Novel generalized rate equation for free radical copolymerization

A generalized copolymerization rate equation is proposed. The North equation of copolymerization is a special case that can be derived from the generalized equation. According to the mass balance and charge-transfer complex (CTC) equilibrium equation, the free monomer concentration is differentiated from the feed monomer concentration. The effects on the copolymerization rate (the equilibrium constant, total monomer concentration, homopropagation constants, and reactivity ratios) are quantitatively calculated and discussed. The generalized equation may be applied to not only the systems with the participation of CTC, such as styrene/N-phenylmaleimide (PMI), but also those without the participation of CTC, such as methyl methacrylate/PMI. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2635–2639, 1999     

Study on suspension copolymerization rate of vinyl chloride/N-phenylmaleimide

The copolymerization rate of vinyl chloride(VC)/N-phenylmaleimide (PMI) was investigated. The cross termination constant φ was measured to be 8.3 by using nonlinear least square fitting. The value showed that the cross termination was significant. A model of the copolymerization rate of VC/PMI was obtained. Using the calculated modeling parameters, the effects of temperature and initiator concentration on the copolymerization rate were predicted. The predicted values were in good agreement with the experimental data. Acrylonitrile, a third monomer, was selected to reduce the range of copolymer composition of this system, but it further lowered the copolymerization rate. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2649–2656, 1999     

A transport model for the absorption of mixed solvents in glassy polymer membrane

Transport model for mixed solvents in glassy polymer membrane is rare in literature. In our previous work, a new experimental method has been developed and absorption kinetic curves for two mixed solvent systems (ethanol/1,2-dichloroethane and ethanol/ethyl acetate) in polyurethane (PU) membrane at have been measured. In this work, based on Liu et al.'s transport model for single solvent/polymer membrane system, a transport model for the absorption of mixed solvents in glassy polymer membrane is established. Three model parameters in this model can be obtained by correlating the experimental data of the corresponding single solvent/polymer membrane systems; the other three should be determined by correlating the experimental data of mixed solvents/polymer membrane system. The effect of model parameters on diffusion is studied by numerical simulation. The correlated results agree well with the experimental absorption curves. The model has the ability to predict the transport phenomena of mixed solvents in polymer membrane.     

Free‐radical homo‐ and copolymerization of vinyl acetate and n‐butyl acrylate: Kinetic studies by online 1H NMR kinetic experiments

Free‐radical homo‐ and copolymerization of vinyl acetate (VAc) and n‐butyl acrylate (BA) in benzene‐d₆ were performed by using benzoyl peroxide as an initiator at 70°C. Polymerization kinetic was followed by online ¹H NMR kinetic experiments. Significant drift in the comonomer mixture composition with reaction progress was observed. Reactivity ratios of VAc and BA were calculated by terminal unit model (TUM) as well as by simplified penultimate unit model (PUM) with r_VAc = 0. It was found that copolymer composition can be described well by the TUM. “Lumped” kinetic parameter ( $ k_p .k_t^{ - 0.5} $ ) was estimated from experimental data. A good fitting between the theoretical and experimental drifts in the comonomer mixture and copolymer compositions with reaction progress was observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Intramolecular charge transfer complexes

Summary Radical copolymerization of N-ethyl-3-hydroxymethyl cartbazolyl methacrylate (EHMCM) with methacryloyl--hydroxyethyl-3,5-dinitrobenzoate (DNBM) and acryloyl--hydroxyethyl-3,5-dinitrobenzoate (DNBA), respectively, lead to intramolecular charge transfer complexes (CTC). In the case of EHMCM-DNBA copolymerization, a mechanism involving intermonomeric CTC participation is evidenced.Dedicated to Professor B. Vollmert's 60th anniversary     

A Generalized Rate Model for Free Radical Copolymerizationand Its Simulation

A generalized rate model for free radical copolymerization was proposed. It can be applied not only to the system with the participation of charge-transfer complex (CTC), but also to the system without the participation of CTC. The effects of equillbrlum constant, total monomer concentration, homc-propagation parameters and reactivity ratios on free monomer, CTC, overall rates, and the contribution of CTC were considered in thesimuiatlon. North equation of copolymerization rate as a special case can be derived from the generalized model.     

Intramolecular charge transfer complexes

Summary In chloroform solutions, 2-naphtyl methacrylate (M₁) and picryl methacrylate (M₂) give a charge transfer complex (CTC) having a 11 composition. The CTC plays a decisive part in the radical copolymerization of these monomers. The reactivity ratio values for this system are : r₁₂=30; r_1C= 0.14; r_1C1=0.19; and r_1C2=0.53.The obtained copolymers are intramolecular CTC, and their charge transfer interactions depend on copolymer composition and conformation.     

Kinetic model of wet oxidation of phenol at basic pH using a copper catalyst

Catalytic wet oxidation of phenol employing a commercial copper catalyst has been studied. The pH of the media was maintained in the range 7-8 by using 500 mg/L of sodium bicarbonate as buffer solution. The use of this chemical avoids the copper leaching from the solid catalyst and presents another additional advantage since the organic oxidation intermediates obtained at these basic conditions are far less toxic than phenol. Thus, detoxification of phenolic wastewater is directly linked to the phenol conversion achieved. The kinetic model of the phenol disappearance rate has been discriminated by fitting experimental data. These data have been obtained by feeding a phenol solution of 1000 mg/L to a three phase fixed bed reactor at different catalyst weights to liquid flow rates ratios. Temperature and oxygen pressure were changed in the range from to and from 8 to 16 bar, respectively. The kinetic model proposed is based on a heterogeneous free radical mechanism which takes into account the scavenger effect of the bicarbonate on the phenoxy radicals formed on the catalyst surface by reduction of the active copper sites. A slight positive influence of the temperature, but no effect of the oxygen pressure has been found on the kinetic equation for phenol oxidation, at least in the ranges studied. These facts can be explained by the free radical mechanism proposed. Besides, a linear relationship was found between phenol and TOC disappearance that allows quite an accurate prediction of the mineralization achieved.     

Free radical copolymerization and kinetic treatment of styrene with N-phenylmaleimide

The copolymerization of styrene (M₁) with N-phenylmaleimide (M₂) in chloroform with 2,2′-azobis(isobutyronitrile) as an initiator was investigated. The kinetic parameters, such as reactivity ratios, overall activity energy, and the effect of molar fraction of monomers on the initial copolymerization rate, were determined. The bimolecular termination of the copolymerization was proved. The treatment method proposed by Yoshimura and colleagues was used to estimate quantitatively the contribution of the charge-transfer complex (CTC) and the free monomers in the copolymerization process. The propagation reactivity ratios of CTC and free monomers were calculated by a new method. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1535–1542, 1997     

Reaction network and kinetic modeling of wet oxidation of phenol catalyzed by activated carbon

A detailed kinetic model for the catalytic wet oxidation (CWO) of phenol with a commercial activated carbon as catalyst has been proposed. Experimental data have been obtained under kinetic control at steady state in a three-phase fixed bed reactor with concurrent up flow. The kinetic model is able to predict the appearance and disappearance of phenol and the cyclic organic intermediates formed along the phenol oxidation progress. As some cyclic oxidation intermediates—such as hydroquinone and p-benzoquinone—are two orders of magnitude more toxic than phenol, this detailed model is required to design a CWO process achieving the detoxification of the influent. Influences of oxygen pressure and temperature have been quantified (in the ranges 127- and 3.4-16 bar, respectively). This model also considers the formation of refractory compounds to the CWO (short-chain acids as, i.e., acetic, maleic and formic acids, which are biodegradable). Besides, a constant value of the overall fractional yield for the oxidation of phenol, as target pollutant to CO₂, has been obtained. The discriminated kinetic model fits quite well the experimental data for the whole range of variables used.     

A molecular weight model in vinyl chloride–divinyl monomer suspension copolymerization before the gel point

In this paper, a molecular weight model in the vinyl chloride (VC)–divinyl monomer suspension copolymerization was derived from the mechanism of VC two-phase polymerization, with pseudokinetic constant method and the theory of the moments of chain length distribution. Furthermore, the behavior of average polymerization degree was simulated with the model at varied experimental parameters. The simulation phenomena were discussed in detail. It is concluded that our model can be useful to predict the behavior of DP_w and to look inside the crosslinking mechanism in the VC–divinyl monomer copolymerization. © 1995 John Wiley & Sons, Inc.     

Kinetic-compartmental modelling of potassium-containing cellulose feedstock gasification

Biomass is of growing interest as a secondary energy source and can be converted to fuels with higher energy density especially by pyrolysis or gasification. Understanding the mechanism and the kinetics of biomass pyrolysis (thermal decomposition) and gasification (conversion of organic material to gases) could be the key to the design of industrial devices capable of processing vast amounts of biomass feedstock. In our work real product components obtained in pyrolysis were took into consideration as well as char and oil as lumped components, and the kinetic constants for a biomass model compound (cellulose) pyrolysis and gasification were identified based on a proposed simplified reaction mechanism within a compartment model structure. A laboratory scale reactor was used for the physical experiments containing consecutive fast pyrolysis and gasification stages using alkali metal (K) containing feedstock, which has a significant effect on the cellulose pyrolysis and gasification. The detailed model was implemented in MATLAB/Simulink environment, and the unknown kinetic parameters were identified based on experimental data. The model was validated based on measurement data, and a good agreement was found. Based on the validated first principle model the optimal parameters were determined as 0.15 mL/min steam flow rate, and 4% K content.

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Research on rapid preparation and performance of polymethacrylimide foams

A high‐performance polymethacrylimide (PMI) foam was prepared from the reactive monomers of acrylonitrile (AN) and methacrylic acid (MAA) via ultrasonic combined with thermal initiation radical bulk copolymerization and free heat foaming. The reaction progress of cyano and carboxyl groups were tracked by Fourier transform infrared (FTIR) spectroscopy and X‐ray Photoelectron Spectroscopy, and the results indicated that the imide groups were formed and cyano groups gradually decreased during foaming and thermal treatment. The cell morphologies of the PMI foams were characterized by scanning electron microscopy, and the results showed the PMI foams were consisted of the honeycomb structure. The thermostability of the prepared PMI foam was evaluated by thermogravimetric analysis (TGA), and the results revealed that the PMI foam possessed excellent thermal stability and char forming capability. The mechanical properties of PMI foams were measured by tensile, flexural, and compressive strength, and the responding values for the PMI foams with the density of 32.30 kg m^?3 were 0.71, 0.86, and 1.49 MPa, respectively, which demonstrated the obtained PMI foams presented superior mechanical properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44959.     

苯乙烯与N－苯基马来酰亚胺本体共聚合动力学

研究了Ｎ－苯基马来酰亚胺在苯乙烯中的溶解度和络合性能，以及聚合温度、Ｎ－苯基马来酰亚胺浓度、引发剂种类及浓度、加料方式等因素对共聚合速率的影响，进一步分析和计算该体系的动力学和热力学参数。     

Control of network structure in emulsion crosslinking copolymerization

A kinetic model for network structure development during crosslinking copolymerization of vinyl and divinyl monomer is proposed. The model calculations suggest that polymer networks synthesized by free-radical copolymerization are, in general, inhomogeneous at least on a microscopic scale. By application of the same kinetic parameters as those for bulk polymerizations, it was found that the crosslinking density of the polymers formed in the earlier stages of polymerization is very high in emulsion polymerizations and polymer networks tend to be highly heterogeneous. Homogeneous networks cannot be formed even under Flory's simplifying assumptions for vinyl/divinyl copolymerization in emulsion polymerizations. The present kinetic model can be used to find semi-batch policies to control the network structure, and semi-batch policies were used to illustrate the synthesis of homogeneous polymer networks.     

Reactivity ratios of free monomers and their charge‐transfer complex in the copolymerization of N‐butyl maleimide and styrene

As for the charge‐transfer complex (CTC) formed by N‐butyl maleimide (NMBI) and styrene in chloroform, the complex formation constant was determined by ¹H‐NMR of Hanna–Ashbaugh. The copolymerization of NBMI (NBMI, M₁) and styrene (St, M₂) in chloroform using AIBN as an initiator was investigated. On the basis of the kinetic model proposed by Shan, the reactivity ratios of free monomers and CTC in the copolymerization were calculated to be r₁₂ = 0.0440, r₂₁ = 0.0349, r_1C = 0.00688, r_2C = 0.00476, and the ratios of rate constants were obtained to be k_1C/k₁₂ = 6.40, k_2C/k₂₁ = 7.33. In addition, the copolymer was characterized by IR, ¹H‐NMR, DSC, and TGA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3007–3012, 2002; DOI 10.1002/app.2330