Dynamic Mechanical Thermal Analysis Techniques Research Articles

A novel semi-analytical methodology for predicting sound absorption of anechoic coatings with arbitrary rotary cavities dependent on temperature and frequency

In response to the shortcomings of existing studies on the sound-absorbing characteristics of an anechoic coating, which most ignore the frequency factor and are expensive for temperature-tunable hydroacoustic experiments, a novel semi-analytical methodology that considers both frequency and temperature is proposed in this paper. Based on the dynamic mechanical thermal analysis technique and time–temperature superposition principle, the temperature and frequency spectra of two rubber materials are tested and expanded in turn. Meanwhile, a complete acoustic prediction model is developed employing the non-uniform waveguide theory for an overburden containing arbitrary rotary cavities. Furthermore, taking a lining embedded with ramped cavities as the research structure, the theoretical model is firstly validated by an absorptive measurement conducted with the hydroacoustic impedance tube test-system, and then the acoustic influences of the material properties and geometric parameters of each sublayer, as well as the temperature factor, are investigated in-depth to reveal the multiple energy dissipation mechanisms. These results show that the present semi-analytical method can accurately and effectively predict the dynamic sound absorptions of a covering in the wide temperature-frequency range of Tg ~ Tg + 50 ℃ and 10 Hz ~ 106 Hz.

Influence of graphite particles in thermal properties of amylopectin/PVA-based hydrogels

The aim of the present work is to study the influence of graphite particles on the molecular structure of the hydrogel composed of amylopectin/poly(vinyl alcohol) hybrid matrix by thermogravimetric analysis, differential scanning calorimetry and dynamic mechanical thermal analysis techniques. Hybrid amylopectin/PVA hydrogels were prepared with and without particles, and their properties were measured. The results of the analyses showed that the presence of particles in the reaction medium decreased the formation of cross-links among macromolecular chain segments, modifying thermal and mechanical properties of hydrogel. Raman spectroscopy confirmed the obtaining of graphitic carbon particles. Besides, optical microscopy and atomic force microscopy showed a large distribution in particles dimensions.

Thermal degradation, dynamic mechanical and morphological properties of PVC stabilized with natural polyphenol-based epoxy resin

In this study, the thermal degradation, dynamic mechanical and morphological properties of polyvinyl chloride (PVC) stabilized with tannin-based epoxy resin and with Ca/Zn-based thermal stabilizers were studied. The efficiency of tannin epoxy resin as thermal stabilizer and additive for PVC was explored in this work using thermogravimetric analysis, dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM) techniques. The obtained TG results reveal that the tannin-based epoxy resin as well as Ca/Zn-based thermal stabilizer has a significant effect on the thermal stability of PVC. The viscoelastic properties of PVC with and without tannin epoxy resin were evaluated by dynamic mechanical thermal analysis technique (DMTA). It was observed that the tannin derivative has an improvement effect on the viscoelastic properties of PVC. The glass transition temperature of PVC/tannin epoxy resin occurs at about 90–93 °C and it is close to that of PVC formulated with Ca/Zn-based commercial thermal stabilizer and without using a plasticizer. DMTA properties show that PVC incorporated with tannin epoxy resin have relatively more recognized flowing stage which occurs smoothly at 160 °C. Other analytical techniques such as SEM and energy dispersive X-ray spectroscopy are employed on PVC morphological properties. Experimental results confirm that the tannin epoxy increase thermal stability of PVC which exhibits smooth and homogenous surface properties compared to the commercial thermal stabilizer.

Development of Functional Polyurethane–ZnO Hybrid Nanocomposite Coatings from Thevetia peruviana Seed Oil

AbstractThe present article reports eco‐friendly multi‐functional polyurethane–ZnO hybrid nanocomposite coatings obtained from Thevetia peruviana seed oil (TPSO). Initially, the polyols were prepared by treating TPSO with glycerol and the formation was supported by Fourier transform infrared (FT‐IR) and 1H‐NMR studies. In the next stage, siloxane functionalized ZnO nanoparticles were added to the polyol mixture in different weight percentages (0, 1 and 2 %) and then treated with excess 4,4′‐diisocyanatodicyclohexylmethane (H12MDI) in order to synthesize isocyanate terminated polyurethane nanocomposites. The polyurethane hybrids were then casted as thin films and cured under atmospheric moisture. After complete curing they were characterized by using FT‐IR, 1H‐NMR, 13C‐NMR, X‐ray diffraction, scanning electron microscopy, thermogravimetric analysis, and dynamic mechanical thermal analysis techniques. The hybrid nanocomposites showed superior thermo‐mechanical and anti‐corrosive properties compared to pristine polyurethane. Also, due to the presence of nano ZnO in the polyurethane matrix, the composite coatings are showing excellent resistance towards various bacterial and fungal stains.

Characterization of Shape Memory Polymer Estane by Means of Dynamic Mechanical Thermal Analysis Technique

Commercially available shape memory polymer (SMP) Estane (designation: ETE75DT3 NAT022) is investigated by means of dynamic mechanical thermal analysis (DMTA) technique in torsion mode using the Modular Compact Rheometer MCR-301 (Anton Paar GmbH). Amplitude sweep tests have been run below and above the glass transition temperature to establish the linear viscoelastic range (LVR) in glassy and rubbery phase of this SMP for the correct physical interpretation of DMTA data. Temperature sweep tests were performed at various frequencies to study the influence of this parameter on values of the storage and loss moduli and the storage and loss compliances as well as the viscosities. These tests have been carried out in heating mode with different rates and at different strain amplitudes. The short- and long-term behavior of SMP Estane have been studied by frequency sweep tests performed at different temperatures and data have been transformed into time-domain properties by applying time-temperature superposition principles. All these DMTA data provide the experimental basis for the study of relaxation processes, property-structure relationships, and the shape memory effect in this little-known SMP.

REDUCCIÓN DEL RUIDO ESTRUCTURAL Y LA VIBRACION EN UN PROTOTIPO DE CABINA DE ASCENSOR MEDIANTE LA UNIÓN ADHESIVA DE PANELES

Abstract This paper presents an experimental study for the structural noise and vibration reduction in a cabin elevator by means of adhesive bonded joints of panels. For that noise and vibration measurements are carried out on two prototypes: one of them built with classical panel joining technologies and the other one with adhesive joints. First of all the mechanical properties (relaxation and complex moduli) of two low modulus materials are compared: a silane and a modified silane adhesives. These properties are obtained for both materials by means of dynamic mechanical thermal analysis technique (DMTA), the master curves under direct strain being built-up through a procedure based on the time-temperature superposition (TTS) principle. Next, the influence that these two materials have on the dynamic response of an adhesively bonded metallic beam is investigated, in order to select the right candidate according to design criteria. Finally, an application for an elevator cabin prototype is presented, in which noise and vibration are measured in order to put into evidence the benefits of joining panels by means of adhesive bonded joints in contrast to the traditional joining technologies. Keywords: Noise and vibration reduction; adhesive bonded joints; cabin elevator

Preparation and characterisation of polyamide 11/montmorillonite (MMT) nanocomposites for use in angioplasty balloon applications

With increased demands on catheter balloon functionality, there is an emphasis to blend new materials which can improve mechanical performance. Polymer nanocomposites were prepared by melt blending polyamide 11 (PA 11) with organically modified montmorillonite nanoclay. The effects of incorporating the nanoclay on the short-term mechanical properties of PA 11 were assessed using a design of experiments (DoEs) approach. X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis techniques (DMA) were used to characterise the morphology of the nanocomposites. Design of experiments studies revealed that the optimum nanocomposites properties can be achieved by carefully controlling the melt compounding parameters. XRD and TEM data proved that exfoliated clay morphologies existed within the matrix at low clay loading (2%). Whereas the interaction between the polymer matrix and nanoclay was quantified in the DMA spectra, showed a significant increase in storage modulus (up to 80%). The reinforcing effect of nanoclay within the PA 11 was further investigated using mechanical testing, where significant increases in the ultimate tensile strength and strain at break of reinforced tri-layer balloon tubing were observed.

Effect of nanosilica on the dielectric properties and thermal stability of polyimide/SiO2 nanohybrid

New polyimide–silica (PI–SiO2) nanohybrids were prepared by the reaction of bis(5-amino-1-naphthoxy) diphenylsilane (5-APS) with commercially available 4,4’-(Hexafluoroisopropylidene) diphthalic anhydride (6-FDA) in the presence of 3-aminopropyl triethoxysilane as a coupling agent and tetraethylorthosilicate (TEOS) as precursor of inorganic network. Hybrid thin films with 5–50 wt.% silica content were synthesized. The prepared PI–SiO2 films were characterized by Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy. The morphology and crystallinity of these hybrid systems were investigated by transmission electron microscopy and XRD analysis. Thermal properties of the nanohybrids were evaluated by thermogravimetric analysis and dynamic mechanical thermal analysis techniques. The optical constants (n and k) and dielectric parameters ( and ) were calculated from IR reflection spectra by employing the Kramers–Kronig dispersion relations. Under proper condition, the silica particle size was in the range of 50–70 nm for the prepared hybrids. The results showed that presence of silica severely modified the properties of samples.

Experimental characterization and modelization of the relaxation and complex moduli of a flexible adhesive

In this paper, the experimental characterization and modelization of the relaxation and complex moduli of the flexible adhesive ISR 70-03 by means of dynamic mechanical thermal analysis technique (DMTA) is presented. Firstly, the procedure followed to obtain and to validate the test specimens is described. Next, the linearity concerning material behavior related to strain level and test specimen thickness is analyzed. Then, relaxation and dynamic master curves under tension strain are built-up by means of a procedure based on the time–temperature superposition principle. Finally, these master curves are modelized using a generalized Maxwell model and a fractional derivative model. As a result, models capable of taking together into account the influence of time, temperature and strain level are proposed.

The use of dynamic mechanical thermal analysis technique for determining an uneven distribution of precipitated silica in CPE/NR blends

Precipitated silica is generally used as non-black reinforcing filler for light colored products. Compared with carbon black, the use of silica is subject to many problems, particularly poor silica dispersion and distribution. In silica filled CPE/NR blends, the uneven distribution of silica in each phase of the blend occurs mainly due to strong filler–polymer interaction between silanol groups on the silica surfaces and chlorine atoms on the CPE backbone. In order to investigate the uneven filler distribution in polymer blends, changes in damping behavior could be used to calculate the amount of silica localizing in each phase of the blends. The results reveal that, with small loading of silica, an even silica distribution is observed due to the counter-balancing effects of relatively low viscosity of the NR phase and strong silica–CPE interaction. As silica loading increases, the effect of strong silica–CPE interaction becomes dominant, leading to preferential migration of silica to the CPE phase. The uneven silica distribution at high silica loading is found to be reduced by addition of silane coupling agents. The effect of 3-thiocyanatopropyl triethoxy silane (Si-264) is more pronounced than bis-(3-triethoxysilylpropyl) tetrasulfane (Si-69) due to the superior wettability and, hence, the silanol deactivation efficiency. The determination of uneven silica distribution by dynamic mechanical properties is in good agreement with the phase morphology of blends.

Synthesis and characterization of novel, biodegradable, thermally stable chitin‐based polyurethane elastomers

AbstractBiodegradable polyurethane (PU) elastomers with potential for biomedical and industrial applications with tunable thermal properties were synthesized by the reaction of poly(ϵ‐caprolactone) and 4,4′‐diphenylmethane diisocyanate and extended with different mass ratios of chitin and 1,4‐butane diol (BDO). Their chemical structures were characterized with Fourier transform infrared, 1H‐NMR, and 13C‐NMR spectroscopy, and the thermal properties were determined by thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical thermal analysis techniques. The incorporation of chitin contents into the PU backbone caused improvements in the thermal stability and degradation rate. Optimum thermal properties and degradation profile were obtained from elastomers extended with chitin, whereas elastomers extended with BDO displayed the worst properties. The investigation of the structure–property relationships of the prepared elastomers showed that the main determining factors for the observed properties were the physical effective crosslink density, hydrogen bonding, thermal stability, and content of chitin in the PU backbone. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Synthesis and thermomechanical characterization of polyurethane elastomers extended with α,ω‐alkane diols

AbstractA series of polyurethane (PU) elastomers was prepared by the reaction of poly(ϵ‐caprolactone) and 4,4′‐diphenylmethane diisocyanate, which was extended with a series of chain extenders (CEs) having 2–10 methylene units in their structure. The completion of the reaction was confirmed by Fourier transform infrared spectroscopy. The chemical structures of the synthesized PU samples were characterized with Fourier transform infrared, 1H‐NMR, and 13C‐NMR spectroscopy, and the thermal properties were determined by thermogravimetric analysis, DSC, and dynamic mechanical thermal analysis techniques. The mechanical properties were also studied and are discussed. The thermogravimetric analysis and DSC analysis showed that CE length had a considerable effect on the thermal properties of the prepared samples. The dynamic mechanical thermal analysis and damping peaks were also affected by the number of methylene units in the CE length. The elastomer extended with 1,2‐ethane diol exhibited optimum thermal properties, whereas the elastomer based on 1,10‐decane diol displayed the worst thermal properties. Tensile strength and elongation at break decreased with increasing CE length, whereas hardness showed the opposite trend. The glass‐transition temperature moved toward lower temperatures with increasing CE length. The decrease in the glass‐transition temperature and tensile properties were interpreted in terms of decreasing hard segments and increasing chain flexibility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

A new method for measuring damping in flexural vibration of thin fibers

In this paper we describe a new method for measuring damping in flexural vibration of filamentous matter, such as polymeric or metallic fibers. This method enables us to measure the damping characteristics of very thin fibers (down to lateral dimensions of a few micrometers). The fiber sample is clamped at one extremity and excited in the flexural vibration mode of a cantilever beam configuration, using a piezoelectric actuator. While the fiber sample vibrates around a flexural eigenfrequency, structural damping is determined from the measurement of the curve of phase difference between excitation and motion. This technique does not require the amplitude of the fiber motion to be determined. The phase curve is inferred from the periodic disturbance occurring when the fiber acts as a shutter for a light beam. This method can be applied to fibers of arbitrary shape and material. Examples are shown of measurements with polymer and metallic fibers. Flexural damping is evaluated at atmospheric pressure and in vacuum. The technique is validated by a comparison with polypropylene damping measurements from standard dynamic mechanical thermal analysis techniques.

Glass‐transition temperature based on dynamic mechanical thermal analysis techniques as an indicator of the adhesive performance of vinyl ester resin

AbstractVinyl ester resins are being used extensively as matrices in fiber‐reinforced polymer composite materials, but their use as a structural adhesive has been limited. Initial studies investigating the durability of a vinyl ester as a wood adhesive showed unsatisfactory performance in comparison with other adhesives. In this work, the glass‐transition temperatures (Tg's) of a vinyl ester and a E‐glass/vinyl ester composite material, fabricated by the Composites Pressure Resin Infusion System, were determined with dynamic mechanical thermal analysis. The results indicated that the resin cured under ambient conditions had a much lower Tg (∼60°C) than the postcured material (∼107°C). This suggested undercuring, that is, incomplete crosslinking, of the resin when it was cured at room temperature. E‐glass/vinyl ester samples, however, showed virtually no difference in Tg between room‐temperature‐cured and postcured samples. The exact reasons for this are not currently known but are thought to be both mechanical and chemical in nature. On the basis of the findings presented in this article, it can be concluded that if this vinyl ester resin is to be used as a structural adhesive, postcuring or formulation to ensure a high degree of crosslinking under ambient conditions is necessary. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2221–2229, 2005

Study of carbon black distribution in BR/NBR blends based on damping properties: Influences of carbon black particle size, filler, and rubber polarity

AbstractEffects of filler and rubber polarity on the distribution of filler in butadiene/nitrile rubber (BR/NBR) blends were investigated, using the dynamic mechanical thermal analysis technique. As 30‐phr filler is added, the reduction in heights of damping peaks (tan δmax), attributed to the dilution effect, was observed. It was also found that the BR phase in the blends, compared to the NBR phase, is more preferential for small‐ and large‐particle size carbon blacks to reside, probably because of the lower viscosity and lower polarity of the BR phase. The addition of silica instead of carbon black leads to an increase in filler migration to the NBR in the 20/80 BR/NBR blend, which is attributed to the strong silica–NBR interaction. In addition, an increase in NBR polarity promotes carbon black migration to the BR phase. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3198–3203, 2001

A study of the morphology of polyurethane–polystyrene interpenetrating polymer networks by means of small angle X‐ray scattering, modulated‐temperature differential scanning calorimetry, and dynamic mechanical thermal analysis techniques

The morphology of polyurethane–polystyrene (PU-PS) (60 : 40 by weight) interpenetrating polymer networks (IPNs), in which internetwork grafting via 2-hydroxyethyl methacrylate resides (HEMA) (1, 2.5, and 10 wt %, respectively) in the polystyrene networks has been studied by means of small angle X-ray scattering (SAXS), modulated-temperature scanning calorimetry (M-TDSC), and dynamical mechanical thermal analysis (DMTA) techniques. With increasing internetwork grafting, the average size of domains became smaller (SAXS data) and the degree of component mixing increased (M-TDSC and DMTA results). For the PU-PS (60 : 40 by weight) IPN with 10% HEMA, the DMTA tan δ-temperature plot showed a single peak. This DMTA result implied that the morphology of this PU-PS IPN is homogeneous. However, the M-TDSC data showed that three PU-PS (60 : 40) IPNs samples (with 1, 2.5, and 10 wt % HEMA, respectively) were phase separated. For the three IPN samples, the correlation length of the segregated phases, obtained from SAXS data based on the Debye–Bueche method, did not show distinct differences. With increasing internetwork grafting, the scattered intensity decreased. This study concluded that for these IPNs, SAXS is sensitive to the size of domains and component mixing, but no quantitative analysis was given for the component mixing. M-TDSC is suitable to be used to quantify the degree of component mixing or the weight fraction of interphases, and DMTA is sensitive to damping behavior and to phase continuity. However, DMTA cannot provide quantitative information about the degree of component mixing or the weight (or volume) fraction of the interphases. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1958–1964, 2001

A study of the morphology of polyurethane-polystyrene interpenetrating polymer networks by means of small angle X-ray scattering, modulated-temperature differential scanning calorimetry, and dynamic mechanical thermal analysis techniques

The morphology of polyurethane–polystyrene (PU-PS) (60 : 40 by weight) interpenetrating polymer networks (IPNs), in which internetwork grafting via 2-hydroxyethyl methacrylate resides (HEMA) (1, 2.5, and 10 wt %, respectively) in the polystyrene networks has been studied by means of small angle X-ray scattering (SAXS), modulated-temperature scanning calorimetry (M-TDSC), and dynamical mechanical thermal analysis (DMTA) techniques. With increasing internetwork grafting, the average size of domains became smaller (SAXS data) and the degree of component mixing increased (M-TDSC and DMTA results). For the PU-PS (60 : 40 by weight) IPN with 10% HEMA, the DMTA tan δ-temperature plot showed a single peak. This DMTA result implied that the morphology of this PU-PS IPN is homogeneous. However, the M-TDSC data showed that three PU-PS (60 : 40) IPNs samples (with 1, 2.5, and 10 wt % HEMA, respectively) were phase separated. For the three IPN samples, the correlation length of the segregated phases, obtained from SAXS data based on the Debye–Bueche method, did not show distinct differences. With increasing internetwork grafting, the scattered intensity decreased. This study concluded that for these IPNs, SAXS is sensitive to the size of domains and component mixing, but no quantitative analysis was given for the component mixing. M-TDSC is suitable to be used to quantify the degree of component mixing or the weight fraction of interphases, and DMTA is sensitive to damping behavior and to phase continuity. However, DMTA cannot provide quantitative information about the degree of component mixing or the weight (or volume) fraction of the interphases. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1958–1964, 2001

Anhydride and diamine epoxy–Kevlar composites: thermal and dynamic‐mechanical properties

Differential scanning calorimetry (DSC) and dynamic–mechanical thermal analysis techniques have been used to characterize different Kevlar–epoxy composites. Tetrafunctional aliphatic amine and anhydride–diglycidyl epoxy have been used as matrix, and different quantities of continuous Kevlar fibers as reinforcement. Kevlar fibers had different effects on curing kinetics and final thermal properties depending on epoxy matrix type. As Kevlar content increased DSC heat flow curves shifted to much lower temperatures in the anhydride matrix case, while there was very little difference in the diamine–epoxy one. A significant decrease in the glass transition temperature (Tg) was observed as Kevlar content increased when anhydride matrix was used, while little change was observed in the reinforced diamine systems. Loss tangent and storage modulus versus frequency master curves were obtained from isothermal scans. The main dynamic–mechanical relaxation and its evolution versus frequency with fiber addition was studied. An important shift to high frequencies was observed in the anhydride system. Copyright © 1999 John Wiley & Sons, Ltd.

Anhydride and diamine epoxy-Kevlar composites: thermal and dynamic-mechanical properties

Differential scanning calorimetry (DSC) and dynamic–mechanical thermal analysis techniques have been used to characterize different Kevlar–epoxy composites. Tetrafunctional aliphatic amine and anhydride–diglycidyl epoxy have been used as matrix, and different quantities of continuous Kevlar fibers as reinforcement. Kevlar fibers had different effects on curing kinetics and final thermal properties depending on epoxy matrix type. As Kevlar content increased DSC heat flow curves shifted to much lower temperatures in the anhydride matrix case, while there was very little difference in the diamine–epoxy one. A significant decrease in the glass transition temperature (Tg) was observed as Kevlar content increased when anhydride matrix was used, while little change was observed in the reinforced diamine systems. Loss tangent and storage modulus versus frequency master curves were obtained from isothermal scans. The main dynamic–mechanical relaxation and its evolution versus frequency with fiber addition was studied. An important shift to high frequencies was observed in the anhydride system. Copyright © 1999 John Wiley & Sons, Ltd.

Envelhecimento físico de sistemas DGEBA/DDM investigado por análise térmica (DSC/DMA)

Neste trabalho, estudou-se o efeito do envelhecimento físico nas propriedades térmicas e mecânicas em sistemas diglicidil éter do bisfenol-A (DGEBA)/diaminodifenilmetano (DDM), em função do grau de conversão, induzido pela cura e do tempo de envelhecimento. A cura isotérmica foi realizada em uma etapa a 115°C por diversos tempos e o envelhecimento foi conduzido a 100°C por períodos de 240 a 4320 min. Considerando que o envelhecimento físico acarreta variações estruturais as quais afetam tanto o desempenho mecânico quanto as propriedades termodinâmicas do material, as técnicas de DSC e DMA são complementares. Através de Calorimetria Exploratória Diferencial (DSC), observou-se que o envelhecimento físico está associado ao pico endotérmico que ocorre na região da transição vítrea e que a entalpia de relaxação, calculada a partir da área deste pico, aumenta gradualmente com o tempo de envelhecimento. Os resultados obtidos por Análise Dinâmico-Mecânica (DMA) mostraram um aumento do módulo elástico E' com o tempo de envelhecimento. As velocidades de envelhecimento foram obtidas a partir da temperatura do pico endotérmico, a partir do módulo elástico E' e a partir da temperatura de transição vítrea e resultaram tanto menores quanto maior o grau de conversão da matriz. Os resultados salientam a importância da seleção adequada das condições de cura para que se possam obter as melhores propriedades destes materiais. A importância dos fenômenos observados é considerada, tendo-se em vista a grande utilização e aplicabilidade das resinas epóxi.