Formulations, electron beam

Elemental chemical analysis provides information regarding the formulation and coloring oxides of glazes and glasses. Energy-dispersive x-ray fluorescence spectrometry is very convenient. However, using this technique the analysis for elements of low atomic numbers is quite difficult, even when vacuum or helium paths are used. The electron-beam microprobe has proven to be an extremely useful tool for this purpose (106). Emission spectroscopy and activation analysis have also been appHed successfully in these studies (101). 

Ultraviolet Electron Beam Curing Formulations for Printing Ink, Coating and Paints, 3 Vols., SiTA Technology, London, 1991. 

A comprehensive review of radiation techniques in the formulation of biomaterials was published by Kaetsu. Substrate modification by electron beam was discussed by Wendrinski at the meeting of RadTech Europe 2001. ... 

In the past, electron beam radiation was applied to produce PSA exclusively however, recent improvements in UV curing technology (precise UV dose control, suitable photoinitiators) permit UV to be used to produce pressure-sensitive adhesives. PSA formulations can vary in consistency from low-viscosity liquids up to solids melting at 80°C (176°F). Therefore, applications may vary from screen printing to roll coating to melt extrusion. Coat weights for most PSA materials vary from 1 to 10 g/m. ... 

The cost of polymer irradiation depends on the type of polymer, formulation, and shape of the fabricated polymer. Upgrading polymers by electron beam radiation costs about 1 to 4 cents per pound. Some of this cost can be equalized through material saving in view of property improvement. Surface treatment might be as low as 0.1 to 0.2 cents per pound. 

Formulation of Resist Solutions. Forty grams of a Novolak resin was mixed with 10 g of the photoactive compound, and dissolved in 100 g of bis-2-methoxy-ethylether. After wafers were spin-coated, the samples were immediately placed on a hot plate at 82 C for 14 min. The formulation procedure of a composite resist of poly (2-methyl-1-pentene sulfone) in the Novolak resin is as follows the polysulfone was mixed with the resin (13 wt% solid), and then dissolved in 2-methoxyethyl acetate the films were spin-coated onto silicon wafers, and then baked at 100°C for 20 min prior to electron beam exposure. 

Starting from the vector model of a precessing spin, the polarization properties of an electron beam with electrons of spin (l/2)h are explained and then formulated... 

This transformation or conversion is accomplished by the addition of a chemically active compound known as a curing agent or catalyst. Depending on the particular details of the epoxy formulation, curing may be accomplished at room temperature, with the application of external heat, or with the application of an external source of energy other than heat such as ultraviolet (uv) or electron beam (EB) energy. 

Their use in adhesive systems is minimal because they are relatively brittle and higher in cost than aromatic resins. However, cycloaliphatic epoxy resins are used in cationi-cally cured epoxy adhesive formulations. These are cured via uv or electron beam (EB) radiation. 

Epoxy acrylates are also commonly used as oligomers in radiation-curing coatings and adhesives. However, their name often leads to confusion. In most cases, these epoxy acrylates have no free epoxy groups left but react through their unsaturation. These resins are formulated with photoinitiators to cure via uv or electron beam (EB) radiation. The reaction mechanism is generally initiated by free radicals or by cations in a cationic photoinitiated system. The uv/EB cured epoxy formulations are discussed in Chap. 14. 

Formulation details are then presented in Chapters 11 through 14 for the various possible forms of epoxy adhesive systems room temperature and elevated-temperature curing liquids, pastes, and solids. The more or less unconventional forms of epoxy adhesives are also identified and discussed, since these are now achieving prominence in industry. These include uv and electron beam radiation curable, waterborne systems, and epoxy adhesives capable of curing via the indirect application of heat or energy. 

Some crystallites will dissociate in the beam while others tend to agglomerate (14). The mass of the crystallite, support-metal interaction, chemical environment, oxidation state of the metal, etc., all have an influence on how the crystallite and electron beam interact. In order to formulate a correlation of these variables with crystallite reactivity with the beam, the crystallite site chemistry is required. This is difficult if not impossible to do because the site chemistry is altered during microscopic examination. With parallel EELS detection the time may be sufficiently reduced that useful chemical information can be obtained and correlations of the type previously described can be made. 

Irradiation crosslinking of PVC-U, carried out using electron beam, has shown a marked increase in glass transition temperature in the presence of a triacrylate, with minimal thermal degradation (216). Electron beam irradiation has also been investigated on a PVC-P wire coating formulation in the presence of different reactive monomers (185). Flame retardancy has also been improved with the incorporation of appropriate flame retardants (118). The effect of UV irradiation on formulations, incorporating iron chloride or cobalt chloride, has also been studied (67). 

The yields of radiation-induced polymerizations can be very high. No additives are required, which makes it possible to synthesize very pure polymers. The initiation step is temperature independent giving rise to an easily controlled process at any desired temperature. These features account for the commercial interest in radiation polymerization. The very high speeds attainable within the layers of monomers subjected to powerful electron beams explain the wide use of this technique in radiation curing of adhesives, inks and coatings. The corresponding formulations are "solvent-free" and involve pre-polymers and monomers as reactive diluents. 

Examples of such photochemical acid generators are shown in Chart 3.2. These onium salts, which are cationic photoinitiators originally developed for curing of epoxy resins (i09), can be used to formulate cross-linking negative resist materials (JOS), are very sensitive to electron beam and X-ray (JOS, 107, 108) radiation, and can be sensitized to longer wavelength radiation (JOS, 110, 111). 

The polymeric systems are usually composed of a polymer which Imparts the majority of physical properties and actinic additives. In simple systems such as curing films or electron beam resists, the polymer is also the radiation sensitive species. In most cases, the formulations behave simllarily in their response to high energy irradiation. Practically any polymer can be made radiation sensitive by direct exposure to ionizing energies or by formulation with additives such as free radical precursors. Thermally sensitive polymers are also likely to undergo a similar reaction when exposed. 

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