Radiation grafting, efficiency

There are a number of important factors that must be considered before applying gamma radiation-induced grafting. These factors include the radiation sensitivity of the polymer/monomer system, radiation dose and dose rate, type and concentration of inhibitor, type of solvent or diluent, and monomer concentration. The effect of such parameters on the grafting efficiency during mutual grafting is given below. 

Homopolymerisation is the most undesired phenomenon associated with surface grafting and has remained the main drawback of the radiation-induced grafting systems. During the last two and a half-decades, different homopolymerisation inhibitors [192, 193, 194] have been employed in various grafting systems and their efficiencies evaluated. Some of the latest developments in improving the grafting efficiency and reducing associated homopolymerisation are presented herewith. 

Graft copolymers of starch and vinyl acetate (VA) have been prepared using Co60 irradiation.110 Near-quantitative conversions of monomer to polymer were reported when the radiation dose was l.OMrad, although the grafting efficiency was <50%. Lower radiation doses gave lower conversions and add-ons. When 10% methacrylate was added to the monomer mixture, grafting efficiency was improved to 70%. Selected copolymers were treated with methanolic sodium hydroxide to yield starch-poly(vinyl... 

A similarly poor efficiency in extraction can also be seen in Fig. 11, where the extraction result for the product obtained by the radiation grafting of styrene onto polyethylene terephthalate)(PET) fibers13 is shown. In this case the unreacted PET can be extracted after most of PS homopolymer has been extracted by repeated solution-precipitation of the sample. It should be mentioned here that the solution procedure is also necessary to extract the unreacted PET. Such a solution-precipitation procedure is also necessary for nylon-styrene13 and poly(vinyl chloride)-acrylo-nitrile14 graft products so as to remove the homopolymers to a sufficient extent. 

When high-energy radiation is used, the most important factor affecting the grafting efficiency is the radiation sensitivity of the monomer to be... 

The significant contribution of Nafion or perfluorosulfonic membranes to the cost of the fuel cells stacks and the high alcohol crossover levels that affect the fuel efficiency, prompted the development of radiation grafted proton exchange membranes based on poly(ethylene-tetrafluoroethylene) (ETFE) [172-178], PVdF [175], andPTFE [179]. The peroxy radicals produced on the base polymer by y-ray, electron- or proton-beam, react with styrene to form a co-polymer that is then sulphonated. 

Sheikh, N., Akhavan, A., Ataeivarjovi, E. Radiation grafting of styrene on starch with high efficiency. Radiat. Phys. Chem. 85, 189-192 (2013)... 

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