Rheological Properties Of Materials Research Articles

Comprehensive Characterization of Polymeric Composites Reinforced with Silica Microparticles Using Leftover Materials of Fused Filament Fabrication 3D Printing.

Silica exhibits properties such that its addition into polymeric materials can result in an enhanced overall quality and improved characteristics and as a result silica has been widely used as a filler material for improving the rheological properties of polymeric materials. The usage of polymers in three-dimensional printing technology has grown exponentially, which has increased the amount of waste produced during this process. Several polymers, such as polypropylene (PP), polyvinyl alcohol (PVA), polylactic acid (PLA), and nylon, are applied in this emerging technology. In this study, the effect of the addition of silica as a filler on the mechanical, thermal, and bulk density properties of the composites prepared from the aforementioned polymeric waste was studied. In addition, the morphology of the composite materials was characterized via scanning electron microscopy. The composite samples were prepared with various silica concentrations using a twin extruder followed by hot compression. Generally, the addition of silica increased the tensile strength of the polymers. For instance, the tensile strength of PVA with 5 wt% filler increased by 76 MPa, whereas those of PP and PLA with 10 wt% filler increased by 7.15 and 121.03 MPa, respectively. The crystallinity of the prepared composite samples ranged from 14% to 35%, which is expected in a composite system. Morphological analysis revealed the random dispersion of silica particles and agglomerate formation at high silica concentrations. The bulk density of the samples decreased with increased amount of filler addition. The addition of silica influenced the changes in the characteristics of the polymeric materials. Furthermore, the properties presented in this study can be used to further study the engineering design, transportation, and production processes, promoting the recycling and reuse of such waste in the same technology with the desired properties.

Predicting the extrudability of complex food materials during 3D printing based on image analysis and gray-box data-driven modelling

Material extrudability is a prerequisite for printing 3D structures with extrusion-based food printing. Food materials with different shear-thinning behaviors were printed to develop predictive models for extrudability. A dataset of 131 unique combinations of materials and printing parameters was collected. Image analysis was employed to rapidly quantify extrudability as determined by mode width, line height and width consistency of line filaments. The relation between the printing pressure and the volumetric flow rate followed a power-law relation, which characterizes the extent of shear-thinning of the food materials. Both regression and classification models were trained and tested using the random forest algorithm. The model performance indicated that extrudability can be predicted with moderate to high accuracy by using rheological measurements and printing parameters as inputs. The predictive workflow developed in this study provides a framework to quantitatively assess and predict extrudability for 3D printing of complex food materials. Industrial relevanceExtrusion-based 3D printing has been applied to customize food designs and can potentially enable personalized nutrition. To achieve this, we need to be able to effectively print complex food materials with high accuracy. Variations in composition and rheological properties of complex food materials make achieving proper extrudability not trivial at this moment, and this limits their applicability to extrusion-based food printing. Here, we developed an image analysis tool to measure line filament extrusion of complex food materials that vary in shear-thinning behaviors. We then built predictive models to estimate material extrudability based on material's shear-thinning properties and printing parameters. Data-driven prediction of material's extrudability can help avoid excessive trial-and error experiments in future.

Preparation and Rheological Properties of Amide-based Multiwalled Carbon Nanotube Mirabilite Phase Change Materials

The multi-walled carbon nanotubes (MWCNTs) are modified by redox methods, and the surface groups of the MWCNTs are analyzed by infrared spectroscopy. And the modified MWCNTs were added to the mirabilite-based phase change materials (PCMs) at 40°C to prepare the mirabilite-based phase change composite material. The results show that when the volume fraction is 0.05% and 0.25%, when the temperature rises from 30°C to 50°C, the viscosity drop of the phase change composite material is 35.86% and 37.50%, respectively. That is, the larger the volume of the fraction of nanoparticles, the higher the viscosity, thus the greater the ability to perceive temperature fluctuations. In addition, the amide multiwalled carbon nanotube mirabilite PCMs was placed for 30 days, and the dispersion stability was good, and no phase delamination occurred.

Regulation of Rheological Properties of Three-Phase Dispersed Systems Used for the Production of Building Materials

The paper considers the relationship of the rheological properties of three-phase dispersed systems with capillary coupling and, on this basis, substantiates the possibility of directional regulation of the rheological properties of raw materials for the production of building materials. It is shown that the rheological properties of two-phase dispersed systems are determined mainly by the action of intermolecular forces in the liquid-filled contact zones of solid phase particles, and in three-phase systems – by the action of capillary coupling forces.

Mechanical and Rheological Properties of Flowable Resin Composites Modified with Low Addition of Hydrophilic and Hydrophobic TiO2 Nanoparticles

The aim of this work was to find the influence of the addition of low amount of hydrophilic and hydrophobic TiO2 nanoparticles on compressive strength, microhardness and rheological properties of flowable dental composite material. Specimens were prepared by adding 0.05; 0.2 and 1 wt. % of hydrophilic and hydrophobic 20 nm TiO2 nanoparticles. These specimens were compared to non-modified control specimens in compressive strength and microhardness. Furthermore, their rheological properties were determined. The optimal nanoparticle loading was 0.2 % hydrophobic TiO2, resulting in significantly higher compressive strength and microhardness than those of the control specimen group. Mechanical properties of flowable composites reinforced with hydrophilic and hydrophobic TiO2 at higher loadings are lower than those of control specimens, which is the result of nanoparticle agglomeration. TiO2 nanoparticles addition resulted in the decrease in viscosity in all specimens except for the specimewn with 1% hydrophilic TiO2 nanoparticles. In accordance to the obtained results, hydrophobic nanoparticle addition results in a more resistant and durable material, combined with an increased flowability compared to a non-modified composite.

SUBSTANTIATION OF APPLICATION FEATURES OF LIQUID MIXTURES FOR SCREENING OF ELECTROMAGNETIC FIELDS

The protective and rheological properties of composite materials based on water-dispersed paint and iron ore concentrate were studied. Features of liquid mixtures application for shielding of magnetic field of industrial frequency and electromagnetic field of ultrahigh frequency were substantiated. The study of the protective characteristics and rheological properties of composite materials based on water-dispersed paint and iron ore concentrate indicates the possibility of their use for shielding electromagnetic fields of a wide frequency range. It was found that the efficiency of the composite material (total shielding coefficient and reflection coefficient of electromagnetic waves) depends on the dispersion of the shielding filler, so the particle size analysis of iron ore concentrate was performed. The analysis shows that the predominant size of iron-containing particles is 23‒24 μm, which is quite acceptable for their uniform distribution in the body of the matrix. Shielding protective material was made of water-dispersion paint with the addition of iron ore concentrate in weight quantities of 15, 30, 45, 60%. The shielding coefficients of the electromagnetic field of industrial frequency and ultrahigh frequency with different filler content were measured. It was found that if the concentration of filler exceeds 30%, both the rheological characteristics of the mixture and the shielding coefficients of electromagnetic fields are unsatisfactory. A dramatic increase in shielding coefficients occurs at a filler concentration of 40%. This mixture has acceptable adhesive properties. It was established that the shielding coefficients could be enhanced if the dispersion of the filler is increased, which will contribute to the stability of the colloidal mixture and improve the rheological properties.

Capillary‐bridge forces between solid particles: Insights from lattice Boltzmann simulations

AbstractLiquid capillary‐bridge formation between solid particles has a critical influence on the rheological properties of granular materials and, in particular, on the efficiency of fluidized bed reactors. The available analytical and semi‐analytical methods have inherent limitations, and often do not cover important aspects, like the presence of non‐axisymmetric bridges. Here, we conduct numerical simulations of the capillary bridge formation between equally and unequally sized solid particles using the lattice Boltzmann method, and provide an assessment of the accuracy of different families of analytical models. We find that some of the models taken into account are shown to perform better than others. However, all of them fail to predict the capillary force for contact angles larger than π/2, where a repulsive capillary force attempts to push the solid particle outward to minimize the surface energy, especially at a small separation distance. We then apply the most suitable model to study the impact of capillary interactions on particle clustering using a coupled lattice Boltzmann and Discrete Element method.

METHOD OF EXPRESS DIAGNOSTICS OF FISHSEMI-FINISHED PRODUCTS

Background. The main aspects of quality assessment of fish raw materials and combi ovens for its heat treatment are considered. The results of connection researches of structural and mechanical properties of raw materials with its thermophysical charac­teristics and parameters of necessary culinary processing are presented. The expediency of using physical methods for assessing the quality of raw materials to predict the mode of heat treatment is determined. The aim of the study is to develop a system of rapid diagnostics of structural-mecha­nical and thermophysical properties of fish semi-finished products for the insti­tutions of the HoReCa industry. Materials and methods. The object of research is the structural-mechanical and thermophysical properties of grass carp and their changes during storage. The subject of research – culinary semi-finished products, specifically – grass carp steaks. Determination of structural and mechanical properties of steaks was carried out by a measuring sensor of original design, developed on the basis of components of ITM LLC. The heating kinetics of grass carp semi-finished products were performed in a PolEco cabinet at a temperature of 180 ºC and forced convection. The temperature in the samples was recorded by standard thermal sensors of the UMCD with a measure­ment period of 20 seconds. The amount of active electricity, consumed for the preparation of steaks, was determined excluding the reactive component, by using current measuring clamp. Culinary processing of steaks was in the steam convection oven Convotherm OEB 6.10. Results. A set of structural and mechanical properties of grass carp steaks with different shelf life was determined with a sensor of the original design of UMCD. The correlation of changes in the indicators of adhesion, penetration and relaxation force after compression with the shelf life of steaks was established. A correlation between the shelf life and the heating speed of the samples was established with a standard thermo sensors of UMCD. The heating speed of the samples after 24 h of storage increases by 10–11 %. By recording the current in the power cable of the combi steamer, the electricity consumption for cooking 12 portions of steaks (2400 g) was determined. The possibility of saving electricity from 4.6 % for cooking freshly asleep fish and up to 16.5 % for chilled fish stored for 24 hours was established. Conclusion. The measuring sensor was tested. It allows determining the rela­xation, strength and adhesion of fish raw materials in the express mode. It was found that the structural-mechanical and thermophysical properties of grass carp change with storage time. It is experimentally confirmed that the change of information parameters of heat treatment in the steam convection oven is a criterion of quality of culinary products from freshwater fish. The developed method of express diagnostics allows determining the rheological properties of raw materials from freshwater fish and optimizing the heat treatment of culinary products in restaurants in terms of differential quality of raw materials. Due to the selection of individual processing modes for fish raw materials of different consistency and shelf life, it is possible to reduce electricity consumption by the steam convection oven by 4.6–22.4 %.

Polymer composite materials with electrically conductive and antistatic properties

The influence of special brands of carbon black and carbon single-wall nanotubes on the electrophysical, physico-mechanical and rheological properties of a PE-based polymer composite material is investigated.

Effect of acoustic excitation on fiber-reinforced polypropylene and the influence on melt viscosity

The paper describes a novel technological approach to influencing the rheological properties of thermoplastic materials exposed to acoustic energy. The flow behavior of polypropylene with different mass percentages of glass fibers is investigated in a parallel plate rheometer under high-frequency longitudinal excitation. The influence of oscillation frequency on the melt viscosity is explained by means of shear thinning criteria. The dependence of the oscillation shape using sinusoidal excitation on shear thinning as a function of different fiber reinforcement percentages is also investigated. A phenomenological view describes the mutually influencing parameters with regard to different material compositions and different excitation frequencies over the time course of the rheometric measurement. Interacting relationships are analyzed and discussed and the potential of the actuator system to influence the plastic melt is worked out. Based on this, a technological approach follows which describes the transfer of an oscillating mold surface to plastics processing methods, which, especially in the case of energy-intensive injection molding technology, leads to the expectation of possible resource efficiency in energy and material.

Effect of Different Activators on Rheological and Strength Properties of Fly Ash-Based Filling Cementitious Materials

In this paper, lime, gypsum, NaOH, and Na2SO4 are mainly used to study the activation degree and activation mechanism of fly ash, and L9 (34) orthogonal table is used for the orthogonal test. The influence of different activators on the rheological and strength properties of slurry was analyzed. The microstructure and hydration products of fly ash cement cementitious body were studied by SEM and XRD. The results show that the bleeding rate of slurry containing activator fly ash system is between 2.24% and 3.37%, which is much higher than that of pure cement slurry (9.25%). Therefore, the addition of this system can improve the fluidity of slurry, and the optimal scheme is a3b2c2d2. The results show that the compressive strength of cement with activator fly ash system is much lower than that of pure cement, but the increase of strength is between 31% and 85%, which is much greater than that of pure cement (35%–46%). The optimal scheme is A2B2C3D3 or A3B2C3D3 at 3 days and A1B3C2D3 at 28 days. According to the scanning results of SEM and XRD, the addition of activator can significantly improve the hydration degree of fly ash and form a more complex network structure without obvious gap.

Determining the role of the method used to recycle polypropylene waste materials from automotive industry using sepiolite and zeolite fillers

In this work, the effectiveness of a rapid recycling method of waste polypropylene (WPP) with the addition of inorganic fillers was investigated. The experiments were performed using three types of WPP and a mixture of them (MWPP), characterized by different amount of talc content. The influence of sepiolite (micrometric size) and zeolite (nanometric size) fillers addition on newly prepared materials was analysed by X-ray diffraction analysis (XRD) and scanning electron microscopy (FE-SEM). Mechanical characterizations of all the filled compounds were also performed. The data indicate that the addition of low percentage (5%) of sepiolite or LTA zeolite improves some mechanical and rheological properties of WPP-recycled materials. However, the results also show that the simple mixing of wastes and additional fillers (without preparing pellets) has an influence on the recycling process.

Investigation of additive incorporation on rheological, microstructural and mechanical properties of 3D printable alkali-activated materials

This study investigates the addition of Poly-vinyl Alcohol (PVA) fibres and attapulgite nanoclay to alkali-activated materials (AAMs) with the aim of enhancing the mechanical performance and optimizing the printability and buildability of AAMs. The fresh properties of six mix formulations, including flowability, slump values, rheology, shape retention, and extrusion window, were evaluated. The best performing mixes, that exhibited optimal fresh properties, were 3D printed, and their mechanical performance, microstructure, and buildability were investigated. The addition of 1 wt.-% attapulgite nanoclay (i.e. A-1) showed the desirable fresh properties required for 3D printing, as well as providing sufficient mechanical reinforcement to the samples. The 3D printed A-1 samples showed an improved flexural and compressive strength by 43% and 20%, respectively, compared to both the casted and printed control mixes. Moreover, microstructure analysis, including SEM, Rapidair measurement, and micro-CT, provided evidence of the compatibility by showing the lowest pores anisotropy and mixture homogeneity, between attapulgite and AAMs.

Application of Physical Methods for the Detection of a Thermally Degraded Recycled Material in Plastic Parts Made of Polypropylene Copolymer.

The paper deals with the possibility of applying physical methods to detect a thermally degraded recycled material in plastic parts made of polypropylene. Standard methods of evaluating the mechanical properties of the material under static tensile and bending stress, as well as under dynamic impact stress using the Charpy method, were used for the experimental measurements. The rheological properties of materials were monitored using a method involving measuring the melt flow index, while their thermal properties and oxidative stability were monitored using differential scanning calorimetry. Based on the methods used, it can be clearly stated that the most suitable technique for detecting thermally degraded recycled material in polypropylene is the method involving establishing the melt flow index. The bending test seems to be the most suitable method for detecting recycled material by measuring the material’s mechanical properties. Similarly to the melt volume flow rate (MVR) method, it was possible to unambiguously detect the presence of even a small amount of recycled material in the whole from measuring the material’s bending properties. It is clear from the results that in the short term, there may be no change in the useful properties of the parts, but in the long term the presence of degraded recycled material will have adverse consequences on their lifespan.

Melt Rheology of Renewable Polymers and of New Materials Based on them as Tool in Controlling the 3D/4D Printability

The article presents results regarding the use of the melt flow index method (MFIM) in estimating the rheological properties of polylactic acid (PLA) and PLA-based materials, as tool in the selection of the operating conditions at their shaping into filaments and for 3D printing with thus obtained filaments. Based on the MFIM, the molecular weight of various PLA grade commonly used in melt processing techniques, including printing, were qualitatively compared. It was found that PLA for printing has the lowest molecular weight as compared with the PLA melt processed through injection, extrusion, thermoforming. It has been also shown that the MFIM can be used to verify the efficiency of drying, pre-treatment always needed to be done, before filaments obtaining and/or printing, especially in case of renewable polyesters. By simulating the printing at the indexer, via depositing successive layers, one over the other, it was possible to estimate the optimal flow conditions that ensure a good adhesion between the deposited layers. The estimation of the condition which ensure the needed adhesion between the deposited layers with the help of the MFIM was verified with good results on a grade of high loaded PLA achieved according to an original formulation.

Yield stress measurement for earth-based building materials: the weighted plunger test

Earth-based building material processing is a challenge for new constructions. Moreover, field measurements to obtain the rheological properties of fresh materials are required in building applications. However, existing field-oriented tests were designed for more flowable materials, and new protocols for stiff materials are rarely available. In this paper, a field-oriented test of yield stress is developed for earth-based building materials accurate enough to identify small variations for demanding applications. The squeeze test is used as the reference measurement of yield stress. For pure clays and two clay-based materials, yield stresses could not be easily linked to two existing tests: the Atterberg limits and the falling plunger. Finally, a weighted plunger test was used to measure the yield stress as accurately as the squeeze test. The development of yield stress measurements for fresh earthen materials will help implement new building techniques on the field.

Nanostructures management technology to reduce the fire risk in the oil and gas industry: Performance, features and implementation

Oil and gas enterprises are characterized by an increased fire risk. There is high probability of occurrence and spread of large fires when oil production and processing, transportation and storage of oil products occurs. There is high probability of large fires during the oil production, oil processing and during the transportation and storage of petroleum products. New materials created using nanotechnology principles are needed to improve the efficiency of fire prevention and extinguishing systems. The technology for controlling the properties and performance characteristics of nanofluids based on liquid hydrocarbons and water is based on the methods of functionalization and interaction of clusters of the base liquid and multilayer carbon nanotubes, methods for stabilizing nanofluids, for changing the thermophysical, rheological and electrostatic properties of substances and materials on their basis. The proposed technology makes it possible to create nanomaterials based on various scenarios for the development of emergency situations and to apply them to reduce fire risk at oil and gas facilities.

FEM simulation of C45 steel and Cu-ETP billet shaping at hot upsetting between convex conical dies

On the basis of finite element analysis (FEA), geometric differences in the shaping during hot upsetting of cylindrical billets with a height-to-diameter ratio of 1.0 and 2.0 made of C45 (1.0503) steel and copper (Cu-ETP) between pointed convex conical dies with a cone slant angle of 12.5°, 15.0° and 17.5° are considered. The stroke velocity of the upper die is 0.5 m/s; process temperature (t) and accepted surface friction coefficient (|μ): for steel - t = 1100 °C, μ = 0.32, for copper - t = 850 °C, μ = 0.34. An equation is obtained for the relation between values of reduction in height ratio and engineering strain on height of workpiece during upsetting between conical dies, taking into account the initial billet dimensions and unevenness of forming due to the geometry of tool. The presence of qualitative and quantitative differences in shaping along the height of upset steel and copper billets was revealed, i.e. influence on unevenness of forming the rheological properties of materials under process conditions. It is advisable to use the results obtained to design and improve of technological processes of open die and closed die forging with preforming of billets.

CLASS OF PLANE PROBLEMS ON THE EFFECT OF MOVING LOADS UNDER A NONLINEAR LAW

The present work is devoted to the dynamics stability study of wave processes of plane and circular elements, and it is also being considered a class of plane tasks about moving loads effect on the surface of a layered elastic half-plane under the nonlinear law of stress versus deformation. While studying the wave processes of planar and circular elements in deformable bodies, the concept of phase velocity is introduced as the rate of phase medium change. In the case of harmonic vibrations of a cylindrical shell, the phase speed is expressed through the frequency of natural oscillations of freely supported along the edges of the shell, and therefore, the investigation of waves in plane and circular elements has the most direct relation to the problem of determining the own forms and vibration frequencies of finite length shells. If the studies are carried out taking into account the material rheological properties of considered system, there is a surrounding system environment, also generally displaying rheological properties, the use of these methods is considerably difficult. In such cases, the influence of rheological parameters on the components of the complex phase velocity is studied in definite values of the vibration frequencies. At present article, it is being considered an approximate solution of the nonlinear task about the effect of a moving load on an elastic layer lying on an undeformable base under the nonlinear stress law of depending strains from deformations.

Water-absorbing materials based on polymer hydrogel and bentonite

The article deals with the production, sorption and rheological properties of composite materials based on polymer hydrogel and bentonite. It is shown that bentonite prevents the collapse of the hydrogel in aqueous solutions of electrolytes and leads to an increase in the moisture content after the collapse. After several repeated cycles of swelling in water, followed by drying at 60 and 110 °C, the degree of swelling of the composite is higher than that of the hydrogel. In the temperature range from 20 to 40 °C, the polymer hydrogel and the composite are able to withstand at least ten cycles of swelling and drying without changing the degree of swelling.