Dynamic Mechanical Analysis Method Research Articles

A comparative study on the rheological, thermal, and mechanical performance of epoxy resin modified with thermoplastics

Thermoplastics and functional polymers are commonly used modifiers for epoxy (EP) resin. In this study, an EP system was fabricated and modified with methyl methacrylate block copolymer (BMG), polyphenylene oxide (PPO) and polysulfone (PSF). This was carried out to study the influence of thermoplastic polymers and functional polymers on the properties of EP resins, and the performance of the different modified EP systems was studied and compared. The curing reaction, rheological performances, heat resistance, and mechanical properties of the EP blends were investigated. Curing process of EP resin was determined as 110 °C for 1 h and 150 °C for 3 h by using non-isothermal differential scanning calorimetry (DSC) method. The rheological test revealed that the EP/BMG and EP/PPO blends exhibited low viscosity and wide processing window compared to the EP/PSF blend, thereby indicating good processing performance. The thermal stability of the modified EP blends was evaluated by using dynamic mechanical analysis methods. The results showed that the glass transition temperature (Tg ) of EP/BMG, EP/PPO and EP/PSF blends were 123 °C, 129 °C, and 131 °C, respectively. BMG showed an excellent toughening effect on EP resin compared to PPO and PSF. In addition, the flexural strength and impact strength of EP/BMG were 114 MPa and 21.2 kJ/m2, respectively. The influence of polymers on the properties of EP resin stems from their molecular structures.

ВЛИЯНИЕ НЕСКОЛЬКИХ ВИДОВ СМОЛ НА ДИНАМИЧЕСКИЕ МЕХАНИЧЕСКИЕ СВОЙСТВА ПОЛИМЕРНОЙ СМЕСИ НА ОСНОВЕ БУТИЛКАУЧУКА

this work is devoted to the problem of developing vibration-damping polymer materials with high damping properties in a wide temperature range. The study of the effect of modifying additives on the strength, damping, adhesive and cohesive properties of a butyl rubber composite is the aim of this work. The task is to identify the actual temperature, frequency, dynamic and mechanical characteristics of a composite material based on butyl rubber depending on the type and concentration of resins. The key methods for studying this problem is the dynamic mechanical analysis method, aimed at obtaining information about changes in the dynamic properties of polymer materials (bond strength with metal when peeling samples of composites, determining the flow resistance of samples, determining the migration of plasticizer). Due to the established experimental dependences, it was found that the addition of resins (3% by weight) in the composition based on butyl rubber leads to an increase in the damping properties of composite materials, and an increase to (4.25% by weight) leads to their decrease. It was established that the obtained filled mixtures with a high damping peak and good adhesive and strength properties are mixtures with the addition of alkyl phenol-formaldehyde resins.

New Thermoplastic Damping Polymeric Materials Based on Ethylene-Vinyl Acetate

This article is devoted to the problem of working out of damping polymer materials which are effective in the wide temperature and frequency range. In the modern world, work is being carried out to create damping polymer composite materials (DPM) from which it is possible to manufacture protective elements and parts of engineering structures of reduced vibration excitability. Existing DPM have a narrow temperature range, within which effective vibration absorption is observed, moreover, most of them go through a vulcanization stage, which increases the cost of the final product, has a harmful effect on environment and allows limited recycling of waste. One of the ways to solve this problem is to replace traditional rubber vibration-absorbing materials with thermo-elastoplasts (TEP). The most promising polymer for TEP is ethylene vinyl acetate (EVA), which has high damping properties, oil resistance and relative incombustibility. In this regard, experimental studies were conducted to establish the patterns of influence of the type and concentration of structure-forming components (plasticizers, fillers, modifiers) on the dynamic mechanical properties of TEP based on EVA in order to develop a new DPM effective in a wide temperature range. The leading method to investigate this problem is a method of dynamic mechanical analysis which allows to get information about changes of mechanical characteristics under mechanical load and controlled temperature and frequency. With the help of detected patterns it was possible to determine type of plasticizer which significantly decreases glass temperature of EVA. The percentage ratio of EVA/plasticizer system is stated, and the type of plasticizer at which the maximum of mechanical losses takes over greater values is accordingly detected. It is revealed, that to work out DPM on EVA basis, which are effective in wide temperature range it is more preferable to add not less than 40 % on volume basis inert fillers, such as talc or mica with addition of 5-10 % of carbon as the hardening additive. The kind of resin improving damping properties and raising rigidity of composites on EVA basis is defined. On the basis of the research, a material was developed which has the following properties: the maximum value of tan δ is at least 0.45 at a temperature of plus 5�C (oscillation frequency 10 Hz); width of the temperature interval within which tan δ is not less than 0.3 from minus 40 to plus 50�С (oscillation frequency 10 Hz); conditional tensile strength of not less than 10 kg/cm2, cold resistance up to minus 50�C.

РЕЛАКСАЦИОННЫЕ СВОЙСТВА КОМПОЗИЦИОННЫХ МАТЕРИАЛОВ НА ОСНОВЕ СМЕСЕЙ ЭПОКСИДНЫХ ПОЛИМЕРОВ И ТЕРМОЭЛАСТОПЛАСТОВ

The influence of thermoplastic elastomers, which are two-block statistical block copolymers based on polybutylene terephthalate and polytetramethylene oxide with a different ratio of rigid and elastic blocks, on the static and dynamic mechanical properties of epoxy polymers is studied. The initial compounds for the synthesis of block copolymers are dimethyl terephthalate, 1,4-butanediol and polytetramethylenoxide with a molecular weight of 2000. The tetrabutoxide is used as catalyst. The process of interaction of the initial components is carried out in two stages, the reaction of transesterification and copolycondensation is consistently carried out. The composition of BSP is set by the ratio of initial reagents. The total molecular weight of block copolymers is 30–40 thousand. The method of dynamic mechanical analysis shows that the introduction of modifiers leads to a decrease in molecular mobility in a wide temperature range from low-temperature (at 220K) to high-temperature (at 380K) relaxation transitions. The magnitude of the effect depends on the ratio of rigid and flexible blocks in the block copolymer. It is assumed that the decrease in the tangent of the angle of mechanical losses at temperatures below the glass transition temperature and especially in the region of the β-transition, may be associated with the slowdown of relaxation processes at the interface of the epoxide matrix with rigid blocks of thermoplastic elastomer. The observed effects in the region of high-temperature transition may be associated with the restriction of freedom of conformational rearrangements near the interface of the epoxy polymer with polybutylene terephthalate and polytetramethylene oxide blocks and an increase in the cross-linking density of the epoxy. A noticeable decrease in the magnitude and creep rate of epoxy composites is found when thermoelastoplast is introduced.

Experimental Study on the Phase Transition Characteristics of Asphalt Mixture for Stress Absorbing Membrane Interlayer

Asphalt mixtures used in stress absorbing membrane interlayers (SAMIs) play a significant role in improving the performance of asphalt pavement. To investigate the rheological properties and phase transition characteristics of asphalt mixtures used in SAMI with temperature changes, twenty-seven candidate mixtures with different binders, gradation types and binder contents were selected in this research. During the study, dynamic mechanical analysis method was employed to evaluate their temperature-dependent properties and a series of wide-range temperature sweep tests were conducted under a sinusoidal loading. Some critical points and key indexes from the testing curves such as glass transition temperature (Tg) can be obtained. Test results show that phase transition characteristics can better reflect the rheological properties of asphalt mixtures at different temperatures. Crumb rubber modified asphalt mixtures (AR) provide a better performance at both high and low temperatures. Additionally, the range of AR asphalt mixtures’ effective functioning temperature ΔT is wider, and the slope K value is greater than the others, which indicates that AR asphalt mixtures are less sensitive to temperature changes. Additionally, gradation type and asphalt content also influence the properties: finer gradation and more asphalt content have a good effect on the low-temperature performance of the asphalt mixtures; while mixtures with a coarser gradation and less asphalt content perform better at high temperature and they are less sensitive to temperature changes. Finally, AR asphalt mixture is more suitable to be applied in the SAMI due to its phase transition characteristics from this method.

Concept of a polishing tool based on viscoelastic properties for midspatial frequencies suppression on aspheric surfaces

We focus on the subaperture polishing tool concept development for suppressing midspatial frequencies (MSF) arising from computer numerical control machining of aspherical optical surfaces. The selective effect in the MSF range is achieved by setting the tool viscoelastic properties so that rigidity increases in the frequency-domain generated by the rotational tool movement over the aspheric surface with the MSF while the tool remains flexible in the lower frequency range associated with tool radial direction movement. The mechanism of MSF removal is discussed in detail, including in terms of elasticity module frequency dependences, and is also experimentally verified. In order to monitor and optimize viscoelastic properties, especially in regard to frequency dependences, the dynamic mechanical analysis method has been developed and applied and is presented in the paper as well.

The heating rate influence on the elastic modulus temperature dependence of a corrosion-resistant nickel alloy

The temperature dependence of the elastic modulus of nickel-chromium-molybdenum alloy C4 was investigated by the method of dynamic mechanical analysis. At all heating rates, an abnormal increase in the elastic modulus is observed upon heating in the temperature range of 200-300 °C. It is shown that an increase in the heating rate shifts the beginning of the observed effect to the region of higher temperatures. The temperature anomaly in the elastic modulus of the C4 alloy is explained from the standpoint of the formation of a short-range order in a solid solution. The thermodynamically equilibrium temperature of the “disorder – short-range order” transition in C4 alloy is determined to be 205 °C.

Thermomechanical Analysis of Composite Films Based on Chitosan and Chitin Nanofibrils

Nanocomposite films based on chitosan and filler in the form of chitin nanofibrils were prepared. An analysis of the film morphology by scanning electron microscopy demonstrated a uniform distribution of filler nanoparticles in the bulk of a film and their predominantly planar orientation. The influence exerted by chitin nanofibrils on the elasticity modulus, strength characteristics and the rate of thermal destruction of the films was examined. The method of multifrequency dynamic mechanical analysis was used to evaluate the influence exerted by the content of chitin on the glass-transition temperature of the nanocomposites. The effect of chitin nanoparticles introduced into a bioresorbable chitosan matrix on the hygroscopicity of composite films was examined.

The Gradient of Dynamic Mechanical Characteristics across the Thickness of Epoxy Polymers during Environmental Exposure

Temperature dependences of dynamic modulus of elasticity and dynamic loss modulus of four compositions of epoxy polymers based on 2,2-di-(4-hydroxyphenyl) propane and a cycloaliphatic amine hardener in an initial state and after 3, 6, 9, and 12 months of exposure on an open bench under conditions of moderately warm climate of Gelendzhik. A glass transition temperature determined during a transition from a glassy state to a highly elastic one of epoxy polymers proved to be sensitive to the polymer composition, an amount of sorbed moisture and duration of exposure. Postcuring of polymers, masked by a plasticizing effect of moisture, is discovered. The glass transition temperature of exposed epoxy polymers changes unevenly across the thickness of specimens. Properties of a surface layer facing the sun (on the front side) change to the greatest extent. Methods of dynamic mechanical analysis have good sensitivity and informativeness for a study of non-uniformity of climatic aging across the thickness.

Dynamic mechanical analysis of novel cosmeceutical facial creams containing nano-encapsulated natural plant and fruit extracts.

Cosmetic industry following the recent trends in the relative market has turned its interest in the formation of cosmeceutical products containing natural bioactive ingredients. Natural extracts may reveal undesirable sensory characteristics due to their composition. Encapsulation and nanotechnology are the most promising methods to overcome these drawbacks, opening up new perspectives for the future of cosmeceutical industry. The purpose of this study was the use of nano-encapsulated plant and fruit extracts to formulate cosmeceutical facial creams with acceptable rheological characteristics. Electrohydrodynamic process was used to encapsulate pomegranate and tea tree oil extracts and incorporate them in facial cosmetic creams. All the formulations including those without additives, were stored at three different temperatures. Subsequently, rheological oscillatory tests (frequency sweep tests) were performed using the dynamic mechanical analysis method in order to evaluate alterations in storage modulus (G'), loss modulus (G''), and complex viscosity (η*). Dynamic mechanical analysis, showed that all formulations are suitable for application in cosmetic industry, while changes due to storage period or the storage temperature were negligible. The addition of the selected extracts' nanofibers to formulate cosmeceutical facial creams, developed products with acceptable rheological characteristics that could be decisive for the cosmetics industry.

Effect of the addition of thiourethane oligomers on the sol⿿gel composition of BisGMA/TEGDMA polymer networks

ObjectivesThiourethane oligomers have been shown to increase the fracture toughness and reduce the polymerization stress of methacrylate-based materials. However, network formation has not been elucidated in these materials yet. The aim of this study was to evaluate how the addition of a thiourethane oligomer (TU) influences the sol/gel composition and network structure of methacrylate-based materials using dynamic mechanical analysis and extraction methods. Materials and methodsBisGMA/TEGDMA at systematically varied mass ratios (20/80 to 80/20wt%) were mixed with pre-polymerized thiourethane oligomers at 0 (control) or 20wt%, synthesized by combining pentaerythritol tetra-3-mercaptopropionate with dicyclohexylmethane 4,4⿲-Diisocyanate, at 1:2 isocyanate:thiol. 0.1wt% of 2,2-Dimethoxy-2-phenylacetophenone was added as the photoinitiator and 0.3wt% of 2,6-di-tert-butyl-4-methylphenol was added as a free radical inhibitor. Disk specimens (0.8ÿ10mm in diameter, n=3) were photoactivated at 270mW/ (320⿿500nm) for 1min. The degree of conversion (DC) was measured in near-IR (˿6165cm⿿1). Specimens were immersed in two different solvents (water for 7 days or dicholoromethane for 48h). Water sorption (WS) and solubility (SL) were obtained according to ISO 4049. The leachates for both solutions were analyzed with 1H-NMR (400MHz, CDCL3). Bar specimens (1ÿ3ÿ25mm, photocured and then post-processed at 180°C for 8h to DC>95%) were subjected to dynamic mechanical analysis (⿿30 to 230°C) to obtain glass transition temperature (Tg), tan delta curves and crosslinking density (ν). Data was analyzed with two-way ANOVA/Tukey⿿s test (95%). ResultsIn general, the presence of TU increased the overall conversion. The WS was similar for all groups, but the SL decreased by 2-fold with the addition of the TU oligomer for all compositions, except BisGMA/TEGDMA 80/20. The BisGMA concentration of the leachates increased with increasing BisGMA in the initial mixture, and with the presence of thiourethane. This compositional drift of the gel with the presence of TU was attributed to the preferential dissolution of TEGDMA into the TU network. Tg and ν decreased with the addition of TU, as expected. The addition of TU produced more homogeneous networks, as evidenced by narrower breadth of the tan delta curve. ConclusionThe addition of TU affected the composition of the sol/gel in crosslinked networks, which were more homogeneous and presented 2-fold less potentially toxic leachates than the methacrylate controls. Clinical significanceThe addition of TU may produce less cytotoxic materials based on the increased conversion and reduced amount of unreacted extractables from its network after water storage.

Characterizing Transformation Phenomena and Elastic Moduli of Austenite and Oriented Martensite of Superelastic Thin NiTi Wire through Isothermal Dynamic Mechanical Analysis

In this paper, superelastic behavior of Nickel Titanium thin wires is characterized using the method of dynamic mechanical analysis. Nominal dynamic storage modulus ′ is measured as function of nominal strain and stress during isothermal superelastic tensile tests at three testing temperatures above the reverse martensitic transformation finish temperature. The method brings new information on deformation mechanisms compared to the consideration of only tensile stress-strain curves. It is shown that determination of the elastic moduli E, especially at high strain, requires to calculate the true storage modulus ′. Using ′ and not ′, elastic modulus of oriented martensite is determined equal to 73 GPa of the same order than the elastic modulus of austenite equal to 70 GPa. Two models are then proposed to simulate experimental storage moduli evolution during the tests. A first model explains the ′ evolution during stress plateau by the localization phenomenon ; it leads to express ′ as function of the nominal strain. A second model describes the evolution of ′ after the stress plateau as function of true stress and test temperature. This model permits to determine the Clausius-Clapeyron coefficient of the forward transformation.

The Influence of Modified Additives on Dynamic Properties of Polymeric Materials Based on Ethylene-Vinyl Acetate

The article deals with the problem of creating vibration damping polymeric materials with high damping properties in a wide temperature range. The purpose of the article is to study physical-mechanical properties of composites based on ethylene-vinyl acetate by adding various modifiers in the form of resins. The main method to investigate this problem is the method of dynamic mechanical analysis, which makes possible to obtain viscoelastic properties of polymeric materials under the influence of an oscillating load at various temperatures and oscillation frequencies. Due to the established experimental dependencies, the authors have determined the type of resin, which improves the damping properties and increases the stiffness of the composites based on ethylene-vinyl acetate. Moreover, the authors have defined the limit of working capacity of composites with resins at negative temperatures.

Testing the mechanical and tribological properties of new metal-polymer nanocomposite materials based on linear low-density polyethylene and Al65Cu22Fe13 quasicrystals

Metal-polymer nanocomposite materials based on linear low-density polyethylene (LLDPE) and Al65Cu22Fe13 quasicrystals were first obtained by melt-blending. The methods of thermal analysis and dynamic mechanical analysis were used to analyze the thermal stability and physicomechanical properties of the obtained nanocomposite materials. It has been found that increasing the content of nanofillers increases the elastic modulus, but tensile strength also increases, especially at low filler concentrations. Friction and wear were assessed on pin-on-disc tester. The results show that the friction coefficient of the sample with 1 wt% content of nanofiller is lower than that of pure LLDPE, and the anti-wear properties of the composite material are increased by 57% compared to pure LLDPE. In addition, during friction with a load of up to 147 N, a protective antifriction film of metallic nanoparticles on the friction surface forms for this sample.

Changes in rubber properties during storage and operation studied by express method of dynamic mechanical analysis

The paper considers changes in the properties of rubber in large-sized products using the method of dynamic mechanical analysis (DMA) in comparison with the previous physical and mechanical investigation data. It is possible to predict changes in properties of rubber during storage or operation if using the combined estimation and prediction curve for the most characteristic indicator of aging.

Влияние gamma-облучения и допирования диоксидом кремния на свойства политетрафторэтилена

V. M. Egorov1, P. N. Yakushev1, M. A. Arsentiev2,3, A.S. Smoliansky2,3. 1Ioffe Institute, Russian Academy of Sciences, St. Petersburg, Russia 2 Branch of JSC Karpov NIFHI, Moscow, Russia 3 Mendeleev University of Chemical Technology, Moscow, Russia A comparative analysis for the melting of Polytetrafluoroethylene both in the initial and irradiated state and for composition with 1% "green" silica has been carried out. The method of Dynamic Mechanical Analysis was used to characterize the glass transitions for all compositions studied. The calculation based on the smeared first-order phase transition theory for the contours of the thermal capacity peaks made it possible to reveal the features of structural changes in the composite and in the irradiated Polytetrafluoroethylene.

Investigation of the processes of softening and crystallization of glassy selenium by dynamic mechanical analysis method

Purpose. The purpose of this work was the investigation of mechanical characteristics of glassy and polycrystalline selenium in glasstransition and crystallization regions by dynamic mechanical analysis method and also the determination of relaxation parameters and establishing the mechanism of dissipative processes in selenium above its softening temperature . Methods. It was measured the mechanical loss tangent and dynamic modulus of elasticity as functions of tem perature. Measurement of these parameters were performed in the mode of forced bending oscillations at a frequency of 0.5 Hz using the Q400 TMA device at a temperature range 220 K - 450 K. Results. In glassy selenium in softening temperature region the a-process of mechanical relaxation with a relative decrease of the elastic module ∆E/E = 0.73 was found. Rapid increase in the elastic modulus due to the crystallization processes of glassy selenium in the interval 353 K - 378 K was observed. Cooling of selenium sample from 450 K to 220 K did not reveal of glassforming effects on the temperature dependences of the elastic modulus and the mechanical loss tangent: a sample of selenium was polycrystalline. Maxima are observed in the temperature dependences of the tangent of the angle of mechanical losses at the α-process of relaxation and crystallization of glassy selenium. Conclusions. In the temperature dependence of the elastic module of glassy selenium a high elasticity plateau was found. The presence of a highly elastic state in glassy selenium in the temperature range 325 K-350 K and crystallization process in the range of 353 K-378 K are shown. In polycrystalline selenium there are no dissipative processes that are characteristic of the glasslike state.

Morphological and Dynamic Mechanical Analysis of Vibration Damping Composite Material Based on Different Elastomers

This work deals with the problem of developing vibration damping polymeric materials which are effective at low temperatures (from minus 40 to 0�C). Due to the fact that the vibration damping efficiency in the composite is mainly determined by the properties of the polymer matrix, it is necessary to study its properties depending on the type and amount of structure-forming parameters. The purpose of the work is to determine the changes in the dynamic properties of the polymer composition based on butyl rubber, EPDM, ethylene-vinyl acetate copolymer (EVA) filled with increasing amount of calcium carbonate. The leading methods of studying this problem were the method of scanning electron microscopy and the method of dynamic mechanical analysis. It has been stated that the selected polymers can be considered as competent candidates for damping materials at low temperatures, and the calcium carbonate filler allows more fully to realize the vibration damping properties of the polymer. The obtained dependences can be used as initial data for analytical predicting of damping properties of polymer composites.

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.

Correlation between mechanical properties and thermochemical behaviours of waste papers in their early devolatilization stage

This article details a correlation study on early devolatilization behaviors (drying & volatile emission at 25–240 °C) and the change in mechanical properties (expressed by viscoelasticity) of four types of waste papers. The early stage of devolatilization was investigated using the TG-FTIR and mechanical properties using the dynamic mechanical analysis (DMA) method. The results show that the elastic and viscous mechanical properties showed obvious correlations with free and bound water evaporation and volatile emission. The storage modulus (E′) and loss modulus (E″) of the papers decreased as temperature increased and at the two important temperatures, namely 100 °C, the start of bound water evaporation, and 150 °C, the start of devolatilization in TG & DTG curves, E′ showed extrema. Especially the relative storage modulus (E′r) exhibited a sudden decrease at around 150 °C, where the activation energy of thermochemical conversion jumps from low values to high values, indicating the start of devolatilization. CO2 is the major compound of the volatiles and it is well correlated with E′r in exponential function model and can be used as an index for predicting the E′r of the waste papers in their early devolatilization stage; while during the drying stage, mass loss ratio can be used to predict E′r of the waste papers.