Graft copolymerization of wool using acrylate monomers. I. Optimum conditions of grafting and molecular weight of grafts

Wool fibres were grafted with methyl acrylate, ethyl acrylate, n-butyl acrylate and methylmethacrylate to various percentages of grafting in nitrogen atmosphere using ceric ammonium nitrate in nitric acid as initiator. The effects of concentration of the initiator, acid, monomer, temperature and time on the grafting were investigated. A comparison of such results indicated the following reactivity order of monomers: methyl acrylate > ethyl acrylate > methylmethacrylate > n-butyl acrylate. The molecular weights of the grafts were investigated by isolating the grafts from the fibres.     

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.     

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.     

Thermal behavior of graft copolymers of cotton cellulose and acrylate monomers

Cotton cellulose yarn was grafted with methyl acrylate, ethyl acrylate, n-butyl acrylate, and methyl methacrylate at various percentages of grafting. The effects of concentration of the initiator, concentration of the acid, and of temperature on grafting was studied and the mechanism discussed. The effect of reactivity of the monomer on the percentage graft-on is pointed out. Thermal behavior of natural and grafted cotton yarn was studied using dynamic thermogravimetry in air at a heating rate of 6°C/min up to a temperature of 500°C. The thermal stabilities of the samples grafted with various acrylate monomers to various percentages of grafting were computed from their primary thermograms by calculating the values of IDT, IPDT, and E^*. The results show that the thermal stability increases with increase in graft-on per cent, and the thermal stabilities of natural cotton and cotton grafted with different monomers are in the order ethyl > methyl > natural cellulose > methyl methacrylate > n-butyl acrylate.     

Graft copolymerization of acrylate monomers onto sulfonated jute–cotton blended fabric

Graft copolymerization of acrylate monomers, e.g., methyl methacrylate and ethyl methacrylate, onto bleached sulfonated jute–cotton‐blended fabric was carried out in an aqueous medium, using potassium persulfate as an initiator under the catalytic influence of ferrous sulfate in a nitrogen atmosphere. The parameter variables, e.g., concentrations of monomer, potassium persulfate, ferrous sulfate, reaction time, and reaction temperature, directly influenced the percent graft yield. The percent graft yield increased to a certain value in each variable, and the percent graft yield of methyl methacrylate and ethyl methacrylate was about 15.9 and 17.1%, respectively. Polymer grafting was characterized by thermogravimetric analysis, infrared spectroscopy, and X‐ray diffractometry. Grafting improved the thermal stability, protected from photo‐oxidative degradation, decreased the dyeability, and had positive impact on fastness characteristics. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4393–4398, 2006     

纤维素醚的乳接枝共聚合

在水溶性聚合物羟丙基甲基纤维素（ＨＰＭＣ０存在下进行丙烯酸酯的乳液支共聚合,研究了引发剂加料方式,用量和ＨＰＭＣ用量对接枝率的影响,结果表明,引发剂质量分数和引发与纤维素的预接触时间对接枝率有显著影响,增大ＨＰＭＣ质量分数导致表观接枝率和真实接枝率明显下降。     

Graft copolymerization of methyl acrylate onto poly(vinyl alcohol) initiated by potassium diperiodatonickelate(IV)

The graft copolymerization of methyl acrylate onto poly(vinyl alcohol) (PVA) with a potassium diperiodatonickelate(IV) [Ni(IV)]–PVA redox system as an initiator was investigated in an alkaline medium. The grafting parameters were determined as functions of the temperature and the concentrations of the monomer and initiator. The structures of the graft copolymers were confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. The Ni(IV)–PVA system was found to be an efficient redox initiator for this graft copolymerization. A single‐electron‐transfer mechanism was proposed for the formation of radicals and the initiation. Other acrylate monomers, such as methyl methacrylate, ethyl acrylate, n‐butyl acrylate, and n‐butyl methacrylate, were used as reductants for graft copolymerization. These reactions definitely occurred to some degree. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 529–534, 2003     

Graft copolymerization of methyl acrylate onto poly(vinyl alcohol) initiated by potassium diperiodatoargentate(III)

The graft copolymerization of methyl acrylate onto poly(vinyl alcohol) (PVA) using potassium diperiodatoargentate(III) [Ag(III)]–PVA redox system as initiator was studied in an alkaline medium. Some structural features and properties of the graft copolymer were confirmed by Fourier‐transfer infrared spectroscopy, scanning electron microscope, X‐ray diffraction and thermogravimetric analysis. The grafting parameters were determined as a function of concentrations of monomer, initiator, macromolecular backbone (X?_n = 1750, M? = 80 000 g mol^?1), reaction temperature and reaction time. A mechanism based on two single‐electron transfer steps is proposed to explain the formation of radicals and the initiation profile. Other acrylate monomers, such as methyl methacrylate, ethyl acrylate and n‐butyl acrylate, were also used to produce graft copolymerizations. It has been confirmed that grafting occurred to some degree. Thermogravimetric analysis was performed in a study of the moisture resistance of the graft copolymer. Copyright © 2004 Society of Chemical Industry     

Synthesis and characterization of graft copolymers of ethyl acrylate/acrylamide mixtures onto starch

Graft copolymerization of ethyl acrylate/acrylamide onto corn starch using potassium permanganate–citric acid initiation system was investigated. Major factors affecting the polymerization reaction were thoroughly investigated in terms of initiator concentration, monomer concentration, polymerization time, polymerization temperature, and starch/liquor, and the obtained results implied that the polymer yield which were expressed by total monomer conversion, grafting ratio, and grafting efficiency were determined by these factors. The optimum reaction conditions were as follows: starch, 30 g; potassium permanganate (based on weight of starch), 0.1%; citric acid (based on weight of starch), 0.5%; ethyl acrylate, 20%; acrylamide, 0.4 g; time, 3 h; temperature, 40°C; starch/liquor, 1:3. We concluded that the initiator of potassium permanganate–citric acid system could be used as a cheap initiator in manufacturing the starch graft copolymer. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Grafting of methyl methacrylate to nitrocellulose by ceric ions

Studies were carried out on grafting of various vinyl monomers to nitrocellulose by ceric ions. It was observed that graft copolymerization occurred only with methyl methacrylate (MMA) and methyl acrylate monomer. The variables such as initiator concentration, monomer concentration, time of grafting, and nitrocellulose content on grafting of MMA are discussed. By hydrolyzing away the nitrocellulose backbone, the grafted poly(methyl methacrylate) branches were isolated and the >c?o peak at 1740 cm^?1 in the infrared spectra of these isolated branches gave definite evidence of grafting. The molecular weight of isolated branches has been determined by viscometry. The probable mechanism of grafting may be at the α-carbon atom of primary alcohol or at a C₂-C₃ glycol group of the anhydro glucose unit or at the hemiacetal group of the end unit of nitrocellulose, as nitrocellulose is formed by the partial nitration of cotton cellulose.     

Grafting onto wool. XI. Graft copolymerization of poly(vinyl acetate) and poly(methyl acrylate) onto reduced wool in presence of potassium persulfate–ferrous ammonium sulfate (KPS—FAS) system as redox initiator

In an attempt to ascertain the role of—SH groups of Himachali wool during graft copolymerization, poly(viny acetate) (PVAc) and poly(methyl acrylate) (PMA) were graft copolymerized onto reduced wool by using potassium persulfate—ferrous ammonium sulfate (KPS—FAS) redox pair in aqueous medium. Reduction of wool was carried out by sodium bisulfite solution of varying concentrations for different reaction periods. Concentration of reducing agent and the extent of reduction were found to influence grafting of vinyl monomers. Maximum grafting of methyl acrylate (MA) and vinyl acetate (VAc) occurred when wool was reduced by 1% and 0.5% NaHSO₃ solution, respectively, for 24 h. Increase in percent grafting of MA onto reduced wool compared to that of unreduced wool has been ascribed to the production of more—SH groups by reduction of—SS—groups of wool fiber.     

Synthesis and characterization of butyl acrylate graft sodium salt of partially carboxymethylated starch

Graft copolymers were synthesized by graft copolymerization of butyl acrylate (BA) onto sodium salt of partially carboxymethylated starch (Na‐PCMS). Ceric ammonium nitrate (CAN), a redox initiator, was used for initiation of graft copolymerization reaction. All the experiments were run with Na‐PCMS having degree of substitution, DS = 0.35. The grafting reaction was characterized by parameters such as % total conversion (%Ct), % grafting (%G), % grafting efficiency (%GE), and % add‐on. Graft copolymers were characterized by infrared spectral analysis and scanning electron microscopy. Variables affecting graft copolymerization reaction such as nitric acid concentration, reaction time, reaction temperature, and ceric ion concentration were investigated. The results revealed that 0.3M CAN as initiator, 0.3M HNO₃, with reaction time 4–4.5 h at 25–30°C were found as suitable parameters for maximum yield of graft copolymerization reaction. © 2006 Wiley Periodicals, Inc. JAppl Polym Sci 102: 3334–3340, 2006     

Graft copolymerization of vinyl monomers onto chitin with cerium (IV) ion

Graft copolymerization of vinyl compounds onto chitin was studied, and an efficient and reproducible procedure has been established, cerium (IV) being used as the initiator. The reactions with acrylamide and acrylic acid onto powdery chitin were carried out under various conditions to elucidate the polymerization behavior in terms of grafting percentage. The amount of cerium (IV) affected the polymerization most strikingly, and grafting percentages showed maxima with suitable amounts of initiator for both the monomers. As a solvent water proved to be superior to aqueous nitric acid except the reaction with a small amount of initiator. Under appropriate conditions, around 240 and 200% grafting percentages were achieved for acrylamide and acrylic acid, respectively. The resulting graft copolymers showed much improved affinity for solvents and hygroscopicity compared to the original chitin.     

Graft copolymerization of starch with methyl acrylate: An examination of reaction variables

Starch-g-poly(methyl acrylate) (S-g-PMA) copolymers containing 55–60% PMA were prepared from cornstarch, high amylose cornstarch, and waxy cornstarch with ceric ammonium nitrate initiation. Graft copolymers were characterized with respect to % PMA homopolymer, % conversion of monomer to polymer, grafted PMA content, grafting frequency, and the molecular weight and molecular weight distributions of PMA grafts. Variables investigated in the graft copolymerization reaction were nitric acid concentration, ceric ion-to-starch ratio, reaction time, gelatinization of the starch, and reactant concentration in water. At high reactant concentrations, high conversions of methyl acrylate to grafted PMA could be obtained in less than 0.5 h at 25°C. © 1993 John Wiley & Sons, Inc.     

Grafting of cellulose–thiocarbamate with vinyl monomers: Antimicrobial activity

Grafting of vinyl monomers onto cellulose-thiocarbamate was carried out using ceric ammonium sulfate (CAS) as an initiator. The graft yield was found to depend on the amount of thiocarbamate groups, initiator, and monomer concentrations as well as temperature. The graft yield increased with increasing (CAS) concentration. The reactivity of vinyl monomers studied followed the order ethyl acrylate>acrylonitrile. A comparison between the graft yields obtained with the modified cullulose indicated that cellulose thiocarbamates having less than 1.1% nitrogen showed lower graft yields than the unmodified cellulose. Above this, cellulose thiocarbamate was much more amenable to grafting than the unmodified cellulose. The grafted cellulose thiocarbamates exhibited high antifungal activity and had no effect on gram-negative, gram-positive bacteria and yeast. The maximum zone of inhibition was obtained after grafting with 2 h which resulted in 43 and 50% add-on polymer in the cases of acrylonitrile and ethyl acrylate, respectively. Grafted cellulose thiocarbamates with acrylonitrile had higher potency for antifungal activity than that grafted with ethyl acrylate.     

Kinetics and mechanism of free radical grafting of methyl acrylate onto sago starch

The graft copolymerization was carried out by methyl acrylate with sago starch in which ceric ammonium nitrate was used as an initiator. It has been found that the rates of graft polymerization and grafting efficiency were dependent upon the concentration of ceric ammonium nitrate (CAN), methyl acrylate (MA), sago starch (AGU, anhydro glucose unit), mineral acid (H₂SO₄), and as well as reaction temperature and period. A rate equation of polymerization was established from the proposed reaction mechanism, and the rate of polymerization (R_p) was the first‐order dependence of the MA monomer concentration and square root of the CAN concentration. A new kinetic model of the grafting reaction has been proposed, and a normal kinetics of methyl acrylate polymerization was observed. An equation of a predicted model relating the graft fraction of poly(methyl acrylate) with the sago starch has been derived, and validity of the predicted model was verified by the experimental results. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 784–791, 2000     

Effect of radiation chemical treatment on sisal fibers I. Radiation induced grafting of ethyl acrylate

Radiation induced graft copolymerization of ethyl acrylate onto sisal fibers was investigated. It was fond that the percent added-on of ethyl acrylate to sisal fibers was prohibitively low when using the direct grafting method due to excessive hompolymerization. The preirradiation method was found to be invalid for improving the grafting content. In the presence of small amounts of styrene (St) the copolymerization can be achieved with little homopolymer formation by the direct grafting technique. The presence of sulfuric acid in the grafting solution enhances the grafting of styrene–ethyl acrylate comonomer to sisal fibers. the effect of different solvents, monomer concentration, and irradiation doses were followed. Sisal fibers were treated with sodium hydroxide, sulfuric acid, and combined treatment of both of them. The effect of these treatments on the grafting content was investigated. The grafting yield decreased when sisal fibers were subjected to alkali treatment under tension. However, sisal fibers pretreated with 0.4N sulfuric acid showed a slight increase in the grafting yield over the untreated samples.     

Grafting of methyl methacrylate onto guar gum by hydrogen peroxide initiation

Graft copolymerization of methyl methacrylate (MMA) onto guar gum (GG) in aqueous slurry has been carried out using hydrogen peroxide (H₂O₂) as initiator. The copolymers were characterized by infrared spectroscopy. The grafting parameters like percent grafting, grafting efficiency, percent add-on, and the grafting frequency were determined, and the effect of reaction time, concentration of initiator, and [GG]/[MMA] ratios on the grafting parameters have been discussed. The decrease in % add-on at increasing concentration of H₂O₂ indicated enhancement in the rate of homopolymerization of methyl methacrylate.     

Ionic Xanthate Method of Grafting. II

In the ionic xanthate method of grafting, the increase of sodium hydroxide concentration and liquor ratio increased the grafting parameters up to a limit. The limit varied from one monomer to another. The positive values of the standard degree of concentration of sodium hydroxide indicate that the graft polymerization reaction has happened. The extent of decrease in the grafting parameters with the increase of the liquor ratio may be due to an increase of termination reactions as a result of the increasing number of HOH molecules, with resulting chain transfer reactions to solvent. Grafting parameters also increased with an increase of the concentration of monomers up to a limit. The reactivity of these monomers is in the order: methyl methacrylate > ethyl acrylate > allyl chloride > acrylonitrile > methyl acrylate > allyl alcohol, being dependent on both the radical stabilization and the strength of the electron acceptance of the monomers. The activation energy of the overall polymerization reaction (i.e., grafting and homopolymer) decreased with the increase of the crude grafting yield, and the reverse relation was achieved with the true grafting yield (i.e., grafting reaction only). This difference may contribute to the difference in the conformation of the polymer chains in graft polymerization on the active sites of the cellulose chains.     

Ionic Xanthate Method of Grafting. II

In the ionic xanthate method of grafting, the increase of sodium hydroxide concentration and liquor ratio increased the grafting parameters up to a limit. The limit varied from one monomer to another. The positive values of the standard degree of concentration of sodium hydroxide indicate that the graft polymerization reaction has happened. The extent of decrease in the grafting parameters with the increase of the liquor ratio may be due to the increase of the termination reactions as a result of increasing the number of HOH molecules and the consequent chain transfer reactions to solvent. Grafting parameters also increased with the increase of the concentration of monomers up to a limit. The reactivity of these monomers is in the order: methyl methacrylate > ethyl acrylate > allyl chloride > acrylonitrile > methyl acrylate > allyl alcohol, being dependent on both the radical stabilization and the strength of the electron acceptance of the monomers. The activation energy of the overall polymerization reaction (i.e., grafting and homopolymer) decreased with the increase of the crude grafting yield, and the reverse relation was achieved with the true grafting yield (i.e., grafting reaction only). This difference may be attributed to the difference in the conformation of the polymer chains to graft polymerize on the active sites of the cellulose chains.