Showing papers on "Thermomechanical analysis published in 2001"
TL;DR: In this article, the thermal expansion coefficients (CTE) of a 50-vol.% SiCp/Al composite prepared by a squeeze casting route were measured and examined from room temperature to 600°C using thermomechanical analysis (TMA) method.
85 citations
TL;DR: In this paper, a soluble polyimide prepared from 7,7′-bis(4-aminophenoxy)-4,4, 4′,4′-tetramethyl-2,2′-spirobichroman and 4,4-hexafluoroisopropylidenediphthalic anhydride was mixed with organo-modified montmorillonite or synthetic mica in N,N-dimethylacetamide.
Abstract: A soluble polyimide prepared from 7,7′-bis(4-aminophenoxy)-4,4,4′,4′-tetramethyl-2,2′-spirobichroman and 4,4′-hexafluoroisopropylidenediphthalic anhydride was mixed with organo-modified montmorillonite or synthetic mica in N,N-dimethylacetamide. The content of the clay minerals was 1, 2, and 4 wt %, respectively. Transparent, flexible, and tough films could be cast from the hybrid solutions. The hybrid films were characterized with wide-angle X-ray scattering (WAXS), transmission electron microscopy, thermomechanical analysis, thermogravimetric analysis, and differential scanning calorimetry. The WAXS results revealed that the montmorillonite was dispersed more homogeneously than the synthetic mica in the polyimide matrix. In both polyimide/clay hybrids the addition of clay caused thermal expansion coefficients to decrease, and the thermal stability was slightly enhanced. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2067–2072, 2001
82 citations
TL;DR: It is concluded that volume expansion of compressed PDLA tablets is related to the glass transition behaviour, originates from water-induced and thermally stimulated shape memory behaviour and is therefore highly dependent on the molecular weight of PDLA.
69 citations
TL;DR: The changes occurring during the heating of a borosilicate glass have been investigated by differential thermal analysis, dilatometric analysis and thermomechanical analysis as discussed by the authors, and a value of 290 kJmol −1 was obtained for the activation energy for viscous flow, where the precipitation of cristobalite was identified by X-ray diffraction.
69 citations
TL;DR: In this article, a fragmentary investigation of the heat capacity and thermal expansion coefficient of single crystals of high-purity silicon is reported and compared with the entire body of data on these properties available to date.
Abstract: Fragmentary investigations of the heat capacity and of the thermal expansion coefficient of single crystals of high-purity silicon are reported. The results of these investigations are compared with the entire body of data on these properties available to date. Generalized equations expressing the heat capacity and thermal expansion coefficient of silicon as functions of temperature are obtained for the temperature ranges of 298–1690 and 100–1400 K, respectively. The Debye temperature of crystalline silicon and the root-mean-square dynamic displacement of atoms from the equilibrium position in its crystal lattice are calculated using the available data on thermal expansion.
64 citations
TL;DR: The results showed that expansion continued formost of the materials over several days, until a steady state of the tablet and its physical properties was reached, and the amount of expansion was different for the tableting materials used.
Abstract: The purpose of this study was to complete information on elastic recovery during a compression cycle by measuring the expansion of the tablet after ejection, and thus, to measure the whole recovery process, which means the time dependency of elastic recovery. Two methods were applied: manual measurement by a micrometer screw, and a continuous measurement by thermomechanical analysis, always at a constant temperature and humidity. Elastic recovery of the tablet continued after ejection from the die, and the amount of expansion was different for the tableting materials used. The results showed that expansion continued for most of the materials over several days, until a steady state of the tablet and its physical properties was reached. The extent and the profiles of the elastic recovery curves were different for the tableting materials dicalcium phosphate dihydrate, carrageenan, microcrystalline cellulose, cellulose acetate, hydroxypropyl methylcellulose and theophylline monohydrate. There were slight differences between both the methods used. The profiles of the materials could be related to some properties of the materials.
60 citations
TL;DR: In this article, a cycloaliphatic triepoxide, 1,1-bis(2′,3′-epoxycyclohexyloxymethyl)-3,4-EPoxycycloelectric hexahydro-4-methylphthalic anhydride with 1,3,5-triethylhexahydroid-s-triazine as a curing accelerator was used.
Abstract: A novel cycloaliphatic triepoxide, 1,1-bis(2′,3′-epoxycyclohexyloxymethyl)-3,4-epoxycyclohexane (II), and its precursor, 1,1-bis(2′-cyclohexenyloxymethyl)-3-cyclohexene, were synthesized. Their chemical structures were confirmed with IR spectroscopy, elemental analysis, and 1H NMR spectroscopy. II was easily cured with hexahydro-4-methylphthalic anhydride with 1,3,5-triethylhexahydro-s-triazine as a curing accelerator. The physical properties of the cured product were examined with thermomechanical analysis, thermogravimetric analysis, and dynamic mechanical analysis. Compared with the commercial diepoxide ERL-4221 under the same curing conditions, the cured product based on II showed a much higher glass-transition temperature (198 °C), a higher crosslinking density (2.08 × 10−3 mol/cm3), and a lower coefficient of thermal expansion [6.2 × 105(/°C)]. II may become a promising candidate material for modern microelectronic packaging. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2799–2804, 2001
54 citations
TL;DR: In this article, the effect of cooling rate on the density of the Pd 40Ni10Cu30P20 bulk metallic glass was investigated over the cooling rate range from 0.63 to 500 K/s.
Abstract: The effect of cooling rate on the density of the Pd 40Ni10Cu30P20 bulk metallic glass~BMG! have been investigated by over the cooling rate range from 0.63 to 500 K/s. The cooling rate dependence of density, microhardness and thermal properties of the BMG is determined. Based on the thermal-expansion coefficients measured in the amorphous and supercooled liquid states, respectively, it is deduced that the density of the BMG in the ‘‘ideal’’ state approaches that of its crystalline counterpart. The effect of cooling rate on the density is discussed in terms of structural relaxation.
53 citations
TL;DR: In this article, a series of PMR polyimides based on substituted benzidines are examined and compared to the state-of-the-art PMR-15, using thermal mechanical analysis and TGA/FTIR/MS techniques.
52 citations
42 citations
IBM1
TL;DR: In this article, the effect of nonconducting fillers on the thermomechanical properties of modified anisotropic conductive adhesive (ACA) composite materials and the reliability of flip chip assembly on organic substrates using modified ACA composite materials were investigated.
Abstract: We investigated the effect of nonconducting fillers on the thermomechanical properties of modified anisotropic conductive adhesive (ACA) composite materials and the reliability of flip chip assembly on organic substrates using modified ACA composite materials. For the characterization of modified ACAs composites with different content of nonconducting fillers, dynamic scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and thermomechanical analysis (TMA) were utilized. As the nonconducting filler content increased, CTE values decreased and storage modulus at room temperature increased. In addition, the increase in the content of filler brought about the increase of T/sub g/(DSC) and T/sub g/(TMA). However, the TGA behaviors stayed almost the same. Contact resistance changes were measured during reliability tests such as thermal cycling, high humidity and temperature, and high temperature at dry condition. The reliability results were significantly influenced by CTEs of ACA materials, especially at the thermal cycling tests. Results showed that flip chip assembly using modified ACA composites with lower coefficients of thermal expansion (CTEs) and higher modulus by loading nonconducting fillers exhibited better contact resistance behavior than conventional ACAs without nonconducting fillers.
TL;DR: Close agreement was found between the response of dentine to thermal changes as observed by moiré interferometry and that detected by thermomechanical analysis.
Abstract: An investigation of the adaptation of dentine to temperature variation was conducted with the aid of digital moire interferometry and thermomechanical analysis. The moire interferometric patterns provided direct evidence of two major phases of thermally involved deformation in dentine. An initial phase of expansion was followed by contraction at higher temperatures. Significant gradients in thermal strain and the coefficient of thermal expansion were identified. Close agreement was found between the response of dentine to thermal changes as observed by moire interferometry and that detected by thermomechanical analysis. This study highlights the biological adaptation of dentine to thermal variations.
TL;DR: In this paper, the use of the thermal lens technique for investigating the thermal properties of polymers as a function of temperature is discussed, and the experimentally determined thermal lens parameters can be used to locate the glass transition in polymers.
Abstract: In this article we discuss the use of the thermal lens technique for investigating the thermal properties of polymers as a function of temperature. It is also discussed how the experimentally determined thermal lens parameters can be used to locate the glass transition in polymers. The methodology is tested using a solution casted films of poly(vinyl chloride) as a testing sample. A comparison with conventional differential scanning calorimetry data is made. It is proposed that the current transient thermal lens methodology, with minor changes in its experimental configuration, could be adapted to develop a new methodology called differential thermal lens scanning especially designed for the investigation of the phase transitions in polymers. It is shown that this new methodology could be equally used for the measurement of the thermal expansion coefficient, above and below the glass transition.
TL;DR: In this article, the structural, crystalline, thermal, morphological, and mechanical properties of isotactic polypropylene (iPP) functionalized by lower energy ultraviolet (UV) irradiation are studied by means of infrared spectroscopy (IR), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), thermogravimetry, thermomechanical analysis (TMA), polariscope and mechanical measurements.
Abstract: The structural, crystalline, thermal, morphological, and mechanical properties of isotactic polypropylene (iPP) functionalized by lower energy ultraviolet (UV) irradiation are studied by means of infrared spectroscopy (IR), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), thermogravimetry (TG), thermomechanical analysis (TMA), polariscope, and mechanical measurements. After the UV irradiation in less than a few hours, the oxygen containing polar groups have been introduced onto iPP chains. DSC analysis shows that a new melting peak is observed around 150°C for the UV irradiated iPP, indicating that there is a α-phase to β-phase transition during UV irradiation process. Under polariscope, the morphology of the UV irradiated iPP is changed, and the deformed α-phase morphology can be observed. DSC and WAXD analysis reveal for the crystallinity of the UV-irradiated iPP increase with UV time, but the relative level and the order of β-phase increase and then decrease with increasing UV time. Under the controlled UV time, the thermomechanical deformation of iPP decrease, and the initial and final thermal degradation temperature of iPP rises up by 70 to 125°C higher, respectively, indicating that the UV-irradiated iPP has higher thermal stability than the non-UV irradiated iPP. The tensile and impact strength, the elongation at break, and the Young's modulus of the UV-irradiated iPP are enhanced, exhibiting the toughened and strengthened effects. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1456–1466, 2001
TL;DR: In this paper, the authors used a highly isospecific metallocene catalyst system based on rac -Me 2 Si(2-ethyl,4-phenyl,1-indenyl) 2 ZrCl 2, in the homogeneous and heterogeneous forms, activated by methylaluminoxane (MAO).
TL;DR: In this article, the authors investigated thermoplastic interpenetrating polymer networks (t-IPNs) prepared by melting and pressing of crystallizable polyurethane (CPU) and styrene/acrylic acid random copolymer (S/AA) in wide ranges of composition.
TL;DR: In this paper, the authors investigated the thermoelastic-plastic deformations of internal heat-generating tubes by considering the temperature dependence of the thermal conductivity coefficient, Young's modulus, and the coefficient of thermal expansion.
Abstract: The thermoelastic-plastic deformations of internal heat-generating tubes are investigated by considering the temperature dependence of the thermal conductivity coefficient, Young's modulus, the coefficient of thermal expansion, and the yield limit of the material. A model describing the elastic-plastic behavior of the tube is developed. The model consists of a system of two second-order ordinary differential equations and a first-order ordinary differential equation involving nonlinear temperature-dependent coefficients. The computer solution of the model is obtained, and the results are compared with the analytical solution that assumes constant thermomechanical properties. It is found that the difference between the two solutions becomes significant in the regions of high temperatures.
TL;DR: In this paper, a thermomechanical analysis of yarns in a tensile mode is used to characterize wool fibers modified to show the β-crystal form in comparison with native untreated wool retaining the α-crystals form.
Abstract: A thermomechanical analysis of yarns in a tensile mode is used to characterize wool fibers modified to show the β-crystal form in comparison with native untreated wool retaining the α-crystal form....
TL;DR: In this article, the role of fiber morphology in a thermal point-bonding operation was investigated, where polypropylene fibers were spun to produce fibers with a wide range of structure, keeping the diameter same.
TL;DR: In this paper, the relative efficiency of different types of fillers e.g., phenolic resin, carbon black and carbon black plus phenolic resins in nitrile rubber vulcanizates for improvement of physico-mechanical properties, resistance to swelling in oil/fuel and thermal stability has been studied.
Abstract: Relative efficiency of different types of fillers e.g., phenolic resin, carbon black and carbon black plus phenolic resin hybrid system in nitrile rubber vulcanizates for improvement of physico-mechanical properties, resistance to swelling in oil/fuel and thermal stability has been studied. The hybrid system was always found to offer maximum benefit in strength and dynamic mechanical properties coupled with higher percent of (a) retention of physical properties due to aging and (b) swelling resistance in oil or fuel. Both thermogravimetric analysis (TGA) as well as thermomechanical analysis (TMA) reflect much better thermal stability for the combined filler system compared to the vulcanizates containing either phenolic resin or carbon black.
TL;DR: In this article, the thermal, thermomechanical and thermal-dielectric properties of polyurethane blends based on branched polymer polyol (PUR) and styrene-acrylonitrile (SAN) copolymer were studied by differential scanning calorimetry (DSC), TMA, thermally stimulated depolarization currents (TSDC) techniques and dielectric relaxation spectroscopy (DRS).
TL;DR: The thermal history of carbon-fiber nylon-6 matrix composite was evaluated by measuring the electrical resistance in the fiber direction during heating, as the resistance was affected by the degree of crystallinity and the thermal oxidative degradation as discussed by the authors.
TL;DR: In this article, mode mismatched thermal lens spectrometry is applied to determine the thermal and optical properties of polycarbonate as a function of temperature, and the results showed that the temperature dependence of the signal amplitude of the thermal lens provided a better definition in locating the glass transition compared to the differential scanning calorimetry data.
Abstract: In this paper, mode mismatched thermal lens spectrometry is applied to determine the thermal and optical properties of polycarbonate as a function of temperature. The focus of the experiments was in the temperature range between 120 °C and 170 °C, where the sample glass transitions occurs. In order to validate and evaluate the sensitivity of the proposed method we have also carried out conventional differential scanning calorimetry measurements. The results showed that the temperature dependence of the signal amplitude of the thermal lens provided a better definition in locating the glass transition compared to the differential scanning calorimetry data. In addition, a sharp decrease in the thermal diffusivity values at the beginning of the sample glass transition was observed. According to the Debye model, this change was attributed to the variation of the sample elastic constant throughout the glass transition. Finally, we propose this procedure, called the differential thermal lens temperature scanning approach, as a new method for the investigation of phase transitions in transparent polymers.} \fnm{3}{Author to whom correspondence should be addressed.
TL;DR: In this article, a triblock polyamic acid was synthesized from the reaction of amine-terminated polystyrene with 4,4′-oxydianiline and pyromellitic dianhydride in N-methyl-2-pyrrolidone.
31 May 2001-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the authors investigated the viscous-flow behavior of bulk amorphous Zr 55 Al 10 Ni 5 Cu 30 alloys and confirmed that the relative displacement under compression depends strongly upon the state of amorphocity of the sample.
Abstract: The viscous-flow behavior of bulk amorphous Zr 55 Al 10 Ni 5 Cu 30 alloys has been investigated. Differential scanning calorimetry (DSC) experiments gave the activation energy for crystallization and thermal stability range of the supercooled liquid as 192.4 kJ mol −1 and 81 K, respectively. Thermomechanical analysis (TMA) experiments showed the effective viscosity decreasing monotonically with increasing temperature, approaching a constant value above the steady-state viscous-flow temperature. We confirmed that the relative displacement under compression depends strongly upon the state of amorphocity of the sample. By examining the relationship between the displacement, Δ L , and applied stress, P , (Δ L / P ) and temperature, important information about viscous-flow forming is obtained. For secondary working with this material, we think that applied stress level and the values of the temperature at each stress level are very useful information. In addition, it is believed that these findings are relevant for the understanding of the effect of indentation on the bulk viscous flow.
TL;DR: In this article, a thermomechanical analyzer (TMA) equipped with a quartz compression probe immersed in water was used to measure polysaccharide hydrogels containing ca 98% water.
Abstract: Application of thermomechanometry to the measurement of hydrogels containing a large amount of water was carried out by static and dynamic methods. A thermomechanical analyzer (TMA) equipped with a quartz compression probe immersed in water was used. Polysaccharide hydrogels containing ca 98% water were measured. Creep of hydrogels in water was analyzed in a stress range from 1.04⋅103 to 5.2⋅103 Pa and loading rate from 0.3⋅103 to 3.0⋅103 Pa min−1.Stress relaxation was measured in compressed ratio range from 0.02 to 0.45 m m−1 and in compressing rate was 0.09 to 0.15 m m−1 min−1. Dynamic viscoelasticity was measured by TMA when dynamic Young’s modulus which was larger than 1⋅104 Pa in frequencies ranging from 0.02~0.2 Hz.
TL;DR: In this article, the thermal properties of barium-iron-metaphosphate glass were investigated by means of differential scanning calorimetry (DSC) and thermal mechanical analysis (TMA).
TL;DR: In this paper, the application of modulated temperature programs to thermomechanical analysis can be used to separate the reversible nature of thermal expansion from irreversible deformation arising from creep under the applied load or changes in dimensions due to relaxation of orientation.
Abstract: The application of modulated temperature programs to thermomechanical analysis can be used to separate the reversible nature of thermal expansion from irreversible deformation arising from creep under the applied load or changes in dimensions due to relaxation of orientation. The effect of experimental variables and calibration are described. Modulated temperature TMA allows the time-dependent nature of thermal expansivity to be studied. Measurements made under compression afford a means of measuring the thermal expansivity of soft specimens independently of initial load. Application of these principles to scanning thermal microscopy leads to a novel method of generating image contrast based upon local changes thermal expansivity of a specimen.
TL;DR: In this article, a copolyimide thin film, which has low-level stress and stress relaxation induced by water sorption was characterized for potential applications as an encapsulant, a stress-relief buffer, and in interlayer dielectrics.
Abstract: Copolyimide thin film, which has low-level stress and stress relaxation induced by water sorption, was characterized for potential applications as an encapsulant, a stress-relief buffer, and in interlayer dielectrics. The polyimides examined were poly(p-phenylene pyromellitimide) (PMDA-PDA) and poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA) as well as their random copolyimides with various compositions. These copolyimide films exhibited good combinations of physical and mechanical properties with low thermal expansion coefficients, residual stress, and moisture-induced stress-relaxation behavior by appropriately selecting the ratios of the dianhydride component. For these polyimides, the residual stress increased in the range of -8.1-7.5 MPa, whereas stress relaxation induced by water uptake decreased in the range of 10.3-4.7 MPa with increasing BPDA contents, respectively. The major factor in determining the magnitude of the stress behavior induced by both the thermal mismatch and water uptake in films should be the morphological factors such as chain rigidity, chain orientation, crystallinity, and microvoids. Their morphological structures were examined by wide angle X-ray diffraction and a prism coupler, and the thermal properties were measured using a dynamic mechanical thermal analyzer as well as thermomechanical analysis. Overall, the candidate for the low level stress buffer application from the PMDA/BPDA-PDA copolyimide was the 30/70 (= PMDA/BPDA in molar ratio) copolyimide. This copolyimide showed no residual stress after curing at 400 °C and relatively insensitive stress relaxation to ambient humidity.
TL;DR: In this article, a mixture of polystyrene-block-polybutadiene-blockpolystyrene (SBS) triblock copolymers with syndiotactic poly styrene (PSsyn) has been performed in a Brabender mixer above the glass transition temperature of the triblock Copolymer but below the melting point of PSsyn.
Abstract: Blending of polystyrene-block-polybutadiene-block-polystyrene (SBS) triblock copolymers with syndiotactic polystyrene (PSsyn) has been performed in a Brabender mixer above the glass transition temperature of the triblock copolymer but below the melting point of PSsyn. The presence of a large excess of amorphous SBS (at least 70 wt.-%) as well as of the amorphous PSsyn phase (about 60 wt.-%, also above its Tg) allowed the easy mixing of the components. In contrast, the presence of unmelted PSsyn crystallites affects both the final morphology of the blend as well as its dynamic behavior. Indeed, according to the dynamic thermomechanical analysis (DMTA) data it is possible to suggest that such solid particles act to reinforce the overall blend structure (as in composite materials filled with inorganic solid particles). Similar behavior is also observed for the SBS copolymer alone below the Tg of the styrene blocks, Tg (PS). This conclusion is supported by both the compatibility of the blends, and the thermal and dynamic thermomechanical behavior at T > Tg (PS) as investigated by means of Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and DMTA. The results obtained are tentatively compared with those of similar blends obtained from toluene solution.