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A detailed thermal analysis investigation of title BCS class II active pharmaceutical ingredients with low solubility and high permeability and known polymorphism were reported. Differential scanning calorimetry (DSC) and thermogravimetry analysis (TG) were used as primary screening techniques to assess into the polymorphic stability of the studied APIs relative to their thermal properties. The solid-state behavior of the drug compounds was further evaluated by X-ray powder diffraction (XRPD) and Fourier transform infrared spectroscopy (FT-IR). The spectra-structural techniques were applied as supportive tools to confirm and correlate the DSC and TG results obtained by preformulation testing. As an attempt to broaden the thermal analysis, a temperature-modulated DSC (TMDSC) was developed to examine the physical properties and explain the polymorphic stability of the studied amorphous lercanidipine HCl. The TMDSC results also aimed to determine the thermal properties comprising glass transition temperature (Tg) and heat capacity (ΔCp). Based on the thermal evolution and the applied preformulation tests, both drug substances manifested considerable increase in their moisture content (hygroscopicity) in relatively short time after exposure on elevated relative humidity in stability testing chambers. The results obtained from the above-mentioned instrumentation inevitably confirmed occurrence of polymorphic transition for both active substances after recrystallization from absolute ethanol. To the best of our knowledge, the study reports new type of crystalline form of lercanidipine HCl as well as unveils the transition of anhydrous ezetimibe to monohydrate form. In addition, the thermal behavior of amorphous lercanidipine HCl is, for the first time, outlined and described in this work. [ABSTRACT FROM AUTHOR]

Post-consumer plastic waste contains blends of numerous types of polyethylene (PE) and isotactic polypropylene (i-PP), whose recycling is challenging due to the complexity of this waste stream. A comprehensive knowledge of the composition of these recyclates is essential to understand the structure-property relationship of these systems and therefore upcycle them for high-value applications. To this aim, we used Temperature Modulated DSC (TM-DSC) to develop a quantitative method to evaluate PE and Low-density PE (LDPE) content in recycled polyolefin blends. TM-DSC was carried out on 29 virgin PE materials, spanning densities between 960 and 862 kg/m3, characterizing a wide range of PE microstructures. Moreover, several PE/i-PP model blends were prepared by selecting LDPE, High-density PE (HDPE) and Linear Low-density PE (LLDPE) materials to blend them with i-PP of three types: homopolymer (PP–H), block copolymer (PP–B) and random copolymer (PP-R), mimicking the composition of real recyclates. Results from the TM-DSC analysis of these blends allowed us to establish methods for quantifying the amount of overall PE content and also the LDPE fraction within recyclates. The developed methods were applied to real post-consumer recycled grades, and results were compared with the ones obtained from Cross-Fractionation Chromatography (CFC) analysis and Nuclear Magnetic Resonance (NMR) spectroscopy, displaying good agreement between the latter and the TM-DSC method.

The influence of post-process annealing treatment on the structural and thermal behaviors of poly(L-lactic acid)/poly(butylene succinate) (PLLA/PBS) blend was investigated by temperature modulated differential scanning calorimetry (TMDSC) and wide-angle X-ray diffractometry. It is shown that the low-order α′-structure of PLLA was formed in the as-molded samples and the molded products annealed at the temperatures below the melting of PBS, whereas the high-order α-crystal was developed when the high temperature of annealing (152 °C) was applied. With the addition of poly(ethylene glycol) plasticizer to the blends, the formation of high-order α-structure was prohibited. During the DSC heating scan, the α′- to α-crystalline phase transformation did not occur. The evidence of multiple melting behaviors observed by TMDSC was ascribed to the simultaneous melting, recrystallization, and remelting of the PLLA and PBS crystals in the blends. [ABSTRACT FROM AUTHOR]

Cartilage thermoforming is an emerging surgical technology which uses heat to accelerate stress relaxation in mechanically deformed tissue specimens. Heat induced shape change in cartilage is associated with complex thermo mechanical behavior of which the mechanisms are still a subject of debate. Differential scanning calorimetry (DSC) was used to characterize the threshold temperatures and enthalpies in cartilage as a function of water content. The DSC identified two enthalpic events in porcine nasal septal cartilage, which depend on the water content. The change in the water content of cartilage impacts the interactions between matrix macromolecules and water molecules, which may be associated with a bound-free water transformation (reversible process) and a denaturation of cartilage (irreversible process).

The molar heat capacities of one-three-dimensional metal-organic frameworks Al4(OH)2(OCH3)4(H2N-BDC)3 (CAU-1) were measured by temperature-modulated differential scanning calorimetry (TMDSC) over the temperature range from 213 to 393 K for the first time. No phase transition or thermal anomaly was observed in the experimental temperature range. The fundamental thermodynamic parameters such as entropy and enthalpy relative to 298.15 K were calculated based on the experimentally determined molar heat capacities. The compound was characterized by elemental analysis, powder XRD, FT-IR spectrum. Moreover, the thermal stabilities and decomposition mechanisms of hydrated phase and dehydrated phase of CAU-1 were investigated by thermogravimetric spectrometer in the temperature range 298-1023 K. [ABSTRACT FROM AUTHOR]

The molar heat capacities of one-three-dimensional zeolitic imidazolate frameworks Zn(C4H6N2)2 (ZIF-8) were measured by temperature-modulated differential scanning calorimetry over the temperature range from 213 to 423 K for the first time. No phase transition or thermal anomaly was observed in the experimental temperature range. The fundamental thermodynamic parameters such as entropy and enthalpy relative to 298.15 K were calculated based on the experimentally determined molar heat capacities. The compound was characterized by powder XRD and FT-IR spectroscopy. Moreover, the thermal decomposition characteristics of ZIF-8 were investigated by thermogravimetry spectrometer (TG). [ABSTRACT FROM AUTHOR]

The molar heat capacities of one-three-dimensional metal-organic frameworks Al4(OH)2(OCH3)4(H2N-BDC)3 (CAU-1) were measured by temperature-modulated differential scanning calorimetry (TMDSC) over the temperature range from 213 to 393 K for the first time. No phase transition or thermal anomaly was observed in the experimental temperature range. The fundamental thermodynamic parameters such as entropy and enthalpy relative to 298.15 K were calculated based on the experimentally determined molar heat capacities. The compound was characterized by elemental analysis, powder XRD, FT-IR spectrum. Moreover, the thermal stabilities and decomposition mechanisms of hydrated phase and dehydrated phase of CAU-1 were investigated by thermogravimetric spectrometer in the temperature range 298-1023 K. [ABSTRACT FROM AUTHOR]

The molar heat capacities of one-three-dimensional metal-organic frameworks (MOFs) CrF(HO)O(BDC) (Cr-MIL-101) were measured by temperature-modulated differential scanning calorimetry over the temperature range from 253 to 413 K for the first time. No phase transition or thermal anomaly was observed in the experimental temperature range. The fundamental thermodynamic parameters such as entropy and enthalpy relative to 298.15 K were calculated based on the experimentally determined molar heat capacities. The compound was characterized by atomic absorption spectrometer, elemental analysis, powder XRD and FTIR spectrum. Moreover, the thermal decomposition characteristics of Cr-MIL-101 were investigated by thermogravimetry-mass spectrometer (TG-MS). Three stages of mass loss were observed in the TG curve. TG-MS curve indicated that the oxidative degradation products of Cr-MIL-101 are mainly HO and CO. [ABSTRACT FROM AUTHOR]

In present study, based on the two polymorphs (α and β form) of azelnidipine (AZE), 12 complexes of AZE and oxalic acid (OXA) were prepared by solvent-assisted grinding (SG) and neat powder grinding (NG) methods at the AZE/OXA molar ratios of 2:1, 1:1, and 1:2. The effect of the different polymorphs of AZE on the micro-structure of the complexes were investigated by powder X-ray diffraction (PXRD), tempreture modulated differential scanning calorimetry and thermogravimetric analysis, cryo-field emission scanning electron microscope system, fourier transform infrared (FTIR), and solid-state nuclear magnetic resonance spectroscopy. β-AZE-OXA co-crystal was produced at β-AZE/OXA molar ratio of 2:1 when SG method was used; while α-AZE was used to produce α-AZE-OXA co-crystal at same condition. However, the other 10 combinations were in co-amorphous forms, including the NG samples with α (or β)-AZE/OXA molar ratios of 2:1, 1:1 (SG and NG), and 1:2 (SG and NG). Although the XRD pattern and IR spectra of the two co-crystals showed no difference, the melting enthalpy and specific heat c p of the β-AZE-OXA co-crystal was higher than that of the α-AZE-OXA co-crystal, indicating that the numbers of solvent molecules which entered the two co-crystal lattices were different. Interestingly, obvious difference occurred in the IR spectra between the α-AZE-OXA and β-AZE-OXA co-amorphous systems. 1745 cm −1 wave-numbers, which were assigned to the free C O groups, appeared in the α-AZE-OXA co-amorphous systems even when just a small amount of OXA was introduced, thereby indicating the presence of different intermolecular forces in the two series of co-amorphous forms. The solubility in different media and the dissolution rate in 0.1 mol L −1 HCl of the 12 complexes were determined. The dramatically improved dissolution rates of the α- and β-AZE-OXA 1:2 (NG) combinations in vitro showed potential in improving the physicochemical properties of AZE by co-amorphous complex formation. [ABSTRACT FROM AUTHOR]

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]

Common temperature modulated DSCs are limited in the accessible frequency range to about 0.1–0.001 Hz. We describe an extension of this frequency range towards lower and higher frequencies by using conventional DSCs (without TMDSC option). By applying steps in the temperature-time profile a simultaneous multi frequency analysis of the heating rate and the heat flow rate response yields heat capacity data over about 2 orders of magnitude in frequency from one single measurement. Based on this step response analysis we show on the example of a Calvet calorimeter, Setaram BT 2.15, an extension down to 10 −5 Hz and on the example of a chip calorimeter, Mettler Toledo Flash DSC 1, an extension up to 150 Hz. Details of the experimental procedures are provided and the influence of sample size on the obtained data and general limitations, particularly regarding temperature assignment, are discussed. A relaxation map is used to combine all calorimetric data and to compare them with dielectric data. [ABSTRACT FROM AUTHOR]

Reversible melting is a phenomenon unique to polymer crystals, which raises an excess reversing heat capacity near their melting points. By means of temperature-modulated differential scanning calorimetry (TMDSC) measurements with an expanded frequency range in chip-calorimeter, we studied reversing heat capacities of alpha- and beta-form crystals of isotactic polypropylene. We attributed their differences at high temperatures and low frequencies to variable chain mobility in these two crystals. We further performed parallel dynamic Monte Carlo simulations of lattice polymers with variable chain mobility in the crystals to confirm this attribution. Our observations provide the first evidence on the role of chain mobility in the microscopic mechanism of reversible melting at the fold-end surfaces of lamellar polymer crystals. [ABSTRACT FROM AUTHOR]

Phase-structural changes and enthalpic relaxation behavior of poly( d , l -lactide) (PDLLA), poly( l -lactide) (PLLA) and poly( l -lactide-co-ε-caprolactone) (PLCL) copolymers with a lactide molar content ∼70% and having different randomness character (PLCL r 1 : R = 0.69; PLCL r 2 : R = 0.92) were evaluated over 7 days in phosphate buffered saline (PBS) at 37 °C. Results obtained by Temperature Modulated Differential Scanning Calorimetry (TMDSC) and Dynamic Mechanical Analysis (DMA) showed an increase in the value of enthalpic relaxation ( δ ) and the narrowing of the tan δ peak, respectively, indicating the reduction in molecular mobility and a more uniform distribution of the entropic states as the aging time increased. The results obtained for PLCLs were clearly affected by chain microstructural magnitudes, l LA (PLCL r 1 = 4.35 and PLCL r 2 = 3.45). Both showed a crystallization process accompanied by amorphous phase separation during the early stage in PBS. DSC and DMA results also revealed faster structural changes as a result of new supramolecular arrangements as well as a higher tendency to crystallize for PLCL r 1 regarding PLCL r 2 . [ABSTRACT FROM AUTHOR]

Dielectric analysis (DEA) is a very sensitive technique, which allows for detection of small structural changes at the low scale. An advantage of DEA, with respect to other modulated techniques, is the possibility of using a wider frequency range. Molecular relaxations of the order of only a few nanometers are not observed by any other thermoanalytic method. Nevertheless, these small relaxations involve dipole changes that can be observed by DEA. Thus, this technique is used here, in combination with temperature-modulated differential scanning calorimetry (TMDSC) to obtain insightful information about the thermal transitions of poly- l-lactic acid (PLLA), one of the stereo-isomers of polylactide. Its complex thermal behavior is the subject of ongoing debate, with several overlapping crystallization and melting processes. The combined use of TMDSC and DEA provides a better insight of three important transitions of this polymer: the alpha relaxation, the enthalpic relaxation, and the cold crystallization. The dependences of the enthalpy relaxation on the dynamic glass transition relaxation and on the glass transition as a thermal event are evaluated. On the other hand, it will be shown how the cold crystallization can be identified by TMDSC, and DEA helps us understand the effect of crystallization on the dipole movements. The shape of the dielectric permittivity curve at low frequencies is compared to that of the reversing heat capacity to check whether both signals are sensitive or not to the same events. It is also verified how the experimental results of alpha relaxation of PLLA follow an Arrhenius or a Vogel trend. [ABSTRACT FROM AUTHOR]

ABSTRACT Adsorbed poly(ethylene-stat-vinyl acetate) (PEVAc) on fumed silica was studied using temperature-modulated differential scanning calorimetry (TMDSC) and FT-IR spectroscopy. The properties of the copolymers were compared with poly(vinyl acetate) (PVAc) and low density polyethylene (LDPE) as references. TMDSC analysis of the copolymer-silica samples in the glass transition region was complicated for the copolymers because of the ethylene crystallinity. Nevertheless, examination of the glass transition region for small adsorbed amounts of these copolymers indicated the presence of tightly- and loosely-bound polymer segments, similar to other polymers which have an attraction to silica. Compared with bulk polymers with the same composition, the tightly-bound polymers showed an increased glass transition temperature ( Tg) and a loosely-bound fraction with a lower Tg than bulk. FT-IR spectra of the surface copolymers indicated that the fraction of bound carbonyls ( p) increased as the fraction of vinyl acetate in the copolymers decreased, consistent with the notion that the carbonyls from vinyl acetate preferentially find their way to the silica surface. Spectra from samples with different adsorbed amounts of polymer were used to obtain the amount of bound polymer ( Mb) and the ratio of molar absorption coefficients of bound carbonyls to free carbonyls ( X). The copolymers had very large p values (up to 0.8) at small adsorbed amounts and dependent on the composition of the polymer. However, an analysis of the bound fractions, based on only the vinyl acetate groups, superimposed the data, suggesting that the ethylene units simply dilute the vinyl acetate groups in the surface polymer. The sample with the smallest fraction of vinyl acetate did not show this behavior and may be considered to be 'carbonyl poor.' © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 727-736 [ABSTRACT FROM AUTHOR]

This study deals with the removal of chromium species from aqueous dilute solutions using thermoresponsive linear and hyperbranched copolymers based on PEG-methacrylates. The thermal stability of polymers was studied by thermogravimetric analysis and chemiluminescence emission, which evidenced a slightly enhanced stability for hyperbranched polymers respect to linear structures. Their LCST was successfully determined by TOPEM (temperature-modulated DSC), and similar values to those obtained by UV spectroscopy were obtained. The adsorption capacities for chromium hexavalent of the polymers have been investigated as function of LCST. The results showed highest retention capacity of Cr(VI) for all polymers above LCST. Hyperbranched polymers were more efficient than linear polymers, because of the structure of the polymers. Hyperbranched polymers when precipitate form a network with more nanocavities where the chromium can be adsorbed. The efficiency increased with ratio of OEGMA/DEGMA, reaching a maximum retention capacity value of 40 mg Cr(VI)/g polymer. [ABSTRACT FROM AUTHOR]

Carbon-fibre prepregs have found widespread use in lightweight applications. They are based on a carbon-fibre fabric impregnated with reactive epoxy resin. Prepreg materials are generally pre-cured so that they have a higher molecular weight than typical resins in order to reduce resin flow, which facilitates storage and later processing properties. The measurements were carried out using commercially available materials and follow the published DMA investigations of the same material [1]. TMDSC was used to find the correlation between curing conditions, the degree of cure and glass transition temperature. TMDSC has the advantage over standard DSC that it enables better determination of the glass transition temperature, which is often accompanied by an exothermic curing reaction, and thus overshadowed. The influence of the amplitude of temperature modulation was tested in preliminary experiments. For non-cured material a glass transition temperature of approximately 0 °C was determined; whereas for the totally cured material it was approximately 230 °C. The changes in degree of cure, temperature of actual glass transition and post-reaction are given as a function of curing time at 180 °C. The correlation between actual glass transition temperature and degree of cure is derived. [ABSTRACT FROM AUTHOR]

Thermal behavior of angiotensin II type 1 (AT1) receptor antagonist, Valsartan (VAL), was examined employing thermogravimetric analysis (TGA), standard differential scanning calorimetry (DSC) and temperature-modulated differential scanning calorimetry (TMDSC). The stability of VAL was measured by TGA from 25 to 600°C. Decomposition of Valsartan starts around 160°C. The DSC curve shows two endotherms, occurring around 80°C and 100°C, related to evaporation of water and enthalpy relaxation, respectively. Valsartan was identified by DSC as an amorphous material and it was confirmed by X-ray powder diffraction. The glass transition of fresh Valsartan appears around 76°C (fictive temperature). TMDSC allows separation of the total heat flow rate into reversing and nonreversing parts. The nonreversing curve corresponds to the enthalpy relaxation and the reversing curve shows changes of heat capacity around 94°C. In the second run, TMDSC curve shows the glass transition process occurring at around 74°C. Results from standard DSC and TMDSC of Valsartan were compared over the whole range of temperature. [ABSTRACT FROM AUTHOR]

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]

Quantitative thermal analysis of the evolution of crystal and amorphous fractions of poly[(R)-3-hydroxybutyrate] (PHB) upon storage at room temperature is detailed in this contribution. Conventional and temperature-modulated calorimetry were used to quantify the crystallinity, as well as the mobile and rigid amorphous fractions, of an initially partially crystallized PHB, subsequently maintained at 25 °C for various times. PHB undergoes progressive crystallization during storage, with an increase in crystal fraction ( w) from the initial w = 0.35 up to w = 0.71 attained after 1 year of storage. Crystallization is accompanied by vitrification of rigid amorphous segments, which leads to a noteworthy increase of the overall fraction of the material that is solid at room temperature, leaving only a mobile amorphous fraction w = 0.04 after 1 year at 25 °C. The quantitative thermal analysis allowed to clarify the kinetics of evolution of both the ordered and unordered fractions of PHB upon storage, which leads to a severe deterioration of material's properties. [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]

StepScan DSC technique was used for the study of the glass transition phenomenon. This method allows relatively good monitoring of reversing and non-reversing processes, and thus is very useful tool for glass transition studies of wide type of glass-forming materials, including inorganic glasses as well as organic polymers. In this work, experience with the StepScan DSC technique is summarized. Some interesting results of its application are presented, such as determination of glass transition temperature independent on thermal history of glass, discovered relationship between the slope of temperature dependence of C in T, and Angel's index of fragility and estimation of viscosity glass transition temperature, T. [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]

Abstract: Various polyethylenes (PEs) and the effects of high-energy radiation on their structures were widely studied in the past using conventional Differential Scanning Calorimetry (DSC) measurements. In this work, we used the Temperature Modulated Differential Scanning Calorimetry (TMDSC) technique in order to obtain more information about the influence of the initial structural differences and gamma radiation on the evolution in structure and thermal properties of different polyethylenes. For this reason, low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) samples were exposed to gamma radiation, in air, to a wide range of absorbed doses (up to 2400kGy). The separation of the total heat flow TMDSC signal into a reversing and non-reversing part enabled us to observe the low-temperature enthalpy relaxation (related to the existence of the “rigid amorphous phase”) and recrystallisation processes, as well as to follow their radiation-induced evolution and/or that of melting in a more revealing manner compared to the case of the conventional DSC. Consequently, our results indicate that TMDSC could improve the understanding of radiation-induced effects in polymers. [Copyright &y& Elsevier]

The present study suggests a new approach, based on the utilization of temperature modulated differential scanning calorimetry (TMDSC) technique, for identifying and characterizing the organic-inorganic interphase of two materials: an epoxy-fumed silica nanocomposite and a thermoplastic polyurethane (TPU)-multiwalled nanotube (MWNT) composite. The approach used here makes use of TMDSC data and basically consists of using the phase angle or the derivative of the reversing heat flow instead of the reversing heat flow curve itself. In the case of epoxy-fumed silica composites, two glass transition regions were identified. The glass transition temperature ( T) of the composite was observed to vary as a consequence of the filler content. This study shows that the T variation is due to the formation of an organic-inorganic interphase, with its own glass transition temperature, which is different from the epoxy matrix T. In the case of TPU-MWNT composites, two relaxations and an additional first order transition were observed: the first relaxation corresponds to the hard segment, the second is related to an interaction between filler and matrix and the third process may be connected to the partial melting of the hard segment. The addition of 0.5 wt% MWNT causes a small reduction in T of the TPU. A major nanotube addition, 10 wt%, induces the appearance of a new relaxation that may be associated with the existence of an interface. In general, a better separation between the matrix and interphase glass transitions was obtained by the TMDSC phase angle signal. [ABSTRACT FROM AUTHOR]

Abstract: Gelatinisation of waxy maize starch (WMS) in excess glycerol was investigated by a temperature modulated DSC in quasi-isothermal and non-isothermal mode. By using the measured specific heat capacities (c p ) at different stages of gelatinisation and the hypothetical enthalpy of melting for 100% crystalline amylopectin, a method was developed to reveal the amorphous fraction which remains glassy in the presence of excess glycerol what can be called “rigid amorphous”. It was suggested that the amorphous part of starch was plasticised at around 40°C whereas, rigid amorphous fraction underwent a second stage glass transition which showed itself by an increase in c p under the gelatinisation endotherm. It was also shown that holding WMS in excess glycerol at 100°C (10°C above the gelatinisation onset temperature) for 10 days was not enough to gelatinise the whole WMS implicating that the most stable crystals did not melt before the required threshold temperature was reached. [Copyright &y& Elsevier]

A series of flexure tests with varying crosshead speed were conducted to study the mechanical behavior of glass/epoxy composites at low temperature. The micromechanics of damage growth and failures underpin the understanding of the revealed fractography. The three-point flexure test of heat-treated and untreated samples was carried out, which were further exposed to low and ultra-low working temperatures of −20°C, −40°C, −60°C, −80°C. The interlaminar shear strength was found to be affected by these conditionings. The unbalanced and inhomogeneous stress concentration within entangled chain of matrix reduces conformational isomerism which in turn reduces the ILSS value considerably at low crosshead speed. At increased crosshead speed (strain rate), the matrix becomes brittle and fracture strain decreases, but at very high strain rate, the fracture strain increases. The reason is anticipated to be adiabatic heating. Temperature-modulated differential scanning calorimetry shows increase in glass transition temperature (Tg). A change in crosshead speed may result in variation of failure modes, which is observed in scanning electron microscope. [ABSTRACT FROM PUBLISHER]

Biodiesel has the advantage of being renewable and clean and for these reasons has been studied recently both academically and in industry. Research in this area is focused on developing new synthetic routes to obtain a purer product or to find new alternative sources of food to replace conventional oils. Papaya biodiesel is obtained from oily residues with a fatty acid composition similar to olive oil. It is generally discarded by the ton, considering that Brazil is the world's largest producer of papaya with an annual output of 1,811 million tons, productivity of 52 t/hectare and domestic consumption at 86.5%. This study was designed by means of thermal analysis (TG, DSC, P-DSC, and MT-DSC), to verify the possibility of achieving high quality biodiesel, with oxidative stability and flow properties previously indicated by composition analysis of its fatty esters, physical-chemical properties (including oxidative stability) using classical methodology, recommended by ASTM D 6756. [ABSTRACT FROM AUTHOR]

Cloud point (CP), cold filter plugging point (CFPP), and pour point (PP) of biodiesel samples obtained from blends containing different amounts of beef tallow, babassu oil, and soybean oil were investigated by the corresponding conventional techniques and by temperature modulated differential scanning calorimetry (TMDSC). The CP and CFPP values correlate well with the crystallization temperature ( T) obtained from the TMDSC curves, being the highest for the biodiesel sample containing the highest amount of methyl stearate. A correspondence between PP and the peak temperature was also noticed, pointing out that pouring ceases after the crystallization of the heavier fatty acid ester. Among the samples of biodiesel, Bio-3 (highest amount of babassu oil) and Bio-4 (highest amount of soybean oil) showed better cold-flow properties, or in other words, lower values of CP, CFPP, and PP. Independently of the composition, the cold-flow properties of all biodiesel samples meet the requirements from the Brazilian National Agency of Petroleum, Natural Gas, and Biofuels (ANP). [ABSTRACT FROM AUTHOR]

The use of pressure cell attached to a temperature modulated differential scanning calorimeter (TMDSC) is investigated to perform modulated DSC experiments at high pressures (TMPDSC). No previous reports were found on the use of TMPDSC. In this study, the proposed method is applied to the study of the pressure effect on the curing reaction of an epoxy system. Curing quasi-isothermal modulated experiments were performed at different pressures to evaluate the vitrification time. Linear heating modulated tests were also successfully performed at different pressures to separate the reversing glass transition effect from the residual exothermic cure reaction. The curing enthalpy, conversion versus temperature, and glass transition of the fully cured thermoset were also evaluated. All the studied parameters resulted to be affected by the pressure in the range from atmospheric pressure to 35 bar. It was observed that the curing enthalpy, the reaction rate and the conversion at any given time increase with any pressure increment. The usefulness of TMDSC to characterize the curing of thermosets is extended by PTMDSC to situations, i.e., aeronautics industry, where pressure curing is needed. [ABSTRACT FROM AUTHOR]

Blends of bacterial poly(( R)-3-hydroxybutyrate) (PHB) and poly( l-lactic acid) (PLLA) synthesized by polycondensation of l-lactic acid or by ring-opening polymerization of l-lactide were studied. Miscibility was investigated through both conventional differential scanning calorimetry (DSC) and temperature-modulated DSC (TMDSC). PHB and low-molar mass PLLA were miscible in a whole concentration range, and a single glass transition temperature was observed. On the other hand, PHB/high-molar mass PLLA mixtures phase separate, giving rise to two glass transition temperatures corresponding to PHB and PLLA. A treatment of blends at 190 °C leads to formation of block/multiblock/random copolymers, and blends become miscible. [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]

metal-organic framework [Mn(4,4′-bipy)(1,3-BDC)] (MnMOF, 1,3-BDC = 1,3-benzene dicarboxylate, 4,4′-bipy = 4,4′-bipyridine) has been synthesized hydrothermally and characterized by single crystal XRD and FT-IR spectrum. The low-temperature molar heat capacities of MnMOF 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 above molar heat capacity data. Moreover, the thermal stability and the decomposition mechanism of MnMOF were investigated by thermogravimetry analysis-mass spectrometer. A two-stage mass loss was observed in air flow. MS curves indicated that the gas products of oxidative degradation were HO, CO, NO, and NO. [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]

Temperature-modulated differential scanning calorimetry (TMDSC) is known to have the ability to measure heat capacity of materials more accurately than the conventional differential scanning calorimeter. However, the accuracy of the measured heat capacity displays significant dependence on various experimental parameters such as period of modulation ( p), amplitude of modulation ( a), geometry of sample ( g), heating rate ( r), etc. One of the key features of this system is the ability to measure heat capacity under quasi-isothermal conditions. In the present investigation, heat capacity of a well-established system namely sapphire and thoria was measured by TMDSC under dynamic mode and also under quasi-isothermal mode. The experimental parameters, mentioned above p, a, g, and r are varied to establish the conditions for measuring heat capacity accurately. [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]

Abstract: Measurements of the glass transition temperature obtained by dynamic mechanical analysis (DMA) and temperature modulated differential scanning calorimetry (TMDSC) are reported to be different. This was mainly attributed to the frequency effect. To obtain comparable measurements, experimental conditions were studied. Although some experimental issues had to be fixed, it was possible to apply the same frequency and temperature using quasi-isothermal conditions in both instruments. The method was tested with three different polymer samples. It was then found that when choosing a suitable response parameter, i.e. the phase angle, the dynamic glass transition temperature values obtained by both methods are practically the same. [ABSTRACT FROM AUTHOR]

The thermodynamic properties of a new antidepressant drug are studied from room temperature to 200 °C. In this range, the sample neither decompose, nor has a significant reactivity with water. When slowly heating a “fresh” sample, we may observe the following phenomena (in the order): melting of a form (F1, ~170 °C), crystallization of a structurally different form (F2), and melting of F2 (~180 °C). In no circumstances, the direct transition from F1 to F2 can be observed. On the other hand, F2 reverts to F1 upon cooling below ~130 °C. A glassy phase is formed upon cooling from above 180 °C, as confirmed by X-ray analysis and the appearance of a glass transition when reheating. The “reversible” (e.g., melting) and “irreversible” (e.g., glass formation) contributions to the measured enthalpies are estimated with temperature-modulated DSC measurements, resulting into a consistent description of thermodynamics of the forms, their melting and their kinetics of transformation. [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]

The fragility of ethylene glycol and glucose aqueous solution systems has been investigated by temperature-modulated differential scanning calorimetry (TMDSC). The frequency and temperature dependences of complex specific heat have been observed in the vicinity of a glass-transition temperature Tg . It is shown that the value of the fragility index m can be determined from the temperature dependence of the α-relaxation times observed by TMDSC. We have also studied the elastic properties of these aqueous solutions by micro-Brillouin scattering, and determined these relaxation times of elastic properties in the gigahertz range. [ABSTRACT FROM AUTHOR]

Temperature modulated differential scanning calorimetry (TMDSC) and dynamic mechanical analysis (DMA) are used to calculate cooperative rearranging region (CRR) average sizes for drawn poly(ethylene terephthalate) (PET) with different draw ratios (λ) ranging from λ=1 to 4, according to Donth’s approach. It is shown for both studies that the CRR size decreases when increases, due to the amorphous phase confinement by the crystals generated during the drawing. However, differences observed between the values calculated from TMDSC and DMA investigations are explained by the differences between a mechanical uniaxial dynamic solicitation (DMA) or a thermal solicitation (TMDSC) in terms of cooperative rearrangements at the glass transition. [ABSTRACT FROM AUTHOR]

The babassu ( Orbignya Phalerata Mart.) biodiesel has lauric esters as main constituents, resulting in high oxidative stability and low cloud and freezing points. In order to reduce these side effects, the saturated ethyl esters content was reduced by means of winterization process. The TMDSC and PDSC techniques were used to verify the thermal and oxidative stabilities of the ethyl babassu biodiesel. During the heating stage, the winterized solid phase of ethyl esters presented an endothermic transition associated to the solidification process. This behavior was not observed for the liquid winterized FAEE, confirming the efficiency of the winterization process. [ABSTRACT FROM AUTHOR]

Melting behaviours of poly(oxytetramethylene)glycols (POTMGs) with different molar masses were investigated by temperature-modulated differential scanning calorimetry (TMDSC) and relaxation times within the melting range were estimated from the modulation-frequency dependence of phase angle δ. An Arrhenius plot of the relaxation times exhibited a plateau in the lower melting peak region of POTMGs with molar masses of 1400, 1000 and 650. This plot was compared with the standard DSC curve. The apparent activation energy was estimated from the relaxation time in the upper and lower sides of a melting temperature region: slight dependence on the molar mass was observed for the former region whereas the maximum value was obtained for a molar mass 1400 for the latter region. [ABSTRACT FROM AUTHOR]