Dual curing thermal treatment

Recently, Endo and coworkers have developed novel sulfonium type initiators that can initiate polymerization either upon irradiation or upon thermal treatment. In addition, these photoinitiators are shown to be functional for both cationic and radical polymerizations. This dual activity is particularly important in hybrid curing systems for coatings and adhesions [28]. Scheme 11.6 contains the general steps for the synthesis of these photoinitiators from sulfides. 

Chart 11.5 Part of a three-dimensional network formed by UV irradiation and thermal treatment of a dual-cure acrylic urethane system [27]. 

When UV-curable resins are used as laminated adhesives to protect three-dimensional objects having complex shapes, it may happen that some remote areas wiU not be accessible to UV-radiation and therefore remain uncured. To address the issue of such shadowed areas, dual-cure systems combining UV-irradiation and thermal treatment have been developed [71]. They contain two types of reactive functions a UV-curable functional group (usually an acrylate double bond)... 

Modem approaches in the field of hybrid materials for advanced applications use dual cure processing which, depending on the nature of components, may be (a) a UV-cure followed by a thermal treatment, or (b) a UV-cure followed by a... 

In this respect, it should be mentioned that dual-cure systems, combining UV irradiation and a thermal treatment, have been developed to address the issue of the lack of cure in shadow areas of 3D objects, as well as in thick pigmented samples." " A few centimeter thick nanocomposite materials can be produced by this two-step process which associates the photopolymerization of the acrylate resin and the thermally-induced polyaddition of isocyanate and alcohol groups ... 

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