scholarly journals THE INFLUENCE OF SURFACE INTERPHASE CHARACTERISTICS ON THE BEHAVIOR OF THE PHASE DIAGRAM OF NANOPARTICLES OF THE PALADIUM-PLATINUM ALLOY

2020 ◽  
pp. 243-251
Author(s):  
Людмила Павловна Арефьева ◽  
Ирина Гусейновна Шебзухова
Keyword(s):  
Phase Diagram ◽  
Statistical Method ◽  
Pt Nanoparticles ◽  
Metal Particles ◽  
Platinum Alloy ◽  
Interfacial Energies ◽  
Melting And Crystallization Temperatures ◽  
Melting And Crystallization

Проведен расчет температур плавления и кристаллизации и построена фазовая диаграмма металлических частиц системы Pd - Pt размером 10 нм. Поверхностная и межфазная энергии, их температурные и размерные зависимости оценивались модифицированным электронно-статистическим методом. Установлено, что вид фазовой диаграммы для наночастиц Pd - Pt имеет существенные отличия от диаграммы объемных фаз, включая гистерезис плавления-кристаллизации. The melting and crystallization temperatures have been calculated and the phase diagram of Pd - Pt metal particles of 10 nm in size has been constructed. The surface and interfacial energies, their temperature and size dependences were estimated by a modified electron-statistical method. It was found that the form of the phase diagram for Pd - Pt nanoparticles has significant differences from the diagram of bulk phases, including the melting-crystallization hysteresis.

TG and DSC as tools to analyse the thermal behaviour of EVA copolymers

2021 ◽  
pp. 009524432098816
Author(s):  
E Díez ◽  
A Rodríguez ◽  
JM Gómez ◽  
J Galán
Keyword(s):  
Vinyl Acetate ◽  
Thermal Behaviour ◽  
Isothermal Crystallization ◽  
Amorphous Polymer ◽  
Polymer Backbone ◽  
Avrami Model ◽  
Melting Temperatures ◽  
Melting And Crystallization Temperatures ◽  
Melting And Crystallization ◽  
Eva Copolymers

This paper analyses the thermal behaviour of six EVA copolymers supplied by REPSOL Company. In relation to crystallization and melting temperatures, both of them decrease when the vinyl acetate percentage increases, in agreement with the fact that polyethylene is a semi-crystalline material, whereas polyvinylacetate is an amorphous polymer. Actually, when the vinyl acetate percentage reaches 30%, the copolymer is practically amorphous. The non-isothermal crystallization was modelled with the modified Avrami model that showed, with the exception of EVA-460 (the material with higher vinyl acetate percentage), the presence of a secondary crystallization due to spherulite impingement in the later stage of the non-isothermal crystallization. The TG analysis indicated two weight loss stages, the first one due to acetic acid loss and the second one due to fragments of polymer backbone, which appear as two separate peaks in the DTG plots. Finally, due to the linear dependence of melting and crystallization temperatures and of the minimum value of DTG peaks on vinyl acetate percentage, it can be concluded that both TG and DSC techniques can be employed to determine the vinyl acetate percentage of a certain copolymer.

scholarly journals Restructuring polymers via nanoconfinement and subsequent release

2012 ◽  
Vol 8 ◽  
pp. 1318-1332 ◽  
Author(s):  
Alan E Tonelli
Keyword(s):  
Small Molecule ◽  
Polymer Chains ◽  
Crystalline Lattice ◽  
Host Molecule ◽  
Nanostructured Polymers ◽  
Narrow Channels ◽  
The Past ◽  
The Relationship ◽  
Melting And Crystallization Temperatures ◽  
Melting And Crystallization

During the past several years my students and I have been utilizing certain small-molecule hosts to create nanostructured polymers. This is accomplished by first forming noncovalently bonded inclusion complexes (ICs) between these small-molecule hosts and guest polymers, followed by the careful removal of the host crystalline lattice to obtain a coalesced bulk polymer. We have repeatedly observed that such coalesced polymer samples behave distinctly from those produced from their solutions or melts. Coalesced amorphous homopolymers exhibit higher glass-transition temperatures, while crystallizable homopolymers coalesced from their ICs display higher melting and crystallization temperatures, and sometimes different crystalline polymorphs. When ICs are formed with block copolymers or with two or more different homopolymers, the resulting coalesced samples can exhibit intimate mixing between the copolymer blocks, or between entire homopolymer chains. Each of the distinct behaviors observed for polymers coalesced from their ICs is a consequence of the structural organization of the polymer–host-ICs. Polymer chains in host-IC crystals are confined to occupy narrow channels (diameter ~0.5–1.0 nm) formed by the small-molecule hosts around the included guest polymers during IC crystallization. This results in the separation and high extension of the included guest polymer chains, which leads, following the careful removal of the host molecule lattice, to unique behaviors for the bulk coalesced polymer samples. Apparently, substantial degrees of the extended and unentangled natures of the IC-included chains are retained upon coalescence. In this review we summarize the behaviors and uses of coalesced polymers, and attempt to draw conclusions on the relationship between their behavior and the organization/structures/conformations of the constituent polymer chains achieved upon coalescence from their ICs.

Synthesis and characterisation of propene / higher 1-olefin copolymers with the catalyst system (CH3)2Si(2-methylbenz[e]indenyl)2ZrCl2/MAO

e-Polymers ◽  
2003 ◽  
Vol 3 (1) ◽  
Author(s):  
Robert Brüll ◽  
Nyambeni Luruli ◽  
Harald Pasch ◽  
Helgard G. Raubenheimer ◽  
E. Rotimi Sadiku ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Catalyst System ◽  
Crystallization Behaviour ◽  
Random Copolymers ◽  
Scanning Calorimetry ◽  
Melting And Crystallization Temperatures ◽  
Comonomer Content ◽  
Melting And Crystallization

Abstract The melting and crystallization behaviour of random copolymers of propene with 1-butene, 1-pentene and 1-hexene synthesized with the catalyst system (CH3)2Si(2-methylbenz[e]indenyl)2ZrCl2/methylaluminoxane (MAO) were investigated by differential scanning calorimetry and crystallization analysis fractionation (CRYSTAF). The melting and crystallization temperatures decreased linearly with increasing comonomer content. The depressions of the melting and crystallization temperatures are strongly dependent on the nature of the monomer and are more pronounced for copolymers of propene with 1-hexene than with 1-butene. In comparison to 1-hexene and 1-butene, the incorporation of 1-pentene leads to an intermediate behaviour. This is in contrast to the behaviour of copolymers of propene with longer chain 1-olefins, where the melting and crystallization temperatures are independent of the comonomer type. The depressant effects of the amount of comonomer incorporated on the melting and the crystallization temperatures are equal.

Nanocomposite of polypropylene/octadecylamine lamellar-zirconium phosphate: Influence of nanofiller and screw speed

2017 ◽  
Vol 52 (5) ◽  
pp. 701-711 ◽  
Author(s):  
Danielle M Mariano ◽  
Daniela FS Freitas ◽  
Luis C Mendes
Keyword(s):  
Thermal Stability ◽  
Zirconium Phosphate ◽  
Melt Processing ◽  
Screw Speed ◽  
Sem Images ◽  
Crystallinity Degree ◽  
Degradation Temperature ◽  
Diffraction Peaks ◽  
Melting And Crystallization Temperatures ◽  
Melting And Crystallization

Nanocomposite based on polypropylene and octadecylamine-modified lamellar-zirconium phosphate (PP/nano-ZrPOct) was prepared by melt processing. The action of the nanofiller and screw speed on the properties were evaluated. SEM images revealed that at highest screw speed, the higher nano-ZrPOct dispersion was achieved. In WAXD diffractrograms, some nanofiller diffraction peaks disappeared and a new peak was observed at low angle. There was evidence of increase of thermal stability although only discrete increasing in initial degradation temperature has been noticed. Melting and crystallization temperatures were invariable but crystallinity degree was influenced with a decreasing behavior at highest screw speed. The results strongly evidenced that the intercalation of the PP chains inside the nano-ZrPOct galleries and some degree of delamination of the nanofiller platelets have been achieved.

Statistical method of obtaining the combustion characteristics of metal particles

1969 ◽  
Vol 5 (3) ◽  
pp. 304-305 ◽  
Author(s):  
M. A. Gurevich ◽  
G. V. Ignatov ◽  
E. S. Ozerov ◽  
B. I. Sotnichenko
Keyword(s):  
Statistical Method ◽  
Combustion Characteristics ◽  
Metal Particles

scholarly journals SILATRANE-CONTAINING POLYMETHACRYLATES

2019 ◽  
Vol 14 (1) ◽  
pp. 82-89 ◽  
Author(s):  
V. V. Istratov ◽  
E. V. Andreeva ◽  
V. I. Gomzyak ◽  
V. A. Vasnev
Keyword(s):  
Molecular Weight ◽  
Thermal Properties ◽  
Three Dimensional ◽  
Gel Permeation Chromatography ◽  
Inert Atmosphere ◽  
Synthetic Methods ◽  
Ir And Nmr Spectroscopy ◽  
Gel Permeation ◽  
Melting And Crystallization Temperatures ◽  
Melting And Crystallization

The possibility of synthesizing silatrane-containing polymers was investigated using three different synthetic methods: the formation of silatrane fragments from polymers with trialkoxysilyl groups, the copolymerization of silatrane-containing monomers, and the reaction of silatranes with functional copolymers. The obtained polymethacrylate copolymers were characterized using gel permeation chromatography, IR and NMR spectroscopy. It was shown that depending on the synthesis scheme used, polymers were obtained in the form of three-dimensional structures or soluble products. It was established that the molecular weight of the synthesized polymers depended significantly on both the content of silatrane fragments and the synthesis technique used. It was shown that the modification of linear carboxyl-containing copolymers by silatranes allows the synthesis of high-molecular polymers with a high content of silatrane fragments. For the synthesized polymers, thermal properties were investigated, and the hydrophobicity of the surface of polymer films was also evaluated. It was found that all the studied polymers did not have clear melting and crystallization temperatures. The polymers were stable in an inert atmosphere up to 270-280 °C, whereas in air they decomposed at lower temperatures with the restructuring of the macromolecular skeleton and the formation of highly heat-resistant silicone structures. An increase in the content of silatrane moieties in the copolymers led to an increase in the hydrophilicity of polymers.

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