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 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     

Ultrasonic degradation of solutions of poly(vinyl acetate) in tetrahydrofuran

The ultrasonic degradation of poly(vinyl acetate) (PVAc) solutions was carried out in tetrahydrofuran (THF) at 20, 25, 30, and 35°C to investigate the effects of the temperature and solution concentration on the rate of degradation. The degradation kinetics were studied with viscometry. The calculated rate constants indicated that the degradation rate of the PVAc solutions decreased as the temperature and solution concentration increased. The calculated rate constants were correlated in terms of the concentration, temperature, vapor pressure of THF, and relative viscosity of the PVAc solutions. This degradation behavior was interpreted in terms of the vapor pressure of THF and the viscosity and concentration of the polymer solutions. With increasing temperature, the vapor pressure of the solvent increased, and so the vapor entered the cavitation bubbles during their growth. This caused a reduction in the collapsing shock because of a cushioning effect; therefore, the rate of degradation decreased. As the solution concentration increased, the viscosity increased and caused a reduction in the cavitation efficiency, and so the rate of degradation decreased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2373–2376, 2005     

Modeling of the copolymerization,with depropagation,of α‐methyl styrene and methyl methacrylate at an elevated temperature

We propose a dynamic model for the copolymerization of α‐methyl styrene (α‐MS) and methyl methacrylate (MMA) in a batch reactor. The parameters are based on data from the literature and our own laboratories over the full conversion range. A two‐parameter model with constant reactivity ratios shows the most reasonable results. The dynamic model depicts the reaction kinetics and reactor behavior more clearly. Termination occurs mainly by the cross reaction of unlike radicals, and its rate increases with the molar ratio of α‐MS to MMA. The model enables us to predict the instantaneous and cumulative properties of the copolymer and also provides us with a basic tool for the optimization and control of industrial reactors. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 261–270, 2004     

Thermal degradation kinetics of polyesters containing mesogenic aromatic diols

A series of polyesters were synthesized by reacting structurally differing aromatic diols with either saturated (flexible) or unsaturated (rigid) dicarboxylic acid halide by a stirred interfacial polycondensation technique. Thermal degradation kinetics of these polyesters were investigated by applying Coats–Redfern and Horowitz–Metzger nonisothermal procedures. The dynamic thermogravimetry experiments were conducted in nitrogen to obtain differential thermogravimetric plots. Thermal stability of these polyesters was discussed on the basis of semiquantitative methods such as differential procedural decomposition temperature, integral procedural decomposition temperature, and fraction decomposition temperature (e.g., 10% DT). Degradation proceeded in multiple stages. The thermal degradation patterns and activation energies in these stages were discussed in relation to central bridging moieties of aromatic diol. The activation energies of these polyesters were found to be in the range of 100 to 200 kJ/mol. The effect of spacer type on activation energy was also reported. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 784–792, 2005     

Copolymerization of styrene with N‐phenyl maleimide in the presence of montmorillonite

The copolymerization of styrene with N‐phenyl maleimide in the presence of organomodified montmorillonite or Na⁺ montmorillonite was investigated. The conversion of the monomer was determined dilatometrically or gravimetrically. The copolymerization rate was accelerated and the polymerization activation energy in bulk and solution copolymerization decreased in the presence of montmorillonite. The tendency of alter‐copolymerization was enhanced for bulk and solution polymerization, but not affected for emulsion polymerization, by the addition of organomodified montmorillonite or Na⁺ montmorillonite. X‐ray diffraction studies showed that the methods of emulsion and bulk intercalative polymerization were more appropriate techniques for preparing nanocomposites with good dispersibility of clay. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1932–1937, 2005     

Effect of zeolite filler on the thermal degradation kinetics of polypropylene

In this study, the thermal degradation behavior of polypropylene (PP) and PP–zeolite composites was investigated. Clinoptilolite, a natural zeolitic tuff, was used as the filler material in composites. The effects of both pure clinoptilolite and silver‐ion‐exchanged clinoptilolite on the thermal degradation kinetics of the PP composites was studied with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Polymer degradation was evaluated with DSC at heating rates of 5, 10, and 20°C/min from room temperature to 500°C. The silver concentration (4.36, 27.85, and 183.8 mg of Ag/g of zeolite) was the selected parameter under consideration. From the DSC curves, we observed that the heat of degradation values of the composites containing 2–6% silver‐exchanged zeolite (321–390 kJ/kg) were larger than that of the pure PP (258 kJ/kg). From the DSC results, we confirmed that the PP–zeolite composites can be used at higher temperatures than the pure PP polymer because of its higher thermal stability. The thermal decomposition activation energies of the composites were calculated with both the Kissinger and Ozawa models. The values predicted from these two equations were in close agreement. From the TGA curves, we found that zeolite addition into the PP matrix slowed the decomposition reaction; however, silver‐exchanged zeolite addition into the matrix accelerated the reaction. The higher the silver concentration was, the lower were the thermal decomposition activation energies we obtained. As a result, PP was much more susceptible to thermal decomposition in the presence of silver‐exchanged zeolite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 143–148, 2006     

Kinetics of the enzymatic degradation of poly(vinyl acetate) in solution

The enzymatic degradability of poly(vinyl acetate) was investigated in toluene solutions at various temperatures with hog pancreas lipase. The polymer degraded by specific scission to yield oligomeric products with a molecular weight of 700. Continuous distribution kinetics were used to determine the rate coefficients. The variation of the rate coefficients with the temperature indicated an optimum at 55°C. The p‐toluene sulfonic acid catalyzed degradation of poly(vinyl acetate) was also investigated. The degradation mechanism was random chain scission, and the energy of activation for degradation was determined from the variation of the rate coefficients with the temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2579–2582, 2003     

Reverse atom transfer radical polymerization of acrylonitrile under microwave irradiation

Reverse atom transfer radical polymerization was first used to successfully synthesize polyacrylonitrile under microwave irradiation. FeCl₃, coordinated by isophthalic acid, was used as the catalyst, and 2,2′‐azobisisoheptonitrilewas used as the initiator. N,N‐Dimethylformamide was used as the solvent to improve the solubility of the ligand. Under the same experimental conditions, the apparent rate constant under microwave irradiation was higher than that under conventional heating. The polymerization not only showed the best control of the molecular weight and its distribution but also provided a rather rapid reaction rate with the [acrylonitrile]/[2,2′‐azobisisoheptonitrile]/[FeCl₃]/[isophthalic acid] ratio of 300 : 1 : 1 : 2. The polymers obtained were used as macroinitiators to initiate the chain extension and successfully synthesize acrylonitrile polymers with a molecular weight higher than 50,000 and a narrow polydispersity as low as 1.30. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Cyclization reaction in poly(acrylonitrile/itaconic acid) copolymer: An isothermal differential scanning calorimetry kinetic study

The kinetics of the cyclization reaction in the poly(acrylonitrile/itaconic acid) (PAN) copolymer in the temperature range 175–200°C was studied by isothermal differential scanning calorimetry (DSC). The reaction conforms to an n^th‐order autocatalytic model, with an overall order of 2. The kinetic parameters were derived by multiple regression analysis. The activation energy is 110.3 kJ/mol for the acid‐catalyzed reaction and 153.2 kJ/mol for the autocatalytic part. The autocatalysis indicates the catalysis of the nitrile group cyclization by the initially formed pyrimidine groups. The kinetic parameters were used to predict the reaction profile at a given temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 915–920, 2003     

Kinetics of the thermal degradation and thermal stability of conductive silicone rubber filled with conductive carbon black

The kinetics of the thermal degradation and thermal stability of conductive silicone rubber filled with conductive carbon black was investigated by thermogravimetric analysis in a flowing nitrogen atmosphere at a heating rate of 5°C/min. The rate parameters were evaluated by the method of Freeman–Carroll. The results show that the thermal degradation of conductive silicone rubber begins at about 350°C and ends at about 600°C. The thermal degradation is multistage, in which zero‐order reactions are principal. The kinetics of the thermal degradation of conductive silicone rubber has relevance to its loading of conductive carbon black. The activation energies are temperature‐sensitive and their sensitivity to temperature becomes weak as temperature increases. In addition, the conductive silicone rubber filled with conductive carbon black has better thermal stability than that of silicone rubber without any fillers. Also, conductive silicone rubber filled with conductive carbon black has better thermal stability than that of silicone rubber filled with the same amount of silica. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1548–1554, 2003     

Ultrasonic degradation of poly(acrylic acid)

The ultrasonic degradation of poly(acrylic acid), a water‐soluble polymer, was studied in the presence of persulfates at different temperatures in binary solvent mixtures of methanol and water. The degraded samples were analyzed by gel permeation chromatography for the time evolution of the molecular weight distributions. A continuous distribution kinetics model based on midpoint chain scission was developed, and the degradation rate coefficients were determined. The decline in the rate of degradation of poly(acrylic acid) with increasing temperature and with an increment in the methanol content in the binary solvent mixture of methanol and water was attributed to the increased vapor pressure of the solutions. The experimental data showed an augmentation of the degradation rate of the polymer with increasing oxidizing agent (persulfate) concentrations. Different concentrations of three persulfates—potassium persulfate, ammonium persulfate, and sodium persulfate—were used. It was found that the ratio of the polymer degradation rate coefficient to the dissociation rate constant of the persulfate was constant. This implies that the ultrasonic degradation rate of poly(acrylic acid) can be determined a priori in the presence of any initiator. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polymerization of acrylonitrile using potassium peroxydisulfate as an initiator in the presence of a multisite phase‐transfer catalyst: A kinetic study

In this article, the kinetics and mechanism of the free‐radical polymerization of acrylonitrile (AN) using potassium peroxydisulfate (PDS) as a water‐soluble initiator in the presence of synthesized 1,4‐bis(triethyl methyl ammonium) benzene dichloride (DC‐X) as a phase‐transfer catalyst (PTC) were studied. The polymerization reactions were carried out under inert and unstirred conditions at a constant temperature of 60 ± 1°C in cyclohexane/water biphasic media. The rate of polymerization (R_p) increased with an increase in the concentrations of AN, PTC, and PDS. The order with respect to the monomer, initiator, and PTC was found to be 1.0, 0.5, and 0.5, respectively. R_p was independent of the ionic strength and pH of the medium. However, an increase in the polarity of the solvent slightly increased the R_p value. On the basis of the obtained results, a mechanism is proposed for the polymerization reaction. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis of liquid crystalline polymers from polyethylene terephthalate and 4‐acetoxybenzoic acid: A kinetic study

Liquid crystalline polymers (LCPs) have been synthesized from polyethylene terephthalate (PET) and 4‐acetoxybenzoic acid (OB) through melt step‐growth polymerization. The presence of liquid crystalline texture is first examined using optical polarizing microscopy. The thermal durability of the developed systems is studied through thermogravimetric analysis. The kinetics of the polymerization processes is analyzed. The effectiveness of three catalysts commonly used in polyesterification is investigated. The effect of reaction temperature is also examined. The progress of polycondensation reactions over time takes a nonlinear behavior of slight sigmoidal shape, irrespective of whether or not the reaction is catalyzed. Simple second and third order equations, along with a nonlinear model, are used to determine the kinetic parameters characterizing these reactions. The rate of reaction is enhanced when the reaction temperature is increased. Overall, second‐order kinetics well describes the polymerization reactions when the data set is divided into two regions. Antimony trioxide induces a more visible enhancement to the rate of reaction, compared to zinc acetate and sodium acetate. The presence of a catalyst generally increases the reaction activation energy. This indicates that entropy factors outweigh the increase in activation energy and drive the catalyzed reactions to completion. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Determination of the degradation apparent activation energy of acrylonitrile/acrylic acid copolymers

Acrylonitrile/acrylic acid copolymers were prepared by H₂O/dimethyl formamide suspension polymerization technique. Differential scanning calorimetry was used to investigate the degradation of acrylonitrile/acrylic acid copolymers in air. The apparent activation energy of degradation of the copolymer was calculated with the Kissinger method. Effects of copolymerization conditions on the apparent activation energy of copolymer were studied. It has been found that increasing the dimethyl formamide concentration in the solvent mixture led to a gradual increase (97.3–149.4 kJ mol^?1) in the apparent activation energy of degradation of the acrylonitrile/acrylic acid copolymers. The apparent activation energy decreases with increase in acrylic acid concentration, and this change became less prominent as the acrylic acid/acrylonitrile weight ratio is more than 5/95. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4668–4671, 2006     

Effect of the carboxylic acid monomer type on the emulsifier‐free emulsion copolymerization of styrene and butadiene

Carboxylated styrene–butadiene rubber latexes were prepared through the emulsifier‐free emulsion copolymerization of styrene and butadiene with various carboxylic acid monomers. The effects of various carboxylic acid monomers on the particle formation process were investigated. The type of carboxylic acid monomer strongly affected the particle nucleation. The number of particles and thus the polymerization rate increased with the increasing hydrophobicity of the carboxylic acid monomers. There was a significant difference in the polymerization rate per particle. The results showed that particle nucleation and growth were dependent on the hydrophilic nature of the carboxylic acid monomers. The average particle diameter of the carboxylated styrene–butadiene rubber latexes in the dry state was obtained through some calculations using direct measurements of the average particle diameter in the monomer‐swollen state by a dynamic light scattering technique. Several parameters, such as the polymerization rate, number of latex particles per unit of volume of the aqueous phase, and polymerization rate per particle, were calculated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Development of new concepts for the control of polymerization processes: Multiobjective optimization and decision engineering. II. Application of a Choquet integral to an emulsion copolymerization process

In polymer industry, engineers seek to obtain polymers with prescribed end‐use properties, high productivities, and low cost. Thus, the optimization of a manufacturing process with all those goals and constraints belongs to a problem domain that aims to achieve the best trade‐off possible. This article concerns the optimization of the batch emulsion polymerization of styrene and α‐methylstyrene. An accurate model was developed to describe the complete patterns of the emulsion polymerization. Key parameters of the model were identified on the basis of batch experimental data. The model was then used to simulate, under several operating conditions, the polymerization rate, the overall conversion of monomers, and the number and weight‐average molecular weights. Amulticriteria optimization approach based on an evolutionary algorithm and the concept of dominance from the Pareto frontier theory was used. Last, a decision aid system based on the Choquet integral was proposed to determine the optimal operating conditions with the preferences of the decision maker taken into account. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Isothermal crystallization of metallocene‐based propylene/α‐olefin copolymers

Isothermal crystallization and subsequent melting behavior of two propylene/hexene‐1 copolymers and two propylene/octene‐1 copolymers prepared with metallocene catalyst were investigated. It is found that γ‐modification is predominant in all copolymers. The Avrami exponent shows a weak dependency on comonomer content and comonomer type. At higher crystallization temperatures (T_c) the crystallization rate constant changes more rapidly with T_c and the crystallization half‐time substantially increases. Double melting peaks were also observed at high T_c, which is attributed to the inhomogeneous distribution of comonomer units along the polymer chains and the existence of crystals with different lamellar thicknesses. The equilibrium melting temperatures (T) of the copolymers were obtained by Hoffman–Weeks extrapolation. It was found that the T decreases with increasing comonomer content, but are independent of comonomer type, implying that comonomer units are excluded from the crystal lattice. Dilation of the crystal lattice was also observed, which depends on crystallization, comonomer content, and comonomer type. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 240–247, 2005     

Reactivity ratios and monomer partitioning in the microemulsion copolymerization of vinyl acetate and butyl acrylate

The true monomer reactivity ratios for the vinyl acetate/butyl acrylate system were determined with experimental data from the cumulative copolymer composition at low, intermediate, and high conversions and with the monomer partitioning among the aqueous, microemulsion droplet, and polymer particle phases taken into account. A mixture of sodium dodecyl sulfate and poly(ethylene oxide) (23) dodecyl ether (Brij‐35; 3 : 1 w/w) was used as a stabilizer. Potassium persulfate was used as an initiator. The true values of the monomer reactivity ratios were 0.028 ± 3.2 × 10^?3 for vinyl acetate and 6.219 ± 3.1 × 10^?1 for butyl acrylate, and these were in agreement with those reported in the literature for bulk copolymerizations but differed from values reported for other compartmentalized copolymerizations. Thus, these results indicate that the monomer partitioning and cumulative copolymer composition throughout the reaction have to be duly accounted for in the determination of monomer reactivity ratios in heterogeneous polymerizations. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Kinetic analysis of poly(N‐isopropylacrylamide‐co‐dimethylaminoethyl methacrylate) microgel latex formation

Curves of the conversion and particle size versus the time in the preparation of poly(N‐isopropylacrylamide‐co‐dimethylaminoethyl methacrylate) microgel latices by surfactant‐free emulsion polymerization were measured. The copolymerization reactions were rapid, and their rates increased with the dimethylaminoethyl methacrylate (DMAEMA) concentration in the polymerization recipe. Particle formation occurred by a homogeneous nucleation mechanism, in which DMAEMA helped to colloidally stabilize the primary particles. In addition, a strong dependence of the water‐soluble‐polymer (WSP) formation on the DMAEMA concentration was found, and the DMAEMA content in the WSP was significantly higher than that in the microgel particle. A drastic variation of the crosslinking density within the microgel particle during the polymerization process was found through a comparison of the particle size determined by quasi‐elastic light scattering with that determined by transmission electron microscopy. Finally, on the basis of these results, the mechanism of particle formation in this polymerization process was examined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 839–846, 2004