Analysis of the Possibility and Conditions of Application of Methylene Blue to Determine the Activity of Radicals in Model System with Preaccelerated Cross-Linking of Polyester Resins

Abstract

Unsaturated polyester resins are usually processed using a curing system consisting of initiator and accelerator introduced into the resin. Actually, the producers apply built-in amine accelerators which can be named as preaccelerators. Commonly used preaccelerators for unsaturated resins are tertiary aromatic amines of which incorporation into resin structure may bring better stability. It also causes shorter gelation time of resins because of formation of active RO• radicals that initiate polymerization. Investigated radical reactions are too fast and there is no possibility of freezing it (in unsaturated polyester) to measure with Electron Paramagnetic Resonance (EPR). The analytical methodology on radicals activity measurement in model of preaccelerated unsaturated polyester resin reaction with methylene blue as indicator was presented. Using methylene blue as indicator allows us to determine the activity of forming radicals in three-component system (cobalt salt, amine preaccelerator, peroxide, or hydroperoxide) during the reaction of radicals generating. Changes in radicals activity using methylene blue as interceptor can be observed by changes of transmittance in the UV-Vis spectrum in the range 400-950 nm.

Green fluorescent unsaturated polyester/graphitic carbon nitride quantum dots nanocomposites: Preparation and study of UV-resistance, mechanical and viscoelastic properties

“…Styrene makes the cross linkages among polyester chains to make a three-dimensional polymeric network. 32,33 CNQDs also participate in UP polymerization reaction and are grafted to the polymer chains that consequently UP/CNQDs nanocomposites are created. Figure 2 demonstrates the polymerization process of UP/CNQDs nanocomposite.

Figure 2.Polymerization process of UP/CNQDs nanocomposite.

…”