Preirradiation grafting

Reactive species can be generated prior to monomer exposure (preirradiation grafting), during contact with monomer, or, after the polymer surface has been saturated with monomer and isolated (postirradiation grafting). The radiation-induced (y-ray and EB) graft copolymerization of AA and vinyl acetate monomer onto PE surface has been reported [170]. The grafted sheets show excellent bonding with an epoxy adhesive and enhanced adhesion with aluminum. 

Fig. 11. Extraction of PS homopolymer and unreacted PET from the reaction product obtained by the preirradiation grafting of styrene onto PET fibers...

The second method called "peroxidation" or "preirradiation" grafting is a two-step process. Polymer A is at first irradiated by itself in air. The resulting polymeric radicals react with oxygen to give peroxidic radicals which further react to form polymeric peroxides via a short chain reaction, analogous to conventional "auto-oxidation". 

S. Hohnberg, P. Holmlund, C.E. Wilen, T. KaUio, G. Sundhohn, and F. Sundhohn. Synthesis of proton-conducting membranes by the utilization of preirradiation grafting and atom transfer radical polymerization techniques. Journal of Polymer Science Part A Polymer Chemistry 40, 591-600 2002. 

Journal of Applied Polymer Science 94,No.6, 15thDec.2004p.2509-16 PREPARATION OF ANTIMICROBIAL SUTURES BY PREIRRADIATION GRAFTING OF ACRYLONITRILE ONTO POLYPROPYLENE MONOFILAMENT. III. HYDROLYSIS OF THE GRAFTED SUTURE Gupta B Jain R Anjum N H Singh Indian Institute of Technology... 

El-S.A. Hegazy, A.M. Dessouuki, A.M. Rabie and I. Ishigaki, Membranes obtained by preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene-perfluoro-vinyl ether), J. Polym. Sci., Polym. Chem. Ed. 1984, 22, 3673-3685. 

Radiation-induced graft polymerization can be classified into two techniques in terms of irradiation opportunity (1) simultaneous grafting, i.e., the mixture of a trunk polymer and a monomer is irradiated, and (2) preirradiation grafting, i.e., a trunk polymer is previously irradiated and then brought into contact with the monomer [56]. From a practical viewpoint, the preirradiation technique is preferable because of the negligible formation of homopolymers and easier control of the degree of polymerization. 

H. Yamagishi, K. Saito, S. Furusaki, T. Sugo and J. Okamoto, Comparison of Simultaneous and Preirradiation Grafting of Methyl Methacrylate onto a Porous Membrane, Chem. Mater., 3 (1991) 987. 

Hegazy, E.S.A., El-Assy, N.B., Rabie, A.G.M. et al. 1984. Kinetic study of preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene-perfluorovinyl ether) copolymer. J Polym Sci Polym Chem. 22 597-604. 

Yang, J. and Hsiue, G. 1996. Synthesis of acrylic acid grafted silicone rubber via preirradiation graft copolymerization and its physical and dielectric properties. J Appl Polym Sci. 61 221-229. 

Zouahri, A. and Elmidaoui, A. 1996. Synthesis of perfluorinated cation exchange membranes by preirradiation grafting of acrylic acid onto ethylene-tetrafluoroethylene films. 7 PoZym Sci. 34 1793-1798. 

Preirradiation grafting (trapped radicals method) involves irradiation of the polymer under inert atmosphere or under vacuiun. As a result, the radicals are formed and remain trapped within the polymer matrix. These radicals subsequently initiate the grafting of a monomer. 

Fig. 3 Effect of low temperature storage on degree of grafting for the preirradiation grafting method [73]...

Styrenic L-prolinol-derived ligand A-Boc-60 was immobilized on chemical inert, mechanically stable polyethylene fibers by electron beam induced preirradiation grafting using styrene as a co-monomer to lead to polymer fiber 161 with a loading of 0.2 mmol/g... 

The only way to apply chemically bonded thin perfluorosulfonic acid layer onto the surface of an inert support is to graft perfluorinated functional monomers onto perfluorinated polymers. Some features of radiation-induced graft copolymerization of PFAVESF onto fluoropolymers were investigated. The studies showed that neither irradiation of a fluoropolymer-PFAVESF mixture (direct grafting) or interaction of PFAVESF with previously irradiated fluoropolymers (preirradiation grafting) yielded the grafted copolymers. It was assumed that this is connected with the low activity of PFAVE in radical polymerization. A special method has been developed for the synthesis of grafted copolymer. Previously irradiated fluoropolymer powders were used to prevent waste of PFAVESF. 

Gupta B, Jain R, Anjum N and Singh H, Preirradiation grafting of acrylonitrile onto polypropylene monofilament for biomedical applications I. influence of synthesis conditions . Radiation Physics and Chemistry, 75 (1), 2006, pp 161-167. 

Although considerable work has been reported using preirradiation grafting, the present treatment will be confined to the mutual or simultaneous procedure since by this latter technique, much lower doses are needed to accomplish a particular percentage graft The simultaneous method is also amenable to the use of additives to accelerate copolymerization. The additives to be discussed in this paper include solvent, mineral acid and polyfunctional monomers for the grafting of styrene monomer to polyethylene and polypropylene films in the presence of gamma radiation ... 

In the case of preirradiation with Co y-rays, the effects of reaction time, dose and temperature in preirradiation grafting of styrene onto PHB have been investigated in detail. The degree of grafting X increased with the preirradiation doses of up to 15kGy and temperatures up to 80°C (Fig. 6.3) [61]. 

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