Polymer Surfaces radiation sources

Other techniques utilize various types of radiation for the investigation of polymer surfaces (Fig. 2). X-ray photoelectron spectroscopy (XPS) has been known in surface analysis for approximately 23 years and is widely applied for the analysis of the chemical composition of polymer surfaces. It is more commonly referred to as electron spectroscopy for chemical analysis (ESCA) [22]. It is a very widespread technique for surface analysis since a wide range of information can be obtained. The surface is exposed to monochromatic X-rays from e.g. a rotating anode generator or a synchrotron source and the energy spectrum of electrons emitted... 

Emission infrared spectroscopy is used for thin films and opaque polymers. The sample is heated so that energy is emitted. The sample acts as the radiation source and the emitted radiation is recorded giving spectra similar to those of classical FTIR. In some cases, IR frequencies vary because of differences in the structures at different depths and interactions between surface and interior emissions. 

Structuring of polymer films attracts considerable attention, and various radiation sources have been employed to crosslink selectively suitable polymers for, e.g., waveguide fabrication [99], Incompatible polymer blends have been forced into certain demixing morphologies along pre-patterned surfaces [55], Persistent structures could be formed by laser radiation in various nonabsorbing polymer solutions, such as polyisoprene in n-hexane [57, 58],... 

Radiation grafting [83, 84, 85, 86, 87, 88, 89] is a very versatile and widely used technique by which surface properties of almost all polymers can be tailored through the choice of different functional monomers. It covers potential applications of industrial interest and particularly for achieving desired chemical and physical properties of polymeric materials. In this method, the most commonly used radiation sources are high-energy electrons, y-radiation, X-rays, U.V.-Vis radiation and, more recently, pulsed laser [90], infrared [91], microwave [92] and ultrasonic radiation [93]. Grafting is performed either by pre-irradiation or simultaneous irradiation techniques [94, 95]. In the former technique, free radicals are trapped in the inert atmosphere in the polymer matrix and later on the monomer is introduced into... 

Yet another boundary condition encountered in polymer processing is prescribed heat flux. Surface-heat generation via solid-solid friction, as in frictional welding and conveying of solids in screw extmders, is an example. Moreover, certain types of intensive radiation or convective heating that are weak functions of surface temperature can also be treated as a prescribed surface heat-flux boundary condition. Finally, we occasionally encounter the highly nonlinear boundary condition of prescribed surface radiation. The exposure of the surface of an opaque substance to a radiation source at temperature 7 ,-leads to the following heat flux ... 

Radiation-induced graft copolymerization using different radiation sources (electron beam, O.l-lOMev and cobalt source ( °Co)) has been widely experimented to chemically modify the surface of polymers because of its versatility and capabilities to treat a wide range of polymer surface through the choice of different fimctional monomers. 

Infrared radiation is a noncontact alternative for hot-plate welding. Infrared is particularly promising for higher-melting polymers, since the parts do not contact and stick to the heat source. Infrared radiation can penetrate into a polymer and create a melt zone quickly. By contrast, hot-plate welding involves heating the polymer surface and relying on conduction to create the required melt zone. 

Radiation grafting [22-27] is a very versatile technique by which surface properties of a polymer can be tailored through the choice of different monomers, the most common radiation sources used in this case being high energy electrons, y radiation, and UV and visible light. 

Samples may be introduced from the atmosphere into the spectrometer by using prepumped insertion locks and valves. Samples can be cooled or heated in situ and additional equipment for sample treatment, e.g. UV radiation sources, can be mounted on the spectrometer. Polymer samples may be studied directly in the form of films or powder. Powders can be mounted on double-sided Scotch Tape. Surface coatings can be investigated without the need to separate the coating from the surface. The minimum thickness of the sample is in the range of 100 A and area 0.2 cm. The ESCA technique is essentially nondestructive. 

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