scholarly journals Thermal studies on Arabic gum - carrageenan polysaccharides film

2017 ◽  
Vol 19 ◽  
pp. 80 ◽  
Author(s):  
J Jamaludin ◽  
F Adam ◽  
R Abdul Rasid ◽  
Z Hassan
Keyword(s):  
Activation Energy ◽  
Chemical Engineering ◽  
Thermal Studies ◽  
Control Sample ◽  
Activation Energies ◽  
Thermal Transitions ◽  
Scanning Calorimetry ◽  
Polyethylene Glycol 400 ◽  
Arabic Gum ◽  
Endothermic Transition

<p>The main objective of this work is to develop film and study the thermal characteristics of polysaccharides films at various concentration of carrageenan in the mixture by calculating activation energy of polysaccharides films. There were four (4) film samples of two polysaccharides combination; arabic gum (AG) and carrageenan (C) with different formulations; sample A, sample B, sample C and sample D prepared. Sample A film is the control sample that contained only arabic gum and distilled water (DI) with 40% weight arabic gum per volume DI water (w/v%). Meanwhile for sample B and C were prepared with concentration 40 w/v% of Arabic gum and two differents of carrageenan concentrations; 1 w/v% and 10 w/v% respectively. Polyethylene glycol 400 (PEG 400) as a plasticiser was added into sample D film. The sample films were thermally characterized using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) under nitrogen atmosphere. The major thermal transitions as well as, activation energies of the major decomposition stages were determined. Sample A and B films exhibited the highest (112.43 kJ/mol) and the lowest (102.89 kJ/mol) activation energy of thermal decomposition, respectively. The activation energies were lower at larger amounts of sulfate groups from carrageenan on the degradation reactions. The DSC trend for all samples shows two (2) major intense peaks recorded in the DSC thermograms; an endothermic transition at temperature around 100<sup>°</sup>C and followed by an exothermic transition at temperature around 300<sup>°</sup>C. The endothermic transition is due to the heat absorption for dehydration of water, H2O and the decomposition of samples process. Meanwhile, the exothermic transition is caused by the formation of H<sub>2</sub>O, CO and CH<sub>4</sub> in polysaccharide film from dehydration, depolymerisation and decomposition at the high-temperature stages.</p><p>Chemical Engineering Research Bulletin 19(2017) 80-86</p>

Glass transformation in vitreous As2Se3 studied by conventional and temperature-modulated differential scanning calorimetry

2001 ◽  
Vol 16 (8) ◽  
pp. 2399-2407 ◽  
Author(s):  
S. O. Kasap ◽  
D. Tonchev
Keyword(s):  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Relaxation Time ◽  
Glass Transition ◽  
Activation Energies ◽  
Temperature Modulation ◽  
Glass Transition Region ◽  
Scanning Calorimetry ◽  
Modulated Differential Scanning Calorimetry ◽  
Apparent Activation Energies

We have studied the glass transition behavior of vitreous As2Se3 by carrying out temperature-modulated differential scanning calorimetry (TMDSC) and conventional differential scanning calorimetry (DSC) experiments to measure the glass transition temperature Tg. In TMDSC experiments we have examined the reversing heat flow (RHF), that is the complex heat capacity CP in the glass transition region as the glass is cooled from a temperature above the glass transition temperature (from a liquidlike state) and also as the glass is heated starting from room temperature (from a solidlike state). The RHF, or CP versus T, in TMDSC changes sigmoidally through the glass transition region without evincing an enthalpic peak which is one of its distinct advantages for studying the glass transformations. The Tg measurements by TMDSC were unaffected by the amplitude of the temperature modulation. We have determined apparent activation energies by using Tg-shift methods based on the Tg-shift with the frequency (ω) of temperature modulation in the TMDSC mode and Tg-shift with heating and cooling rates, r and q, respectively, in the DSC mode. It is shown that the apparent activation energies ∆h* obtained from ln ω versus 1/Tg and ln q versus 1/Tg plots are not the same, but nonetheless, they are approximately the same as the apparent activation energy ∆hn of the viscosity over the same temperature range where the empirical Vogel expression of Henderson and Ast, η = 12.9 exp[2940/(T - 335)], was used for the viscosity. The latter observation is in agreement with the assertion that the structural relaxation time Ʈ is proportional to the viscosity h. The apparent activation energy ∆hr obtained from the ln r versus 1/Tg plot during heating DSC scans is lower than ∆h* observed during cooling scans. The results are discussed in terms of a phenomenological Narayanaswamy type relaxation time. It was observed that Tg obtained from TMDSC cooling experiments did not depend on the underlying cooling rate for q ≤ 1 °C min-1; and for temperature amplitudes 0.5–5 °C. The transition due to the temperature modulation was well separated from the transition due to the underlying cooling rate. Further, the apparent activation energies obtained from ln ω versus 1/Tg during cooling and heating scans for q and r ≤ 1 °C min−1 are approximately the same as expected from Hutchison's calculations using a single relaxation time model of TMDSC experiments.

scholarly journals Synthesis, Structural, Electrical, and Thermal Studies of ( and ) Ferroelectric Ceramics

ISRN Ceramics ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Shiv K. Barbar ◽  
M. Roy
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Thermal Studies ◽  
Activation Energies ◽  
Ferroelectric Ceramics ◽  
Scanning Calorimetry ◽  
Conventional Solid State Reaction ◽  
Modulated Differential Scanning Calorimetry ◽  
Orthorhombic Crystal Structure

The polycrystalline ceramic samples of lead barium niobate with general formula ( and 0.4) were prepared by conventional solid state reaction method. The room temperature X-ray diffraction patterns reveal that both of the samples have orthorhombic crystal structure with space group Cm2m. The dielectric constant and dissipation factor were measured as a function of frequency (100 Hz-2 MHz) and temperature (RT-660K). The DC electrical conductivity of both the samples was measured from RT to 660 K. The activation energies calculated from log σ versus 1000/T curves in ferroelectric phase of the compounds are 1.09 eV for pure () sample and 1.36 eV for Ba-substituted () sample. The values of activation energies show that the substitution of Ba2+ ion on Pb2+ ion site increases the resistivity of pure PbNb2O6 () ceramic. The modulated differential scanning calorimetry (MDSC) has been used to investigate the phase transition temperature of both the compounds and also to see the effect of Ba2+ ion substitution on the phase transition temperature, specific heat, and other thermal parameters of the compound.

scholarly journals Staling of sponge cakes with added emulsifiers

2020 ◽  
Author(s):  
Maria Marudova ◽  
Stanko Stankov ◽  
Marianna Baeva
Keyword(s):  
Thermal Analysis ◽  
Differential Scanning Calorimetry ◽  
Differential Thermal Analysis ◽  
Control Sample ◽  
Bound Water ◽  
Storage Period ◽  
Scanning Calorimetry ◽  
Retarding Effect ◽  
Starch Retrogradation ◽  
Endothermic Transition

AbstractThe effect of three types of emulsifiers (polyglycerol monostearate ester – E475, sucrose stearate ester – E473 and modified inulin palmitate ester – HP-25) on the starch retrogradation in sponge cake (SC) during storage was investigated. The method of differential scanning calorimetry (DSC) was applied to determine the changes in the starch retrogradation during the staling process. The retrogradation temperature and the enthalpy of the endothermic transition decreased when emulsifiers were added. The lowest values of the enthalpy for the whole storage period were found for SC with 1% HP-25. The methods of differential thermal analysis (DTA) and thermogravimetry analysis (TGA) showed significantly bigger (1.43 times) amount of strongly bound water in the crumb of the SC with E475 and HP-25 in comparison to the control sample on the sixth day of storage. Based on our results, emulsifiers possessed retarding effect on the starch retrogradation and extend the shelf-life of the SC.

scholarly journals Variation in Activation Energy and Nanoscale Characteristic Length at the Glass Transition

2008 ◽  
Vol 3 (1) ◽  
pp. 31-43
Author(s):  
Ion Dranca
Keyword(s):  
Activation Energy ◽  
Heat Capacity ◽  
Glass Transition ◽  
Effective Activation Energy ◽  
Activation Energies ◽  
Linear Size ◽  
Effective Activation ◽  
Scanning Calorimetry ◽  
Clay System ◽  
Heat Capacity Measurements

Differential scanning calorimetry has been used to study the α-relaxation (glass transition) in virgin polystyrene (PS), PS-clay nanocomposite, amorphous indomethacin (IM), maltitol (Mt) and glucose (Gl). Variation of the effective activation energy (E) throughout the glass transition has been determined by applying an advanced isoconversional method to DSC data on the glass transition. The relaxations have been characterized by determining the effective activation energies (E) and evaluating the sizes of cooperatively rearranging regions at the glass transition (Vg). The values of Vg have been determined from the heat capacity data. The α-relaxation demonstrates markedly larger values of E (~340 vs ~270 kJ mol-1) for the PS-clay system than for virgin PS. For IM in the glass transition region, the effective activation energy of relaxation decreases with increasing temperature from 320 to 160 kJ mol-1. In the Tg region E decreases (from~250 to ~150 kJ mol-1 in maltitol and from~220 to ~170 kJ mol-1 in glucose) with increasing T as typically found for the α-relaxation. It has been found that in the sub-Tg region E decreases with decreasing T reaching the values ~60 (glucose) and ~70 (maltitol) kJ -1 that are comparable to the literature values of the activation energies for the β-relaxation. Heat capacity measurements have allowed for the evaluation of the cooperatively rearranging region in terms of the linear size The PS-clay system has also been found to have a significantly larger value of Vg, 36.7 nm3 as compared to 20.9 nm3 for PS. Heat capacity measurements of IM have allowed for the evaluation of the cooperatively rearranging region (CRR) in term of linear size (3.4 nm) and the number of molecules (90). The size of CRR have been determined as 3.1 (maltitol) and 3.3 (glucose) nm.

scholarly journals FTIR and Thermal Studies on Nylon-66 and 30% Glass Fibre Reinforced Nylon-66

2009 ◽  
Vol 6 (1) ◽  
pp. 23-33 ◽  
Author(s):  
Julie Charles ◽  
G. R. Ramkumaar ◽  
S. Azhagiri ◽  
S. Gunasekaran
Keyword(s):  
Activation Energy ◽  
Glass Fibre ◽  
Thermal Studies ◽  
Polymeric Materials ◽  
Thermally Stable ◽  
Melting Behaviour ◽  
Thermal Transitions ◽  
Nylon 66 ◽  
Degradation Temperature ◽  
Glass Fibre Reinforced

The present study deals with the characterization of the polymeric materialsviz.,nylon-66 and 30% glass fibre reinforced nylon-66 (GF Nylon-66) by employing FTIR and thermal measurements. The complete vibrational band assignment made available for nylon-66 and GF nylon-66 using FTIR spectra confirm their chemical structure. FTIR spectroscopy provides detailed information on polymer structure through the characteristic vibrational energies of the various groups present in the molecule. The thermal behavior of nylon-66 and GF nylon-66 essential for proper processing and fabrication was studied from TGA and DTA thermograms. The thermal stability of the polymers was studied from TGA and the activation energy for the degradation of the polymeric materials was calculated using Murray-White plot and Coats-Redfern plot. The polymer with high activation energy is more thermally stable. GF nylon-66 is found to be more thermally stable than nylon-66. The major thermal transitions such as crystalline melting temperature (Tm) and degradation temperature (Td) of the polymers were detected from DTA curves. The melting behaviour of the polymer depends upon the specimen history and in particular upon the temperature of crystallization. The melting behaviour also depends upon the rate at which the specimen is heated. The various factors such as molar mass and degree of chain branching govern the value of Tmin different polymers.

scholarly journals Crystallization Behavior and Mechanical Properties of Poly(ε-caprolactone) Reinforced with Barium Sulfate Submicron Particles

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2368
Author(s):  
Hegoi Amestoy ◽  
Paul Diego ◽  
Emilio Meaurio ◽  
Jone Muñoz ◽  
Jose-Ramon Sarasua
Keyword(s):  
Barium Sulfate ◽  
Thermal Studies ◽  
Polarized Light ◽  
Optical Microscope ◽  
Submicron Particles ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
Nucleation Effect ◽  
Crystal Fraction ◽  
Light Optical Microscope

Poly(ε-caprolactone) (PCL) was mixed with submicron particles of barium sulfate to obtain biodegradable radiopaque composites. X-ray images comparing with aluminum samples show that 15 wt.% barium sulfate (BaSO4) is sufficient to present radiopacity. Thermal studies by differential scanning calorimetry (DSC) show a statistically significant increase in PCL degree of crystallinity from 46% to 52% for 25 wt.% BaSO4. Non-isothermal crystallization tests were performed at different cooling rates to evaluate crystallization kinetics. The nucleation effect of BaSO4 was found to change the morphology and quantity of the primary crystals of PCL, which was also corroborated by the use of a polarized light optical microscope (PLOM). These results fit well with Avrami–Ozawa–Jeziorny model and show a secondary crystallization that contributes to an increase in crystal fraction with internal structure reorganization. The addition of barium sulfate particles in composite formulations with PCL improves stiffness but not strength for all compositions due to possible cavitation effects induced by debonding of reinforcement interphase.

scholarly journals The Influence of the Addition of Nuts on the Thermal and Rheological Properties of Wheat Flour

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3969
Author(s):  
Karolina Pycia ◽  
Lesław Juszczak
Keyword(s):  
Rheological Properties ◽  
Wheat Flour ◽  
Viscoelastic Properties ◽  
Control Sample ◽  
Scanning Calorimetry ◽  
Creep And Recovery ◽  
Research Material ◽  
Pasting Characteristics ◽  
Tan Δ ◽  
Weak Gels

The aim of the study was to assess the influence of replacing wheat flour with hazelnuts or walnuts, in various amounts, on the thermal and rheological properties of the obtained systems. The research material were systems in which wheat flour was replaced with ground hazelnuts (H) or walnuts (W) in the amount of 5%, 10%, and 15%. The parameters of the thermodynamic gelatinization characteristics were determined by the differential scanning calorimetry method. In addition, the pasting characteristics were determined with the use of a viscosity analyzer and the viscoelastic properties were assessed. Sweep frequency and creep and recovery tests were used to assess the viscoelastic properties of the tested gels. It was found that replacing wheat flour with nuts increased the values of gelatinization temperature, gelatinization, and retrogradation enthalpy, and the degree of retrogradation. The highest viscosity was characteristic of the control sample (2039 mPa·s), and the lowest for the paste with 15% addition of walnuts (1120 mPa·s). Replacing the flour with nuts resulted in a very visible reduction in the viscosity of such systems. In addition, gels based on the systems with the addition of H and W were weak gels (tan δ = G″/G′ > 0.1), and the values of G′ and G″ parameters decreased with the increased share of nuts in the systems. Creep and recovery analysis indicated that the systems in which wheat flour was replaced with hazelnuts were less susceptible to deformation compared to the systems with the addition of W.

scholarly journals High-Temperature Deformation of Naturally Aged 7010 Aluminum Alloy

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 581
Author(s):  
Abdulhakim A. Almajid
Keyword(s):  
Activation Energy ◽  
Aluminum Alloy ◽  
High Temperature ◽  
Threshold Stress ◽  
Activation Energies ◽  
Temperature Deformation ◽  
High Temperature Range ◽  
Temperature Range ◽  
True Activation Energy ◽  
Two Temperatures

This study is focused on the deformation mechanism and behavior of naturally aged 7010 aluminum alloy at elevated temperatures. The specimens were naturally aged for 60 days to reach a saturated hardness state. High-temperature tensile tests for the naturally aged sample were conducted at different temperatures of 573, 623, 673, and 723 K at various strain rates ranging from 5 × 10−5 to 10−2 s−1. The dependency of stress on the strain rate showed a stress exponent, n, of ~6.5 for the low two temperatures and ~4.5 for the high two temperatures. The apparent activation energies of 290 and 165 kJ/mol are observed at the low, and high-temperature range, respectively. These values of activation energies are greater than those of solute/solvent self-diffusion. The stress exponents, n, and activation energy observed are rather high and this indicates the presence of threshold stress. This behavior occurred as a result of the dislocation interaction with the second phase particles that are existed in the alloy at the testing temperatures. The threshold stress decreases in an exponential manner as temperature increases. The true activation energy was computed by incorporating the threshold stress in the power-law relation between the stress and the strain. The magnitude of the true activation energy, Qt dropped to 234 and 102 kJ/mol at the low and high-temperature range, respectively. These values are close to that of diffusion of Zinc in Aluminum and diffusion of Magnesium in Aluminum, respectively. The Zener–Hollomon parameter for the alloy was developed as a function of effective stress. The data in each region (low and high-temperature region) coalescence in a segment line in each region.

scholarly journals Effect of CaO on catalytic combustion of semi-coke

2021 ◽  
Vol 10 (1) ◽  
pp. 011-020
Author(s):  
Luyao Kou ◽  
Junjing Tang ◽  
Tu Hu ◽  
Baocheng Zhou ◽  
Li Yang
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Combustion Rate ◽  
Activation Energies ◽  
Combustion Reaction ◽  
Tg Analysis ◽  
Conversion Rates ◽  
Apparent Activation Energies ◽  
Ozawa Integral Method ◽  
Addition Amount

Abstract Generally, adding a certain amount of an additive to pulverized coal can promote its combustion performance. In this paper, the effect of CaO on the combustion characteristics and kinetic behavior of semi-coke was studied by thermogravimetric (TG) analysis. The results show that adding proper amount of CaO can reduce the ignition temperature of semi-coke and increase the combustion rate of semi-coke; with the increase in CaO content, the combustion rate of semi-coke increases first and then decreases, and the results of TG analysis showed that optimal addition amount of CaO is 2 wt%. The apparent activation energy of CaO with different addition amounts of CaO was calculated by Coats–Redfern integration method. The apparent activation energy of semi-coke in the combustion reaction increases first and then decreases with the increase in CaO addition. The apparent activation energies of different samples at different conversion rates were calculated by Flynn–Wall–Ozawa integral method. It was found that the apparent activation energies of semi-coke during combustion reaction decreased with the increase in conversion.

scholarly journals The Effect of α-Al(MnCr)Si Dispersoids on Activation Energy and Workability of Al-Mg-Si-Cu Alloys during Hot Deformation

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xiaoguo Wang ◽  
Jian Qin ◽  
Hiromi Nagaumi ◽  
Ruirui Wu ◽  
Qiushu Li
Keyword(s):  
Activation Energy ◽  
Aluminum Alloys ◽  
Constitutive Equation ◽  
Hot Deformation ◽  
Flow Instability ◽  
Void Formation ◽  
Activation Energies ◽  
Compression Tests ◽  
Softening Mechanism ◽  
Dynamic Softening

The hot deformation behaviors of homogenized direct-chill (DC) casting 6061 aluminum alloys and Mn/Cr-containing aluminum alloys denoted as WQ1 were studied systematically by uniaxial compression tests at various deformation temperatures and strain rates. Hot deformation behavior of WQ1 alloy was remarkably changed compared to that of 6061 alloy with the presence of α-Al(MnCr)Si dispersoids. The hyperbolic-sine constitutive equation was employed to determine the materials constants and activation energies of both studied alloys. The evolution of the activation energies of two alloys was investigated on a revised Sellars’ constitutive equation. The processing maps and activation energy maps of both alloys were also constructed to reveal deformation stable domains and optimize deformation parameters, respectively. Under the influence of α dispersoids, WQ1 alloy presented a higher activation energy, around 40 kJ/mol greater than 6061 alloy’s at the same deformation conditions. Dynamic recrystallization (DRX) is main dynamic softening mechanism in safe processing domain of 6061 alloy, while dynamic recovery (DRV) was main dynamic softening mechanism in WQ1 alloy due to pinning effect of α-Al(MnCr)Si dispersoids. α dispersoids can not only resist DRX but also increase power required for deformation of WQ1 alloy. The microstructure analysis revealed that the flow instability was attributed to the void formation and intermetallic cracking during hot deformation of both alloys.

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