Kinetic study of radical polymerization. III. Solution polymerization of acrylamide by 1H‐NMR

Solution and radical polymerization of acrylamide in the presence of potassium persulfate in D₂O was investigated up to high conversion by high‐field ¹H‐NMR spectroscopy. The kinetics of reaction was studied according to the data obtained from the corresponding spectra at various times during the polymerization reaction progress. Processing of the data led us to derive the rate equation of this polymerization reaction and determine the reaction order of each component in the rate equation. The order, with respect to initiator, was consistent with the classical kinetic rate equation (0.45), whereas the order with respect to monomer was greater than unity (1.49). The effect of temperature on the polymerization rate was also investigated and the activation energy of 48.4 kJ mol^?1 was obtained over the temperature range of 60–75°C. Also some mechanistic studies were discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2007–2013, 2004     

Kinetic study of the degradation of acrylonitrile–acrylamide copolymers

Differential scanning calorimetry was used to investigate the degradation of acrylonitrile–acrylamide copolymers in air. The apparent activation energy of degradation of the copolymers was calculated with the Kissinger method. The effects of the copolymerization conditions on the apparent activation energy of the copolymers were studied. Increasing the dimethylformamide concentration in the solvent mixture led to a rapid increase in the apparent activation energy of degradation of the acrylonitrile–acrylamide copolymers. The apparent activation energy decreased quickly as the comonomer acrylamide concentration increased, and this change became less prominent as the acrylamide/acrylonitrile weight ratio increased beyond 5/95. The apparent activation energy increased as the copolymerization temperature increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1017–1020, 2005     

Kinetic study of the aqueous free‐radical polymerization of 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid via an online proton nuclear magnetic resonance technique

The free‐radical polymerization of 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) in aqueous media and in the presence of potassium persulfate (KPS) as a thermal initiator was studied. The ¹H‐NMR method was applied to record the reaction data in online gain. The effects of the monomer and initiator concentrations and also the reaction temperature were studied. The order of reaction with respect to the monomer was much greater than unity (1.94). None of the three theories describing an order of reaction higher than unity could predict the AMPS polymerization mechanism in this study. So, a new mechanism is presented. It is suggested that initiation took place through the formation of a complex between the initiator and monomer, and termination occurred not only by a bimolecular reaction but also by a monomolecular reaction. The order with respect to KPS was 0.49; this was consistent with classical kinetic theory. The determined activation energy at the overall rate of reaction was 92.7 kJ mol^?1 K^?1. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Kinetic study of the polymerization of ethyl acrylate in an aqueous nitric acid medium

A kinetic study of the aqueous polymerization of ethyl acrylate (EA) was carried out at 30°C in a dilute nitric acid medium with ammonium ceric nitrate (ACN)–n‐propanol (nPA) and ACN–ethanol as redox initiator systems. The ceric‐ion consumption was first‐order with respect to the ceric‐ion concentration with both initiator systems. The formation of complexes between Ce(IV) and reducing agents was observed. The orders with respect to the Ce(IV), reducing agents, and monomer were evaluated for aqueous polymerizations of EA initiated by Ce(IV)–nPA and Ce(IV)–ethanol redox initiator systems. The overall activation energy for the aqueous polymerization of EA was evaluated in the temperature region of 27–40°C with both initiator systems. A kinetic mechanism for the aqueous polymerization of EA initiated by redox initiator systems is presented. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 218–224, 2006     

Novel Reaction Kinetic Model for Anionic Polyamide‐6

Semi‐adiabatic temperature measurements are recorded and used to define semi‐empirical equations for the simulation and prediction of the anionic polyamide‐6 (APA‐6) reaction kinetics. The resin mixture used has a long infusion window before the reaction starts. The prediction of the induction time and its corresponding initial temperature of reaction is explored. By means of this semi‐empirical approach and an optimised fitting procedure, the reaction kinetics of APA‐6 can successfully be described. The adiabatic polymerisation can be predicted on the basis of an autocatalytic Kamal‐Sourour model for thermoset resins, and the crystallisation can be described using the isothermal crystallisation model.

     

Polyamide solid state polymerization: Evaluation of pertinent kinetic models

Nylon 6,6 resins, in the form of pellets, were solid state polymerized in the temperature range of 160–200°C in a fixed‐bed reactor under flowing nitrogen for times of 0–4 h. The kinetics of the solid state polymerization (SSP) of nylon 6,6 were examined by the evaluation of pertinent rate expressions and the selection of the most suitable one for describing the apparent overall process. The Flory‐theory‐based kinetic models were the most effective both for this study's data and for data previously published on SSP of different polyamides. Accordingly, SSP rate constants and activation energies were derived, and process parameters, such as the temperature and time, were investigated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 671–681, 2005     

Copolymerization of acrylonitrile with methyl vinyl ketone

Methyl vinyl ketone (MVK) was first used to successfully copolymerize with acrylonitrile (AN). This was achieved with azobisisobutyronitrile as the initiator. The kinetics of the copolymerization of AN with MVK were investigated in a H₂O/dimethyl sulfoxide (DMSO) mixture between 50 and 70°C under N₂ atmosphere. The rate of copolymerization was measured. The kinetic equation of the copolymerization system was obtained, and the overall activation energy for the copolymerization system was determined. The values of the monomer apparent reactivity ratios were calculated by the Kelen–Tudos method. In a DMSO‐rich reaction medium (DMSO/H₂O > 80/20), the monomer apparent reactivity ratios were similar to those in the solution polymerization system. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1940–1944, 2006     

Kinetic study of the urethane and urea reactions of isophorone diisocyanate

Kinetic studies of the catalyzed urethane reactions between isophorone diisocyanate (IPDI) and alcohols and of the urea reactions between an isocyanate‐terminated prepolymer [IPDI–PPG2000–IPDI, where PPG2000 is poly(propylene glycol) with a number‐average molecular weight of 2000 g/mol] and water in the bulk state were performed with Fourier transform infrared (FTIR) spectroscopy. Dibutyltin dilaurate was used as the catalyst for the urethane reaction, and various tertiary amines were used as catalysts for the urea reactions. The reactions were followed through the monitoring of the change in the intensity of the absorbance band for NCO stretching at 2270 cm^?1 in the FTIR spectra; the activation parameters were determined through the evaluation of the kinetic data obtained at various temperatures (within the range of 30–60°C). The kinetic data indicated that the catalyzed isocyanate/alcohol and isocyanate/water reactions both followed second‐order kinetics during their initial stages but later followed third‐order kinetics resulting from the autocatalytic effects of hydrogen bonding between the hydroxyl groups and the newly formed urethane and urea groups. Furthermore, activation energies of 64.88 and about 80 kJ/mol for the isocyanate/alcohol and isocyanate/water reactions, respectively, indicated that the urea‐forming reactions were more sensitive to the reaction temperature than the urethane‐forming reactions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Kinetic study of the thermal decomposition of (2‐phenyl‐1,3‐dioxolane‐4‐yl) methyl methacrylate and 2‐hydroxyethyl methacrylate copolymers

The kinetics of nonisothermal decomposition of (2‐phenyl‐1,3‐dioxolane‐4‐yl) methyl methacrylate (PDMMA), 2‐hydroxyethyl methacrylate (HEMA), and vinyl‐pyrrolidone (VPy) copolymers were investigated by thermogravimetry (TG) and differential thermal analysis (DTA). The data indicated that the major weight loss occurs in the range of 270 to 450°C. The decomposition characteristics showed essentially two regimes and varied depending on the temperature and the copolymer composition. The apparent kinetic parameters of the decompositions were estimated from both TG and DTA data by using the alternative calculation methods. The results suggest that the weight loss rates may be represented, depending on the type of sample, by a reaction model of overall order 1.0 to 1.6, with an activation energy of approximately 65–95 kJ mol^?1. The DTA data estimated considerably higher values for the overall activation energies, around 198–240 kJ mol^?1. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1500–1508, 2005     

Evaluation of the cure kinetics of isocyanate reactive hot‐melt adhesives with differential scanning calorimetry

The matrix polymer of reactive hot‐melt adhesive (RHMA) is an isocyanate‐terminated urethane prepolymer based on oligoester or oligoether diols and diisocyanates. In this study, we explored wet cure kinetics with both isothermal and nonisothermal differential scanning calorimetry methods. Second‐order autocatalytic models were successfully used to evaluate the cure process of both oligoester‐ and oligoether‐based RHMAs. The autocatalyzation effect did not to depend on the structure of diols but on the reaction nature of the end isocyanates. The apparent energy of the overall cure reaction was 86.54 and 84.46 kJ/mol, respectively, which was based on nonisothermal DSC results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2708–2713, 2003     

Bulk polymerization of methyl methacrylate initiated by high intensity ultrasonic irradiation and ESR study

High‐intensity ultrasound was used to initiate the bulk polymerization of methyl methacrylate. The polymerization rate varied with the sonication time, the intensity of the ultrasound, and the initiator concentration of poly (methyl methacrylate) in the monomer. Electron spin resonance (ESR) spectra, obtained by the spin trapping technique, testified that free radicals were produced during the sonication process, and the concentration of radicals also changed with the sonication condition. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1731–1735, 2002     

Study on propene polymerization using a novel spherical Ziegler‐Natta catalyst and its kinetics

The effects of the Al/Ti ratio and external donor (ED) on the catalytic activity and kinetics of propene polymerization catalyzed by a spherical Ziegler‐Natta (Z‐N) catalyst were investigated. The preparation conditions of the catalyst play an important role in the polymerization kinetics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3737–3740, 2003     

Grafting emulsion polymerization of glycidyl methacrylate onto leather by chemical initiation systems

The kinetics of the grafting polymerization of glycidyl methacrylate (GMA) onto leather were studied with chemical initiation systems. The results showed that the rate of grafting of GMA onto leather was dependent on different rates in the chemical initiation systems; for ammonium persulfate (AmPS)/acetone sodium bisulfite (ASBS), potassium persulfate (PPS)/ASBS, and sodium persulfate (SPS)/ASBS, the powers were 1.06, 0.48, and 0.43 and 0.63, 0.46, and 0.43, respectively, with respect to the concentration of the emulsifier sodium dodecyl sulfate, whereas the powers were 1.41, 0.70, and 0.81, respectively, with respect to the monomer concentration. The apparent activation energy was calculated for each initiation system and was found to be 180.8, 361.63, and 542.45 kcal for the AmPS/ASBS, PPS/ASBS, and SPS/ASBS systems, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Kinetic study of the free‐radical polymerization of vinyl acetate in the presence of deuterated chloroform by 1H‐NMR spectroscopy

The free‐radical polymerization of vinyl acetate was performed in the presence of deuterated chloroform (CDCl₃) as a chain‐transfer agent (telogen) and 2,2′‐azobisisobutyronitrile as an initiator. The effects of the initiator and solvent concentrations (or equivalent monomer concentration) and the reaction temperature on the reaction kinetics were studied by real‐time ¹H‐NMR spectroscopy. Data obtained from analysis of the ¹H‐NMR spectra were used to calculate some kinetic parameters, such as the initiator decomposition rate constant (k_d), k_p(f/k_t)^1/2 ratio (where k_p is the average rate constant for propagation, f is the initiator efficiency, and k_t is the average rate constant for termination), and transfer constant to CDCl₃ (C). The results show that k_d and k_p(f/k_t)^1/2 changed significantly with the solvent concentration and reaction temperature, whereas they remained almost constant with the initiator concentration. C changed only with the reaction temperature. Attempts were made to explain the dependence of k_p(f/k_t)^1/2 on the solvent concentration. We concluded from the solvent‐independent C values that the solvent did not have any significant effect on the k_p values. As a result, changes in the k_p(f/k_t)^1/2 values with solvent concentration were attributed to the solvent effect on the f and/or k_t values. Individual values of f and k_t were estimated, and we observed that both the f and k_t values were dependent on the solvent (or equivalent monomer) concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Correlation of Arrhenius parameters for UHMWPE synthesis with ethylene solubility characteristics in different polymerization media

The effect of different polymerization media like n‐hexane, cyclohexane, isooctane, n‐decane, toluene, varsol, and light normal paraffin (LNP) on the kinetics of the slurry polymerization of ethylene using a highly active Ziegler Natta (ZN) catalyst for synthesizing UHMWPE was studied. Attempts have been made to determine the solubility of ethylene in the above polymerization media in a very basic manner and to correlate same with the process activation energy based on the Arrhenius plots. The ethylene solubility seemed to depend on the number of carbon atoms in the media, besides other parameters like geometry, dipole moment, etc. It is obvious and well understood that the monomer (ethylene) concentration has a direct bearing on the polymerization kinetics, which influenced the activation energy (Ea) besides other parameters like catalyst/cocatalyst concentration, temperature, etc which were kept constant during the study. The role of the catalyst system in controlling the activation energy was also further exemplified by employing a different ZN catalyst system wherein higher activation energy was observed. This was ascribed to restricted activation pathways for the catalyst under the comparable experimental conditions employed. As soon as better activation pathways for the catalyst were enabled the activation energy dropped down remarkably. The Ea for the synthesis of ultra‐high molecular weight polyethylene (UHMWPE) using traditional MgCl₂ supported Ti catalyst was found to be 5–12 kcal/mol which compared well with the values obtained by other researchers using other similar catalyst systems for different ethylene polymerization processes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Kinetics and Mechanism of Potassium Persulphate/L-Serine Initiated Polymerization of Methylmethacrylate

The polymerization kinetics of methyl methacrylate with K₂S₂O₈/L-serine redox system has been investigated volumetrically at 35±0.1°C under nitrogen atmosphere acidic aqueous medium in DMF/H₂O mixture (50% v/v). The rates of polymerization were measured varying concentrations of the monomer, initiator, L-serine as well as temperature; and it was found to increase with increasing of both temperature and concentrations of monomer, initiator, and L-serine. The overall energy of activation (E _a ) has been calculated to be 29.48 kJ/mol from the Arrhenius plot in temperature range 25–50°C. The molecular weight of the polymer was determined by gel permeation chromatography (GPC). Based on kinetic studies and depending on the results obtained, a suitable reaction mechanism has been suggested and the rates of polymerization found to obey the following equation: V _p [methyl methacrylate]^1.09[L-serine]^1.03[K₂S₂O₈]^0.96.     

Kinetic investigations of trimethylolpropane–diisocyanate reactions

Trimethylolpropane (TMP) is frequently used as a trifunctional branching and chain‐extending agent in polyurethane production. This article deals with the analysis of the reactivities of the three primary hydroxyl groups of TMP during reactions with two exemplary diisocyanates: aromatic diphenylmethane‐4,4′‐diisocyanate and aliphatic m‐tetramethylxylylene diisocyanate. The method of examination is online attenuated total reflection/Fourier transform infrared spectroscopy. With this method, reactions in progress can be monitored simultaneously. It is shown that the addition of an isocyanate (here phenyl isocyanate) to the alcohol affects the rate of subsequent reactions. The higher the substitution degree is, the smaller the rate constant is of the reaction between the remaining free hydroxyl groups and the diisocyanates. This effect is largely determined by the type of diisocyanate. For reactions with very reactive aromatic diisocyanates, steric hindrance plays a significant role. For aliphatic diisocyanates, the substitution shows only minor effects because of the slowly reacting isocyanate groups. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4090–4097, 2006     

Kinetics of polymerization of dimer fatty acids with ethylenediamine

A generally applicable stoichiometric and kinetic model was developed for the polymerization of dimer fatty acids with ethylenediamine. The rate equations were second‐order before 90% conversion and were used between 405 and 475 K. The parameters of the rate equations were determined with nonlinear regression analysis. A comparison of the model predictions and the experimental data showed that the approach was useful in predicting the polymerization kinetics. The equilibrium constant changed from 3.175 to 7.311. The frequency factor and activation energy for the forward rate constant before 90% conversion were 2,716,894 kg mol^?1 min^?1 and 66.7 kJ mol^?1, respectively. The equilibrium constant was independent of the temperature at frequency factor and activation energy values of 74.4 and 9.7 kJ mol^?1, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2504–2513, 2004     

Kinetic analysis of the imidization of poly(styrene‐co‐maleic anhydride) with aniline in the melt

On the basis of the competitive reactions of intermediate poly(styrene‐co‐N‐phenyl maleamic acid) (SNPMA) to produce either poly(styrene‐co‐maleic anhydride) (SMA) or poly(styrene‐co‐N‐phenyl maleimide) (SNPMI), the imidization kinetics of SMA with aniline in the molten state were investigated by a novel approach. The volatiles emitted during the reaction of SNPMA were monitored online with both thermogravimetric analysis and Fourier transform infrared (FTIR) integrated technology. The experimental results directly and definitely indicate that the amidization reaction from SMA to SNPMA in the melt was reversible. Moreover, the kinetic parameters of the competitive reactions of SNPMA in the melt to produce either SMA or SNPMI were determined by FTIR analysis and then compared with those parameters in solution that were obtained in our previous study. It was also implied that the forward ring‐opening reaction of SMA in the melt was nearly instantaneous and that the rates of the competitive reactions of SNPMA to produce either SMA or SNPMI were crucial for the total imidization of SMA. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A kinetic study of novel bimetallic titanocene catalyst for syndiospecific styrene polymerization

A kinetic study of a syndiospecific polymerization was performed with two kinds of catalysts: Cp*Ti(O(C₆H₄)CMe₂(C₆H₄)O)TiCp* [bimetallic system] and Cp*Ti(OMe)₃ [monometallic system]. The purpose of this study was to determine the reasons behind the high activity of a bimetallic catalyst system. The active site structures of the two kinds of catalysts appears to be similar to the cationic Ti [III] species having η⁵‐pentamethylcyclopentadienyl ligand, while the rate of the activation process of the bimetallic catalyst was found to be higher than that of the monometallic catalyst. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007