Electron Beam Processing of Liquid Systems

Electron beam processing of solvenf-free liquid systems for coatings, inks, and paints involves essentially polymerizahon and cross-linking using electrons with energies between 120 and 300 keV. Initiation by electrons leads primarily to free radical reactions. Cationic polymerization is only found in rare cases.  

Typical liquid systems require doses between 10 and 50 kGy. They consist of binders (prepolymers) with acrylic (H2C=CH-CO-0-) double bonds in the main chain (polymaleates and polyfumarates) and of monomers, usually acrylates used as reactive thinners. Other ingredients added to the formulation may be pigments, dyes, fillers, flatting agents, and additives to improve film and surface properties and attain the required performance criferia.  

Reactive prepolymers used as binders are produced by acrylation of oligomers, such as epoxy resins, urethanes, polyesters, silicones, oligo-buta-diene, melamine derivatives, cellulose, and starches. Prepolymers are the principal ingredients of coating formulations and largely determine the basic properties of the coating. Examples of industrially important acrylated prepolymers are in Table 5.9. 

Tripropylene glycol diacrylate (TPGDA) 1,6-Hexanediol diacrylate (HDDA) Dipropylene glycol diacrylate (DPGDA) 

Examples of Acrylate Prepolymers Used for Radiation Technology 

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Natural Rubber and Synthetic Polyisoprene Polybutadiene and Its Copolymers Polyisobutylene and Its Copolymers Ethylene-Propylene Copolymers and Terpolymers Polychloroprene Silicone Elastomers Fluorocarbon Elastomers Fluorosilicone Elastomers Electron Beam Processing of Liquid Systems Grafting and Other Polymer Modifications... 

It is worth noting that some of these methods are both an inlet system to the mass spectrometer and an ion source at the same time and are not used with conventional ion sources. Thus, with electrospray, the process of removing the liquid phase from the column eluant also produces ions of any emerging mixture components, and these are passed straight to the mass spectrometer analyzer no separate ion source is needed. The particle beam method is different in that the liquid phase is removed, and any residual mixture components are passed into a conventional ion source (often electron ionization). 

We have investigated in detail the parameters affecting the continuous y-radiolysis of concentrated solutions (intensity, pH, 02, scavengers, etc.). Transients were investigated by pulsed electron beam radiolysis and kinetic spectroscopy, and the reactions of the optically accessible excited states of nitrate were investigated by conventional photolysis. This paper represents a survey of our recent results which, taken in conjunction with the work of others, allows the construction of a model whereby the main features of this system may be understood and may even be predicted. Literature review is necessarily selective for the present purpose (because of doubtful relevance to liquid state processes, low temperature radiolysis, and hence ESR work has been omitted from... 

Flash photolysis and electron-pulse techniques may be considered as cases of extreme perturbing functions, in the first case an extremely intense flash of light, in the other case a beam of electrons. Such perturbations cause extreme deviations from equilibrium concentrations, so that linear first-order rate equations no longer describe the time behavior of the system. In fact, molecules are often promoted to higher electronic states. With the advent of the laser, the time resolution of flash photolysis has been reduced to picoseconds. This permits the study of processes not previously accessible to kineticists. The types of systems studied include radiationless transitions, the solvated electron and chlorophyll. For example, the cage effect in liquids has been demonstrated by a study of the recombination of iodine atoms at very short times [8]. Although these methods are of considerable interest, we do not discuss them in further detail here (cf. Hammes [1]). 

When an X-ray beam falls on alums iwo processes may occur. The beam may be scaltcrcd or the beam may be absorbed with an ejection of electrons from an atom. In the case of a crystalline material the scattering of X-rays is used to determine the structure of the solid phase and the chemist applies this method to the proof of the structure of new compounds very often. But even when a regular crystalline arrangement does not exist, as in liquids or amorphous solids, scattering patterns are produced. I.ike in the crystalline solid phase the scattering of X-rays on disordered systems can be used to determine the probability of distribution of atoms in the environment of any reference atom, or in other words the frequency with which interatomic distances occur. 

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