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This study explores the impact of different levels of halloysite nanotubes (HNT) and d-isomer on the non-isothermal crystallization behavior of the polylactic acid (PLA). The processing conditions, thermal flow, molecular orientation and the presence of nanofillers can affect the crystallinity and properties of PLA. In this work, PLA-based nanocomposite filaments were produced and their crystallization kinetics was studied. The data obtained through experiments, using differential scanning calorimetry at various cooling rates, were analyzed employing the Jeziorny and Mo models. And the activation energy of crystallization was determined by the Friedman method. The results showed that the growth of PLA crystals is three-dimensional, the HNT can accelerate the crystallization process, and crystallization occurs at higher temperatures in the presence of flow. The activation energy increased with addiction of more HNT in the nanocomposite. The study also found that the d-isomer has a more significant influence on the crystallization of PLA than HNT, which can inhibit crystal formation in some cases. These findings provide insights into the factors that can influence the properties of PLA nanocomposites and how they can be optimized. [ABSTRACT FROM AUTHOR]

We have developed an analytical method to quantitatively analyze differential scanning calorimetry (DSC) experimental data. This method provides accurate determination of thermal properties such as equilibrium melting temperature, latent heat, change of heat capacity which can be performed automatically without intervention of a DSC operator. DSC is one of the best techniques to determine the thermal properties of materials. However, the accuracy of the transition temperature and enthalpy change can be affected by artifacts caused by the instrumentation, sampling, and the DSC analysis methods which are based on graphical constructions. In the present study, an analytical function (DSCN(T)) has been developed based on an assumed Arrhenius crystal size distribution together with instrumental and sample-related peak broadening. The DSCN(T) function was successfully applied to fit the experimental data of a substantial number of calibration and new unknown samples, including samples with an obvious asymmetry of the melting peak, yielding the thermal characteristics such as melting and glass transition temperature, and enthalpy and heat capacity change. It also allows very accurate analysis of binary systems with two distinct but severely overlapping peaks and samples that include a cold crystallization before melting. [ABSTRACT FROM AUTHOR]

In this work, the effect of uniaxial stretching on the crystallization and melting behaviors, miscibility, crystal structure, and mechanical properties of neat poly(L-lactide) (PLLA) and miscible PLLA/poly(vinyl acetate) (PVAc) blends was investigated. Stretching process could generate remarkable influence on thermal properties of neat PLLA and PLLA/PVAc blend. With stretching ratio increasing, macromolecular chains orientation and crystallization were promoted, resulting in a decrease in cold crystallization temperature and an increase in glass transition temperature, and a significant increase in crystallinity. In addition, after stretching process PVAc still inhibited the crystallization of PLLA. PLLA/PVAc blends were completely miscible blend system which had only one glass transition temperature before and after stretching process, and phase separation did not occur after stretching process. When stretch ratio increased, amorphous PVAc had greater influence on the tanδ transition peak and storage modulus increased markedly, which was benefit to the improvement of heat resistance. The α′ crystal form was produced in blends after stretching process. Stretching process with moderate stretch ratio can be utilized to improve the mechanical properties of PLLA with simultaneous enhancement of tensile strength, fracture strain and stiffness. The findings in this work provide an insightful understanding of the effect of stretching process on miscible PLLA blend and the improvement of toughness, which will facilitate the large-scale practical application of PLLA. [ABSTRACT FROM AUTHOR]

The structural and thermal properties of sodium niobium phosphate glass are studied to analyse its suitability for immobilizing long-lived radioactive waste from nuclear reprocessing plants. Two series of sodium niobium phosphate glasses such as (A) xNb2O5–(50−x)Na2O–50P2O5 and (B) xNb2O5–(50−x/2)Na2O–(50−x/2) P2O5 (x = 0, 10, 20, 30, 40 mol.%) are prepared by the conventional melt–quenching technique. The influence of the incremental addition of Nb2O5 on the structural and thermal properties of the above two series is investigated. The FTIR and Raman spectra of these glasses revealed that the number of [NbO6] octahedral chain increases with Nb content and dominates as the major structural unit over the number of PO4 tetrahedra unit. The glass transition temperature (Tg), crystallization temperature (Tc) and melting temperature (Tm) are measured by using a differential scanning calorimeter (DSC). Other thermal stability parameters such as Hruby (KH), Angell (KA), Saad–Poulain (KSP) and Weinberg (KW), the total relaxation time of transformation and fragility are evaluated and compared between different composition of glasses. For both series A and B, the glass transition temperature increases with Nb content, suggesting the formation of a larger number of P–O–Nb or Nb–O–Nb linkages compared to the PO4 tetrahedra, resulting in a more rigid network. This is confirmed by Raman spectra which show an increase in the number of Nb–O–Nb bonds with Nb content. The major crystalline phases formed by devitrifying these glasses are identified by XRD and are found to be mainly NaPO3, NbOPO4, Na2Nb6P4O26 and Na4Nb8P4O32. [ABSTRACT FROM AUTHOR]

In this work, poly(ethylene glycol) (PEG)/boron nitride nanosheets (BNNS) masterbatch was prepared by freeze-drying their ultrasonically homogenized aqueous suspension, followed by melt-mixing with poly(lactic acid) (PLA) to fabricate the nanocomposites. The effect of PEG and BNNS on the crystallization behavior of PLA was investigated. The dynamic mechanical properties, thermal conductivity and thermal stability of the nanocomposites were also evaluated. It was found that, under quiescent conditions, PEG and BNNS had a synergistic effect on accelerating the nonisothermal crystallization of PLA. Unexpectedly, under injection molding conditions, the combination of PEG and BNNS had a negative effect on PLA crystallization. This can be ascribed to the plasticizing effect of PEG, which relaxes the orientation of PLA chains and retards flow-induced crystallization. Dynamic mechanical analysis (DMA) showed that the presence of BNNS enhanced the heat resistance of PLA only when PLA was crystallized, while further incorporation of PEG had a negative effect. Nevertheless, simultaneous use of PEG and BNNS had a synergistic effect on enhancing the thermal conductivity of PLA. [ABSTRACT FROM AUTHOR]

Metal ions, as common impurities in the crystallization process of explosives, have a significant influence on the crystal quality and performance. The effects of Fe3+, Zn2+, Ca2+ and Na+ ions on the crystallization and thermal properties of octogen (HMX) were studied. And the defect distribution as well as formation process of the explosive crystals doped with the metal ions were analysed. ICP, XPS and an etching method were utilized to characterize the contents and distributions of residual metal ions in the HMX crystals. The effects of the metal ions on the thermal decomposition and phase transition of HMX were obtained based on DSC-TG and in situ XRD. The mechanism of the influence of the metal ions on the crystallization of HMX was also explored. The results showed that the metal ions would change the nucleation growth mode of HMX to form dispersed crystalline HMX. The residual metal ions were mainly adsorbed on the crystal surface and included in the crystal. The metal ions had a significant influence on the thermal properties of HMX, with Ca2+ and Fe3+ inhibiting the thermally induced phase transition of HMX, Na+ promoting the phase transition of HMX, and the effect of Zn2+ on the phase transition of HMX depending on its concentration. The growth mechanism of doped HMX was lamellar stacking, and the metal ions changed the quality of the crystal by hindering the growth step of the HMX crystal. Since the crystal quality is highly related to the thermal performance, the safety of the explosive is affected. [ABSTRACT FROM AUTHOR]

Bioplastics reinforced by agricultural waste fibres show promise to provide degradation back into the environment when they are no longer needed. These biocomposites have the potential to replace synthetic polymers from non-renewable resources in some applications and may turn out to be one of the material revolutions of this century. Unlike synthetic composites, biocomposites are renewable, carbon neutral, biodegradable and non-petroleum based and have low environmental, human health and safety risks. In this paper, poly(lactic acid) (PLA)-based biocomposites filled with technical cellulose fibres (CeF) and rice husks (RHs) at 10–30 mass% loading were prepared by twin-screw extrusion and injection moulding to enhance stiffness of resulting biocomposites. Particular attention was given to the enhancement of adhesion between the polymer matrix and natural filler through the physical modification by ozone (O3) and dielectric barrier discharge (DBD) plasma (p) surface treatments. Further than, compatibilizing agent based on PLA-g-MAH was produced and introduced into the PLA systems. The non-isothermal crystallization behaviour and thermal properties were investigated through differential scanning calorimetry (DSC) under various cooling rates (5, 10, 20 and 40 °C min−1). The addition of both fillers increased overall crystallization kinetics of resulted biocomposites, especially at high cooling rates. An increase in crystallinity degree from 2.4 (neat PLA) up to 51% has been observed for PLA/30CeFO3 samples at 40 °C min−1 cooling rate. An increase in crystallinity degree based on mass percentage of filler was noticed especially for PLA/RH. Mass percentage increase in CeF did not notice significant increase in PLA crystallinity. The influence of RH and CeF on transformation behaviours of PLA αʹ-/α-polymorphs was observed. The elimination of imperfect αʹ-crystals was observed with increasing amount of RH and CeF. [ABSTRACT FROM AUTHOR]

The polymorphism of tolbutamide and chlorpropamide under melting/crystallization was investigated with using DSC and in situ X-ray powder diffraction. The asymmetry in thermal transformations was revealed for both substances. Under heating, all tolbutamide/chlorpropamide polymorphs transform into high-temperature IH/ε polymorph, which melts at 128 °C. The crystal structures of the high-temperature polymorphs, IH and ε, are very similar to each other in the unit cell parameters and in the arrangement of z-shaped infinite hydrogen-bonded ribbons. Under cooling, other polymorph crystallizes from the melt, V for tolbutamide and β for chlorpropamide, thus making easy the obtaining of these metastable polymorphs. The polymorphs of tolbutamide and chlorpropamide crystallized from their melts turned out to be also very similar to each other in their structures (space group, unit cell parameters, arrangement of π-shaped infinite hydrogen-bonded ribbons). Solid–solid transformation V ⇒ II in tolbutamide was detected both in samples stored under room conditions and those melted in capillaries, thus providing new easy way for II tolbutamide crystallization. In generalizing our results, one can expect that if evident similarity is found among the polymorphs of similar molecules in their crystal structure, the similarity in their thermal properties can be also found, and vice versa. [ABSTRACT FROM AUTHOR]

The influence of composition and neodymium doping on the crystallization kinetic of calcium aluminosilicate glasses, melted under vacuum atmosphere, was investigated. Glass stability was evaluated by means of thermal events. Non-isothermal methods of Kissinger and Ozawa were used to obtain the apparent activation energy and to predict the crystallization mechanism. The isothermal method of Ray and Day was applied in order to obtain the nucleation rate type curve and the maximum nucleation temperature. In the studied glass system, surface crystallization was more favorable than bulk. By confocal Raman microscopy, it was estimated that the crystallized region was 20–30 μ m from surface to center of sample. This observation was further validated by structural investigation with X-ray diffraction, which showed the formation of Ca 9 Al 6 O 18 and Ca 3 Al 2 O 6 phase as a surface layer in the samples. [ABSTRACT FROM AUTHOR]

The influence of cerium oxide on the thermal properties and the glass structure has been studied for the Li2O–(Na2O–K2O)–B2O3–SiO2 system. It has been established that cerium is completely soluble in the quenched glass during the synthesis if addition of CeO2 is 0–10 mol%. The cubic ceria phase is formed in glass either during the synthesis if addition of CeO2 is 20 mol% or after thermal treatment (annealing) if the glass contains 10–20 mol% of CeO2. The studied lithium borosilicate glasses have low thermal stability and demonstrate significant difference in the crystal phase formation for Ce-free and Ce-containing glasses after annealing. The lithium–sodium and lithium–potassium glasses have much higher thermal stability toward crystallization regardless of Ce content. The obtained results are relevant for improving the properties of matrix materials of similar borosilicate systems used for immobilization of radioactive waste. [ABSTRACT FROM AUTHOR]

Barium phosphate glasses of the composition (100 − x)Ba(PO3)2–xWO3 with 0–60 mol% WO3 were prepared and studied. Thermal studies of the glasses were carried out with DTA, dilatometry and hot-stage microscopy. Glass transition temperature in this glass series increases with increasing WO3 content from 461 °C (x = 0) to 623 °C (x = 60). Most glasses containing WO3 crystallize on heating within the range of 650–750 °C with the exception of glasses with 20–30 mol% WO3, which are thermally stable. Very high chemical durability of these glasses with dissolution rate of 1.4 × 10−8–6.2 × 10−9 g cm−2 min−1 was also revealed. Crystallization of glasses revealed the existence of a new compound Ba(WO2)2(PO4)2 in the studied compositional series. The compound Ba(WO2)2(PO4)2 possess hexagonal unit cell of dimensions a = 11.5191(1) Å and c = 6.3437(1) Å, and its melting point is 936 °C. Raman spectra of crystallized glasses confirmed the formation of crystalline compound in this glass series and revealed the presence of glass phase in some thermal-treated samples. 31P MAS NMR showed on only one coordination of phosphorus atoms in the Ba(WO2)2(PO4)2 compound. [ABSTRACT FROM AUTHOR]

Casting films of polypropylene (PP), poly(lactic acid) (PLA) and ethylene vinyl alcohol copolymer (EVOH) ternary blends having different compositions were prepared. The thermal properties in correlation to the oxygen permeability and mechanical properties of the films were investigated. The morphology of the blends, before and after the film extrusion process was investigated. The SEM images of casted films show a great laminar morphology development in the machine direction. The effects of EVOH and compatibilizer on the relative changes in the crystallization behavior, i.e., melting peak crystallization (Xm%) and degree of crystallization (Xc) are considered. While the compatibilization facilitated the crystallization of PP, it had reverse effect on EVOH crystallization. There is an increase in the Xm% as well as Xc% of EVOH in ternary blend with an increase in EVOH content. The permeability to oxygen was decreased with an increase in EVOH content and compatibilization led to improvement in barrier properties. The crystallinity degree of EVOH revealed to have a greater effect on barrier and mechanical properties as compared to that of PP. Finally, the study of the interaction parameters using Nishi and Wang theory confirmed an effective interaction between the components. [ABSTRACT FROM AUTHOR]

Differential scanning calorimetry (DSC), dilatometry and X-ray diffraction have been used to study thermal behavior and stability of glasses prepared simultaneously in Al2O3 or Pt crucibles in compositional series (40 − x)MgO-xFe2O3-60P2O5 within the concentration range of x = 0-40 mol% Fe2O3. Mössbauer spectra showed that all glasses with Fe2O3 contained both Fe(II) and Fe(III) ions. The contamination glasses from alumina crucibles ranged from 0.3 to 0.9 mol% Al2O3. The replacement of MgO by Fe2O3 resulted in a gradual decrease in glass transition temperature and dilatometric softening temperature, whereas thermal expansion coefficient did not change significantly. The DSC curves showed that all glasses crystallize on heating in the broad temperature range ≈ 560-900 °C. Crystallization temperature decreases with increasing Fe2O3 content. The highest tendency toward crystallization was found for the glass containing 40 mol% Fe2O3. X-ray diffraction measurements showed that the major compounds formed by glass crystallization were Mg(PO3)2, Fe(PO3)3, Fe3(P2O7)2 and FePO4. All thermoanalytical studies showed differences in thermal behavior of glasses prepared in Al2O3 or Pt crucibles. [ABSTRACT FROM AUTHOR]

In the study, MDSC method was used to evaluate thermal properties of β-lactoglobulin-retinyl palmitate products enriched in disaccharides. Additionally, sorption behavior of powders was determined to define their stability. The obtained powders were also examined and visualized with scanning electron microscopy to find the relationship between food processing conditions and morphological changes in products. For the samples tested, a single glass transition was observed. The results have shown the impact of the composition of studied samples on the glass transition temperatures. The carbohydrate- β-lactoglobulin systems were characterized by higher T values than disaccharides alone. At low water activity, all powdered complexes showed typical sorption behavior of food systems with the sigmoidal shape of the curve. The present study has shown that spray-dried and freeze-dried powdered products with lactose or trehalose have different time-dependent crystallization behavior. Trehalose as a carbohydrate component of samples, in comparison with lactose, delayed the occurrence of crystallization. The obtained images presented the dependence of the shape of the particles on the drying method used. Spray-dried powders were characterized by a spherical or close to spherical structure with the surface of larger particles often deformed. In the case of freeze-dried particles, irregular structures were observed. [ABSTRACT FROM AUTHOR]

The hexahydrate of europium nitrate hexahydrate Eu(NO)·6HO shows no phase transitions in the range of −40 to 76 °C when it melts in its own water of crystallization. It was shown that the thermal decomposition is a complex step-wise process, which starts with the simultaneous condensation of 6 mol of the initial monomer Eu(NO)·6HO into a cyclic cluster 6[Eu(NO)·6HO]. This hexamer gradually loses water and nitric acid, and a series of intermediate amorphous oxynitrates is formed. The removal of HNO azeotrope is essentially a continuous process occurring in the liquid phase. At higher temperatures, oxynitrates undergo further degradation, lose water, nitrogen dioxide, and oxygen, and finally, after having lost lattice water, are transformed into europium oxide. All mass losses are satisfactorily accounted for under the proposed scheme of thermal decomposition. [ABSTRACT FROM AUTHOR]

A glass with the composition of the SiO-NaO-CaO-PO was synthesized by sol-gel method at temperature of 900 °C, and then yttrium-, silver- and cerium-containing glasses were prepared at the same conditions using this base system. The structural and thermal properties of the glass samples were investigated by X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy, energy-dispersive X-ray (EDX) spectroscopy and differential thermal analysis techniques. The Ca(PO)(SiO) phase having the orthorhombic crystal system is detected for each sample without any secondary phase, and this phase is confirmed by the FTIR spectra. With the addition of Y, Ag and Ce to the SiO-NaO-CaO-PO system, the variations in the average crystallite size, crystallinity percent, lattice parameters and unit cell volume are observed. A decrease in the crystallization peak temperature and the changes in the glass transition temperature are seen with the addition of Y, Ag and Ce to the base system. The addition of Y, Ag and Ce to the base glass increases significantly its density. The EDX spectra of the as-prepared samples verify the introduction of the as-mentioned elements. [ABSTRACT FROM AUTHOR]

In this paper, a ribbon of binary Ni-Nb amorphous alloy was prepared by the melt spinning technique. Glass transition and crystallization phenomenon of the alloy were investigated by differential scanning calorimetry. Thermal properties of the ribbon of binary Ni-Nb upon heating and cooling were analysed by DTA at a heating/cooling rate of 0.5 K s under the purified argon atmosphere. The thermal stability of Ni-Nb amorphous alloy was studied by using an X-ray diffractometer equipped with an in situ heating system. The structure and fracture morphology of the ribbons were examined by X-ray diffraction and scanning electron microscopy methods. [ABSTRACT FROM AUTHOR]

Borophosphate glasses of the BaO-BO-PO ternary system were prepared and studied within the large glass-forming region of the system. Fourteen investigated glass samples of barium borophosphate glasses were discussed for a comparison of the compositional trends in their properties in four compositional series such as A: (100 − x)Ba(PO)- xBO, B: 40BaO- yBO-(60 − y)PO, C: (50 − z)BaO- zBO-50PO, and D: (60 − w)BaO- wBO-40PO. Changes in glass density and molar volume primarily depend on the BaO content in the glasses. The thermal properties were studied with a differential thermal analysis, hot-stage microscopy, and dilatometry. Glass transition temperature increases with a rising BO content most rapidly in the glass series A and B. It reaches its maximum in these series for the glasses containing 20-30 mol%, where the glass network represents a 3D structure interlinked with P-O-B, P-O-P, and B-O-B bridges. The thermal expansion coefficient decreases, in contrast, with the increasing BO content in these ternary glasses as well as their chemical durability. The crystallization of these glasses, in the samples with a low BO content, results in the formation of barium metaphosphate BaPO. Certain crystallized samples also contain a small amount of BPO, and diffraction lines of ternary compounds BaBPO and BaB(PO) were revealed in a number of samples. A new compound of the composition BaBPO was identified in the crystallized glass 50BaO-10BO-40PO. [ABSTRACT FROM AUTHOR]

The higher mechanical properties of polypropylene (PP) fibers based on metallocene-catalyzed PP (miPP) in comparison with fibers based on Ziegler-Natta-catalyzed PP (zniPP) were presented in periodic literature in the last decade. At the same time the miPP fibers have lower crystallinity and lower melting temperature compared with conventional zniPP fibers. In our experimental work, the thermal and mechanical properties of both the miPP and zniPP multifilaments depending on their spinning and drawing conditions were investigated. The dynamic viscosity and deviation from the Newtonian flow of polymer melt were evaluated as important parameters for melt-spinning technology. The melting temperature, melting enthalpy and melting entropy of multifilaments were investigated using DSC analysis in dependence on spinning temperature and draw ratio of fibers. At the same time the mechanical properties of fibers tenacity, elongation and elastic modulus were measured. The DSC measurements were carried out using conventional method and constant length method at which the constant length of fibers was held (constrained fibers). The changes in melting temperature, melting enthalpy and melting entropy of drawn fibers were analyzed and correlated with mechanical properties of fibers. The mechanical and thermal properties of fibers were discussed with regard to the spinning and drawing conditions as well. [ABSTRACT FROM AUTHOR]

This study deals with the effects of Ru-Bi partial substitutions on the thermal, structural and mechanical properties of BiRuPbSrCaCuO ( x = 0.0, 0.025, 0.050, 0.075) system, produced by using glass ceramics method. The effects of Ru-Bi partial substitutions on glass transition, nucleation and crystallization temperature were analyzed via differential thermal analyzer (DTA). Besides, microstructure and micromechanical properties of Ru-Bi partially substituted BSCCO glass ceramics were also investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Vickers microhardness measurements. From the DTA results, nucleation kinetics were studied by using Ozawa, Augis-Bennett, Takhor and Kissinger equations. In addition to this, activation energies and Avrami parameters were also calculated. According to the results of the thermogravimetric analyses, the amount of oxidation was seen to be increased with increasing Ru concentration. Moreover, the lattice parameters, volume fractions and surface morphologies of our newly produced glass ceramics were investigated by XRD and SEM measurements, respectively. RISE behavior obtained from the microhardness measurements for all samples. Microhardness, elastic modulus, yield strength and fracture toughness values decreased with increasing Ru doping. [ABSTRACT FROM AUTHOR]

Biodegradable poly(butylene succinate) (PBS)/basalt fiber (BF) composites were prepared by melt blending method using twin-screw extruder followed by injection molding. Mechanical properties, crystallization and melting behavior, morphology, crystal structure and thermal stability of PBS/BF composites with various BF contents were investigated by different techniques. The tensile and impact properties of the composites were improved markedly with the addition of BF, due to the efficient interfacial adhesion between fibers and PBS matrix. Crystallization and melting behavior of PBS in its composites kept almost unchanged, indicating that the nucleation effect of BF was minimal and, meanwhile, it played a role in hindrance of chain motion. TG analysis showed that the thermal stability of PBS/BF composites was enhanced by the addition of BF. The crystal structure of PBS was not affected by the incorporation of BF, while the nucleation density increased gradually and the spherulite size reduced remarkably with the increase in BF. No transcrystallization phenomenon on the surface of BF was observed maybe as a result of without surface treatment. [ABSTRACT FROM AUTHOR]

Various compositions of polypropylene (PP) and poly(lactic acid) (PLA) blends were prepared by one-step melt compounding in a twin-screw extruder. Two compositions were selected for investigation of effect of clay and n-butyl acrylate glycidyl methacrylate ethylene terpolymer (PTW) as compatibilizer on thermal properties and non-isothermal crystallization behavior of PP/PLA/clay nanocomposite systems, i.e., PP-rich one (75/25 composition) containing Cloisite 15A and PLA-rich one (25/75 composition) containing Cloisite 30B. The thermal behavior of the systems was investigated by means of differential scanning calorimetry (DSC) and correlated with their microstructures. The narrowing down of the peaks in the wide-angle X-ray scattering pattern of PP-rich blend was associated with an increase in size and/or perfection of the crystals. On the other hand, the broadening of the peaks in PLA-rich blend implied a decrease in the size of the crystals. The calculated interlayer distance, using Scherrer equation, in Cloisite 15A was slightly greater than that of Cloisite 30B. Moreover, an increase of 100 % in interlayer distance showed a greater level of intercalation in PP-rich system as compared to the PLA-rich system. Blending of PP and PLA led to significant changes in the crystallinity behavior of the blends compared to the neat components. Moreover, the incorporation of the both clays into the two systems led to a greater change in the crystallinity degree, comparing to that of unfilled blends. [ABSTRACT FROM AUTHOR]

Vitrification is the most effective method of hazardous waste immobilization. Toxic elements are incorporated into a glass structure. Iron alumino-phosphate glasses are presently being considered as a matrix for storage of a radioactive waste which cannot be vitrified using conventional borosilicate waste glasses. Influence of NaSO as a one of components such the waste on thermal properties and crystallization ability of 60PO-20FeO-20AlO glass was studied. It was observed that NaSO decreases transformation temperature and increases Δ C. The glass characteristic temperatures, glass crystallization ability and crystallizing phases were determined. NaSO increases the glass crystallization ability which could be related with Δ C heat capacity accompanying glass transition changes. The glass internal structure rebuilding accompanying the sodium content increase is considered. The obtained results were compared with structural model previously developed for 60PO-40FeO glass and showed the structural similarity between these glasses. [ABSTRACT FROM AUTHOR]

The thermal behavior of gallium microparticles, in comparison with bulk gallium, was examined by differential scanning calorimetry. All the samples showed a single endothermic signal for melting near the known melting point of gallium. Cooling the molten samples showed super-cooling effect, which was more pronounced for the gallium microparticles than for the bulk metal. [ABSTRACT FROM AUTHOR]

The crystallization behavior of the 70GeS-20InS-10CsI glass introduced with 2 mol% AgS system has been studied under non-isothermal condition. The beginning of transmission is shifted toward longer wavelength as a function of annealing temperature. Thermal properties were measured by the differential scanning calorimeter. From the heating rate dependence of crystallization temperature, the activation energy ( E) for crystallization and the crystallization rate constant ( K) were calculated. The K value of 2.44 × 10 for the InS phase is about 28 times larger than the second CP, this is why the controllable crystallization to transparent chalcogenide glass-ceramics with sole InS crystallites can be achieved. By heat treatment with various temperatures, the hardness of the glass enhanced from 204 to 230.8 kg mm, while retained the transmittance of the 8-11 μm. [ABSTRACT FROM AUTHOR]

Vitrification is the most effective method of the hazardous waste immobilization. Toxic elements are incorporated into glass structure. Iron phosphate glasses are presently being considered as a matrix for storage of the radioactive waste which cannot be vitrified using a conventional borosilicate glass. Influence of NaSO as one of the components such the waste on thermal properties and crystallization ability of iron phosphate waste glass was studied. It was observed that NaSO decreases transformation temperature and increases Δ C. The glass characteristic temperatures, glass crystallization ability, and crystallizing phases were determined. NaSO increases the glass crystallization ability which could be related with Δ C heat capacity accompanying glass transition changes. The glass internal structure rebuilding, accompanying the sodium content increase, is considered. It is shown that Δ C is a suitable, structure-sensitive glass crystallization ability, parameter. [ABSTRACT FROM AUTHOR]

Thermal behavior of waxy oils is investigated using the techniques of thermogravimetric (TG) analysis and differential scanning calorimetry (DSC). Model waxy oils and real waxy crude oils are utilized. Decomposition temperatures of waxy oils are obtained using TG analysis. The effects of thermal history, wax content, and additive on the gelation process of waxy oils are investigated using DSC. The DSC method provides a measure of wax solubility as well as solid fraction. An integration method and a computation method are utilized to predict solid fraction. In addition, wax crystallization onset points are obtained at the cooling rates ranging from 1 to 20 °C min. Similarly, wax dissolution endset points are obtained at heating rates ranging from 1 to 20 °C min. Extrapolated onset and endset points yield wax precipitation temperature and wax dissolution temperature, respectively. Subsequently, wax solubility curves are obtained using thermodynamic computations. A wax precipitation temperature method and a wax dissolution temperature method combine thermodynamic phase behavior with onset/endset points to predict solid fraction. Both the wax precipitation temperature method and the wax dissolution temperature method can predict solid fraction of waxy oil samples. The wax precipitation temperature method and the wax dissolution temperature method are accurate when the temperature is close to the wax appearance temperature. A heat-integration method provides accurate values of the solid fraction at temperatures significantly below the wax appearance temperature. Therefore, integration method and wax precipitation temperature/wax dissolution temperature method are combined to predict solid fraction. The effect of solid fraction on yield stress is also investigated using differential scanning calorimetry and rheometry. Finally, a new solid fraction dependent gel strength model is obtained for shut in and restart of waxy crude oil pipelines. [ABSTRACT FROM AUTHOR]

Thermal properties and structure of bulk glasses of (AsS)(SbS) system ( x varies from 0 to 60 mol%) were studied by differential scanning calorimetry and Raman spectroscopy. It was found that with increasing Sb content the glasses can be sorted out to the three groups. The structure of glasses with x ≤ 10 is build-up mainly from AsS pyramidal units and the well-known crystallization resistance of AsS can explain the reluctance of these undercooled liquids against crystallization. In glasses with a higher content of antimony, i.e., 10 < x ≤ 30 mol%, the vibration characteristics of AsS clusters appear. Undercooled melts of these glasses crystallize forming both β-AsS and high-temperature phases of SbS. Structure of glasses with the highest antimony content ( x > 30 mol%) is based on SbS structural units significantly lowering stability of their undercooled melts from which only SbS crystallizes. [ABSTRACT FROM AUTHOR]

In this work, we studied the kinetics of mullite formation in different composites under non-isothermal conditions using DTA. Different composites based of mullite, alumina, zircon and zirconia were prepared by reaction sintering of boehmite (as alumina source) and zircon. Several mixtures were used while varying the percentage of the boehmite from 30 to 70 mass% with a step of 10. Five compositions marked as B30, B40, B50, B60 and B70 corresponding to boehmite-zircon ratios (mass%) of 30/70, 40/60, 50/50, 60/40 and 70/30 were fabricated and studied. The DTA conducted at heating rates of 10, 20 and 30 K min showed an endothermic peak in all composites at about 1,603 K associated with mullite formation. The activation energies measured from non-isothermal treatments for five compositions (30, 40, 50, 60 and 70 mass% of boehmite) were 1,029, 1,085, 1,262, 1,508 and 1,321 kJ mol, respectively. The n values (Avrami parameter) for all compositions are larger than 2.5, the mullite crystallization of these composites is followed by three-dimensional growth. [ABSTRACT FROM AUTHOR]

In this paper, studies of the temperature dependence for spherulitic growth of PBST copolyester bearing 70 mol% butylene terephthalate units (named as PBST-70) ranged from 70 to 170 °C were first reported based on the Lauritzen-Hoffman secondary nucleation theory. The results showed that maximum spherulitic growth rate of PBST-70 was obtained under crystallization temperature of 90 °C, and more perfect spherulites were formed via increasing isothermal crystallization temperature by POM measurement. The classical regime I → II and regime II → III transitions occurred at the temperatures of 150 and 110 °C, respectively, using the empirical universal values of U* = 6300 J mol and T = T− 30 K. Moreover, the effects of isothermal crystallization temperature on crystal lamellar thickness, thermal and tensile properties of PBST-70 were systematically investigated by small angle X-ray scattering, differential scanning calorimeter, and strength tester. The results indicated that the crystal lamellar thickness increased by increasing isothermal crystallization temperature. The endothermic peak shifted to higher temperature and the tensile properties of PBST-70 were enhanced under higher isothermal crystallization temperature. [ABSTRACT FROM AUTHOR]

Kinetic analysis of the crystallization process in Bi(AsS) and Bi(AsS) glasses was performed based on DSC curves recorded under non-isothermal measurement conditions. Samples were thermally treated at different heating rates in the temperature range 300-770 K. The activation energy of crystallization E and the pre-exponential factor K are determined by the Kissinger method and the characteristic crystallization parameters m and n of investigated glasses by the Matusita method. For both crystallization processes the glass with 4 at.% of Bi is characterized by the mechanism of volume nucleation, which is manifested in the form of two-dimensional growth at the first crystallization process, and as three-dimensional at the second one. On the other hand, in the sample with 6 at.% Bi, the average value of the parameter m is close to one, which indicates one-dimensional crystal growth. Compatibility of the values of the parameters m and n suggests that this sample has a large number of crystallization centers, which do not increase significantly during the thermal treatment. [ABSTRACT FROM AUTHOR]

Novel double complex salts [M(NH)Br][AuBr]· nHO, M = Rh, Ir, have been synthesized and examined. The processes of thermal decomposition of the compounds in inert and reductive atmospheres have been studied and intermediate products identified. Simultaneous thermal analysis with parallel mass-spectrometric analysis of evolved gases (STA-EGA) has been employed for identification of main gaseous products of thermolysis in inert atmosphere. It has been revealed that the final products of decomposition in inert or reductive atmospheres are fine powders of gold and the corresponding platinum metal with sizes of crystallites 4-40 nm. The possibility of preparation of the metastable solid solution AuIr on thermolysis of [Ir(NH)Br][AuBr]·HO in inert atmosphere has been demonstrated. [ABSTRACT FROM AUTHOR]

The effect of TeO additions on the thermal behaviour of zinc borophosphate glasses were studied in the compositional series (100 − x)[0.5ZnO-0.1BO-0.4PO]- xTeO by differential scanning calorimetry, thermodilatometry and heating microscopy thermal analysis. The addition of TeO to the starting borophosphate glass resulted in a linear increase of glass transition temperature and dilatometric softening temperature, whereas the thermal expansion coefficient decreased. Most of glasses crystallize under heating within the temperature range of 440-640 °C. The crystallization temperature steeply decreases with increasing TeO content. The lowest tendency towards crystallization was observed for the glasses containing 50 and 60 mol% TeO. X-ray diffraction analysis showed that major compounds formed by annealing of the glasses were ZnPO, BPO and α-TeO. Annealing of the powdered 50ZnO-10BO-40PO glass leads at first to the formation of an unknown crystalline phase, which is gradually transformed to ZnPO and BPO during subsequent heating. [ABSTRACT FROM AUTHOR]

Calorimetric study of SeTeSn ( x = 0, 2, 4 and 6) glassy alloys have been performed using Differential Scanning Calorimetry (DSC) under non-isothermal conditions at four different heating rates (5, 10, 15 and 20 °C/min). The glass transition temperature and peak crystallization temperature are found to increase with increasing heating rate. It is remarkable to note that a second glass transition region is associated with second crystallization peak for Sn additive Se-Te investigated samples. Three approaches have been employed to study the glass transition region. The kinetic analysis for the first crystallization peak has been taken by three different methods. The glass transition activation energy, the activation energy of crystallization, and Avrami exponent ( n) are found to be composition dependent. The crystallization ability is found to increase with increasing Sn content. From the experimental data, the temperature difference ( T − T) is found to be maximum for SeTeSn alloy, which indicates that this alloy is thermally more stable in the composition range under investigation. [ABSTRACT FROM AUTHOR]

The processing of polyimide films from polyamidic acid solutions involves the simultaeous loss of solvent and chemical conversion, and may imply structural reorganization such as orientation or crystallization. The effect of thermal treatment on the thermal, mechanical and dielectric properties of polymer films based on benzophenonetetracarboxylic dianhydride and 4,4'-diamino-3,3'-dimethyl diphenylmethane have been investigated. The thermal treatment of polyamidic acid at different temperatures led to compounds with different degree of imidization; it turned out that the imidization process took place with high speed until 240 °C and then remained constant. The dynamic mechanical analysis (DMA), contact angles, and dielectric measurements revealed that the storage modulus and contact angles increased with increasing of curing temperature while the dielectric constant decreased. [ABSTRACT FROM AUTHOR]

The results of thermal analysis of speciality elastomers CSM with different chlorine and sulphur contents is presented in the article. The thermal curves obtained under the atmosphere of inert gas have been interpreted from the point of view of phase transitions and chemical reactions of the examined polymers during their heating. It has been stated that from among the investigated chlorosulphonated polyethylenes, only CSM24, which has the lowest chlorine content, contains a crystalline phase, clearly influences on its T temperature. Results of the thermal analysis obtained under inert gas atmosphere have been compared with results obtained under termooxidative atmosphere. Irrespective of the research atmosphere, the thermal decomposition of investigated CSM takes place in three stages. The maximum rate of thermal destruction of modified by heating elastomers, d m/d t, decreases with the increase in chlorine content in the sample having been heated. [ABSTRACT FROM AUTHOR]

Thermal behaviour and structure of glasses from the SiO–PO–KO–MgO–CaO system modified by FeO addition were studied by DSC, XRD and FTIR methods. It has been found that the replacement of MgO and CaO modifiers by FeO in the structural network of silicate–phosphate glass results in decrease of the glass transition temperature ( T) and heat capacity change (Δ C) accompanying the glass transformation. Simultaneously, the ability for crystallization, its course and the type of the forming phases depend on the relative proportions between iron and phosphorus as components forming the silicate–phosphate structure. The type of the crystal phases forming in the course of heating the considered glass has been found to be in agreement with the character of the domains occurring in this glass, confirmed by FTIR examinations. [ABSTRACT FROM AUTHOR]

Glasses of the SiO2–P2O5–K2O–MgO–CaO–B2O3 system acting as nutrients carriers in the soil environment were synthesised by the melt-quenching technique. Thermal properties were studied using DTA/DSC methods and the influence of B2O3 and P2O5 content on thermal stability and crystallization process of these glasses was examined. The structure of the glass network was characterized by FTIR, 31P, and 11B MAS NMR. The chemical activity of the glasses in the 2 mass% citric acid solution was measured by the ICP-AES method. The analysis indicated that the formation of P–O–B units with chemically stable tetrahedral borate groups decreases the glass solubility in conditions simulating the soil environment. [ABSTRACT FROM AUTHOR]

A hydrated form of theophylline-7-acetic acid obtained by recrystallization from water is described and characterized in terms of thermal properties, physical stability with respect to relative humidity and dehydration kinetics. The hydrate resulted to be stable at ambient conditions. Fitting of experimental dehydration data to solid state reaction equations suggests a three dimensional phase boundary reaction proceeding from the surface of the crystal inward along three dimensions. The relevant activation energy calculated from the Arrhenius plot is 173 kJ/mol. [ABSTRACT FROM AUTHOR]

The copolyamides consisting of ε-caprolactam and 6.1–24.5 wt.% of nylon salt prepared from adipic acid and 1-(2-aminoethyl) piperazine were synthesized. Physical and thermal characteristics of polyamide 6 and the copolyamides were compared. Nylon salt does not influence the polyreaction equilibrium so it is possible to prepare the copolyamides with high molecular weight and with the content of low-molecular compounds comparable with that of pure PA 6. Melting temperatures of the copolyamides are lower in comparison with PA 6 and decrease proportionally to the amount of the nylon salt. The thermal stability of the copolyamides is good and equal to that of PA 6. The melting enthalpies indicate that the process of crystallization of the copolyamides is influenced by the time of crystallization and the amount of comonomer present. Longer time of the crystallization assures higher degree of crystallization. The kinetics and the level of crystallization are positively influenced by the mobility of copolyamide segments mainly up to 10 wt.% of comonomer. [ABSTRACT FROM AUTHOR]

The paper presents results of thermal properties measurements of cis-1,4-polybutadienes with different contents of cis-1,4 mers before and after their conventional cross-linking with the use of dicumyl peroxide and non-conventional cross-linking by means of iodoform. The measurements were carried out under the atmosphere of neutral gas using a micro-calorimeter, DSC and thermogravimetry, TG. The thermal curves have been interpreted from the point of view of phase transitions and chemical reactions of investigated elastomers. [ABSTRACT FROM AUTHOR]

Thermal properties such as melting and crystallization are important aspects in understanding the morphology and its contribution to the physical properties of semicrystalline polymers, such as polypropylene. The inclusion of fillers, which are small particles dispersed in the continuous polymer phase, often complicates the predictability of these properties by acting as nucleating agents or defect origins. This paper discusses the creation and use of empirical models based on experimental data for predicting and optimizing the thermal properties of agricultural filler-polypropylene (AgFiller-PP) composites, including peak melting temperature ( Tm), peak crystallization temperature ( Tc) and percent of crystallinity ( Xc). Experiments were performed using differential scanning calorimetry (DSC) to gather data necessary for building appropriate prediction models. Finally, additional experiments were carried out to test the prediction results generated by the models. [ABSTRACT FROM AUTHOR]

A thermal analysis of a series of polylactides (PLA) was carried out based on the number of average molecular mass ( Mn), and the nature of isomer ( D, L and DL). It is confirmed that the glass transition temperature ( Tg) of PLA increased as a function of molecular mass irrespective of isomer type except sample with a high polydispersity index. The melting temperature ( Tm) and enthalpy of crystal fusion (Δ Hf) of L-isomer increased as the Mn was increased from 1100 to 27500. The degree of crystallinity (χc%) increased as a function of molecular mass. However no crystallization peak was detected in the lower molecular mass range (550–1400). The non-isothermal crystallization behavior of the PLA melt was significantly influenced by the cooling rate. Both D and L isomers exhibited insignificant difference in thermal properties and DL lactides exhibited amorphous behavior at identical molecular masses. Change in microstructure showed significant difference between two isomers. Analysis of the FTIR spectra of these PLA samples in the range of 1200–1230 cm−1 supported DSC observation on crystallinity. [ABSTRACT FROM AUTHOR]

The non-isothermal crystallization behavior of poly(trimethylene terephthalate) (PTT) and its blends with a liquid crystalline polymer, namely Vectra A950 (VA), was studied by differential scanning calorimetry. The values of the half-time of crystallization, t0.5 and the parameter F( T) in the combined Avrami and Ozawa equation indicated that VA can enhance the PTT crystallization rate by acting as a nucleating agent. The crystallization activation energy of the PTT phase increased with increasing VA content. The blends were immiscible, as can be inferred from their morphology. Thermogravimetric analysis of the blends revealed improved thermal stability by the incorporation of VA. [ABSTRACT FROM AUTHOR]

Structural and thermal properties of the 20Li2O-80TeO2 glass were studied using X-ray diffraction analysis and differential scanning calorimetry techniques to understand and control the crystallization process on this glass. The γ-TeO2, α-TeO2 and α-Li2Te2O5 phases were identified during the crystallization in this glass. Activation energies and Avrami exponent n were calculated from non-isothermal measurements for glasses with different particle size. The mean values $$ \bar n $$ of Avrami exponent were obtained for glasses with 63–75 and 45–63 μm particle sizes such as $$ \bar n_1 < \bar n_2 < \bar n_3 $$, but glasses with particle size 38–45 μm and smaller than 38 g,m presented $$ \bar n_1 \approx \bar n_2 < \bar n_3 $$. [ABSTRACT FROM AUTHOR]

Glasses with the composition Li2O·2SiO2· nTiO2 and Li2O·2SiO2· nZrO2, where n=0, 0.03, 0.062, 0.1, were prepared and the onset and peak temperatures have been determined by DTA. From these characteristic temperatures, the kinetic parameters describing the nucleation and crystal growth have been obtained by isoconversional methods. The kinetic parameters have been used for the calculation of nucleation and crystal growth times for individual glasses so determining the order of glass stability at reheating. The stability of glasses increases with the content of TiO2 or ZrO2 where the increase is higher for ZrO2. Within the concentration range under study, the increase of both times with the metal oxide concentration is quadratic. It has been discussed that the crystallization kinetics does not obey the Arrhenius law and, therefore, when using the evaluation methods based on this law, the results should not be extrapolated outside the temperature range of the measurements. [ABSTRACT FROM AUTHOR]

This project investigated the interaction between poly- L-lactic acid (PLLA) and several therapeutic agents. Low percentage crystallinity PLLA (melt-pressed, molded and drawn) was studied. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to characterize the crystallinity and thermal properties in a thermal cycling process. Repeatable melting and crystallization events were observed. The thermal properties of a drug-polymer combination using PLLA and an acidic, basic, neutral and zwitterionic material were investigated. A sufficient quantity of the drug must be present in the polymer to be observed thermally. Release of atropine sulfate from a PLLA tablet showed a two-phase process. [ABSTRACT FROM AUTHOR]

Two integral isoconversional methods (Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose) and the invariant kinetic parameters method (IKP) were used in order to examine the kinetics of the non-isothermal crystallisation of a silica-soda-lead glass. The objective of the paper is to show the usefulness of the IKP method to determine both the activation parameters and the kinetic model of the investigated process. Thismethod associated with the criterion of coincidence of kinetic parameters for all heating rates and some procedures of the evaluation of the parameter from Johnson–Mehl–Avrami–Erofeev–Kolmogorov (JMAEK) equation led us to the following kinetic triplet: activation energy, E=170.5±2.5 kJ mol–1 , pre-exponential factor, A=1.178±0.350·10 10 min–1 and JMAEK model ( A m) m=1.5. [ABSTRACT FROM AUTHOR]

The polymerization of a cyclic butylene terephthalate (CBT) oligomer was studied as a function of temperature ( T=200 and 260°C, respectively) by modulated DSC (MDSC). The first heating was followed by cooling after various holding times (5, 15 and 30 min) prior to the second heating which ended always at T=260°C. This allowed us to study the crystallization and melting behavior of the resulting polybutylene terephthalate (PBT), as well. In contrary to the usual belief, the CBT polymerization is exothermic and the related process is superimposed to that of the CBT melting. The melting behavior of the PBT was affected by the polymerization mode (performed below or above the melting temperature of the PBT product) of the CBT. Annealing above the melting temperature of PBT yielded a product featuring double melting. This was attributed to the presence of crystallites with different degrees of perfection. The crystals perfection which occurred via recrystallization/remelting was manifested by a pronounced exothermic peak in the non-reversing trace. [ABSTRACT FROM AUTHOR]

We have fabricated glasses in the Bi-2223 H Tc superconductor system with Bi2Sr2Ca2Cu3-xErxO10+ δ nominal composition, where x=0.5 and 1.0, by the glass-ceramic technique. Using an analysis developed for non-isothermal crystallization studies, information on some aspects of crystallization temperature and thermal properties has been obtained. The crystallization studies were made using DTA with several uniform rates. The calculations of crystallization activation energies, Ea, and the Avrami parameters, n, were made based on the non-isothermal kinetic theory of Kissinger and the Ozawa’s equations. The DTA data of the samples showed that the first crystallization temperature, Tx1, increases and the second crystallization temperature, Tx2, decreases by increasing the Er concentration. This suggests that the Er substitution had significant effect on the glassification of the BSCCO material due to change on the surface nucleation and increased ionic activities at high temperature region. The activation energy for crystallization, Ea, of the samples was also showed an increase at high Er concentration case. However, the Avrami parameter, n, decreased from 2.5 to 1.7 for x=0.5 and 1.0 samples, respectively. This suggests that the growth mechanism is diffusion-controlled and three-dimensional parabolic growth takes place near the first crystallization temperature. The oxidization rates and the activation barrier for oxygen out-diffusion process, E, was calculated using the TG data. It was found that the total mass gain in the x=0.5 sample is comparably smaller than that of the x=1.0 sample. This shows that the oxygen absorption of the x=1.0 sample is faster than the x=0.5 sample, leading to increase in the oxidization rate in the x=1.0 material. [ABSTRACT FROM AUTHOR]