Cellulose radiation grafting

Several authors have discussed the ion exchange potentials and membrane properties of grafted cellulose [135,136]. Radiation grafting of anionic and cationic monomers to impart ion exchange properties to polymer films and other structures is rather promising. Thus, grafting of acrylamide and acrylic acid onto polyethylene, polyethylene/ethylene vinyl acetate copolymer as a blend [98], and waste rubber powder [137,138], allows... 

An effective method of NVF chemical modification is graft copolymerization [34,35]. This reaction is initiated by free radicals of the cellulose molecule. The cellulose is treated with an aqueous solution with selected ions and is exposed to a high-energy radiation. Then, the cellulose molecule cracks and radicals are formed. Afterwards, the radical sites of the cellulose are treated with a suitable solution (compatible with the polymer matrix), for example vinyl monomer [35] acrylonitrile [34], methyl methacrylate [47], polystyrene [41]. The resulting copolymer possesses properties characteristic of both fibrous cellulose and grafted polymer. 

Advanced development of ion-selective films has been attempted by radiation grafting of methacrylic acid on polyethylene films, and combination of this with cellophane are also being tested. Polyamide fleece impregnated with regenerated cellulose, is another option for zinc-silver oxide batteries. 

Radiation grafting is an extremely valuable one-step method for directly modifying the properties of polymers (y,2). The technique has been used with a wide variety of naturally occurring macromolecules such as wool (3) and cellulose (4) and also with many synthetic polymers, particularly the polyolefins (2, 5, 6) ... 

A theory for this acid effect has been developed essentially from the wool and cellulose work (3,4). Recently, in a brief communication, we reported analogous acid enhancement effects in the radiation grafting of monomers such as styrene in methanol to nonpolar synthetic backbone polymers like polypropylene and polyethylene (5). In the present work, detailed studies of this acid enhancement effect are discussed for the radiation grafting of styrene in various solvents to polyethylene. The results are fundamentally important since most of the experiments reported here have been performed in solvents such as the low molecular weight alcohols which, unlike cellulose and wool systems, do not swell polyethylene. 

Acid enhancement in the radiation grafting of styrene in methanol to cellulose (4), wool (3) and in preliminary work with the polyolefins (5 6) has been proposed as being predominantly due to such reactions. 

The most common material used is cellophane, which is a cellulose film, which acts as a membrane and is capable of resisting zinc penetration. The cycle life of cells utilizing this material is severely limited due to the hydrolysis of the cellophane in alkaline solution. Various methods have been tried to stabilize cellulose materials, such as chemical treatment and radiation grafting to other polymers, but none have, as of now proved economically feasible. The most successful zinc migration barrier material yet developed for the nickel—zinc battery is Celgard microporous polypropylene film. It is inherently hydrophobic so it is typically treated with a wetting agent for aqueous applications. 

Radiation Grafting of Miscellaneous Monomers onto Cellulose... 

Finally, various attempts have been reported to interpret the kinetics of radiation grafting. The study by Mock, and Vanderkooi (123) concerned the mutual radiation grafting of styrene from the vapor phase to ethyl cellulose film at 50° C. The radical flux was determined separately using electron spin resonance. The kinetic scheme rigorously took account of the diffusion controlled nature of the reaction and the appropriate diffusion constants were separately determined (124). The value for the ratio of for the graft polymerization was determined as... 

Mock, R. A., and W. N. Vanderkooi Kinetics of mutual radiation grafting of styrene onto ethyl cellulose film. J. Polymer Sci. 56, 69 (1962). 

Molecular Weights and Average Number of Cellulose Molecules per Grafted Side Chain. Radiation Grafting of Styrene to Cellophane and Cotton (Taken from Krassig) Ref. 15. 

In the radiation grafting work, experiments were performed in spent fuel element and cobalt-60 facilities of the Australian Atomic Energy Commission, dose rates being determined by ferrous sulfate dosimetry (G(Fe)= 15.6). For the specific irradiations, which were carried out in quadruplicate, small strips (5 x 4cm) of cellulose (Whatman No. 41, W.R. Balston Pty. Ltd., double acid-washed chromatography grade) were equilibrated at 65% relative humidity for 24 h at 23 °C, folded into test tubes (16 x 1.2 cm), monomer solution (6ml) added to the tubes which were then lightly stoppered. After irradiation, the strips... 

Mechanism of Acid Effect in Radiation Grafting. In earlier studies (13,14,15,21) on the mechanism of the acid effect on radiation grafting of styrene (MH) in dioxan or methanol (SH) to cellulose(Cell-OH)the sequence of events depicted in Equations (1) - (9) was proposed to explain the phenomenon. Thus, cellulose can undergo bond... 

On the other hand, it might be desirable to reduce the hygroscopicity of certain polymers. J. C. Arthur deals with radiation grafting of vinyl monomers upon cotton cellulose. 

Methods for Enhancing Ultraviolet and Radiation Grafting of Monomers to Cellulose and Derivatives to Improve Properties of Value to Conservation... 

The influence of more than 100 organic media (solvents for the monomer) on radiation grafting of 2,4-dimethyl- and 2-methyI-5-vinylpyridine to cellulose (filter paper of various brands and degrees of grinding) was shown to be associated with two factors, namely cellulose swelling and specific interaction of the organic liquid with the monomer and with cellulose75,76 ... 

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