Gamma radiation grafting

F. R. Hartley. Gamma-radiation grafting a novel approach for the preparation of robust and highly selective supported metal complex catalysts. British Polyrrier J., 16 (4), 199-204,1984. 

Alternatively, the film is placed between two perforated lead plates and grafted with monomer M by the mutual method. After grafting, the film is now placed between the two perforated lead plates taking precautions that only the ungrafted portions of the grafted film are exposed to gamma radiations in the presence of monomer M2. Schematically, the preparation of the mosaic membrane is shown in Fig. 2. 

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. 

Photodegradation of polyethylene waste can be markedly accelerated via its grafting with acrylamide [98], In contrast, photostabilization of polyethylene and polypropylene can be achieved as a result of the grafting of 2-hydroxy-4-(3-methacryloxy-2-hydroxy-propoxy) benzophenone using gamma radiation [ 147], In this case, the grafted compound acting as a U V stabilizer is chemically bound to the backbone chain of the polymer and its evaporation from the surface can be avoided. 

Paraffin gauze dressing Perforated film absorbent dressing Polyurethane foam Burns, scaids, grafts Postoperative wounds Burns, ulcers, grafts. Any combination of dry heat, gamma-radiation and ethylene oxide... 

Graft copolymerisation of styrene on partially carboxymethylated cotton using gamma radiation. 

Radiolysis Effects. Radicals formed in solvent (SH) and trunk polymers (PH) are important in the grafting of monomers (MH) with gamma radiation. With polymers such as polyethylene, grafting sites are formed by direct bond rupture (Equation 1). Additional sites are also... 

Xerogels Ag, Au Two steps (1) gamma radiation initiation of metal-particle growth in a solution containing metal ions and multifunctional silanes (2) xerogels with metal clusters grafted on an oxide network prepared via hydrolysis and condensation 76... 

Gamma-radiation 3 megarads in air. Redox catalyst 0.01% Fe2+. Grafting temperature 25 °C. 

Waksman R, Ajani AE, White RL, et al, Intravascular gamma radiation for in-stent restenosis in saphenous-vein bypass grafts. N Engl J Med 2002 346 1194-11 99. 

Further work on the mechanism of the acid enhancement in both UV and gamma ray grafting is reported. The copolymerisation of styrene in methanol and dioxan to cellulose is used as model system. Acid enhances grafting and homopolymer formation in both radiation systems. Analysis of the homopolymer from the grafting runs indicates that acid reduces the chain length, but increases the numbers, of grafted chains. 

In the present work, further mechanistic data for the acid effect in both UV and gamma radiation systems are reported, particularly molecular weight studies on the species present in the grafting solutions. The significance of these acid effects in possible commercial applications of the resulting copolymers of cellulose is also briefly mentioned. 

Effect of Acid as an Additive on UV and Radiation Grafting. Previous studies have shown that mineral acids can enhance the radiation grafting of styrene to cellulose under certain radiation conditions. W The results of analogous experiments in photografting are shown in Table III, and compared with the corresponding gamma ray data. In... 

Mechanistically the role of acid In enhancing gamma radiation copolymerization Involves a number of competing processes. In previous work In this field with cellulose (i6), it has been suggested that acid at the concentrations used does not markedly affect the precipitation of the grafted chains or the swelling of the backbone polymer, especially with cellulose. Instead It has been proposed that part of the acid enhancement can be attributed to a radiation chemistry phenomenon Involving increased G(H) yields and thermallzed electrons (Equations 7 to 9). These processes can lead... 

Also within this category of application is the field of radiation grafting onto pre-existing polymeric substrates. E-beam or gamma sources can be used to initiate grafting onto a range of materials, for example poly(olefin)s, fluoropolymers, and cellulosics. The biocompatibility of poly(olefin)s can be greatly... 

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