Pyrolysis and thermo‐oxidative degradation of polycyclopentadiene

Thermal degradation of polycyclopentadiene polymer (PCPD) was investigated by pyrolysis gas chromatography (PGC) in the temperature range of 500–950°C. The nature and composition of the pyrolyzates at various temperatures are presented, and the mechanism of degradation is explained. The activation energy of decomposition (E_a) was obtained from an Arrhenius‐type plot using the concentration of the product ethylene (C₂) at different pyrolysis temperatures and the value was found to be 138 kJ mol⁻¹. Thermo‐oxidative degradation of PCPD in the presence of ammonium perchlorate (AP), the most commonly used oxidizer for polymeric fuel binders, was studied at a pyrolysis temperature of 700°C. The compositions of the products with varying amounts of AP are given, and the exothermicity of oxidative decomposition reactions is evaluated. The energetics of the degradation processes are compared with those of polybutadiene type polymers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 635–641, 2000     

Flammability of polyacrylonitrile and its copolymers II. Thermal behaviour and mechanism of degradation

Homopolymeric polyacrylonitrile and fibre-forming copolymers containing either vinyl acetate or methyl acrylate comonomer have been studied by thermal analysis (DSC, TGA and DTG) at various heating rates (10–100 K min^?1) and under air and nitrogen. Three well-defined pyrolysis stages have been observed which occur over the temperature ranges 250–350°C, 350–550°C and above 550°C. Each stage involves a competition between volatilisation and cyclisation or char-forming reactions which depends on heating rate and the presence or absence of oxygen. The well-established dominance of cyclisation in the 250–350°C temperature range obtained during carbon fibre production from acrylic precursors occurs only at low heating rates. At high heating rates, volatilisation dominates and this explains why acrylic polymers have high flammabilities when heating rapidly. The full pyrolysis mechanism has been semi-quantitatively analysed and the role that comonomers play discussed. This has enabled a fuller understanding of the potential burning behaviour of these polymers to be developed.     

Thermal degradation of new copolymers from pyromellitic anhydride

A series of new copolyimides has been synthesized from pyromellitic anhydride. Copoly(imide esters) and copoly(imide amides) were synthesized from bis(N-methylcarboxychloride)pyromellitimide with diols and amines, respectively. One copoly(imide amine) was obtained from bis(N-allyl)pyromellitimide and piperazine via the Michael reaction. The thermal degradation of the copolymides obtained was studied by direct pyrolysis mass spectrometry. Our results show that a selective β-CH hydrogen transfer reaction occurs in copoly(imide esters) containing 1,3-propyl and 1,6-hexane diols, while an intramolecular ester exchange process takes place in copoly(imide ester) with a neopentylglycol moiety. Copoly(imide amide) containing 1,6-hexane diamine decomposes by an N-H hydrogen transfer process, although extensive crosslinking is observed, while that containing piperazine decomposes by an -CH hydrogen transfer. In contrast, copoly(imide amine) undergoes a very selective depolymerization process, yielding bis(N-allyl)pyromellitimide and piperazine.     

Thermal degradation of ethylene–carbon monoxide alternating copolymer under inert atmosphere

This work aims to understand the mechanism of the thermal degradation of the ethylene–carbon monoxide (E-CO) alternating copolymer under mild conditions. The copolymer was subjected to accelerated ageing in an oven at different temperatures below the copolymer melting point, under argon atmosphere, and in the absence of light. The properties of the aged samples were compared with the properties of the untreated copolymer. Untreated and aged samples were analysed by mass spectroscopy (MS) with the direct introduction probe (DIP) and pyrolysis (Py) techniques. The accelerated ageing experiments showed that the thermal degradation of the E-CO alternating copolymer under inert atmosphere is characterized by chain cross-linking, loss of water, and changes in the UV absorption spectrum. The IR spectrum shows modifications only for highly degraded samples in which O−H and C=C groups are present. The experiments performed with the DIP-MS technique have confirmed that the E-CO alternating copolymer loses water during its thermal ageing. The pyrolysis products of the copolymer are linear molecules with 1,4-diketonic structure, 2-cyclopentenone derivatives, alkyl furans, and aromatic compounds. These results suggest that during the thermal degradation of the E-CO alternating copolymer under inert atmosphere, and at low temperatures, aldol condensations and/or dehydration to furan rings probably occur. © 1998 SCI.     

Kinetic investigation of thermooxidative degradation of poly(vinyl chloride)/acrylonitrile–butadiene–styrene blends by isothermal thermogravimetric analysis

The thermal degradation of poly(vinyl chloride)/acrylonitrile–butadiene–styrene (PVC/ABS) blends of different compositions was investigated by means of isothermal thermogravimetric analysis at temperatures of 210°–240°C in flowing atmosphere of air. The Flynn equation, the method of stationary point, and kinetic equation using the Prout–Tompkins model proved to be satisfactory in describing the thermooxidative degradation in the range of 5–30% conversions. The apparent activation energy E and preexponential factor Z were calculated for all compositions of PVC/ABS blends. The ratios E/ln Z are constant for pure and modified PVC and point to the unique mechanism of degradation process. Upon increasing the ratio of ABS in the PVC/ABS blend up to 50%, only the rate of the process is changed; the mechanism remains unchanged. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 833–839, 1999     

Thermal degradation of Kevlar fiber by high‐resolution thermogravimetry

A novel high‐resolution thermogravimetry (TG) technique in a variable heating rate mode that maximizes resolution and minimizes the time required for TG experiments has been performed for evaluating the thermal degradation and its kinetics of Kevlar fiber in the temperature range ∼ 25–900°C. The degradation of Kevlar in nitrogen or air occurs in one step. The decomposition rate and char yield at 900°C are higher in air than in nitrogen, but the degradation temperature is higher in nitrogen than in air. The initial degradation temperature and maximal degradation rate for Kevlar are 520°C and 8.2%/min in air and 530°C and 3.5%/min in nitrogen. The different techniques for calculating the kinetic parameters are compared. The respective activation energy, order, and natural logarithm of preexponential factor of the degradation of Kevlar are achieved at average values of 133 kJ/mol (or 154 kJ/mol), 0.7 (or 1.1), and 16 min⁻¹ (or 20 min⁻¹) in air (or nitrogen). The technique based on the principle that the maximum weight loss rate is observed at the minimum heating rate gives thermal degradation results that were in excellent agreement with values determined by traditional TG experiments. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 565–571, 1999     

Polymer pyrolysis: A resolution of anomalies in kinetic schemes for the rate of evolution of volatile products

Kinetic schemes proposed by three groups of workers for polymer pyrolysis have been critically examined, in order to resolve apparent anomalies, especially in the way in which the overall first-order rate constant for volatile evolution by depropagation mechanisms, involving different modes of initiation and termination, have been interpreted. In one scheme, the treatment of rate was found to be inappropriate for changing-volume systems, and the resulting rate expressions therefore cannot be recommended. When choice of units, conventions, and symbols was taken into account, the other schemes were found to be totally compatible. These schemes lead to identical expressions for the initial rate of evolution of a volatile product, provided the symbols are defined specifically according to the conventions chosen. These expressions are to be recommended for studies of this kind.     

Kinetic parameters of thermal degradation of polyethylene glycol‐toughened novolac‐type phenolic resin

The miscibility and thermal degradation of poly(ethylene glycol) (PEG)‐toughened novolac‐type phenolic resin were investigated. Differential scanning calorimetry (DSC) results confirmed that the phenolic resin/PEG blend was blended completely. Infrared spectra show that hydrogen bonding existed in the blends. Thermal degradation of PEG blended with novolac‐type phenolic resin was studied utilizing a dynamic thermogravimetric technique in a flowing nitrogen atmosphere at several heating rates (i.e., 5, 10, 20, 40°C/min). Thermal degradation of phenolic resin/PEG blends takes place in multiple steps. The thermal behavior and the thermal stability affected the thermal degradation, which coincided with the data from the thermal degradation of novolac‐type phenolic resin/PEG blends by thermogravimetric analysis (TGA). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 188–196, 2001     

An old kinetic method for a new polymerization mechanism: Toward photochemically mediated ATRP

With the idea of “an old method for a new mechanism,” a detailed kinetic insight into photochemically mediated atom‐transfer radical polymerization (photo ATRP) was presented through a validated comprehensive model. The simulation mimics the experimental results of the model system using optimized photochemically mediated radical generation rate coefficients. The activator and radical (re)generated from the photo mediated reactions endow the photo ATRP with unique features, such as rapid ATRP equilibrium and quick consumption of initiator with a small amount of residual. The effect of the reaction parameters on ATRP behaviors was also investigated. Results showed that the acceleration of polymerization rate follows the square root law in the following three cases: the overall photochemically mediated radical generation rate coefficients (k_r), the free ligand concentration, and the initiator concentration. However, the independence of the apparent propagation rate coefficient ( ) on the square root of catalyst concentration might be attributed to the result of the synergy between the activators regenerated by electron‐transfer ATRP and the initiators for continuous activator regeneration ATRP mechanism. The photo ATRP is able to design and prepare various polymers by carefully tuning the conditions using the model‐based optimization approach. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1947–1958, 2015     

PY‐GC/MS an effective technique to characterizing of degradation mechanism of poly (L‐lactide) in the different environment

The biotic and abiotic degradation of poly (L‐lactide) (PLLA) has been studied with pyrolysis gas chromatography mass spectrometry (Py‐GC‐MS). A mixed culture of compost micro‐organisms was used as the biotic medium. Size‐exclusion chromatography (SEC), gas chromatography‐mass spectrometry (GC‐MS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were utilized to monitor the degradation and degradation mechanism. Differences in pH, molecular weight, surface structure, and degradation mechanisms were noted between sample aged in biotic and abiotic medium. Using fractionated Py‐GC‐MS at 400 and 500°C, acetaldehyde, acrylic acid, lactoyl acrylic acid, two lactide isomers, and cyclic oligomers up to the pentamer were identified as thermal decomposition products of PLA as well as some other not completely identified products. The ratio of meso‐lactide to L‐lactide was lower in the sample aged in the biotic media than the abiotic media. This is a result of the preference of the micro‐organisms for L‐form of lactic acid and lactoyl lactic acid rather than the D‐form that in turn influences the formation and the amounts of meso and D,L‐lactide during the pyrolysis. Based on SEM micrographs, it was shown that degradation in the biotic medium proceeded mainly via a surface erosion mechanism, whereas bulk erosion was the predominant degradation mechanism in the abiotic medium. The SEC and Py‐GC‐MS data indicate that degradation was faster in the biotic than in the abiotic sample. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2369–2378, 2000     

Theoretical evaluation and the effect of thermal degradation on the Time–Temperature–Transformation (TTT) diagram of bisphenol A epoxies

A brief discussion about the Time–Temperature–Transformation (TTT) diagram is presented. Using diamino diphenylsulfone‐cured diglycidyl bisphenol A as a representative example, its TTT diagram is completed by including the thermal degradation. The theoretical diagram as obtained from the kinetics of curing and thermal degradation is compared with experimental data. The agreement is good, slight deviations are observed only in the time to vitrify above 150°C and the maximum available glass temperature, which is due to side reactions and onset of thermal degradation during curing. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3894–3896, 2003     

Thermal degradation of liquid polysulfide polymers: Pyrolysis–GC–MS and thermogravimetric studies

The thermal decomposition of Thioped, a liquid polysulfide polymer based on dichloroethyl formal, was studied using pyrolysis–GC–MS. The nature and composition of the products of pyrolysis at 358 and 485°C are given. A striking feature of the product analysis is the presence of several disulfide compounds only at the higher decomposition temperature. The pyrolysis-GC of other liquid polysulfide polymers (LP-2, LP-32, LP-3, and LP-33) showed that molecular weight had only marginal effect on the product composition. Ionic and radical mechanisms were considered to account for the product formation. Isothermal and dynamic thermogravimetric studies were carried out to differentiate between the two mechanisms. The results were found to be in agreement with a free radical mechanism, with cleavage of the formal C? O linkage as the preferred mode of initiation. The overall activation energy for the decomposition was found to be 190 kJ mol^?1.     

Biological degradation of EDTA: Reaction kinetics and technical approach

The microbial mineralization of EDTA in waste water by a mixed culture was studied with suspended and immobilized cells. Efficient degradation of EDTA could be achieved, though the chelator is stated not to be biodegradable. A complete set of kinetic parameters was determined that enables the modelling of EDTA degradation and, related to this, bacterial growth, ammonium release, maintenance requirement as well as oxygen uptake. In order to obtain important technical scale-up parameters, the microorganisms were immobilized on different carrier particles and employed in continuously operated three-phase airlift-loop reactors. The reactors could be operated at a dilution rate up to D=1·2 h⁻¹ (D≪μ_max) that, at an EDTA concentration of 450 mg dm⁻³, led to EDTA degradation rates up to 12·8 kg m⁻³ day⁻¹. The extent of EDTA deg-radation remained constant at 95–99% with increasing values of D. Achieved kinetic parameters of the biofilm systems were compared with those which were obtained from experiments with suspended cells. © 1998 Society of Chemical Industry     

Kinetic effects of selenium on degradation of ethylene–propylene copolymer

The antioxidation protection of elementary selenium added to an ethylene–propylene copolymer (EPR) at different concentrations (0.1, 0.2, and 0.5 phr) was studied. Oxygen uptake measurements were isothermally performed at 180°C on polymer samples stabilized with increasing concentrations of Se. Experimental data have revealed the enhancement in induction periods and the decrease in oxidation rates for unaged elastomer samples. Stabilized polymer specimens exposed to γ‐radiation have presented the highest effects at 0.5 phr of selenium concentration for all irradiation doses (50, 100, 150, and 250 kGy). Influence of selenium on the competition between crosslinking and oxidation occurred in γ‐irradiated ethylene–propylene elastomers discussed on the basis of kinetic treatment on studied thermal degradation process. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2053–2057, 2001     

Superstructure optimization of integrated fast pyrolysis‐gasification for production of liquid fuels and propylene

Motivated by the apparent advantages of fast pyrolysis and gasification, a novel integrated biorefinery plant is systematically synthesized for coproducing premium quality liquid fuels and propylene. The required heat and fluidization promotion of the fast pyrolyzer are provided by hot syngas from the gasifier. Light gas and syngas from the fast pyrolyzer are finally converted to hydrocarbons via Fischer‐Tropsch synthesis. Multiple syngas production technologies, hydrocarbon production and downstream upgrading routes are incorporated within a superstructure optimization based process synthesis framework. This is the first article to investigate the benefits associated with the introduction of conventional catalytic cracking and dewaxing from a systems engineering perspective. Surrogate models describing the gasifiers and rigorous equations for Fischer‐Tropsch effluents validated by our experimental collaborator are introduced. Through investigation of five scenarios the primary parameters affecting overall economic performance are identified through ranking of the relevant candidates. Comparisons of the hybrid conversion route and stand‐alone routes are made. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3155–3176, 2016     

Thermal analysis in the evaluation of compost stability: a comparison with humification parameters

Characterization of organic matter of six composts from agroindustrial wastes was carried out by both chemical analysis and thermal analysis in order to assess their level of stability. Degree of humification (DH%) and index of humification (HI) were calculated after extraction, fractionation and analysis of the organic carbon from composts. Differential Scanning Calorimetry (DSC) and thermogravimetry (TG) were simultaneously performed in oxidizing conditions on whole ground composts. Thermoanalitical data resulted to be useful in integrating quantitative information coming from chemical analysis of humified fraction of compost organic matter. Particularly, DSC curves allow to distinguish between well and poor stabilized composts, and information deriving from weight losses, registered by TG curves, permits to individuate a thermoanalytical parameter (R1) that resulted to be well correlated to humification parameters DH% and HI.     

Synthesis,characterization and thermal degradation of poly[2‐(3‐p‐bromophenyl‐3‐methylcyclobutyl)‐2‐hydroxyethylmethacrylate]

In this work, 2‐(3‐p‐bromophenyl‐3‐methylcyclobutyl)‐2‐hydroxyethylmethacrylate (BPHEMA) [monomer] was synthesized by the addition of methacrylic acid to 1‐epoxyethyl‐3‐bromophenyl‐3‐methyl cyclobutane. The monomer and poly(BPHEMA) were characterized by FT‐IR and [¹H] and [¹³C]NMR. Average molecular weight, glass transition temperature, solubility parameter, and density of the polymer were also determined. Thermal degradation of poly[BPHEMA] was studied by thermogravimetry (TG), FT‐IR. Programmed heating was carried out at 10 °C min⁻¹ from room temperature to 500 °C. The partially degraded polymer was examined by FT‐IR spectroscopy. The degradation products were identified by using FT‐IR, [¹H] and [¹³C]NMR and GC‐MS techniques. Depolymerization is the main reaction in thermal degradation of the polymer up to about 300 °C. Percentage of the monomer in CRF (Cold Ring Fraction) was estimated at 33% in the peak area of the GC curve. Intramolecular cyclization and cyclic anhydride type structures were observed at temperatures above 300 °C. The liquid products of the degradation, formation of anhydride ring structures and mechanism of degradation are discussed. © 1999 Society of Chemical Industry     

Fenton‐like degradation of rhodamine B over highly durable Cu‐embedded alumina: Kinetics and mechanism

Cu‐embedded mesoporous alumina, as a Fenton‐like catalyst prepared via a sol‐gel method, showed excellent activity and durability for the degradation of refectory compounds. The origin of active sites for the generation of hydroxyl radicals (?OH) were thoroughly studied using multitechniques. Cu, as the only active element, could be penetrated into the bulk of alumina and some Cu atoms were embedded into the framework. The dynamic structure of surface Cu species (the variety of Cu⁺/Cu²⁺ ratio) during the reaction were determined as well. Furthermore, the structure plasticity of catalyst has proved by optimizing preparation and reaction conditions. A 98.53% degradation of RhB was recorded within 30 min, following a pseudo‐first‐order reaction rate expression. Electron spin resonance spectra and ?OH scavenging experiments have confirmed that ?OH is the main reactive oxidant for the elimination of RhB. By the surface‐enhanced Raman spectroscopy and gas chromatography‐mass spectrometer results, plausible pathways of RhB degradation were elaborated. © 2017 American Institute of Chemical Engineers AIChE J, 64: 538–549, 2018     

Verification of Eulerian–Eulerian and Eulerian–Lagrangian simulations for turbulent fluid–particle flows

We present a verification study of three simulation techniques for fluid–particle flows, including an Euler–Lagrange approach (EL) inspired by Jackson's seminal work on fluidized particles, a quadrature–based moment method based on the anisotropic Gaussian closure (AG), and the traditional two‐fluid model. We perform simulations of two problems: particles in frozen homogeneous isotropic turbulence (HIT) and cluster‐induced turbulence (CIT). For verification, we evaluate various techniques for extracting statistics from EL and study the convergence properties of the three methods under grid refinement. The convergence is found to depend on the simulation method and on the problem, with CIT simulations posing fewer difficulties than HIT. Specifically, EL converges under refinement for both HIT and CIT, but statistics exhibit dependence on the postprocessing parameters. For CIT, AG produces similar results to EL. For HIT, converging both TFM and AG poses challenges. Overall, extracting converged, parameter‐independent Eulerian statistics remains a challenge for all methods. © 2017 American Institute of Chemical Engineers AIChE J, 63: 5396–5412, 2017