Chemical modification of jute fibers. II: A study on the Fe2+/H2O2-initiated graft copolymerization of methyl methacrylate,acrylonitrile, and acrylamide onto jute fibers

The study of graft copolymerization of methyl methacrylate, acrylonitrile, and acrylamide onto both defatted and bleached jute fibers using the ferrous ammonium sulfate / H₂O₂ redox initiator system has been made. To determine the optimum conditions of grafting, the effects of concentrations of ferrous ammonium sulfate, monomer, H₂O₂; time and temperature on percentage of graft yield have been studied. Acrylamide was found to graft onto the fiber only at a fixed ferrous ammonium ion concentration (5 × 10^?4M). Kinetic studies showed that the rates of grafting follow the second-order mechanism. The activation energies of the reactions were found to be 3.351 and 2.53 kcal/mol in the methyl methacrylate and acrylonitrile systems, respectively. The grafted fibers have been characterized by thermogravimetric analysis, IR spectroscopy, and XRD studies.     

Preparation and evaluation of the chitin derivatives for wastewater treatments

The chitin thiocarbonate—Fe(II)H—H₂O₂ redox system was investigated as the initiator for the graft copolymerization of acrylonitrile and acrylic acid monomers onto chitin powder. The reaction with vinyl monomers onto chitin was carried out under various parameters of the graft copolymerization reaction to elucidate the polymerization behavior in terms of graft yield. Reactions of chitin—acrylonitrile graft copolymer with hydroxyl amine hydrochloride, as well as, sodium hydroxide were conducted in order to obtain chitin—(amidoxime-co-acrylonitrile) and chitin-(acrylate-co-acrylamide) graft copolymers, respectively. The reaction efficiency depends upon the alkali concentration, time, temperature, and on the reactant concentrations. The prepared chitin derivatives were evaluated for use in the wastewater treatments for adsorption and desorption of heavy metal ions as well as acid and basic dyes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1939–1946, 1997     

Synthesis and characterization of polyacrylonitrile pregelled starch graft copolymers using ferrous sulfate‐hydrogen peroxide redox initiation system as surface sizing agent

A graft copolymer was synthesized by graft copolymerization of starch with styrene (St) and butyl acrylate (BA), using ferrous sulfate‐hydrogen peroxide redox initiation system. The starch was pregelled in the presence of acrylonitrile (AN) in aqueous alkali at high temperature before graft polymerization. Major factors affecting the polymerization reaction were investigated. It was found that a graft copolymer with higher percentage conversion (PC), graft efficiency (GE) and graft percentage (GP) was obtained by controlling the initiator concentration, concentration, and ratio of monomers and polymerization temperature. The optimum conditions were as follows: H₂O₂ concentration, 12%; monomer concentration, 120%; St/BA ratio, 1 : 1; polymerization temperature, 65°C. Fourier transform infrared spectroscopy and NMR analyses were used to gain information on the structure of the products. It was demonstrated that St, BA, and AN had been successfully grafted onto starch and ? CN had been saponified into ? CONH₂ and ? COO^? to a certain degree when pregelling. Scanning electron microscope micrographs showed the coarse structure and broad network. The graft polymerization took place on the surface of starch granule and led to amorphization of the starch structure. Graft polymer had better thermal stability and was endowed with pseudo‐plasticity. It was observed that the starch graft copolymer offers good properties such as water resistance as surface‐sizing agent. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Graft copolymerization of methyl methacrylate onto rubber‐wood fiber using H2O2 and Fe2+ as an initiator system

Methyl methacrylate (MMA) was successfully grafted onto rubber‐wood fiber in a free‐radical solution polymerization initiated by ferrous ion and hydrogen peroxide. The effects of the reaction parameters (reaction temperature, reaction period, influence of hydrogen peroxide, ferrous ammonium sulfate, and monomer concentrations) were investigated. The grafting percentage showed dependency on H₂O₂, Fe²⁺, and monomer concentrations, as well as reaction temperature and reaction period. The optimum reaction temperature was determined to be about 60°C and the reaction period was 60 min. The optimum concentration of H₂O₂ was 0.03M and optimum amounts of Fe²⁺ and MMA were 0.26 mmol and 2.36 × 10^?2 mol, respectively. Poly(methyl methacrylate) (PMMA) homopolymer was removed from the graft copolymer by Soxhlet extractor using acetone. The presence of PMMA on the fiber was shown by FT‐IR spectroscopy and gravimetric analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2499–2503, 2003     

Grafting onto wool. XX. Graft copolymerization of vinyl monomers by use of redox initiators. Comparison of monomer reactivities

Methyl methacrylate (MMA) and ethylacrylate (EA) have been graft copolymerized onto Himachali wool in aqueous medium by using a ferrous ammonium sulfate–hydrogen peroxide (FAS? H₂O₂) system as redox initiator. Percentage of grafting has been determined as functions of concentration of monomer, molar ratio of [FAS]/[H₂O₂], time and temperature. Percentage of grafting is found to depend upon the molar ratio of [FAS]/[H₂O₂]. An attempt has been made to compare the reactivities of the acceptor monomer (MMA and EA) with that of the donor monomer (VAc) toward grafting onto wool.     

Influence of nature/concentration of halide promoters and oxidation state on the direct oxidation of H2 to H2O2 over Pd/ZrO2 catalysts in aqueous acidic medium

The nature/concentration of halide promoters and influence of the Pd oxidation state on the promoted reaction system has been investigated on the direct H₂O₂ process over a 2.5 wt.% Pd/ZrO₂ catalyst in an aqueous acidic reaction medium. The oxidation state of Pd had a profound influence on the H₂O₂ synthesis process. Interestingly, the nature of the halide determined the magnitude/type of influence the Pd oxidation state exerted on the overall process. While the effect of the oxidation state on the H₂O₂ yields was large for the reaction systems containing F⁻ or no halide, the effect was significantly smaller for the reaction systems containing Br⁻ and Cl⁻. The nature of the halide also strongly influenced the H₂O₂ synthesis process. Br⁻ strongly enhanced the H₂O₂ yields, while F⁻ had a negative influence on the H₂O₂ yields. The ability of the halides to enhance the H₂O₂ process was found to strongly depend on its propensity to suppress the secondary H₂O₂ decomposition reaction. The influence of Br⁻ and Cl⁻concentration studies revealed that the optimum halide concentration for the direct H₂O₂ synthesis process was dependent on the nature of the halide. While the maximum in H₂O₂ yields for the Br⁻ containing reaction medium corresponded to a concentration of ∼0.9 mmol/dm³ (KBr) the maximum for the Cl⁻ containing solution was obtained at ∼1.5 mmol/dm³ (KCl). Such knowledge is crucial from the viewpoint of optimization (catalyst/reaction system screening studies) of the direct H₂O₂ process. The qualitative trends (H₂O₂ selectivity/yield) observed in case of the incorporated halide catalysts were similar to those observed with halides in reaction medium over the Pd/ZrO₂ catalyst.     

Preparation of an adsorbent by graft polymerization of acrylamide onto coconut husk for mercury(II) removal from aqueous solution and chloralkali industry wastewater

Graft copolymerization of acrylamide onto coconut husk (CH), initiated by the ferrous ammonium sulfate/H₂O₂ redox initiator system, was studied. To determine the optimum conditions of grafting, the effect of the concentrations of ferrous ammonium sulfate, the monomer, and H₂O₂ and the time and temperature on percentage of the graft yield was studied. A new adsorbent media having a carboxylate functional group was synthesized by the surface modification of polymer‐grafted coconut husk (PGCH COOH). The mechanism of graft polymerization and surface functionalization is proposed. The material exhibits a very high adsorption potential for Hg(II). The sorption of Hg(II) was found to be dependent on the contact time, concentration, pH, and temperature. Maximum removal of 99.4% with 2 g/L of the sorbent was observed at 125 μmol L⁻¹ Hg(II) concentration at pH 6.0. The slow step which determines the rate of exchange of Hg(II) ions is diffusion through the adsorbent particles. The diffusion coefficients, energy of activation, and entropy of activation were calculated and used to determine the theoretical behavior of the sorption process. The applicability of the Langmuir isotherm established the endothermic character of the adsorption. Acid regeneration was tried for several cycles with a view to recover the adsorbed metal ions and also to restore the sorbent to its original state. The adsorbent efficiency toward Hg(II) removal was tested using synthetic and chloralkali industry wastewaters. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1261–1269, 2000     

Peroxydiphosphate–metal ion–cellulose thiocarbonate redox system‐induced graft copolymerization of vinyl monomers onto cotton fabric

The grafting of methacrylic acid (MAA) and other vinyl monomers onto cotton cellulose in fabric form was investigated in an aqueous medium with a potassium peroxydiphosphate–metal ion–cellulose thiocarbonate redox initiation system. The graft copolymerization reaction was influenced by peroxydiphosphate (PP) concentration, the pH of the reaction medium, monomer concentration, the duration and temperature of polymerization, the nature of vinyl monomers, and the nature and concentration of metallic ions (activators). On the basis of a detailed investigation of these factors, the optimal conditions for the grafting of MAA onto cotton fabric with the said redox system were as follows: [Fe²⁺] = 0.1 mmol/L, [PP] = 2 mmol/L, [MAA] = 4%, pH‐2, grafting time = 2 h, grafting temperature = 70°C, and material/liquor ratio = 1 : 50. Under these optimal conditions, the graft yields of different monomers were in the following sequence: MAA ? acrylonitrile > acrylic acid > methyl acrylate > methyl methacrylate. The unmodified cellulosic fabric (the control) had no ability to be grafted with MAA with the PP–Fe²⁺ redox system. The percentage of grafting onto the thiocarbonated cellulosic fabric was more greatly enhanced in the presence of iron salts than in their absence. This held true when the lowest concentrations of these salts were used separately. A suitable mechanism for the grafting processes is suggested, in accordance with the experimental results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1879–1889, 2003     

The xanthate method of grafting. V. Graftability of mechanical pulp

Softwood mechanical pulp was copolymerized with acrylonitrile using the xanthate redox grafting process. Experiments carried out under different reaction conditions (temperature, H₂O₂, concentration, pH, reaction time) showed that mechanical pulp is less apt to form graft copolymers than chemical pulps. In most cases, long inhibition periods were observed, and the product formed thereafter contained large quantities of homopolymer. It was not possible to raise grafting efficiency by increasing the concentration of hydrogen peroxide. A series of experiments with pulps having different particle size showed a moderate increase in total conversation to polymer with decreasing mean fiber length. The latter, however, produced little influence on the copolymer/homopolymer ratio.     

Graft polymerization of methyl acrylate onto granular starch: Comparison of the Fe+2/H2O2 and ceric initiating systems

Graft polymerizations of methyl acrylate (MA) onto granular cornstarch were carried out in water with both ferrous ammonium sulfate/hydrogen peroxide (FAS/H₂O₂) and ceric ammonium nitrate (CAN) initiation. Starch concentrations were 10, 20, and 30% in water, and the amount of MA used was either 0.5, 1, or 2 mol per AGU of starch. Two concentrations of FAS/H₂O₂ were used: 1 mol each of FAS and H₂O₂ per 100 AGU of starch, and 1 mol per 1000 AGU. Significant amounts of acetone-extractable PMA homopolymer were produced, and homopolymer formation was especially high at the 1:100 ratio. Sharp exotherms were observed, and reaction mixtures reached maximum temperature within 2 min or less. Total conversions of MA to PMA were higher at the 1:100 ratio, and conversions in some polymerizations were nearly quantitative. CAN-initiated polymerizations were run under the same conditions used for FAS/H₂O₂; however, the amount of CAN used was limited to 1 mol per 100 AGU because of low conversions at the 1:1000 ratio. Compared with FAS/H₂O₂, CAN gave more moderate exotherms; and longer time periods were required for reaction mixtures to reach maximum temperature. CAN gave quantitative conversions of MA to PMA, but only low percentages of PMA homopolymer were observed. Differences between FAS/H₂O₂ and CAN initiation are consistent with differences in the two initiation mechanisms. High levels of homopolymer produced on starch granule surface with FAS/H₂O₂ could be seen in scanning electron micrographs and were also apparent in infrared spectra obtained with an attenuated total reflectance (ATR) cell. ATR spectra of acetone-extracted products indicated that the amount of PMA actually grafted to starch granule surfaces was similar with both initiating systems. Tensile properties of extruded ribbons prepared from these polymers did not vary greatly with the initiator used. © 1996 John Wiley & Sons, Inc.

1 This article is a U.S. Government work and, as such, is in the public domain in the United States of America.

     

Grafting of acrylic monomers onto cotton fabric using an activated cellulose thiocarbonate–azobisisobutyronitrile redox system

The feasibility of a cellulose thiocarbonate–azobisisobutyronitrile (AIBN) initiation system to induce graft copolymerization of methyl methacrylate (MMA) and other acrylic monomers onto cotton fabric was investigated. Other acrylic monomers were acrylic acid, acrylonitrile, and methyl acrylate. The initiation system under investigation was highly activated in the presence of a metal‐ion reductant or a metal‐ion oxidant in the polymerization medium. A number of variables in the grafting reaction were studied, including AIBN concentration, pH of the polymerization medium, nature of substrate, monomer concentration, duration and temperature of polymerization, and composition of the solvent/water polymerization medium. The solvents used were methanol, isopropanol, 1,4‐dioxane, cyclohexane, benzene, dimethyl formamide, and dimethyl sulfoxide. There were optimal concentrations of AIBN (5 mmol/L), MMA (8%), Fe²⁺ (0.1 mmol/L), Mn²⁺ (8 mmol/L), and Fe³⁺ (2 mmol/L). A polymerization medium of pH 2 and temperature of 70°C constituted the optimal conditions for grafting. The methanol/water mixture constituted the most favorable reaction medium for grafting MMA onto cotton fabric by using the Fe²⁺–cellulose thiocarbonate–AIBN redox system. MMA was superior to other monomers for grafting. The unmodified cotton cellulose showed very little tendency to be grafted with MMA compared with the chemically modified cellulosic substrate. A tentative mechanism for the grafting reaction was proposed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1261–1274, 2004     

Optimized conditions for the grafting reaction of poly(methyl acrylate) onto rubberwood fiber

Graft copolymerization of poly(methyl acrylate) (PMA) onto rubberwood fiber (RWF) was carried out by free radical initiation. Hydrogen peroxide and ferrous ions were used as an initiator system. Effects of various parameters (reaction temperature and reaction time, as well as hydrogen peroxide, ferrous ammonium sulfate and monomer concentrations) on the grafting percentage were investigated. A high percentage of grafting was achieved when optimum reaction conditions were used. The optimum temperature of the reaction was determined to be about 55 °C and the reaction time was 120 min. The optimum concentration of H₂O₂ was 0.03 M and the amounts of Fe²⁺ and MA were 0.4 mmol and 0.05 mol, respectively. The PMA homopolymer was removed from the graft copolymer by Soxhlet extraction using acetone. The presence of PMA on the fiber was confirmed by FT-IR spectroscopy and gravimetry. The surface morphology of the poly(methyl acrylate)-graft-(rubberwood fiber) was studied by means of scanning electron microscopy. Copyright © 2004 Society of Chemical Industry     

Graft copolymerization of 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid onto carboxymethylcellulose (sodium salt) by H2O2/Fe+2 redox pair

The effect of the reaction conditions on the grafting parameters during grafting of 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid onto sodium carboxymethylcellulose using H₂O₂/Fe⁺² redox pair are studied at 30°C. The grafting ratio, add on, and conversion initially increase with the H₂O₂ concentration in the range of (10.0–15.0) × 10^?2 mol dm^?3. Thereafter, these parameters decrease with the H₂O₂ concentration. The grafting ratio, add on, and conversion increase when increasing the ferrous ion concentration from (0.5 to 4.0) × 10^?2 mol dm^?3 and decrease with a further increase in the concentration. It is observed that the grafting ratio and add on increase with the monomer concentration, whereas the conversion decrease. The hydrogen ions seem to be facilitating the grafting reaction up to a certain concentration and after this concentration seem to be retarding the process. The grafting ratio, add on, and conversion decrease with the sodium carboxymethylcellulose concentration. When increasing the time period from 60 to 90 min, the grafting parameters increase but decrease thereafter. Similarly, when increasing the temperature from 25 to 30°C, the grafting parameters increase and decrease thereafter. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4819–4825, 2006     

Surface Modification of Acrylonitrile Copolymer Membranes by Grafting Acrylamide. II. Initiation by Fe2+/H2O2

Surface modification of membranes of an acrylonitrile copolymer (PAN) containing 5.5% methyl methacrylate and 4.0% sodium methylpropylenesulfonate by grafting acrylamide (AAm) with ferrous ammonium sulfate/H₂O₂ as an initiator in aqueous medium was studied. The grafted copolymer was verified by infrared spectra, X-ray photoelectron spectroscopy, and a scanning electron microscope (SEM). From the SEM photos, we know that the AAm homopolymer branches were grafted onto the surface of the membrane and the morphology of the PAN membrane did not change. The results showed that the extent of grafting was varied with some parameters, such as the pH value of the medium, reaction time and temperature, and concentration of AAm and H₂O₂. The results of the water-absorption percent of the membrane showed that the wettability of the modified PAN membrane was improved. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1907–1915, 1998     

H2O2-induced graft polymerization of acrylic acid on poly(ethylene terephthalate) fibers

Graft polymerization of acrylic acid to poly(ethylene terephthalate) fibers using H₂O₂ as initiator was only possible in benzyl alcohol as reaction medium. The effect of initiator and monomer concentrations, reaction time, and temperature as well as addition of metallic salts to the polymerization medium was studied. Percent grafting was enhanced significantly by increasing H₂O₂ concentrations up to 100 mequiv/L and then decreased upon further increase in initiator concentration. The same held true for acrylic acid concentration of up to 10%, but above this concentration grafting leveled off. Raising the polymerization temperature from 85 to 115°C favored grafting at lower H₂O₂concentration. The reverse was the case at higher H₂O₂ concentration (more than 25 mequiv/L). Addition of copper sulfate to the polymerization medium decreased the rate of grafting, and no leveling off of grafting could be achieved even after 5 h. The ferrous ammonium sulfate functioned similarly but to lesser degree, and leveling off of grafting occurred after 4 h. This contrasted with grafting in the absence of metallic salts where grafting leveled off after 1 h. Action of initial graft formation as diffusion barrier is believed to account for this.     

Graft copolymerization of glycidylmethacrylate onto modified nylon‐6 fibers

The graft copolymerization of glycidylmethacrylate (GMA) onto modified nylon‐6 fibers containing polydiallyldimethylammonium chloride (PDADMAC) groups in the presence of (Cu ²⁺–K₂S₂O₈) as a redox initiating system was carried out, with very high extent and almost without homopolymer formation. The mechanism of the graft polymerization induced by this system was suggested. The rate of grafting was determined by varying the monomer, K₂S₂O₈, and cupric ion concentrations as well as the amount of PDADMAC. The kinetic investigation revealed that the rate of grafting (Rp) of GMA onto modified nylon‐6 fibers is proportional to [GMA]^1.83, [CuSO₄·5H₂O]^0.46, [PDADMAC]^0.4, and [K₂S₂O₈]^1.43. The overall activation energy was 134.7 kJ/mol. The fine structure and thermal properties of the grafted nylon‐6 fibers were investigated. investigated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 613–618, 2006     

A novel method for vinyl grafting onto cotton fabric using ceric-cellulose thiocarbonate redox system

Treatment of cotton fabric with carbon disulphide in presence of NaOH resulted in cellulose thiocarbonate. The latter formed a complex when treated with ceric ammonium nitrate (CAN). After being thoroughly washed, the Ce^IV cellulose thiocarbonate was capable of initiating vinyl graft polymerization onto cotton fabric without homopolymer formation. The graft yield obtained with methyl methacrylate was found to increase by increasing CAN from zero to 50 mmol/l at temperatures from 60 to 80°C. Grafting was greatly favoured at pH 2; alkaline pH offset grafting. Incorporation of up to 7% of methanol, ethanol, or isopropanol in the aqueous polymerization medium enhanced grafting significantly with the certainty that the highest graft yield was obtained with isopropanol; using higher alcohol percentages decreased grafting. The rate of grafting showed an initial fast rate followed by a slower rate; 60 minutes reaction time proved appropriate for grafting irrespective of the condition used. In addition to methyl methacrylate the ability of Ce^IV-cellulose thiocarbonate to induce grafting of acrylonitrile and acrylamide was also examined. The rate of grafting followed the order methyl methacrylate > acrylonitrile > acrylamide.     

Grafting of methacrylic acid to loomastate viscose fabric using KMnO4/NaClO2 system

Graft polymerization of methacrylic acid (MAA) to loomstate viscose fabric (greige fabric) using KMnO₄/NaClO₂ system was studied. Residual thiocarbonate and/or sizing materials on the fabric as well as presence of NaClO₂ act in favor of primary radical formation which, in turn, accelerate formation of cellulose macroradicals capable of initiating grafting. The polymerization reaction was studied with respect to polymer yield, graft yield, homopolymer, total conversion, and graft efficiency. The magnitude of each of these characteristics was found to depend upon parameters such as concentrations of KMnO₄, NaClO₂, and MAA as well as liquor ratio, reaction time, and temperature of polymerization. By and large all these parameters enhance the polymerization process with the exception of the liquor ratio. A reaction mechanism for the polymerization reaction is also reported. © 1995 John Wiley & Sons, Inc.     

Fabrication of sulfonic acid chemisorption fibre by graft polymerization

A sulfonic acid fibre was fabricated by graft copolymerization of p-styrenesulfonate to Vion KN-1 fibre using redox and peroxide initiating systems with a static exchange capacity of 2 meq/g. Use of a redox initiating system in graft copolymerization causes the formation of up to 20–50 wt. % homopolymer, while the mass of homopolymer deceases to 10–25% in peroxide initiation. Repeated graft copolymerization of the monomer remaining in the solution virtually does not increase the effective degree of conversion.All-Russian Scientific-Research Institute of Polymer Fibres, Mytishchi. Translated from Khimicheskie Volokna, No. 1, pp. 28–31, January–February, 1994.     

Effects of space velocity on methanol synthesis from Co2/Co/H2 over Cu/ZnO/Al2O3 catalyst

The space velocity had profound and complicated effects on methanol synthesis from CO₂/CO/H₂ over Cu/ZnO/Al₂O₃ at 523 K and 3.0MPa. At high space velocities, methanol yields as well as the rate of methanol production increased continuously with increasing CO₂ concentration in the feed. Below a certain space velocity, methanol yields and reaction rates showed a maximum at CO₂ concentration of 5–10%. Different coverages of surface reaction intermediates on copper appeared to be responsible for this phenomenon. The space velocity that gave the maximal rate of methanol production also depended on the feed composition. Higher space velocity yielded higher rates for CO₂/ H₂ and the opposite effect was observed for the CO/H₂ feed. For CO₂/CO/H₂ feed, an optimal space velocity existed for obtaining the maximal rate.