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In an effort to select the best possible medical grade of polyether ether ketone (PEEK) for active medical implants application, it was necessary to inspect surface thermodynamic properties of different grades and correlate with self-bonding (autohesion) strength. Autohesion is the process of choice for encapsulating active medical implants made of PEEK. Temperature modulated DSC was used to investigate crystallinity and thermal events of range of medical grade PEEK (semi-crystalline, amorphous, semi-crystalline with amorphous surface, minerals and black masterbatch filled). Lab shear test was used to measure autohesive forces between PEEK samples pressed at moderate temperature (200 °C) and pressure. Samples with higher mobile amorphous region (MAF) and lower degree of crystallinity (Wc) resulted in higher autohesivce bonding strength. However, semi crystalline PEEK with surfaces that showed high MAF and lowWcresulted in higher autohesive bonding strength when compared with crystalline samples. The presence of fillers (minerals and black masterbatch) in the crystalline structure doubled the autohesive bonding strength values of the semi-crystalline sample. The presence of large crystalline region and a larger portion of the rigid amorphous region acted negatively on autohesion strength. Semi-crystalline PEEK with a special manufacturing procedure to produce amorphous surface produced the best choice among the PEEK grades. This grade have the desired thermodynamical properties in the bulk while exhibiting best surface adhesion strength. [ABSTRACT FROM PUBLISHER]

Highlights: [•] [Co(AIP)(BPY)0.5·H2O] n ·2nH2O was synthesized. [•] It is characterized by powder X-ray diffraction, FT-IR spectra. [•] Molar heat capacities of [Co(AIP)(BPY)0.5·H2O] n ·2nH2O were measured. [•] Its thermodynamic parameters (entropy and enthalpy) were derived. [•] Its thermal decomposition mechanism for the material was investigated. [ABSTRACT FROM AUTHOR]

A novel metal-organic frameworks Co(3,5-PDC)(HO) (CoMOF, 3,5-PDC = pyridine-3,5-dicarboxylic acid) has been synthesized hydrothermally and characterized by single-crystal XRD and FT-IR spectra. The thermal stability and the decomposition mechanism of CoMOF were investigated by thermogravimetry-mass spectrometry, and a two-stage shape curve of mass loss was observed. Moreover, the low-temperature molar heat capacities were measured by temperature-modulated differential scanning calorimetry for the first time. The thermodynamic parameters such as entropy and enthalpy relative to reference temperature 298.15 K were derived based on the molar heat capacity data. [ABSTRACT FROM AUTHOR]

A 3D supramolecule (HO)[Cu(2,6-pdc)]·HO (pdc = pyridinedicarboxylate) has been solvothermally synthesized and characterized by X-ray powder diffraction and FT-IR spectrum. The thermal decomposition characteristics of the complex were investigated by thermogravimetric analysis, which revealed a three-step mass loss process. The low-temperature molar heat capacities of crystalline (HO)[Cu(2,6-pdc)]·HO were measured by temperature-modulated differential scanning calorimetry for the first time. A phenomenon of glass transition was observed. The thermodynamic parameters such as entropy and enthalpy relative to 298.15 K were calculated based on the above molar heat capacity data. [ABSTRACT FROM AUTHOR]

The low-temperature molar heat capacity of crystalline Ni(btz)(DMA)(NO) (1) (btz = benzotriazolate; DMA = N,N′-dimethylacetamide) was measured by temperature-modulated differential scanning calorimetry for the first time. The thermodynamic parameters such as entropy and enthalpy relative to reference temperature 298.15 K were obtained based on the above molar heat capacity data. The compound was synthesized by solvothermal method and characterized by powder X-ray diffraction and FT-IR spectra. Moreover, the thermal stability and the decomposition mechanism of Ni(btz)(DMA)(NO) were investigated by thermogravimetry (TG) analysis under air atmosphere from 300 to 873 K. The experimental results through TG measurement demonstrate that the compound has a two-stage mass loss in air flow. [ABSTRACT FROM AUTHOR]

Two metal-organic frameworks (MOFs) of M(HBTC)(4,4′-bipy)·3DMF [M = Ni (for 1) and Co (for 2); HBTC = 1,3,5-benzenetricarboxylic acid (1,3,5-BTC); 4,4′-bipy = 4,4′-bipyridine; DMF = N, N′-dimethylformamide] were synthesized by a one-pot solution reaction and a solvothermal method, respectively, and characterized by powder X-ray diffraction and FT-IR spectra. The low-temperature molar heat capacities of M(HBTC)(4,4′-bipy)·3DMF were measured by temperature-modulated differential scanning calorimetry (TMDSC) for the first time. The thermodynamic parameters such as entropy and enthalpy relative to reference temperature 298.15 K were derived based on the above molar heat capacity data. Moreover, the thermal stability and the decomposition mechanism of M(HBTC)(4,4′-bipy)·3DMF were investigated by thermogravimetry analysis (TGA). The experimental results through TGA measurement demonstrate that both of the two compounds have a three-stage mass loss in air flow. [ABSTRACT FROM AUTHOR]

One-three-dimensional metal-organic frameworks Mg(CHO)(CHNO) (MgNDC) has been synthesized solvothermally and characterized by single crystal XRD, powder XRD, FT-IR spectra. The low-temperature molar heat capacities of MgNDC were measured by temperature modulated differential scanning calorimetry (TMDSC) over the temperature range from 205 to 470 K for the first time. No phase transition or thermal anomaly was observed in the experimental temperature range. The thermodynamic parameters of MgNDC such as entropy and enthalpy relative to reference temperature of 298.15 K were derived based on the above molar heat capacities data. Moreover, the thermal stability and decomposition of MgNDC was further investigated through thermogravimetry (TG)-mass spectrometer (MS). Three stages of mass loss were observed in the TG curve. TG-MS curve indicated that the oxidative degradation products of MgNDC are mainly HO, CO, NO, and NO. [ABSTRACT FROM AUTHOR]

three-dimensional lithium-based metal-organic framework Li(2,6-NDC) (2,6-NDC = 2,6-naphthalene dicarboxylate) has been synthesized solvothermally and characterized by X-ray powder diffraction, elemental analysis, FT-IR spectroscopy, thermogravimetry and mass spectrometer analysis (TG-MS). The framework has exceptional stability and is stable to 863 K. The thermal decomposition characteristic of this compound was investigated through the TG-MS from 293 to 1250 K. The molar heat capacity of the compound was measured by temperature modulated differential scanning calorimetry (TMDSC) over the temperature range from 195 to 670 K for the first time. The thermodynamic parameters such as entropy and enthalpy versus 298.15 K based on the above molar heat capacity were calculated. [ABSTRACT FROM AUTHOR]

The development of photopolymers was helped by the development of photocalorimetry, which is now a basic technique for the study of these materials. This work shows how to obtain vitrification times in single isothermal curing experiments by monitoring the reversing heat capacity along time in modulated temperature DSC-photocuring systems, overcoming the time-consuming problem of standard DSC. The effects of the light intensity and the isothermal curing temperature on the vitrification time of a photocurable system were evaluated. The results obtained at a given curing temperature with different light intensities indicate that the UV-light affects the molecular mobility hindering the vitrification process. The effects of the curing temperature on the vitrification time, the conversion at the vitrification time and the maximum conversion were also evaluated. [ABSTRACT FROM AUTHOR]

The low-temperature molar heat capacity of crystalline Mn(HEDTA)·10HO was measured by temperature-modulated differential scanning calorimetry (TMDSC) for the first time. The thermodynamic parameters such as entropy and enthalpy relative to 298.15 K were calculated based on the above molar heat capacity data. The compound was characterized by powder XRD, FT-IR spectrum. Moreover, the thermal decomposition characteristics of Mn(HEDTA)·10HO were investigated by thermogravimetry-mass spectrometer (TG-MS). The experimental result through TG measurement shows that a three-step mass loss process exists. HO, CO, NO, and NO were observed as products for oxidative degradation of Mn(HEDTA)·10HO from the MS curves. [ABSTRACT FROM AUTHOR]

The processes of vitrification and devitrification that occur in an epoxy resin when it cures non-isothermally with a hardener are studied in terms of their frequency dependence and as a function of the heating rate. A novel modulated DSC technique, TOPEM, has been used which permits the evaluation of the frequency dependence for a single sample in a scan at constant underlying heating rate, thus avoiding errors arising from the composition of the sample. The effects of both frequency and heating rate on vitrification and devitrification are investigated. Some advantages of this technique are observed and discussed. [ABSTRACT FROM AUTHOR]

Abstract: To develop constitutive models to represent the thermomechanically chemically coupled behaviour of curing resins, vulcanizing elastomers or melting and crystallizing polymers the technique of DSC is extremely helpful. In the present study, the method of TMDSC is interpreted and evaluated in the context of thermodynamics with internal state variables. The balance equation of energy and the dissipation principle in the form of the Clausius–Duhem inequality form the theoretical basis of our study. Since the pressure and the temperature are the external variables in DSC, the specific Gibbs free energy is used as thermodynamic potential. It depends on temperature, stress and a set of internal state variables to represent the microstructure of the material on a phenomenological basis. The temperature- and internal variable-induced changes in the Gibbs free energy are approximated by a Taylor series up to second order terms. As a substantial result of this work, closed-form expressions for the dynamic calorimetric response due to harmonic temperature perturbations and the frequency-dependent complex heat capacity are derived. The theory allows a physical interpretation of the complex heat capacity and its underlying phenomena and is in accordance with experimental observations from literature. [Copyright &y& Elsevier]

Zinc formate dihydrate has been synthesized and characterized by powder X-ray diffraction, elemental analysis, FTIR spectra and thermal analysis. The molar heat capacity of the coordination compound was measured by a temperature modulated differential scanning calorimetry (TMDSC) over the temperature range from 200 to 330 K for the first time. The thermodynamic parameters such as entropy and enthalpy vs. 298.15 K based on the above molar heat capacity were calculated. The thermal decomposition characteristics of this compound were investigated by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). TG curve showed that the thermal decomposition occurred in two stages. The first step was the dehydration process of the coordination compound, and the second step corresponded to the decomposition of the anhydrous zinc formate. The apparent activation energy of the dehydration step of the compound was calculated by the Kissinger method using experimental data of TG analysis. There are three sharply endothermic peaks in the temperature range from 300 to 650 K in DSC curve. [ABSTRACT FROM AUTHOR]

The low-temperature molar heat capacities of CoPc and CoTMPP were measured by temperature modulated differential scanning calorimetry (TMDSC) over the temperature range from 223 to 413 K for the first time. No phase transition or thermal anomaly was observed in the experimental temperature range for CoPc. However, a structural change was found to be nonreversible for CoTMPP in the temperature range of 368–403 K, which was further validated by the results of IR and XRD. The molar enthalpy Δ H m and entropy Δ S m of phase transition of the CoTMPP were determined to be 3.301 kJ mol−1 and 8.596 J K−1 mol−1, respectively. The thermodynamic parameters of CoPc and CoTMPP such as entropy and enthalpy relative to reference temperature 298.15 K were derived based on the above molar heat capacity data. Moreover, the thermal stability of these two compounds was further investigated through TG measurements. Three steps of mass loss were observed in the TG curve for CoPc and five steps for CoTMPP. [ABSTRACT FROM AUTHOR]

This review traces the development of thermal analysis over the last 50 years as it was experienced and contributed to by the author. The article touches upon the beginning of calorimetry and thermal analysis of polymers, the development of differential scanning calorimetry (DSC), single-run DSC, and other special instrumentations, up to the recent addition of modulation to calorimetry and superfast calorimetry. Many new words and phrases have been introduced to the field by the author and his students, leaving a trail of the varied interests over 50 years. It began with cold crystallization and more recently the terms oriented, intermediate phase, glass transitions of crystals, and decoupled chain segments were coined. In-between the following phenomena were named and studied: extended-chain crystals, irreversible thermodynamics of melting of polymer crystals, zero-entropy-production melting, dynamic differential thermal analysis (DDTA), the rule of constant increase of C p per mobile bead within a molecule at the glass transition temperature, superheating of polymer crystals, melting kinetics, crystallization during polymerization, chin-folding principle, molecular nucleation, rigid amorphous phase, system of classifying molecules, macroconformations, amorphous defects, rules for the entropy of fusion based on molecular shape and flexibility, single-molecule single-crystals, systems for classifying phases and mesophases including condis phases, and the globally metastable semicrystalline polymers with reversible, local subsystems. [ABSTRACT FROM AUTHOR]

The heat capacity or the specific heat is for any crystalline, partially amorphous or completely amorphous substance or material a significant thermodynamic property. The glass transition may be regarded as the melting point of amorphous substances and materials, a transition property of an outstanding technical importance. A crucial point is the fact that the presence of a glass transition is an unequivocal proof of an amorphous content of a material. Furthermore, the change of the specific heat at the glass transition temperature enables the quantitative determination of the amorphicity on a relative or absolute level of any substance or material. The absolute determination of the amorphicity affords a calibration with a reference corresponding to the material under investigation. The crystallinity for this reference substance must be known from the preparation and or by any independent analytical method. The literature data for the specific heat and the glass transition of polystyrene were collected and evaluated. Data were found for the specific heat in literature from 10 to 470 K. The data were unified for each of the reported temperature in a mean value and the corresponding standard deviation was determined. An excellent conformity was found in the glassy state of polystyrene with standard deviations lower than 0.7%. The standard deviations above the glass transition were considerably higher. All these literature data were transferred for each of the literature sets separately into linear specific heat functions in the vicinity of the glass transition. One set of our measurements performed with the DSC 204 and with polystyrene SRM 705a as sample material was additionally integrated in the mean of these functions for the glassy state and the liquid amorphous state respectively. The addition of our results gave practically no change of the mean coefficients and only a decrease of the standard deviations. In such a way, the data with the best statistical base for the specific heat of polystyrene are listed in this paper ( ‘Conclusions’). The glass transition as a transition in and out of a non-equilibrium state, the glassy state, is sensitive to all kind of influences such as thermal and mechanical treatments as well as to the selected experimental conditions. Therefore, certain standardized conditions procedures must be fulfilled to get reproducible data. The literature data for the glass transition temperature were also used to get a mean value. However, two values were omitted for the formation of the mean, because the authors reported values, which were too low on the base of impurities present. The mean value of the glass transition for polystyrene is according to the literature 369±2 K. A mean value of 370±2 K was extrapolated for an infinite molecular mass. The DSC and TMDSC measurements for the three thermodynamic properties reported in this paper, namely the specific heat, the glass transition temperature and the corresponding change of the specific heat gave results without significant differences compared with the literature values. Atactic polystyrene is a rather ideal polymer together with sapphire as calibration substance to elucidate and validate the DSC and TMDSC procedures for the determination of the specific heat and the glass transition. [ABSTRACT FROM AUTHOR]

Contributions of modern, temperature-modulated calorimetry are qualitatively and quantitatively discussed. The limitations are summarized, and it is shown that their understanding leads to new advances in instrumentation and measurement. The new thermal analysis experiments allow to separate reversing from irreversible processes. This opens the irreversible states and transitions to a description in terms of equilibrium and irreversible thermodynamics. Amorphous systems can be treated frommacroscopic to nanometer sizes with weak to strong coupling between neighboring phases. Semicrystalline, macromolecular systems are understood on the basis of modulated calorimetry as globally metastable, micro-to-nanophase-separated systems with locally reversible transitions. [ABSTRACT FROM AUTHOR]

All started with the invention of differential thermal analysis, DTA at the beginning of the 20th century. The tool was qualitative in the measurement of heat, but quantitative in measuring temperature. The differential scanning calorimetry, DSC, became popular in the 1970s. In certain temperature regions, it could replace even the more precise, but cumbersome, classical technique of adiabatic calorimetry. A large volume of quantitative thermodynamic information was accumulated. Both equilibrium and non-equilibrium data were collected. Unfortunately, the qualitative applications of the DSC grew even faster and overshadowed the quantitative capabilities of measurement of heat. The newer temperature-modulated DSC, TMDSC, makes use of the same instrumentation and seems to follow the same fate, despite the fact, that it can distinguish equilibrium from non-equilibrium, a key information needed in the thermodynamic description of materials. Seeing the growth of these efficient techniques, one could conclude that all questions one might have wanted to ask in 1900 can be answered now. A new question, however, has become important in the 21st century: What happens at the nanophase level and in the description of very fast processes? Are we able to learn from the past, or are we again to stay at the level of qualitative DTA? [ABSTRACT FROM AUTHOR]