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.     

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.     

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.     

Pentavalent vanadium ion-induced grafting of methyl methacrylate onto cotton cellulose

Graft polymerization of methyl methacrylate (MMA) onto cotton cellulose using vanadium pentanitrate as initiator was studied under a variety of conditions. The graft yield increased with increasing initiator concentration up to 8 mmole/l. and then decreased upon further increase in initiator concentration. Increasing MMA concentration from 1 to 5% was accompanied by a significant increase in the degree of grafting. The latter was also affected by the kind and concentration of the acid incorporated in the polymerization medium. Based on graft yields, the efficiency of the acids follows the order H₂SO₄ > HNO₃ > HClO₄. Replacement of the acid with isopropyl alcohol was also examined. An isopropyl alcohol concentration of 10% constitutes the optimal concentration for grafting. Maximum graft yield depends upon the polymerization temperature; it follows the order 50°C ≥ 60°C > 40°C > 30°C > 70°C. Reaction mechanisms for grafting in the presence of acid as well as in the presence of isopropyl alcohol are proposed.     

Radiation‐induced graft polymerization of methyl methacrylate onto ultrahigh molecular weight polyethylene in the presence of a metallic salt and acid

An attempt was made to graft methyl methacrylate (MMA) onto ultrahigh molecular weight polyethylene preirradiated in air in the presence of a metallic salt and acid. The grafting yield increased with increasing monomer concentration. The maximum grafting yield was around a 60 vol % monomer concentration. The results showed that the inclusion of FeSO₄ · 7H₂O and sulfuric acid in MMA grafting solutions was extremely beneficial and led to a most unusual synergistic effect in the radiation grafting, much more than with only a metallic salt. However, CuSO₄ · 5H₂O led to a detrimental effect. It is believed that sulfuric acid accelerates the decomposition of hydroperoxides in the presence of metallic salts such as Fe²⁺, inhibiting homopolymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2348–2356, 2002     

Grafting vinyl monomers onto silk fibers. VIII. Graft copolymerization of methyl methacrylate onto silk using tetravalent manganese–oxalic acid redox system

The graft copolymerization of methyl methacrylate onto silk fibers was investigated in aqueous solution using the Mn(IV)–oxalic acid redox system. The copolymerization reaction was carried out under a variety of conditions such as different monomer, initiator, oxalic acid, acid concentrations, and temperatures. The graft yield increases with increasing initiator concentration up to 5 × 10^?2M, and with further increase of the initiator concentration it decreases. The graft yield also increases with increasing sulfuric acid concentration up to 15 × 10^?2M, and decreases thereafter. The rate of grafting also increases with increase in oxalic acid concentration up to 1.5 × 10^?2M and 84.592 × 10^?2M, respectively, and thereafter the rate of grafting shows down. The effect of temperature, solvents, and salts on graft yield has also been investigated and a plausible rate expression has been derived.     

Grafting onto wool. XIV. Graft copolymerization of vinyl monomers by use of Mn(AcAc)3 as an initiator

Ethyl acrylate (EA), butyl acrylate (BA), and vinyl acetate (VAc) have been graft copolymerized onto Himachali wool fiber in an aqueous medium by using Mn(AcAc)₃ as an initiator. Graft copolymerization was studied at 45°, 55°, 65° and 75°C for various reaction periods. Percentage of grafting and percent efficiency were determined as functions of concentration of monomer, concentation of initiator, concentration of nitric acid, time, and temperature. Several grafting experiments were carried out in the presence of various additives which included: (i) pyridine and (ii) Et₃ N. EA, BA, and VAc were found to differ in reactivity towards grafting and followed the order: EA > BA > VAc.     

Graft polymerization of methyl methacrylate onto wool initiated by ferric acetylacetonate/dichloroacetic acid system

The graft polymerization of methyl methacrylate (MMA) initiated by ferric acetyl acetonate/dichloroacetic acid [Fe(acac)₃–Cl₂CHCOOH] system onto wool has been investigated in a mixture of water and dioxane. No grafting occurred in organic solvent; water was essential to the grafting. Both the total conversion and the percentage of grafting showed maxima when the mole ratio of Fe(acac)₃ and Cl₂CHCOOH was ¼. Increasing wool content increased the percentage of grafting, while homopolymer conversion was independent of wool content. The rate of grafting was not proportional to MMA concentration. The grafting mechanism was discussed from these results.     

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.     

Graft copolymerization of 4-vinyl pyridine onto isotactic polypropylene hydroperoxide by mutual irradiation method

An attempt has been made to graft copolymerize 4-vinyl pyridine onto isotactic polypropylene hydroperoxide by mutual irradiation method in an aqueous medium. Polypropylene hydroperoxide has been prepared by irradiating recrystallized polypropylene beads from a Co⁶⁰ source in the presence of air. The resulting polypropylene hydroperoxide beads have been used as the backbone polymer and grafting of 4-vinyl pyridine has been studied as a function of various reaction parameters. Optimum conditions for maximum percentage of grafting have been evaluated. Rate of grafting (R_g) has been determined as a function of preirradiation dose and initial monomer concentration. Water has been found to affect percentage of grafting. The graft copolymers have been characterized by spectroscopic method and isolation of the grafted poly(4-VP) from the graft copolymer. A plausible mechanism is proposed to explain the mutual grafting of 4-vinyl pyridine onto polypropylene hydroperoxide. © 1993 John Wiley & Sons, Inc.     

Grafting onto wool. VII. Ceric ion-initiated graft copolymerization of vinyl monomers. Comparison of monomer reactivities

In an attempt to compare relative reactivities of vinyl monomers toward grafting, methyl methacrylate (MMA) and acrylic acid (AAc) were grafted separately to Himachali wool in aqueous medium by using ceric ammonium nitrate (CAN) as redox initiator. Nitric acid was found to catalyze the reaction. Percent grafting was determined as a function of concentration of nitric acid, concentration of CAN, concentration of monomer, time, and temperature. Optimum conditions for maximum grafting were evaluated for each monomer and were found to depend upon the nature of the monomer. Reactivities of MMA and AAc toward grafting were compared with those of methyl acrylate (MA), ethyl acrylate (EA), and vinyl acetate (VAc) reported earlier from this laboratory and were found to follow the order MA > EA > MMA > VAc > AAc. An explanation for the observed order of reactivity of different vinyl monomers is presented.     

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.     

Studies on graft copolymerization of 4‐vinylpyridine onto guar gum

Graft copolymerization of 4‐vinylpyridine (4‐VP) onto guar gum (GOH) using potassium monopersulfate (PMS)/thioacetamide (TAA) as a redox pair was studied in an aqueous medium under inert atmosphere. The concentration of potassium monopersulfate and thioacetamide should be 1.0 × 10^?2 and 5.0 × 10^?3 mol dm^?3, respectively, for highest grafting ratio and efficiency. Efficient grafting was observed at 19.25 × 10^?2 and 4.87 × 10^?2 mol dm^?3 concentration of 4‐vinylpyridine and sulfuric acid, respectively. The optimum temperature for grafting is 30°C. As the time period of reaction is increased, the grafting ratio increases, whereas efficiency decreases. The plausible mechanism of grafting has been suggested. A sample of guar gum and guar‐ g‐4‐vinylpyridine were subjected to thermogravimetric analysis with the objective of studying the effect of grafting 4‐vinylpyridine on the thermal stability of guar gum. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2380–2385, 2002     

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 acrylic acid onto caesarweed fibers by cerric ion–toluene redox pair

The graft copolymerization of acrylic acid onto caesarweed fibers in aqueous media by cerric ion–toluene redox pair has been investigated. The percentage graft increased and then decreased with cerric ion concentration ranging from 8.3 to 100.0 × 10^?3 M with a peak value of 17%. The effects of toluene, substituted toluenes, acids, and acrylic acid were examined. The percentage graft increased and then decreased with toluene concentration with an optimum value of 53% at 18.0 × 10^?4 M toluene. Under identical reaction conditions, the percentage graft after 30 min for the graft polymerization initiated by substituted toluenes are in the order of p-toluene sulfonic acid > toluene > p-Xylene ? o-toluidine. Low concentrations of acetic acid were favorable to the graft polymerization. The percentage graft increased linearly with acrylic acid concentration reaching a value of 53% at 1.39 M acrylic acid. The presence of neutral salts had nominal effects on the percentage graft. The effect of temperature was investigated between 20 and 60°C. The percentage graft increased with temperature up to 40°C but showed a negative temperature dependence beyond 40°C. The calculated activation energy was 6.2 kcal mol^?1. Characterization of the physical properties of the grafted fibers was also conducted. © 1994 John Wiley & Sons, Inc.     

Grafting vinyl monomers onto wool fibers: Graft copolymerization of methyl methacrylate onto wool fibers using vanadyl acetyl acetonate complex

The graft copolymerization of methyl methacrylate (MMA) onto native and reduced Indian Chokla wool fibers was studied in aqueous solution using the acetylacetonate oxovanadium (IV) complex. The rate of grafting was investigated by varying the concentration of the monomer and the complex, acidity of the medium, and the solvent composition of the reaction medium. The graft yield increases with increasing concentration of the initiator up to 8.75 × 10^?5 mol/L, of the monomer up to 0.5634 mol/L, and thereafter it decreases. MMA was found to be the most active monomer when compared to other vinyl monomers. Grafting increases with increasing concentration of HClO₄ and with increasing temperature. Reduced and oxidized wools were found to be better substrates than untreated, esterified, crosslinked, and trinitrophenylated wools. The extent of grafting was mostly dependent upon the concentration of ? SH groups in case of reduced wool. A suitable reaction scheme has been proposed and the activation energy was calculated from Arrhenius plot.     

Grafting onto wool. XVI. Graft copolymerization of vinyl monomers by use of TBHP–FAS as redox initiator

Methyl acrylate (MA), methyl methacrylate (MMA), and n-butyl vinyl ether (n-BVE) have been graft-copolymerized onto Himachali wool in an aqueous medium by using tertiary butyl hydroperoxide ferrous ammonium sulfate (TBHP-FAS) redox system at 40°C, 50°C, 60°C, and 70°C for various reaction periods. Percentage of grafting and percent efficiency have been determined as functions of concentration of monomers, molar ratios of [TBHP]/[FAS], time and temperture. Molar ratios of [TBHP]/[FAS] were found to influence grafting of different monomers studied. Chemical evidence indicates that a covalent bond formation occurs between grafted polymeric chain and backbone polymer. The rate of grafting (R_p) and induction period (I_p) of different monomers towards graft copolymerization were determined as function of total initial monomer concentrations. R_p and I_p of n-BVE are independent of total initial monomer concentrations while R_p and I_p of both MA and MMA were found to depend on the total initial monomer concentrations. MA, MMA, and n-BVE were found to differ in reactivity towards grafting onto wool in the presence of (TBHP-FAS) redox system; the following reactivity order was observed: MMA > MA > n-BVE.     

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 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 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.