High Acrylonitrile Research Articles

Phase-Separated Structure of NBR/PVC Blends with Different Acrylonitrile Contents Investigated Using STEM-EDS Mapping Analysis.

We investigated the phase-separated structure of nitrile butadiene rubber (NBR)/polyvinyl chloride (PVC) blends with different acrylonitrile (AN) contents in the NBR, using dynamic mechanical analysis measurements and scanning-transmission-electron-microscopy (STEM)-energy-dispersive-X-ray-spectroscopy (EDS) elemental analysis. Two separate sharp tan δ peaks were observed in the blend at the lower AN content of 18.0%, whereas a broad peak was observed in the blends with the higher AN contents of 29.0 and 33.5%, due to the increase in miscibility, as expected from the decrease in the solubility parameter difference with the increasing AN content. The STEM-EDS elemental analysis for the concentration distribution showed that the NBR was mixed in the large PVC domains with a diameter of several micrometers, and the excluded PVC existed around the interface of the domain-matrix phases in the blend with the lower AN content, whereas small domains with a diameter of several tens of nanometers were dispersed in the blend with the higher AN content. The concentration difference in PVC between the PVC domain and the NBR matrix became smaller with increasing miscibility as the AN content increased although the blends contained the same PVC content of 40 wt%.

Coverage-dependent acrylonitrile adsorption and electrochemical reduction kinetics on Pb electrode

Electrochemical dimerization of acrylonitrile (AN) is an environmentally friendly approach to manufacture adiponitrile (ADN), the key raw material of nylon-6,6. Despite its significance in industry, the studies on the mechanism and kinetics of AN conversion on cathode are relatively limited. Herein we investigated the adsorption and electrochemical reduction of AN on Pb electrode under different coverage by the combination of experiments and density function theory (DFT) calculations. Under various reaction conditions, it was observed that when decreasing the bulk concentration of AN, the generation of ADN decreases as expected while that of the saturated propionitrile (PN) increases on the contrary, indicating a coverage-dependent kinetic behavior. Theoretical analysis revealed high AN coverage on Pb surface could inhibit the formation of H and repel the contacting of C=C with active site, both of which is against the generation PN and favorable for ADN. A kinetic model was then developed for the cathodic reaction by taking the impact of temperature, potential and surface coverage into account, which gives good agreement in a wide range of operation conditions.

Adsorptive Removal of Lead Ions in Aqueous Solution by Kapok-Polyacrylonitrile Nanocomposites

Abstract In this study, the naturally hydrophobic kapok fibers were modified with polyacrylonitrile (PAN) to reverse its wetting property for adsorption of lead (Pb) ions in aqueous solution. Increasing the initial amount of the acrylonitrile (AN) monomer in solution resulted in thicker PAN coating on the surface of the kapok fibers after in situ polymerization. Consequently, the static water contact angle of the nanocomposite was reduced to zero. The kapok-PAN nanocomposites were then used for adsorption of lead (Pb) II in aqueous solution. Adsorption capacities for Pb(II) increased from 22.05 to 26.81 mg/g with higher AN concentration. Hydrolysis of the kapok-PAN nanocomposite was performed by immersing in a sodium hydroxide (NaOH) solution, which results to significantly enhanced adsorption of about 78.34 mg/g.

Towards an Understanding of the Reaction Pathways in Propane Ammoxidation Based on the Distribution of Elements at the Active Centers of the M1 Phase of the MoV(Nb,Ta)TeO System

The M1 phase of the MoV(Nb,Ta)TeO system is one of the most effective catalysts for the ammoxidation and selective oxidation of propane to acrylonitrile (AN) and acrylic acid, respectively. The active centers of the M1 phase reside on the ab planes of this crystalline material (i.e., the (001) lattice face). Early on we proposed that the thus located active centers contain all key catalytic elements strategically placed for the conversion of propane to AN. These seven element comprising active centers contain: five metal oxide octahedra (2 V0.325+/Mo0.686+, 1 V0.624+/Mo0.386+, 2Mo0.56+/Mo0.55+) and two Te4+—oxygen sites. In this contribution we analyze the various compositional probabilities of the seven element active centers and their additional eight element surroundings and conclude that there are 32 possible compositional arrangements of this 15 element assembly. From the diverse structural arrangements, diverse catalytic properties can be assigned to the individual sites, leading to diverse propane reaction pathways. We conclude that there are 22% AN forming, 22% propylene, 10% waste and 46% inert sites. After normalization these sites are deemed to lead to the following product yields: 41% AN, 41% propylene and 18% waste. The highest experimentally attained AN yield from propane is 42%, employing M1 phase only, which coincides with the predicted value of a concerted mechanism. Higher AN yields are, however, anticipated, up to a lofty upper limit of 82%, by allowing also for a consecutive mechanism (C3° → C3=→AN). This possibility can be rationalized on the basis of the existence of vicinal C3° → C3=/C3=→AN sites whose presence is plentiful on the catalytically important ab planes of M1. The placement and efficiency of these sites is, however, not perfect; therefore the upper AN yield limit is not realized in practice. Our analysis of the elemental distribution at the active centers and their immediate surroundings provides us with new insights into the relationship between structure and catalytic reaction mechanisms of the M1 phase and might serve as a guide towards a redesign of the M1 composition, so as to attain higher AN yields from propane. It provides a challenging task for the synthetic chemist.

Effect of support materials on Ag catalysts used for acrylonitrile decomposition

The effect of the support material on the Ag-catalyzed decomposition of acrylonitrile (AN) to form N 2 was studied for catalyst systems of Ag-ZSM-5, Ag/Al 2O 3, Ag/TiO 2, Ag/SiO 2, Ag/MgO, and Ag/ZrO 2. Ag/TiO 2 and Ag/SiO 2 exhibited high AN conversion with high N 2 selectivity. X-ray diffraction, ultraviolet–visible spectroscopy, and H 2 temperature-programmed reduction revealed that both metallic and oxidized Ag species were present on TiO 2 and SiO 2. On the basis of diffuse reflectance infrared Fourier transform spectroscopy measurements, NH 3 appeared to be formed by hydrolysis of AN, and this hydrolysis was enhanced by the presence of oxidized Ag species in the catalysts. The high AN decomposition activity was due to the presence of both oxidized and metallic Ag species, which promoted the hydrolysis of AN to form NH 3 and the subsequent oxidation of NH 3 to N 2, respectively.

Morphological and thermal properties of ABS/montmorillonite nanocomposites using two different ABS polymers and four different montmorillonite clays

AbstractABS/Clay nanocomposites were prepared using two ABS with different Acrylonitrile (AN) contents and four montmorillonite clays; a natural clay (CNa+) and three modified clays, Cloisites 10A, 20A, and 30B. The composites were prepared in a twin‐screw extruder. Results were analyzed considering the effect of clay and ABS type, on the clay dispersion, intercalation and exfoliation, as well as on the storage modulus and thermal stability of the nanocomposites. XRD and TEM confirm that when using an ABS with higher AN content (ABS2), a better dispersion and intercalation–exfoliation can be obtained. Cloisites 20A and 30B, respectively the one with greater initial intergallery spacing, but lower polarity and with smaller inter‐gallery spacing but greater polarity, produce the ABS nanocomposites with the greater intergallery spacing. Both ABS polymers have similar storage modulus and Tg and in both cases, the modulus increases with the 4 wt % clay. This increase is greater with the modified clays and slightly greater with the ABS2. Tg, from tan δ, increases very little with the 4 wt % clay, but again, this is slightly greater with ABS2. TGA and flammability tests show that the dispersed clay enhances the thermal stability and that the ABS with higher AN content produces a greater increase in fire retardancy. Tests also show that the better thermal stability and fire retardancy is obtained with the Cloisites 20A or 30B. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 190–200, 2008

Chronic toxicity and oncogenic dose–response effects of lifetime oral acrylonitrile exposure to Fischer 344 rats

Acrylonitrile (AN) was administered in the drinking water for approximately 2 years to groups of 100 male and 100 female Fischer 344 rats at nominal concentrations of 1, 3, 10, 30, and 100 ppm. Two groups, each of 100 males and 100 females, were used as untreated controls. Average daily intake was 0.1, 0.3, 0.8, 2.5 or 8.4 mg AN per kg body weight per day, respectively, for treated male rats and 0.1, 0.4, 1.3, 3.7, or 10.9 mg AN per kg per body weight per day, respectively, for dosed females. Clinical biochemistry, interim necropsies, organ weights and microscopic evaluation of tissues and organs were performed on groups of ten rats per sex per group at months 6, 12, and 18 and at study termination. Females were sacrificed in the 24th month and males were terminated after 26 months of dosing. A consistent decrease in survival, lower body weight and reduced water intake, as well as small reductions in hematological parameters, were observed in both sexes of the 100 ppm group. Elevated numbers of early deaths were observed in groups of males receiving 10 ppm AN and females receiving 30 ppm AN. Organ:body weight ratios at various study intervals were consistently elevated in the high dose group and likely were related to lower body weights. At these same intervals, mean absolute weights were either comparable to controls or only slightly elevated and few changes in weight ratios were seen when organ weights were compared with brain weights. No biochemical changes suggested a treatment-related effect. An increase in urine specific gravity in 100 ppm male rats was reflective of a decrease in liquid intake at this level. The only significant non-neoplastic finding observed histologically was a dose-related increase in hyperplasia/hyperkeratosis in squamous cells of the forestomach in male and female rats given 3 ppm and higher AN. This observation correlated with the induction of treatment-related squamous cell tumors (papillomas and carcinomas) of the forestomach seen primarily in rats at 3 ppm AN and higher. Mammary gland carcinomas were observed only in female groups. Both sexes given 10 ppm AN or more in their drinking water for their lifetime had astrocytomas of the brain/spinal cord and adenomas/carcinomas of the Zymbal's gland.

β-CYCLODEXTRIN REGULATED STEREOREGULARITY AND MOLECULAR WEIGHT IN INCLUSION POLYMERIZATION OF ACRYLONITRILE

Polyacrylonitrile (PAN) polymers were prepared by inclusion polymerization of the monomer using various molar equivalents of β-cyclodextrin (β-CD). Stereoregular (isotactic, atactic and syndiotactic) distributions of the prepared PAN polymers were determined from terminal model Bernoullian statistics using 13C-NMR data. With an increase in acrylonitrile (AN): β-CD ratios, the proportion of isotactic polymers increased. Also, Tg increased along with degradation temperature at higher AN: β-CD ratios. However, molecular weight of the polymers prepared was lower at an AN: β-CD ratio of 10:1, but was found to be larger than the control at an AN: β-CD ratio of 20:1.

Dose dependence of covalent binding of acrylonitrile to tissue protein and globin in rats.

The dose dependence of acrylonitrile (AN) covalent binding to tissue protein, following a single acute exposure over a 100-fold range in dose, was measured. Covalent binding was a linear function of AN dose in the lower dose range (0.02-0.95 mmol AN/kg). The slopes of the dose-response curves indicated that tissues varied by nearly 10-fold in their reactivity with AN. The relative order of covalent binding was as follows: blood > > kidney = liver > forestomach = brain > glandular stomach > > muscle. Similar dose-response behavior was observed for globin total covalent binding and for globin N-(2-cyanoethyl) valine (CEValine) adduct formation. The latter adduct was found to represent only 0.2% of the total AN adduction to globin. Regression of tissue protein binding versus globin total covalent binding or globin CEValine adduct indicated that both globin biomarkers could be used as surrogates to estimate the amount of AN bound to tissue protein. At higher AN doses, above approximately 1 mmol/kg, a sharp break in the covalent binding dose-response curve was observed. This knot value is explained by the nearly complete depletion of liver glutathione and the resultant termination of AN detoxification. The toxicity of AN is known to increase sharply above this dose. The data suggest that a comparison of specific tissue proteins labeled by AN above and below this threshold dose may provide some insight into the mechanism of AN-induced toxicity.

Dose Dependence of Covalent Binding of Acrylonitrile to Tissue Protein and Globin in Rats

LI, J., AND CORBETT, D. (1997). Fundam. Appl. ToxicoL 36, 149-156. The dose dependence of acrylonitrile (AN) covalent binding to tissue protein, following a single acute exposure over a 100-fold range in dose, was measured. Covalent binding was a linear function of AN dose in the lower dose range (0.02-0.95 mmol AN/ kg). The slopes of the dose-response curves indicated that tissues varied by nearly 10-fold in their reactivity with AN. The relative order of covalent binding was as follows: blood S> kidney = liver > forestomach = brain > glandular stomach *> muscle. Similar dose-response behavior was observed for globin total covalent binding and for globin N-(2-cyanoethyl)valine (CEValine) adduct formation. The latter adduct was found to represent only 0.2% of the total AN adduction to globin. Regression of tissue protein binding versus globin total covalent binding or globin CEValine adduct indicated that both globin biomarkers could be used as surrogates to estimate the amount of AN bound to tissue protein. At higher AN doses, above approximately 1 mmol/kg, a sharp break in the covalent binding dose-response curve was observed. This knot value is explained by the nearly complete depletion of liver glutathione and the resultant termination of AN detoxification. The toxicity of AN is known to increase sharply above this dose. The data suggest that a comparison of specific tissue proteins labeled by AN above and below this threshold dose may provide some insight into the mechanism of AN-induced toxicity. O 1997 Soctety of Toxicology. Acrylonitrile (AN) is a vinyl monomer used in the production of synthetic fibers, rubber, and plastics. The estimated production of AN in the United States in 1995 was 3.21 billion pounds, ranking it 40th among manufactured chemicals (Kirschner, 1996).

Characterization of Styrene-Acrylonitrile Copolymers by Size Exclusion Chromatography/Stepwise Gradient Elution—Liquid Precipitation Chromatography

Abstract Styrene-acrylonitrile copolymer having acrylonitrile (AN) content of 19.4% was fractionated first by size exclusion chromatography (SEC) and SEC fractions were then separated by liquid precipitation chromatography (LPC), followed by SEC (SEC-LPC-SEC). LPC was performed by stepwise gradient elution with an octadecylsilane (ODS) silica column and mobile phase of mixtures of n-hexane and chloroform in which the chloroform content in the mobile phase was increased 2% every 5 min. The copolymer was separated by LPC according to both composition and molecular weight (MW); fractions having higher AN content had higher MW. The hyphenated technique of SEC-LPC-SEC gave detailed information in which the first SEC fractions having higher MW had lower AN content. In the same SEC fraction, the LPC fractions having higher MW had higher AN content.

Enthalpic interaction in block copolymer/homopolymer blend systems: morphological studies of solvent-cast films

We report morphological studies of solvent-cast polymer blend films containing a polystyrene/poly(methyl methacrylate) (PS/PMMA) block copolymer with polymers that are miscible with one block copolymer segment, viz. polystyrene (PS), random styrene/acrylonitrile copolymers (SAN) and poly(methyl methacrylate) (PMMA). By utilizing SANs that have four different acrylonitrile (AN) contents, we vary the enthalpic interaction between the SAN copolymer and the block copolymer segments. With polystyrene as the minor constituent, and for a given overall composition ratio and specified molecular weights of the blend components, the morphology of the blends was found to change systematically from dispersed spheres to cylinders, vesicles and lamellae, depending on the strength of the enthalpic interaction between the matrix and the block copolymer segments. Selective staining of the PMMA block at the interphase in blends containing SANs was possible only for SANs of higher AN content. This is interpreted as an indication of interfacial microsegregation of the PMMA block from the SAN matrix as the AN content increases. These morphological changes can be explained by differences in the relative solubility of matrix polymer in the micellar corona, which are controlled by the balance between attractive and repulsive interactions with the miscible and immiscible blocks.

Synthesis of Vinyl Polymer‐Starch Composites to Serve as Size Base Materials

AbstractStarch was polymerized independently with acrylamide, acrylic acid, methacrylic acid and acrylonitrile (AN) using potassium persulphate (K2S2O8) as initiator. The products of the polymerization reaction consisted of free starch, grafted starch, homopolymer and oxidized starch. The ratios of these composite constituents were found to differ considerably depending upon the nature of monomer as evidenced by differences in viscosity curves (amylograph‐viscograph) as well as sizeability of the composites and their ease of removal from cotton yarns during desizing. Also studied was the dependence of the extent of polymerization (grafting and homopolymerization) of AN to starch on K2S2O8 and AN concentrations, polymerization temperature, starch/AN ratio and starch + AN/liquor ratio; and the onset of these factors on the apparent viscosity of the composite obtained thereof. Results indicated that the extent of polymerisation increased by increasing the persulphate concentration to 6 g K2S2O8/100 g starch then levelled off; the same held good for apparent viscosity but the latter decreased upon using concentrations higher than 6 g K2S2O8/100 g starch. While the extent of polymerization increased over a range of 8‐32g AN/100 g starch, apparent viscosity decreased. Raising the polymerization temperature from 30 to 60°C caused significant enhancement in the extent of polymerization but with the certainty that maximum apparent viscosity was attained at 50°C. The extent of polymerization was much favoured at higher AN ratio, but maximum apparent viscosity was attained at starch/AN ratio of 83:17. On the other hand, the extent of polymerization decreased by increasing starch + AN/liquor ratio upto 1:75 then remained almost constant upto a ratio of 1:12.5; meanwhile maximum apparent viscosity was observed at a material/liquor ratio of 1:7.5. The results were interpreted in terms of differences in the magnitude of constituents of the poly (AN) ‐ starch composite and their affinity for and swellability in water.

Mechanism of electrohydrodimerization of acrylonitrile on mercury from aqueous solutions

The electrohydrodimerization (EHD) of acrylonitrile (AN) on mercury from aqueous solutions was examined by a polarographic technique with positive feedback for IR compensation as well as by differential-capacity measurements, with the aim of determining optimal experimental conditions under which the formation of the hydrodimer adiponitrile (ADN) is decidedly favoured over that of the saturated monomer propionitrile (PN). Several tetraalkylammonium cations at low concentrations (≈10 −3 M ) and several supporting electrolytes were employed for this purpose. The best conditions for EHD were attained in aqueous solutions of 1.3 to 1.5 M Na + or Li + citrate containing 10 −3 M dodecylethyldimethylammonium (DEDMA) bromide. Under these conditions a gradual increase in the AN bulk concentration from 10 −2 M to 0.2 M causes a progressive splitting of the single two-electron wave due to PN formation into two consecutive one-electron waves, the first of which is due to ADN formation. Differential-capacity measurements indicate that such a progressive passage from the formation of the saturated monomer to that of the hydrodimer is accompanied by a gradual coadsorption of AN and DEDMA on the electrode surface, which demonstrates that the coupling reaction yielding ADN takes place in the adsorbed state. Mechanisms for PN formation at AN concentrations <10 −2 M and for ADN formation at the higher AN concentrations at which EHD takes place have been proposed.

Mechanism of electrohydrodimerization of acrylonitrile on mercury from aqueous solutions

The electrohydrodimerization (EHD) of acrylonitrile (AN) on mercury from aqueous solutions was examined by a polarographic technique with positive feedback for IR compensation as well as by differential-capacity measurements, with the aim of determining optimal experimental conditions under which the formation of the hydrodimer adiponitrile (ADN) is decidedly favoured over that of the saturated monomer propionitrile (PN). Several tetraalkylammonium cations at low concentrations (≈10 −3 M) and several supporting electrolytes were employed for this purpose. The best conditions for EHD were attained in aqueous solutions of 1.3 to 1.5 M Na + or Li + citrate containing 10 −3 M dodecylethyldimethylammonium (DEDMA) bromide. Under these conditions a gradual increase in the AN bulk concentration from 10 −2 M to 0.2 M causes a progressive splitting of the single two-electron wave due to PN formation into two consecutive one-electron waves, the first of which is due to ADN formation. Differential-capacity measurements indicate that such a progressive passage from the formation of the saturated monomer to that of the hydrodimer is accompanied by a gradual coadsorption of AN and DEDMA on the electrode surface, which demonstrates that the coupling reaction yielding ADN takes place in the adsorbed state. Mechanisms for PN formation at AN concentrations <10 −2 M and for ADN formation at the higher AN concentrations at which EHD takes place have been proposed.

Properties of reverse osmosis membranes prepared from poly(4-vinyl pyridine)-acrylonitrile copolymer and the partially quaternized copolymer

Reverse osmosis membranes were prepared from 4-vinyl pyridine(4VP)-acrylonitrile (AN) copolymers and those partially quaternized. Their salt rejection ( S) and hydraulic water permeability ( K 1) were investigated with regard, to co-polymer composition, the membrane profile by SEM observation, cross-linking quaternization with diiodobutane (DIB) and the method of membrane preparation. S decreased with increasing AN content, but K 1 was closely dependent on water content which had a minimum at about 65% 4VP. The increase in K 1 and water content in a high AN range was caused by the change in the membrane structure from dense to porous one. Quaternization with DIB to a small extent notably improved K 1, up to ten times without significant change in S, and most effectively improved both of the membrane structure and the performance of AN rich copolymer membranes which were the highest in tensile strength among the copolymers. It was found by IR and elemental analysis that DIB charged was nearly completely reacted. The DIB modified membranes were anion exchangeable and more than two-thirds of iodide were exchanged for chloride. The modification reduced the membrane strength, to the least extent in the AN rich copolymers, with increasing DIB due to an increase in water content. The quaternized membranes prepared by surface-treating with DIB gave an essentially similar performance and had a composite structure which held unreacted layer. Monofunctional quaternizing agents merely brought about a poor membrane performance. Water transport through the membranes followed solution-diffusion mechanism for the membranes of volume fraction of water smaller than 0.41. The membranes modified with DIB to a small degree were regarded as tight ionic membranes and able to be treated as a nonionic ones, although they behaved ionically showing a decrease in S with the increasing feed concentration.

Antiplasticization and transition to marked nonlinear viscoelasticity in poly(vinyl chloride)/acrylonitrile–butadiene copolymer blends

A series of PVC/NBR blends with varying acrylonitrile (AN) content in the NBR has been studied in uniaxial tension creep tests. The tests have been carried out at 21.5 ± 0.5°C covering creep times from 10 to 1000 sec. NBR with low AN content, having poor compatibility with PVC, gives the blends with higher compliance and increased time dependence of the compliance. A higher AN content in the NBR gives the blends with the opposite properties when the NBR is added in small amounts. NBR with 40 wt-% AN is found to act as an antiplasticizer giving minimal creep compliance when 7 wt-% NBR is added. The antiplasticization reveals a considerably increased stress level at which the transition from approximatively linear to marked nonlinear viscoelasticity occurs and a decreased stress dependence of the creep compliance in the nonlinear viscoelastic range. Since the antiplasticization is also associated with a suppression of the β-transition mechanism, the results provide a demonstration of the importance of β-mechanism in the stress activated processes responsible for the appearance of nonlinear viscoelasticity in solid polymers.