Radiation-induced modifications

RADIATION-INDUCED MODIFICATION 31.2.1 Radiation Types and Sources... 

Parameters/Units Used in Electron Beam Radiation-Induced Modification OF Materials... 

Radiation-induced modification or processing of a polymer is a relatively sophisticated method than conventional thermal and chemical processes. The radiation-induced changes in polymer materials such as plastics or elastomers provide some desirable combinations of physical and chemical properties in the end product. Radiation can be applied to various industrial processes involving polymerization, cross-linking, graft copolymerization, curing of paints and coatings, etc. 

Among the various radiation-induced modifications, the EB-processing of polymers has gained special importance as it requires less energy, is simple, fast, and versatile in application. The overall properties of EB-irradiated polymeric materials are also improved compared to those induced by other ionizing radiation. 

Understanding of the mechanism of radiation degradation of polymer molecules is essential for development of improved and new industrial processes, for radiation-induced modification of polymer properties, and for selection of polymers for use in radiation environments. This means that the detailed chemical reactions resulting from absorption of radiation must be known. This fundamental understanding must enable us to relate the chemical structure of a polymer to changes in its chemical, physical and material properties. Such structure-property relationships require a great deal of research work, but they are the key to further advancement on a scientific basis. 

Temperature is an important parameter in radiation degradation, yet remarkably little experimental work has been reported for irradiation at other than ambient temperature. The transition temperatures, Tg and Tm, of the polymer are as important in the radiolysis as they are for the properties. The irradiation temperature can be deliberately varied to enhance the radiation-induced modifications of polymers and should not be regarded as just an environmental property. Similarly, once the sensitization to, or protection from, radiation degradation by small molecule additives is understood — as a function... 

Fig. 14 shows Rexp/Rcanv as functions of q q for ECS and NCS. The effect revealed by NCS is between 25% and 50%, and increases with increasing momentum transfer, (i.e. decreasing scattering time) see Eq. (1). The ECS data reveal a corresponding "anomalous" decrease of Rexp of 15 - 45%. For the ECS experiment it was checked that no radiation induced modifications of the film occurred for doses required to obtain good quality spectra [Vos... 

The second part of the dual switch design requires the selective, radiation-induced modification of this film back to a water soluble state. This goal may be achieved through incorporation of an acid cleavable site within the carboxylic acid crosslinker or solubility modifier. Radiation-induced generation of a catalytic amount of acid in selected areas of the resist film would then allow the selective destruction of the insolubilizing linkages. 

RADIATION INDUCED MODIFICATION OF POLYETHERURETHANE TUBES WITH HEMA AND ACRYLAMIDE... 

Synthesis of polymers which undergo radiation-induced modification of side-chain polarity in a catalytic process. 

Inhibiting effect of DM arises from the presence of aromatic rings in its structure. The aromatic compounds are known to influence the radiation-induced modification by effect of resonance energy dissipation [24-25]. In the structural formula of DM, heteroatoms, such as sulfur and nitrogen are also present. The sulfur moieties are known to inhibit the effect of ionizing radiation action on matter [26-27], due to the fact that sulfur groups act as sinks of the radiation energy [28]. 

Radiation-Induced Modifications of Alfylamino-Substituted Pofyphosphazenes... 

---