Interphase Fraction Research Articles

A model for tensile strength of polymer/carbon nanotubes nanocomposites assuming the percolation of interphase regions

In this paper, a model is developed for tensile strength of polymer/carbon nanotubes nanocomposites (PCNT) assuming the network formation above percolation threshold based on Ouali approach. The reinforcing and networking roles of interphase are also considered in the developed model, because the interphase regions commonly form in polymer nanocomposites. Several equations are established to enable the developed model to predict the strength using the properties of polymer matrix, nanoparticles, and interphase. The suggested model is evaluated using the experimental results of several samples. Also, the logical and average levels of thickness, strength, and percolation threshold of interphase regions are calculated for the reported samples. The developed model shows acceptable agreement with the experimental results of nanocomposites. Additionally, the developed model demonstrates the reasonable effects of the volume fraction and radius of nanoparticles as well as the volume fraction, percolation threshold, thickness and strength of interphase on the strength. All observations validate the predictability of the developed model for tensile strength of PCNT.

Proteomic analysis of cell cycle progression in asynchronous cultures, including mitotic subphases, using PRIMMUS.

The temporal regulation of protein abundance and post-translational modifications is a key feature of cell division. Recently, we analysed gene expression and protein abundance changes during interphase under minimally perturbed conditions (Ly et al., 2014, 2015). Here, we show that by using specific intracellular immunolabelling protocols, FACS separation of interphase and mitotic cells, including mitotic subphases, can be combined with proteomic analysis by mass spectrometry. Using this PRIMMUS (PRoteomic analysis of Intracellular iMMUnolabelled cell Subsets) approach, we now compare protein abundance and phosphorylation changes in interphase and mitotic fractions from asynchronously growing human cells. We identify a set of 115 phosphorylation sites increased during G2, termed 'early risers'. This set includes phosphorylation of S738 on TPX2, which we show is important for TPX2 function and mitotic progression. Further, we use PRIMMUS to provide the first a proteome-wide analysis of protein abundance remodeling between prophase, prometaphase and anaphase.

Elastic properties of particle-reinforced composites containing nonspherical particles of high packing density and interphase: DEM–FEM simulation and micromechanical theory

The physical and morphological properties of particles and interfaces can seriously impact the whole mechanical behavior of particle-reinforced composites. In this work, we devise a robust coupling model of the discrete element method (DEM) and the finite element method (FEM) to numerically investigate the effective elastic moduli of particle-reinforced composites consisting of elliptical particles of high packing density, compliant interfaces and homogeneous matrix. In the numerical model, a novel parametric equation for the topological geometry of an interface that is treated as an interphase model is formulated to realize a compliant (penetrable) layer with a constant finite thickness coated surrounding each elliptical particle. Additionally, a convenient strategy is implemented to cope with periodic boundary conditions containing numerous particles. On the other hand, we also propose a micromechanical theoretical framework to derive the effective elastic properties of such three-phase composites by incorporating the fraction of compliant interfaces that is theoretically computed by using the statistical geometry of composites. It is shown that our numerical and theoretical models lead to the prediction of elastic moduli of particle-reinforced composites with nonspherical particles of high packing density to a reasonable accuracy by comparing with available experimental data. Moreover, utilizing the proposed models, we systematically investigate the influence of the characteristics of particles and interphase such as the high packing density and geometries of elliptical particles, and interphase fraction, thickness and stiffness on the elastic moduli of particle-reinforced composites. We find that these physical characteristics play significant roles in determining the mechanical behavior of composites, suggesting that the properties of such materials can be tailored via proper composites engineering and design.

Development and modification of conventional Ouali model for tensile modulus of polymer/carbon nanotubes nanocomposites assuming the roles of dispersed and networked nanoparticles and surrounding interphases

In this paper, conventional Ouali model for tensile modulus of composites is developed for polymer/carbon nanotubes (CNT) nanocomposites (PCNT) assuming the influences of filler network and dispersed nanoparticles above percolation threshold as well as the interphases between polymer host and nanoparticles which reinforce the nanocomposite and facilitate the networking. The developed model is simplified, because the characteristics of dispersed nanoparticles and surrounding interphase cannot significantly change the modulus of PCNT. The suggested model is compared to the experimentally measured modulus of some samples, which can calculate the percolation threshold of interphase regions and the possessions of interphase and filler network. The suggested model correctly predicts the influences of all parameters on the modulus. Thinner and longer CNT in addition to thicker interphase enhance the volume fraction of interphase which shifts the connectivity of interphase regions to smaller nanoparticle fraction and improves the modulus of PCNT. A very low level of percolation threshold significantly develops the modulus, but its high ranges have not any role. Among the studied parameters, the thickness and modulus of interphase between polymer host and networked nanoparticles play the most important roles in the modulus of PCNT.

Control of crystal morphology and its effect on electromechanical performances of electrostrictive P(VDF-TrFE-CTFE) terpolymer

Interplay of microstructure and electromechanical properties of the poly(vinylidenefluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) terpolymer were studied by tailor-made adjusting crystal fraction via temperature annealing processing. Worm-like crystal nanodomain firstly demonstrated an evolution of the surface morphology upon the increasing temperature annealing treatment, in favor of preferential crystal orientation, known to facilitate the dipoles switching along the external electric field. Apart from the aligned crystal orientation and high coverage of crystal fraction raised by high temperature annealing, the enhancement of interphase fraction of the terpolymer contributes to the high-performance of dielectric property and increases the electric breakdown strength as well. The electromechanical behaviors linking to the microstructure were finally evaluated by a bilaminar unimorph cantilever beam theory. And consequently the figure of merits of electromechanical performance, namely dielectric constant and tensile strength values play a trade-off role in the field-induced strain of the electroactive terpolymer layer, suggesting the microstructure-controlled effects. The tip displacement of bilaminar cantilever beam, serving as an indicator of the actuator performance, consists in the electroactive terpolymer layers and passive foil support. Aiming at obtaining optimum actuator device, specific microstructure of terpolymer membrane was revealed by taking the passive support layers into consideration.

Three-dimensional micromechanical analysis of the CNT waviness influence on the mechanical properties of polymer nanocomposites

The effects of carbon nanotube (CNT) waviness on the elastic characterizations of polymer nanocomposites are investigated using a three-dimensional unit cell-based micromechanical model. The most important advantages of this model are its accuracy, simplicity, and efficiency. Both random and regular CNT arrangements can be included in the modeling. The wavy CNTs are modeled as sinusoidal solid CNT fibers while at any location along the length of CNT, the CNT is considered as transversely isotropic material. The polymer and interphase formed due to non-bonded interaction between a CNT and the polymer are assumed to be homogeneous and isotropic as well. Results show that the effect of CNT waviness is not important for the effective coefficients \(C_{11}\), \(C_{12}\), and \(C_{13}\) of the nanocomposites. CNT waviness plays a critical role in determining the effective coefficients \(C_{22}\), \(C_{23}\), \(C_{33}\), and \(C_{44}\) of the nanocomposites. Also, it is found that the CNT waviness slightly affects the effective values of \(C_{55}\) and \(C_{66}\). The effects of volume fraction of CNT and interphase on the mechanical properties of the nanocomposite are examined. Comparison of the present model results shows very good agreement with other available micromechanical analysis and experiment. As comparing with the finite element method, the present model requires much less computational time for obtaining the effective properties of the nanocomposites. Consequently, the results emphasize that all four important parameters, i.e., CNT behavior and waviness, CNT random arrangement, and interphase contributions, should be precisely included in the modeling to predict a more realistic outcome.

Quantifying the particle size and interphase percolation effects on the elastic performance of semi-crystalline nanocomposites

In this research, the effects of particle size and interphase percolation on the elastic moduli of the polymer nanocomposites were studied by using finite element (FE) analysis. For indicating the limitations of micromechanical models, FE results compared to those of micromechanical model. A mathematical algorithm was developed to calculate the percolated interphases’ radii, assuming the volume fraction of interphase to be equal to the crystallinity ratio of corresponding polymer matrix. A model was suggested to estimate the elastic modulus of interphase region based on the interphase radius, matrix properties and particle–matrix compatibility effect. It was seen that the interphase modulus rises by reducing particle size and increasing particle matrix compatibility. By using the proposed model, finite element analyses were carried out for various crystalline matrices filled by CaCO3 nanoparticles of different sizes. The results suggest that by decreasing the particle size, the elastic moduli of nanocomposites increase significantly. For highly crystalline matrices, percolation of interphases causes an additional stiffening effect, especially for smaller particle sizes.

Challenges for Kenaf Fiber as a Reinforcement: A Review

In order to reduce cost of production and decrease environmental pollution, so many research work has been conducted and still ongoing as to the possibility to use kenaf fiber in high technologies production. Its shows that kenaf fiber have potential reinforced fiber in thermosets and thermoplastics composites. This paper presents the various of challenges to produce kenaf as a reinforcement which mean to identify the limit of kenaf fiber performance after over all of challenging factor. The main factor that touch on interphase, water absorption, chemical treatment and fiber fraction which mean affect the performance of kenaf fiber as a reinforcement are discussed.

The Influence of Nonlinear Matrix on Mechanical Behavior of Polymer Particulate Composite

In this contribution the mechanical behavior of polymer particulate composite is studied. A numerical model is created as three phase continuum when a matrix, particles and an interphase are considered. Size of particles and properties of matrix are determined from experiment. A non-linear behavior of matrix is considered in calculations. The main objective is to estimate mechanical response of particulate composite depending on the change in matrix and interphase properties. The results are evaluated for different volume filler fraction of particles. The finite element commercial code ANSYS is used for calculations. Results indicated that by the change of volume filler fraction and properties of matrix and interphase it can be obtained composite with relatively different properties.

Structural relaxation of polystyrene in nanolayer confinement

The physical aging of polystyrene (PS) confined in a multilayered film arrangement was explored using differential scanning calorimetry (DSC). The multilayered films were produced via multilayer coextrusion and consisted of alternating layers of PS and polycarbonate (PC), with PS layer thicknesses ranging from 50 nm to 500 nm. A 125 μm bulk control film of pure PS was also extruded and studied for comparison. The glass transition temperatures (Tg) of the PS in multilayered films did not appear to be systematically dependent on layer thickness, and Tg values in all PS/PC films were similar to the bulk value of 104 °C. Two approaches were used to investigate the structural relaxation of PS in the layered films. In the first method, PS layers were aged isothermally at 80 °C after annealing above the Tg of PS (135 °C for 15 min) to reset the thermal history and provide a well-defined starting point for aging experiments. Recovered enthalpy data for aged films (calculated from DSC thermograms) showed that the aging rate in the PS layers decreased with decreasing layer thickness. Calculated aging rates were also compared with the fraction of interphase material (which increases significantly with decreasing layer thickness), and the decrease in aging rate for films with thinner layers was found to correlate with an increase in interphase fraction. The elevated Tg of the interphase material (compared to pure PS) was suggested as a possible reason for reduced aging rates in the thin PS layers. In the second method, PS layers were cooled from above their Tg at different rates under confinement by PC layers. After this cooling step was performed, subsequent heating thermograms revealed that the enthalpy recovered upon reheating through the Tg of PS was similar for bulk and nanolayered films.

Effect of surface modification on dielectric and magnetic properties of metal powder/polymer nanocomposites

Metal nanopowder (Co and Fe)/polymer composites, both with and without surface modification by behenic acid, were fabricated and their dielectric and magnetic properties were measured at 1 GHz to study the effect of surface modification on the electromagnetic properties. The relative permittivity and the real part of the permeability of the composites with surface modified powders were higher than those with unmodified powders. Related dielectric losses remained at almost the same level, but magnetic losses were somewhat increased. The increase of relative permittivity could result from the increased volume fraction of interphase with a slightly higher relative permittivity at the particle/polymer interface than that of the bulk polymer. The increase in the real part of the permeability may be caused by suppression of the induced demagnetizing field due to suppression of eddy currents by a better particle distribution and a decrease in effective agglomerate size because of the surface modification.

Relevant Elements of a Maize γ-Zein Domain Involved in Protein Body Biogenesis

The N-terminal proline-rich domain of γ-zein (Zera) plays an important role in protein body (PB) formation not only in the original host (maize seeds) but in a broad spectrum of eukaryotic cells. However, the elements within the Zera sequence that are involved in the biogenesis of PBs have not been clearly identified. Here, we focused on amino acid sequence motifs that could be involved in Zera oligomerization, leading to PB-like structures in Nicotiana benthamiana leaves. By using fusions of Zera with fluorescent proteins, we found that the lack of the repeat region (PPPVHL)(8) of Zera resulted in the secretion of the fusion protein but that this repeat by itself did not form PBs. Although the repeat region containing eight units was the most efficient for Zera self-assembly, shorter repeats of 4-6 units still formed small multimers. Based on site-directed mutagenesis of Zera cysteine residues and analysis of multimer formation, we conclude that the two N-terminal Cys residues of Zera (Cys(7) and Cys(9)) are critical for oligomerization. Immunoelectron microscopy and confocal studies on PB development over time revealed that early, small, Zera-derived oligomers were sequestered in buds along the rough ER and that the mature size of the PBs could be attained by both cross-linking of preformed multimers and the incorporation of new chains of Zera fusions synthesized by active membrane-bound ribosomes. Based on these results and on the behavior of the Zera structure determined by molecular dynamics simulation studies, we propose a model of Zera-induced PB biogenesis.

Analytical Investigation and Comparative Assessment of Interphase Influence on Elastic Behavior of Fiber Reinforced Composites

Interfacial interactions and interphases play a key role in all fiber reinforced composites. However, a clear distinction must be made between interface and interphase. Interphase becomes interface if its thickness decreases to zero. In most of the available micromechanical models the interface is considered perfect (no interphase). However, such a condition is hardly fulfilled in real composites. It is possible to find the volume of interphase by using DSC or identification of interphase region using SEM or some other sophisticated instrument techniques as it is a region created between the two main phase of a composite. All these techniques require special technical skill. In the present study attempt is made to identify the existence of the interphase region in fiber matrix composites using SEM. It was also decided to develop an equation for volume fraction and thickness of interphase by considering the composite as three-phase RVE. Developed equations of interphase volume fraction was used by considering the soft and stiff interphase parameters. Comparisons were made to study elastic behavior of fiber reinforced composites in longitudinal and transverse directions with available experimental data and published model in the literature and they are in good agreement.

Cholesterol Substitution Increases the Structural Heterogeneity of Caveolae

Caveolin-1 binds cholesterol and caveola formation involves caveolin-1 oligomerization and cholesterol association. The role of cholesterol in caveolae has so far been addressed by methods that compromise membrane integrity and abolish caveolar invaginations. To study the importance of sterol specificity for the structure and function of caveolae, we replaced cholesterol in mammalian cells with its immediate precursor desmosterol by inhibiting 24-dehydrocholesterol reductase. Desmosterol could substitute for cholesterol in maintaining cell growth, membrane integrity, and preserving caveolar invaginations. However, in desmosterol cells the affinity of caveolin-1 for sterol and the stability of caveolin oligomers were decreased. Moreover, caveolar invaginations became more heterogeneous in dimensions and in the number of caveolin-1 molecules per caveola. Despite the altered caveolar structure, caveolar ligand uptake was only moderately inhibited. We found that in desmosterol cells, Src kinase phosphorylated Cav1 at Tyr(14) more avidly than in cholesterol cells. Taken the role of Cav1 Tyr(14) phosphorylation in caveolar endocytosis, this may help to preserve caveolar uptake in desmosterol cells. We conclude that a sterol C24 double bond interferes with caveolin-sterol interaction and perturbs caveolar morphology but facilitates Cav1 Src phosphorylation and allows caveolar endocytosis. More generally, substitution of cholesterol by a structurally closely related sterol provides a method to selectively modify membrane protein-sterol affinity, structure and function of cholesterol-dependent domains without compromising membrane integrity.

Evaluation of influence of interphase material parameters on effective material properties of three phase composites

In this paper, evaluation of effective material properties of different types of three phase composites (reinforcement, matrix and in between interphase) using numerical homogenization techniques (representative volume element (RVE) approach) based on finite element method is presented. The influence of interphase parameters like stiffness and volume fraction of interphase on effective material properties of transversely randomly distributed uni-directional fiber composites and randomly distributed spherical particle composites is studied. The RVEs, required for transversely randomly distributed uni-directional fiber composites and randomly distributed spherical particle composites, are generated using a modified random sequential adsorption (RSA) algorithm with periodicity on opposite boundary surfaces. The numerical results are compared with analytical methods like asymptotic homogenization method for regular arrangement of uni-directional fiber composites.

The Effect of Interphase Structures in Nanodielectrics

The interface between the polymer and the filler particles influences the properties of dielectric materials. To understand how interfaces act, they should be considered as layers rather than interfaces. Therefore the term interphase is more appropriate for the polymer layer around a filler particle where the polymer chains are chemically and/or physically bound to the particle surface.The interphase is characterized by an ordered polymer structure around the particles. This paper discusses the influence of the ordered polymer structure around the particles on the polymer properties with regard to explain the effect of nano particles on material properties.In this paper also a model is given how to estimate the maximum interphase fraction depending on particle diameter and interphase thickness. It is postulated that the most significant results can be achieved at this maximum.

Microstructure evolution in pearlitic steels during wire drawing

Major processes affecting microstructure of a drawn pearlitic wire including lamellae thinning, changes in inter-lamellar interface and metallographic and crystallographic texture, plastic flow localization, and dynamic strain aging were characterized. Heavily drawn pearlite represents a nano-composite with thickness of ferrite and cementite lamellae decreasing during wire drawing. Volume fraction of inter-phase interfaces is comparable with that of pearlitic cementite and they are associated with high elastic stresses. Stretching and rotation of pearlite colonies result in their alignment with the wire axis. This is accompanied by increase in a local ductility at the true strain below from 1.5 to 2 and then decrease at higher strain levels. Development of a strong crystallographic texture causes anisotropy in mechanical properties. Targeted observations of plastic flow at the same region showed two systems of localized shear bands and provided information on their development. A dramatic decrease in elongation to failure in wires after drawing is linked to the existence of the localized shear bands. Dynamic strain aging increases strength and degrades ductility of drawn wires.

Isolation of luteolin 7-O-rutinoside and esculetin with potential antioxidant activity from the aerial parts of Artemisia montana.

The antioxidant activity of Artemisia montana was determined by measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and inhibitory activity against free radical generation of hepatocytes (AC2F). The methanol extract of A. montana showed strong radical scavenging activity at a concentration of 10.1 microg/ml, and thus fractionated by solvent extraction. Esculetin and luteolin 7-O-rutinoside (scolymoside) were isolated as the active principles from the EtOAc and Interphase fractions, respectively. The antioxidant activity of these compounds were comparable to that of L-ascorbic acid.

Modulated Differential Scanning Calorimetry Analysis of Interphases in Multi-Component Polymer Materials

A modulated-temperature differential scanning calorimetry (M-TDSC) method for the analysis of interphases in multi-component polymer materials has been developed further. As examples, interphases in a polybutadiene-natural rubber (50:50 by mass) blend, a poly(methyl methacrylate)-poly(vinyl acetate) (50:50 by mass) structured latex film, a polyepichlorohydrinpoly(vinyl acetate) bilayer film, and polystyrene-polyurethane (40:60 by mass) and poly(ethyl methacrylate)-polyurethane (60:40 by mass) interpenetrating polymer networks were investigated. The mass fraction of interphase and its composition can be calculated quantitatively. These interphases do not exhibit clear separate glass transition temperatures, but occur continually between the glass transition temperatures of the constituent polymers.

Induction of diplochromosomes in mammalian cells by inhibitors of topoisomerase II.

Diplochromosomes, consisting of four chromatids lying side-by-side, instead of the normal two, are produced when cells go through two rounds of DNA replication without separation of chromatids. They are thus an indication of the failure of the normal chromosome separation mechanism. In the present experiments, induction of diplochromosomes by inhibitors of topoisomerase II (Topo II) was used to provide further evidence that Topo II is required for separation of daughter chromosomes. Actively growing cultures of CHO cells were treated with Colcemid, and separated into metaphase and interphase fractions, each of which was treated for 2 h with the Topo II inhibitor being tested. The cells were then cultivated in fresh medium without inhibitor for periods of between 18 and 44 h, and metaphase cells once again accumulated by treatment with Colcemid. Chromosome preparations were made in the standard way and stained with Giemsa. Up to 2,000 metaphases were counted from each culture, and the proportion with diplochromosomes calculated. At appropriate concentrations, the Topo II inhibitors etoposide and mitoxantrone induced substantial levels of metaphases with diplochromosomes in cultures that had been treated when the cells were in interphase (up to 30% and 11%, respectively). Amsacrine, however, only produced a smaller proportion (4.7%) of metaphases with diplochromosomes after a much longer culture period following treatment. All the inhibitors caused severe chromosome damage. When used to treat metaphase cells, mitoxantrone and amsacrine only induced diplochromosomes after prolonged culture, although a small number of diplochromosomes were seen after etoposide treatment and a shorter period of culture. Results with cells treated in metaphase might indicate that Topo II is, in fact, not required for anaphase chromosome separation, although it is clearly important for segregation of newly replicated DNA.