Thermomechanical Analysis Method Research Articles

ВЛИЯНИЕ ВЗРЫВНОЙ ОБРАБОТКИ НА СТРУКТУРУ И СВОЙСТВА ВТОРИЧНОГО ФТОРОПЛАСТА-4

This study is dedicated to investigating the influence of explosive treatment on the structure and properties of secondary fluoroplastic-4 (VF-4). Comprehensive research was conducted using microstructural analysis, X-ray structural analysis, and thermomechanical analysis methods. The obtained results are of great significance for the development and improvement of polymer waste recycling technologies.

Cyclic Thermomechanical Analysis of Polyethylene Glycol Based Shape Memory Polymers

Shape memory polymers (SMP’s) are a type of smart material that possess the ability to remember its original shape. Shape memory polymer quickly recovers to its original or permanent shape. As a result of these properties, SMPs can be used as sensors, actuators, and transplants, as well as auxiliary materials in a variety of applications. It has been used in a variety of domains over the previous two decades because to its shape memory capability, and its applications are growing at a quicker rate. Due to its biocompatibility, wide range of tunable stiffness, large deformation, large recovery, high elastic property, water vapour permeability, and multi responsive shape memory effect, memory polymers, polyurethanes are the most adaptable polymeric material. They offer several advantages over other types of shape memory materials, such as shape memory alloys, such as easier manufacturing, lighter weight, lower cost, larger recoverable strain, and lesser toxicity. When compared to shape memory alloys (SMA’s), SMPs have a few disadvantages, such as lower moduli, which results in lower recovery stresses, and longer response times. In some applications, a proper recovery stress derived from the elastic recovery stress created during the deformation process is crucial. There is no literature on how to synthesize SMP’s in an efficient manner. SMP’s and its classification in terms of their distinct qualities. This work focuses on the analysis of cyclic thermomechanical tests of linear SMP’s in order to address some of these problems. Form memory polymers were made using a two-step polymerization process in this study, with the composition of PEG 6000-IPDI-PEG600-BDO as 58wt%-42wt%-1ml-1ml respectively and the shape memory effect was assessed using a bend test. Cyclic thermomechanical analysis method involves tensile test procedure in thermal chamber with intermediate temperatures. Mechanical properties such as cyclic thermomechanical test, dynamic mechanical analysis, and tensile test are used in the validation process. In the primary cycle can be determined as for the sample 10 when we applied the load of 0.8 Mpa the strain was found as 200% the shape fixity and shape recovery values are 98.95 and 97.0 respectively.

Функциональные свойства сегнетоэлектрических материалов на основе цирконата-титаната свинца и триглицинсульфата на макро- и микромасштабе размеров

Samples of ferroelectric functional materials based on lead zirconate titanate with the chemical formula PbTiO3-PbZrO3-PbNb2/3Zn1/3O3-PbNb2/3Mg1/3O3 and triglycine sulfate (NH2CH2COOH)3•H2SO4 were manufactured and characterized. The dielectric spectroscopy and differential scanning calorimetry confirmed the presence of phase transitions in them, and the characteristic transition temperatures were determined. Thermomechanical analysis method has been used to study thermally induced deformations in them, near phase transitions. The shape memory effect (SME) and electrocaloric effect in macro samples were studied. Methods of studying the SME on the microscale of sample sizes have been worked out. The process of formation of microstructures in these materials in the form of «micropillars» («micropillars») by selective ion etching with a focused ion beam is investigated. The process of deformation of «micro-pillars» with a diameter from 120 nm to 1 micron from ferroelectric materials using a microneedle mounted on a Kleidiek nanomanipulator in the vacuum chamber of a two-beam scanning microscope CrossBeam 1540 EsB has been studied.

PTC-thermistors Based on Polymer Composite Material for Use in the Agricultural Sector

The agro-industrial complex plays a key role in the domestic economy and requires improvement and modernization of existing and creation of new technologies. The introduction of intelligent and automated systems and digital methods leads to the need for the development of control systems and sensors that ensure accuracy and operational stability. (Research purpose) The research purpose is in developing the polymer composite materials based on an epoxy oligomeric binder for use as PTC sensors. (Materials and methods). The compositions were mixed according to the calculations of generalized parameters of the structure of a dispersed-filled polymer composite material. The method of thermomechanical analysis was used to study the dependence of electrical resistivity on temperature for samples of composite material based on ED-20 epoxy resin with different filler concentrations. The resistance was measured by multimeter to the contacts of the sample. Copper fabric was used as contacts. (Results and discussion) The article considers the possibility of using the obtained composite materials on the example of the technological process of grain drying, where the temperature of the drying agent can vary in the temperature range from 40-50 to 120-140 degrees Celsius. There is a possibility of «programming» PTC sensors based on polymer composite materials by varying the qualitative and quantitative composition to solve the necessary tasks and the operation of PTC sensors in different temperature ranges. (Conclusions) The developed samples of polymer composite materials have the prospect of application as PTC sensors for various technological processes of agriculture. The developed samples of various compositions are sensitive to the required temperature ranges.

Influence of Cross-Linking Agent Concentration/Beta Radiation Surface Modification on the Micro-Mechanical Properties of Polyamide 6.

This study focuses on the problematic of polyamide 6 containing various concentrations of cross-linking agent that was exposed to electron radiation. It is important to improve the material properties of polymers as much as possible. This endeavor can be realized by numerous methods, one of which is radiation exposure. This study investigates the effect of electron beam radiation in doses ranging from 66 to 132 kGy on the micro-mechanical properties of polymers, specifically polyamide 6 filled with 1, 3 and 5 wt.% of cross-linking agent triallyl isocyanurate (TAIC). The changes in the material brought by the radiation exposure were quantified by measurements of indentation hardness and modulus, which were the main measured micro-mechanical properties. Furthermore, thermo-mechanical analysis (TMA) was chosen to confirm the results of the material cross-linking, while the effect of degradation was investigated by Fourier-transform infrared spectroscopy (FTIR). In pursuit of complete evaluation, the topography of the test subject’s surface was explored by atomic force microscopy (AFM). The optimal concentration/radiation ratio was found in polyamide 6 enriched by 5 wt.% concentration of TAIC, which was irradiated by 132 kGy. Material treated in such a way had its indentation hardness by 33% and indentation modulus improved by 26% in comparison with the untreated material. These results were subsequently confirmed by the TMA and FTIR methods.

Synthesis and characterization of polyurethane–polysiloxane block copolymers modified by α,ω-hydroxyalkyl polysiloxanes with methacrylate side chain

Abstract In order to prepare polyurethane–polysiloxane block copolymers, α,ω-hydroxyalkyl polysiloxanes with methacrylate side chain and α,ω-bis(2-methyl-3-hydroxypropyl)polymethyl(2-methyl-methylpropanoate) siloxanes, were synthesized and characterized in this study. The syntheses process included hydroxyl protection, hydrosilylation, deprotection, and ring-opening equilibrium reactions. The intermediates and target products were characterized by Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance methods. The characterization results showed that each step was successfully carried out in all the cases. Then the waterborne polyurethane–polysiloxane block copolymers were prepared via step-growth polymerization. The properties of the block copolymer films were characterized by thermal gravimetric analysis, differential scanning calorimetry, and dynamic thermomechanical analysis methods in detail. The experimental results showed that the block introduction of hydroxyalkyl polysiloxane could reduce the water absorption of waterborne polyurethane from 62 to 11%, and significantly improve the water resistance of polyurethane. With the introduction of polysiloxane, the tensile strength decreased and the elongation at break increased. At the same time, with the increase of the polysiloxane content, the glass transition temperature of the soft segment decreased to −56.4°C and the thermal decomposition temperature increased to 300°C. The results revealed that the introduction of polysiloxane could effectively improve the comprehensive performance of polyurethane–polysiloxane block copolymer films.

Hybrid Polyurethane Adhesive Sealants with Increased Strength Characteristics

Tests of the physicomechanical characteristics, heat resistance, and temperature range of performance of the developed hybrid silane-functional adhesives sealants Viladex-60 (based on STP-polymers) and Viladex-3105 (based on MS-polymer) have been carried out in comparison with the previously developed Viladex-451 and Viladex-45 sealants and the foreign-produced Betaseal 1125-1F polyurethane sealant. It has been found by the method of thermomechanical analysis that the developed adhesive–sealants differ from the previously developed sealants by an increased modulus of elasticity by 1.5–2 times in the temperature range from 0 to 150°C, and in terms of adhesion, deformation–strength, and thermomechanical characteristics, they are not inferior to the foreign sealants Betaseal 1125-1F designed for gluing glass to automobiles.

In-situ analysis of the effect of CaO/Fe2O3 addition on ash melting and sintering behavior for slagging-type applications

Slagging-type technologies, particularly entrained-flow gasification, have been quickly developed and industrialized due to their inherent advantages. The ashes of many feedstocks are rich in SiO2 and Al2O3. Therefore, a high operating temperature is required, making the process less efficient. The use of pure additives such as limestone does not meet the requirements. In consequence, binary additives of CaO/Fe2O3 are studied to improve the fusibility. The CaO/Fe2O3 ratio is varied in order to optimize cost efficiency and the operation and control of processes. Ash fusion temperatures (AFTs) and X-ray diffraction (XRD) combined with in-situ methods of thermomechanical analysis (TMA) and high-temperature scanning electron microscopy (HT-SEM) are used to explore the effect of CaO/Fe2O3 on ash fusibility. The CaO/Fe2O3 ratio affects the ash fusion behavior due to changes in the mineral phase composition. The AFTs reveal an optimum combination for the joint addition of CaO and Fe2O3 compared to blends with the same amount of one single additive, while sintering is less strongly affected. Based on the in-situ analyses, the blends of ash and additive are categorized into two or three regimes of sintering, swelling, and fusion in the high temperature range. Depending on the applied additive ratio, different regimes of ash fusion are detected, which affect the slag properties.

Formation of Silver-Containing Polymeric Nanocomposites by the Reduction of Ag+ Ions in Polyelectrolyte–Metal Complexes Under the Action of Electric Fields

By the methods of wide-angle X-ray diffraction and small-angle X-ray scattering, we study the specific features of the structural organization of pectin–Ag0–P4VP nanocomposites obtained under the action of constant electric fields. It is shown that, in the process of chemical reduction of Ag+ ions in polyelectrolyte–metal complexes, under the action of electric fields, we observe the formation of nanocomposites with higher contents of metallic silver than in the absence of the field. By the method of thermomechanical analysis, it is demonstrated that these materials have a much higher temperature of vitrification, a lower temperature of transition into the viscous-flow state, and a higher susceptibility to relative deformation.

Fire resistance design method for restrained stainless steel H-section columns under axial compression

Considering the material and geometric nonlinearity of restrained axially-compressed stainless steel H-section columns, this paper investigates their behavioural responses during fire exposure via the coupled thermo-mechanical analysis method and finite element models that were established by using ABAQUS. 7 restrained stainless steel H-section columns under axial compression were tested in the ISO-834 standard fire. A numerical simulation analysis was carried out, and the validity and feasibility of the finite element analysis model was proven by the test results. On this basis, a parameter-influencing analysis was performed to determine the main influencing factors of the fire resistance of a restrained axially-compressed stainless steel H-section column. The result shows that the load ratio n, slenderness ratio λ, axial restraint stiffness ratio βl and rotational restraint stiffness ratio βr are the key factors. Based on existing experimental studies and numerical simulations, an equivalent method of rotational restraint at the ends of a stainless steel column in fire is tentatively presented. A simplified formula, based on the effective length coefficient μθ of restrained axially-compressed stainless steel H-section columns, for calculating the critical temperature is proposed.

Influence of moderately warm and extremely cold climate on properties of basalt plastic armature

Rods of basalt plastic armature (BPA) of a periodic profile with diameters of 6, 8, 10, 16 and 20 mm on the basis of an epoxy matrix were exposed for 30 months on open stands in a moderately warm marine climate of Gelendzhik and 28 months on similar stands in an extremely cold climate of Yakutsk. For initial and exposed BPA samples, changes of mechanical parameters were determined. After the exposure in Yakutsk, an increase of ultimate compression strength by 4–12% is found, depending on the diameter of rods. After the exposure in Gelendzhik, this indicator decreases by 10–17%. Using methods of thermomechanical analysis and dynamic mechanical analysis, linear thermal expansion coefficient and glass transition temperature of epoxy matrix were measured. In an initial state, a transition from a glassy state to a highly elastic one is discovered: an α1-transition at 118 °C and an α2-transition at 149 °C. After climatic action, there were detected a shift of α1-transition to low temperatures and a shift of α2-transition to higher temperatures. Reasons for the change of temperatures of transitions are weakening of a molecular layer and post-curing of the epoxy matrix in a surface layer. These effects are accompanied by an increase of the linear thermal expansion coefficient, moisture diffusion coefficient and maximum moisture saturation after the climatic action on BPA. Fractographic studies discovered presence of pores in a structure of BPA with sizes up to 10–20 μm, a quantity and size of which increase by 20–40% after the climatic action. In general, the studied BPA has high climatic stability and can be used for a long time under the extreme climatic conditions.

Stress Induced Precipitation during Quenching of Aluminium Alloys

Quenching is an important step during age hardening of aluminium alloys. It significantly influences on microstructures, properties, residual stresses and component distortion. Due to high heat transfer, thermal stresses occur in quenched components. I.e., all premature precipitates during undercritical quenching form on condition of mechanical stresses. Opposite, quench sensitivity investigations, e.g. recording of continuous cooling precipitation diagrams, are usually performed in stress-free conditions and may therefore be incomplete. We have developed a new method of thermomechanical analysis and calorimetric reheating to investigate stress induced precipitation during quenching of aluminium alloys. For aluminium alloy 2024, it has been shown for the very first time that mechanical stresses during quenching also influence on quench-induced precipitation reactions.

A Novel Method for Investigation of Entropic Stress in Prestabilization of PAN‐Based Precursor Fibers

ABSTRACTApplying stress in the fiber axis direction during the prestabilization process is the best method to control entropic relaxation. Evaluation of entropic stress is necessary for exact determination of required imposed stress. Accordingly, in this paper three types of special‐grade polyacrylonitrile (PAN) fibers with different physical‐mechanical properties and morphological characteristic are studied. To determine thermal‐induced entropic stresses, we use the thermomechanical analysis method from room temperature to beginning of chemical reactions under certain stresses. It is shown that three thermophysical behaviors including the first return, second return, and sans return occurs under certain stresses during the thermal process. There are distinct temperatures for the first and second return behaviors, in which fibers return to primary length after shrinkage or elongation. These temperatures depend on imposed stress during prestabilization. We found that if no elongation or fiber shrinkage occurs in a specific stress and temperature, it shows that imposed stress is equivalent to thermal entropic stress. Changes in shrinkage as a function of temperature for various external imposed stresses are also observed. According to our findings, the onset of entropic stress strongly depends on the orientation index of the paracrystalline region. The maximum entropic stress occurs in the rubbery flow region in amorphous phases and can be obtained from a derivative of the second‐order polynomial trend line of the entropic stress–temperature diagram.

Structure and Thermomechanical Properties of Systems Based on Epoxy Polymer, Metal Oxides, and Polyaniline

We study the structure and thermomechanical properties of systems based on epoxy polymer, metal oxides, and polyaniline. It is shown that iron oxide in a mixture with polyaniline begins to reveal its crystalline structure in the composite for a fairly low concentration level (1.0 vol.%) unlike aluminum oxide, which does not reveal its structure even for its high contents. The investigations reveal a strong dependence of the microheterogeneous structure of composites on the type of metal atoms in oxides. By the method of thermomechanical analysis, we show that the composites based on the epoxy polymer and a mixture of polyaniline with one of the metal oxides ( Al2O3 or Fe2O3) are characterized by the abnormal expandability (α1 = 25%).

Methods for the Numerical Modelling of the Adhesive Interlayer of Sandwich-Sheets in Case of Coupled Thermo-Mechanical FE-Analysis

Bending of multilayered sheets like lightweight sandwich sheets or fiber reinforced thermoplastics is dominated by the mechanism of interply-slip. FE-analysis is performed to predict defects depending on this mechanism. The shear and damage behavior of the adhesive layer of sandwich sheets can be modeled by cohesive elements in Abaqus. Forming simulation of fiber reinforced thermoplastics requires coupled thermo-mechanical analysis methods due to temperature dependence. For this, alternative modeling strategies for the inner layer of adhesive or polymer matrices will be tested in this paper that are able to transfer heat. The layer will be presented by solid elements with enriched property definitions or viscoplasticity. Furthermore the thickness of the layer will be neglected and replaced by contact formulations or spring elements.

Numerical Simulation of Microstructure Evolution of Hot Forging

The paper focuses on the research of using the coupled thermo mechanical analysis method of rigid viscoplastic finite element and the evolution of dynamic recrystallization to establish the calculation model coupling factors of deformation, heat conduction, dynamic recrystallization in the DEFORM, and on the hot-forging simulation of AISI4140. Through the simulation, it makes a valid prediction of dynamic recrystallization volume fraction and the grain size of recrystallized during the metal hot-forging process.

Investigation of effects of reactive copolymer containing maleic anhydride on thermomechanical properties of ternary blends of poly(methyl metacrylate) (PMMA)

In the present paper, the effects of reactive copolymer containing maleic anhydride on the thermomechanical properties of poly(methyl metacrylate) (PMMA) were investigated. Maleic anhydride–styrene (MA–St) and aniline maleamidic acid–styrene copolymers (AnMAA–St) were used as reactive copolymers. Multicomponent blends such as PMMA/MA–St/AnMAA–St were prepared and thermomechanical characterisation of these blends was performed by thermomechanical analysis method (TMA). The blends were prepared by changes of the weight ratios of MA–St and AnMAA–St copolymers in the blends. PMMA contents in all the blends are fixed at a weight of 75%. Consequently, it is clear that MA–St copolymer can be used for changes of the thermomechanical properties of PMMA.

Effect of sulfur atom substitute with selenium on stability of glassy Ge 20As 14S xSe 52-XI 14 chalcohalides

The paper presents results of the research carried out with the aim of establishing the effect of sulfur atom substitute with selenium on thermal and chemical stability of glasses of the Ge 20As 14S xSe 52-xI 14 type. Chemical stability of glasses was estimated on the basis of their dissolution rate in potassium hydroxide of different concentrations. It was found that the rate of dissolving in KOH solutions increases with the increase of the percentage of sulfur content in the glass. The dissolving rate also depends on concentration of basic solution. It was found that the functional dependence of the rate of their dissolution could be described by an exponential function. Values of the glass transition point, as well as the temperature of the beginning of thermomechanical deformation were determined by the methods of thermomechanical analysis. It was established that characteristic temperatures increase insignificantly as sulfur content increases in investigated system.

Dependence of thermal stability and thermomechanical characteristics of non-crystalline chalcogenides in the Cu-As-Se system on copper content

The paper describes the results of a study of glasses of the type CuxAs50Se50-xfor x=5, 10 and 15 at.% Cu, by the method of thermomechanical analysis. Values of the thermal coefficients of linear expansion in solid (αg) and visco-plastic (αω) phase were determined. On the basis of the results obtained using the mentioned methods it was possible to determine the specific temperature of the beginning of the softening process of the glass (Tg), as well as the temperature of the beginning of the deformation (Tω). It was shown that coefficients of linear expansion decrease with the increase of Cu content. On the other hand, the increase of Cu content caused the increase of the temperatures. The analytical forms of dependence of four physical parameters αg, αω, Tg, Tωas a function of the Cu content were fitted.

UO2및 (U1-yCey)O2소결체의 열팽창 측정 및 평가

The linear thermal expansions of UO₂ and (U 1-y Ce y )O₂ pellet were measured from room temperature to 1400℃ as a function of Ce contents (0, 7.63, 14.84, and 21.68 mol%) by using the TMA(Thermo-Mechanical Analysis) method. From the measured data, the linear thermal expansion rate, the coefficient of linear thermal expansion and density variation with temperature were calculated, and the best-fitted temperature-dependent equations were recommended. It was shown that the rate and coefficient of (U 1-y Ce y )O₂ thermal expansion increased and the density decreased with increasing Ce contents.