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Polystyrene Molecular Weight Determination of Submicron Particles Shell
Abstract
The method of determination of the molecular weight of the polystyrene, which is formed as the shell on the surfaces of submicron aluminum oxide particles is considered in the paper. This method is based on the sedimentation of submicron particles, covered by polymer molecules, in a solvent for polystyrene. It is shown that the average polystyrene molecular weight is 39500±11250 amu, when the polymer shells on the surfaces of submicron particles (Al2O3) are formed by the vapor-phase method.
Supplementary resources (4)
Data
November 2021
Data
October 2021
... That is why this paper uses polymethyl methacrylate as a transparent matrix. Al 2 O 3 submicron particles are originally spheres [9,10,24], and polystyrene coating changes their geometry. Due to this fact electron microscopy makes it possible to see if the coating is present on the particles. ...
... Aluminum oxide particles were modified by application of a polystyrene coating on their surface using vapor phase method, described in [9,10,24]. The main idea behind this method is to generate a two-phase gas flow of Al 2 O 3 particles agglomerates, their dispersion in corona and then mixing of these particles with styrene vapor. ...
... It should be noted that polystyrene in the coating has low molecular mass of approx. 40,000 Da [24]. ...
Agglomeration of distributed particles is the main problem in polymer composites reinforced with such particles. It leads to a decrease in mechanical performance and its poor reproducibility. Thus, development of methods to address the agglomeration of particles is relevant. Evaluation of the size and concentration of agglomerates is required to select a method to address agglomeration. The paper analyzes aluminum oxide particles agglomeration in particles-reinforced polymethyl methacrylate (PMMA) composites. Quantitative parameters of polystyrene-coated aluminum oxide particles agglomerates are obtained for the first time in this article. Unlike uncoated aluminum oxide particles, when coated aluminum oxide particles are used, agglomerates concentration in polymer composites decreases approx. 10 times. It demonstrates that modification of submicron particles by a polymer coating decreases the number of agglomerates in the polymer composite. The use of transmittance and opacity values to estimate particles agglomerates is reasonable in this article. It is shown that the difference in optical performance of specimens reinforced with coated and the original particles is related to the number and average size of agglomerates in the specimens. For example, when the concentration exceeds 0.2%, transmittance values for the specimens reinforced with coated particles are greater than the ones for the specimens reinforced with the original particles.
Synthesized silica nanoparticles (SiO2) were coated with a thin polydopamine (PDA) shell by a modified one-step procedure leading to PDA coated silica nanoparticles (SiO2@PDA). Core-shell (CSNPs) characterization revealed 15 nm thickness of PDA shell surrounding the SiO2 core (~270 nm in diameter). Different weight percentages of CSNPs were employed as filler to enhance the final properties of an aeronautical epoxy resin (RTM6) commonly used as matrix to manufacture structural composites. RTM6/SiO2@PDA nanocomposites were experimentally characterized in terms of thermal stability and mechanical performances to assess the induced effects by the synthesized CSNPs on pristine matrix. Thermal stability was investigated by thermogravimetry and data were modelled by the Doyle model and Kissinger methods. An overall enhancement in thermal stability was achieved and clearly highlighted by modelling results. Dynamic Mechanical Analysis has revealed an improvement in the nanocomposite performances compared to the neat matrix, with an increase in the glassy (+9.5%) and rubbery moduli (+32%) as well as glass transition temperature (+10 °C). Fracture Toughness tests confirmed the positive effect in damage resistance compared to unloaded resin with an impressive variation in critical stress intensity factor (KIC) and critical strain energy (GIC) of about 60% and 138%, respectively, with the highest SiO2@PDA content.
Polymers have become indispensable in many engineering applications because of their attractive properties, including low volumetric mass density and excellent resistance to corrosion. However, polymers typically lack in mechanical, thermal, and electrical properties that may be required for certain engineering applications. Therefore, researchers have been seeking to improve properties by modifying polymers with particulate fillers. In the research presented herein, a numerical modeling framework was employed that is capable of predicting the properties of binary or higher order composites with randomly distributed fillers in a polymer matrix. Specifically, mechanical properties, i.e., elastic modulus, Poisson’s ratio, and thermal expansion coefficient, were herein explored for the case of size-distributed spherical filler particles. The modeling framework, employing stochastic finite element analysis, reduces efforts for assessing material properties compared to experimental work, while increasing the level of accuracy compared to other available approaches, such as analytical methods. Results from the modeling framework are presented and contrasted with findings from experimental works available in the technical literature. Numerical predictions agree well with the non-linear trends observed in the experiments, i.e., elastic modulus predictions are within the experimental data scatter, while numerical data deviate from experimental Poisson’s ratio data for filler volume fractions greater than 0.15. The latter may be the result of morphology changes in specimens at higher filler volume fractions that do not comply with modelling assumptions.
This manuscript provides novel bounds and estimates, for the first time, on size-dependent properties of composites accounting for generalized interfaces in their microstructure, via analytical homogenization verified by computational analysis. We extend both the composite cylinder assemblage and Mori–Tanaka approaches to account for the general interface model. Our proposed strategy does not only determine the overall response of composites, but also it provides information about the local fields for each phase of the medium including the interface. We present a comprehensive study on a broad range of interface parameters, stiffness ratios and sizes. Our analytical solutions are in excellent agreement with the computational results using the finite element method. Based on the observations throughout our investigations, two notions of size-dependent bounds and ultimate bounds on the effective response of composites are introduced which yield a significant insight into the size effects, particularly important for the design of nano-composites.
ABS is an engineering plastic that has butadi-ene part uniformly distributed over the acrylonitrile-styrene matrix. It possesses excellent toughness, good dimensional stability, easy processing ability, chemical resistance, and cheapness. However, it suffers from inherent shortcomings in terms of mechanical strength and vulnerability to environmental conditions. Furthermore, it is non-conducting and easily fretted. Plating on ABS can serve to enhance the strength and structural integrity as well as to improve durability and thermal resistance resulting in metallic properties on the ABS material. ABS is described as the most suitable candidate for plating because it is possible to deposit an adherent metal coating on it by only the use of chemical pretreatment process and without the use of any mechanical abrasion. This article aims to review the history of ABS plastics, properties of ABS, processes and mechanisms of plating, and studies of plating on ABS involving mainly eco-friendly methods of plating by discussing the literature published in recent years. The details of elec-troplating of ABS carried out in the authors' laboratory are also presented.
Flotation of fine mineral particles is one of the major challenges faced by the minerals industries worldwide. Flocculation of these fine particles prior to flotation, to form separate hydrophobic and hydrophilic flocs, is one of the methods to tackle this challenge. In order to gain a better understanding of the properties of hydrophilic polymer flocs for the intended flocculation flotation, this paper reports testwork completed on the formation, breakage, and re-growth of quartz flocs when non-ionic high molecular weight polyacrylamide (PAM) was used as a flocculant under different test conditions in an alkaline environment. Focused beam reflectance measurement (FBRM) particle size analyses, coupled with sedimentation tests and optical microscope observations were performed to monitor the real-time evolution and change of quartz flocs. In addition, adsorption experiments and zeta potential measurements were carried out and used as parameters in the DLVO theory interaction energy estimation. The results of DLVO theory interaction energy estimation, settling experiments and optical microscope observations showed that the quartz particles dispersed well in slurry at pH 9. PAM had a strong flocculation ability to quartz particles, the peak values of floc size were affected by both the stirring rate and PAM concentration. In addition, the degree of floc breakage depended on the increased stirring rate and the shear time. Floc re-growth occurred to different extents according to the breakage durations and PAM dosages.
The results of studies into the influence of the thickness of a polystyrene shell applied to surfaces of dispersed corundum (Al2O3) filler particles on the structure and mechanical properties of the composition of an acrylonitrile butadiene styrene plastic are presented. It is shown that the mechanical properties of the composition depend at least on two factors: the interaction between shell molecules and the polymer matrix, and the ratio of shell thickness to the average size of submicron particles of the filler. The change in the mechanical properties of the composition is explained by the decreasing mobility of polymer macromolecules near the encapsulated filler particles due to the increasing adhesion of macromolecules to the polymer shell. It was shown experimentally that the Martens hardness, elastic modulus, tensile strength, and rupture strain can be changed in some range by varying the thickness of the polymer shell on the surfaces of corundum particles.
The functional properties (aggregation, solubilization, rheological) of a pyrrolidinium surfactant with a hexadecyl hydrocarbon tail and a hydroxyethyl moiety at the nitrogen (N) atom in the presence of polymers (poly(acrylic acid), poly(ethylene glycol) and poly(vinylpyrrolidone)) and hydrotropes (sodium salicylate, sodium benzoate and sodium tosylate) were investigated. It was established that the addition of sodium salicylate to an aqueous solution of a cationic surfactant leads to a sevenfold decrease in the critical micelle concentration and a four-order increase in solution viscosity. It was shown that the formation of mixed polymer–colloidal systems of the pyrrolidinium surfactant with uncharged polymers is expressed very weakly. In the case of poly(acrylic acid), it is determined by the value of its molecular mass: the greatest synergetic effect (the highest aggregating and solubilizing ability) is observed in the presence of a low-molecular-mass poly(acrylic acid).
Composites of polymers and inorganic materials have recently attracted considerable attention as lightweight tough materials. In this study, we examined the structures and fracture paths at the adhesive interfaces between a sulfur-containing rubber compound and brass formed during vulcanization. Samples consisting of brass fillers dispersed in a rubber matrix were subjected to in situ tensile observations using transmission electron microscopy. Upon uniaxial stretching, fracture occurred between the rubber compound and outermost CuxS layers of the adhesive interface. With prolonged vulcanization, the adhesive interface became broader and depletion regions of Cu and Zn appeared inside the particles, indicating sample degradation, owing to outward diffusion of the metal elements into the rubber compound. Fracture of the degraded rubber composite occurred along the depletion regions. These observations demonstrate that the adhesiveness of brass and rubber composites strongly depends on the interfacial structures.
Ever since several formations of polymer-based nanocomposites were reported, research on their modeling, characterization, and computerized analysis methodology has been extensively investigated to become a major academic field of advanced material science and technology. This paper mainly summarizes the multiscale computational analysis methodology for polymer nanocomposites. We also introduce various computational modeling approaches to characterizing the physical behavior of polymer nanocomposites, which are the molecular dynamics approach, and the continuum approach. Based on the various computational analyses, we summarize how the material properties and phenomenological behaviors of polymer nanocomposites were analyzed.
The aggregation characteristics of binary systems based on a novel pyrrolidinium surfactant with the hexadecyl hydrocarbon tail and hydroxyethyl fragment at the nitrogen atom were studied in the presence of polyacrylic acid by a complex of physicochemical methods (tensiometry, conductometry, dynamic light scattering, fluorescence spectroscopy, and spectrophotometry). The formation of surfactant–polyelectrolyte complexes leads to a decrease in the concentration thresholds of aggregation by an order of magnitude to form aggregates ~70 nm in size was established by tensiometry and fluorimetry. The solubilization capacity of the formed mixed aggregates was tested using the Orange OT hydrophobic dye.
The structure and mechanical properties of composites based on an ED-20 epoxy resin, modified with ZnO and ZnO particles untreated or encapsulated in polystyrene, were studied. It is shown that the introduction of polystyrene-encapsulated ZnO submicroparticles into the epoxy resin changed its supramolecular structure in comparison with that of the resin filled with untreated ones. It was established that the presence of shell on the filler particles affected the mechanical properties of the polymer composites — their hardness increased by 22.5% and elastic modulus by 13%.
This paper reviews the fundamentals of fracture mechanics for isotropic materials and discusses its extension to orthotropic materials. This is followed by a discussion of the variety of failure modes observed in composites and a review of the predominant fracture mechanics theories that attempt to predict fracture using semiempirical parameters. The main aim of this paper is to present a survey of the field in its current state and to demonstrate the approach taken by each investigator. The paper concludes with two examples where linear elastic fracture mechanics concepts have been satisfactorily employed for composite materials.
In the work, a computational algorithm for crack opening through surface image processing of loaded materials in fatigue fracture was developed and studied in experiment. In the first part of the paper we analyze model displacement fields to test and verify the proposed procedure and software, and in the second part, we consider experimentally taken images of surface regions with a propagating fatigue crack. It is shown that for experimental study of fatigue fracture, it is appropriate to use two parameters: the average crack opening displacement and the shear strain intensity around the crack tip. Analysis of images containing both a deformation zone and an opening crack reveals a nonlinear dependence of the crack opening displacement on the shear strain intensity and this suggests that the computation domain fails to cover the entire strain localization zone.
The structure of PAN gel fibres spun by the water-thiocyanate method is investigated. It is shown that in identical spinning conditions, the packing density of the structural elements in gel fibres based on poly(AN-co-MA-co-ItA)terpolymer is lower than in gel fibres based on poly(AN-co-MA-co-AMPS). A structural model of PAN gel fibre is composed and substantiated. It is shown that the lower packaging density of the structural elements in PAN gel fibres is responsible for the higher sorption power with respect to different inorganic and organic compounds and higher rate polymer-analog transformations.
The complex formation in the oppositely charged linear and flexible polyelectrolytes: quaternized poly(vinylpyridinium) (QPVP) and poly(sodium styrenesulfonate) (NaPSS) was investigated by static and dynamic light scattering (LS), flow birefringence (FB), and viscometry over a wide range of mixing ratios 0.003 ≤ m ≤ 0.9. NaPPS/QPVP systems in N-methylformamide + 0.01 M KBr generated complexes with fractal geometries. The observed clusters were stable and had average dimensions Rg ≈ Rh ≈ 1000 Å at low and high mixing ratios. As the mixing ratio approached m = 0.4, which corresponds to the gel point, the number and the dimensions of clusters grew to R ≈ 1500−3000 Å with a corresponding increase of the fractal parameter d ≈ 3. According to FB data, the axial ratio of the clusters at the gel point m = 0.4 was p = L/d = 1.07, which supports a model with spherical shape.
Dilute and semi-dilute solution properties of several classes of branched macromolecules are outlined and discussed. The dilute
solution properties are needed for a control of the chemical synthesis. The molecular parameters also determine the overlap
concentration which is an essential quantity for description of the semi-dilute state. This state is represented by a multi-particle,
highly entangled ensemble that exhibits certain similarities to the corresponding bulk systems. Because of the rich versatility
in branching the present contribution made a selection and deals specifically with the two extremes of regularly branched
polymers, on the one hand, and the randomly branched macromolecules on the other. Some properties of hyperbranched chains
are included, whereas the many examples of slight deviations from regularity are mentioned only in passing. The treatment
of the two extremes demonstrates the complexity to be expected in the general case of less organized but non-randomly branched
systems. However, it also discloses certain common features.
A study was conducted to investigate classes, properties, synthesis mechanisms, characterization, and applications of core and shell nanoparticles. It was found that concentric spherical core/shell nanoparticles were the most common where a simple spherical core particle was completely coated by a shell of a different material. Approaches for nanomaterial synthesis were broadly divided into two categories, such as top-down and bottom-up. The top-down approach used traditional workshop or microfabrication methods where externally controlled tools were used to cut, mill, and shape materials into the desired shape and order. A large variety of core/shell nanoparticles were available with a wide range of applications. The classification of all the available core/shell nanoparticles depended on their industrial applications or was based on some other property.
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