Process-Induced Monomers

Another issue is the uniformity of the temperature distribution throughout the melt. In fact, the melt temperature is known to be highly non-uniform due to the low thermal conductivity of the viscous molten polymer. Large temperature differences ( 50 °C) have been observed in different regions of the molten polymer within the same extruder, which results in non-uniform properties [5, 6]. 

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Keywords Moisture Temperature Process-induced monomer Sterilization techniques Ethylene oxide Radiation Packaging... 

Additives and impurities Process-induced monomers Inflammatory reactions and... 

V. Ella, L. Nikkola, M. Kellomaki, Process-induced monomer on a medical-grade polymer and its effect on short-term hydrolytic degradation. J. Appl. Polym. Sci. 119(5), 2996—3003 (2011)... 

Radiation processing of monomers and polymers by electron beam, such as polymerization and copolymerization of monomers, cross-linking, grafting, and degradation of polymers, is induced by these different chemically reactive species. ... 

In a different vein, 10,11-epoxyundecanoic acid was exploited as an AB monomer, which was polymerised by the oxirane ring-opening chain process induced by the carboxylic group sitting at its other end and catalysed by ammonium or phosphonium salts [78], as illustrated in Scheme 4.19. The ensuing linear hydroxylated polyester... 

Photopolymerization, in general, can be defined as the process whereby light is used to induce the conversion of monomer molecules to a polymer chain. One can distinguish between true photopolymerization and photoinitiation of polymerization processes. In the former, each chain propagation step involves a photochemical process [1,2] (i.e., photochemical chain lengthening process in which the absorption of light is indispensable for... 

Ionizing radiation is unselective and has its effect on the monomer, the polymer, the solvent, and any other substances present in the system. The radiation sensitivity of a substrate is measured in terms of its G value or free radical yield G(R). Since radiation-induced grafting proceeds by generation of free radicals on the polymer as well as on the monomer, the highest graft yield is obtained when the free radical yield for the polymer is much greater than that for the monomer. Hence, the free radical yield plays an important role in grafting process [85]. 

The creation of active sites as well as the graft polymerization of monomers may be carried out by using radiation procedures or free-radical initiators. This review is not devoted to the consideration of polymerization mechanisms on the surfaces of porous solids. Such information is presented in a number of excellent reviews [66-68]. However, it is necessary to focus attention on those peculiarities of polymerization that result in the formation of chromatographic sorbents. In spite of numerous publications devoted to problems of composite materials produced by means of polymerization techniques, articles concerning chromatographic sorbents are scarce. As mentioned above, there are two principle processes of sorbent preparation by graft polymerization radiation-induced polymerization or polymerization by radical initiators. We will also pay attention to advantages and deficiencies of the methods. 

Radical induced grafting may be carried out in solution, in the melt phase,292 29 or as a solid state process.296 This section will focus on melt phase grafting to polyolefin substrates but many of the considerations are generic. The direct grafting of monomers onto polymers, in particular polyolefins, in the melt phase by reactive extrusion has been widely studied. Most recently, the subject has been reviewed by Moad1 9 and by Russell.292 More details on reactive extrusion as a technique can be found in volumes edited by Xanthos," A1 Malaika and Baker et a 21 7 The process most often involves combining a frcc-radical initiator (most commonly a peroxide) and a monomer or macromonomer with the polyolefin as they are conveyed through the extruder. Monomers commonly used in this context include MAII (Section 7.6.4.1), maleimidc derivatives and malcate esters (Section 7.6.4.2), (meth)acrylic acid and (meth)acrylate esters (Section 7.6.43), S, AMS and derivatives (Section 7.6.4.4), vinylsilancs (Section 7.6.4.5) and vinyl oxazolines (Section 7.6.4.6). 

The most comprehensive simulation of a free radical polymerization process in a CSTR is that of Konopnicki and Kuester (15). For a mechanism which includes transfer to both monomer and solvent as well as termination by combination and disproportionation they examined the influence of non-isothermal operation, viscosity effects as well as induced sinuoidal and square-wave forcing functions on initiator feed and jacket temperature on the MWD of the polymer produced. 

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