Abstract
A novel set of dual-curable multiacetoacetate-multiacrylate-divinyl sulfone ternary materials with versatile and manipulable properties are presented. In contrast to common dual-curing systems, the first stage polymer herein consists of a densely crosslinked, high Tg network as a result of base-catalyzed multiacetoacetate-divinyl sulfone Michael addition. A more flexible secondary network forms after base-catalyzed Michael addition of remaining multiacetoacetate to multiacrylate. Curing is truly sequential as the rates of the two Michael additions are significantly different. Curing kinetics were analyzed using differential scanning calorimetry (DSC) and Fourier-transform infrared (FTIR). The materials at each curing stage were characterized using dynamic mechanical analysis (DMA) and SEM. Although some phase separation was observed in certain formulations, the incompatibilities were minimized when the molar percentage of the acetoacetate-divinyl sulfone polymer network was above 75%. Furthermore, the environmental scanning electron microscopy (ESEM) images of these materials show that the more flexible acetoacetate-acrylate phase is dispersed in the form of polymeric spheres within the rigid acetoacetate-divinyl sulfone matrix. This unique dual microstructure can potentially render these materials highly resilient in applications requiring densely crosslinked polymer architectures with enhanced toughness.
Highlights
More and more thermosetting polymers are prepared by versatile dual-curing methodologies due to their many advantages in terms of material processing [1,2,3,4,5]
The second curing stage is initiated at a later time using a different stimulus to yield the final material with significantly improved mechanical properties
A trifunctional acetoacetate K-FLEX® 7301, supplied by King Industries, Norwalk, CT, USA, was used as a Michael reagent donor
Summary
More and more thermosetting polymers are prepared by versatile dual-curing methodologies due to their many advantages in terms of material processing [1,2,3,4,5]. For simultaneous dual-curing, a sequential process facilitates processing flexibility as it affords the storage of stable intermediate (i.e., partially-cured) materials. The properties of these intermediate materials can be tailored a priori by careful selection of monomers and their proportions. As a result, they can range from liquid-like adhesives to semi-rigid and conformable solids [6]. The second curing stage is initiated at a later time using a different stimulus to yield the final material with significantly improved mechanical properties
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