scholarly journals INFLUENCE OF ALUMINUM POWDER CONCENTRATION ON MECHANISM AND KINETIC REGULARITIES OF CRYSTALLIZATION OF COMPOSITES BASED ON LOW DENSITY POLYETHYLENE

2020 ◽  
Vol 63 (2) ◽  
pp. 77-83
Author(s):  
Najaf T. Kakhramanov ◽  
Khayala V. Allakhverdieva ◽  
Fatima A. Mustafayeva ◽  
Marat I. Abdullin
Keyword(s):  
Aluminum Powder ◽  
Polymer Matrix ◽  
Specific Volume ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Dilatometric Curve ◽  
First Order ◽  
Powder Concentration ◽  
First Order Phase Transition ◽  
First Order Phase

The results of the study of the influence of the aluminum powder concentration on the mechanism and the regularity of changes in the dependence of specific volume on temperature in the range of 25-180 °C in composites based on low density polyethylene are presented. By extrapolating the upper and lower branches of the dilatometric curve, approximate values of the glass transition temperature of the composites are found. Extrapolation of the lower branch of the dilatometric curve of the considered polymer composites to the absolute temperature allowed us to determine the value of the "occupied" specific volume and the "free" specific volume. Using the step dilatometry method, the temperature of the first-order phase transition of composites was found, which varies depending on the aluminum powder concentration in the composition of low density polyethylene. The concentration of aluminum powder with a particle size 1-2 µm varied between 0.5 – 30 wt. %. It has been established that the loading of 0.5 wt. % of aluminum powder practically does not affect the regularity of change in the dilatometric curve of the initial polymer matrix. At a filler concentration of 1.0 wt. % and higher, a significant change occurs in the regularities of change in these curves, expressed in a decrease in the value of the specific volume of the composites. A sharp decrease in the specific volume or an increase in the density of the composites in viscous-flow and solid states clearly indicated the reinforcing role of aluminum powder. In composites based on low density polyethylene, the dependence of the free specific volume on temperature and on the concentration of aluminum powder is determined. It is shown that an increase in the concentration of aluminum powder in the composition of low density polyethylene is accompanied by a regular decrease in the free volume of the polymer matrix. The obtained data confirms our idea that particles of aluminum powder are involved not only in the formation of heterogeneous crystallization centers, but are also forced into the amorphous region as the spherolite crystalline formations grow. In the coordinates of Avraami, the kinetic regularities of the process of isothermal crystallization in the region of the first-order phase transition are investigated. It has been established that with an increase in the degree of filling of the polymer matrix, the mechanism of crystallization from spherical (three-dimensional) type of growth of crystalline formations passes into a plate-like (two-dimensional) with the continuous formation of crystallization centers. Recommendations are given on the practical use of the results of a study of the crystallization process of composites as applied to the technology of their processing by injection molding.

scholarly journals Isotherms of crystallization of nanocomposites on the basis of low density polyethylene and ash of domestic wastes

2019 ◽  
pp. 49-51
Author(s):  
U. M. Mammadli ◽  
A. A. Gasanova ◽  
F. A. Mustafayeva ◽  
R. Sh. Gadzhiev ◽  
R. V. Kurbanova ◽  
...  
Keyword(s):  
Phase Transition ◽  
Low Density Polyethylene ◽  
Filler Concentration ◽  
Low Density ◽  
Domestic Waste ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase ◽  
Kinetics Of ◽  
Phase Transition Zone

The dilatometry method was used to study the effect of the concentration of domestic waste ash on the dependence of the specific volume of nanocomposites based on low density polyethylene on the temperature. The kinetics of crystallization in the first-order phase transition zone has been studied. The mechanism of crystallization depending on the filler concentration is established.

scholarly journals Notizen: Specific Volume Studies on Some Nematic Liquid Crystals

1975 ◽  
Vol 30 (8) ◽  
pp. 1094-1096 ◽  
Author(s):  
Birendra Bahadur
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Order Phase Transition ◽  
Specific Volume ◽  
Nematic Liquid Crystals ◽  
Adiabatic Compressibility ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase ◽  
Sudden Jump

Abstract The temperature variation of the specific volume of two nematic liquid crystals (HBT and OBT) has been observed in both the nematic and isotropic regions. A sudden jump is observed in the vicinity of the nematic-isotropic transition indicating a first order phase transition. Pretransitional effects are found to occur only on the nematic side of the transition. This accords with the Maier-Saupe theory. Some parameters such as SK , A, the adiabatic compressibility, the Rao number, and the van der Waals constant are also determined.

Phase Separation and Solidification of Fluid Phosphorus

2006 ◽  
Vol 987 ◽  
Author(s):  
Yoshinori Katayama ◽  
Yasuhiro Inamura ◽  
Hiroyuki Saitoh ◽  
Wataru Utsumi
Keyword(s):  
Phase Separation ◽  
Solidification Process ◽  
Low Density ◽  
Fluid Sample ◽  
X Ray ◽  
First Order ◽  
Solid Mixture ◽  
First Order Phase Transition ◽  
First Order Phase ◽  
Scanning Electron

AbstractFluid phosphorus exhibits a macroscopic phase separation during a pressure-induced first-order phase transition between low-density fluid and high-density fluid. Solidification process of the phase-separated fluid sample was monitored by x-ray radiography and the obtained solid sample was investigated by optical and scanning electron microscopy. A solid mixture of black parts and red parts was obtained from the phase-separated sample. Three different morphologies were observed in the red part of the sample.

Morphological studies of linear (AB)n multiblock copolymers and their blends

1992 ◽  
Vol 50 (1) ◽  
pp. 384-385
Author(s):  
Richard J. Spontak ◽  
Steven D. Smith ◽  
Arman Ashraf
Keyword(s):  
Electron Microscopy ◽  
Microphase Separation ◽  
Multiblock Copolymers ◽  
First Order ◽  
Morphological Studies ◽  
Transmission Electron ◽  
First Order Phase Transition ◽  
Covalently Bonded ◽  
Total Molecular Weight ◽  
First Order Phase

Block copolymers are composed of sequences of dissimilar chemical moieties covalently bonded together. If the block lengths of each component are sufficiently long and the blocks are thermodynamically incompatible, these materials are capable of undergoing microphase separation, a weak first-order phase transition which results in the formation of an ordered microstructural network. Most efforts designed to elucidate the phase and configurational behavior in these copolymers have focused on the simple AB and ABA designs. Few studies have thus far targeted the perfectly-alternating multiblock (AB)n architecture. In this work, two series of neat (AB)n copolymers have been synthesized from styrene and isoprene monomers at a composition of 50 wt% polystyrene (PS). In Set I, the total molecular weight is held constant while the number of AB block pairs (n) is increased from one to four (which results in shorter blocks). Set II consists of materials in which the block lengths are held constant and n is varied again from one to four (which results in longer chains). Transmission electron microscopy (TEM) has been employed here to investigate the morphologies and phase behavior of these materials and their blends.

scholarly journals Low-Density Polyethylene Films Carrying ferula asafoetida Extract for Active Food Packaging: Thermal, Mechanical, Optical, Barrier, and Antifungal Properties

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Razieh Niazmand ◽  
Bibi Marzieh Razavizadeh ◽  
Farzaneh Sabbagh
Keyword(s):  
Polymer Matrix ◽  
Food Packaging ◽  
Barrier Properties ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Optical Barrier ◽  
Leaf Extracts ◽  
Polyethylene Films ◽  
Active Food Packaging ◽  
Ferula Asafoetida

The physical, thermal, mechanical, optical, microstructural, and barrier properties of low-density polyethylene films (LDPE) containing ferula asafoetida leaf and gum extracts were investigated. Results showed a reduction in elasticity and tensile strength with increasing extract concentration in the polymer matrix. The melting temperature and enthalpy increased with increasing concentration of extracts. The films containing extracts had lower L∗ and a∗ and higher b∗ indices. The films containing leaf extract had more barrier potential to UV than the gum extracts. The oxygen permeability in films containing 5% of leaf and gum extracts increased by 2.3 and 2.1 times, respectively. The morphology of the active films was similar to bubble swollen islands, which was more pronounced at higher concentrations of gum and leaf extracts. FTIR results confirmed some chemical interactions of ferula extracts with the polymer matrix. At the end of day 14th, the growth rate of Aspergillus niger and Saccharomyces cerevisea in the presence of the PE-Gum-5 reduced more than PE-Leaf-5 (3.7 and 2.4 logarithmic cycles, respectively) compared to the first day. Our findings showed that active LDPE films have desire thermo-mechanical and barrier properties for food packaging.

scholarly journals Gravitational wave signals of dark matter freeze-out

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Danny Marfatia ◽  
Po-Yan Tseng
Keyword(s):  
Phase Transition ◽  
Dark Matter ◽  
Gravitational Waves ◽  
Order Phase Transition ◽  
First Order ◽  
Stochastic Background ◽  
First Order Phase Transition ◽  
Relic Abundance ◽  
First Order Phase ◽  
Freeze Out

Abstract We study the stochastic background of gravitational waves which accompany the sudden freeze-out of dark matter triggered by a cosmological first order phase transition that endows dark matter with mass. We consider models that produce the measured dark matter relic abundance via (1) bubble filtering, and (2) inflation and reheating, and show that gravitational waves from these mechanisms are detectable at future interferometers.

scholarly journals Dark Matter production from relativistic bubble walls

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Aleksandr Azatov ◽  
Miguel Vanvlasselaer ◽  
Wen Yin
Keyword(s):  
Phase Transition ◽  
Dark Matter ◽  
Electroweak Phase Transition ◽  
First Order ◽  
Matter Production ◽  
First Order Phase Transition ◽  
Relic Abundance ◽  
Higgs Portal ◽  
First Order Phase ◽  
Gravitational Background

Abstract In this paper we present a novel mechanism for producing the observed Dark Matter (DM) relic abundance during the First Order Phase Transition (FOPT) in the early universe. We show that the bubble expansion with ultra-relativistic velocities can lead to the abundance of DM particles with masses much larger than the scale of the transition. We study this non-thermal production mechanism in the context of a generic phase transition and the electroweak phase transition. The application of the mechanism to the Higgs portal DM as well as the signal in the Stochastic Gravitational Background are discussed.

scholarly journals Solving puzzles in deformed JT gravity: phase transitions and non-perturbative effects

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Clifford V. Johnson ◽  
Felipe Rosso
Keyword(s):  
Phase Structure ◽  
Scalar Potential ◽  
String Equation ◽  
Two Dimensional ◽  
Leading Order ◽  
Classical Analysis ◽  
First Order ◽  
First Order Phase Transition ◽  
Definition Of ◽  
First Order Phase

Abstract Recent work has shown that certain deformations of the scalar potential in Jackiw-Teitelboim gravity can be written as double-scaled matrix models. However, some of the deformations exhibit an apparent breakdown of unitarity in the form of a negative spectral density at disc order. We show here that the source of the problem is the presence of a multi-valued solution of the leading order matrix model string equation. While for a class of deformations we fix the problem by identifying a first order phase transition, for others we show that the theory is both perturbatively and non-perturbatively inconsistent. Aspects of the phase structure of the deformations are mapped out, using methods known to supply a non-perturbative definition of undeformed JT gravity. Some features are in qualitative agreement with a semi-classical analysis of the phase structure of two-dimensional black holes in these deformed theories.

Sign in / Sign up

Export Citation Format

Share Document