Gamma-irradiation processing

3 Gamma-irradiation processing Process diagram and description 

Quality-control tests and important process variables 

Important material and process variables for y-processing include 

Little process modelling has been developed due to the low industrial usage of y-irradiation processing for reactive polymers. However, many researchers are examining cure models for promising materials. 

Alessi et al. (2005) examined the y-irradiation and electron-beam processing of an epoxy-resin system in the presence of a photoinitiator. They showed that increasing the irradiation dose frequency and photoinitiator concentration greatly increases the temperature reached by the samples. The increase in temperature of the system during irradiation is related to the balance between the heat-evolution rate, due to both polymerization reaction and radiation absorption, and the rate of heat release towards the environment. High dose rates and high photoinitiator concentmtions increase the reaction rate and the difference between the heat produced and the heat released to the environment (Alessi et al. (2005). 

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Choi, J. I., Kim, J. H., and Lee, J. W. (2011). Physiological properties of tuna cooking drip hydrolysate prepared with gamma irradiation. Process Biochem. 46,1875-1878. 

Halls N.A. 1991. Gamma-irradiation processing. In Irradiation effects on polymers. D. Clegg and A. Collyer, Eds. New York Elsevier. 

Polyethylene and polystyrene are examples of plastics subject to environmental stress cracking. Crack resistance tests have shown that surfactants, alcohols, organic acids, vegetable and mineral oils, and ethers provide an active environment for stress cracking of polyethylene. Table 6 lists typical sterile devices and plastic materials used to fabricate them, while Tables 7-9 list the potential effects of sterilization processes on polymeric materials. The effect of gamma irradiation on elastomeric closures has been studied by the Parenteral Drug Association [15]. 

Colombo, P. et al., J. Polymer Sci., 1963, Bl(8), 435-436 Mixtures containing ratios of about 20 1 and 12 1 of ethylene haloalkene undergoing polymerisation under gamma irradiation at 308 krad/h exploded violently after a total dose of 50 krad. Dose rate and haloalkene cone, were both involved in the initiation process. 

The two-step process of epitaxial polymerization has been applied to symmetrically substituted diacetylenes First, the monomers have been crystallized epitaxially on alkali halides substrates from solution and the vapor phase. The oriented monomer crystals are then polymerized under the substrate s influence by gamma-irradiation. The diacetylenes in this study are 2,4-hexadiyn-l,6-diol (HD) and the bis-phenylurethane of 5,7-dodecadiyn-l,12-diol (TCDU). The polydiacetylene crystal structures and morphologies have been examined with the electron microscope. Reactivity and polymorphism are found to be controlled by the substrate. 

ISO/ASTM 51204 Standard Practice for Dosimetry in Gamma Irradiation Facilities for Food Processing... 

The effect of radiolysis on complexed solutions proposed for the FPEX process was investigated. The calixarene BOBCalixC6 was present with substi-tuted-18-crown-6, aromatic fluoro-propanol as modifier, and trioctylamine in aliphatic diluents (35). The effect of gamma irradiation was negligible up to 0.02 MGy. An important change of coloration and the appearance of a third phase was observed, but due to the nitration of the modifier. Instead of the BC-6 and oct-MC6 calixarenes, which presented a decrease of Cs extraction after radiolysis, the presence of alkylated phenyl moieties provided protection for the Cs site. 

Cie la, K., Roos, Y., Gluszewski, W. 2000. Denaturation process in gamma irradiated proteins studied by differential scanning calorimetry. Radiat Phys Chem 58 233-243. 

TR 11 Sterilization of Parenterals by Gamma Irradiation, 1988 TR 13 Fundamentals of an Environmental Monitoring Program, 2001 TR 22 Process Simulation Testing for Aseptically Filled Products, 1996 TR 26 Sterilizing Filtration of Liquids, 1998... 

The interaction of blood with PVC-P based on a phthalate and trimellitate plasticiser has shown that there is a higher reactivity for the trimellitate, which correlated with the plasticiser distribution at the polymer surface (316). Another important aspect is for the medical packaging to be suitable for sterilisation of the contents. Details are available of improving the gamma irradiation stability of PVC-P in order to retain colour (447). In addition to unacceptable colour formation, excessive shifts in pH and extractables can occur in inappropriately stabilised PVC-P (301). An additive system, based on materials approved for medical use, has been developed to give low extractables and low blush with good colour and processability (239). The effects of different plasticisers... 

Aging process in silk, acceleration, 16 Alanine, ESR spectrum after gamma-irradiation, 366,367/... 

PVA was widely used as a matrix for preparation of nanocomposites due to its easy processability, high clarity and biocompatibility. Ag-PVA nanocomposites were prepared by reduction of Ag" ions in PVA aqueous solutions using gamma irradiation followed by solvent evaporation. Ag-PVA hydrogel nanocomposite was obtained by simultaneous reduction of Ag" and cross-linking of PVA by yirradiation. 

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