TMA Curves Research Articles

Effects of yttrium addition on thermoplastic formability of Zr-Cu-Ni-Al amorphous alloy under non-isothermal condition

A low-cost and Be-free Zr-based amorphous system with excellent thermoplastic formability has been developed by doping a small amount of Y element. Based on the thermodynamic test data, Y addition can increase the supercooled liquid region of Zr-based amorphous alloy when it is less than 2 at%, leading to a relatively wider temperature range of thermoplastic forming. The compression experimental results reveal that (Zr0.507Cu0.28Ni0.9Al0.123)98.5Y1.5 (ZrY1.5) alloy possesses the largest Dmax value (the maximum diameter of the compressed cylindrical specimen) than other Zr-based amorphous alloys prepared in this study, thereby confirming its superior thermoplastic formability. A lower viscosity can be observed on the TMA curves of ZrY1.5 alloy, suggesting that appropriate Y addition decreases the viscous resistance of amorphous supercooled liquid. However, the more obvious deviation from Vogel–Fulcher–Tamann theoretical model indicates the weak Arrhenius temperature dependence of viscous flow behavior. The parameter ΔTTPF/D*, where ΔTTPF represents the temperature range of thermoplastic forming and D* denotes the fragility index, is found to be an effective indicator for evaluating the thermoplastic formability of the investigated Y addition Zr-based amorphous system. Finally, Zr-based amorphous nanopillar arrays have been successfully fabricated under non-isothermal condition, which further proves that Y addition Zr-based amorphous alloy is a promising candidate for nanomolding material.

Fusion characterization of biomass ash

The ash fusion characteristics are important parameters for thermochemical utilization of biomass. In this research, a method for measuring the fusion characteristics of biomass ash by Thermo-mechanical Analyzer, TMA, is described. The typical TMA shrinking ratio curve can be divided into two stages, which are closely related to ash melting behaviors. Several characteristics temperatures based on the TMA curves are used to assess the ash fusion characteristics. A new characteristics temperature, Tm, is proposed to represent the severe melting temperature of biomass ash. The fusion characteristics of six types of biomass ash have been measured by TMA. Compared with standard ash fusibility temperatures (AFT) test, TMA is more suitable for measuring the fusion characteristics of biomass ash. The glassy molten areas of the ash samples are sticky and mainly consist of K-Ca-silicates.

Thermal expansion behaviour of granites

This paper presents the application of thermomechanical analysis along with thermogravimetric analysis and differential thermal analysis in characterization of thermal expansion behaviour of three granite samples from Czech Republic and two granite samples from India and Italy. The mineralogical composition was carried out by optical microscopy, X-ray diffraction and FTIR spectroscopy. The detailed study has included mainly the effect of granite composition and structure on final thermal expansion and effect of proceeding phase transformation during heat stress of material. The coefficient of thermal expansion showed relatively similar values for all studied granite samples ranged from 35 to 43.10−6 K−1. TMA curves displayed a bit different shapes and characteristics; the final shape probably depends both on the content of quartz and feldspar and on their proportion of the mixture.

Thermal characterization ofn-alkyl maleate-styrene-allyl propionate terpolymers

Thermal characterization of maleic anhydride-styrene-allyl propionate (MA-St-AP) terpolymer and its ester derivatives named as n-alkyl maleate and shown as nPr MA-St-AP, nBu MA-St-AP, nPn MA-St-AP, and nBz MA-St-AP was carried out. The thermal characterization was performed using thermal analysis techniques such as TGA, DTA, DSC, and TMA. Different results were observed between the original terpolymer and its ester derivatives. Thermal stabilities of the terpolymer and its ester derivatives were compared by using various measurements plotted as TGA, DTA, DSC, and TMA curves. The increase in the alcohols' carbon numbers added to the original terpolymer results in ester derivatives with different thermal stability behavior. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 600–604, 2007

Stability studies of ZSM-5/polystyrene and Y/polystyrene composites

Zeolite (ZSM-5 or Y)/polystyrene (PS) composites were obtained by casting evaporation with different proportions (wt/wt) using ethyl acetate as the solvent. The films were characterized by XRD, SEM, water absorption, TG, DSC, and TMA (penetration mode). XRD revealed characteristic peaks of incorporated zeolites. Zeolite microdomains in the polystyrene films were detected by SEM. Water absorption was small, keeping practically constant after 4 h of immersion. TG showed increasing thermal stability of the composites compared to that of the pure PS. DSC revealed no significant changes on glass transition temperatures ( T g). The TMA curves with a 10 mN load showed expansion of composites up to the softening temperature ( T s) and compression of PS film. The T s data did not show important changes, except for 20 wt% zeolite films. TMA results with a 100 mN load did not present any expansion, but the T s values were much higher compared to the polystyrene film.

Physical, mechanical, and thermal properties of PVC/PMMA blends in relation to their morphologies

AbstractThe effect of blending poly (methyl methacrylate) (PMMA) in various proportions with suitably stabilized and plasticized poly (vinyl chloride) (PVC) was studied with reference to their physical, mechanical, and thermal properties. The resulting morphologies of the various blends were also studied to find a suitable explanation of these properties. The physical and mechanical properties of such polyblends revealed a substantial increase in toughness accompanied with unusual increase in modulus and ultimate tensile strength after an initial drop at the initial stages of PMMA incorporation compared to pure reference compound PVC. The toughening effect, however, undergoes a reduction with increasing proportion of PMMA but it never goes below that of pure PVC (reference compound) within the ranges of PMMA incorporation under study. The various polyblends exhibit the two‐stage degradation typical of PVC and all of them possess higher thermal stability as manifested in their characteristic thermograms. The softening characteristics imparted by PMMA were also reflected in their respective TMA curves. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2721–2730, 2004

Microstructure and magnetic properties of Pr 95− xFe xC 5 (15 ≤ x ≤ 65) alloys

This work investigates the range of existence of the D 1-phase in Pr 95− x Fe x C 5 (15≤ x≤65) alloys. A comparative study of the microstructure of this alloy system, in the as-cast state and after annealing at 600 °C, was carried out. In as-cast samples with 15≤ x≤55, besides the presence of Pr grains and large needles, a quite corrosive phase is observed. For x=35 primary Pr 2Fe 17 crystals, surrounded by corrosive phases, were observed. By increasing the Fe-content the population of needle-like particles formed in the intergranular region also increases. TMA curves revealed that D 1 is the major magnetic phase formed in as-cast alloys with 15≤ x≤45 and in annealed alloys with 15≤ x≤35. In both as-cast and annealed samples with 15≤ x≤45, the intrinsic coercivity decreases with the increase of Fe content indicating that the phase D 1 is mainly responsible for the high coercivity in these alloys.

Microstructure and magnetic properties of Nd 95− xFe xC 5 (15⩽ x⩽65) alloys

This work investigates the range of existence of the D 1-phase in Nd 95− x Fe x C 5 (15⩽ x⩽65) alloys. A comparative study of the microstructure of this alloy system, in the as-cast state and after annealing at 600°C, was carried out. In as-cast samples with 15⩽ x⩽45, besides the presence of Nd grains and large needles, quite corrosive Nd-based carbides are formed. According to TMA curves, D 1 is the major magnetic phase formed in this composition range. For x>45 primary Nd 2Fe 17 crystals, surrounded by corrosive Nd-C phases, were observed. By increasing the Fe-content the population of needle-like particles formed in the intergranular region also increases. In both as-cast and annealed samples with 15⩽ x⩽45, the intrinsic coercivity decreases with the increase of Fe content indicating that the phase D 1 is mainly responsible for the high coercivity in these alloys.

Structural Characterization of Wool by Thermal Mechanical Analysis of Yarns

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. The TMA curves show that fiber extension causes significant structural modification of the wool samples. In particular, melting of the α-form crystallites in native wool can be detected at around 215°C, with supercontraction prior to effective crystallite melting. But extended wool yarn shows no thermal mechanical event corresponding to melting of the β-form crystallites. Extended wool has a thermal mechanical behavior similar to that of silk yarn.

Structure and properties of tussah silk fibers graft‐copolymerized with methacrylamide and 2‐hydroxyethyl methacrylate

Tussah silk fibers were graft-copolymerized with methacrylamide (MAA) and 2-hydroxyethyl methacrylate (HEMA) in aqueous media, using a chemical redox system as an initiator. High weight gain values were obtained with both grafting agents (up to 175%). The extent of homopolymerization was negligible for the MAA grafting system over the entire range of monomer–silk ratios examined, while polymer deposition on the fiber surface occurred when the HEMA–silk ratio exceeded 0.5% (w/w). The moisture content of poly(MAA)-grafted silk fibers was enhanced by grafting. Breaking load, elongation at break, and energy decreased at low weight gain (0–20%) and then remained rather constant. The DSC curves of poly(MAA)-grafted silk showed a new endotherm at about 280°C, due to the melting of poly(MAA) chains. The loss modulus peak of poly(HEMA)-grafted silk fibers broadened and shifted to a lower temperature, showing a tendency to split into two peaks at high weight gain. On the other hand, grafting with poly(MAA) induced a noticeable upward shift of the loss peak. The TMA curves showed that grafting with poly(MAA) resulted in a higher extent of fiber contraction from room temperature to about 250°C. Moreover, the intensity of the final contraction step at about 350°C decreased with increasing weight gain and shifted to a lower temperature. The Raman spectra of grafted fibers were characterized by overlapping of the characteristic lines of both silk fibroin and polymer, the latter showing an intensity proportional to the amount of weight gain. Among the conformationally sensitive vibrational modes of tussah silk fibroin, the amide III range was significantly modified by grafting with both poly(MAA) and poly(HEMA). © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1393–1403, 1998

Structure and properties of tussah silk fibers graft-copolymerized with methacrylamide and 2-hydroxyethyl methacrylate

Tussah silk fibers were graft-copolymerized with methacrylamide (MAA) and 2-hydroxyethyl methacrylate (HEMA) in aqueous media, using a chemical redox system as an initiator. High weight gain values were obtained with both grafting agents (up to 175%). The extent of homopolymerization was negligible for the MAA grafting system over the entire range of monomer–silk ratios examined, while polymer deposition on the fiber surface occurred when the HEMA–silk ratio exceeded 0.5% (w/w). The moisture content of poly(MAA)-grafted silk fibers was enhanced by grafting. Breaking load, elongation at break, and energy decreased at low weight gain (0–20%) and then remained rather constant. The DSC curves of poly(MAA)-grafted silk showed a new endotherm at about 280°C, due to the melting of poly(MAA) chains. The loss modulus peak of poly(HEMA)-grafted silk fibers broadened and shifted to a lower temperature, showing a tendency to split into two peaks at high weight gain. On the other hand, grafting with poly(MAA) induced a noticeable upward shift of the loss peak. The TMA curves showed that grafting with poly(MAA) resulted in a higher extent of fiber contraction from room temperature to about 250°C. Moreover, the intensity of the final contraction step at about 350°C decreased with increasing weight gain and shifted to a lower temperature. The Raman spectra of grafted fibers were characterized by overlapping of the characteristic lines of both silk fibroin and polymer, the latter showing an intensity proportional to the amount of weight gain. Among the conformationally sensitive vibrational modes of tussah silk fibroin, the amide III range was significantly modified by grafting with both poly(MAA) and poly(HEMA). © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1393–1403, 1998

The effects of mechanical grinding on the structural and magnetic properties of Dy 2Fe 14B 1- xC x alloys

The effects of mechanical grinding on the magnetic and structural properties and on the phase formation of Dy-Fe-(B, C) alloys have been studied. X-ray diffraction, Mössbauer spectroscopy and thermomagnetic analysis show that there is a decomposition of the Dy 2Fe 14(B, C) phase accompanied by the formation of α-Fe. In addition, for boron rich alloys magnetic phases which are revealed in the TMA curves disappear during the measurement. The magnetic measurements showed a gradual fall in coercivity at longer grinding times. The magnetisation falls initially and then rises, due to the amorphisation and decomposition of the original phases and the formation of the α-Fe.

Physical properties of 2‐hydroxyethyl methacrylate‐grafted silk fibers

AbstractThis paper deals with the physical properties of silk fibers grafted with 2‐hydroxyethyl methacrylate (HEMA). Both tensile strength and elongation measured in the dry and wet states gradually decreased with increasing weight gain. The initial modulus of the grafted silk fibers in the dry state sharply increased in the weight gain range of 0–16%, then decreased to a lower value than the reference untreated sample. The refractive indices parallel and perpendicular to the fiber axis decreased, though the former showed a steeper slope. Accordingly, birefringence and isotropic refractive index also decreased, suggesting a lower degree of crystallinity and molecular orientation of grafted silk fibers. DSC, TMA, and TGA curves of the HEMA‐grafted silk fibers indicated an increased higher thermal stability of silk fibers due to the HEMA grafting. The dynamic mechanical measurements showed that the thermally induced molecular movement of both amorphous and crystalline domains of silk fibers was enhanced by HEMA grafting. X‐ray diffraction curves, however, implied that the crystalline structure of the silk fibroin remained unchanged regardless of HEMA polymerization. The introduction of HEMA polymer in silk fibers was evidenced by the infrared spectra, exhibiting the absorption bands characteristic of either the grafted HEMA polymer and the fibroin molecules with ordered β structure. © 1993 John Wiley & Sons, Inc.

Elasticity of α-β quartz measured by TMA

The α -β transformation at 573°C is used for the identification by DSC of quartz in mineral mixtures. This transformation can also be observed in TMA curves due to the difference in thermal expansion of the two quartz modifications. In this study a special accessory for bending measurements has been used to determine the Young's modulus by bending within the transformation region. Oriented cuts of natural and synthetic quartz crystals parallel and perpendicular to the c-axis were measured. The results proved that this modulus is larger in the low-temperature than in the high-temperature form. During the α-β transformation, a significant change in the elastic behavior takes place: the quartz crystal becomes “softer” (H.G. Wiedemann, R. Riessen and A. Boller, in A.T. Riga and M. Naeg (Eds.) Material Characterization by Thermochemical Analysis, American Society for Testing and Materials, Philadelphia, 1991, p. 84). A pronounced difference in the modulus was found for quartz samples cut 45° at an angle to the hexagonal c-axis, the optimum direction for oscillator quartz.

Thermal studies on thenardite

Two natural thenardite (Na 2SO 4) single crystals, e.g. from Wadi El-Natron and Searles Lake, and one synthetic thenardite were studied by combined thermal techniques (e.g. DTA, TG, TMA, TOA and MS) mainly with regard to the occurring phase transitions and in order to determine the reason for the observed differences in the transition behaviour of the studied samples. The synthetic thenardite which was chemically very pure (especially free of water) showed its phase transitions during heating and cooling for be much closer together and (1st heating) a little shifted to higher temperatures compared with the natural samples which contained remarkable amounts of water and carbon, respectively. Simultaneously with the phase transitions, both natural samples lost some weight, showed very sharp, clear changes in the TMA curves and released water and CO 2 during the first heating. The thermal transitions started at distincts spots within the single crystals, easily recognizable at different interference colours when using crossed nicols in the thermomicroscope. These spots were interpreted as domains with a certain crystal physical defect character which partly enables earlier phase transitions at the defect domains. The spots seem to include very small particles of mirabilite, Na 2SO 4 10 H 2O, or carbon flakes which are the reason for the defect domains and the observed release of water and CO 2.

Stress–strain behavior, hardness, and thermomechanical properties of butadiene–styrene block copolymers as a function of processing technique

AbstractStress–strain properties of star‐shaped butadiene–styrene block copolymers were carried out on extruded sheet and injection molded samples. A striking “plastic‐like” behavior was observed during the first extension, with a marked yield point, a drawing process, and an important hysteresis. These phenomena disappeared on the second elongation, but annealing below the polystyrene glass transition temperature gave again the initial behavior. A marked processing technique dependence was observed in the stress–strain experiments. An important variation in hardness was observed before and after stretching, and annealing experiments permitted the study of hardness recovery. A logarithmic relation between recovered hardness and the annealing time at constant temperature was deduced from the experimental data. Thermomechanical analysis curves show singular transitions between 20° and 85°C, which disappear on stretching. An important discrepancy occurs in TMA curves of extruded and injected samples. A comparison is made of thermomechanical behavior of linear and star‐shaped SBS block copolymers. A modified model is proposed for a reversibly deformable structure composed of polybutadiene and polystyrene linked ends at the diffuse interfacial region between the PS domains and the PB matrix.

Thermal Analysis of Nomex® and Kevlar® Fibers

DTA, TG, and TMA curves of commercial Kevlar® 49 and Nomex® fibers have been used to assess their behavior at high temperatures. The fibers lost absorbed water around 100°C, and a glass transition was reflected in the DTA and TMA curves in the region of 300°C. Difficulties in the interpretation of DTA and TMA curves in the glass-transition region and in the assignments of Tv‘s for these high-performance fibers are discussed. Whereas Kevlar 49 showed both a crystalline melting point (560°C) and a sharp endothermal thermal decomposition (590°C), Nomex showed only the latter (440°C) and no evidence of melting from the DTA curves. The endothermal decomposition peaks apparently correspond to “polymer melt temperatures” reported for related materials, and correlate well with the TG and TMA features. During thermal analysis of Kevlar 49, oxidation occurs more readily than thermal decomposition, but the latter predominates for Nomex. Differences between dyed and undyed Nomex were due to differences in yarn constitution.

Thermal Shrinkage of Cold-Drawn Polypyromellitimide

This paper deals with the mechanical dispersions and the thermal shrinkage of cold-drawn polypyromellitimide in relation to its structure. Three mechanical dispersions were found in our measurements. The lowest one found around 80°C has been ascribed to the translational movement of chain segments against their intermolecular interaction. The activation energy of this molecular motion was about 10kcal/mol, obtained from the analysis of TMA curves. The second and the third ones were found at around 200°C and 360°C, respectively. Both of them were influenced by annealing and were strengthened by cold-drawing. The molecular motions of these mechanical dispersions were not clarified yet. However, it was certain that they are related to the main chain motion, from the analysis of thermal shrinkage of cold-drawn samples. The activation energies of these two processes were about 25Kcal/mol and 33Kcal/mol, respectively.