Melting Temperature Depression Research Articles

How the Aliphatic Glycol Chain Length Determines the Pseudoeutectic Composition in Biodegradable Isodimorphic poly(alkylene succinate-ran-caprolactone) Random Copolyesters.

We synthesize four series of novel biodegradable poly(alkylene succinate-ran-caprolactone) random copolyesters using a two-step ring-opening/transesterification and polycondensation process with ε-caprolactone (PCL) as a common comonomer. The second comonomers are succinic acid derivatives, with variations in the number of methylene groups (nCH2) in the glycol segment, nCH2 = 2, 4, 8, and 12. The obtained copolyesters were poly(ethylene succinate-ran-PCL) (ESxCLy), poly(butylene succinate-ran-PCL) (BSxCLy), poly(octamethylene succinate-ran-PCL) (OSxCLy), and poly(dodecylene succinate-ran-PCL) (DSxCLy). We discovered a new mixed isodimorphic/comonomer exclusion crystallization in ESxCLy copolymers. The BSxCLy, OSxCLy, and DSxCLy copolymers display isodimorphic behavior. Our findings revealed a significant variation in the pseudoeutectic point position, from mixed isodimorphism/comonomer exclusion crystallization to isodimorphism with pseudoeutectic point variation from 54% to up to 90%. Moreover, we established a link between the melting temperature depression slope variation and the comonomer inclusion/exclusion balance, providing valuable insights into the complex topic of isodimorphic random copolymers.

The Effect of Zr and Li on the Microstructure of AlMg5Si2Mn-Type Casting Alloys

AbstractIn the article, the authors present results of microstructural studies of Al-Mg-Si-Mn casting alloys with Zr, Li, and TiB2 additions on a broad scale. Zirconium content was set on two levels: 0.34 and 1.58 wt%, and Li was set 1.2 and 2.0 wt%. It was found that the addition of Zr shifts the eutectic melting temperature to a higher level, up to 611.3 °C at 1.6 wt% Zr. At the same time, Li addition leads to the depression of eutectic melting temperature: down to 587.2 °C at 2.0 wt% Li, what is a common effect of eutectic modification which was confirmed by means of structural examinations. The complex addition of Li and AlTi5B1 resulted in a eutectic melting temperature close to the equilibrium eutectic temperature for the Al-Mg-Si system (596.2 °C). The grain refinement effect of Zr is due to the nucleation of α-Al on the Zr(Al1−x, Six)3 phase. Crystals of this phase were detected in the grain centers of Zr-containing alloys. The Li addition does not affect α-Al grain size but changes the morphology of eutectic colonies from petal-like to fibrous. Observation of TiB2 particles inside the primary Mg2Si crystals gives direct experimental confirmation of nucleation of the primary phase on the surface of TiB2 in the alloy after adding Li and AlTi5B1. Natural aging of the alloys resulted in the formation of fine precipitates detected close to dislocations. The most apparent supposition is that the mechanism responsible for their formation is heterogeneous nucleation in the stress field of dislocations. Hardness tests showed adding 2.0 wt% of Li is very effective, increasing hardness up to 113 HV0.2 in naturally aged condition, which is nearly double that of commercial Al-Mg-Si die-casting alloy. Several effects were proposed which may synergistically contribute to the rise of hardness in Li-containing alloys, such as solid solution strengthening, formation of primary LiAlSi phase and natural aging.

Impact of aging on the phase behavior of cocoa butter and copra oil blends

Aging of cocoa butter (CB)/copra oil (CO) binary blends (noted CB/CO) is investigated through a multi-technique approach. Indeed, the phase behavior of non-aged and 30 days-aged cocoa butter/copra oil binary blends (CB/CO) at 4°C is studied, using a combination of Nuclear Magnetic Resonance (NMR), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD). During subsequent heating from 4°C to 40°C, solid fat content depression between 15°C and 20°C is shown with NMR, with the most pronounced occurring at two different compositions for the non-aged (60% CO addition in CB) and for the 30 days-aged mixtures (80% CO addition in CB). In agreement, DSC exposes melting enthalpy and melting temperature depression for the aged-blend 80/20 CB/CO. XRD highlights fat interactions at the nanoscopic scale and allows the precise attribution of polymorphic transitions perceived with DSC. The melt-mediated transformation of CB crystals from β'2-2L to β2-3L is shown in non-aged blends containing 0% to 10% of CO in CB, whereas it is shown to occur in blends containing 0% to 60% CO in CB for the 30 days aged-blends. As a result of this study, all the results obtained with the various methods are used to build the very first complete pseudo-phase diagram of 4°C-aged CB/CO blends, it highlights the shift of the eutectic points after 30 days of storage. We think that such a fundamental work can bring new understanding of a well-known issue as encountered in chocolate-based products storage.

Physical origins of freezing and melting temperature depressions of water in millimeter-sized pores

As a long-standing problem, the physics of freezing and melting temperature depressions of water in millimeter-sized pores remains elusive. We devised a series of experiments on the freezing and melting of water in glass tubes with varying tube diameters, water volumes, water-solid interfacial areas, and cooling rates. The results of the experiments indicate that the freezing temperature depression is highly correlated with the water-solid interfacial areas. It can be inferred that heterogeneous nucleation is the dominant physical origin for such freezing temperature depression. In contrast, melting temperature depression is orders of magnitude lower than that of freezing, and is independent of heating rate, water volume, water-solid interfacial area, and correlated with pore diameter, suggesting the governing role of capillarity. The recognized distinct physical origins of freezing and melting temperatures lead to the disparity between them, i.e., freezing and melting hysteresis. The findings resolve the controversy on the freezing mechanism of water in millimeter-sized pores, and can be used to better manipulate freezing and melting behaviors of pore water in various engineering applications, e.g., promoting or inhibiting freezing in biomaterials, and developing anti-freezing materials.

Melting Point of a Confined Fluid within Nanopores: The Composition Effect on the Gibbs-Thomson Equation.

The Gibbs-Thomson (GT) equation finds that the shift in the freezing/melting temperature under confinement with respect to its bulk counterpart is inversely proportional to the pore size. This century old relation successfully elaborates the freezing experiments of many fluids (e.g., water, molten salt), while it fails in quantitatively predicting the phase stability of the nonstoichoimetric crystals (e.g., gas hydrates). Based only on the crystal/liquid coexistence, we here revisit the GT equation to treat the multicomponent compounds within a slit confined geometry. In addition to the interfacial energy contribution, the extended GT equation accounts for the excess free energies associated with the composition variations upon the freezing/melting transition. Using the direct coexisting method (DCM), we first probe the melting temperatures of a face-centered cubic (fcc) crystal confined in slit pores as well as its bulk counterpart. The melting temperature under confinement is shown to be depressed compared to the bulk. We then turn to estimate the parameters entering the GT equation using several independent molecular simulations. The melting temperature depression observed in the DCM simulations is found to be well described by the GT equation if used with accurate estimates of the pore/crystal and pore/liquid interfacial tensions. Finally, using the above molecular modeling strategies, we show that the GT equation with the composition correction successfully predicts the shifted melting temperature of methane hydrate confined in porous solids. For such nonstoichoimetric compounds under confinement, accounting for the composition effects is of utmost importance as it exhibits a non-negligible contribution to the GT description. The extended GT equation can be expected to investigate the capillary freezing of the nonstoichoimetric compound in nanopores and to provide a better understanding of the pore body.

Frustrated crystallization behavior under hierarchical confinement in electrospun fibers of poly(styrene)/poly(ethylene oxide)/poly(l‐lactide) ternary mixtures

AbstractThe crystallization behavior of binary crystalline mixtures composed of poly(ethylene oxide) (PEO) and poly(l‐lactide) (PLLA) was investigated in the electrospun nanofibers fabricated by the ternary blends of polystyrene (PS), PEO, and PLLA. The weight fraction of PEO/PLLA mixture was kept at ≤0.2 such that PS formed the matrix phase. The preferred mixing of PEO and PLLA resulted in the formation of mixed PEO/PLLA dispersed domains in the PS matrix. The small diameter of the electrospun nanofibers restricted the size of dispersed domain. During cooling from melt, PLLA crystallized first resulting in crystallization induced phase separation and entrapment of PEO within the intracrystalline regions of PLLA crystals. Hence, whereas the PLLA crystallized within the soft PS matrix, the crystallization of PEO occurred within the hierarchical confinement imposed by the PLLA crystals as well as the glassy PS matrix. Interestingly, it was found that the confinement favored the formation of α crystals phase in PLLA even at very low crystallization temperatures. Furthermore, due to plausible entrapment of PEO segments within the PLLA crystals, significant depression in PLLA melting temperature was observed. Moreover, the PEO melting temperature also depressed by more than 30°C due to the frustrated crystallization within the hierarchical confinement.

Catalytic Control of Crystallization in Dynamic Networks.

The effect of catalysts with varying nucleophilic strength on thiol-thioester bond exchange dynamics and concomitant crystallization was studied in a model semicrystalline polymer network. It was found that the characteristic time scale of covalent bond exchange, τ, could be tuned over a ∼101-103 s range simply by changing the nucleophilicity of the catalyst. Using isothermal crystallization measurements via differential scanning calorimetry, thermodynamic and kinetic features of crystallization were considered. A depression in melting temperature was observed with increasing bond exchange rate, suggesting a dependence of crystalline organization on network dynamics. Furthermore, a systematic slowing of crystallization kinetics with faster covalent bond exchange rates was observed. Lauritzen-Hoffman analysis showed a near doubling in the barrier for secondary nucleation for dynamic networks, suggesting that that bond exchange slows crystallization by limiting secondary nucleation and further growth. Finally, longitudinal DSC studies reveal a long-term increase in melting temperature for samples held at ambient temperature with bond exchange activated at room temperature, indicating that while bond exchange slows crystallization on short time scales it facilitates isothermal long-term crystal rearrangement and growth on longer time scales.

Immobilization of Technetium-99 in a Lead Borosilicate Glass

The volatility of Technetium-99 (99Tc) makes vitrification of Tc-containing nuclear waste at high temperatures a challenge. In this paper, we report the development of a lead borosilicate glass with a nominal composition of 73.1PbO–10.1B2O3–13.1SiO2–3.7Al2O3 (wt%) and a depressed melting temperature (750 °C) to decrease Tc volatilization during vitrification. The lead borosilicate glass was able to incorporate up to ∼1.8 wt% Re (as a surrogate for 99Tc), and the results of a product consistency test showed that it was chemical durable. Raman and Fourier transform infrared spectra showed that Re was incorporated into the lead borosilicate network as ReO4− and the small addition of Re did not induce any detectable changes to the B and Si network. At the same time, nuclear magnetic resonance measurements suggested that some of the ionic Pb in the glass turned to covalent Pb with the addition of KReO4. No loss of Re was detected when vitrification of the Re-containing lead borosilicate glass was conducted at 750 °C, and only ∼12% of the Re volatilized when the temperature was ramped up to 1100 °C. Our findings confirm suggestions that lead borosilicate glass would be an attractive candidate waste form for immobilizing Tc concentrate.

Phytosterols and γ-Oryzanol as Cholesterol Solid Phase Modifiers during Digestion.

Literature reports that ingestion of phytosterols and γ-oryzanol contributes to cholesterol lowering. Despite in vivo observations, thermodynamic phase equilibria could explain phenomena occurring during digestion leading to such effects. To advance the observations made by previous literature, this study was aimed at describing the complete solid-liquid phase equilibrium diagrams of cholesterol + phytosterol and γ-oryzanol systems by DSC, evaluating them by powder X-ray, microscopy, and thermodynamic modeling. Additionally, this study evaluated the phenomena observed by an in vitro digestibility method. Results confirmed the formation of solid solution in the cholesterol + phytosterols system at any concentration and that cholesterol + γ-oryzanol mixtures formed stable liquid crystalline phases with a significant melting temperature depression. The in vitro protocol supported the idea that the same phenomena can occur during digestion in which mechanochemical forces were probably the mechanisms promoting cholesterol solid phase changes in the presence of such phytocompounds. In this case, these changes could alter cholesterol solubility and possibly its absorption in the gastrointestinal lumen.

Deep eutectic behavior in binary mixtures of protic ionic liquids

The solid–liquid phase equilibrium of ionic liquids (ILs) is a kind of fundamental data, and the deep eutectic behavior of protic ionic liquids (PILs) is scarcely studied in literature. In this work, four PILs, 1,3-dimethyl-2-imidazolidinone bisulfate ([DMIH][HSO4]), pyridinium bisulfate ([Hpy][HSO4]), 2-methylpyridinium bisulfate ([2-mHpy][HSO4]), and 3-methylpyridinium bisulfate ([3-mHpy][HSO4]), were prepared and six binary mixture systems from these four PILs were used to evaluate the deep eutectic behavior. All six systems were found to have a deep eutectic point in the solid–liquid equilibrium curves, and the largest melting temperature depression is 68.8 K appearing in [DMIH][HSO4]-[Hpy][HSO4]. The eutectic compositions and temperatures were determined, and the solid–liquid equilibrium data of the six binary systems were calculated successfully using the two-suffix Margules equation. The molecular interactions were also investigated using quantum calculations to show the non-ideality in the eutectic systems. Since the deep eutectic behavior is in favor of broadening the liquid window and tuning the physical property of ionic liquids, more binary or ternary eutectic ionic liquids can be prepared as functional materials by just simple mixing. In this sense, the study in this paper helps to elucidate the deep eutectic principle for ILs material design.

On the melting behaviour of linear polyethylene single crystals in mixtures with homogeneous short chain branched polyolefins

The melting temperature depression of linear polyethylene lozenge single crystals is thoroughly examined in mixtures with a series of homogeneous high molecular weight branched polyethylene models, with special emphasis on the effect of short chain branching on the compatibility. The results indicate that the melting temperature of the lamellar single crystals is influenced both by the branching content of the surrounding matrix and by the relative volume concentration of the two polymers in the mixture. The discussion of the results is conducted around the compatibility of polymeric species as a function of the short chain branching content, invoking experimental and computational work performed by other authors. The observed depression indicates that the homogeneous mixing of the two polymers at the melting point may occur whenever the branching content is lower than 6–7 every 100 carbon atoms, a result that is reconciled with computer simulations and other experimental approaches.

Melting Temperature Depression and Phase Transitions of Nitrate-Based Molten Salts in Nanoconfinement.

Hybrids of nitrate-based molten salts (KNO3, NaNO3, and Solar Salt) and anodic aluminum oxide (AAO) with various pore sizes (between 25 and 380 nm) were designed for concentrated solar power (CSP) plants to achieve low melting point (<200 °C) and high thermal conductivity (>1 W m–1 K–1). AAO pore surfaces were passivated with octadecyl phosphonic acid (ODPA), and the results were compared with as-anodized AAO. The change in phase transition temperatures and melting temperatures of salts was investigated as a function of pore diameter. Melting temperatures decreased for all salts inside AAO with different pore sizes while the highest melting temperature decrease (ΔT = 173 ± 2 °C) was observed for KNO3 filled in AAO with a pore diameter of 380 nm. Another nanoconfinement effect was observed in the crystal phases of the salts. The ferroelectric phase of KNO3 (γ-phase) formed at room temperature for KNO3/AAO hybrids with pore size larger than 35 nm. Thermal conductivity values of molten salt (MS)/AAO hybrids were obtained by thermal property analysis (TPS) at room temperature and above melting temperatures of the salts. The highest increase in thermal conductivity was observed as 73% for KNO3/AAO-35 nm. For NaNO3/AAO-380 nm hybrids, the thermal conductivity coefficient was 1.224 ± 0.019 at room temperature. To determine the capacity and efficiency of MS/AAO hybrids during the heat transfer process, the energy storage density per unit volume (J m–3) was calculated. The highest energy storage capacity was calculated as 2390 MJ m–3 for KNO3/AAO with a pore diameter of 400 nm. This value is approximately five times higher than that of bulk salt.

Melting Temperature Depression of Polymer Single Crystals: Application to the Eco-Design of Tie-Layers in Polyolefinic-Based Multilayered Films.

In this paper, we describe a method for determining polymer compatibility, which will aid in establishing the requirements of polyolefinic materials for the eco-design of multilayer films for mechanical recycling while avoiding the use of reactive tie layers. Our ultimate goal is to define the molecular characteristics of the polyolefinic structural layer that improve compatibility with the tie layer during mechanical recycling. We have investigated the melting temperature depression of single crystals of various polyethylenes embedded in commercial polymeric matrices with various functionalities (ester, acrylate, acetate and methacrylic acid sodium ionomer), which can be potentially used as tie layers. We demonstrate how the concentration and molecular architecture of the matrices affect the melting temperature of the embedded single crystals differently depending on the latter’s molecular architecture. The main finding indicates that the tie layers are more compatible with linear polyethylene than with branched polyethylenes. Indeed, our results show that the heterogeneous Ziegler–Natta linear low-density polyethylene is incompatible with all of the tie layers tested. The depression of melting temperatures observed are in excellent agreement with the results obtained by investigating the rheological behaviour and morphological features of solution-mixed blends in which segmental interactions between polymeric chains have been, in theory, maximized. Because Ziegler–Natta linear density polyethylene is one of the most commonly used polymers as a structural layer in multi-layer applications, the findings of this study are useful as they clearly show the unsuitability of this type of polyethylene for recycling from an eco-design standpoint. The specific molecular requirements for polyethylene layers (branching content less than 0.5/100 carbon atoms) can be specified for use in packaging, guiding the eco-design and valorisation of recycled multi-layered films containing this material.

Therapeutic Deep Eutectic Systems towards the Treatment of Tuberculosis and Colorectal Cancer: Opportunities and Challenges

What if a new technology based on therapeutic deep eutectic systems would disrupt the current treatment of major economic and socially burden diseases? The classical definition of eutectic systems is that they are the combination of two or more compounds that interact via hydrogen bonds, from which results a melting temperature depression in comparison with that of its individual components. Therapeutic deep eutectic systems are defined as eutectic systems in which at least one of the individual components is an active pharmaceutical ingredient, or a eutectic system in which the active pharmaceutical ingredient is dissolved. Current literature reports on tuberculosis have been mostly based on the most common anti-tuberculosis drugs prescribed. Using eutectic systems based on naturally occurring molecules known for their anti-microbial activity may also present a promising therapeutic strategy able to cope with the prevalence of Mycobacterium tuberculosis and prevent the appearance of multidrug resistance strains. With regards to colorectal cancer, literature has been unravelling combinations of terpenes with anti-inflammatory drugs that are selectively cytotoxic towards colorectal cancer cells and do not compromise the viability of normal intestinal cells. This technology could contribute to preventing tumor growth and metastasis while providing a patient compliance therapeutics, which will be crucial to the success of overcoming the challenges presented by cancers.

Solid-liquid phase behavior of eutectic solvents containing sugar alcohols

Mixtures of carbohydrates are often reported in the literature as deep eutectic solvents yet, in most cases, their solid–liquid phase diagrams are poorly characterized and no evidence is available to validate this classification. In this work, the phase diagrams of the binary systems composed of the sugar alcohols mannitol or maltitol and meso-erythritol, xylitol, or sorbitol, were experimentally determined. The results obtained reveal that these systems have a thermodynamic ideal behavior, questioning their classification as deep eutectic solvents and showing that intermolecular hydrogen bonding between the components of a mixture is not a sufficient condition to prepare deep eutectic solvents.The phase diagrams of the systems composed of mannitol or maltitol and cholinium chloride were also measured in this work. In sharp contrast to the mixtures composed solely by sugar alcohols, and unlike numerous other choline-based eutectic systems reported in the literature, these systems revealed significant deviations to thermodynamic ideality, leading to significant melting temperature depressions. The Cl-OH interaction between cholinium chloride and the sugar alcohols is identified as the main reason for these deviations to ideality, paving the way for the rational choice of hydrogen bond acceptors to prepare deep eutectic solvents.

Melting Point Depression and Phase Identification of Sugar Alcohols Encapsulated in ZIF Nanopores

Author(s): Dames, C; Urban, JJ; Kang, H | Abstract: Sugar alcohols (SAs) have attractive characteristics as phase-change materials, but their relatively high melting temperature limits their application in the real world. Nanoconfinement can be a useful parameter to reduce the melting temperature to pragmatic ranges. Using molecular dynamics simulations, we investigate the phases and behaviors of encapsulated SA in ZIF-8 and ZIF-11, which cannot be experimentally observed. Based on reliable partial charges for the zeolitic imidazolate framework (ZIF) structures calculated by a density functional theory, structural analysis shows that the SA's attractive interaction with the ZIF structure frustrates the SA crystallization and also elucidates the second-order phase transition between amorphous phases. A methodology is suggested to determine the phase transition temperature of confined materials and used to quantify the melting temperature depression of the ZIF-confined SAs. We also explored the thermal conductivity of SA-in-ZIF composites. Phonon frequency analysis verifies that the presence of SA molecules enhances the heat transfer by adding heat pathways between the nanoporous structure of ZIFs.

Confinement of pyrrolidinium-based ionic liquids [CnMPyrr]+[Tf2N]− with long cationic alkyl side chains (n = 10 and 16) to nanoscale pores: Dielectric and calorimetric studies

Ionic liquids (ILs) with long cationic side chains have shown potential applications in wide fields such as phase-change materials for seasonal energy storage, environmentally friendly herbicides, components of ideal electrode material for supercapacitor devices, and more. In this paper, we investigated the glass transition dynamics, charge transport and structure properties of two pyrrolidinium-based ILs, [CnMPyrr]+[Tf2N]− with n = 10 and 16. Differential scanning calorimetry studies demonstrated the poor glass forming ability (GFA) of the tested materials, especially [C16MPyrr]+[Tf2N]−. Temperature-dependent X-ray diffraction measurements suggested the layered structures in the crystalline and liquid phases of both ILs. Through the dielectric measurements of [C10MPyrr]+[Tf2N]−, we noticed its higher conductivity than the homologues with shorter cationic alkyl chains, in the supercooled liquid state. Additionally, the derivative spectra, εder′′ = (−π/2)[∂ε′/∂ ln (f)], of [C10MPyrr]+[Tf2N]− at temperatures above Tg were examined, and no evidence of the slow sub- α mode associated with the self-aggregation of alkyl chains is detected. Next, we checked how [C10MPyrr]+[Tf2N]− and [C16MPyrr]+[Tf2N]− behaved when geometrically confined in alumina nanopores with various sizes ranging from 10 nm to 120 nm. With respect to the bulk material, confined [C10MPyrr]+[Tf2N]− samples are featured by the drastically enhanced GFA but up to 300-fold decrease in ionic conductivity. In addition, for [C16MPyrr]+[Tf2N]−, vitrification is unfulfilled even when confined into 10 nm nanopore. Nonetheless, nanoscale constraints bring pronounced melting temperature depression and enhanced conductivity to the crystalline confined samples relative to the bulk counterpart. The results of this study contribute to a more comprehensive picture of various confinement effects on ILs and will benefit the rational design of ILs-containing nanodevices.

Characterization and in‐vitro analysis of poly(ε‐caprolactone)‐“Jackfruit” Mucilage blends for tissue engineering applications

AbstractJackfruit mucilage (JM) obtained from the fruit, Artocarpus heterophyllus was melt blended with poly(ε‐caprolactone) (PCL). The physical properties of the blends with more than 60 wt% PCL were investigated. Depression in the equilibrium melting temperature () and the presence of extinction rings in the spherulites of PCL in the blends confirmed miscibility of the two components. The carbonyl and the COC groups of PCL and JM were responsible for the interactions as identified by Fourier transform infrared spectroscopy. The thermal stability of PCL decreased marginally in the blends with increasing JM content. The scanning electron microscopy (SEM) images indicated that no phase separation occurred. Porosity and the mechanical strength of the blends decreased with increasing JM content. Blends exposed to porcine pancreatic lipase showed enzymatic degradation of JM but not PCL and SEM images showed holes in the sample indicative of selective degradation of JM. Cell growth inhibition technique using the L929 fibroblasts cells showed the degree of inhibition was dependent on the increasing JM content in the blends. Blends with low JM content have the potential to be used for increased cell viability while blends with high JM content can be used for the treatment of cancer.

Linking thermophysical and rheological properties to the selection of CO2 foaming conditions of rubbery elastomers using the relative rigidity reduction path

Changes in rigidity and depression of the melting transitions of poly(ethylene-co-vinyl acetate-co-carbon monoxide) in CO2 have been determined with High-Pressure Torsional Braid Analysis (HP-TBA). The results show that the ambient pressure melting temperature was reduced from 56 °C to 40 °C at 73 bar, and to 30 °C at 99 bar CO2 pressure. Foaming experiments were carried out at 30 and 40 °C at different pressure conditions along the rigidity reduction path. Foam densities in the range 0.20 g/cm3 were achievable at foaming temperatures of 30 and 40 °C, respectively. The present study shows that linking the relative rigidity or the melt strength of the polymer and the depressed melting temperature to CO2 exposure pressure allows for rational assessments of the lower saturation pressures that would still permit foaming at a given temperature, and the upper saturation pressures beyond which foaming would not significantly lower the foam density.

Investigation of the Melting Point Depression of Copper Nanoparticles

In this paper copper nanoparticles (Cu NPs) have been produced by solvothermal method. One of the objectives of the present research was to create Cu NPs using aqueous medium technology. The analysis of the produced particles was performed by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). In the course of the experiments, copper core and organic shell nanoparticles were created successfully. It has been found that the average diameter of the created Cu NPs was 50 nm. The thermal behaviour of these particles was investigated by Differential Scanning Calorimetry (DSC). The melting temperature depression of the one-pot synthesized Cu NPs was 633 °C.