Pyrolysis gas-chromatographic studies of homopolymers and copolymers of chlorotrifluoroethylene with vinylidene fluoride and methyl methacrylate (original) (raw)
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Journal of Macromolecular Science, Part B, 2019
Commercial fluororubber SKF 32, fluoroplastic F-32L, fluoroelastomer Kel-F, fluoroplastic FK 800 (labeled as SKF 32, F-32L, Kel-F and FK 800) and an in-house prepared poly(vinylidene fluoride-chlorotrifluoroethylene) (FKM) copolymer were investigated in terms of their thermal degradation kinetics, reaction models and corresponding thermodynamic parameters. All samples underwent a single step thermal degradation using thermogravimetric analysis (TGA) at different heating rates under nitrogen atmosphere. The kinetic parameters were determined through the Kissinger method and three isoconversional methods; viz. the Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Starink. The activation energies of the SKF 32, F-32L, Kel-F, FK 800 and FKM obtained using the Kissinger method were 206, 200, 185, 221 and 243 kJ mol-1 , respectively. The activation energy values for the degradation obtained using the KAS method were: 180-225 kJ mol À1 for SKF 32, 192-209 kJ mol À1 for F-32L, 163-185 kJ mol À1 for Kel-F, 213-227 kJ mol À1 for FK 800 and 187-269 kJ mol À1 for FKM with the extents of conversion (a) ¼ 0.1-0.9. These values of the activation energies obtained from the KAS method were in good agreement with those obtained using the FWO and Starink methods. In addition, the appropriate degradation reaction models were determined by means of the Coats-Redfern and Criado methods. The thermodynamic parameters, such as activation Gibb free energy, DG Ã , activation enthalpy, DH Ã , and activation entropy, DS Ã , for formation of the activated complexes during the thermal degradation were also determined and discussed. The positive values of the E a , DG Ã , DH Ã , and DS Ã for SKF 32, F-32L, FK 800 and FKM indicated a non-spontaneous process, while the positive values of the E a , DG Ã and DH Ã , and negative value of DS Ã for Kel-F meant that the formation of the activated complex was accompanied by a smaller decrease of entropy than for the other polymers.
European Polymer Journal, 2017
Decomposition of poly(vinylidene fluoride-ter-hexafluoropropylene-ter-tetrafluoroethylene) terpolymer, a typical fluoroelastomer with high flexibility and high resistance to permeation of oil and excellent adhesive ability to other materials, in subcritical water (SubCW) was studied as a first example of the decomposition of the terpolymer with the aim of developing a technique to recover the fluorine element. Compared to common fluoropolymer such as poly(vinylidene fluoride), the terpolymer was considerably stable in SubCW. 19 F NMR spectral analysis of the decomposition products obtained from the reaction at 300 o C was carried out to better understand the decomposition mechanism. When the reaction was performed in SubCW at 300 ºC for 6 h under argon, only a negligible amount of Fions (1%) was released. Addition of H 2 O 2 into the reaction system accelerated the mineralization of the terpolymer to form Fand CO 2. Apart from these major products, small amounts of malonic acid and CF 3 H were detected. When this macromolecule was heated in SubCW at 350 ºC with 4.0 M H 2 O 2 , both the yields of Fand CO 2 reached up to 95%. These features indicate a quasi-complete mineralization of the terpolymer. Furthermore, the reaction in the presence of 4.0 M H 2 O 2 and stoichiometric amount of Ca(OH) 2 at 350 ºC for 18 h resulted in the formation of pure CaF 2 , a raw material for hydrofluoric acid, in 84% yield.
Polymer Degradation and Stability, 2003
Three series of linear aromatic copolyimides containing hexafluoro isopropylidine moieties (i.e., 6F) were synthesized by reacting 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) with various mole percents of (a) 1,3-phenylene diamine (mPDA) and 2,6-diamino toluene (DAT) (b) mPDA and 2,4,6-trimethyl-l,3-phenylene diamine (TMemPDA) and (c) DAT and TMemPDA in N-methyl-2-pyrrolidone (NMP). These copolyimides were characterized by inherent viscosity, GPC, DSC, XRD, and TGA. T g increased with increase in TMemPDA content in [6FDA+TMemPDA+mPDA] and [6FDA+TMemPDA+DAT] copolyimides and increase in DAT content in [6FDA+mPDA+DAT] copolyimide series. All the copolyimides were found to be amorphous. Activation energy was determined for the thermal degradation of these copolyimides using the Coats-Redfern equation and was found to follow first-order kinetics in air and nitrogen. CO 2 was the main decomposition product in air and CHF 3 in nitrogen atmosphere.
Pyrolytic degradation of common polymers present in packaging materials
Journal of Thermal Analysis and Calorimetry, 2019
Pyrolysis of polymers with widespread use, such as PET, HDPE, PVC, LDPE, PP and PS, been utilized extensively as plastic packaging materials, is the subject of this study. Low biodegradability and short life of polymers used in packaging have resulted in enormous waste amounts; thus, polymer recycling is more than imperative for modern, developed municipalities. One of the main problems is the production of either feedstock or valuable secondary materials, without additional environmental burden. In this context, the thermochemical methods lead not only to recycling of plastics but also to the creation of specific petrochemical industrial products, and the profit will be considerable. Pyrolizer accompanied by a GC/MS is a useful instrumental array for the study of the thermal degradation of several types of polymers. It is resulted that the cracking temperature affects the type and number of the segments produced, since higher temperatures strongly parcel the polymer chain to monomers and release smaller molecules, while at lower temperatures it is more likely to detect oligomers. Chromatographic results were sometimes complicated due to the isomers produced during pyrolysis. It is mainly supposed that polyolefins decompose through a radical process, where depolymerization propagates until H-abstraction occurs. PVC behaves differently due to the presence of halogens, fond to chain reactions, while for PS the main fragments eluted are styrene monomer, dimmer and trimmer. From PET analysis, it is concluded that the products of decomposition include CO 2 , PhCOOH, PhCOOCH = H 2 and other aromatic vinyl-substitutes, while PET depolymerization is keen on CaO catalysis for lower decomposition temperatures.
Polymer Bulletin, 2017
Poly(vinylidene fluoride-chlorotrifluoroethylene) (poly(VDF-CTFE)) copolymer is a kind of versatile fluoropolymers that can be used as binder for polymer-bonded explosives (PBXs) application. In this work, some of fluoropolymers consisting of VDF and CTFE units such as fluororubber SKF 32, fluoroplastic F-32L, fluoroelastomer KeL-F, fluoroplastic FK 800 and poly(VDF-CTFE) (abbreviated as SKF 32, F-32L, KeL-F, FK 800 and FKM, respectively) synthesized inhouse have been characterized their physicochemical properties by means of gas pycnometer, scanning electron microscope (SEM), energy dispersive X-ray (EDX), organic elemental analyzer, Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) and thermogravimetry (TG). Glass transition temperature, melting point and crystallinity were measured by differential scanning calorimetry (DSC) method. Thermal stability and thermal degradation kinetics were studied using a temperature at the maximum reaction rate (peak) methods, i.e. Ozawa, Kissinger, Starink and Tang from DSC data obtained at four heating rates of 5, 10, 20 and 30°C min-1 under nitrogen atmosphere and thermal stability from TG. The activation energy values calculated by Tang method for the thermal degradation of SKF 32, F-32L, KeL-F, FK 800 and FKM were obtained around 212.8, 204.9, 218.7, 238.8 and 245.5 kJ mol-1 , respectively. These values of the activation energy are in good agreement and consistent with those Ozawa, Kissinger and Starink methods used for kinetic analysis. The thermodynamic parameters such as the activation free energy DG = , activation enthalpy DH = , and activation entropy DS = were also determined and discussed.
Polymer Degradation and Stability, 2011
The thermal decomposition under non-oxidative conditions of a copolymer of vinylidene cyanide (VCN) and 2,2,2-trifluoroethyl methacrylate (MATRIF) was investigated by thermogravimetry (TG) and Pyrolysis-GCeMS. The type and composition of the pyrolytic products and the shape of the TG curve indicate that both the main thermal degradation process, with onset at 368 C, and a minor weight loss at around 222 C are mainly associated with random main-chain scission. The kinetic parameters were determined by means of dynamic and, in the case of the main degradation stage, also isothermal methods. The results obtained from the dynamic methods (Friedman, FlynneWalleOzawa, and Kissinger, respectively) are in good agreement with those obtained from isothermal TG data. The activation energy was in the 177e213 kJ/mol range for the first stage, and 224e295 kJ/mol for the second stage, the highest respective values being determined from the kinetic analysis according to the Kissinger method.
Preparation of tetrafluoroethylene from the pyrolysis of pentafluoropropionate salts
Journal of Fluorine Chemistry, 2017
The use of tetrafluoroethylene (TFE) in academic institutions beyond a few millimoles has often been inhibited by the compound's inherent danger and general lack of commercial availability. On the other hand, TFE is prepared industrially on a rather large scale by a number of major fluorochemical companies via the pyrolysis of chlorodifluoromethane at high temperatures, yielding TFE and HCl. For a few years at The University of Alabama and Clemson University, we have been preparing TFE on a 100 +-gram scale by the pyrolysis under dynamic vacuum of pentafluoropropionate salts, which can be obtained from the neutralization of pentafluoropropionic acid with a M(OH) n (where M = Li, Na, K, and Cs for n = 1 and Mg, Ca, and Ba for n = 2). Additionally, potassium pentafluoropropionate can be prepared from the reaction of potassium trimethylsilanolate and ethyl pentafluoropropionate. The pentafluoropropionate salts and their
Atmospheric Environment, 2018
The gas-phase reaction of Cl atom with 2,2,2-trifluoroethylacrylate (k1), 1,1,1,3,3,3hexafluoroisopropylacrylate (k2), 2,2,2-trifluoroethylmethacrylate (k3) and 1,1,1,3,3,3hexafluoroisopropylmethacrylate (k4), have been investigated at 298 K and 1 atm using the relative method by gas chromatography coupled with flame ionization detection (GC-FID). The values obtained are (in cm 3 molecule-1 s-1): k1(Cl+CH2=CHC(O)OCH2CF3) = (2.410.57) ×10-10 , k2(Cl+CH2=CHC(O)OCH(CF3)2) = (1.390.34) ×10-10 , k3(Cl+CH2=C(CH3)C(O)OCH2CF3) = (2.220.45) ×10-10 , and k4(Cl +CH2=C(CH3)C(O)OCH(CF3)2 = (2.440.52) × 10-10. Products identification studies were performed by solid-phase microextraction (SPME) method, with on-fiber products derivatization using o-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride, coupled with gas chromatography with mass spectrometry detection (GC-MS). Chloroacetone, trifluoroacetaldehyde and formaldehyde were observed as degradation products and a general mechanism is proposed. Additionally, reactivity trends and atmospheric implications are discussed. Significant ozone photochemical potentials (POCP) and acidification potentials lead to local and or regional impact of the esters under study although is expected to a have a minor impact on global warming and climate change.