Acrylonitrile-vinyl Acetate Copolymer Research Articles

Acrylonitrile/vinyl acetate copolymer nanofibers with different vinylacetate content

AbstractIn this study, free radical copolymerization of acrylonitrile (AN)–vinyl acetate (VAc) was performed for five different feed ratio of VAc (wt %) by using ammonium persulfate (APS) in the aqueous medium. The effect of VAc content on the spectrophotometric and thermal properties of AN–VAc copolymers was investigated by Fourier Transform Infrared–Attenuated Total Reflectance spectrophotometer (FTIR–ATR), differential scanning calorimeter (DSC), and thermal gravimetric analyzer (TGA). Thermal stability of homopolymer of AN is improved after being copolymerized. The electrospun P(AN‐co‐VAc) nanofibers were fabricated and the effect of VAc content on the morphologic properties of nanofibers was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The viscosity of the solution had a significant effect on P(AN‐co‐VAc) electrospinning and the nanofiber morphology. The average diameters of P(AN‐co‐VAc) nanofibers decreased 3.4 times with increasing feed ratio of VAc wt %. The P(AN‐co‐VAc) electrospun nanofiber mats, with the feed ratio of 30 wt % VAc, can be used as a nanofiber membrane in filtration and as a carbon nanofiber precursor for energy storage applications due to high surface to volume ratio, high thermal stability, homogeneous, and thinner nanofiber distribution. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

High-flux composite perfluorinated gas separation membranes of Hyflon® AD on a hollow fibre ultrafiltration membrane support

Composite membranes were prepared by coating of perfluorinated copolymer Hyfon® AD60x on a support of hollow fibre ultrafiltration membrane. Two types of polymer were used for the support: a glassy amorphous poly(ether ether ketone) and a crystalline partially oxidized acrylonitrile-vinylacetate copolymer. Hollow fibre membranes were prepared by the dry-wet spinning method. The pure gas transport properties of the uncoated and the coated membranes were studied for oxygen, nitrogen, methane, helium and carbon dioxide. A dense flat membrane was prepared by solvent evaporation for determination of the diffusion coefficient and solubility of various gases in Hyflon.

Use of near-infrared spectrometry in control analyses of acrylic fibre manufacturing processes

Near-infrared (NIR) spectroscopy was used in control analyses for sodium thiocyanate and 90 : 10 (w/w) acrylonitrile–vinyl acetate copolymer in spinning solutions used for manufacturing textile acrylic fibres. NIR spectra were recorded in the transflectance mode, using fibre optics and a ceramic disk as reflecting surface. Partial least-squares regression (PLSR) was used to construct models for both analytes, using the test set for external validation. Second-derivative and standard normal variate (SNV) spectra led to simplified and more robust models than conventional spectra. Two PLS1 models for the individual determination of the analytes and a PLS2 model for their joint simultaneous determination are proposed. The errors obtained for the validation samples were 1.6% for NaSCN and 2.6% for the copolymer. The robustness of the proposed calibration models was confirmed by using them in control analyses of samples manufactured several months after the models were constructed.

Continuous polymerization of acrylonittile in aqueous medium under the condition of low water to monomer ratio. 9. Effect of polymetrization condition and fluid mixing on the molecular weight distribution of acrylonitrile copolymer with vinyl acetate by continuous polymerization in aqueous medium.

In the continuous polymerization for acrylonitrile-vinyl acetate copolymer (93:7 in weight) using persulfate-bisulfite ion initiation system in aqueous medium, effects of polymerization condition and fluid mixing on the molecular weight distribution of the polymer have been studied by simulation using a kinetic model with a continuous reactor. The following results were obtained. 1) Few effect of water/monomer ratio and, bisulfite/persulfate molar ratio were observed on _??_w/_??_n ratio of the polymer. 2) When dimensionless parameter _??_L/2_??_ (L, length of a reactor; _??_, mean velocity of fluid; _??_, mean diffusion coefficient toward direction of flow) was varied from 0 to 20, _??_w/_??_n ratio increased from 2 to approximately 4 as a result of increased conversion, depending on the polymerization conditions. 3) The experimental values of _??_w/_??_n ratio can be explained to some extent from the simulation result described.

On loci of acrylonitrile polymerization with bisulfite‐persulfate initiators under the conditions of low water/monomer ratio

AbstractIn the preparation of acrylonitrile–vinylacetate copolymer (93:7 in weight) by continuous polymerization in aqueous medium using the complete mixing type reactor, the author and co‐workers studied the effects of the water/monomer ratio on polymer properties and polymerization. They reported that the structure of a polymer particle becomes more compact with decreasing water/monomer ratio. This was noted in studying the physical properties of the polymer and the formation of polymer particles in this system. 1,2 Here the author has performed kinetic studies based on the results of polymerization to determine the loci of the polymerization in the range of water/monomer ratio roughly from 1.75 to 4.0. Most of the primary radicals from the initiators attack the monomers in the aqueous phase to form monomer radicals attached to initiator fragments, and most of the monomer radicals grow to form polymer radicals until termination occurs in the aqueous phase. Hence, the loci of polymerization in this system are not the surfaces and inner parts of the polymer particles, the diameters of which are roughly from 20 to 60 μm observed by a microscope, but the aqueous phase excluding these particles.

Molecular weight distribution of the acrylonitrile-vinyl acetate copolymer prepared by redox polymerization.

The molecular weight distributions were estimated for the acrylonitrile-vinyl acetate copolymers (93:7 in weight), which were prepared by continuous polymerization in aqueous medium with the persulfate-bisulfite-ion redox system under the conditions of water/monomer ratio varied in the range from 4 to 1.75 in weight.The molecular weight distributions were evaluated by_??_ratios estimated from viscosity and osmotic measurements, and by_??_ratios estimated from gel permeation chromatography. The molecular weight distributions of these polymers were so broad that_??_ratio varied between 4 and 6. No marked difference was observed in the molecular weight distribution of the polymers prepared under the conditions mentioned above.

Hydrodynamic properties of dilute solutions and the molecular characteristics of copolymers of acrylonitrile with vinyl acetate

The intrinsic viscosities [η] of fractions of the statistical copolymer of acrylonitrile with vinyl acetate in DMFA and the binary solvent DMFA-THF (1 : 1 by volume) have been measured. The method of approximation to sedimentation equilibrium in DMFA has been used to determine the weight average molecular masses M w and the second viraal coefficients A 2 and in DMFA-THF the sedimentation constants S 0. From the values of [η], A 2 and M w the authors calculate the unperturbed dimensions for fractions of different composition; on average, the length of the Kuhn segment is ∼ 25 A ̊ . Some anomalies of the hydrodynamic behaviour of solutions of acrylonitrile-vinyl acetate copolymers are explicable only by taking into account the microstructure of the chains—the stereoregularity of the acrylonitrile blocks and the distribution by the lengths of the sequences of the vinyl acetate units determined by the method of IR spectroscopy.

Water as a melting point depressant for acrylic polymers

Water is known to strongly depress the melting point of polyacrylonitrile (PAN) and acrylic copolymers. A scanning calorimetric technique has been developed that utilizes this melting point depression in probing the structure of acrylic fibers. In this report the melting and crystallization of PAN and acrylonitrile-vinyl acetate copolymers is studied as a function of water content. Addition of water continually depresses the polymer melting point until a critical water level is reached where the molten polymer separates from the water and no further reduction in the melting point is observed. Both the minimum melting point and the critical amount of water required for phase separation decreases as the level of vinyl acetate comonomer is increased. The latter relationships are examined in terms of the acrylic polymer morphology and the possibility that the water molecules become associated with the nitrile group during the melting process.

Compatibility of poly(vinyl chloride) with other polymers

Abstract The compatibility of polyacrylonitrile (PAN) and a few of its copolymers with poly(vinyl chloride) (PVC), has been studied by viscometry, phase separation from a common solvent, and light microscopy methods. We determined the influence of the following parameters on compatibility: temperature, concentration of the polymers in solution, chemical composition of the blends, and the nature of the solvent. The experimental results obtained by the three methods are in good agreement and prove that the PAN/PVC system is not compatible. Among the copolymers studied, it was noticed that acrylonitrilevinyl acetate copolymer induced compatibility of the polymer blend system at some blend compositions.

Glass Transition Temperatures of Regularly Alternating Acrylonitrile-Vinyl Acetate Copolymers

Glass Transition Temperatures of Regularly Alternating Acrylonitrile-Vinyl Acetate Copolymers

The osmometry and viscosity of dilute acrylonitrile-vinyl acetate copolymer solutions in dimethylformamide

The osmometry and viscosity of dilute acrylonitrile-vinyl acetate copolymer solutions in dimethylformamide

The melting of polyacrylonitrile

The melting point of a series of acrylonitrile—vinyl acetate copolymers were measured by differential thermal analysis and the data treated with the Flory relationship for melting-point depression. As a result of this calculation, the melting point of polyacrylonitrile was found to be 322 °C. Additional calculations revealed that the heat of fusion derived from copolymer experiments was about one half the value obtained from diluent studies and that reasonable heats of fusion could be calculated from copolymer melting-point depression experiments if the assumption is made that the effective concentration of the minor component is two times the actual amount present.

A study of spinnability in the wet‐spinning of acrylic fibers

AbstractAn extensive study of spinnability is presented for the formation of acrylic fibers by wet‐spinning. The system consisted of an acrylonitrile–vinyl acetate copolymer with dimethylacetamide as the solvent and water in most instances as the nonsolvent. The term spinnability is used here to denote the type of filament breakage that occurs in the spin bath near the spinnerette face as the withdrawal speed V1 is increased to some critical value. This maximum speed V1, m depends on essentially every spinning variable. Data are presented for a wide range of spinnerette hole diameters, flow rates per hole, coagulation rates, temperatures, and polymer concentration in the spinning solution. The freely extruded velocity of the filaments, Vf, is also given over the same range of variables. The free velocity is much less than the average velocity because of the Barus effect. Some similarities are noted in the response of V1, m and Vf to certain variables. In fact, V1, m seems to be determined by Vf. Through this observation the influence of the Barus effect on spinnability is easily seen. Spinnability is discussed also in terms of coagulation rates. It is concluded that both rheological and coagulation phenomena are important in the breakage mechanism. These observations are probably applicable in part to other wet‐spinning systems.

Reversible gelation of acrylonitrile–vinyl acetate copolymer solutions. II. Mechanical properties

AbstractConcentrated solutions of acrylonitrile polymers exhibit reversible gelation. The rate of gelation at 25°C. was determined for various solutions of an acrylonitrile copolymer containing 7.7% vinyl acetate in mixtures of dimethylacetamide (solvent) and water (nonsolvent) by measuring the shear modulus of the forming gel as a function of time. The mechanical properties were also measured on a series of gels formed by cooling solutions to −78°C. It was found that both the rate of gelation at 25°C. and the modulus of gels formed at −78°C. increase very rapidly as either the solids level of the solution of the water content of the solvent is increased. The gelation rate data wree correlated with the gel melting points of the gels. The results are discussed and compared with the analogous but limited data available for other systems.

Reversible gelation of acrylonitrile–vinyl acetate copolymer solutions

AbstractThe reversible gelation of acrylonitrile–vinyl acetate copolymers in concentrated solutions has been studied with the use of various solvents. These concentrated solutions gel or become rigid with time, but they become fluid again when heated above a certain temperature called the gel melting point. A technique involving the use of mercury drops was developed to measure this transition. This temperature was evaluated as a function of solids level, water content in the solvent, and the amount of vinyl acetate in the copolymer, dimethylacetamide being used as the solvent. Four other solvents were used to obtain limited data. Gel melting was studied further by differential thermal analysis and shear modulus measurements. The results are discussed in terms of network formation and solubility. The x‐ray diffraction results imply that the tie points of the gel are crystalline.

Spectra of nitrone and acrylonitrile-vinyl acetate copolymer in polarized infrared

Spectra of nitrone and acrylonitrile-vinyl acetate copolymer in polarized infrared

The glass temperatures of polyacrylonitrile and acrylonitrile–vinyl acetate copolymers

The glass-transition temperatures Tg of various copolymers of acrylonitrile and vinyl acetate were measured by observing the linear expansion of molded discs. For vinyl acetate contents of 0 to 27 wt-.% the glass temperature is constant at 87°C. This value agrees with the results of Kolb and Izard for pure polyacrylonitrile. Fitting of the glass temperature–composition data above 27% vinyl acetate to the equation of Fox and Loshaek leads to an extrapolated value of 110°C. for completely amorphous polyacrylonitrile, which agrees with similar data of Krigbaum and Tokita. The difference between the two values can be explained in terms of the effects of crystallinity analogous to those discussed by Nielsen for ethylene–vinyl acetate copolymers. Moreover, experimental values of 92 and 103°C. were found for specially prepared samples of polyacrylonitrile. These samples were found to be less crystalline or to have a different ordering of the polymer chains as evidenced by x-ray data. It is concluded that the glass temperature of completely amorphous polyacrylonitrile can be no greater than 110°C. and that experimental values for semicrystalline polyacrylonitrile may range down to 87°C.

Dye-sensitized Photopolymerization of Acrylonitrile-Vinyl Acetate Copolymers

Abstract Copolymers of acrylonitrile and vinyl acetate have been produced using a dye-reducing agent combination as the photo sensitizer. Visible light was employed as the radiation source. Nitrogen analyses were performed on the polymers obtained. The copolymerization ratio were 3.88 and 0.009 for acrylonitrile and vinyl acetate, respectively. Below an initial monomer molar ratio of acrylonitrile of 0.3, the resultant copoly-mer dissolves in acetone.