Ultraviolet polymerization

Ultraviolet polymerization has been used to graft acrylic acid, acrylamide, dim-ethylacrylamide, 2-hydroxylethyl acrylate, or poly(ethyleneglycol) monomethoxyl... 

Photopolymerization and Plasma Polymerization. The use of ultraviolet light alone (14) as well as the use of electrically excited plasmas or glow discharges to generate monomers capable of undergoing VDP have been explored. The products of these two processes, called plasma polymers, continue to receive considerable scientific attention. Interest in these approaches is enhanced by the fact that the feedstock material from which the monomer capable of VDP is generated is often inexpensive and readily available. In spite of these widespread scientific efforts, however, commercial use of the technologies is quite limited. 

Geotextiles may be woven, nonwoven, or knitted. AH types, woven, nonwoven, or knitted, are susceptible to degradation owing to the effects of ultraviolet light and water. Thus stabilizing agents are added to the base polymeric material to lessen the effects of exposure to ultraviolet light and water. 

Photopolymerization. In many cases polymerization is initiated by ittadiation of a sensitizer with ultraviolet or visible light. The excited state of the sensitizer may dissociate directiy to form active free radicals, or it may first undergo a bimoleculat electron-transfer reaction, the products of which initiate polymerization (14). TriphenylaLkylborate salts of polymethines such as (23) ate photoinitiators of free-radical polymerization. The sensitivity of these salts throughout the entire visible spectral region is the result of an intra-ion pair electron-transfer reaction (101). 

In the foregoing discussion polymers have been used as a medium for smaU molecules in comparison with the crystalline state. It has also been observed that there are changes in polymeric geometry and various rotational motions introduced by pressure (10—14). These are at times reflected in the absorption spectmm (usuaUy in the ultraviolet) or in the emission spectmm and are a form of piezochromism. 

An example, Figure 9 is an SFM image of a Langmuir-Blodgett film. This film was polymerized with ultraviolet light, giving a periodicity of 200 A, which is seen in the associated Fourier transform. The low forces exerted by the SFM tip are essential for imaging such soft polymer surfaces. 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials No reactions Stability During Transport Stable Neutralizing Agemsfor Acids and Caustics Not pertinent Polymerization Polymerizes when exposed to heat, ultraviolet light, or free-radical catalysts Inhibitor of Polymerization 200 ppm Hydroquinone. 

Acrylic is a generic name for derivatives of acrylic acid, of which methyl methacrylate is the most important. Polymerization is controlled to produce chain length of 800 to 3,000 monomer units. A small amount of plasticizer such as dibutyl phthalate may be added before bulk polymerization to assist in deep molding. The outstanding property of polymethyl metliacrylate is 0 transparency resistance to ultraviolet radiation from fluorescent lamps and ability to be... 

Acrylamide readily undergoes polymerization by conventional free radical methods, ionizing radiation, ultrasonic waves, and ultraviolet radiation. The base-cata-lized hydrogen transfer polymerization of acrylamide yields poly-/3-alanine (Nylon 3) a water insoluble polymer that is soluble in certain hot organics. All current industrial production is believed to be by free radical polymerization. 

This aminium radical salt in aqueous solution in the form of solvated radical salt is very stable and will not polymerize acrylonitrile even with CeHsCOONa to form the corresponding benzoate. Therefore, we believe that in the nucleophilic displacement, there must be some intermediate step, such as intimate ion pair and cyclic transition state, which will then proceed the deprotonation to form the active aminium radical ion [14], as shown in Scheme 1. The presence of the above aminomethyl radical has also been verified [15] through ultraviolet (UV) analysis of this polymer formed such as PAN or PMMA with the characteristic band as the end group. 

One of the first methods of polymerizing vinyl monomers was to expose the monomer to sunlight. In 1845, Blyth and Hoffman [7] obtained by this means a clear glassy polymeric product from styrene. Berthelot and Gaudechon [8] were the first to polymerize ethylene to a solid form and they used ultraviolet (UV) light for this purpose. The first demonstration of the chain reaction nature of photoinitiation of vinyl polymerization was done by Ostromislenski in 1912 [9]. He showed that the amount of poly(vinyl bromide) produced was considerably in excess of that produced for an ordinary chemical reaction. 

Paints are complex formulations of polymeric binders with additives including anti-corrosion pigments, colors, plasticizers, ultraviolet absorbers, flame-retardant chemicals, etc. Almost all binders are organic materials such as resins based on epoxy, polyurethanes, alkyds, esters, chlorinated rubber and acrylics. The common inorganic binder is the silicate used in inorganic zinc silicate primer for steel. Specific formulations are available for application to aluminum and for galvanized steel substrates. 

Rodriguez and Gandini139,14° have recently carried out some work on the structure of the soluble polymers of the two ketones. The purified monomers were polymerized with various acids to give dark soluble products with DP s of 10—20. The ultraviolet, infrared, and NMR spectra and the elemental analysis of these purified substances were compared with those of the starting monomers. It was concluded that, at least for this initial phase, the two systems are characterized by polymerization through the olefinic bond because ... 

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