UV radiation sources

UV radiation source, before a subsequent layer is deposited. At the end of the building process, the cured Supporting material is removed manually or with the aid of water. 

In most cases spectrophotometers are equipped with two independent radiation sources UV and VIS. The UV source is usually a deuterium- or xenon lamp that emits radiation in the range of 180 00 nm or 190-750 nm, respectively. The development of the UV radiation sources has been reviewed [13]. 

Apart from a suitable UV-curing adhesive, suitable UV-radiation sources are required, too, which are available in the form of flashlights or continuous lines. To achieve optimum curing, it is very important to adapt the UV-radiation precisely to the adhesive to be cured (Section 9.3.3). 

Pressure-sensitive adhesives are the essential components of adhesive tapes and labels. They are polymers with permanent tack, usually applied on substrates (plastic/metal films, siliconized papers). To enhance their tack, compounds with high inherent tack are added, for example, resins, plasticizers. Pressure-sensitive adhesives reach their adhesion on the material to be bonded by contact pressure, from which the term pressure-sensitive adhesive (PSA) derives. Apart from electron radiation, also UV-radiation curing described in Section 4.3.2 is applied in adhesive tape manufacturing. The monomer molecules to be polymerized are applied, in liquid form, to the substrates to be coated by rolling and are continuously cured to a polymer layer within seconds under a UV-radiation source. Depending on their composition, predetermined adhesion values can be adjusted. The adhesive tapes can be subsumed under the systems shown in Figure 5.4 ... 

Deuterium lamps are commonly used as a UV radiation source in the range 200-400 nm and tungsten incandescent lamps as sonrces for the visible and NIR regions covering the range 400-2500 nm. For the NIR work, the sonrce is operated at 2500-3000 K, which results in more intense radiation. 

The sample can be exposed to UV and visible radiation in sequence. This might be performed in two separate chambers. One chamber could have a visible radiation source and the second a UV radiation source. 

UV oxidation methods were proposed during the same period as WCO, although they were not adopted until the 1970s. As with WCO, inorganic carbon is removed from the seawater prior to oxidation. Typically, water samples were exposed to a UV radiation source light via a quartz capillary coiled around the light source. Some UV radiation procedures included the addition of a chemical oxidant. 

The parts are exposed by UV light, through a photomask in contact with the coating. UV radiation sources with mercury or mercury-xenon collimated light are preferred, using equipment such as that shown in Figure 7.13. The optimum exposure energy is determined from an exposure-time series that yields the correct size vias or photoformed holes in the dielectric after development (Table 7.6). 

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. 

From the solar spectrum passing through the earth s atmosphere, it is evident that no radiation with a wavelength < 300 nm is transmitted by the atmosphere. This has important practical implications in that the number and type of photochemical reactions which may occur are thereby severely restricted, in comparison to the case when polymer samples are exposed to radiation from UV radiation sources. Since the energy of (sun)light (E ) is inversely proportional to the wavelength, i.e. ... 

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