Graft copolymerization of methyl methacrylate onto jute fibers. Studies on vanadium (V)-cyclohexanol redox system

Graft copolymerization of methyl methacrylate (MMA) onto natural jute (chemically modified) was studied using V⁵⁺ -cyclohexanol redox initiator system. The effects of time, concentration of metal ion (V⁵⁺), monomer (MMA), substrate, amount of jute fibers, temperature, and acid concentration on graft yield have been studied. The effects of some organic solvents and inorganic salts on graft yield have also been studied. A grafting mechanism is proposed and an expression has been derived for the reaction rate. Grafting has improved the thermal stability and the light fastness of jute fibers dyed with basic dyes. IR spectra of the natural jute (chemically modified) and grafted jute have been taken. More than 170% graft yield could be achieved with the present system.     

Graft copolymerization of acrylonitrile onto jute fibers (studies on Ce(IV)-hippuric acid redox system)

Graft copolymerization of acrylonitrile (AN) onto chemically modified bleached jute fibers was studied using Ce(IV)-hippuric acid redox initiator system. The effects of time, temperature, concentration of monomer (AN), metal ion (Ce⁴⁺), hippuric acid, sulfuric acid, and amount of jute fiber on graft yield have been studied. The effects of some organic solvents and inorganic salts on graft yield have also been studied. Infrared spectra of chemically modified bleached jute and grafted jute have been taken and their characteristic bands have been identified. More than 90% graft yield could be achieved with the present system.     

Influence of N-acetylglycine on the kinetics of the ceric ion-initiated graft copolymerization of acrylonitrile and methyl methacrylate onto jute fibers

The influence of N-acetylglycine on the kinetics of graft copolymerization of acrylonitrile (AN) and methyl methacrylate (MMA) onto chemically modified jute fibers was studied in the temperature range 40–60°C. The optimum conditions for grafting have been determined by studying the effects of concentrations of monomers, Ce(IV), and N-acetylglycine on the rate of grafting. Besides the effect of time, temperature, and concentration of the acid, the amount of jute fibers and some organic solvents and inorganic salts on the rate of grafting has been investigated. On the basis of experimental findings, a kinetic scheme has been proposed. Infrared spectra of chemically modified jute and grafted jute have been investigated. More than 185% graft yield could be achieved with the present system. Grafting has improved the thermal stability of jute fibers. © 1994 John Wiley & Sons, Inc.     

Vanadium-cyclohexanone–initiated graft copolymerization of methyl methacrylate onto jute fibers

Graft copolymerization of methyl methacrylate (MMA) was carried out on jute fibers using a V⁵⁺ -cyclohexanone redox initiator system. The effect of the concentration of acid, monomer, and V⁵⁺ on graft yield have been studied. In order to obtain optimum conditions of grafting, the effects of temperature, acid, reaction medium, solvent, and some inorganic salts on graft yield have been investigated. The most remarkable features of the investigation include the proposition of a mechanism and derivation of rate expression for the grafting process. More than 100% grafting could be achieved with the present system.     

Graft Copolymerization of Acrylonitrile on Chemically Modified Sisal Fibers

Graft copolymerization of acrylonitrile (AN) on chemically modified sisal fibers was studied using a combination of NaIO₄ and CuSO₄ as initiator in an aqueous medium in the temperature range of 50–70°C. Effects of reaction medium, variation of time and temperature, concentration of CuSO₄, NaIO₄ and AN, and the amount of sisal fiber on the percentage of graft yield have been investigated. Water absorption (%) and tensile properties such as tensile strength, Young's modulus and extension at break of untreated, chemically modified and AN‐grafted sisal fibers were evaluated and compared. FTIR spectroscopy and scanning electron microscopy (SEM) of the chemically modified and AN‐grafted sisal fibers have been carried out.     

Surface modification of coir fibers. II. Cu(II)‐ IO initiated graft copolymerization of acrylonitrile onto chemically modified coir fibers

A study of the graft copolymerization of acrylonitrile (AN) onto chemically modified coir fibers was carried out using a CuSO₄ and NaIO₄ combination as the initiator in an aqueous medium in a temperature range of 50–70°C. The graft yield was influenced by the reaction time, temperature, concentration of CuSO₄, concentration of NaIO₄, and monomer concentration. Grafting was also carried out in the presence of inorganic salts and organic solvents. A combination of copper(II) and sodium periodate (Cu²⁺‐IO) in an aqueous medium with an IO concentration of 0.005 mol L^?1 and a Cu²⁺ concentration of 0.004 mol L^?1 produced optimum grafting. The chemically modified and AN grafted fibers were characterized by FTIR and scanning electron microscopy (SEM). The SEM studies revealed that grafting not only takes place on the surface of the fibers but also penetrates the fiber matrix. The tensile properties like the maximum stress at break and extension at break of untreated, chemically modified, and AN grafted coir fibers were evaluated and compared. The extent of absorption of water of untreated, chemically modified, and grafted coir fibers was determined. It was found that grafting of AN imparts hydrophobicity onto coir fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 75–82, 2002; DOI 10.1002/app.10221     

FTIR spectra and physico-chemical behavior of vinyl ester participated transesterification and curing of jute

In this article we report the transesterification of jute with n-Butylacrylate (BA) under appropriate condition using NaOH, Pyridine (Py), and a Pyridine–acetone mixture as a catalyst. The modified vinylog jute was subsequently cured with benzoylperoxide (BPO) in acetone at 50–60°C. The parent and chemically modified jute were characterized by FTIR spectra. The percent moisture regain, mechanical strength, and behavior to common chemical reagents of the parent and modified fibers have also been tested. Transesterification and curing of jute lowered the percentage of moisture regain, imparted mechanical strength, and resistance to common chemical reagents. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 575–581, 2001     

Graft copolymerization of methyl methacrylate onto jute fiber initiated by cerium(IV)–DMSO redox initiator system

The kinetics of graft copolymerization of methyl methacrylate (MMA) onto chemically modified jute fibers initiated by the Ce(IV)–DMSO redox system was studied in the temperature range of 40–60°C. By studying the effects of the concentration of the monomer, Ce(IV), and DMSO on the rate of grafting, the optimum conditions for grafting were determined. Also, the effect of temperature, time, concentration of the acid, the amount of jute fiber, and some inorganic salts and organic solvents on the rate was investigated. A kinetic scheme was proposed on the basis of the experimental findings. Infrared spectra of chemically modified jute and grafted jute was investigated. More than 120% of grafting could be achieved with the present system. The characterization of MMA-grafted chemically modified jute by TGA and DTA studies was made. The thermal stability of the jute fibers was improved by grafting. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2569–2576, 1998     

Graft copolymerization onto starch. III. Grafting of acrylonitrile to gelatinized potato starch by manganic pyrophosphate initiation

Recent development of synthesis and applications in grafting of acrylonitrile (AN) to gelatinized starch by Ce⁴⁺ initiation have been briefly reviewed. Using the Mn³⁺ method, the effects of starch pretreatment temperature on grafting parameters in grafting of AN onto starch have been studied. Total conversion of AN to PAN and % add-on were almost constant and showed only slight variation with increasing starch pretreatment temperature. Average molecular weight of grafts showed, however, an increase by a factor of nearly 10 (i.e., from 0.4 X 10⁵ to 4 X 10⁵) after swelling and gelatinization of the starch, and the grafting frequency (anhydroglucose units per grafted chain) increased in proportion. In grafting of AN onto gelatinized starch, increasing Mn³⁺ concentration increased the conversion of monomer and % add-on, whereas the average molecular weight of grafts and the grafting frequency (AGU/chain) decreased. An increase in the amount of starch also increased the conversion of monomer and the grafting frequency (AGU/chain) but decreased the % add-on and the average molecular weight of the grafts. Selective solution of PAN homopolymer by dimethylformamide indicated that grafting efficiencies were high in all cases. The results are interpreted in terms of slow termination rates due to high viscosity of gelatinized starch.     

Study of jute fiber reinforced polyester composites by dynamic mechanical analysis

Cyanoethylation of jute fibers in the form of nonwoven fabric was studied, and these chemically modified fibers were used to make jute–polyester composites. The dynamic mechanical thermal properties of unsaturated polyester resin (cured) and composites of unmodified and chemically modified jute–polyester were studied by using a dynamic mechanical analyzer over a wide temperature range. The data suggest that the storage modulus and thermal transition temperature of the composites increased enormously due to cyanoethylation of fiber. An increase of the storage modulus of composites, prepared from chemically modified fiber, indicates its higher stiffness as compared to a composite prepared from unmodified fiber. It is also observed that incorporation of jute fiber (both unmodified and modified) with the unsaturated resin reduced the tan δ peak height remarkably. Composites prepared from cyanoethylated jute show better creep resistance at comparatively lower temperatures. On the contrary, a reversed phenomenon is observed at higher temperatures (120°C and above). Scanning electron micrographs of tensile fracture surfaces of unmodified and modified jute–polyester composites clearly demonstrate better fiber–matrix bonding in the case of the latter. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1505–1513, 1999     

Antibacterial,flame retardant,and physico‐chemical properties of cotton fabric graft copolymerized with a binary mixture of acrylonitrile and 4‐vinylpyridine

Modification of cotton fabric has been carried out through chemically induced graft copolymerization of binary mixture of acrylonitrile (AN) and 4‐vinyl pyridine (4‐VP) using ceric ammonium nitrate, (CAN) as initiator. Maximum percentage of grafting (151.28%) has been obtained at [4‐VP] = 0.376 mol L^?1 and [AN] = 1.221 mol L^?1, [CAN] = 0.0255 mol L^?1 and [HNO₃] = 0.9585 mol L^?1 in 25mL of water at 70°C in 180 min. Post quarternization and phosphorylation reactions of the grey and grafted cotton fabrics have been carried out to study their antibacterial and flame retardant properties respectively. The fabrics have been characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The physico‐chemical properties such as wettability, moisture regain, crease recovery and tensile strength of the grey and grafted cotton fabric have also been evaluated. The modified fabric has been shown to exhibit excellent antibacterial and flame retarding properties with improved physico‐chemical properties except for the mechanical properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40415.     

Role of microporosity and surface functionality of activated carbon in methylene blue dye removal from water

Activated carbons have been prepared from jute stick by both chemical and physical activation methods using zinc chloride and steam, respectively. They were characterized by evaluating surface area, iodine number, pore size distribution, and concentration of surface functional groups. The chemically activated carbon largely featured micropore structure, while the physically activated carbon mainly featured macropore structure. The specific surface area of chemically and physically activated carbons was 2,325 and 723 m ² /g, while the iodine number was 2,105 and 815mg/g, respectively. The concentration of surface functional groups was determined by Boehm titration method, which suggested that different types of surface functional groups are randomly distributed on chemical activated carbons, while it is limited for physical activated carbon. The microporosity along with surface functional groups provided a unique property to chemically activated carbon to adsorb Methylene Blue dye to a large extent. The adsorption of dye was also affected by the adsorption parameters such as adsorption time, temperature and pH. Comparatively, higher temperature and pH significantly facilitated dye adsorption on chemically activated carbon.     

Voltammetric study of interaction of Co(phen)3 with DNA at gold nanoparticle self-assembly electrode

Modifying electrode surfaces on the molecule scale allow developing new electrochemical biosensors. A new strategy for the immobilization of calf thymus DNA on the surface of gold nanoparticles which are co-immobilized at a gold electrode through 4,4^′-bis(methanethiol) biphenyl (MTP) molecule by assembly process is demonstrated. The DNA modified electrode was incubated in Co(phen)₃³⁺ solution of an aqueous buffer or an acetonitrile (AN) solution, then it was rinsed and placed in a Co(phen)₃³⁺ free buffer solution or AN solution, followed by cyclic voltammetric experiments. Clear redox peaks of Co(phen)₃³⁺ were observed both in an aqueous and AN solutions. The concentration of supporting electrolyte on electrochemical behavior was discussed. It was found that the surface coverage value of DNA molecules on modified gold nanoparticle and the redox current of adsorbed Co(phen)₃³⁺ were decrease with increasing the size of gold nanoparticles (6, 25, 42, 73, and 93 nm). In aqueous solution, the electron transfer rate constant of Co(phen)₃^3+/2+ redox couple became slow with increasing the diameter of gold nanoparticle, and the speed almost had nothing to do with the diameter in nonaqueous solution. The surface concentration of Co(phen)₃³⁺ adsorption on DNA modified electrode decreased and rate constant of adsorption kinetics increased with increasing the interactive temperature. In AN solution, the electrostatic interaction between DNA and Co(phen)₃^3+/2+ was greatly reduced, however, compare with in aqueous solution the interaction between DNA and reduced form of Co(phen)₃²⁺ was more strongly than oxidized form Co(phen)₃³⁺. The surface concentration of Co(phen)₃³⁺ adsorption on DNA modified electrode reach maximum value when the interactive temperature about 20 °C, and rate constant of adsorption kinetics nearly independent of the interactive temperature. The results show that the DNA can adsorb on the modified electrode firmly and the Co(phen)₃^3+/2+ adsorbed on DNA give good electrochemical response both in aqueous and nonaqueous solutions. It was confirmed that the DNA modified electrode can be applied in a nonaqueous system and the modified electrode can be used to investigate the interaction between DNA and electroactive species both in aqueous and nonaqueous systems.     

Studies on graft copolymerization of acrylonitrile onto jute fiber with permanganate ion initiation system in presence of air

The graft copolymerization of acrylonitrile with jute using potassium permanganate as the initiator has been studied in the presence of air. To establish reaction conditions for the graft copolymerization of acrylonitrile (AN) onto jute, the effect of different variables such as the residual lignin content of bleached jute (after bleaching with sodium chlorite), initiator concentration, monomer concentration, time of polymerization, reaction temperature, and amount of bleached jute fiber have been studied. As evidence of polymer grafting, some instrumental analyses such as scanning electron microscopy, infrared, and thermogravimetry have been carried out. The extent of grafting of acrylonitrile depends on how much lignin is present on the jute fiber. Percent grafting and grafting efficiency have also been studied. © 1995 John Wiley & Sons, Inc.     

Ce(IV)-N-acetylglycine initiated graft copolymerization of acrylonitrile onto chemically modified pineapple leaf fibers

Graft copolymerization of acrylonitrile (AN) onto chemically modified pineapple leaf fiber (PALF) was studied using Ce(IV) and N-acetylglycine (NAG) combination as initiator in the temperature range 40–60°C. The effects of concentration of monomer, Ce(IV), and NAG on graft yield have been studied. Besides the effects of time, temperature, acid, amount of PALF, some inorganic salts and organic solvents on graft yield have been investigated. FTIR and scanning electron microscopy of PALF and grafted PALF have been studied. Grafting has improved the thermal stability of PALF. © 1996 John Wiley & Sons, Inc.     

Catalytic Consequences of a Revised Distribution of Key Elements at the Active Centers of the M1 Phase of the MoVNbTeOx System

In an earlier publication (Grasselli et al., Top Catal 54:595, 2011) [1] we analyzed the distribution of key catalytic elements at the active site of the M1 phase of the MoVNbTeO_x catalyst system based on the definition of this center put forth in our original work (Grasselli et al., Top Catal 23:5, 2003) [2]. From that analysis we derived the probabilities of the metal element distributions at the active center and its immediate surroundings, and based on those results, proposed a model for propane ammoxidation on M1. Recently, the occupancies and concomitant charges of the various elements of the M1 phase have been revised (Li et al., Top Catal 54:614, 2011) [3]. Based on this revised structural model we have now recalculated the elemental probabilities at the active center and its immediate surroundings, and describe here the catalytic consequences in the ammoxidation mechanism of propane that these changes portend. Our revised model (REV) predicts more closely the actual experimental results of propane ammoxidation over MoVNbTeO_x than does our first model (ORIG). The results obtained are: ORIG Model: 41 % AN (acrylonitrile) concerted, 82 % total possible AN; REV Model: 43 % AN concerted, 59 % total possible AN; experimental: 42 % AN concerted, 62 % total possible AN using both the M1 + M2 phases. Comparing the original (Grasselli et al., Top Catal 23:5, 2003) [2] and current (Li et al., Top Catal 54:614, 2011) [3] elemental distributions at the active centers of M1 and the ORIG and REV ammoxidation reaction pathways (from the derived models), it is readily apparent that higher concentrations of V⁵⁺ at the active centers lead to undesirable overoxidation of propane and thus lower AN selectivity. Therefore, decreasing the surface concentration of vanadium in M1 (to favor more site isolated V⁵⁺ sites) should be beneficial and lead to better AN selectivities and yields. Additionally, selective doping or selective isomorphous substitution of M1 (and/or M2) should also be useful approaches towards improved AN yields.     

Oxidative dehydrogenation of ethane on a magnesium-vanadium aluminophosphate (MgVAPO-5) catalyst

Vanadium and/or magnesium substituted aluminophosphate with ALPO₄-5 structure have been prepared by hydrothermal synthesis. These catalysts have been tested for the oxidative dehydrogenation (ODH) of ethane. ALPO₄-5 has a low activity and low selectivity for the ODH of ethane. The presence of Mg²⁺ ions in MgAPO-5 increases the selectivity to ethene, while the presence of V⁵⁺ species in VAPO-5 increases both the activity and the selectivity for this reaction. The presence of Mg²⁺ and V⁵⁺ species in the vanadium-magnesium alumino-phosphate (MgVAPO-5) results in a more selective catalysts for the ODH of ethane. The behavior of MgVAPO-5 could be attributed to the presence of acid sites (Mg²⁺) near to the redox sites (V⁵⁺) in the molecular sieve framework.     

Electron Beam Grafted Polymer Adsorbent for Removal of Heavy Metal Ion from Aqueous Solution

Abstract

An electron beam grafted adsorbent was synthesized by post irradiation grafting of acrylonitrile (AN) on to a non‐woven thermally bonded polypropylene (PP) sheet using 2 MeV electron beam accelerator. The grafted poly(acrylonitrile) chains were chemically modified to convert a nitrile group to an amidoxime (AMO) group, a chelating group responsible for metal ion uptake from an aqueous solution. The effect of various experimental variables viz. dose, dose rate, temperature, and solvent composition on the grafting extent was investigated. PP grafted with the amidoxime group (AMO‐g‐PP) was tested for its suitability as an adsorbent for removal of heavy metal ions such as Co²⁺, Ni²⁺, Mn²⁺, and Cd²⁺ from aqueous solution. Langmuir and Freundlich adsorption models were used to investigate the type of adsorption of these ions. The adsorption capacities of the adsorbent for the metal ions were found to follow the order Cd²⁺>Co²⁺>Ni²⁺>Mn²⁺. The kinetics of adsorption of these ions indicated that the rate of adsorption of Cd²⁺ was faster than that of other ions studied.     

Effects of dopants on the reliability of low temperature sintered Li2ZnTi3O8 ceramics

The effects of acceptor dopant (typical Mn²⁺) and donor dopant (typical V⁵⁺) on the reliability of Li₂ZnTi₃O₈ based low temperature co-fired ceramics (LTCC, in short) have been investigated. Large difference occurs among different types of dopants. V⁵⁺ doping decreases the breakdown voltage of the multilayer capacitors which were manufactured by low temperature sintered Li₂ZnTi₃O₈ ceramics, however, Mn²⁺ doping increases the breakdown voltage and lowers down the leakage current significantly. This may very likely due to the fact that donor induces the generation of weak bound electrons while acceptor capture the weak bound electrons. The results suggest that Mn²⁺ is a very effective additive for improving the reliability of low temperature sintered Li₂ZnTi₃O₈ ceramics.     

Polyacrylonitrile (PAN)-grafted jute fibres: Some physical and chemical properties and morphology

Grafting of polyacrylonitrile (PAN) on (dewaxed and bleached) jute fibres was done by aqueous polymerization of acrylonitrile (AN) in the presence of the fiber samples employing a sodium periodate (IO₄^?) and copper sulfate (Cu²⁺) combination as the initiator. Effect of PAN grafting to different extents on X-ray crystallinity, tensile properties, thermal behavior, whiteness index, dyeability, light-fastness rating, and moisture regain properties of the fiber samples were studied and analyzed. Their rot resistance, determined by a standard soil burial test, were also examined and compared. Twenty to thirty percent PAN-grafting was found to impart a most desirable balance of physical properties including fiber strength and modulus, moisture regain, whiteness index, and light-fastness rating. PAN grafting also makes the otherwise nonresistant jute fiber significantly rot-resistant. Morphology of the different fiber samples as studied and compared using scanning electron microscopy indicates that PAN grafting occurs on surfaces and intercellular regions as well as within the lumens of the multicellular jute fibers. © 1994 John Wiley & Sons, Inc.