Dual-curing systems

The problems associated with the multifunctional curing agents for CTPB and the resultant aging behavior of the cured polymers have led to a practical solution for curing binders and propellants—i.e., using mixed aziridines or a mixture of an aziridine and an epoxide. Such mixtures, when appropriately balanced, usually provide satisfactory mechanical behavior and high temperature stability. In dual curing systems such as MAPO and BITA or MAPO and a suitable multifunctional epoxide,... 

One of the more interesting possibilities of developing truly unique photocurable films lies in the ability of certain onium salts to generate both a reactive radical species and a strong acid upon photolysis. Indeed, several papers describe dual radical/cationic photocurable systems (16-18). The possibilities afforded by dual cure systems provide a unique mechanism for generating cured films with expanded properties for a number of applications. 

Features Promotes amino resin/blocked isocyanate dual cure systems ... 

As reviewed earlier, a semi-EV system is a compromise designed to produce, in structural terms, a vulcanizate containing a balance of monosulfidic and polysulfidic crosslinks at a defined optimum cure state. If polysulfidic crosslinks are to persist over extended periods, new ones must be created to replace those lost through reversion. With use of normal accelerations systems, there is limited opportunity for such events. Maintenance of a polysulfidic network through the curing process thus dictates utilization of a dual-cure system both of which are independent of each other. This is the principle of the equilibrium cure (EC) system. Here, bis(3-triethoxysilylpropyl)tetrasulfane (TESPT) is added as a slow sulfur donor [38] (Fig. 7). 

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)... 

The cross-linked nature of UV/EB-cured adhesives results in good chemical, heat, and abrasion resistance toughness dimensional stability and adhesion to many substrates. Unlike thermal curing, EB or UV curing requires pure raw material grades. The use of dual-curing systems allows opaque substrates to be cured. 

UV silicones can be cured fully by UV or have a dual-cure system... 

However, an adhesive s ability to adhere to specific substrates must be considered. Further progress has been achieved with dual-cure systems the outstanding adhesive performance of polyurethane systems has been combined with the quick curing of free-radical formulations. If including isocyanate components one needs to consider the residual isocyanate monomer content in isocyanate-terminated compounds... 

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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