Radiation grafting of vinyl monomers onto wood pulp cellulose. II

The effect of radiation dose rate and beating time on the mutual radiation grafting of styrene to unbleached and bleached kraft wood pulp was studied. Companion studies on the effect of beating time, peroxidation grafting, and order of monomer addition on the preirradiation graft copolymerization of acrylamide and diethylaminoethyl methacrylate were conducted on bleached wood pulp. The grafting rate of styrene increased with dose rate, but the kinetics suggests a significant diffusional resistance to the observed grafting rate. The per cent graft measured at fixed grafting conditions decreased markedly as pulp beating (effected prior to grafting) was increased. It is suggested that the decrease in grafting with beating is due to an increase in the accessibility and swelling of the beaten fibers. Dimethylaminoethyl methacrylate appeared to inhibit the grafting of acrylamide, and double grafting had to be used to graft both hydrophilic polymers to the pulp. The mechanical properties of high-yield pulp and groundwood were improved by the addition of the grafted pulps. The double grafts appeared to show promise as fibrous beaten additives for dry strength improvement. The styrenegrafted pulps were found not to respond at all to the beating process.     

Radiation grafting of vinyl monomers onto wood pulp cellulose. Part I

The effect of dose, dose rate, monomer type, and monomer concentration on the water transport behavior in grafted cellulose pulp and hand sheets was studied. At low dose rates, grafting rates of styrene onto wood pulp were less with hand sheets than with the pulp itself. Grafting was also found to be decreased by increasing the dose rate. Grafting mixtures of styrene and acrylonitrile gave better yields than styrene alone. Excellent grafting yields were obtained by treating the pulp or hand sheets with water before adding vinyl monomers. In this way, solvents such as dioxane could be eliminated from the grafting mixture. The hand sheets, grafted with mixtures of acrylonitrile and styrene, had good mechanical properties although less than the corresponding ungrafted sheets. Grafting decreased the moisture regain in pulp and hand sheets. Gamma irradiation of wood pulp under ambient conditions without additives reduced the water sorption considerably.     

Radiation induced grafting of mixed monomers onto polyester and polypropylene fibers

Grafting of the mixture of acrylamide and acrylic acid onto polyester and polypropylene fibers and mixture of acrylic acid and methacrylic acid onto polypropylene by the radiation method are reported. It is observed that when pure acrylamide was used for grafting, the grafting extent was small, whereas when the mixture was used, the amount of acrylamide content in the copolymer was found to be more than the feed ratios. The results are explained on the basis of chain transfer mechanism. With methacrylic acid and acrylic acid mixtures, the rate of grafting decreased with the increase in the concentration of acrylic acid in the feed ratio, and this has been explained on the basis of the formation of either a 3-dimensional network structure or a highly branched structure involving backbone polymer molecules with acrylic acid, which prevents the diffusion of the monomer from the solution phase to the swollen phase.     

Plasma-induced hydrogel grafting of vinyl monomers on polypropylene

Polypropylene (PP) film was plasma-treated using a 13.56 MHz direct plasma with argon, nitrogen, and oxygen as the plasma-forming gases. The three gases induced very different changes on the PP film surface, which were studied using contact angle measurements. Because of its degrading and oxidative effect, oxygen plasma pretreatment was not used for the homogeneous grafting of acrylic acid and acrylamide. Nitrogen plasma treatment did not lead to the formation of stable peroxides on the film surface and did not undergo grafting reactions. This may be due to the types of radicals and functional groups created on the surface during the plasma treatment. Finally, argon plasma pretreatment was found to be the most effective for the grafting of vinyl monomers. The amount of grafted poly(acrylic acid) was shown to be proportional to the concentration of peroxides created by argon plasma treatment.     

Electroinitiated emulsion polymerisation of vinyl monomers. III. Homopolymerisation and copolymerisation with vinyl acetate

Of the monomers studied, vinyl acetate and vinyl n-caproate are the only ones capable of electroinitiated homopolymerisation in aqueous acidic emulsion. Water solubility does not appear to be the overriding consideration. Activity of the radical would seem to be most important. Copolymerisation with monomers not undergoing homopolymerisation in this system produces good yields of copolymers low in vinyl acetate concentration.     

Half-sandwich ruthenium complexes for the controlled radical polymerisation of vinyl monomers

Ruthenium complexes of the type [RuX(Cp^#)(PPh₃)₂] (X=Cl and H; Cp^#=Cp, Cp*, indenyl, and carboranyl) catalyse the radical polymerisation of styrene and n-butyl acrylate, and both the catalyst activity and the degree of control of the polymerisation strongly depend on the Cp^# ligand and the monomer.     

Radiation induced graft copolymerization of vinyl monomers and their binary mixture onto rayon fibre

Ethyl acrylate (EA), Vinyl imidazole (VI), and their binary mixture have been copolymerized onto rayon in aqueous medium by mutual method using γ-radiation. The graft yield has been determined as a function of different reaction parameters such as total dose, concentration of vinyl monomers, and amount of water. Effect of surfactant (1-octane sulfonic acid, sodium salt) has been studied on the percentage of grafting of EA, VI, and (EA + VI). A plausible mechanism has been suggested to explain the observed behavior of the surfactant on grafting. Water retention and moisture regain of the grafted film was determined at appropriate relative humidity. The graft copolymers have been characterized by IR spectroscopy and scanning electron microscopic methods. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

An investigation into the effects of graft polymerisation of vinyl monomers to wool

The grafting of vinyl monomers to wool to confer shrink-resistance can have a number of side-effects, notably changes in dye uptake, tensile behaviour and handle. This work investigated these phenomena as a method of improving specific fibre properties. In addition, an attempt was made to develop a system of industrial, rather than purely scientific, significance. Several systems were examined, in particular a highly efficient and selective system using the redox couple potassium bromate and cobalt diacetate, with monomers such as methyl-, ethyl-and butyl-methacrylate. The effects of co-solvents such as acetone and diethyleneglycol monobutylether were also studied. It was found that both dye uptake and tensile strength could be significantly improved by relatively low levels of grafting without deleterious effects on handle. A novel ‘limiting volume’ model was developed to describe the various stages through which the grafting process proceeds, which explains the observed results, particularly at high levels of grafting where polymer growth is ‘forced’ onto the fibre surface.     

Graft copolymerization of vinyl monomers on modified cotton. IV. Ceric-induced grafting on vinyl monomers on cellulose bearing different substituents

The influence of introducing various functional groups into the cellulose molecule on its susceptibility toward grafting with vinyl monomers such as acrylonitrile and methyl methacrylate using the Ce(IV)–cellulose redox system was studied. While cellulose bearing either cyanoethyl or carboxymethyl groups showed higher graft yields, cellulose bearing both groups showed lower yields. Presence of acrylamidomethyl groups in the cellulose molecule reduced its reactivity to grafting. The same holds true for cellulose bearing acrylamidomethyl groups along with carboxymethyl groups. On the other hand, introducing carbamoylethyl groups in the cellulose molecule enhances significantly the susceptibility of cellulose toward grafting. This is also observed with cellulose bearing cyanoethyl and carboxyethyl groups. Treating cellulose with N-methylolacrylamide in alkaline medium seems to produce a crosslinked cellulose with lower reactivity to grafting. The results obtained with the different substrates were discussed on the basis of the change in the physical and/or chemical structure of cellulose brought about during its modification as well as on the nature of the substituent groups introduced. The mode of Ce(IV) attack on cellulose was also clarified.     

Factorial experimental design for grafting of vinyl monomers onto natural rubber latex

Graft copolymerization of styrene (St) and methyl methacrylate (MMA) in the presence of natural rubber latex using cumene hydroperoxide/tetraethylenepentamine redox initiator system was prepared at various process variables. The synthesized graft copolymers were purified and then characterized by Fourier transformed infrared spectroscopy analysis. A full 2⁴ factorial experimental design was applied to study the effect of various process variables on grafting efficiency. The following four independent variables considered to be mainly affecting the grafting efficiency were reaction temperature, rubber‐to‐monomer ratio, St‐to‐MMA ratio, and initiator amount used in the secondary polymerization. It was shown in this study that the reaction temperature significantly influenced the grafting efficiency, increasing as the temperature was increased. The amount of grafting increased with increasing rubber‐to‐monomer ratio and St‐to‐MMA ratio, whereas the amount of grafting decreased with increasing amount of initiator. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 455–463, 2004     

Grafting of polypropylene fibers. I. Radiation grafting of vinyl monomers,dyeing, and hydrophilic characteristics of the grafted polymer

Radiation-initiated grafting of methacrylic acid, acrylonitrile, and vinyl acetate on polypropylene fibers and the moisture content and dyeing characteristics of the grafted fibers have been reported. The extent of grafting with methacrylic acid is quite large when compared to acrylonitrile and vinyl acetate. The grafted fibers show an increase in moisture content with increase in the amount of graft. In general, the dyeability with disperse dyes increases due to grafting. In the case of cationic dyes, the polypropylene fibers grafted with methacrylic acid and acrylonitrile alone could be dyed.     

Emulsion polymerisation of highly water-insoluble monomers

Contrary to an earlier report, monomers (e.g. p-tert-butylstyrene and octadecyl methacrylate) which are less soluble in water than styrene have been found to polymerise in emulsion using persulphate initiation. At 60°C, the order of the Interval II polymerisation rate of octadecyl methacrylate is 0.48 in persulphate concentration and 0.68 in sodium dodecyl sulphate concentration. The rate is increased by addition of methanol to the aqueous phase. Unlike styrene, p-tert-butylstyrene could not be polymerised in aqueous suspension by persulphate in the absence of emulsifier. High emulsifier-monomer ratios were used in these experiments so that it is possible that mini-emulsion droplets were a significant reaction locus.     

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.     

Role of choline formate ionic liquid in the polymerization of vinyl and methacrylic monomers

Polymerizations of vinyl and methacrylate monomers (2‐hydroxyethyl methacrylate, styrene, and methyl methacrylate) were carried out in a choline formate ionic liquid at room temperature without the addition of peroxide‐based initiators. Choline formate acted as both an initiator and a solvent and produced high‐molecular‐weight polymers. Gel permeation chromatography and electron paramagnetic resonance measurements indicated that the polymerizations predominantly occurred by a free‐radical mechanism. This method of polymerization provides an alternate route to eliminate the use of toxic initiators and solvents. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Chemically induced graft copolymerization of vinyl monomers onto cotton fibers

We investigated the chemically induced graft copolymerizations of acrylic acid (AA), acrylamide, crotonic acid, and itaconic acid (IA) onto cotton fibers. Benzoyl peroxide was used as an initiator. The effects of grafting temperature, grafting time, and monomer and initiator concentrations on the grafting yields were studied, and optimum grafting conditions were determined for the sample material. The maximum grafting yield value obtained was 23.8% for AA. Swelling tests, Fourier transform infrared spectroscopy, and scanning electron microscopy analyses of grafted and ungrafted fibers were also performed to characterize fiber properties. IA‐grafted fibers were measured as the most swollen fibers, with a swelling value of 510%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2343–2347, 2006     

Ultrafiltration membranes obtained by grafting hydrophilic monomers onto poly(vinyl chloride)

The grafting of vinylacetate (VAc) or hydroxyethylmethacrylate (HEMA) onto poly(vinyl chloride) (PVC) has been performed by means of γ-rays or chemical initiators. The grafted polymer so obtained has been separated by selective extraction and submitted to IR spectroscopy in order to check the amount of grafting. The grafting percentage was measured as a function of the grafting conditions. Using the above-mentioned polymer, dissolved again in DMF, asymmetric ultrafiltration membranes have been prepared by the phase inversion technique. The membranes have been tested with Dextran solutions. Their performances have been studied as functions of the grafting amount. The values of rejection and permeating flux demonstrated the effectiveness of the treatment in enhancing the performances of PVC ultrafiltration membranes.     

Elucidation of the nanoparticle effect on the grafting of vinyl monomers onto cotton fabric

The grafting emulsion polymerization of vinyl monomers onto cotton was carried out in the presence of double‐modified montmorillonite clay. The obtained results show that grafting with glycidyl methacrylate/montmorillonite gave a higher rate of grafting than grafting with methyl methacrylate/montmorillonite in all clay percentages, and also, the grafting yield of glycidyl methacrylate monomer onto cotton in the presence of montmorillonite clay had a higher value than that in the absence of the clay for all factors studied. Cotton grafted with glycidyl methacrylate/montmorillonite with a graft yield of about 50% was prepared according to the emulsion polymerization technique and was treated with different concentrations of dibutylamine solutions ranging from 1 to 4%. The obtained samples were characterized according to nitrogen content, thermal stability, scanning electron microscopy, mechanical properties, water absorption, and color strength according to acid, basic, and reactive dyes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Crosslinking and grafting ethylene vinyl acetate copolymer with accelerated electrons in the presence of polyfunctional monomers

In this study, we have studied the effects of polyfunctional monomers (PFMs) on physical properties of ethylene vinyl acetate (EVA) copolymer crosslinked with electron beam (EB) or peroxides. The PFMs used were triallylcyanurate, triallylisocyanurate, trimethylolpropane trimethacrylate, zinc diacrylate, and ethylene glycol dimethacrylate. Using PFMs has led to (1) optimum cure time t ₉₀ decrease from 19′25″ to 17′30″–18′45″, (2) scorch time increase from 2′ to maximum 3′45″, (3) increasing the crosslink density of peroxide or EB-cured systems by increasing the efficiency of productive radical reactions. The most efficient PFM for EVA copolymer blends has been triallylisocyanurate. Tensile strength and tear strength of samples crosslinked with EB for all irradiation doses are significantly better than those obtained for samples crosslinked with peroxides (differences up to 190%). The results show that EB irradiation gave the best results