Information on the noncrystalline phase of nascent iPP given by slow calorimetry

1997 ◽  
Vol 75 (10) ◽  
pp. 1354-1362 ◽  
Author(s):  
X. Zhang ◽  
H. Phuong-Nguyen ◽  
P. Bernazzani ◽  
I. Lapes ◽  
G. Delmas
Keyword(s):  
Heat Content ◽  
Melting Process ◽  
Heat Of Fusion ◽  
Main Peak ◽  
Physical Network ◽  
Polymer Melting ◽  
New Information ◽  
Temperature Ramp ◽  
Conventional Dsc ◽  
Noncrystalline Phase

Nascent isotactic polypropylene (iPP) has a lower crystallinity and a different X-ray pattern than recrystallized iPP. Heat flows during the melting of nascent highly stereoregular iPP samples are recorded with a Setaram C80 calorimeter over a wide T range (30–280 °C). The rate of heating–cooling is 1–3 K/h, i.e., much lower than with conventional DSC. Melting is performed after annealing at 30 < Tannealing < 140 °C and with or without substrate. The main peak, that found by DSC, is associated with melting of monoclinic crystals and gives an enthalpy ΔHDSC. Two other peaks, usually above and below the main peak, are observed. These are associated with a slower process of disordering a physical network, which was produced in the sample during polymerization. The sum of ΔHDSC and ΔHnetwork equals ΔHtotal. When melting is complete ΔHtotal is equal to ΔH0, the heat of fusion of perfect iPP crystals. This work presents new information on: (i) the noncrystalline phase of nascent iPP and the heat content of a semicrystalline polymer; (ii) the modifications of the melting process due to strain development, brought about by expansion in the material during the temperature ramp when a physical network is present; and (iii) the effect of a substrate on the polymer melting process. Keywords: nascent iPP, slow calorimetry, strain-melting, change of enthalpy, substrates.

Crystallization of Isotactic Poly(propylene) in Solution as Followed by Slow Calorimetry

1995 ◽  
Vol 60 (11) ◽  
pp. 1905-1924 ◽  
Author(s):  
Hong Phuong-Nguyen ◽  
Geneviève Delmas
Keyword(s):  
Molecular Weight ◽  
Crystal Growth ◽  
High Temperature ◽  
Heat Of Fusion ◽  
Complete Dissolution ◽  
Polymer Molecular Weight ◽  
Solvent Quality ◽  
Temperature Ramp ◽  
Poly Propylene

Dissolution, crystallization and second dissolution traces of isotactic poly(propylene) have been obtained in a slow temperature ramp (3 K h-1) with the C80 Setaram calorimeter. Traces of phase-change, in presence of solvent, are comparable to traces without solvent. The change of enthalpy on heating or cooling, ∆Htotal, over the 40-170 °C temperature range, is the sum of two contributions, ∆HDSC and ∆Hnetwork. The change ∆HDSC is the usual heat obtained in a fast temperature ramp and ∆Hnetwork is associated with a physical network whose disordering is slow and subject to superheating due to strain. When dissolution is complete, ∆Htotal is equal to ∆H0, the heat of fusion of perfect crystals. The values of ∆Htota for nascent and recrystallized samples are compared. Dissolution is the tool to evaluate the quality of the crystals. The repartition of ∆Htotal, into the two endotherms, reflects the quality of crystals. The crystals grown more rapidly have a higher fraction of network crystals which are stable at high T in the solvents. A complete dissolution, i.e. a high temperature (170 °C or more) is necessary to obtain good crystals. The effect of concentration, polymer molecular weight and solvent quality on crystal growth is analyzed.

THERMODYNAMIC CHARACTERIZATION OF WATER ADSORBED ON PEAT

1977 ◽  
Vol 57 (4) ◽  
pp. 497-501 ◽  
Author(s):  
B. D. KAY ◽  
J. B. GOIT
Keyword(s):  
Heat Content ◽  
Adsorbed Water ◽  
Heat Of Fusion ◽  
Vapor Pressures ◽  
Thermodynamic Characterization ◽  
Dry Conditions ◽  
Adsorption Of Water ◽  
Adsorption On Heterogeneous Surfaces ◽  
Water Contents

A preliminary thermodynamic characterization of water adsorbed on peat of sphagnum origin has been completed. The characterization has indicated that this organic material has a reactivity with respect to water which is similar to that of a montmorillonite clay. Under the relatively dry conditions of this study, less water was adsorbed by samples with a very low rubbed fibre content. The relative partial molar heat content of the adsorbed water approached the latent heat of fusion at water contents of about 16%. Additional measurements are required in the range of relative vapor pressures of 0.0–0.5 in order to determine if Halsey’s theory for adsorption on heterogeneous surfaces is applicable to the adsorption of water on peat.

Heat Transfer During Constrained Melting of Graphite-Based Nanofluids in a Spherical Capsule

2016 ◽  
Author(s):  
Zi-Qin Zhu ◽  
Li-Wu Fan ◽  
Min-Jie Liu ◽  
Yi Zeng
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Natural Convection ◽  
Phase Change ◽  
Dynamic Viscosity ◽  
Fold Increase ◽  
Melting Process ◽  
Heat Of Fusion ◽  
Graphite Nanosheets ◽  
Spherical Capsule

Transient heat transfer during constrained melting of graphite-based solid-liquid phase change nanofluids in a spherical capsule was investigated experimentally. Nanofluids filled with self-prepared graphite nanosheets (GNSs) were prepared at various loadings up to 1% by weight, using a straight-chain saturated fatty alcohol, i.e., 1-dodecanol (C12H26O), with a nominal melting point of 22 °C as the base fluid. In-house measured thermal properties were adopted for data reduction, including thermal conductivity, dynamic viscosity, latent heat of fusion, specific heat capacity and density. A proper experimental approach depended on volume expansion was figured out to monitor the melting process of nano-enhanced phase change fluid in a spherical capsule indirectly and qualitatively characterize the process. A variety of boundary temperatures were also adopted to vary the intensity of natural convection. It was shown that under low boundary temperatures, a monotonous melting acceleration came into being while increasing the loading due to the monotonously increased thermal conductivity of the nanofluids. While increasing the boundary temperature leads to more intensive natural convection that in turn slowed down melting under the influence of nanoparticles because the contribution by natural convection is significantly suppressed by the dramatically grown dynamic viscosity, e.g., more than 60-fold increase at the loading of 1 wt.%. The melting rate is determined by the competition between the enhanced heat conduction and deteriorated natural convection.

A thermodynamical investigation of the system benzene-diphenyl

1951 ◽  
Vol 243 (862) ◽  
pp. 169-196 ◽  
Keyword(s):  
Free Energy ◽  
Experimental Method ◽  
Thermodynamic Functions ◽  
Virial Coefficients ◽  
Heat Content ◽  
Heat Of Fusion ◽  
Partial Pressures ◽  
Pure Benzene ◽  
Good Agreement ◽  
Saturated Solutions

The partial molar heat content, entropy and free energy of benzene in solutions of diphenyl in benzene have been determined by measurement of the partial pressures of benzene over the solu-­ tions. The whole composition range has been covered (as far as the solubility of diphenyl will allow), at temperatures from 30 to 80° C. A check on the accuracy of the experimental method has been made by measuring the vapour pressure of pure benzene over this temperature range, and good agreement has been found with recent values reported in the literature. The calculation of the thermodynamic functions from the vapour pressures requires a knowledge of the compressibility of benzene vapour. An experimental method has been devised for determining the gas imperfections of vapours, and using this the second and third virial coefficients of benzene vapour at various temperatures have been obtained. The variation of the thermodynamic functions of benzene with the composition of the solutions has been compared with that to be expected on the basis of recent statistical theories. It is found that whereas the non-ideal partial molar free energy can be accounted for almost exactly by the theo­ retical expression, the separate heat contents and entropies show some deviations. It is suggested that these deviations arise from slight changes in molecular packing as the composition is varied. The activities of benzene and diphenyl in saturated solutions at 30 to 60° C have been obtained from the vapour pressures of saturated solutions at these temperatures. These lead to values for the latent heat of fusion of diphenyl in agreement with the calorimetric value. The yapour pressure of saturated solutions is discussed.

scholarly journals Sound Velocity Measurement of Shock-Compressed Quartz at Extreme Conditions

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1334
Author(s):  
Liang Sun ◽  
Huan Zhang ◽  
Zanyang Guan ◽  
Weiming Yang ◽  
Youjun Zhang ◽  
...  
Keyword(s):  
Sound Velocity ◽  
Melting Process ◽  
Extreme Conditions ◽  
Planetary Interiors ◽  
New Information ◽  
Laser Facility ◽  
Magnesium Silicates ◽  
Magma Oceans ◽  
Physical And Chemical ◽  
Key Parameter

The physical properties of basic minerals such as magnesium silicates, oxides, and silica at extreme conditions, up to 1000 s of GPa, are crucial to understand the behaviors of magma oceans and melting in Super-Earths discovered to data. Their sound velocity at the conditions relevant to the Super-Earth’s mantle is a key parameter for melting process in determining the physical and chemical evolution of planetary interiors. In this article, we used laser indirectly driven shock compression for quartz to document the sound velocity of quartz at pressures of 270 GPa to 870 GPa during lateral unloadings in a high-power laser facility in China. These measurements demonstrate and improve the technique proposed by Li et al. [PRL 120, 215703 (2018)] to determine the sound velocity. The results compare favorably to the SESAME EoS table and previous data. The Grüneisen parameter at extreme conditions was also calculated from sound velocity data. The data presented in our experiment also provide new information on sound velocity to support the dissociation and metallization for liquid quartz at extreme conditions.

Alternative Soda-Lime Glass Batch to Reduce Energy Consumption

2013 ◽  
Vol 545 ◽  
pp. 24-30 ◽  
Author(s):  
Ekarat Meechoowas ◽  
Kanit Tapasa ◽  
Tepiwan Jitwatcharakomol
Keyword(s):  
Melting Temperature ◽  
Raw Materials ◽  
Glass Batch ◽  
Heat Content ◽  
Melting Process ◽  
Soda Lime ◽  
Raw Material ◽  
Soda Lime Glass ◽  
Kinetic Properties ◽  
Atmosphere Temperature

Soda-lime glass is produced by melting sand (SiO2), soda ash (Na2CO3), lime stone (CaCO3) together with effective additives such as dolomite (CaMg(CO3)2) and an important structural modification, alumina (Al2O3) in which the melting temperature is very high around 1500°C. With this reason, to dissolve alumina, high amount of energy is needed. Consequently, one of possibilities to reduce the melting energy is replacing alumina by the raw material with a lower enthalpy of melting. The heat required for melting the batch of raw materials from atmosphere temperature to melting temperature is called exploited heat (Hex), which can be calculated from chemical enthalpy (H°chem) and heat content (Hmelt) at reference temperature (Tex). From thermodynamic approach, chemical enthalpy of alumina is higher than feldspar (KAlSiO3) or pyrophyllite (Al2Si4O10(OH)2). For the glass batch with alumina, the calculated exploited heat is 540 kWh/ton while the batch with feldspar or pyrophyllite is lower, namely 534 and 484 kWh/ton, respectively. This means that the melting process can be emerged easier than the batch with alumina because the melting point of feldspar is around 1200°C and pyrophyllite dehydroxylates around 900°C. The kinetic properties of batch melting were investigated by Batch-Free Time method, which defines the melting ability of the modified batch. According to thermodynamic calculation, it was found that both alternative batches were melted easier. The study showed that feldspar or pyrophyllite could be used instead of alumina without significant changes in glass chemical composition and physical properties. The concern of using feldspar or pyrophyllite is the quantity of minor impurities which affect to the color appearance especially in clear glass products.

Effect of Mechanical Activation on the Heat of Fusion of a Conventional Batch Used for the Manufacture of Float Glass

MRS Advances ◽  
2019 ◽  
Vol 4 (57-58) ◽  
pp. 3171-3180
Author(s):  
J. López-Cuevas ◽  
G. Vargas-Gutiérrez ◽  
P.P. Rodríguez-Salazar ◽  
S.R. Ruiz-Ontiveros
Keyword(s):  
Mechanical Activation ◽  
Raw Materials ◽  
Chemical Reactivity ◽  
Melting Process ◽  
Soda Lime ◽  
Initial Mixture ◽  
Float Glass ◽  
Heat Of Fusion ◽  
Activation Process ◽  
Batch Melting

ABSTRACTAn initial mixture of raw materials (batch) typically used for the manufacture of conventional soda-lime float glass was subjected to a mechanical activation process for 30 or 60 minutes in a planetary ball mill. An intensification of the chemical reactivity of the batch, which was directly related with the increase in the milling time, was observed. This accelerated the chemical reactions that took place during the batch melting process between sodium, calcium and magnesium carbonates and other components of the mixture, which happened at significantly lower temperatures with respect to the batch without mechanical activation. The heat of fusion of the batch, estimated using a methodology previously reported in the literature, indicated that the mechanical activation given to the initial mixture of raw materials decreased the energy consumed during the batch melting. This was also evidenced by a decrease in the temperature at which the release of CO2 ended, which was considerably larger than that previously reported in the literature based solely on the decrease in the particle size of a batch of similar composition achieved by dry sieving.

scholarly journals Determining the Heat of Fusion and Specific Heat of Microencapsulated Phase Change Material Slurry by Thermal Delay Method

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 179
Author(s):  
Krzysztof Dutkowski ◽  
Marcin Kruzel ◽  
Bartosz Zajączkowski
Keyword(s):  
Phase Change ◽  
Specific Heat ◽  
Phase Change Material ◽  
Water Solution ◽  
Heat Of Fusion ◽  
Main Peak ◽  
Liquid Form ◽  
Microencapsulated Phase Change Material ◽  
Thermal Delay ◽  
Change Material

This paper details an experimental study that was performed to investigate the specific heat of microencapsulated phase change material (mPCM) slurry and its heat of fusion at the PCM phase change transition temperature. Six samples (mPCM slurry concentrate with the water solution of propylene glycol used as a main base liquid) were prepared. As the concentrate contains 43.0% mPCM, the actual mass fraction amounts to 8.6, 12.9, 17.2, 21.5, 25.8, and 30.1 wt%, respectively. The thermal delay method was used. Samples were cooled from 50 °C to 10 °C. A higher concentration of microcapsules caused a proportional increase in the specific heat of slurry at the main peak melting temperature. The maximum value of the specific heat changed from 9.2 to 33.7 kJ/kg for 8.6 wt%, and 30.1 wt%, respectively. The specific heat of the mPCM slurry is a constant quantity and depends on the concentration of the microcapsules. The specific heat of the slurry (PCM inside microcapsules in a liquid form) decreased from 4.0 to 3.8 kJ/(kgK) for 8.6 wt%, and 30.1 wt% of mPCM, respectively. The specific heat of the slurry (PCM inside microcapsules in a liquid form) was higher than when the PCM in the microcapsules is in the form of a solid and increased from 4.5 to 5.2 kJ/(kgK) for 8.6 wt% and 30.1 wt% of mPCM, respectively.

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