Use Of Differential Scanning Calorimetry Research Articles

Isothermal differential scanning calorimetry analysis of the anionic polymerisation of polyamide-6: Separation by dual asymmetric gaussians

The use of a reactive processing approach for the manufacture of thermoplastic composites is of increasing interest owing to the potential for lower melt viscosities, processing temperatures, and cycle times. These reactive systems, such as the anionic polymerisation of polyamide-6 (APA6), lack the depth of characterisation and modelling required for mould flow simulation for the purposes of part quality assurance and process optimisation as desirable for industrial application. This is particularly important in reactive systems, owing to the potential of part failure through inadequate polymer conversion, and the nature of thermoplastic polymer crystallisation which will occur simultaneously with polymerisation in these systems. A typical experimental technique for the kinetic analysis of polymerisation is through use of Differential Scanning Calorimetry (DSC) to measure the reaction exotherms. Unfortunately, as polymerisation and crystallisation occur simultaneously, the resulting exotherms obscure each other in thermal analysis techniques, inhibiting independent model fitting. An algorithmic approach to the interpretation of kinetic information obtained by isothermal DSC is implemented and discussed, with gaussian curve parameters for a variety of isothermal temperatures and initiator/activator concentrations presented.

Curing and thermal properties of tannin-based epoxy and its blends with commercial epoxy resin

In order to find partial substitution for bisphenol A-based commercial epoxy resin (CE), a bio-based epoxy resin was prepared from eucalyptus tannins through a typical glycidylation reaction with epichlorohydrin. The structure of tannin-based epoxy resin (TE) was confirmed by Fourier transform infrared spectroscopy (FTIR) analysis. Herein, mixtures of TE and CE (TE–CE) were prepared using varying loading amounts (20, 40 and 60) wt/wt%of TE. Tannins used here are produced by solid–liquid extraction from the outer bark of eucalyptus tree, mainly consisting of condensed tannins. Through the use of differential scanning calorimetry (DSC) and FTIR techniques, the reactivity of tannin epoxy with and without commercial epoxy resin to form cross-linking network was investigated. TE was successfully cured with amine-based curing agent. Furthermore, compared to commercial epoxy resin (CE), TE exhibited broad low exothermic peak, insignificant cross-linking properties and low curing enthalpy at different levels of curing agent. Moreover, to study the influence of TE substitution on the curing properties of CE, curing behavior of TE–CE mixtures was investigated by DSC. It was found that TE at high loading levels such as 40 and 60 wt/wt% increases slightly the reactivity of CE by decreasing curing characteristics temperatures such as the initial of curing, peak exotherm and completion of curing temperatures. TE can serve as curing accelerator and has a non-desirable impact on the curing performance of CE resin such as curing enthalpy. And up to 20 wt/wt% of CE could be replaced by TE without any significant reduction in the curing behavior of CE.

Structural changes of serum albumin in response to oxidative stress caused byWalker-256 carcinosarcoma growth.

To assess oxidative stress and structural changes of the serum albumin in rats with transplanted Walker-256carcinosarcoma (W256) strains with varying sensitivity to doxorubicin (Dox). The study was performed on female Wistar rats with transplanted W256. On the 9th day after tumor cell transplantation an analysis of peripheral blood, oxidative stress parameters, and structural changes of serum albumin of experimental animals was performed. On the 9th day after W256transplantation a significant increase in the leukocyte counts was observed in the groups of animals with the Dox-resistant and parental (Dox-sensitive) W256tumors compared with the group of the intact animals: up to 14.24 ± 1.92•103/μl and 9.78 ± 1.03•103/μl, vs 8.92 ± 1.04•103/μl, respectively, due to the increase of granulocyte and monocyte counts. The number of lymphocytes was within the normal range. The level of hemoglobin and the erythrocyte counts were also within normal limits, but hematocrit in both groups of animals with tumors somewhat increased against the background of 1.2-fold elevation of the mean erythrocyte volume. In the group of rats with Dox-resistant W256, there was observed a decrease in the plateletcrit by almost 22% and thrombocyte counts- by 28%. Analysis of oxidative stress indices revealed a significant increase in the level of reactive oxygen species, 2-fold increase of malonic dialdehyde level and the degree of oxidative damage of blood plasma proteins, as well as a decrease in the activity of catalase in hemolysates (by 12-15%) in both groups of tumor-bearing rats. With the use of differential scanning calorimetry, UV and fluorescence spectroscopy we have revealed anomalous conformational changes of albumin caused by tumor development: structural rearrangements in the region of its first drug binding site located in the IIA domain, separation of globular parts of albumin molecule, and partial "opening" in a protein molecular three-domain structure resulting a loss of its thermal resistance. The development of transplanted Walker-256carcinosarcoma, especially its Dox-resistant variant, results in severe metabolic intoxication reflected in alteration of hematological parameters, and indices of oxidative stress, as well as architectonic changes of serum albumin.

Thermal Characterization of Flax/Basalt Fiber Reinforced Phenol Resin Brake Pad Material: Effective Replacement of Asbestos

ABSTRACT Asbestos fiber usage as reinforcement in friction material composites is avoided because of its carcinogenic property that might cause cancer. The aim of this study is to investigate the thermal characteristics of the novel noncommercial brake pad materials, i.e., flax fiber reinforced phenolic resin composites (FRPCs) and basalt fiber reinforced phenolic resin composites (BRPCs). FRPCs and BRPCs with different volume percentages of 2, 4, 6, and 8 of chemically treated flax and basalt fiber are fabricated by diffusion bonding technique. The thermal behavior was investigated by the use of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques. DSC results revealed that FRPC and BRPC samples reinforced with 6% volume fraction (Vf ) of the respective fibers are having better thermal stability than other volume percentage, since the glass transition temperature (Tg ) is relatively high. TGA analysis also shows that FRPC and BRPC specimens reinforced with 6% Vf of flax and basalt fibers have good thermal stability when compared to other volume fractions. The weight loss observed for 6% Vf of FRPC and BRPC is less compared to other specimens with increase in temperature. Scanning electron microscopy photography is used to analyze the orientation and bonding structure of matrix and fibers.

Does the molecular mobility and flexibility of the saccharide ring affect the glass-forming ability of naproxen in binary mixtures?

In this paper, we studied the impact of saccharides having a similar backbone but differing in the degree of freedom, local molecular mobility, flexibility of the ring and intermolecular interactions on the glass-forming ability (GFA) of naproxen (NAP) in binary mixtures. For this purpose, a series of methyl and acetyl derivatives of glucose (GLS) and anhydroglucose (anhGLS), as well as neat anhGLS have been used to produce homogeneous solid dispersions (SDs) of varying molar concentration of examined active pharmaceutical ingredient (API). Systematic measurements with the use of Differential Scanning Calorimetry (DSC) and Broadband Dielectric Spectroscopy (BDS) enabled us to determine the phase transitions, homogeneity and molecular mobility of the investigated binary mixtures as well as the impact of excipient on the crystallization tendency of NAP. It turned out that acetylated glucose (acGLS), one of the most mobile and flexible saccharides of all examined herein materials, is the best excipient enhancing the GFA of studied API. Although, it should be noted that upon storage at room temperature, we observed the recrystallization of NAP from binary mixtures. Interestingly, API always crystallized to the initial polymorphic form, as shown by X-ray diffraction (XRD) investigations. Finally, since additional measurements with the use of Fourier Transform Infrared (FTIR) Spectroscopy clearly indicated that there are no significant differences in the intermolecular interactions in the systems composed of NAP and all examined saccharides, one can postulate that the mobility and ring flexibility of the matrix have, , the most important impact on the crystallization tendency of NAP upon cooling. Consequently, it seems that in some cases, more mobile/flexible matrices can be a much better choice to enhance the glass-forming ability of studied pharmaceutical.

Practical Use of Differential Scanning Calorimetry for Thermal Stability Hazard Evaluation

Differential scanning calorimetry (DSC) is a common industry tool used in the assessment of thermal stability of materials. Despite widespread use of DSC for thermal stability hazard evaluation, mi...

Differential scanning calorimetry as a fast method to discriminate cage or free-range rabbit meat

In this work, we proposed the use of differential scanning calorimetry (DSC) as a rapid tool for the discrimination of meat samples coming from free-ranged and caged rabbits. Fatty acid composition, colour, and texture were also provided to fully characterize meat quality of the different samples. A total of 36, thirty-seven days old California × New Zealand White male rabbits were divided into 2 groups, housed in open air cages and in ground free-range, respectively. After 62 days of farming, 12 rabbits per group were slaughtered and the skinned carcasses were chilled for 24 h at 4 °C prior to be dissected. The Longissimus thoracis et lumborum muscle was analysed. The overall fatty acid profile was not affected by the farming system, while free-range rabbits show a significant lower L* value (49.59) than the open-air ones (53.54). Nor a* and b* were altered. Texture measurements revealed that there was no effect of housing system on shear force. More interestingly, the deconvolution of DSC signals in the range 30–90 °C revealed that free-range rearing lead to an increase of myosin amount in meat, being its peak percentage equal to 8.5 ± 1.9 against 4.3 ± 2.2 in meat from caged rabbits.

Varying thermodynamic conditions as a new way to tune the molecular order in glassy itraconazole

In this paper, comprehensive calorimetric, structural, inter- and intramolecular dynamics measurements with the use of Differential Scanning Calorimetry (DSC), X-ray diffraction (XRD), Broadband Dielectric and Fourier Transform Infrared (FTIR) spectroscopies have been applied to investigate properties of itraconazole (ITZ) glasses obtained via slow cooling (ordinary glass, OG), rapid quenching (quenched glass, QG) and fast compression (compressed glass, CG). Interestingly, XRD studies showed that consistently with a recent paper by Teerakapibal et al. [Phys. Rev. Lett. 120 (2018) 055502], we can significantly reduce the content of smectic order in the glassy state of this compound solely by varying the rate of cooling and pressurization. Thermograms registered for the studied samples revealed the presence of the two glass transition temperatures located below and above the Tg of the OG. Since in the QG and CG a smectic phase has not been completely removed, two Tgs were interpreted as a clear manifestation of vitrification of reorientational motions around long (α) and short (δ) axis of ITZ, occurring within nematic and smectic domains, coexisting at the same thermodynamic conditions. Finally, structural studies carried out on the quenched and compressed glasses indicated that the smectic order tends to reconstruct with time during storage at T = 298 K. These data were furthermore used to explain the unexpected shift of the β-process towards higher frequencies (shorter relaxation times) during aging experiments performed on CG and QG at room temperature. Results presented herein clearly show that the characteristic liquid crystalline ordering can be significantly affected not only by the temperature variation but also by the density changes.

Synergistic effect of Ag and ZnO nanoparticles on polyaniline incorporated epoxy/2pack coatings for splash zone applications

In this work, epoxy/2pack coatings containing polyaniline (PANI) in combination with Ag and ZnO nanoparticles have been synthesized. The nanoparticles were incorporated with bisphenol-A diglycidyl ether epoxy resin and polyamino-amide. The mechanical properties of the fabricated coatings, such as the pendulum hardness, scratch resistance, and impact strength, were studied. The composition of the fabricated coatings was confirmed by attenuated total reflectance infrared spectroscopy measurements. The thermal degradation and indentations were characterized through the use of differential scanning calorimetry and nano-indentation techniques, respectively. The surface morphology of the fabricated coatings was characterized using field-emission scanning electron microscopy. The synergistic effects of the Ag and ZnO nanoparticles on the corrosion resistance of the coatings after different exposure periods in 3.5% NaCl solutions were determined by electrochemical impedance spectroscopy. All the results were consistent with one another and confirmed that the addition of Ag and ZnO nanoparticles improved the mechanical properties of the coatings. This effect also led to a notable increase in the corrosion resistance of the PANI coatings.

Value of DSC in Characterization and Optimization of Protein Stability.

Differential scanning calorimetry (DSC) is a well-established technique for biomolecular stability studies. The technique is based on forced thermal denaturation of biomolecules in solution. Here we describe the use of DSC for characterization and optimization of stability of two proteins, a protein kinase and a mAb protein.

Enhancing the Pharmaceutical Behavior of Nateglinide by Cocrystallization: Physicochemical Assessment of Cocrystal Formation and Informed Use of Differential Scanning Calorimetry for Its Quantitative Characterization

The aim of this study was to synthetize cocrystals of nateglinide, an antidiabetic agent of biopharmaceutics classification system Class IIa, as a strategy to improve both the solubility and the dissolution rate of the drug. Benzamide was selected by a screening procedure as a suitable coformer, and binary mixtures with different compositions were prepared and analyzed by differential scanning calorimetry (DSC). An in-depth analysis of DSC data allowed obtaining both the eutectic mixture and cocrystal compositions. The rationale of such an analysis was highlighted and explained. Cocrystals were prepared by kneading and solvent evaporation. Their formation was proved by DSC and confirmed by X-ray powder diffraction, solid-state nuclear magnetic resonance, and Fourier-transform infrared spectroscopy. The functional groups involved in the interaction leading to cocrystals formation were investigated by spectroscopic techniques. The in vitro dissolution profiles show that cocrystals have definite better pharmaceutical performances than the pure drug.

Caffeoyl maleic fatty alcohol monoesters: Synthesis, characterization and antioxidant assessment

HypothesisCaffeoyl malate anhydride, as a good nucleophilic acceptor, can react with lipophilic fatty alcohols to yield interface-confined amphiphiles. The resulting novel molecules are hypothesized to deliver combined functionalities of parent natural building blocks, as emulsifier, stabilizer, ion chelator and free radical scavenger. ExperimentsRing-opening reactions of caffeoyl malate anhydride with fatty alcohols of different chain lengths generated a new group of antioxidant amphiphiles. Structural verification was by MS (mass spectrometry), 1H/13C NMR (nuclear magnetic resonance) and FT-IR (Fourier transform infra-red) spectroscopy. Physicochemical characterization was done by use of DSC (differential scanning calorimetry), FT-IR, determinations of critical micelle concentrations (CMC) and calculations of HLB. Antioxidant activity was assessed by DPPH (2, 2-diphenyl-1-picrylhydrazyl) and hydroxyl radical scavenging activities. Dynamic light scattering (DLS) studies demonstrated surface-activity of G8–G18. Inhibition of iron- and thermally-accelerated lipid oxidation was monitored by thiobarbituric acid reactive substances (TBARS) assay. FindingsDerivatization of caffeoyl malate anhydride with fatty alcohols maintained free radical scavenging activity, and improved hydroxyl radical scavenging activity of caffeic acid. Lipid oxidation at 22 °C was significantly inhibited (up to 3.5 times) in emulsions stabilized by G8–G18 with or without chitosan compared to emulsions stabilized by commercial emulsifiers and stabilizers. Thermal oxidation (at 80 °C) was 10 times less in emulsions facilitated by G8–G18 in combination with chitosan compared to emulsions stabilized by commercial emulsifiers and stabilizers. This study has developed a simple and straightforward approach for developing value-added compounds from underexplored fatty alcohols.

Separation of metal and plastic wastes from wire and cable manufacturing for effective recycling

The trend to recycle materials in industry has increased over the last few years as manufacturers seek ways to decrease material costs and reduce their environmental footprints. In the wire and cable manufacturing industry, excess wire and cable is shredded into a mixture commonly known as fluff. Because fluff is comprised of different metals as well as polymers of varying physical and chemical properties, it cannot be recycled into a usable product until the different components comprising fluff have been separated. Metallic components could possibly be used for recovery of metals from zinc-carbon and alkaline spent batteries. However, the amount of metals in fluff is low from the economical point of view. Polymeric components might be used in the production of aggregate in concrete – considered for this application together with fly ash. We have employed different concentrations and combinations of frothers, wetting agents, and inorganic materials, encouraging the separation of the different components of fluff by taking advantage of each component’s physical properties. An essential stage of the operation was separating metals from polymers. Among polymers, the main component of fluff was PVC – that we successfully reclaimed and then verified our results through the use of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Success in this endeavor would spell dramatic reductions in unrecyclable wire and cable waste, increase reclamation of materials, and further improve our understanding of the pros and cons of different density-based separation methods.

Controlled Syntheses of Poly(phenylene ethynylene)s with Regiochemically-Tuned Optical Band Gaps and Ordered Morphologies

A series of well-defined poly(phenylene ethynylene)s (PPEs) comprised of para- and/or meta-substituted monomers was synthesized and characterized. With use of a modified catalyst transfer method, the requisite polymerization reactions were found to proceed in a chain growth manner which enabled control over polymer molecular weight while maintaining a low polydispersity. In addition, varying the monomer feed ratio afforded copolymers with tunable regiochemistry and consequent electronic properties. The methodology was found to be general and successfully combined with an isocyanide polymerization reaction to prepare the respective diblock copolymers. With use of differential scanning calorimetry in conjunction with atomic force microscopy, the copolymers were found to adopt ordered, phase-separated morphologies in the solid state.

Combined use of DSC, TGA, XDR and NIR in the compatibility study of preformulation mixtures for the development of 10 mg tablets of Rupatadine Fumarate

It is essential to guarantee physico-chemical compatibility between the active pharmaceutical ingredient (API) and the components that are planned to be used in the development of a pharmaceutical formulation. A successful compatibility study allows to distinguish between the excipients that can be used and those that may represent a risk in the quality, safety and efficacy of the medication. The present study focuses on the identification of possible incompatibilities between Rupatadine fumarate and the excipients of three formulation prototypes for the development of API´s 10 mg tablets. Samples of each raw material, placebos and preformulation mixtures were analyzed by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XDR) and infrared spectroscopy (IRS). The results obtained were analyzed and contrasted with the literature. Based on these, it is demonstrated that the excipients used along with the API do not generate problems in terms of compatibility, as there are no chemical changes in the drug. Keywords: Active pharmaceutical ingredient, Chemical incompatibility, Compatibility study, Differential scanning calorimetry, Infrared spectroscopy, Preformulation powder mixtures, Rupatadine fumarate, Thermal analysis, Thermogravimetric analysis, X ray diffraction.

Synthesis and interaction of sterol-uridine conjugate with DMPC liposomes studied by differential scanning calorimetry.

Differential scanning calorimetry (DSC) is a thermoanalytical technique which provides information on the interaction between drugs and models of cell membranes. Studies on the calorimetric behavior of hydrated phospholipids within liposomes are employed to shed light on the changes in the physico-chemical properties when interacting with drugs. In this report, new potential anti-cancer drugs such as uridine and uridine derivatives (acetonide and its succinate), 3β-5α,8α-endoperoxide-cholestan-6-en-3-ol (5,8-epidioxicholesterol) and conjugate (uridine acetonide-epidioxicholesterol succinate) have been synthesized. Steglich esterification method using coupling agents allowed to obtain the uridine acetonide-sterol conjugate. The study on the interaction between the drugs and dimiristoyl-phophatidilcholine (DMPC) liposomes has been conducted by the use of DSC. The analysis of the DSC curves indicated that the uridine and derivatives (acetonide and its succinate) present a very soft interaction with the DMPC liposomes, whereas the 5,8-epidioxicholesterol and the conjugate showed a strong effect on the thermotropic behavior. Our results suggested that the lipophilic character of uridine acetonide-sterol conjugate improves the affinity with the DMPC liposomes.

Differential scanning calorimetry study of early and advanced stages in Parkinson’s disease using human blood serum

The study evaluates the use of differential scanning calorimetry (DSC) in differentiating the severity of Parkinson’s disease (PD). The heat capacity profiles and thermodynamic parameters of serum denaturation transition in advanced PD deviate significantly from the age-matched healthy controls. Unfortunately, blood serum calorimetry does not indicate the early stages of the disease. The amplitude of the main transition and the enthalpy of serum denaturation are significantly reduced with advanced disease. Statistically significant, inverse correlations have been found between these parameters and age as well as disease severity. Significantly higher mean temperature of the second transition at about 70 C, has been observed for PD patients in comparison with healthy participants but only small its deviations have appeared across disease groups. Results of the study indicate that DSC can be used as complementary bioanalytical tool for the monitoring of disease-related changes in serum and PD progression.

Use of DSC in degree of conversion of dimethacrylate polymers: easier and faster than MIR technique

This work aims to determine the degree of conversion of polymers obtained using diurethane dimethacrylate (UDMA) monomer by two different techniques: differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (MIR). The measurements were made in triplicate on both equipment, which resulted in average values for MIR 79.52 ± 3.57% (camphorquinone photoinitiator) and 78.15 ± 1.86% (fluorescein photoinitiator) and for DSC 80.85 ± 1.06 and 78.27 ± 1.71%. The DSC technique showed higher accuracy and lesser standard deviation. Furthermore, this technique is easier and faster than the MIR, and in situ polymerization is not necessary on the DSC equipment.

Hydrophobic and hydrophilic effects on water structuring and adhesion in denture adhesives.

Denture adhesives are designed to be moisture-sensitive through the inclusion of a blend of polymer salts with varying degrees of water-sensitivity. This enables the adhesive to mix with saliva in vivo and activate its high tack, through the formation of a mucilaginous layer. We report for the first time, the use of differential scanning calorimetry to study a series of hydrophobic and hydrophilic polymeric systems in order to correlate water-structuring behavior with adhesion strength. Adhesive bonding of the more hydrophobic variants was higher than that of a commercial-based control and a more hydrophilic polymer system in both lap shear and tensile configurations. Water-binding data suggested that increasing the hydrophobicity of the maleic acid copolymer substituents led to decreased levels of freezing water. In comparison, increasing the hydrophilic nature of the polymer backbone gave higher levels of freezing water within the hydrated samples. The results of this study emphasize the importance of varying the levels of hydrophobic and hydrophilic components within denture adhesive formulations, alongside the types of water present within the adhesive systems. This phenomenon has shown the potential to fine-tune the adhesive properties and failure mode against poly(methyl methacrylate), surfaces. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1355-1362, 2018.

Evaluating the Use of Differential Scanning Calorimetry for the Analysis of Illicit Substances and Their Adulterants

Evaluating the Use of Differential Scanning Calorimetry for the Analysis of Illicit Substances and Their Adulterants