Physical properties of natural and modified cotton cellulose grafted with acrylate monomers

Natural, cyanoethylated, and formaldehyde-crosslinked cotton cellulose has been grafted with methyl, ethyl, and n-butyl acrylate and methyl methacrylate monomers. Various physical properties such as density, moisture regain, birefringence, and mechanical properties were studied. The results indicate that the density and moisture regain of the grafted fibers are less than those of natural cotton. The birefringence of grafted fibers is also less than that of natural cotton. The variation in birefringence with percent graft-on depends on the monomer. Parameters such as orientation factor, helix angle, and refractive power of fibers were calculated from the birefringence data and the results discussed. It was observed that due to grafting of both natural and crosslinked cotton, there is a decrease in tensile strength, increase in elongation at break, and decrease in the initial modulus. Attempts are made to understand these changes in the properties of cotton in terms of the changes occurring in the fine structure of the fiber.     

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 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.     

Pentavalent vanadium ion–cellulose thiocarbonate redox-system induced grafting of methyl methacrylate and other vinyl monomers onto cotton fabric

Cellulose thiocarbonate was prepared by reacting cotton cellulose fabric with carbon disulphide in the presence of sodium hydroxide. The treated fabric formed, with pentavalent vanadium ion, an effective redox system capable of initiating grafting of methyl methacrylate (MMA) and other monomers no+o the cotton fabric. The dependence of grafting on vanadium concentration, pH of the polymerization medium, temperature and duration of grafting, nature and concentration of monomer, and solvent/water ratio was studied. The results indicated that increasing the pentavalent vanadium (V^v) concentration up to 60 mmol/L was accompanied by enhancement in the rate of grafting; the latter was not affected by further increase in V^v concentration. Maximum grafting yield was achieved at pH 2; grafting fell greatly at higher pH. The rate of grafting followed the order: 70° > 60° > 50°C. The graft yield increased significantly by increasing the MMA concentration from 0.5 to 5%. Of the solvents studied, n-propanol and isopropanol enhanced the grafting rate provided that a solvent/water ratio of 5 : 95 was used; a higher solvent ratio decreased the magnitude of grafting. Other solvents, namely, methanol, ethanol, n-butanol, and acetone, in any proportion, decreased the rate of grafting. With the monomer used, the graft yield followed the order: methyl methacrylate > methyl acrylate > methacrylic acid > ethyl methacrylate > acrylic acid. Also reported was a tentative mechanism for vinyl-graft copolymerization onto cotton fabric using cellulose thiocarbonate-V^v. © 1993 John Wiley & Sons, Inc.     

Grafting onto wool,XVII. Graft copolymerization of methyl acrylate and ethyl acrylate by use of VO(acac)2 as initiator. Comparison of monomer reactivities

Graft copolymerization of acceptor monomers methyl acrylate and ethyl acrylate onto Himachali wool fiber has been studied in aqueous medium by using vanadium oxyacetyl acetonate as initiator at 40, 50, 60, and 70°C. Graft copolymerization was carried out for various reaction periods and nitric acid was found to catalyse the reaction. Percentage of grafting and percent efficiency have been determined as functions of concentration of nitric acid, concentration of initiator, concentration of monomer, time, and temperature. Under optimum conditions, methyl acrylate and ethyl acrylate afforded maximum grafting to the extent of 28.4 and 18.5%, respectively. Relative reactivities of methyl acrylate and ethyl acrylate towards grafting have been compared with those of methyl methacrylate, acrylic acid and vinyl acetate reported earlier from this laboratory. Different vinyl monomers showed the following reactivity order: MMA > MA > EA > AAc > VAc. Several grafting experiments were carried out in the presence of various additives which included tert-butylhydroperoxide (TBHP), dimethylsulfoxide, pyridine, and dimethylformamide. Only TBHP was found to enhance grafting to a considerable extent, other additives decrease percent grafting of both methyl acrylate and ethyl acrylate.     

New polymeric materials for paper and textiles conservation. II. Grafting polymerization of ethyl acrylate/methyl methacrylate copolymers onto linen and cotton

In the preservation of Cultural Heritage items, the use of polymeric materials for the consolidation and protection of artifacts with historical and artistic value is widely accepted, except for cellulose‐based materials, since here there are no suitable products and appropriate application techniques. Grafting polymerization of acrylic monomers onto cellulose chains represents an innovative method of restoration for both artificially and naturally aged textiles. In this article, some results concerning the grafting polymerization of ethyl acrylate/ethyl methacrylate 75/25 and ethyl acrylate/methyl methacrylate/trifluoroethyl methacrylate 73/24.5/2.5 polymers onto linen and cotton are reported. The effectiveness of grafting polymerization as a method for textiles conservation is discussed. The consolidating and protective effects were investigated by evaluating the mechanical properties and the wetting behavior of the grafted samples, and comparing them with the original and aged substrates. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 90–99, 2007     

Thermal behavior of cellulosic graft copolymers. II. Cotton grafted with binary mixtures of vinyl acetate and methyl acrylate

Thermal degradation of cotton, mercerized cotton, cotton grafted with vinyl acetate-methyl acrylate mixtures at different compositions, and mercerized cotton grafted with vinyl acetate–methyl acrylate mixture at a composition of 60 : 40 has been investigated using the techniques of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) in nitrogen. The kinetic parameters E, n, and A have been obtained following several methods of thermogravimetric analyses. The mercerization shows a little effect upon thermic properties of cotton cellulose, making cotton thermally more stable. Graft copolymerization of vinyl acetate-methyl acrylate mixture makes cotton thermally less stable if the composition of the copolymer grafted is 100, 90, and 70 mol % VA, while in the case of cellulose graft copolymers with compositions of VA–MA of 80 : 20, 20 : 80, 5 : 95, and 0 : 100 the thermal stability is higher than that of original cotton. The thermal stability of the mercerized cotton grafted with vinyl acetate-methyl acrylate mixture with a composition of 60 : 40 depends on the percent grafting yield. The thermal stability of mercerized cotton grafted with the monomer mixture is higher than that of cotton grafted with that monomer mixture. The degradation of cellulose and cellulose graft copolymers is complex as is shown by DTA thermograms and kinetic parameters.     

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     

Modification of polyvinyl chloride-vinyl acetate latex by seed emulsion polymerization of acrylic monomers

Fundamental studies were carried out to modify the thermal properties of polyvinyl chloride (PVC)-based latices. General features of composite PVC-vinyl acetate (VAc) copolymer latices synthesized from the seed emulsion polymerization of acrylic monomers are reported, in particular, the observation of particle morphology and the measurements of minimum film formation temperature (MFT) and DSC spectra. Acrylic monomers used as modifiers were methyl methacrylate (MMA), n-butyl methacrylate (BMA), methyl acrylate (MA), ethyl acrylate (EA), n-butyl acrylate (nBA), and MMA-nBA 75:25,50:50 and 25:75 wt%. Styrene whose polymer is incompatible with PVC-VAc was used as a counterpart of compatible PMMA. Compatibility between seed and modifier polymer and the mode of operation, either batch (flooded and pre-swollen) or semi-batch (starved and no swelling), induced morphology differences, and consequently variations of thermal properties.     

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.     

Study of thermal and dyeing behavior of isotactic polypropylene fiber graft copolymerized with acrylate monomers using preirradiation method

In an attempt to modify isotactic polypropylene (IPP) fiber, grafting of acrylate monomers such as methyl acrylate (MA) and ethyl acrylate (EA) onto IPP has been carried out by preirradiation method in aqueous medium. Percentage of grafting has been determined as a function of various reaction parameters. Rate of grafting (R_g) and induction period (I_p) have been evaluated as a function of total initial monomer concentration. Methyl acrylate was found to be more reactive than ethyl acrylate toward grafting. Thermogravimetric analysis (TGA) indicates that the thermal stability of polypropylene fiber is significantly improved upon grafting. While polypropylene fiber could not be dyed by crystal violet, the grafted fiber was dyed with crystal violet, and the dye uptake has been quantitatively determined by spectrometric method. © 1994 John Wiley & Sons, Inc.     

Polymer-leather composites. I. Process and location study for the deposition of selected acrylate monomers by polymerization into chrome-tanned cattlehide

Three acrylate monomer systems were deposited by redox emulsion polymerization at room temperature into the fibrous matrix of 2-mm-thick chrome-tanned cattlehide over a wide range of composition. Polymer not bound to the matrix was separated by hot benzene extractions. Monomers used were methyl methacrylate, a mixture of n-butyl acrylate and methyl methacrylate and n-butyl acrylate, each selected to produce composites having wide variation in glass-transition temperature. The same three systems were introduced into the free space of leather by bulk and solution polymerization. All conversions were close to 100%. When the emulsion technique was used, with feed composition variable, overall deposition efficiency depended on the characteristic rate of deposition for the individual acrylate monomers. Observed orders in deposition rate and overall efficiency were: methyl methacrylate > comonomer > n-butyl acrylate. However, specific deposition efficiencies declined roughly monotonically with feed or time increase, but maintained the same order. Microscopic examination of thin sections revealed polymer only in the outer region of the leather cross section. Information on polymer location and its influence on specimen thickness for composites prepared by both emulsion and solution methods of deposition were obtained by correlating experimental densities with theoretical density–composition curves for various assumed models. The foregoing, together with observations of greatly reduced grafting frequency, in view of the maximum theoretically attainable, made a dominant grafting mechanism unattractive. A mechanism involving diffusion controlled monomer transport to occluded radicals in localized polymer deposits was suggested as an alternative.     

Graft copolymerization of methyl methacrylate and other vinyl monomers onto cotton fabric using ferrous cellulose thiocarbonate–N-bromosuccinimide redox initiation system

The cellulose thiocarbonate, in the fabric from, was treated first with a freshly prepared ferrous ammonium sulphate (FAS) solution. The sotreated fabric formed, with N-bromosuccinimide (NBS), an effective redox system capable of initiating grafting of methyl methacrylate (MMA) and other vinyl monomers onto the cotton fabric. The effect of the polymerization conditions the polymer criteria, namely, graft yeild, homopolymer, total conversion, and grafting efficiency, was studied. These polymer criteria were found to depend extensively upon concentrations of the Fe²⁺ ion (activator), NBS (initiator), and MMA; pH of the polymerization medium, and duration and temperature of polymerization. Based on detailed investigation of these factors, the optimal conditions for grafting were as follows: Fe²⁺, 1 × 10⁻³ mol/L; NBS, 1 × 10⁻² mol/L; MMA, 4%; pH, 2: polymerization time, 150 min; polymerization temperature, 60°C; material/liquor ratio, 1: 100. Under these optimal conditions, the rates of grafting of different vinyl monomers were in the following sequence: methyl methacrylate ≫ methyl acrylate > acrylonitrile. Other vinyl monomers namely, acrylic acid, and methacrylic acid have no ability to be grafted to the cellulosic fabric using the said redox system. A tentative mechanism for the polymerization reaction is suggested. © 1996 John Wiley & Sons, Inc.     

Mechanical and some other properties of acrylic-monomer-grafted nylon 6 fiber

Nylon 6 fiber, grafted with various vinyl monomers, viz., methyl methacrylate (MMA), ethyl methacrylate (EMA), and n-butyl methacrylate (n-BMA) were evaluated for their tensile, dye uptake, moisture regain, and solubility characteristics and compared to those of the parent nylon 6 fiber. The tensile properties (tenacity and initial modules) of the grafted samples show a decreasing trend and the percentage breaking elongation an increasing trend with the increase in the graft level in the case of all the three monomers compared to parent nylon 6 fiber. Disperse dye uptake also shows a decrease with the increase in the graft level in all the three monomers grafted only onto nylon 6 fiber. With the introduction of hydrophobic groups in the polymer backbone the moisture regain values decrease. This is true for all the samples and follows the order MMA-g-nylon > EMA-g-nylon > n-BMA-g-nylon. Solubility of the polymer in the solvent orthochlorophenol (OCP) and metacresol (MC) also decreases with the increase in the graft level for all the three monomers used in the following manner: OCP: EMA-g-nylon > n-BMA-g-nylon > MMA-g-nylon; MC: n-BMA-g-nylon > EMA-g-nylon > MMA-g-nylon.     

Mechanical reinforcement of cotton fabrics by grafting polymerization of acrylics

Grafting polymerization of acrylic monomers onto cellulose chains possesses a great potential for tailoring the properties of cellulose‐based materials. In this article, some results concerning the grafting polymerization of ethyl acrylate/methyl methacrylate (EA/MMA) 75/25 wt % on cotton fabrics are reported. The effectiveness of the grafting process as a method for the mechanical reinforcement of cotton without any modification of its handle is discussed. In addition, SEM observations were carried out to check the morphological modification occurring on cotton after the grafting reaction. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Photo-initiated vapor-phase grafting of acrylic monomers onto fibrous substrates in the presence of biacetyl

A novel vapor-phase process has been developed for grafting relatively volatile acrylic monomers onto various polymeric substrates, using photo-initiation by near ultraviolet irradiation in the presence of biacetyl vapors. With it, very even graft polymerizations on the substrates, with minimum amounts of homopolymerization, were found. Furthermore, there were essentially no changes in the tensile or aesthetic properties of the treated surfaces. The degree of photografting is dependent upon the chemical composition and porosity of the substrate, the volatility and reactivity of the monomers, prewetting of the substrate with a suitable wetting agent, and the conditions of irradiation used. The effects of various reaction parameters on the photo-induced grafting of methyl acrylate, methyl methacrylate, and acrylonitrile on wool keratin are studied in detail. Increasing biacetyl and monomer flow rates and flow times, irradiation times, and moisture content of the wool all caused progressive increases in the amount of polymer grafted to the wool, up to limiting values dependent on the reaction parameters involved and monomer used. In all instances, the amount of homopolymer found on the fiber was limited and remained essentially constant over the range of conditions studied. A series of acrylic monomers of different volatilities and reactivities including methyl acrylate, methyl methacrylate, butyl acrylate, acrylic acid, acrylamide, acrylonitrile, N,N-dimethylaminoethyl methacrylate, and 2,2,2-trifluoroethyl methacrylate was successfully grafted onto several hydrophilic and hydrophobic textile fibers (wool, cotton, rayon, nylon, acrylics, polyester, and polypropylene) and other polymeric surfaces such as filter paper, cellophane, and acetate film by this process. The wetting agents used included water, methyl and n-propyl alcohol, N,N-dimethylformamide, dimethylsulfoxide, benzene, and chlorinated hydrocarbon solvents.     

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.     

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.     

Grafting of formaldehyde-crosslinked and cyanoethylated cotton cellulose with acrylate monomers

Formaldehyde-crosslinked cotton and cyanoethylated cotton were grafted with methyl, ethyl, and n-butyl acrylates and methyl methacrylate using ceric ion as initiator. It was observed that the graft yields for formaldehyde-crosslinked cotton were significantly higher than those for native cotton. An increase in the bound formaldehyde resulted initially in a decrease in molecular weight of grafts; but later on, an increase was observed. In the case of cyanoethylated cottons, increasing the degree of substitution resulted in increase in graft yields. Molecular weights of the grafts increase up to a D.S. of 0.3, after which they decrease. These results are interpreted in terms of rates of initiation and termination being influenced by production of additional sites due to swelling of cellulose fibers.     

Radiation-induced polymerization of methyl methacrylate and alkyl acrylates at high dose rate

Polymerization of methyl methacrylate and methyl, ethyl, and n-butyl acrylates was carried out in a wide range of dose rate, 10–10⁶ rad/s by γ-ray and electron beam irradiation. With methyl methacrylate and n-butyl acrylate, and steady-state kinetics in radical polymerization was maintained in an entire dose rate range at about the initial stage of the polymerization. With methyl and ethyl acrylates, the rate of polymerization increased much less markedly than expected from the square root law and the molecular weight decreased much less gradually with dose rate. In all these monomers it was found that autoacceleration of the rate of polymerization due to gel effect becomes vague at high dose rate. Two-peaked molecular weight distribution was observed for the polymers obtained at high dose rate.