Polymer processing radiation methods

The initiation of polymerization by ultraviolet radiation has been of particular interest in the study of free radical processes [1,2]. The test tube demonstration described here is simple and may be used to evaluate the polymerizabil-ity of new monomers or to study some of the physical properties of a polymer. Although the method is particularly effective for acrylic and methacrylic monomers, it may also be applied to the polymerization of a wide range of vinyl -type monomers. 

Trradiation provides a powerful method for modifying polymers, and radiation-initiated processes such as crosslinking and graft coply-merization have attracted considerable interest in past years. Although only a few irradiation processes are currently used in industry, it seems most likely that this field will grow and expand actively in the not-too-distant future. 

Chmielewski, A.G., M. Haji-Saeid and S. Ahmed. 2005. Progress in radiation processing of polymers. Nucl Instrum Methods Phys Res B 236 44-54. 

Grafting induced by radiation methods can be achieved either after preirradiation or simultaneously during the irradiation. In the latter, polymer film is embedded in a monomer solution which is directly grafted during the irradiation process. 

The scission and crosslinking reactions have the greatest effect on the material properties of polymers and measurement of the radiation chemical yields of these two processes is very important for quantifying degradation of polymers by radiation(4). The main methods used to determine the yields of scission and crosslinking are listed in Table 2. 

Ryan, A.J., Elwell, M.J., Bras, W. Using synchrotron radiation to study polymer processing. Nucl. Instr. Methods Phys. Res. B97, 216-223 (1995)... 

Many challenging industrial and military applications utilize polychlorotriduoroethylene [9002-83-9] (PCTFE) where, ia addition to thermal and chemical resistance, other unique properties are requited ia a thermoplastic polymer. Such has been the destiny of the polymer siace PCTFE was initially synthesized and disclosed ia 1937 (1). The synthesis and characterization of this high molecular weight thermoplastic were researched and utilized duting the Manhattan Project (2). The unique comhination of chemical iaertness, radiation resistance, low vapor permeabiUty, electrical iasulation properties, and thermal stabiUty of this polymer filled an urgent need for a thermoplastic material for use ia the gaseous UF diffusion process for the separation of uranium isotopes (see Diffusion separation methods). 

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. 

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