Degradation kinetics of acrylonitrile/methyl vinyl ketone copolymers

Methyl vinyl ketone (MVK) was first used to successfully copolymerize with acrylonitrile (AN). This was achieved by using azobisisobutyronitrile as the initiator. Differential scanning calorimetry results of the degradation of AN/MVK copolymers in air are presented. The apparent activation energy of degradation of the copolymers was calculated with Kissinger method. Effects of copolymerization conditions on the apparent activation energy of the copolymers were studied. It has been found that increasing dimethyl sulfoxide concentration in the solvent mixture leads to a rapid increase in the degradation apparent activation energy of AN/MVK copolymers. The apparent activation energy decreases quickly along with increase in the comononer MVK concentration, and this change becomes less prominent as the weight ratio of MVK/AN goes beyond 7/93. The apparent activation energy shows a trend of increase as the copolymerization temperature increases. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1386–1390, 2007     

Preparation and characterization of membranes obtained from blends of acrylonitrile copolymers with poly(vinyl alcohol)

New microfiltration and ultrafiltration membranes were obtained using acrylonitrile‐vinyl acetate copolymers in mixture with poly(vinyl alcohol) (PVA). Thus, a blend polymer solution was prepared in dimethylsulfoxide (DMSO) and used to obtain bicomponent polymer membranes by phase inversion. The rheological behavior of the DMSO polymer solutions was, mostly, dilatant at low shear gradients and pseudo plastic with quasi Newtonian tendency at higher gradients. Membranes were characterized by Fourier transform infrared spectrometry (FTIR), optical microscopy, atomic force microscopy, thermal gravimetric analysis‐differential thermal gravimetry, and pure water flux (PWF). FTIR spectra displayed the characteristic bands for acrylonitrile, vinyl acetate, and PVA. The morphology and the porosity can be tailored by the preparation conditions. PVA allows controlling the size of the pores and enables, in principle, to use the resulted membranes as supports for enzyme immobilization. PVA content influences the thermal stability. PWF values depend on the copolymer, on the content in PVA, but also on the coagulation bath composition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41013.     

Orientation and properties of acrylonitrile copolymers

The orientation characteristics and the physical properties of acrylonitrile copolymers are studied as a function of orientation temperature, stretch ratio, and rubber modification content. The mechanical, barrier, and thermal properties are evaluated and discussed with respect to the influence of rubber content on these properties. The data indicate unique differences in the orientation behavior of rigid and rubber-modified copolymers. An explanation of these differences is offered on the basis of microscopy and dynamic mechanical analysis.     

Structure development during dry–jet–wet spinning of acrylonitrile/vinyl acids and acrylonitrile/methyl acrylate copolymers

Dry–jet–wet spinning of three copolymers, poly(acrylonitrile/methyl acrylate), poly(acrylonitrile/methacrylic acid), and poly(acrylonitrile/itaconic acid), was performed with a dimethylformamide/water (60:40 v/v) coagulation bath at different temperatures (10–40°C). The fibers were stretched to different levels (1.1–6×) in boiling water, collapsed, and annealed over a heater plate at 130°C. The effects of the polymer composition, coagulation bath temperature, and draw ratio on the cross‐sectional morphology, structure, and tensile properties are reported. The cross‐sectional shape of the gel fibers underwent a transition from a kidney shape to an oval shape, and macrovoids began to appear at higher temperatures. However, F(AN/IA) gel fibers changed from a kidney shape to an irregular shoe type with a gel network of interconnected polymer fibrils. For F(AN/MAA) gel fibers, the diameter increased from 45 to 67 μm when the coagulation bath temperature was increased from 10 to 40°C, and the denier value decreased from 17.5 to 14.3 den/filament. The strength, modulus, and elongation at break decreased with an increase in the coagulation bath temperature. For F(AN/MAA) fibers coagulated at 10°C in a spin bath, the strength increased from 0.43 to 2.213 g/den, the modulus increased from 27 to 76 g/den, and the density increased from 1.177 to 1.196 g cm^?3 when the gel fibers were drawn to 6×. However, 6× drawn F(AN/MA) fibers had a higher strength (3.1 g/den) and elongation (14.6%) in a 40°C coagulation bath. F(AN/IA) fibers could be drawn only to a draw ratio of 4× instead of the 6× draw ratio for F(AN/MAA) and F(AN/MA) fibers. Therefore, the final F(AN/IA) fibers exhibited poor mechanical properties (tenacity = 0.81 g/den, modulus = 22 g/den, and elongation at break = 8%). The crystallinity did not change significantly (χ_c = 61–63%) with the draw ratio, but the crystal size increased from 22.9 to 43.4 Å and orientation factor from 0.41 to 0.78. The dichroic ratio, measured with Fourier transform infrared, decreased with an increase in the draw ratio, but the sonic modulus and crystalline orientation values increased with an increase in the draw ratio. Thermomechanical data show a maximum physical shrinkage of 51.7% for 6× drawn F(AN/MA) and a minimum physical shrinkage of 30.5% for 4× drawn F(AN/IA) fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 773–787, 2002     

Investigation of the compatibility of butadiene—acrylonitrile copolymers with poly(vinyl chloride)

Various methods were used to study the compatibility of butadiene-acrylonitrile copolymers with poly(vinyl chloride). These blends were investigated by phase contrast microscopy, differential scanning calorimetry and torsion pendulum analysis. We conclude that the copolymers are compatible with poly(vinyl chloride) in all PVC compositions within the range 23–45% acrylonitrile. These blends exhibit a single T_g in the torsion pendulum studies and differential scanning calorimetry studies and follow a Fox expression in the variation of T_g with composition. Experimental densities are also higher than those calculated assuming volume additivity, implying better packing and a negative heat of mixing leading to molecular compatibility.     

Polyelectrolyte properties of acrylonitrile copolymers

Conclusions -- The ternary acrylonitrile—methylacrylate—itaconic acid copolymer can display polyelectrolyte properties in solutions, caused by the ionogenic groups from the itaconic acid.-- The itaconic acid content of the copolymer can be estimated from the magnitude of the polyelectrolyte effect in viscosimetric determination of the inherent viscosity of the copolymer.VNIIPV, Mytishchi. Translated from Khimicheskie Volokna, No. 5, pp. 17–18, September–October, 1992.     

Polyblends. I. Mechanical properties of polyblends of butadiene–acrylonitrile elastomers and copolymers of vinyl stearate and vinyl chloride

Several nitrile rubber elastomers were polyblended, across the composition range, with selected polymeric compositions containing vinyl chloride. The compositions incorporated were (a) bulk poly(vinyl chloride) (PVC); (b) copolymers of vinyl stearate and vinyl chloride containing, respectively, 0.21, 0.36, and 0.47 weight fraction of the vinyl ester; and (c) mixtures containing the same weight fractions of di-2-ethylhexyl phthalate (DOP) with PVC. Mechanical, viscoelastic, optical, and volatility properties were studied on all blends in this first paper. To accurately compare the mechanical properties of polyblends of different systems, a criterion of mechanical equivalence was taken as the observance of similar stresses at break for compositions selected to have identical 100% moduli. Optimum mechanical equivalence, therefore, occurred at the largest ratios of 100% modulus to break stress for all systems compared. Optimum mechanical property equivalence was observed for NBR blends with PVC and for similar blends of both internally and externally plasticized systems containing 0.21 weight fraction of plasticizer. However, considerably more nitrile rubber was needed for PVC blends to acquire the properties of the plasticized systems. Mechanical equivalence was observed, but was not optimum for systems having more plasticizer because tensile strengths were lower. Polyblending with NBR improved the toughness and low-temperature properties of starting vinyl stearate copolymers. Improved toughness was indicated by the expansion of areas under stress–strain curves. Refractive index matching appeared to explain the transparency of the best films and their relative freedom from haze. On heating at 85°C, poly(vinyl chloride) and the copolymer polyblends suffered no volatility loss. Volatility of DOP from the blends was 1.5 times greater than for PVC–DOP mixtures. Because modulus–temperature curves and mechanical T_g values of the filler component shifted with composition, the mechanical behavior of these blends was in harmony with an accepted standard of interdomain compatibility.     

Preparation of fibres from graft copolymers of acrylonitrile and polyvinyl alcohol

Conclusions The possibility of spinning fibres from graft copolymers of polyvinyl alcohol and acryonitrile by the scheme for spinning polyacrylonitrile fibre has been established.It has been shown that spinning solutions can be prepared directly from latexes of the graft copolymers.The suggestion has been made that long side chains in the copolymers participate in formation of supermolecular structural elements and aid in obtaining fibres with adequately high mechanical strength and an increased thermal stability.Translated from Khimicheskie Volokna, No. 1, pp. 13–15, January–February, 1988.     

Thermomechanical properties of fibers from copolymers of acrylonitrile and vinylic monomers

The thermomechanical properties of fibers from copolymers of acrylonitrile and methyl acrylate and acrylic (methacrylic) acid were investigated. The possibility of obtaining fibers with a broad range of shrinkage properties by altering the composition of the copolymer and thus altering the kinetic flexibility of the macromolecules was demonstrated.Translated from Khimicheskie Volokna, No. 4, pp. 15–16, July–August, 1992.     

Graft copolymers from thiolated starch and vinyl monomers

Thiol starches of degree of substitution (D.S.) 0.005–0.162 were prepared by displacing starch tosyloxy groups with xanthate and treating the resulting xanthate esters with either sodium hydroxide or sodium borohydride. Acrylonitrile, styrene, acrylamide, acrylic acid, and dimethylaminoethyl methacrylate were grafted onto the thiol starches with hydrogen peroxide as initiator. The peroxide caused both grafting of monomer and coupling of thiol groups to disulfide. Treating graft copolymers with sodium borohydride regenerated thiol groups from disulfide groups so that the grafting sequence could be repeated. By regenerating the thiol groups and repeating the grafting steps, high add-on and high-frequency starch graft copolymers were prepared. During four grafting sequences, acrylonitrile reacted with D.S. 0.162 thiol starch to give graft copolymers that contained increasing amounts of polyacrylonitrile (46.0–66.5%). Grafting frequency increased from 183 to 71 anhydroglucose units (AGU)/graft, while molecular weights of the grafted chains ranged between 20,000 and 25,200. The final product was hydrolyzed with potassium hydroxide solution to a copolymer, which absorbed up to 400 ml water per gram. Styrene was grafted onto thiol starch to give products containing 34.4–69.5% polystyrene with 986–3520 AGU/graft and having molecular weights of grafted chains between 276,000 and 364,000. Graft copolymers containing 48.9% polyacrylamide, 21.2% poly(acrylic acid), and 77.7% poly(2-methacryloyloxyethyldimethylammonium acetate) were obtained under similar conditions.     

The degradation and prestabilization of acrylonitrile copolymers

The degradation and prestabilization of polyacrylonitrile (PAN) were investigated with differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). The initial temperature, initial loss‐weight temperatures, and loss‐weight were significantly lowered when ammonium itaconate (AIA) was used as comonomer. One exothermal peak of PAN (homopolymer) was shown in the DSC curves, while there were four exothermal peaks of poly(AN‐AIA). FTIR spectra results confirm the degradation process of NH groups. During the heating process, NH groups (3030 cm^?1) were changed into NH (2955 cm^?1) and then NH groups (2920 cm^?1). The dissociated H⁺ could initiate the cyclization reactions of C?N companied with heat released. The effect of ammonia on degradation and prestabilization of PAN was also studied. It was found that ammonia could accelerate prestabilization of acrylic precursors. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Syntheses of block copolymers of 2-methyl-2-oxazoline and aromatic vinyl compounds

Summary Various polymers of aromatic vinyl compounds having haloalkyl groups at the both chain-ends were prepared by terminating the living anionic polymers with 1,2-dichloroethane or 1,4-dibromobutane. Using these polymers as initiators, 2-methyl-2-oxazoline was polymerized to result in the block copolymers.     

Iodine reaction of vinyl acetate-vinyl propionate copolymers,VI, thermochromism of the iodine complex membranes of poly(vinyl acetate) and vinyl acetate-vinyl propionate copolymers

The thermochromism of the iodine complex membranes of poly(vinyl acetate) and vinyl acetate-vinyl propionate copolymers was investigated at the states of different humidity. The complex membranes which were maintained in water and in wet air showed a reversible colour change by a heating-cooling cycle, while the complex membrane in dry air was irreversibly decoloured by heating. The decolouration of the complex membranes occurred quite sharply at a temperature characteristic of each membrane.     

Rheological characterization of styrene acrylonitrile copolymers

The relationship between copolymer composition, molecular weight distribution, and rheological properties of random styrene acrylonitrile copolymers synthesized by radical polymerization in bulk was investigated. From differential scanning calorimetry analysis, glass transition temperature was obtained and increases with the acrylonitrile content. The knowledge of the glass transition is a key factor to compare the different copolymers in an iso‐free volume condition for melt rheology. Owing to time temperature superposition, a large frequencies window ranging from the terminal zone until the glassy plateau can be obtained. Thus, the mechanical spectroscopy was used to estimate the rubbery plateau modulus and the Newtonian viscosity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1316–1321, 2000     

Glass transition temperatures of copolymers from methyl methacrylate,styrene, and acrylonitrile: binary copolymers

By using a new theoretical glass transition temperature (T _g)–composition equation, T _g’s of statistic binary copolymers obtained from MMA, St and AN were investigated in this article. The copolymers were prepared by bulk copolymerization using azo-bis-isobutyronitrile (AIBN) as initiator. The compositions and T _g’s were determined by NMR and DSC, respectively. The monomer reactivity ratios were obtained by nonlinear fitting with Mayo–Lewis equation. Excellent fitting results were obtained when relations of T _g’s of MMA–St, MMA–AN, and St–AN copolymers with their compositions were investigated by using a new equation which assumed additivity of bond stiff energy (Liu et al. J Phys Chem B 112:93–99, 2008). This equation contains mole fractions of triads and T _g’s of corresponding periodic copolymers. Compared with the widely used Johnston equation and Barton equation, the new equation showed its superiority. Meanwhile, T _g’s of the assumed periodic copolymers that have not been acquired were tentatively predicted which may provide useful information.