Grafting vinyl monomers onto wool fibers. I. Graft copolymerization of methyl methacrylate onto wool using V5+–thiourea redox system

The graft copolymerization of methyl methacrylate in wool fibers was investigated in aqueous solution using V⁵⁺—thiourea redox system. The rate of grafting was determined by varying monomer, thiourea, acidity of the medium, temperature, nature of wool, different acrylic monomers, and reaction medium. The graft yield increases significantly by increasing reaction time in the initial stages of the reaction but it does slow down on prolonging the duration of grafting. The effect of increasing monomer concentration brings about a significant enhancement in the graft yield. The graft yield increases with increasing thiourea concentration, but beyond 0.0075M, the percentage graft yield decreases. The graft yields are considerably influenced by chemical modification prior to grafting. Wool reduced with thioglycolic acid is more susceptible to grafting than untreated wool; the opposite effect is noted in the case of trinitrophenylated and esterified wools. A suitable kinetic scheme has been proposed and the rate equation has been evaluated.     

Redox-initiated vinyl graft copolymerisation onto wool with thiourea as the reductant. II. Fe3+-thiourea co-catalyst induced graft copolymerisation of methyl methacrylate on wool and modified wool fibres.

The capability of Fe³⁺-thiourea redox system to induce graft polymerisation of methyl methacrylate onto wool fibres was investigated under various conditions. Variables studied include sequence of addition of reagents, acidity of the reaction medium, temperature, monomer concentration and nature of the substrate. In addition, alkali solubility of wool before and after grafting was examined. Allowing the ferric ion to be absorbed first on wool before addition of the thiourea and monomer leads not only to higher grafting but to greater grafting efficiency and total conversion than when all the reagents were present together. The graft yield increases significantly by increasing reaction time in the initial stages of the reaction but it does slow down on prolonging the duration of grafting. The effect of increasing monomer concentration is to bring about a significant enhancement in the graft yield. The same holds true for acidity of the reaction medium and temperature. The graft yields are considerably influenced by chemical modification prior to grafting. For instance, wool reduced via treatment with thioglycolic acid is more amenable to grafting than untreated wool. The opposite holds true for esterified and dinitrophenylated wools. The alkali solubility of wool decreases significantly by increasing the graft yield; a graft yield of ca. 95% makes wool practically unimpaired with aqueous sodium hydroxide.     

Grafting vinyl monomers onto silk fibers: Graft copolymerization of methyl methacrylate onto silk using acetylacetonate Mn(III) complex

The graft copolymerization of methyl methacrylate onto Mulberry silk fibers was studied in aqueous solution using Mn(acac)₃ as initiator. Perchloric acid was found to catalyze the reaction. The rate of grafting was investigated by varying the concentration of the monomer and the complex, acidity of the medium, the solvent composition of the reaction medium, the surfactants, and the inhibitors. The graft yield increases with increasing concentration of Mn(acac)₃ up to 0.01 mol/L, decreasing thereafter. Increase of MMA concentration up to 0.56 mol/L increases graft yield, and thereafter it decreases. Among the various vinyl monomers studied, MMA was found to be most suitable for grafting. Grafting increases up to 7.5 × 10^?3 mol/L of HClO₄ concentration, and thereafter it decreases. A suitable reaction scheme has been proposed and a rate equation has been derived. The energy of activation has been calculated from the Arrhenius plot. The chain transfer constants for various chain transfer solvents have been evaluated from the average molecular weight (M?) of grafted poly(methyl methacrylate).     

Grafting vinyl monomers onto wool fibers. VIII. Graft copolymerization of methyl methacrylate onto wool using peroxydiphosphate–fructose redox system

The graft copolymerization of methyl methacrylate onto wool fibers was investigated in aqueous solution using the peroxydiphosphate–fructose redox system. The rate of grafting was determined by varying monomer, acidity of the medium, temperature, nature of wool, and reaction medium. The graft yield increases with increase in peroxydiphosphate concentration. With increase in concentration of fructose up to 7.5 × 10^?4 mole/l., there is a significant increase in graft yield; and with further increase in concentration of fructose the graft yield decreases. The graft yield increases with increase in monomer concentration up to 65.72 × 10^?2 mole/l. and decreases thereafter. The grafting is considerably influenced by chemical modification prior to grafting. The effect of acid, temperature, and solvent on the rate of grafting has been investigated and a suitable rate expression has been derived.     

Grafting vinyl monomers onto wool fibers. V. Graft copolymerization of methyl methacrylate onto wool using peroxydiphosphate as initiator

Graft copolymerization of methyl methacrylate onto wool was investigated in aqueous solution using potassium peroxydiphosphate as initiator. The rate of grafting was determined by varying monomer, peroxydiphosphate ion, temperature, solvent, and nature of wool. The graft yield increases with increase in monomer concentration. The graft yield increases significantly by increasing peroxydiphosphate ion up to 80 × 10^?4mole/l.; with further increase of peroxydiphosphate ion the graft yield decreases. The rate of grafting increases with increase in temperature. The effect of acid-and water-soluble solvents on the rate of grafting was investigated and a suitable rate expression has been derived.     

Graft polymerization of methyl methacrylate onto wool using dimethylaniline/copper(II) system

Dimethylaniline (DMA)/Cu^II-induced grafting of methyl methacrylate (MMA) onto wool fibres was studied under different conditions. The grafting reaction was found to be influenced by Cu^II, DMA, and MMA concentrations as well as polymerization temperature, reaction time, and polymerization medium. While the graft yield increased by increasing the amount of MMA from 100 to 500 mmol/L, maximum grafting occurred at 0.5 mmol/L CuSO₄, 10 mmol/L DMA. The graft yield increased by increasing the reaction time from 15 to 150 min and by raising the polymerization temperature from 60 to 80°C. Using dimethylformamide/water and ethyl alcohol/water mixture as a medium for grafting decreased the graft yield, while using isopropyl alcohol/water mixtures increased the graft yield as compared to pure aqueous medium.     

Studies on graft copolymerization of methyl methacrylate onto chemically modified tussa silk fibers. Peroxydisulfate-thiourea redox system

The graft copolymerization of methyl methacrylate (MMA) onto chemically modified tussa silk fibers in aqueous media using potassium peroxodisulfate-thiourea redox initiator system was studied at 60°C. The effects of time of reaction, concentrations of oxidant, thiourea (TU), monomer (M), amount of silk fibers on graft yield have been studied. The effects of reaction medium, acid concentration, and some inorganic salts and organic solvents on grafting have also been investigated. A significant increase in percent of grafting was observed with increasing monomer concentration to 65.86 · 10^?2 mol · 1^?1; a further increase of monomer concentration is associated with the decrease of graft yield. The graft yield increases with an increase of thiourea concentration up to 10 · 10^?1 mol · 1^?1, beyond which it decreases very significantly. A measurable increase of the graft yield was also observed with an increase of the oxidant concentration up to 0.08 mol · 1^?1 beyond which the graft yield decreased. The graft yield was medium dependent. The reaction mechanism of the grafting process has been proposed and a rate expression has been derived on the basis of experimental findings. IR spectra of the grafted fiber and original fiber have been taken and their characteristic bands have been identified. The thermal behaviour of the original and grafted silk fibers has been studied by TGA and DTG analysis. Grafting has improved thermal stability as well as the light fastness of silk dyed with Rhodamine B.     

Redox-initiated vinyl graft copolymerization onto wool with thiourea as the reductant. III. Di-tert.-butyl peroxide thiourea system

Graft copolymerization of wool with methyl methacrylate (MMA) induced by di-tert.-butyl peroxide (DTBP)/thiourea (TU) system in acid medium was studied. The rate of the copolymerization reaction depends on concentrations of DTBP, TU and MMA, temperature as well as kind of acid and solvent used. The graft yield increases by increasing the concentration of DTBP and MMA. Increasing the temperature enhances also the graft formation; 60°C produces higher grafting than 50°C. Carrying out the graft polymerization reaction in acid medium by using nitric acid has proved to be the best in comparison with sulphuric and formic acid. There is an optimal concentration of TU (0.4 M); lower grafting is achieved below and above this concentration. A mixture of isopropanol/water at a ratio of 10:90 constitutes the most favourable reaction medium since increasing the solvent content is accompanied by a reduction in the graft yield. The kind of solvent does affect the graft yield: for the solvent studied, the graft yield follows the order: isopropanol < acetone < dimethylsulphoxide. Incorporation of an acid dye in the polymerization system to affect concurrent dyeing and grafting was carried out and the properties of the products so obtained were examined. The changes in alkali solubility of wool by grafting was also investigated. In addition, a reaction mechanism based essentially on complexes formed between DTBP and wool and/or DTBP and TU and their subsequent dissociation to give wool macroradicals was suggested.     

Grafting onto wool

Summary In order to study the role of -SH group of wool in graft copolymerization, an attempt has been made to study grafting of acrylic acid (AAc) onto reduced wool in aqueous medium using ceric ammonium nitrate (CAN) as redox initiator. HNO₃ was found to catalyze the graft copolymerization. Reduction of wool was effected with thioglycolic acid (TGA) in aqueous medium. Percentage of grafting was determined as a function of concentration of (i) CAN, (ii) vinyl monomer (AAc), (iii) nitric acid, (iv) time and (v) temperature. Under optimum conditions, poly-(acrylic acid) was grafted to the reduced wool to the extent of 9.14%, the unreduced wool under optimum conditions afforded maximum grafting of poly(AAc) to the extent of 12.24%. Reduction of wool does not promote grafting of AAc in the presence of CAN.     

Grafting onto wool fibers: Graft copolymerization of methyl methacrylate onto wool fibers initiated by KHSO5/Fe(III) couple

Graft copolymerization of methyl methacrylate (MMA) onto wool fibers has been carried out in an aqueous medium under deaerated condition initiated by potassium monopersulphate (KHSO₅/Fe(III) system, at varying concentration of the reactants and temperature. The effect of various salts and organic solvents on the extent of grafting has also been studied. Maximum graft percentage of 210.8% was obtained in 4 h at 40°C with the concentration of MMA (0.46 M), KHSO₅ (0.0195 M), Fe(III) (1.25 × 10^?4 M) in the presence of 50% formic acid. Various improved properties of the grafts have been studied and compared with the parent fiber.     

Graft copolymerization of methyl methacrylate onto wool by use of ferrous ion–peroxodiphosphate

Polymethyl methacrylate has been graft copolymerized onto wool using a ferrous ion–peroxodiphosphate initiator system in an aqueous methanol medium. Graft copolymerization was carried out at 20°C, 30°C, 40°C, and 50°C. The rate of grafting was found to be dependent on the concentrations of monomer (MMA), ferrous ion (Fe²⁺), peroxodisphosphate (PP), wool (w), and reaction temperature. [Acid], solvent composition and ionic strenghth were also varied to study their effect on grafting. Based on the experimental results, a suitable kinetic scheme was proposed. Rate and thermodynamic parameters were also varied to study their effect on grafting. Based on the experimental results, a suitable kinetic scheme was proposed. Rate and thermodynamic parameters were also evaluated.     

Graft copolymerization of methyl methacrylate onto wool using thallium (III) ions as initiator

The graft copolymerization of methyl methacrylate onto wool initiated by thallium (III) perchloric was investigated in aqueous perchloric acid medium. The rate of grafting was evaluated varying the concentrations of the monomer, initiator, acid, and temperature. The rate of grafting was found to increase with the increase of the monomer and the initiator concentration. The graft yield was found to decrease upon increasing the acid concentration. Increase of temperature was accompanied with the increase of the graft yield. From the Arrhenius plot the overall activation energy was calculated to be 4.7 kcal/mol. The effect of inhibitors, various solvents, cationic and anionic surfactants, and different inorganic salts on the graft yield was studied. The grafting was considerably influenced by chemical modification of wool prior to grafting. A suitable kinetic scheme has been proposed, and a rate equation has been derived.     

Grafting vinyl monomers onto silk fibers III. Graft copolymerization of methyl methacrylate onto silk using tetravalent cerium as initiator

The use of tetravalent ceric ions to initiate graft-copolymerization of methyl methacrylate onto silk has been investigated. The rate of grafting has been determined by varying monomer, cerium (IV), temperature, and nature of silk. The graft yield increases with increasing monomer concentration up to 0.65 mol/l and with further increase of monomer, the graft yield decreases. The percentage of grafting increases with increasing ceric ion concentration up to 0.03 mol/l and thereafter it decreases. The rate of reaction is temperature dependent, with increasing temperature, the graft yield increases. The grafting is considerably influenced by chemical modification prior to grafting. The effect of different species of ceric ion and CuSO₄ on the rate of grafting has also been investigated.     

Graft copolymerization of benzyl methacrylate onto wool fibers

Benzyl methacrylate (BzMA) was graft copolymerized onto wool fibers by using ammonium peroxydisulphate as the initiator. Grafted samples with different polymer add ons (from 7 to 180%) were obtained by varying the monomer concentration in the reaction system. Following grafting with BzMA, the X-ray diffraction peak at 20.2° slightly moved towards higher spacing values. Birefringence decreased, indicating a lower degree of molecular orientation of grafted wool fibers. The equilibrium regain values of grafted wool decreased with increasing add on. Tensile strength increased in the range 45–77% add on, while elongation at break decreased. Differential scanning calorimetry (DSC) and thermogravimetry (TG) measurements showed a higher thermal stability for grafted wool. Following grafting, the drop of dynamic storage modulus (E′) shifted to a lower temperature. Accordingly, the intensity of the loss modulus (E′) peak decreased, indicating that the thermally induced molecular motion was enhanced by grafting. Thermomechanical analysis (TMA) confirmed the increase in chain mobility for the grafted wool fibers. Above 35–40% add on, the presence of homopolymer on the surface of the wool fibers was identified by scanning electron microscopy. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 343–350, 1997     

Graft polymerization of methacrylate onto wool using dimethylaniline–benzyl chloride mixture as initiator

Graft polymerization of wool with methyl methacrylate (MMA) initiated by a dimethylaniline–benzyl chloride (DMA/BC) mixture was extensively studied. The grafting and homopolymerization reactions are influenced by the nature of the solvent used; ethanol proved to be the best. Using water as a cosolvent enhances significantly both graft formation and homopolymerization. A mixture of water/ethanol at a ratio of 90:10 constitutes the optimal medium for the grafting reaction. Addition of acetic acid or formic acid in low concentration (0.2 mole/l.) favors grafting. The opposite holds true for sulfuric and hydrochloric acid. Kinetic investigations showed that the rates of total conversion (R_p) and grafting (R_p′) are dependent of the concentrations of DMA, BC, acetic acid (Ac) and amount of wool (W), as well as temperature. They can be expressed by the following equations: The overall activation energies for the total conversion and grafting reactions amount to 8.5 and 9.0 kcal/mole, respectively; whereas the corresponding energies for initiations E_d are E_d′ 7.0 and 8.0 kcal/mole, respectively. The changes in the physical and/or chemical structure of wool via reduction, acetylation, and dinitrophenylation are reflected on the susceptibility of wool toward grafting. While reduced wool showed higher grafting, the graft yields obtained with acetylated and dinitrophenylated wools were quite poor. The alkali solubility of wool graft copolymer was determined and its tendency to felt was examined. Evidences for grafting were provided and a tentative mechanism for grafting initiation was suggested.     

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.     

Trivalent manganese chelate-initiated graft copolymerization of methyl methacrylate onto silk fibers

The graft copolymerization of methyl methacrylate onto silk fibers was investigated in aqueous solution using Mn³⁺ acetyl acetonate [Mn(acac)₃] as initiator. The rate of grafting was determined by varying monomer, acidity of medium, temperature, and reaction medium. The graft yield increases significantly with increase of [Mn(acac)₃] concentration up to 0.01M, and with further increase of [Mn(acac)₃] the graft yield decreases. The effect of the increase of monomer concentration brings about a significant enhancement in the graft yield, and with further increase the graft yield decreases. The rate of reaction is temperature dependent; with increasing temperature, the graft yield increases. Among the solvent composition studied, a water/solvent mixture containing 10% of the solvent seems to constitute the most favorable medium for grafting, and, with further increase of solvent composition, the graft yield decreases. The effect of some inorganic salts, organic solvents, and complexing agents has been investigated.     

Grafting vinyl monomers onto polyester fibers. III. Graft copolymerization of methyl methacrylate onto poly(ethylene terephthalate) using potassium permanganate–oxalic acid redox system

The use of the KMnO₄—oxalic acid redox system to initiate graft copolymerization of methyl methacrylate (MMA) onto poly(ethylene terephthalate) (PET) fiber has been investigated. The rate of grafting was determined by varying the concentrations of monomer, KMnO₄, oxalic acid, acidity of the medium, and temperature. The graft yield increases steadily with increasing KMnO₄ concentration. The graft yield is also influenced with concentration. The graft yield is also influenced with temperature. The effect of certain solvents on the rate of grafting has been investigated, and a suitable reaction mechanism has been proposed.     

Graft copolymerization of methacrylates onto wool fibers

Grafting of butyl (BuMA), decyl (DeMA), and octadecyl methacrylate (ODeMA) onto reduced wool was carried out by using K₂S₂O₈ or K₂S₂O₈–LiBr redox system as initiator. The influence of the monomer and monomer concentration, temperature, and duration of the reaction on the percentage of grafting was studied. Evidence of grafting was provided by scanning electron microscopy, size exclusion chromatography, and infrared spectroscopy.     

Grafting vinyl monomers onto wool fibers IV. Graft copolymerization of methyl methacrylate onto wool using peroxydisulfate catalysed by silver ions

Graft copolymerization of methyl methacrylate onto wool was investigated in aqueous solution using peroxydisulfate catalysed by silver ions. The rate of grafting was determined by varying the concentration of monomer, peroxydisulfate ion, thiourea, the temperature and the solvent. The graft yield increased with increasing monomer concentration, peroxydisulfate concentration, thiourea concentration, and temperature in all cases to a certain value, beyond of which a decrease in graft yield was observed. The effect of certain inorganic salts and water soluble solvents on the rate of grafting was investigated. The alkali solubility of the grafted fiber was studied.