adverse effect on cure rate, film properties and adhesion. In recent years, several advanced amine cross-linking agents having superior curing ability at low temperature application environment have been introduced. The aim of this paper is to study the properties of epoxy-based coating cured with different cross-linking agents designed for low temperature application at different environmental conditions. Design/methodology/approach Series of cross linking agents such as modified cycloaliphatic amine (H1), polyamine adduct (H2), modified aliphatic ketamine (H3), phenalkamine (H4) and phenalkamide (H5) have been studied to evaluate their performance in epoxy compositions when cured at four environmental conditions, i.e. at ambient and sub-ambient temperatures with 60 and 90 per cent relative humidity, respectively. The effect of curing conditions was investigated by evaluating different physico-mechanical properties. Dynamic mechanical analyser technique was used to determine glass transition temperature (Tg) and cross-link density (ρ) of coatings. Anticorrosive properties of coatings also have been studied by electrochemical impedance spectroscopy. Findings The outcome of this study is expected to generate new insight into the curing behaviour of epoxy coating using different cross-linking agents which are recommended for low temperature application. Optimum physico-mechanical and corrosion resistance properties have been obtained by phenalkamine curing agent at low temperature and high humidity condition. Practical implications This study is an experimental approach to select the better cross-linking agent for low temperature application. Different test conditions were measured for understanding the performance of epoxy coating cured at different environmental condition. Originality/value The understanding reaction mechanism of the epoxy resin with cross-linking agent at different environmental condition is the great challenge and is hardly investigated in the literature. Therefore, in this research, the influence of climatic conditions and type of cross-linking agents on curing behaviour of epoxy-based coating was investigated.

Dynamic and atomic-scale understanding of the twin thickness effect on dislocation nucleation and propagation activities by in situ bending of Ni nanowires

Although their mechanical behavior has been extensively studied, the atomic-scale deformation mechanisms of metallic nanowires (NWs) with growth twins are not completely understood. Using our own atomic-scale and dynamic mechanical testing techniques, bending experiments were conducted on single-crystalline and twin-structural Ni NWs (D=∼40nm) using a high-resolution transmission electron microscope (HRTEM). Atomic-scale and time-resolved dislocation nucleation and propagation activities were captured in situ. A large number of in situ HRTEM observations indicated strong effects from the twin thickness (TT) on dislocation type and glide system. In thick twin lamella (TT>∼12nm) and single-crystalline NWs, the plasticity was controlled by full dislocation nucleation. For NWs with twin thicknesses of ∼9nm<TT<∼12nm, full and partial dislocation nucleation occurred from the free surface, and the dislocations glided on multiple systems and interacted with each other during plastic deformation. For NWs with twin thicknesses of ∼6nm<TT<∼9nm, partial dislocation nucleation from the free surface and the gliding of those dislocations on the plane that intersected the twin boundaries (TBs) were the dominant plasticity events. For the NWs with twin thicknesses of ∼1nm<TT<∼6nm, the plasticity was accommodated by a partial dislocation nucleation process and glide parallel to the TBs. When TT<∼1nm, TB migration and detwinning processes resulting from partial dislocation nucleation and glide adjacent to the TBs were frequently observed.

Ceramic–polymer capacitive sensors for tactile/force awareness in harsh environment robotic applications

The need for force feedback and spatial awareness of contact in harsh environment applications, such as space servicing, has been unsatisfied due to the inability of current sensor technology to resist environmental effects. In this work, capacitive sensors based on a thick film 0:3 connectivity ceramic:polymer composite structure were evaluated for potential use in future operations within robotic end effectors, withstanding temperatures ranging from −80 ° C to 120 ° C and forces up to 350 kPa. A thick film design is utilized to allow for ease of embedding, allowing sensors to be implemented into exciting robotic hardware with minimal intrusion, and protecting sensors from electron bombardment, radiation, and point concentrations from metal-on-metal contact. Taguchi design of experiments allows composition variables including sensor thickness, ceramic composition, ceramic particle size, ceramic volume loading, polymer character, modifier character, and the polymer:modifier ratio to be evaluated simultaneously. Dynamic thermal and mechanical loading techniques were implemented to characterize the composite sensors with in situ electrical acquisition. Individual composition variables were linked to the sensor magnitude, sensitivity, drift, and hysteresis, showing that the sensor response is optimized with a thickness of single microns, 10 vol% loading of nano-particle ceramics, and high molecular weight polymers with a low content of simple architecture modifiers lacking glass or melting temperatures in the working range.

Viscosity, glass transition and activation energy of solid cis-polyisoprene and trans-polyisoprene blends

Blends of cis-polyisoprene (CPI) and trans-polyisoprene (TPI) have been prepared by solution casting to study viscosity, glass transition temperature and activation energy for the glass transition. The viscosity of blends having different weight ratios has been obtained through a single experiment measuring storage and loss modulus using the dynamic mechanical analyser technique. The glass transition temperature is determined through the temperature at which the minimum of temperature derivative curve of viscosity falls. The activation energy of glass transition and fragility index have been obtained by employing the Vogel–Fulchar–Tammann (VFT) equation by assuming non-Arrhenius behaviour of viscosity of polymer blends. Results indicate that both glass transition and activation energy for the glass transition are influenced by composition and crosslink density of the blend.

Study on mechanical and thermal properties of composites of cis‐ and trans‐polyisoprene blends filled with polyaniline

AbstractIn this study, the effect of polyaniline (PANI) as filler has been investigated on the mechanical and thermal properties of blends of cis‐polyisoprene (CPI) and trans‐polyisoprene (TPI) by dynamic mechanical analyzer and transient plane source technique, respectively. The samples blend composites with different concentration of PANI have been prepared by solution casting method and characterized through X‐ray diffraction. Experimental results from mechanical and thermal measurements show that incorporation of PANI in CPI/TPI blends increases glass transition temperature, mechanical properties and thermal properties whereas decreases damping property. This increase in different properties is only upto a certain amount of PANI and over this amount an entirely apposite behavior is observed. This observed behavior of mechanical and thermal properties is explained on the basis of crystallinity and crosslink density. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

The Effect of Woven Structures on the Vibration Characteristics of Glass Fabric/Epoxy Composite Plates

&lt;p class="MsoNormal" style="text-justify: inter-ideograph; margin: 0cm 0cm 0pt; layout-grid-mode: char; text-align: justify; mso-layout-grid-align: none;"&gt;&lt;span style="font-size: 9pt; mso-fareast-language: ZH-CN; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US;" lang="EN-US"&gt;&lt;span style="font-family: Times New Roman;"&gt;We study the effects of woven structures on the dynamic mechanical properties and vibration properties of the fabric composites. Five typical weaving sets including the ordinary plain weaved and the warp interlocked were adopted in fabric processing. The composites plates with the same thickness were prepared by epoxy resin curing, and their fibre volume fractions were examined. Dynamic Mechanical Analyzer (DMA) and vibration test technique were used to reveal the dynamical behaviours of specimens in different frequencies of vibration. The storage modulus, the loss tangent, the natural frequency and damping ratio&lt;span style="mso-spacerun: yes;"&gt; &lt;/span&gt;were obtained. The result showed that the woven structure have a strong effect on the fibre volume fraction, resin-rich area and the warp architectures of the composites, which determines the performances of the composites in vibration.&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;&lt;p class="MsoNormal" style="text-justify: inter-ideograph; margin: 0cm 0cm 0pt; layout-grid-mode: char; text-align: justify; mso-layout-grid-align: none;"&gt;&lt;span style="font-size: 9pt; mso-fareast-language: ZH-CN; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US;" lang="EN-US"&gt;&lt;span style="font-family: Times New Roman;"&gt;&lt;strong&gt;Defence Science Journal, 2011, 61(5), pp.499-504&lt;/strong&gt;&lt;strong&gt;&lt;strong&gt;, DOI:http://dx.doi.org/10.14429/dsj.61.296&lt;/strong&gt;&lt;/strong&gt;&lt;br /&gt;&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;

Vibration characteristics of glass fabric/epoxy composites with different woven structures

We study the effects of woven structures on the vibration properties of the composites. Five typical weaving sets including the ordinary plain weaved and the warp interlocked were adopted in fabric processing. The composites plates with adequate thickness were prepared by epoxy resin curing, and their fiber volume fractions were examined. Dynamic mechanical analyzer and vibration test technique were used to reveal the dynamical behaviors of specimens in different frequencies of vibration. The result showed that the woven structure have a strong effect on the fiber volume fraction, resin-rich area, and the warp architectures of the composites, which determine the performances of the composites in vibration.

Characterization of the interphase in carbon fiber/polymer composites using a nanoscale dynamic mechanical imaging technique

The interphase of fiber reinforced polymer composites is a narrow region around the fiber, and the mechanical performance of a composite strongly depends on the properties of the interphase. The interphase of carbon fiber reinforced polymer composites (CFRPs) is difficult to quantitatively characterize because of its nanometer dimension. To solve this problem, we present a nanomechanical imaging technique for mapping the dynamic mechanical property around the interphase region in CFRPs, and for providing nanoscale information of the interfacial dimension. The experimental results show that this method can determine the width and topography of the interphase with nanoscale lateral resolution, based on the storage modulus profile on the cross section of the composite. The average interphase thicknesses of a T300 carbon fiber/epoxy resin composite and a T700 carbon fiber/bismaleimide resin composite are 118 nm and 163 nm, respectively, and the size of interphase is uneven in width and “river-like”, which is consistent with the surface topography of the carbon fibers. Furthermore, the effect of water-aging on the interphase of the T300/epoxy composite was analyzed using the in situ imaging technique. An increase in the interphase width and interface debonding were revealed, implying a degradation in the interphase region.

Dynamic mechanical behavior of intermetallic Ti 3Sn

Damping and Young’s modulus have been measured in single-phase Ti3Sn using resonant and dynamic mechanical techniques. The compound demonstrates unusual non-linear behavior. Elasticity decreases with strain, but increases with both frequency and temperature (343–673 K); damping is unusually high and decreases with frequency, remains unchanged with strain and shows peaks at 190 and 310 K. Although the mechanisms of energy dissipation are presently unknown, the results suggest the occurrence of a phase transition at about 350 K.

Toughening of an epoxy resin with an isocyanate‐terminated polyether

AbstractA low‐molar‐mass, hydroxyl‐terminated polyether [polypropylene glycol/poly(ethylene glycol) copolymer (POPE)] was functionalized with isocyanate groups and used to improve the impact resistance of a diglycidyl ether of bisphenol A based epoxy resin cured with triethylene tetramine (TETA). The effect of polyether‐based modifiers (with and without NCO groups) on the curing rate of the epoxy/TETA system was investigated with rheological techniques. The NCO‐functionalized polyether reduced the gel time, and this indicated an accelerating effect of the curing process. In addition, a significant improvement in the impact resistance was observed with only a slightly detrimental effect on the stiffness and mechanical strength. Scanning electron microscopy of the corresponding epoxy network revealed a homogeneous morphology with no phase separation. The miscibility of NCO‐modified POPE and the epoxy resin was also confirmed with atomic force microscopy. The glass‐transition temperature of the epoxy networks was also investigated with dynamic mechanical techniques. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Physicochemical and biological evaluation of plasma‐induced graft polymerization of acrylamide onto polydimethylsiloxane

AbstractPolydimethylsiloxane (PDMS) rubbers exhibit good mechanical properties for biomedical and industrial applications, but their inherently high hydrophobicity limits biomedical applications of this material despite its favorable mechanical properties. In this work, surface modification of PDMS by radio‐frequency glow discharge and subsequently graft polymerization of acrylamide was studied. PAAm‐grafted, oxygen plasma‐treated, and control (untreated) PDMS rubbers were characterized using attenuated total reflectance Fourier transform infrared, scanning electron microscopy, dynamic mechanical thermal analyses, zeta potential, and contact angle techniques. Fibroblast (L929) cell attachment and growth onto these surfaces were examined by optical microscopy. The data from in vitro assays showed that cell attachment onto control surface was very negligible while significant cell attachment and growth was observed onto oxygen plasma‐treated and PAAm‐grafted PDMS surfaces. The method developed in this work offers a convenient way of surface modifications of biomaterials to improve attachment of cells onto substrates. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008

Effects of Heating, Tensile, and High Pressure Treatments on Aggregate Structure of a Low Density Polyethylene

The effects of heating, tensile, and high pressure treatments on the aggregate structure of a low density polyethylene (LDPE) are studied via modulated DSC (MDSC) and dynamic mechanical technique (DMA). The results indicate that the nonreversing heat flow can reflect the relative thermodynamic stability for crystalline structure of the polymer, and this makes nonreversing heat flow be a novel useful tool to qualitatively characterize the perfect degree of crystalline structures. During thermal treatment, it is found that there exists a low temperature melting endotherm at about 35°C. It presents an endothermal peak in nonreversing heat flow and a simultaneous glasslike transition in reversing heat flow, which behaves a feature of physical aging far above the glass transition temperature of the polymer. This suggests the existence of so-called “rigid amorphous fraction” (RAF). The structural changes of polyethylene induced by different treating methods are also investigated by DMA, and the relaxation characteristics of macromolecular chains are analyzed.

OBSERVATION OF ENERGY DISSIPATION PEAK IN POLYSTYRENE MELT ABOVE Tg

In this paper two different kinds of dynamic mechanical techniques (inversed torsion pendulum and energy dissipation apparatus) were used to study the dynamic behavior of atactic monodisperse polystyrene above glass transition. The plots of energy dissipation versus temperature were presented for two atactic polystyrene samples. An apparent energy dissipation peak occurred above Tg in each plot measured by the inversed torsion pendulum, and simultaneously the sample was found to flow assuredly at the moment. To exclude the influence of the flow and demonstrate there was a peak indeed above Tg, the energy dissipation apparatus was used, in which the samples were put into a cup. An obvious peak appeared, and it was in agreement with the peak observed by the inversed torsion pendulum. On basis of the results measured by the two kinds of apparatus, a conclusion is drawn that a peak occurrs above Tg, which gives a manifestation for the existence of the liquid-liquid transition.

Stress corrosion cracking in tinplate destined for legume and pet food packaging

Problems associated with stress corrosion of tinplate cans for foodstuffs are occurring at an increasing rate. The appearance of stress corrosion usually entails heavy financial penalties and high risk to the food. Unfortunately, at present, no practical measures exist to counteract this phenomenon. Stress corrosion is a type of localised corrosion which develops by way of the simultaneous action of particular media, which, in the absence of stress, may be only mildly aggressive or even non-aggressive, and a stress which is lower than that required for purely mechanical cracking. The aim of the present work was to study the susceptibility of tinplate to stress corrosion in different test media simulating foodstuffs. To this end, two approaches were used: an electrochemical technique, fast and slow polarisation, and a dynamic–mechanical technique, the slow strain rate test. The results of both tests enabled identification of the environment–material combination most susceptible to this type of corrosion. In particular, it emerged that the most critical environment for the development of stress corrosion is a solution simulating meat products at pH 6, whereas the most sensitive material was found to be tinplate produced from single reduction continuous annealing steel.

Dynamical mechanical behavior of copolymers made of styrene and methyl methacrylate: Random, alternate and diblock copolymers

The dynamics of copolymers made of styrene and methyl methacrylate and of different architecture (three diblock, two random and one alternate) have been studied using a dynamic mechanical spectroscopy technique (DMTA). The scanning calorimetric results indicate that there is only one glass transition except for two of the diblock copolymers. In addition, only one broad mechanical relaxation is observed in all the copolymers studied in this work. However, it has not been possible to build master curves for the complex Young modulus E* for the copolymers. In fact the relaxation spectra calculated from E* are bimodal. In order to describe the relaxation functions of the samples, it has been necessary to use two Kohlraush–Williams–Watts functions at each of the temperatures studied. The relaxation times of the two dynamic contributions can be described by Arrhenius laws, which is probably due to the relatively narrow temperature range for which the relaxation can be studied within the frequency range experimentally accessible. The stretching parameters increase linearly with T, which indicates that both dynamic transitions broaden as T is decreased.

Time-Temperature-Intensity-Transformation Cure Diagram for Visible Light Curable Dimethacrylate Resins

The cure behavior of two dimethacrylate resin formulations activated by visible light (λ = 400-500 nm) was investigated by means of a rapid monitoring dynamic mechanical technique. Storage modulus (G � ) and tan δ vs. time data were obtained for different light intensities (20-600 mW cm −2 ) and cure temperatures (25-60 ◦ C). Gelation and vitrification time were estimated from initial rise of Gand maximum peak of tan δ vs. time curve, respectively, and used to construct time-temperature-intensity-transformation (TTIT) cure diagram. Physical states of material in the regions divided by the estimates of the transforming times were incorporated in the cure diagram. It was found that the dimethacrylate systems undergo phase transformation initially from liquid to rubber and finally to glass. Effects of intensity and temperature on the gelation and vitrification are discussed and compared for the two formulations. Visible light curable dimethacrylate resins are widely used as an important base material for dental restora- tive composites as a consequence of their advantages such as the short application time and the aesthetic performance in clinical applications. However, there remain many issues of the dimethacrylate based den- tal resins. Rapid reaction of the light curing systems leads to incomplete cure, 1-5 reducing the mechanical strength and increasing the swelling of the material. Unreacted monomers trapped in the incompletely cured material could be extractable, causing various troubles in the body. 6-9 Shrinkage during photo-polymerization is also one of principal drawbacks in practical applica- tions. 10, 11

Acousto-optical Characterization of the Viscoelastic Nature of a Nuchal Elastin Tissue Scaffold

A nondestructive, acousto-optical method for characterizing the mechanical loss factor of biological tissues and tissue scaffolds is presented and applied to the characterization of an elastin tissue scaffold derived from bovine nuchal ligament. The method relies on launching guided surface acoustic waves into the tissue scaffold with a small speaker and simultaneously illuminating a small region of the scaffold distant from the speaker with a low-power HeNe laser. The phase lag between the driving acoustic wave and the shift in the backscattered laser speckle pattern is determined as a measure of the mechanical loss factor of the scaffold, tan delta. Measurements of tan delta and elastic modulus were also made by traditional dynamic mechanical loading techniques. Through the central portion of the loading cycle, the elastic modulus of the elastin scaffold was 1.2 x 10(6) +/- 1 x 10(5) N x m(-2) (parallel to fiber orientation). The estimated value of tan delta in the direction parallel to the elastin fibers was 0.03 +/- 0.017 by traditional methods and 0.029 +/- 0.03 when using the acousto-optical method. In the direction perpendicular to fiber orientation, tan delta was measured as 0.14 +/- 0.056 by the acousto-optical method. Because of a lack of mechanical integrity, it was not possible to measure tan delta in the direction perpendicular to fiber orientation by traditional methods. The acousto-optical method may prove to be useful in the mechanical characterization of developing engineered tissues.