THERMAL PROTECTION OF POLYAMIDE 6/ACRYLONITRILE–BUTADIENE RUBBER THERMOPLASTIC-VULCANIZATES: INFLUENCE OF TYPE AND CONTENT ON BLEND PROPERTIES

2013 ◽  
Vol 86 (2) ◽  
pp. 286-298 ◽  
Author(s):  
Ana Catarina de Oliveira Gomes ◽  
Marcia Gomes Oliveira ◽  
Caio Marcio Paranhos ◽  
Bluma Guenther Soares
Keyword(s):  
Crystallization Process ◽  
Elevated Temperatures ◽  
Thermal Protection ◽  
Polyamide 6 ◽  
Butadiene Rubber ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Strength Differential ◽  
Processing Stability

ABSTRACT Polyamide 6 (PA6)/NBR blends are interesting because of their supposed properties at elevated temperatures. The blend, however, has a critical problem in terms of processing stability, as a result of the thermal degradation of the NBR phase. We evaluate a system of dissimilar addition of antioxidant in each phase (a combination of Irganox®/Irgafos® for the PA phase, and Naugard 445® for the NBR phase) and study the influence of these antioxidants on the properties of the blend. The evaluation was performed through tensile strength, differential scanning calorimetry (DSC), thermogravimetric analysis, and X-ray diffraction analysis. The influence of the antioxidant system on the crystallization process of the PA phase was evaluated through isothermal DSC analysis. Results showed the best combination of antioxidant addition in master batches and during processing.

The Effect of Sample Substrate on the Structural Properties of Co-Deposited Films of A-Ge:H

1990 ◽  
Vol 192 ◽  
Author(s):  
S.J. Jones ◽  
W.A. Turner ◽  
D. Pang ◽  
W. Paul
Keyword(s):  
Yield Strength ◽  
Crystallization Process ◽  
Exothermic Peak ◽  
High Yield ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Strength Differential ◽  
Substrate Temperatures ◽  
Deposited Films

ABSTRACTResults from structural measurements on r.f. glow discharge produced a-Ge:H films have been found to be substrate dependent. The variations in the results were found to depend on both the substrate temperature, Ts, and the substrate yield strength. Differential scanning calorimetry results were particularly affected by these parameters. For films prepared at Ts = 150°C, the DSC spectra contain two exothermic peaks when the films are deposited on low yield strength substrates while only one exothermic peak is present for films deposited on high yield strength substrates. One exothermic DSC peak is seen in spectra for all films prepared at Ts = 300°C no matter what substrates were used. This DSC spectral dependence is attributed to differences in the microstructure of films deposited at the two substrate temperatures, as seen in TEM micrographs. X-ray diffraction measurements performed on films annealed to various temperatures show that all of the exothermic DSC peaks described above are associated with the crystallization process. Thus, for the films prepared at low Ts, crystallization is either a one or two step process depending on the yield strength of the substrate.

scholarly journals SOLID DOSAGE FORM DEVELOPMENT OF GLIBENCLAMIDE WITH INCREASING THE SOLUBILITY AND DISSOLUTION RATE USING COCRYSTALLIZATION

2018 ◽  
Vol 10 (6) ◽  
pp. 181
Author(s):  
Arif Budiman ◽  
Sandra Megantara ◽  
Putri Raraswati ◽  
Tazyinul Qoriah
Keyword(s):  
Dissolution Rate ◽  
Dosage Form ◽  
Crystallization Process ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Solid Dosage Form ◽  
Solid Dosage ◽  
Infra Red ◽  
Form Development

Objective: The aim of this study was to develop a solid dosage form of glibenclamide with increasing the solubility properties of glibenclamide with cocrystallization method.Methods: Virtual screening was performed to investigate the interaction between glibenclamide and a co-former. Saccharin, the selected co-former, then co-crystallized with glibenclamide with equimolar ratios of 1:1 and 1:2 using the solvent evaporation method. Further characterization was performed using an infra-red (IR) spectrophotometer, differential scanning calorimetry (DSC), and powder x-ray diffraction (PXRD).Results: Co-crystals of 1:2 equimolar ratio were more highly soluble compared to pure glibenclamide (30-fold for 12 h and 24-fold for 24 h). The dissolution rate had also increased from 46.838% of pure glibenclamide to 77.655% of glibenclamide co-crystal in 60 min. There was no chemical reaction observed during the co-crystallization process based on the IR spectrum. However, there was a new peak in the X-Ray diffractogram and a reduction of melting point in the DSC curve, indicating the formation of co-crystals.Conclusion: The optimal co-crystal ratio of glibenclamide-saccharin was found to be 1:2, which was successful in improving the solubility of glibenclamide.

Exploring concomitant/conformational dimorphism in a difluoro-substituted phosphoramidate derivative

2019 ◽  
Vol 75 (4) ◽  
pp. 451-461 ◽  
Author(s):  
Avantika Hasija ◽  
Deepak Chopra
Keyword(s):  
Hydrogen Bonds ◽  
Intermolecular Interactions ◽  
Crystallization Process ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Dispersion Energy ◽  
Torsion Angles ◽  
X Ray ◽  
Electrostatic Contribution ◽  
Distinguished Contribution

The concomitant occurrence of dimorphs of diphenyl (3,4-difluorophenyl)phosphoramidate, C18H14F2NO3P, was observed via a solution-mediated crystallization process with variation in the symmetry-free molecules (Z′). The existence of two forms, i.e. Form I (block, Z′ = 1) and Form II (needle, Z′ = 2), was characterized by single-crystal X-ray diffraction, differential scanning calorimetry and powder X-ray diffraction. Furthermore, a quantitative analysis of the energetics of the different intermolecular interactions was carried out via the energy decomposition method (PIXEL), which corroborates with inputs from the energy framework and looks at the topology of the various intermolecular interactions present in both forms. The unequivocally distinguished contribution of strong N—H...O hydrogen bonds along with other interactions, such as C—H...O, C—H...F, π–π and C—H...π, mapped on the Hirshfeld surface is depicted by two-dimensional fingerprint plots. Apart from the major electrostatic contribution from N—H...O hydrogen bonds, the crystal structures are stabilized by contributions from the dispersion energy. The closely related melting points and opposite trends in the calculated lattice energies are interesting to investigate with respect to the thermodynamic stability of the observed dimorphs. The significant variation in the torsion angles in both forms helps in classifying them in the category of conformational polymorphs.

Synthesis and Investigation of Al2O3/SiO2 /ZrO2 Powders via Selective Laser Sintering

2012 ◽  
Vol 569 ◽  
pp. 297-300 ◽  
Author(s):  
Wei Wang ◽  
Yong Xian Liu ◽  
Xiang Dong Shi ◽  
Jin Hua Li ◽  
J.Y.H. Fuh
Keyword(s):  
Crystallization Process ◽  
Eutectic Temperature ◽  
Selective Laser Sintering ◽  
Ternary Eutectic ◽  
Composite Ceramic ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Scanning Electron Microcopy ◽  
Zro2 System

This research focused on the synthesis and investigation of the thermal properties and microstructure of the Al2O3/SiO2 /ZrO2 system applied to dental field. The composite ceramic was studied by scanning electron microcopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Detailed investigations of the different proportions of materials on the preparation and microstructural phases of ternary eutectic were presented. Furthermore, the crystallization process was investigated by using DSC and XRD. The results indicate that sintering microstructure of the ternary eutectic composite is greatly influenced by the materials proportions. The synthetically thermal analysis shows that the eutectic temperature of ternary Al2O3/SiO2 /ZrO2 composite is 1040°C, is well matching the phase diagram of Al2O3/SiO2 /ZrO2.

Crystallization of Zr-Ni metallic glasses

1988 ◽  
Vol 46 ◽  
pp. 456-457
Author(s):  
C. G. McKamey ◽  
D. M. Kroeger ◽  
D. S. Easton ◽  
J. A. Horton
Keyword(s):  
Metallic Glasses ◽  
Crystallization Process ◽  
Metastable Phase ◽  
Stoichiometric Composition ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Short Range Ordering ◽  
Equilibrium Phases ◽  
Reported Data

In a previous paper the results of a study of the crystallization of Zr-Ni metallic glasses of compositions between 55 and 70 at. % Zr were reported. Data from differential scanning calorimetry (DSC) and x-ray diffraction (XRD) were presented and discussed with respect to the phase transformations occurring during the crystallization process. A metastable crystalline phase, shown by DSC and XRD results to appear between 57 and 63.2 at. % Zr, was the first phase to appear upon heating the amorphous metal. (Evidence indicates the stoichiometric composition for this phase is approximately 60% Zr.) This metastable phase transforms to the equilibrium crystalline phases (ZrNi and Zr2Ni) upon further heating. For compositions of 55-57 and 63.5-70% Zr only the equilibrium phases appear upon heating. It was noted that phase separation and chemical short range ordering (SRO) are believed to play an important role in the crystallization of these alloys.

On polyamide 6-montmorillonite nanocomposites obtained by in-situ polymerization

e-Polymers ◽  
2007 ◽  
Vol 7 (1) ◽  
Author(s):  
Orietta Monticelli ◽  
Zenfira Musina ◽  
Francesca Ghigliotti ◽  
Saverio Russo ◽  
Valerio Causin
Keyword(s):  
In Situ Polymerization ◽  
Active Role ◽  
Polyamide 6 ◽  
Layered Silicates ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Close Relationship ◽  
Restricted Mobility

AbstractNanocomposites based on polyamide 6 (PA6) and montmorillonite-type (MMT) commercial clays, either unmodified or organically modified, were prepared by in-situ polymerization of ε-caprolactam (CL). The above materials were characterized in detail by a number of experimental techniques, including transmission electron microscopy (TEM), wide angle X-ray diffraction (WAXD), infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The formation of nanostructured systems was checked not only for the commonly used ω-aminoacid-modified clay, but also for other types of organoclays. In general, a correlation was found between nanoscopic swelling of the clay in molten CL, measured by X-ray diffraction, and level of clay dispersion in PA6. Specifically, with the most swellable clays, completely exfoliated nanocomposites were obtained. However, also layered silicates modified by compatibilizers having carboxy groups, because of the active role of latter in CL polymerization, formed delaminated nanocomposites despite their low degree of swelling in CL monomer. Both molecular mass and crystallinity of the polyamide matrix were found to be strongly influenced by the presence of specific layered silicates. In particular, some characterization techniques (WAXD, FTIR) have evidenced a close relationship between the MMT used and PA6 crystal structure. Namely, PA6 γ-form is promoted by clay with compatibilizer bearing the carboxy group, which is able to induce the polymer to be tethered on the silicate layers, thus provoking conditions of restricted mobility to occur.

scholarly journals Crystallization Process and Microstructural Evolution of Melt Spun Al-RE-Ni-(Cu) Ribbons

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 443
Author(s):  
Francisco G. Cuevas ◽  
Sergio Lozano-Perez ◽  
Rosa María Aranda ◽  
Raquel Astacio
Keyword(s):  
Crystallization Process ◽  
Primary Crystallization ◽  
Amorphous Structure ◽  
Intermetallic Phases ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Transmission Electron ◽  
Melt Spun ◽  
The Stability

The crystallization process, both at the initial and subsequent stages, of amorphous Al88-RE4-Ni8 alloys (RE = Y, Sm and Ce) has been studied. Additionally, the consequences of adding 1 at.% Cu replacing Ni or Al were studied. The stability of the amorphous structure in melt spun ribbons was thermally studied by differential scanning calorimetry, with Ce alloys being the most stable. The effect of Cu to reduce the nanocrystal size during primary crystallization was analyzed by transmission electron microscopy. This latter technique and x-ray diffraction showed the formation of intermetallic phases at higher temperatures. A clear difference was observed for the Ce alloy, with a simpler sequence involving the presence of Al3Ni and Al11Ce3. However, for the Y and Sm alloys, a more complex evolution involving metastable ternary phases before Al19RE5Ni3 appears, takes place. The shape of the intermetallics changes from equiaxial in the Ce alloys to elongate for Y and Sm, with longer particles for Sm and, in general, when Cu is added to the alloy.

scholarly journals Bi-based high Tc superconducting fibers by melt extraction

1992 ◽  
Vol 7 (9) ◽  
pp. 2365-2372
Author(s):  
J.J. Chang ◽  
G. Rudkowska ◽  
A. Zaluska ◽  
P. Rudkowski ◽  
J.O. Ström-Olsen ◽  
...  
Keyword(s):  
Crystallization Process ◽  
Lattice Parameter ◽  
Squid Magnetometry ◽  
X Ray Diffraction ◽  
Initial Composition ◽  
Scanning Calorimetry ◽  
High Tc ◽  
X Ray ◽  
Melt Extraction ◽  
Bcc Phase

Bismuth-based high Tc superconductors have been prepared as fibers by a technique of melt extraction. As-made, the fibers are amorphous with diameters ranging from 0.7 μm to 100 μm and lengths of up to 5 cm. The fibers were subsequently transformed into high Tc superconductors by heat treatment in air. Superconducting transitions at 105 K and 82 K were measured in annealed fibers of initial composition Bi1.8Pb0.2Sr2Ca3Cu4Ox by SQUID magnetometry. The volume fractions of superconducting phases were estimated to have lower bounds of 30% for 2212 and 5% for 2223. The crystallization process has been studied by differential scanning calorimetry, electron microscopy, and x-ray diffraction. Crystallization involves first the formation of the Bi-2201 phase and a bcc phase with lattice parameter a = 0.425 nm before finally significant fractions of both the Bi-2212 and Bi-2223 phases are formed.

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