scholarly journals Preparation and Characterization of Composites Materials with Rubber Matrix and with Polyvinyl Chloride Addition (PVC)

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1978
Author(s):  
Dan Dobrotă ◽  
Valentin Petrescu ◽  
Cristinel Sabin Dimulescu ◽  
Mihaela Oleksik
Keyword(s):  
Substantial Reduction ◽  
Accelerated Aging ◽  
Mechanical Tests ◽  
Point Of View ◽  
Rubber Matrix ◽  
The Finite Element Method ◽  
Composites Materials ◽  
Before And After ◽  
Conveyor Belts

An important problem that arises at present refers to the increase in performances in the exploitation of the conveyor belts. Additionally, it is pursued to use some materials, which can be obtained by recycling rubber and PVC waste, in their structure. Thus, the research aimed at creating conveyor belts using materials obtained from the recycling of rubber and PVC waste. Under these conditions, conveyor belts were made that had in their structure two types of rubber and PVC, which was obtained by adding in certain proportions of reclaimed rubber and powder obtained from grinding rubber waste. In order to study the effect of adding PVC on properties, four types of conveyor belts were made, with the structure of rubber, PVC and textile reinforcement. These have been subjected to certain mechanical tests, also being analyzed from the point of view of the behavior of the accelerated aging. The results obtained showed that the addition of PVC lead to a decrease in tensile stress for the strips made, but also an increase in the tensile strain. Additionally, the elasticity tests performed before and after the accelerated aging showed that the presence of PVC in the structure of the conveyor belts determined a substantial reduction of the aging process of the rubber in the conveyor belts. Under these conditions, it has been established that the use of PVC in the structure of rubber matrix conveyor belts is beneficial if conveyor belts are to be produced that are less subject to mechanical stress, but that work in conditions that can cause accelerated aging of materials. An analysis with the finite element method (FEM) of the test samples was also performed.

Surface Characterization of Monolithic Zirconia Following Treatment with Different Polishing Techniques

2020 ◽  
Vol 980 ◽  
pp. 176-186
Author(s):  
Zhen Yu Tang ◽  
Xin Yi Zhao ◽  
Anderson T. Hara
Keyword(s):  
Phase Transformation ◽  
Surface Characterization ◽  
Point Of View ◽  
Xps Analysis ◽  
Diamond Bur ◽  
Before And After ◽  
Monolithic Zirconia ◽  
Polishing Procedures ◽  
Xrd Patterns

The purpose of this study was to evaluate the effects of different polishing techniques on the topographical features and phase transformation of monolithic zirconia. Four brands of zirconia were ground and polished using one of four systems. All zirconia specimens were ground with a fine-grit diamond bur (GB) prior to polishing procedures. The surface roughness and phase transition (XRD) were evaluated, and surface characterizations (SEM and XPS) were performed. The highest roughness was obtained with the Tob system. The strongest diffraction peak in the obtained XRD patterns was at 2θ=30.246°. No monoclinic phase change was found in any group. The XPS analysis showed that the atomic percentages of yttrium in the specimens of Cercon before and after polishing were the highest of any sample. All the polishing systems tested may not adversely affect the phase transformation of monolithic zirconia. The Tob system resulted in the highest roughness. The XPS analysis showed that grinding and polishing had some effects on the properties of zirconia from a microscopic point of view.

Analyse of the Evolution of the Hygrothermal Properties of the Hemp-Based Mortar within the Framework of the Total Weathering Protocol

2022 ◽  
Author(s):  
Dmytro Kosiachevskyi ◽  
Kamilia Abahri ◽  
Anne Daubresse ◽  
Evelyne Prat ◽  
Mohend Chaouche
Keyword(s):  
Thermal Conductivity ◽  
Accelerated Aging ◽  
Total Porosity ◽  
Point Of View ◽  
Environmental Benefits ◽  
Microstructural Characteristics ◽  
Building Insulation ◽  
Buffer Value ◽  
Before And After ◽  
Moisture Buffer Value

The use of bio-based composites for building insulation is interesting from the point of view of hygrothermal performances, economic and environmental benefits. Among different organic fibers for these materials, hemp is interesting because of its huge availability in France. Nevertheless, the broad application of the hemp-based insulation mortars is hampered due to the lack of a database on their durability. This paper consists of a better understanding of the evolution of the hemp-based composite and its hygrothermal properties. The main objectives are, first, to study the evolution of the hemp insulation mortar microstructure and properties under the accelerated aging cycles, and second, to characterize and analyze the interconnection between observed changes. Experimentally, the protocol of accelerated aging inspired by standardized one was proposed, the microstructural characteristics and the hygrothermal properties, as the total porosity, the thermal conductivity, and the moisture buffer value (MBV) before and after the aging cycles was identified. The MBV characterization was performed for both hemp mortar and hemp shives. The obtained results reveal the increase of the hemp mortar porosity and the decrease of the hemp mortar's thermal conductivity. Furthermore, the MBV value of hemp mortar changes slightly, unlike that of the bulk hemp, which is explained by the mineral matrix's influence. These results consist of data for a better forecast on the degradation of the hemp mortar.

scholarly journals Evolution of the physical and physiological quality of soybean seeds during processing

2018 ◽  
Vol 40 (3) ◽  
pp. 313-322 ◽  
Author(s):  
Tana Balesdent Moreano ◽  
Odair José Marques ◽  
Alessandro Lucca Braccini ◽  
Carlos Alberto Scapim ◽  
José de Barros França-Neto ◽  
...  
Keyword(s):  
Soybean Seed ◽  
Accelerated Aging ◽  
Processing Plant ◽  
Soybean Seeds ◽  
Seed Processing ◽  
Before And After ◽  
Processing Line ◽  
Conveyor Belts ◽  
Physiological Quality ◽  
Germination Vigor

Abstract: Seed processing or conditioning is important for improving soybean seed lot quality as it improves the physical characteristics by eliminating inert materials, weed and non-standard seeds and increases physiological quality. The objective of this study was to evaluate the effect of processing on physical and physiological qualities of soybean seed, before and after each equipment and transport system, during processing in a Seed Processing Plant. Samples of six cultivars were obtained during processing while seeds passed through each machine, totaling fifteen sampling sites. The experimental design was entirely randomized, treatments arranged in 15 x 6 factorial scheme, with 10 replications. Characteristics evaluated were germination; vigor by accelerated aging test; tetrazolium test for viability (TZ 1 to 5), vigor (TZ 1 to 3), weathering damage (TZ 3), mechanical damages (TZ 2 to 8), stinkbug damages (TZ 2 to 8) and moisture content. Results showed that processing improves the physiological and physical qualities of soybean seeds and enhances average quality seeds. The equipment and the system of transport (lifts and conveyor belts) used in this study did not cause mechanical damages to the seeds; the mechanical damages were mostly detected in larger seeds and stinkbug damages were found in smaller seeds; and seeds with weathering damage were neither eliminated nor reduced by any processing line.

scholarly journals Physical Characterization of Breast Implants Submitted to High Energy X-Rays

TECCIENCIA ◽  
2019 ◽  
Vol 14 (26) ◽  
pp. 65-71
Author(s):  
Sandra Johana Patiño Leiva ◽  
María Cristina Plazas ◽  
Lisette Barreto
Keyword(s):  
Breast Implants ◽  
High Energy ◽  
Mechanical Tests ◽  
Prosthetic Material ◽  
X Rays ◽  
X Ray ◽  
Before And After ◽  
The Impact ◽  
Radiotherapy Treatment

Based on clinical experience and various studies, it has been found that breast prostheses present failures that are related to a radiotherapy treatment. However, there are currently few studies that analyze the impact of radiotherapy on the material of the prosthesis. Accordingly, the aim of this paper is to characterize the material of silicone breast implants with high cohesiveness. In order to carry out the research a characterization based on mechanical tests, rheology, and spectrophotometry and scanning electron microscopy. This was done with the objective of identifying changes in the prosthesis before and after being irradiated with high energy x-ray photons. To perform the study, 4 breast implants were used. These implants were subjected to the aforementioned tests. The researcher repeated the observation in the second and the third month. Finally, when comparing the results, the mechanical changes are shown in the coating. In the internal material small changes were generated in the elastic and viscous modules. To conclude, effective changes were observed after radiotherapy treatment in the prosthetic material.

scholarly journals Preparation and Characterization of Electrospun PAN/PSA Carbonized Nanofibers: Experiment and Simulation Study

Nanomaterials ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 821 ◽  
Author(s):  
Shixin Jin ◽  
Jiali Yu ◽  
Yuansheng Zheng ◽  
Wen-Yi Wang ◽  
Binjie Xin ◽  
...  
Keyword(s):  
High Temperature ◽  
Electric Field Distribution ◽  
Fiber Diameter ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
The Finite Element Method ◽  
Before And After ◽  
Nanofiber Membranes ◽  
Scanning Electron

In this study, we simulated the electric field distribution of side-by-side electrospinning by using the finite element method (FEM), and studied the effects of spinneret wall thickness, spinning voltage and receiving distance on the distribution of the electrostatic field. The receiving distance was selected as a variable in the experimental, a series of PAN/PSA composite nanofiber membranes were prepared by using a self-made side by side electrospinning device. The membranes were tested by Fourier-transform infrared (FTIR), thermogravimetric analysis (TG), and scanning electron microscope (SEM). The prepared membranes were also treated by high-temperature treatment, and the change of fiber diameter and conductivity of the membrane before and after high-temperature treatment were studied. It was found that the PAN/PSA carbonized nanofibers could achieve a better performance in heat resistance and conductivity at 200 mm receiving distance.

scholarly journals Constructive Optimization of Vulcanization Installations in Order to Improve the Performance of Conveyor Belts

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3607 ◽  
Author(s):  
Dan Dobrota ◽  
Valentin Petrescu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Mechanical Characteristics ◽  
Fem Analysis ◽  
Rubber Matrix ◽  
Special Importance ◽  
The Finite Element Method ◽  
Type Defect ◽  
Conveyor Belts ◽  
Last Stage

Conveyor belts of special importance must have superior mechanical characteristics. The joining by vulcanization of the conveyor belts allows to obtain superior performances, but it has been found that at the vulcanizing joint of the conveyor belts, there is a “bell”-type defect. This type of defect can cause the quick removal of the conveyor belts from use; thus, within this paper, we realized the constructive optimization of vulcanization installations using the finite element method (FEM). Thus, the FEM analysis was performed for the installation used at the present time, which has four spacers for stiffening, moving to the next stage to a stiffening system with seven spacers and, in the last stage, it was proposed to use a stiffening plate. The joined conveyor belts were of type ST 2000, and by the constructive optimization of the vulcanizing press type DSLQ, the bell-type defect was greatly reduced. Also, an analysis of the effects that the constructive optimization of the vulcanization installation has on the resistance to extraction of the metallic insert from the rubber matrix of the costs determined by the proposed constructive modifications, has been performed.

scholarly journals From model to artefact: Versatile characterization of cinnabar, red lead and realgar red paints for rubrics and miniatures

Chemija ◽  
2020 ◽  
Vol 31 (4) ◽  
Author(s):  
Aušra Čiuladienė ◽  
Aivaras Kareiva ◽  
Rimantas Raudonis
Keyword(s):  
Accelerated Aging ◽  
Gum Arabic ◽  
X Ray Diffraction ◽  
X Ray ◽  
Medieval Manuscript ◽  
Analysis Techniques ◽  
Before And After ◽  
Red Lead ◽  
Data Library

This study focuses on the characterization of cinnabar, red lead and realgar paints, since the red colour was very often used for the illuminations and rubrics of medieval manuscript. The commercial pigments (cinnabar (HgS), red lead (Pb3O4), realgar (As4S4)) and binding media (gum Arabic, fish and parchment glue) were used for the preparation of analogous to historical paints. This work is on-going and at this stage, the resulting red paint samples were analysed to create a short data library that could be used to describe the various red paints and their compositions. The obtained paints were characterized before and after accelerated aging using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX), X-ray diffraction (XRD) and thermal (TG/DSC) analysis techniques. These results of versatile characterization are useful to develop red paint guidelines for the storage and how they affect current and future conservation of these objects.

An Electron Microscope Study of Interdiffusion and Compound Formation in Ta-Au Thin Films

1973 ◽  
Vol 31 ◽  
pp. 32-33 ◽  
Author(s):  
T. C. Tisone ◽  
S. Lau
Keyword(s):  
Electron Microscope ◽  
Electron Microscope Study ◽  
Thermally Grown Oxide ◽  
Ion Milling ◽  
Compound Formation ◽  
Technology Application ◽  
Transmission Electron ◽  
Before And After ◽  
Au Thin Films

In a study of the properties of a Ta-Au metallization system for thin film technology application, the interdiffusion between Ta(bcc)-Au, βTa-Au and Ta2M-Au films was studied. Considered here is a discussion of the use of the transmission electron microscope(TEM) in the identification of phases formed and characterization of the film microstructures before and after annealing.The films were deposited by sputtering onto silicon wafers with 5000 Å of thermally grown oxide. The film thicknesses were 2000 Å of Ta and 2000 Å of Au. Samples for TEM observation were prepared by ultrasonically cutting 3mm disks from the wafers. The disks were first chemically etched from the silicon side using a HNO3 :HF(19:5) solution followed by ion milling to perforation of the Au side.

Clinically Meaningful Change

Methodology ◽  
2019 ◽  
Vol 15 (3) ◽  
pp. 97-105
Author(s):  
Rodrigo Ferrer ◽  
Antonio Pardo
Keyword(s):  
Effect Size ◽  
False Negative ◽  
False Negative Rate ◽  
Point Of View ◽  
Skewed Distribution ◽  
Effect Sizes ◽  
False Negatives ◽  
Large Size ◽  
Before And After ◽  
Post Test

Abstract. In a recent paper, Ferrer and Pardo (2014) tested several distribution-based methods designed to assess when test scores obtained before and after an intervention reflect a statistically reliable change. However, we still do not know how these methods perform from the point of view of false negatives. For this purpose, we have simulated change scenarios (different effect sizes in a pre-post-test design) with distributions of different shapes and with different sample sizes. For each simulated scenario, we generated 1,000 samples. In each sample, we recorded the false-negative rate of the five distribution-based methods with the best performance from the point of view of the false positives. Our results have revealed unacceptable rates of false negatives even with effects of very large size, starting from 31.8% in an optimistic scenario (effect size of 2.0 and a normal distribution) to 99.9% in the worst scenario (effect size of 0.2 and a highly skewed distribution). Therefore, our results suggest that the widely used distribution-based methods must be applied with caution in a clinical context, because they need huge effect sizes to detect a true change. However, we made some considerations regarding the effect size and the cut-off points commonly used which allow us to be more precise in our estimates.

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