Differential Scanning Calorimetry Scans Research Articles

Reorganization of Poly(Butylene Succinate) Containing Crystals of Low Stability.

Poly(butylene succinate) (PBS) forms small and imperfect crystals of low melting temperature at high supercooling of the melt. Slow heating allows reorganization of the obtained semicrystalline structure with the changes of the crystallinity and of the size and perfection of crystals analyzed by differential scanning calorimetry (DSC) and temperature-resolved X-ray scattering techniques. Crystals generated at 20 °C begin to melt and reorganize at a few K higher temperature with their initial imperfection and thickness unchanged upon heating to 70-80 °C. Slow heating to temperatures higher than 70-80 °C yields a distinct exothermic peak in the DSC scan, paralleled by detection of crystals of larger size/higher perfection, beginning to melt at ≈100 °C. These observations suggest that below 70-80 °C, reorganization of the semicrystalline morphology is constrained such that only minor and local improvement of the structure of crystals are possible. The formation of both perfect and thicker crystal lamellae at higher temperature proceeds via melting of imperfect crystals followed by melt-recrystallization as for PBS solid-state thickening is impossible. The study shows the limit of low-temperature reorganization processes when not involving both complete melting of crystals and rearrangement of the lamellar-stack structure.

The glass transition temperature of anhydrous amorphous calcium carbonate

Abstract Amorphous calcium carbonate (ACC) is the least stable polymorph of calcium carbonates. It has been identified to play an important role in nature (e.g., biomineralization and speleothem formation), where it acts as a precursor for the transformation to more stable polymorphs such as calcite. Furthermore, the use of ACC in technical applications requires a robust understanding of the material’s properties. We present the first study that reveals the existence of a glass transition for synthetic and anhydrous ACC. The glass transition occurs at 339 °C. Such measurements are impossible with conventional differential scanning calorimetry (DSC) due to the high tendency of ACC to crystallize. Fast scanning DSC with heating rates of 500 °C/s and higher, however, can be used to separate the endothermic glass transition signature from the exothermic crystallization event since crystallization is shifted to higher temperatures. This allows the detection and quantification of the glass transition for ACC. These observations indicate that ACC is a structural glass and are especially significant because the synthesis of ACC, precipitation from a solution followed by lyophilization, contrasts with the more conventional and well-known route of glass formation–the rapid cooling of a melt. Moreover, we prove that a structural glass can be produced from a simple single-component carbonate system.

Investigating the impact of PACAP on thermal stability of G-actin by differential scanning calorimetry

AbstractPituitary adenylate cyclase-activating polypeptide (PACAP) is a bioactive peptide known for its diverse effects on the nervous system. While numerous studies have demonstrated the neuroprotective properties of PACAP, its role in tissue regeneration and potential as a therapeutic agent remain to be fully understood. Specifically, the understanding of PACAP’s impact on cytoskeletal dynamics, particularly the organization and disorganization of actin filament networks, is limited due to the scarcity of in vitro studies in this area. Additionally, the interaction between PACAP and actin has been minimally explored, and the influence of PACAP on the thermal stability of actin is completely unknown. To address these gaps, the current study aimed to investigate the impact of different forms and fragments of PACAP on the thermal denaturation and renaturation of Ca2+-G-actin using a differential scanning calorimetry (DSC) approach. Our primary objective was to determine whether PACAP modulates the thermal stability of Ca2+-G-actin and establish a temperature-dependent pattern of any structural alterations that may occur as a result of PACAP interaction. Two PACAP forms exist in vivo: the 38 amino-acid length PACAP38 and the PACAP27, the latter truncated at the C-terminal. In the PACAP38 + Ca2+-G-actin mixture, the DSC scans exhibited a mild decrease in actin denaturation temperature compared to the control, plus an exotherm appeared in the high-temperature range with a significantly increased calorimetric enthalpy. The truncated PACAP27 produced a slight increase in actin denaturation temperature with the same exotherm without significant alteration in enthalpy. In PACAP6-38 mixture (i.e., an artificial fragment of PACAP38 + Ca2+-G-actin), there was no change in the denaturation temperature of actin and no plus exotherm, but significant ΔHcal was observed. With the modified PACAP6-27 (another artificial fragment), the exotherm was absent, but the actin denaturation temperature and enthalpy increased compared to the control. Through this research, we sought to elucidate the underlying mechanisms of PACAP’s effects on actin dynamics and provide valuable insights into the potential therapeutic applications of PACAP in the context of cytoskeletal organization and neuronal regeneration. The findings of this study may contribute to the development of novel strategies targeting actin-related processes for neuroprotection and neural tissue repair.

Exploring the response of PACAP on thermal endurance of F-actin by differential scanning calorimetry

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a bioactive peptide known for its diverse effects on the nervous system. While numerous studies have demonstrated the neuroprotective properties of PACAP, its role in tissue regeneration and potential as a therapeutic agent remain to be fully understood. Specifically, the understanding of PACAP’s impact on cytoskeletal dynamics, particularly the organization and disorganization of actin filament networks, is limited due to the scarcity of in vitro studies in this area. Additionally, the interaction between PACAP and actin has been minimally explored, and the influence of PACAP on the thermal stability of actin is completely unknown. To address these gaps, the current study aimed to investigate the impact of different forms and fragments of PACAP on the thermal denaturation and renaturation of Ca2+-F-actin using a differential scanning calorimetry (DSC) approach. Our primary objective was to determine whether PACAP modulates the thermal stability of Ca2+-F-actin and establish a temperature-dependent pattern of any structural alterations that may occur as a result of PACAP interaction. Two PACAP forms exist in vivo: the 38 amino acid length PACAP38 and the PACAP27, the latter truncated at the C-terminal. Both in the PACAP38 + Ca2+-F-actin and in the PACAP6-38 + Ca2+-F-actin mixtures, the DSC scans exhibited a significant decrease of actin denaturation temperature compared to the control; however, the PACAP27 + Ca2+-F-actin and PACAP6-27 + Ca2+-F-actin revealed no remarkable differences compared to the actin control sample. The calorimetric enthalpy of the truncated PACAP27 and PACAP6-27 + actin mixture also followed the tendencies mentioned above. Thus, in PACAP27 and PACAP6-27 mixture, there was no change in the denaturation temperature of actin, and no significant ΔHcal was observed. Through this research, we sought to elucidate the underlying mechanisms of PACAP’s effects on actin dynamics using thermal de- and renaturation cycles.

Thermal Stability, Crystallization, and Melting Behaviours of Iodine Doped Semiconducting Polyethylene Terephthalate (PET) Thin Films

The influence of iodine doping on the thermal stability, degradation kinetics, and the melting and crystallization behaviors of polyethylene terephthalate (PET) films were investigated. Iodine doping was performed by immersing PET films in 0.4 M I2/l toluene. The thermal stability and degradation kinetics of PET and the semi-conducting PET/iodine complex films were studied using the thermogravimetric analysis-derivative thermogravimetric analysis (TGA-DTGA) studies and the differential scanning calorimetry (DSC). It was found that iodine incorporation accelerated the thermal degradation and weight loss through increased chain mobility owing to the imperfections formed by doping. Both pure and doped films exhibited appreciable thermal stability with the peak degradation temperature above 400 °C. DSC thermograms of the pristine PET and the PET/iodine films in the crystallization regions were recorded during the cooling scan and the significant parameters were studied. The peak crystallization temperature of PET increased from 192 to 209 °C after iodination. Doping initiated crystallization at an early stage of cooling with an increase in the rate of crystallization and smaller crystallization half time. Iodine catalyzed crystallization and acted as a nucleating agent. DSC scans were also used to study the melting characteristics of the polymer samples. The peak melting temperature was lower and the absolute crystallinity reduced for the iodine doped PET films.

Synthesis, curing, and degradation kinetics of polyurethanes based on poly(ethylene glycol), isosorbide, and pentamethylene diisocyanate

AbstractPolyurethane (PU) synthesis based on poly(ethylene glycol) (PEG) with isosorbide (ISO) and pentamethylene diisocyanate (PDI), named (ISOPUs) was carried out targeting PUs from renewable sources. The cross‐linked ISOPUs were produced and the details of the curing kinetics were determined via Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). DSC scans displayed exotherms between 100 and 200°C, related to cross‐linking. ISO addition accelerated the curing and the maximum curing rate (Cmax), with 91°C and 0.2964 min−1 for the compound with 70% ISO. FTIR spectra confirmed the interaction between OH (ISO/PEG) and NCO (PDI) groups, with total NCO consumption (band at 2267 cm−1). Through the thermogravimetric analyses (TGA), the PU/70% ISO presented weight loss at 146°C due to the degradation of ISO. ISOPUs displayed a decreased activation energy (Ea) during curing over a range of 100 to 42 kJ/mol for 0 < α < 5%, as demonstrated using the Friedman model, and higher thermal stability as evidenced through TG analyses. Curing and degradation kinetics were modeled using Friedman (FR), Kissinger‐Akahira‐Sunose (KAS), and Ozawa‐Flynn‐Wall (OFW). Overall, ISO accelerated the curing rate and increased the degradation Ea, suggesting high thermal stability for PUs with intermediate ISO contents, that is, 30%–50%.

Effects of Accelerating the Ageing of 1D PLA Filaments after Fused Filament Fabrication.

The effects of post-treatment temperature-based methods for accelerating the ageing of PLA were studied on 1D single-PLA filaments after fused filament fabrication (FFF). The goal was to answer the questions whether the PLA can be safely aged-i.e., without degrading-at higher temperatures; at which temperatures, if any; how long it takes for the PLA to fully age at the chosen temperature; and which are the main differences between the material aged at room temperature and the material aged at higher temperatures. We also share other helpful information found. The use of 1D filaments allows for decoupling the variables related to the 3D structure (layer height, raster angle, infill density, and layers adhesion) from the variables solely related to the material (here, we analysed the molecular weight, the molecular orientation, and the crystallinity). 1D PLA filaments were aged at 20, 39, 42, 51, 65, 75, and 80 °C in a water-bath-inspired process in which the hydrolytic degradation of the PLA was minimised for the ageing temperatures of interest. Those temperatures were selected based on a differential scanning calorimetry (DSC) scan of the PLA right after it was printed in order to study the most effective ageing temperature, 39 °C, and highlight possible degradation mechanisms during ageing. The evolution of the thermal and mechanical properties of the PLA filaments at different temperatures was recorded and compared with those of the material aged at room temperature. A DSC scan was used to evaluate the thermal and physical properties, in which the glass transition, enthalpic relaxation, crystallisation, and melting reactions were analysed. A double glass transition was found, and its potential implications for the scientific community are discussed. Tensile tests were performed to evaluate the tensile strength and elastic modulus. The flow-induced molecular orientation, the degradation, the logistic fitting, and the so-called summer effect-the stabilisation of properties at higher values when aged at higher temperatures-are discussed to assess the safety of accelerating the ageing rate and the differences between the materials aged at different temperatures. It was found that the PLA aged at 39 °C (1) reached almost stable properties with just one day of ageing, i.e., the ageing rate accelerated by 875% for the elastic modulus and by 1635% for the yield strength; (2) the stable properties were higher than those from the PLA aged at room temperature; and (3) no signs of degradation were identified for the ageing temperature of interest.

Description of non-isothermal crystallization kinetics of Fe48Co32P14B6 metallic glass using the isothermal analysis data

The non-isothermal crystallization kinetics of Fe48Co32P14B6 glass was experimentally studied by differential scanning calorimetry (DSC) at heating rates from 5 to 40 K/min. The integral form of the non-isothermal glass crystallization kinetic equation based on the combination of the Kolmogorov's model of mass crystallization kinetics and the Kashchiev's transient nucleation approach involving the classical equations for nucleation rate and growth velocity was derived. The kinetic model describing the interface-controlled mode of crystallization in a wide range of the nucleation rate deviations from its steady-state value involves only the first terms of the Kashchiev's infinite series and of the series obtained by re-summation. Using the thermodynamic and kinetic parameters and their temperature dependencies derived from analysis of the isothermal crystallization of the glass investigated [Vasiliev et al, J. Alloys and Compds. 869 (2021) 159,285] the experimental DSC scans were correctly approximated in the frames of the proposed kinetic model. The values of the transient of nucleation rates at continuous heating were estimated and the effect of non-stationarity on thermal stability of metallic glasses was discussed.

Effect of hardener and catalyst contents on curing and degradation of epoxidized soybean oil

AbstractEpoxidized soybean oil (ESO) compounds were cured with methyl tetrahydrophthalic anhydride (MTHPA) as hardener and 2,4,6‐tris (dimethylaminomethyl) phenol (DEH 35) as catalyst. To figure out MTHPA and DEH 35's influence during curing and degradation, ESO/MTHPA/DEH 35 compounds were investigated using Fourier‐Transform Infrared Spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetry (TG). FTIR spectra of uncured resin showed the secondary interactions among ESO's carbonyl groups with MTHPA and DEH 35's hydroxyls and amines. Curing progress was followed tracking the evolution of reactive groups, that is, epoxy and carbonyl bands and corroborated with released heat of DSC scans. ESO 87:5 and ESO 87:10 compounds cured using higher heating rates presented higher released enthalpy suggesting denser reticulation, and they also displayed lower activation energy for curing, which was evaluated using the Friedman model. Increasing the hardener and catalysts contents promoted higher thermal stability and lower degradation rates, while higher for degradation was verified.

Enhanced miscibility of PBAT/PLA/lignin upon γ‐irradiation and effects on the non‐isothermal crystallization

AbstractLignin is natural and renewable polymer, the second most abundant on Earth. Properly used it can reduce synthetic and oil based materials in addition to contributing to the biodegradable systems. In this work, the kraft lignin was subjected to gamma radiation at absorbed doses of 30, 60, and 90 KGy in order to increase the interaction with “Poly(butylene adipate‐co‐terephthalate) (PBAT)/Poly(lactic acid) (PLA)” blend (Ecovio®). PBAT/PLA/lignin blends with 10% of the weight of lignin were produced by extrusion using twin‐screw extruder and characterized by Fourier transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC), and Field emission scanning electron microscopy (FE‐SEM). FTIR spectra showed partial miscibility between PBAT/PLA and lignin, most due to the hydrogen bond between PBAT/PLA carbonyl and lignin hydroxyl, being intensified in irradiated lignin compounds. As evidenced on DSC scans, in PBAT/PLA/irradiated lignin the crystallization peak was shifted to lower temperatures and the crystallization rate decreased. Crystallization kinetics was modeled using Pseudo Avrami, and isoconversional models of Friedman and Vyazovkin. Pseudo‐Avrami displayed linearity deviation at beginning and crystallization ending due to the nucleation and secondary crystallization, while from Friedman and Vyazovkin the activation energy () was higher for PBAT/PLA/irradiated lignin 30 KGy, characterizing crystallization with higher energy consumption. FE‐SEM images showed better dispersion and miscibility in PBAT/PLA/irradiated lignin. The results indicate that the irradiation of Kraft lignin promotes miscibility and compatibility of PBAT/PLA/lignin.

Phase behavior and heat capacity of alkylboron-capped cobalt (II) and nickel (II) clathrochelates

For understanding of properties of transition metal complexes with d-electrons of 4–7, the n-butylboron-capped macrobicyclic nickel (II) and cobalt (II) tris-dioximates have been synthesized using the direct template condensation method. The two compounds were characterized using elemental analysis, differential scanning calorimetry (DSC), thermogravimetry (TG), X-ray diffraction, and relaxation calorimetry. They formed triclinic crystals at low temperatures and room temperature. In the DSC scan, only the nickel complex showed a first-order phase transition at 269.3 K with a latent heat of 1.67 J g−1. TG analysis displayed several stages of weight loss in them, starting from above 510 K. Heat capacities of the two complexes did not exhibit anomalies in very low temperature region, while a broad heat-capacity hump was observed above 120 K, correlated to the movements of the alkyl chains.

Temperature control and intermittent time-set protocol optimization for minimizing tissue carbonization in microwave ablation

Purpose The charring tissue formation in the ablated lesion during the microwave ablation (MWA) of tumors would induce various unwanted inflammatory responses. This paper aimed to deliver appropriate thermal dose for effective ablations while preventing tissue carbonization by optimizing the treatment protocol during MWA with the set combinations of temperature control and pulsed microwave energy delivery. Material and methods The thermal phase transition of ex vivo porcine liver tissues were recorded by differential scanning calorimetry (DSC) to determine the temperature threshold during microwave output control. MWA was performed by an in-house built system with the ease of microwave output parameter adjustment and real-time temperature monitoring. The effects of continuous and pulsed microwave deliveries as well as various intermittent time-set of MWA were evaluated by measuring the dimensions of the coagulation zone and the carbonization zone. Results The DSC scans demonstrated that the ex vivo porcine liver tissues have been in a state of endothermic heat during the heating process, where the maximum absorbed heat occurred at the temperature of 105 °C ± 5 °C. The temperature control during MWA resulted in effective coagulative necrosis while preventing tissue carbonization, after setting 100 °C as the upper threshold temperature and 60 °C as the lower threshold. Both the numerical simulation and ex vivo experiments have shown that, upon the optimization of the time-set parameters in the periodic intermittent pulsed microwave output, the tissue carbonization was significantly diminished. Conclusion This study developed a straight-forward anti-carbonization strategy in MWA by modulating the pulsing mode and intermittent time. The programmed protocols of intermittent pulsing MWA have demonstrated its potentials toward future expansion of MWA technology in clinical application.

Saliva profiling with differential scanning calorimetry: A feasibility study with ex vivo samples

Differential scanning calorimetry (DSC) has been used widely to study various biomarkers from blood, less is known about the protein profiles from saliva. The aim of the study was to investigate the use DSC in order to detect saliva thermal profiles and determine the most appropriate sampling procedure to collect and process saliva. Saliva was collected from 25 healthy young individuals and processed using different protocols based on centrifugation and filtering. The most effective protocol was centrifugation at 5000g for 10 min at 4°C followed by filtration through Millex 0.45 μm filter. Prepared samples were transferred to 3 mL calorimetric ampoules and then loaded into TAM48 calibrated to 30°C until analysis. DSC scans were recorded from 30°C to 90°C at a scan rate of 1°C/h with a pre-conditioning the samples to starting temperature for 1 h. The results show that the peak distribution of protein melting points was clearly bimodal, and the majority of peaks appeared between 40–50°C. Another set of peaks is visible between 65°C– 75°C. Additionally, the peak amplitude and area under the peak are less affected by the concentration of protein in the sample than by the individual differences between people. In conclusion, the study shows that with right preparation of the samples, there is a possibility to have thermograms of salivary proteins that show peaks in similar temperature regions between different healthy volunteers.

Thermally Stable Copolymers with Pendant “N-Arylimide” Groups Via Reversible Deactivation Radical Polymerization Technique

This paper reports the synthesis of copolymers of N-arylitaconimides (NAI) and methyl methacrylate (MMA) with random architecture via activator generated electron transfer atom transfer radical polymerization (AGET-ATRP) method, resulting in N-arylimide as pendant group.The AGET-ATRP is a versatile and famous reversible deactivation radical polymerization technique used to synthesize the well defined polymers. The structural characterizations of obtained copolymers were done using FT-IR, 1H-NMR spectroscopy and elemental analysis. The molecular weights of copolymers were in the range 8,000-20,000 g/ mol with a narrow polydispersity index i.e. 1.2-1.3. Thermal characterization of Poly(NAI-ran-MMA) copolymers were done using differential scanning calorimetry (DSC) and thermogravimetric analysis (TG/ DTG). DSC scans show 60-117% enhancements in the glass transition temperature (Tg), as compared to Poly(methyl methacrylate). The rate of copolymerization, molecular weight and Tg were observed to increase with increase in electron releasing nature of the substituent on aromatic ring of the pendant group.

Curing and morphology approaches of polyurethane/poly(ethylene glycol) foam upon poly(lactic acid) addition

AbstractThe effect of poly(lactic acid) (PLA) content on the curing of polyethylene glycol (PEG) based polyurethanes (PU) was investigated. Aiming to produce biobased PU foams, pentamethylene diisocyanate (PDI) was used. Fourier transform infrared spectroscopy (FTIR) found no curing evidence at 30°C and verified that the curing was completed at 300°C. This method tracks hydrogen bonding and NCO consumption. PLA addition decreased the curing rate as evidenced through differential scanning calorimetry (DSC) and promoted changes in the released heat which is linked to chemical and physical crosslinking. Complex peaks were verified in DSC scans whereas the peak at lower temperatures is related to the catalyzed curing while that in the higher ones is due to the homopolymerization. PU foams morphology was investigated using scanning electron microscopy (SEM). Pores and cell sizes are related to PLA content and hydrogen bonding.

Correlating thermal properties of polyurethane/clay nanocomposite coatings with processing

Phase morphology of polyurethane (PU) and its nanocomposites with Bentone 38 (B38) nano clay additive has been investigated and its effect on the thermal degradation behaviour has been evaluated. Two processing schemes were used to reinforce B38 into the matrix of PU in three different weight percentages (1, 2 and 3 wt%). The nanocomposite coatings show different formations (pyramid, sheet stacks etc.) of clay on the surface of the PU nanocomposite samples. The variable intensity of the key peaks in Fourier transform infrared spectroscopy (FTIR) confirms changes in the chemical interface between B38 clay-PU chains due to different processing schemes. The FTIR data was quantitatively derived to calculate the degree of phase separation (DPS) and the degree of phase mixing (DPM) and analyse the effect of this variation. “Cure index” calculations from differential scanning calorimetry (DSC) were used to analyse the cure state of the nanocomposites. The morphological studies through X-ray diffraction (XRD), atomic force microscopy (AFM) and optical microscopy (OM) highlight the variation in structures due to modified processing schemes. An improvement of around 34% (89 °C) is seen in the 20% weight loss temperature (Tg20) at a loading of just 1 wt% B38. DSC scans also show improved thermal properties. A shift of 14 °C (2 wt% B38) and 46 °C (1 wt% B38) respectively is observed in the degradation temperature from the heat flow scans w.r.t. the pristine PU. These results indicate that even at low clay loadings, properties can be significantly enhanced just by tweaking the processing scheme, thereby indicating the great sensitivity nanocomposites have to processing schemes.

DSC assisted kinetic analysis on the urethane network formation between castor oil based ester polyol and poly(methylene di phenyl isocyanate) (pMDI)

Kinetics of the reaction between castor oil based ester polyol (CEP) and poly(methylene di phenyl isocyanate) (pMDI) was studied adopting differential scanning calorimetry (DSC). DSC scans were recorded at various heating rates, viz.: 5, 10, 15 and 20 K.min−1. Hydroxyl and isocyanato compounds were taken at stoichiometric ratio [ Both single heating rate methods (Coats-Redfern, Chatterjee-Conrad) and multiple heating rate based iso-conversional methods (Ozawa, Freidman and Kissinger) were adopted to calculate the kinetic parameters. DSC thermograms consist of two exothermic peaks at temperatures 343 and 393 K, for all heating rates. Kinetic parameters were calculated using input parameters deduced from DSC thermogram. The reaction was assumed to be second order and the corresponding second order equations were applied for evaluating the kinetic parameters.

Effects of poly(diallyldimethylammonium chloride) addition on the curing kinetics of urea-formaldehyde adhesives for particleboards

Addition of poly(diallyldimethylammonium chloride) (PDDA) on the performances of urea-formaldehyde (UF) adhesives was evaluated in this work. Three types of UF adhesives were prepared, one without PDDA addition, and two types with PDDA addition of 1 and 3 wt.% per dry UF adhesive mass. These UF adhesive systems were used for producing experimental particleboard panels. The addition of PDDA decreased the thickness swelling of the panel samples, while the internal bond of the particleboards increased significantly only at the highest PDDA content (3 wt.%). Differential scanning calorimetry (DSC) was applied to address the influence of PDDA on UF adhesive curing kinetics. DSC scans were performed in non-isothermal regimes using different heating rates (5, 10, and 20 ?C?min?1). The activation energy (Ea) of the curing reaction showed slightly lower values for the UF adhesive systems containing PDDA. However, the peak temperatures and enthalpy of reaction did not change significantly. The Kissinger-Akahira-Sunose and Friedman iso-conversional methods were applied to investigate the effects of PDDA addition on the UF adhesive curing process.

Microstructure and thermal properties of the Bi–Ag alloys

Microstructure, melting behavior and thermal conductivities of three Bi–Ag alloys with 5, 20 and 45 mass% of Ag were experimentally studied in the present work. Phase morphology of the alloys was analyzed by the light microscopy and scanning electron microscopy with energy-dispersive X-ray spectrometry. Phase transition temperatures and their heat effects were measured using differential scanning calorimetry (DSC). The calculation of phase diagrams method was used for the computation of thermodynamic functions such as enthalpy and specific heat capacity of the investigated alloys. Experimentally obtained DSC heating scans were compared with the simulated DSC scans derived from thermodynamic data, and good mutual agreement was noticed. The flash method was used for determination of thermal diffusivity and thermal conductivity of the investigated alloys. It was found that increase in silver content to 45 mass% resulted in modest increase in thermal conductivity of the investigated alloys. Thermal conductivities for all three investigated eutectic alloys slightly decrease with increasing temperature.

Thermal performance enhancement of cementitious composite containing polystyrene/n-octadecane microcapsules: An experimental and numerical study

This paper experimentally and numerically investigated the thermal performance of cementitious composites containing polystyrene/n-octadecane microcapsules (MPCM-CCs). The focus was placed on the passive cooling and heating, and the peak load reduction and shifting of MPCM-CCs subjected to extreme temperature conditions (10–50 °C). Adding microcapsules with a latent heat of 142.9 J/g effectively improved the heat storage and thermal insulation performance of MPCM-CCs, thereby mitigating the temperature fluctuations of inner surface and indoor air by up to 17.5 °C and 10.7 °C, respectively. The peak load was reduced and shifted by up to 260 W/m2 and 675 s in the heating process (1130 s), and 436 W/m2 and 465 s in the cooling process (1750 s). Further, this study evaluated the influence of differential scanning calorimetry (DSC) scanning rate on the phase change properties of microcapsules and the consistency between the simulation and experimental results of MPCM-CCs. Due to the low thermal conductivity of polystyrene shell, the phase change temperatures of microcapsules varied significantly with DSC scanning rates. Consequently, the simulation results based on improper scanning rates deviated from the experimental results, which highlights the importance of considering the difference between the temperature change rates of building components and DSC analysis.