scholarly journals Thermal Degradation Kinetics and pH-Rate Profiles of Iriflophenone 3,5-C-β-d-diglucoside, Iriflophenone 3-C-β-d-Glucoside and Mangiferin in Aquilaria crassna Leaf Extract

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 4898
Author(s):  
Eakkaluk Wongwad ◽  
Kornkanok Ingkaninan ◽  
Wudtichai Wisuitiprot ◽  
Boonchoo Sritularak ◽  
Neti Waranuch
Keyword(s):  
Activation Energy ◽  
Thermal Degradation ◽  
Shelf Life ◽  
Leaf Extract ◽  
Degradation Kinetics ◽  
Order Reaction ◽  
Thermal Degradation Kinetics ◽  
Order Kinetic ◽  
First Order ◽  
Aquilaria Crassna

The health benefits of the Aquilaria crassna Pierre ex Lecomte leaf extract (AE) make it very useful as an ingredient in food and pharmaceutical products. Iriflophenone 3,5-C-β-d-diglucoside (1), iriflophenone 3-C-β-d-glucoside (2) and mangiferin (3) are bioactive compounds of AE. We assessed the stability of AE by investigating the thermal degradation kinetics and shelf-life (t90%) of compounds 1, 2 and 3 using Arrhenius plot models and studied their pH-rate profiles. The results demonstrate that 1 and 2 were degraded, following a first-order kinetic reaction. The degradation of 3 followed first-order reaction kinetics when present in a solution and second-order reaction kinetics in the dried powder form of the extract. According to the first-order kinetic model, the predicted shelf-life (t90%) of the extract at 25 °C in dried form for compound 1 was 989 days with activation energy 129.86 kJ·mol−1, and for 2 it was 248 days with activation energy 110.57 kJ·mol−1, while in the extract solution, the predicted shelf-life of compounds 1–3 was 189, 13 and 75 days with activation energies 86.83, 51.49 and 65.28 kJ·mol−1, respectively. In addition, the pH-rate profiles of 1–3 indicated that they were stable in neutral to acidic environments.

Non-isothermal crystallization and thermal degradation kinetics of MXene/linear low-density polyethylene nanocomposites

e-Polymers ◽  
2017 ◽  
Vol 17 (5) ◽  
pp. 373-381 ◽  
Author(s):  
Xinxin Cao ◽  
Mengqi Wu ◽  
Aiguo Zhou ◽  
You Wang ◽  
Xiaofang He ◽  
...  
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Thermal Degradation ◽  
Isothermal Crystallization ◽  
Degradation Kinetics ◽  
Thermal Degradation Kinetics ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Linear Low Density Polyethylene ◽  
Kinetics Of

AbstractA novel two-dimensional material MXene was used to synthesize nanocomposites with linear low-density polyethylene (LLDPE). The influence of MXene on crystallization and thermal degradation kinetics of LLDPE was investigated. Non-isothermal crystallization kinetics was investigated by using differential scanning calorimetry (DSC). The experimental data was analyzed by Jeziorny theory and the Mo method. It is found that MXene acted as a nucleating agent during the non-isothermal crystallization process, and 2 wt% MXene incorporated in the nanocomposites could accelerate the crystallization rate. Findings from activation energy calculation for non-isothermal crystallization came to the same conclusion. Thermal gravity (TG) analysis of MXene/LLDPE nanocomposites was conducted at different heating rates, and the TG thermograms suggested the nanocomposites showed an improvement in thermal stability. Apparent activation energy (Ea) of thermal degradation was calculated by the Kissinger method, and Ea values of nanocomposites were higher than that of pure LLDPE. The existence of MXene seems to lead to better thermal stability in composites.

scholarly journals Thermal Degradation Kinetics of Anthocyanins Extracted from Purple Maize Flour Extract and the Effect of Heating on Selected Biological Functionality

Foods ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 1593
Author(s):  
Mioara Slavu (Ursu) ◽  
Iuliana Aprodu ◽  
Ștefania Adelina Milea ◽  
Elena Enachi ◽  
Gabriela Râpeanu ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Thermal Degradation ◽  
Degradation Kinetics ◽  
In Vitro Release ◽  
Conformational Space ◽  
Thermal Degradation Kinetics ◽  
Order Kinetic ◽  
Preliminary Heating ◽  
Self Association

The thermal degradation of the anthocyanins and antioxidant activity in purple maize extracts was determined between 80 and 180 °C. The anthocyanins were found to be thermostable in the temperature range of 80 to 120 °C, whereas at higher temperatures the thermal degradation of both anthocyanins and antioxidant activity followed a first-order kinetic model. The z-values started from 61.72 ± 2.28 °C for anthocyanins and 75.75 ± 2.87 °C for antioxidant activity. The conformational space of pairs of model anthocyanin molecules at 25 and 180 °C was explored through a molecular dynamics test, and results indicated the occurrence of intermolecular self-association reactions and intramolecular co-pigmentation events, which might help explaining the findings of the degradation kinetics. The relationship between thermal degradation of anthocyanins and antioxidant activity and the in vitro release was further studied. The unheated extracts showed a high stability under gastric environment, whereas after heating at 180 °C, the digestion ended quickly after 60 min. After simulated intestinal digestion, the anthocyanins were slowly decreased to a maximum of 12% for the unheated extracts, whereas an 83% decrease was found after preliminary heating at 180 °C. The thermal degradation of anthocyanins was positively correlated with the in vitro decrease of antioxidant activity.

Effect of Pd Nanoparticle on the Thermal Degradation Kinetics of Nylon 6/Pd Nanocomposite Prepared by a Dry Process

2012 ◽  
Vol 486 ◽  
pp. 27-33 ◽  
Author(s):  
Jae Young Lee ◽  
Sung Wan Hong ◽  
Kyeong Sik Han ◽  
Taeck Hong Lee ◽  
Hong Ki Lee
Keyword(s):  
Activation Energy ◽  
Thermal Degradation ◽  
Degradation Kinetics ◽  
Pd Nanoparticles ◽  
Nylon 6 ◽  
Thermal Degradation Kinetics ◽  
Heating Rates ◽  
Dry Process ◽  
Effect Of Pd ◽  
Kinetics Of

Palladium (Pd) nanoparticles were incorporated into a nylon 6 film via a dry process which consisted of simultaneous vaporization, penetration and reduction processes of palladium (II) bis (acetylacetonate, Pd (acac)2) at 180°C for various exposure time. The even dispersion of the generated Pd nanoparticles were observed by transmission electron microscope (TEM) and the Pd loading weight of about 15~43 wt% was measured by thermogravimetric analysis (TGA). In order to study the catalytic effect of Pd nanoparticles on the thermal degradation kinetics of nylon 6, TGA data at various heating rates were introduced to Flynn & Wall equation. The thermal degradation activation energy for neat nylon 6 was ca. 162~178 kJ/mol over the thermal degradation fraction of 0.05~0.40 while that of the nylon 6/Pd (26.5 wt%) nanocomposite was ca. 110~169 kJ/mol over the same fraction range. It meant the Pd nanoparticles were acted as a catalyst on the depolymerization of amide group in nylon 6. It was also found that the activation energy decreased slightly with the increasing Pd loading weight.

Thermal degradation kinetics of oxo-degradable PP/PLA blends

2018 ◽  
Vol 39 (1) ◽  
pp. 58-67 ◽  
Author(s):  
Dev K. Mandal ◽  
Haripada Bhunia ◽  
Pramod K. Bajpai
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Thermogravimetric Analysis ◽  
Thermal Degradation ◽  
Kinetic Parameters ◽  
Degradation Kinetics ◽  
Nitrogen Atmosphere ◽  
Thermal Degradation Kinetics ◽  
Heating Rates ◽  
Kinetics Of

AbstractIn this article, the influence of polylactide and pro-oxidant on the thermal stability, degradation kinetics, and lifetime of polypropylene has been investigated using thermogravimetric analysis under nitrogen atmosphere at four different heating rates (i.e. 5, 10, 15, and 20°C/min). The kinetic parameters of degradation were studied over a temperature range of 30–550°C. The derivative thermogravimetric curves have indicated single stage and two stage degradation processes. The activation energy was evaluated by using the Kissinger, Kim-Park, and Flynn-Wall methods under the nitrogen atmosphere. The activation energy value of polypropylene was much higher than that of polylactide. Addition of polylactide and pro-oxidant in polypropylene decreased the activation energy. The lifetime of polypropylene has also decreased with the addition of polylactide and pro-oxidant.

scholarly journals Thermomechanical and Morphological Studies of CFRP Tested in Different Environmental Conditions

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 63 ◽  
Author(s):  
Claudia Barile ◽  
Caterina Casavola ◽  
Paramsamy Vimalathithan ◽  
Marco Pugliese ◽  
Vincenzo Maiorano
Keyword(s):  
Activation Energy ◽  
Thermal Degradation ◽  
Mass Loss ◽  
Environmental Conditions ◽  
Degradation Kinetics ◽  
Fiber Reinforced Polymers ◽  
Thermal Degradation Kinetics ◽  
Morphological Studies ◽  
Significant Difference ◽  
Kinetics Of

The present work describes the mechanical characterization combined with the thermal degradation kinetics of Carbon Fiber Reinforced Polymers (CFRP). The thermal degradation kinetics of CFRP have never been studied in the past. In that regard, the present work focuses on studying the thermal degradation kinetics of CFRP tested mechanically at different environmental conditions. Tensile tests were performed on the specimens with different lay-ups at room temperature, elevated temperature (71 °C), and cryogenic conditions (−54 °C), and the same specimens were used for thermal degradation kinetic studies. Mechanical tests show different responses respect to the different environmental conditions and different fibers orientation. On the other hand, the thermogravimetric results, mass loss, and derivative mass loss, show no significant difference in the degradation of CFRP tested at different temperatures. However, the thermal degradation kinetics shows more insight into the degradation pattern of the materials. The activation energy of degradation shows that the degradation of materials subjected to elevated conditions increases rapidly in the later stages of degradation, suggesting the formation of high char yield. The varying activation energy has been related to different degradation mechanisms. Lastly, the morphology of the materials was studied under SEM to understand the structural change in the material after tested in different weather conditions.

Thermal Degradation Kinetics of Poly (vinyl chloride)

2010 ◽  
Vol 96 ◽  
pp. 245-249 ◽  
Author(s):  
Bin Han ◽  
Yu Long Wu ◽  
Guo Rui ◽  
Wei Feng ◽  
Zhen Chen ◽  
...  
Keyword(s):  
Activation Energy ◽  
Thermal Degradation ◽  
Degradation Kinetics ◽  
Mass Conservation ◽  
Thermal Degradation Kinetics ◽  
Pyrolysis Mechanism ◽  
Second Stage ◽  
Volatile Products ◽  
Infrared Spectrometer ◽  
Kinetics Of

The thermal degradation of PVC resin was examined by the thermogravimetric analysis (TGA). The pyrolysis volatile products were analyzed by Fourier transform infrared spectrometer synchronized with TG test (TG-FTIR). Based on the TG results, the kinetics of thermal degradation was studied by Friedman method. The pyrolysis mechanism was discussed also. The results indicate that the pyrolysis process of PVC can be divided into two main stages: 220°C - 380°C and 380°C - 560°C. By the calculation of mass conservation and TG-FTIR results, it can be supposed that not only HCl, but also some unsubstituted aromatics such as benzene were released during the first stage. The comparison of activation energy shows that the second stage exhibited higher activation energy than the first stage. Two activation energy values in the first stage confirm that there arose two reactions in the first stage.

Thermal degradation kinetics and lifetime of HDPE/PLLA/pro-oxidant blends

2016 ◽  
Vol 36 (9) ◽  
pp. 917-931 ◽  
Author(s):  
Gaurav Madhu ◽  
Dev K. Mandal ◽  
Haripada Bhunia ◽  
Pramod K. Bajpai
Keyword(s):  
Activation Energy ◽  
Thermal Degradation ◽  
Degradation Kinetics ◽  
Model Fitting ◽  
Frequency Factor ◽  
Thermal Degradation Kinetics ◽  
Heating Rates ◽  
Model Free ◽  
Calculation Technique ◽  
Thermal Degradation Behavior

Abstract The effect of adding poly(L-lactic acid) (PLLA) with and without a pro-oxidant additive cobalt stearate (CoSt) and compatibilizer maleic anhydride grafted polyethylene (MA-g-PE) on the thermal degradation and stability of high-density polyethylene (HDPE) films was analyzed using thermogravimetric analysis (TGA). The kinetic parameters [i.e. activation energy (Ea), order of reaction (n), and frequency factor ln(A)] of the samples were studied over a temperature range of 25°C–600°C at four heating rates (i.e. 5, 10, 15, and 20°C/min) through model-free techniques (e.g. Friedman, second Kissinger, and Flynn-Wall-Ozawa) and model-fitting techniques (e.g. Freeman-Carroll and Kim-Park). The value of Ea for neat HDPE was found to be much higher than PLLA; for the HDPE/PLLA blend, it was nearer to that of HDPE. An increase in the activation energy of 80/20 (HDPE/PLLA) blend was noticed by the addition of MA-g-PE. The TGA data and degradation kinetics were also used to predict the lifetime of the film samples. The lifetime of HDPE was found to decrease with the increase in the concentration of CoSt, thereby revealing its pro-oxidative ability. Minimum lifetime was noted for the HDPE/PLLA (80/20) sample blended with CoSt, which increased slightly in the presence of MA-g-PE. Studies indicated that the thermal degradation behavior and lifetime of the investigated film samples depends not only on the fractions of their constituents but also on the heating rates and calculation technique.

Effect of the Packing Material and Temperature on the Quality Characteristics of Dehydrated Carrot during Storage

2013 ◽  
Vol 448-453 ◽  
pp. 1115-1118
Author(s):  
Xiao Xiao Zhao ◽  
Dan Wang ◽  
Yue Ma ◽  
Xiao Yan Zhao
Keyword(s):  
Thermal Degradation ◽  
Room Temperature ◽  
Storage Temperature ◽  
Degradation Kinetics ◽  
Aluminum Foil ◽  
Packing Material ◽  
Thermal Degradation Kinetics ◽  
First Order ◽  
Kinetics Of

In order to maintain quality of dehydrated carrot during storage, the effect of storage temperature and packing material on dehydrated carrot was studied. Quality changing of dehydrated carrot packed in aluminum foil bag (AF) and high-density polyethylene (HDPE) at low temperature or room temperature were evaluated during storage. The results showed that the quality of samples in four packing methods had a reduction. The samples in AF underwent the least reduction in quality. The thermal degradation kinetics of carotenoids in dehydrated carrot was followed the first order thermal degradation kinetics reaction. The retention of carotenoids in AF was higher than that in HDPE. The k was the least. The value of non-enzymatic browning (NEB) increased. Samples in HDPE had lower quality than the samples in AF.

scholarly journals Drying characteristics and degradation kinetics in some parameters of goji berry (Lycium Barbarum L.) fruit during hot air drying

2021 ◽  
Vol 33 (1) ◽  
pp. 16-28
Author(s):  
Heysem Suat Batu ◽  
Çetin Kadakal
Keyword(s):  
Thermal Degradation ◽  
Antioxidant Capacity ◽  
Total Phenolic Content ◽  
Phenolic Content ◽  
Degradation Kinetics ◽  
Water Soluble ◽  
Thermal Degradation Kinetics ◽  
Total Phenolic ◽  
Order Kinetic ◽  
Lycium Barbarum

Drying kinetics, color properties, water-soluble vitamins, antioxidant capacity, total phenolic content, and thermal degradation kinetics of bioactive compounds in goji berries were investigated. Drying experiments were conducted at 50°C, 60°C, and 70°C. Page model was determined as the best model to predict experimental moisture ratio for all temperatures. Increment in drying temperature increased effective moisture diffusivity and drying rate values. Vitamins C and B6, antioxidant activity and total phenolic content were significantly reduced by drying. Thermal degradation of vitamins C and B6, antioxidant capacity and total phenolic content were found to fit the first order kinetic model.

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