Nonisothermal and Isothermal Degradation Kinetics of Thermotropic Liquid Crystal Copolyesters Containing BPA and BPAF Units

2016 ◽  
Vol 848 ◽  
pp. 179-183
Author(s):  
Peng Wei ◽  
Shuo Han Huang ◽  
Yi Min Wang
Keyword(s):  
Liquid Crystal ◽  
Degradation Kinetics ◽  
Degradation Mechanism ◽  
Nitrogen Atmosphere ◽  
High Glass Transition Temperature ◽  
Isothermal Heating ◽  
Thermotropic Liquid Crystal ◽  
Kinetics Of ◽  
Bisphenol Af ◽  
Dynamic Heating

The thermotropic liquid crystal copolyester P-BPA2.5 and P-BPAF2.5 with low melting temperature and high glass transition temperature were obtained by introducing 2.5mol% bisphenol A (BPA), bisphenol AF (BPAF) and terephthalic acid (TA) receptively into the molecular chain of poly (oxybenzoate-co-oxynaphthoate). The isothermal and nonisothermal degradation behavior of the two copolyesters P-BPA2.5 and P-BPAF2.5 were studied by thermo-gravimetry analysis (TGA) under nitrogen atmosphere. The degradation kinetics of the copolyesters under dynamic and isothermal heating conditions was evaluated byKissinger-Akahira-Sunose (KAS) and iso-conversional methodrespectively. Results showed that the activation energy (E) values followed the order P-BPAF2.5>P-BPA2.5 under dynamic heating atmosphere. However, the P-BPA2.5 showed a better thermal stability as compared with P-BPAF2.5 under isothermal heating conditions. The differences of degradation mechanism between the two copolyesters may be a reason for this phenomenon, which was discussed in detail in the text.

Pyrolysis kinetics of recycled polyesters

2015 ◽  
Vol 27 (4) ◽  
pp. 523-531 ◽  
Author(s):  
Jaber Al-Juaidiyah
Keyword(s):  
Textile Industry ◽  
Degradation Kinetics ◽  
Nitrogen Atmosphere ◽  
Coefficient Of Determination ◽  
Pyrolysis Kinetics ◽  
Polybutylene Terephthalate ◽  
Exponential Factor ◽  
Content Type ◽  
Kissinger Model ◽  
Kinetics Of

Purpose – The purpose of this paper is to study the non-isothermal degradation kinetics of recycled polybutylene terephthalate, polytrimethylene terephthalate and polyethylene terephthalate using thermogravimetric analysis (TGA) in a nitrogen atmosphere. Design/methodology/approach – To achieve this goal, the author utilized standard kinetic models, such as Coats-Redfern and Kissinger equations, for analysis of the TGA data. Findings – When applied to the TGA data, the Kissinger model resulted in a coefficient of determination (R2) value greater than 0.99. Originality/value – This study describes the maiden application of the Kissinger model to obtain the pre-exponential factor (A) and activation energy (E) for different polyester systems used in the textile industry.

Thermal Oxidative Degradation Behavior of Fluorinated Thermotropic Liquid Crystal Copolyesters

2015 ◽  
Vol 1088 ◽  
pp. 343-347
Author(s):  
Peng Wei ◽  
Shuo Han Huang ◽  
Yan Ping Wang ◽  
Yi Min Wang
Keyword(s):  
Liquid Crystal ◽  
Oxidative Degradation ◽  
Thermal Oxidative Degradation ◽  
Degradation Behavior ◽  
Molar Percentage ◽  
Good Thermal Stability ◽  
Thermotropic Liquid Crystal ◽  
Air Atmosphere ◽  
Degradation Activation Energy ◽  
Bisphenol Af

In this study, the thermal oxidative degradation behavior of thermotropic liquid crystal copolyesters P-BPAFx containing 2.5-10 mol% bisphenol AF unit were evaluated by thermogravimetric analysis (TGA) technique under air atmosphere and the degradation activation energy (E) was obtained from Kissinger and Kissinger-Akahira-Sunose (KAS) method. The degradation behavior of copolyester are strongly dependent on the molar percentage of BPAF unit. Results showed that the E values obtained by the two methods increase first and then decrease slightly with increasing the BPAF unit and follow the order P-BPAF5.0< P-BPAF10<P-BPAF2.5, indicating P-BPAF2.5 has good thermal stability. The reason for this phenomenon was discussed in detail in the text.

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.

Photocatalytic Degradation of Bisphenol AF in TiO2 Suspension

2014 ◽  
Vol 955-959 ◽  
pp. 2334-2339
Author(s):  
Pin Wen Wang
Keyword(s):  
Photocatalytic Degradation ◽  
Reaction Rate ◽  
Degradation Kinetics ◽  
Fluoride Concentration ◽  
Reaction Rate Constant ◽  
Rate Model ◽  
Initial Concentration ◽  
Fluoride Pollution ◽  
Kinetics Of ◽  
Bisphenol Af

The photodegradation behavior of bisphenol AF (BPAF) in TiO2 suspension was investigated. The influence of dissolved oxygen, TiO2 dosage, fluoride, and initial BPAF concentration on the degradation of BPAF was studied and described in details. The main purposes were to clarify the degradation kinetics of BPAF and quantify the fluoride concentration during the degradation. At an initial concentration of 40 mol/L, more than 97% of TOC was removed efficiency was achieved within 540 min irradiation, and the concentration of fluoride was 0.98 mg/L. Degradation of BPAF followed the Langmuir–Hinshelwood kinetics rate model and the reaction rate constant kre was 1.21 μM/min. The results obtained indicated that TiO2 photocatalytic degradation is a highly effective way to remove BPAF without any generation of more toxic products or fluoride pollution.

The influence of pH on the molecular degradation mechanism of PLGA

MRS Advances ◽  
2018 ◽  
Vol 3 (63) ◽  
pp. 3883-3889 ◽  
Author(s):  
Rainhard Machatschek ◽  
Burkhard Schulz ◽  
Andreas Lendlein
Keyword(s):  
Degradation Products ◽  
Bulk Material ◽  
Degradation Kinetics ◽  
Degradation Mechanism ◽  
Controlled Drug Release ◽  
Interfacial Rheology ◽  
Alkaline Conditions ◽  
A Chain ◽  
The Impact ◽  
Kinetics Of

ABSTRACTPoly[(rac-lactide)-co-glycolide] (PLGA) is used in medicine to provide mechanical support for healing tissue or as matrix for controlled drug release. The properties of this copolymer depend on the evolution of the molecular weight of the material during degradation, which is determined by the kinetics of the cleavage of hydrolysable bonds. The generally accepted description of the degradation of PLGA is a random fragmentation that is autocatalyzed by the accumulation of acidic fragments inside the bulk material. Since mechanistic studies with lactide oligomers have concluded a chain-end scission mechanism and monolayer degradation experiments with polylactide found no accelerated degradation at lower pH, we hypothesize that the impact of acidic fragments on the molecular degradation kinetics of PLGA is overestimated. By means of the Langmuir monolayer degradation technique, the molecular degradation kinetics of PLGA at different pH could be determined. Protons did not catalyze the degradation of PLGA. The molecular mechanism at neutral pH and low pH is a combination of random and chainend-cut events, while the degradation under strongly alkaline conditions is determined by rapid chainend cuts. We suggest that the degradation of bulk PLGA is not catalyzed by the acidic degradation products. Instead, increased concentration of small fragments leads to accelerated mass loss via fast chain-end cut events. In the future, we aim to substantiate the proposed molecular degradation mechanism of PLGA with interfacial rheology.

Thermal degradation kinetics of PP/PLA nanocomposite blends

2018 ◽  
Vol 32 (12) ◽  
pp. 1714-1730 ◽  
Author(s):  
Dev K Mandal ◽  
Haripada Bhunia ◽  
Pramod K Bajpai
Keyword(s):  
Thermal Degradation ◽  
Degradation Kinetics ◽  
Frequency Factor ◽  
Nitrogen Atmosphere ◽  
Thermal Degradation Kinetics ◽  
Heating Rates ◽  
Degradation Kinetic ◽  
Thermal Degradation Behavior ◽  
Kinetics Of ◽  
Thermal Stability Of

In this article, the effect of adding polylactide (PLA) and nanoclay on the thermal stability of polypropylene (PP) films was analyzed using thermogravimetric analysis. The thermal degradation kinetic parameters such as activation energy ( Ea), order of reaction ( n), and frequency factor (ln ( Z)) of the samples were studied over a temperature range of 30–550°C. Analyses were performed under nitrogen atmosphere with four different heating rates (i.e. 5, 10, 15, and 20°C min−1). The Ea was calculated by Kissinger, Kim–Park, and Flynn–Wall methods. The Ea value of PP was much higher than PLA, whereas the addition of PLA and nanoclay in PP decreased the Ea. The addition of compatibilizer increased the compatibility and Ea of blended films upto some extent. The lifetime of PP was found to be decreased with the addition of PLA and nanoclay. Studies indicated that the thermal degradation behavior and lifetime of the investigated samples depend on the fractions of constituents and heating rates.

scholarly journals Impact of Active Chlorines and •OH Radicals on Degradation of Quinoline Using the Bipolar Electro-Fenton Process

Water ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 128
Author(s):  
Wenlong Zhang ◽  
Jun Chen ◽  
Jichao Wang ◽  
Cheng-Xing Cui ◽  
Bingxing Wang ◽  
...  
Keyword(s):  
Degradation Kinetics ◽  
Degradation Mechanism ◽  
Supporting Electrolyte ◽  
Reaction System ◽  
Oxygen Demand ◽  
Oh Radicals ◽  
Fenton Process ◽  
Reaction Conditions ◽  
Initial Ph ◽  
Kinetics Of

Quinoline is a typical nitrogenous heterocyclic compound, which is carcinogenic, teratogenic, and mutagenic to organisms, and its wastewater is difficult to biodegrade directly. The bipolar electro-Fenton process was employed to treat quinoline solution. The process/reaction conditions were optimized through the single factor experiment. The degradation kinetics of chemical oxygen demand (COD) was analyzed. To get the degradation mechanism and pathways of quinoline, the intermediate products were identified by gas chromatograph–mass spectrometer (GC–MS). By using sodium chloride as supporting electrolyte in the electro-Fenton reaction system with initial pH 3.0, conductivity 15,800 µs/cm, H2O2 concentration 71 mmol/L, current density 30.5 mA/cm2, and applied voltage 26.5 V, 75.56% of COD was decreased by indirect oxidation with electrogeneration of hydroxyl radicals (•OH) and active chloric species in 20 min. The COD decrease of quinoline solution followed the first order reaction kinetic model. The main products of quinoline degradation were 2(1H)-quinolinone, 4-chloro-2(1H)-quinolinone, 5-chloro-8-hydroxyquinoline, and 5,7-dichloro-8-hydroxyquinoline. Furthermore, two possible degradation pathways of quinoline were proposed, supported with Natural charge distribution on quinoline and intermediates calculated at the theoretical level of MN15L/6-311G(d).

The influence of bisphenol AF unit on thermal behavior of thermotropic liquid crystal copolyesters

2014 ◽  
Vol 586 ◽  
pp. 45-51 ◽  
Author(s):  
Peng Wei ◽  
Miko Cakmak ◽  
Yuwei Chen ◽  
Xinhang Wang ◽  
Yanping Wang ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Thermal Behavior ◽  
Thermotropic Liquid Crystal ◽  
Bisphenol Af
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