Polymerization reaction photocures

Many aspects of the polymerization reactions of light curable coatings, however, are more complex. A number of attempts were made to describe the kinetic pictures of photocuring. Some of these are presented below. 

It is important that the photopol5mierization initiator has an absorption peak in a different wavelength region from the color material (44). Also, a pol nnerization inhibitor may be added in order to suppress a preliminary unwanted polymerization reaction (51). Examples of pol5merization inhibitors are shown in Table 3.26. In addition, examples of photocurable recipes are shown in Table 3.27. 

Besides the above noted polymerization techniques photocuring is a special process that transforms a multifunctional monomer into a crosslinked macromolecule by a chain reaction initiated by reactive species generated by UV irradiation [77]. Three basic components are needed for photocuring ... 

An advantage of this type of photopolymerizations is that as they are non-radical chain polymerizations, they are insensitive to oxygen. In addition, as the cation is relatively stable, the reaction is able to continue in the dark. Applications of this chemistry may be found in the fields of coatings, adhesives, printing inks, and also for photocurable composites and microelectronic photoresists. 

The reaction of glycidyl acrylate with a-(2-carboxyethyl)benzoin methyl ether has allowed one to obtain [101] the corresponding acrylic monomer which, upon copolymerization with different amounts of MMA, butyl methacrylate and 2-(V, V-dimethylamino)ethyl methacrylate, gives rise to polymeric photoinitiators, containing side-chain benzoin methylether moieties, for photocurable coatings ... 

It Is well known that cationic polymerization may be Inhibited by nucleophilic species In the reaction mixture however, vinyl ethers appear to be less sensitive than epoxies to presence of nucleophiles. The high reactivity of the vinyl ether group with the growing cationic chain Is often favored over termination by a nucleophilic species. Water may act as a nucleophile and It has been reported that high atmospheric humidity conditions will Inhibit the photocuring of epoxles(24). We have observed a similar effect on vinyl ether based coatings. 

It is important to monitor photopolymerization reactions as they provide valuable information about the reaction kinetics, which can help optimize photocurable formulations to achieve desired properties, such as structural, physical, and mechanical, in the cured materials. This section provides a detailed summary of the available characterization techniques commonly used to investigate photopolymerization reactions. The parameters that are generally investigated are the rate of polymerization Rp), DC and the amount of RCs, induction period (ti), quantum yield of polymerization, kinetic chain lengths, and gelation time. 

The photocured films were characterized by DSC and DMTA analyses. The data, reported in Table 2, show that by increasing the amount of PBOH in the photocurable mixture a decrease of Tg is induced. The flexibilization of the network is obtained as a consequence of the chain transfer reaction and to the introduction in the polymeric network of the very flexible PBOH structure. 

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