Issue 8, 2023

Frontally polymerized foams: thermodynamic and kinetical aspects of front hindrance by particles

Abstract

Frontal polymerization (FP) is a solvent-free, energy-efficient process where a self-propagating polymerization reaction with a characteristic sharp temperature gradient at the front head propagates through the resin to provide the curing conditions. It relies on the enthalpic balance, which spreads the reaction to unreacted resin in the neighborhood. Therefore, the FP is sensitive to the presence of non-reactive volumes, such as boundaries, fillers, or other additives, that retain heat from the front but produce no enthalpy in return. On the other hand, the front's high temperature could be used to initiate other processes, such as foaming, incorporating them into a simple single-step fabrication procedure. This study used silica particles of two different sizes (14 nm and 200–300 nm) in an epoxy-based FP foam as a representative filler to probe the constraints imposed by non-reactive additives. The presence of particles visibly hindered the front propagation, increased the foam density and even corrupted the frontal regime in some cases. We show that preheating or chemical composition changes are viable approaches to address the fillers’ adverse effects. Furthermore, we present evidence that the reduced reaction enthalpy caused by silica nanoparticles, was balanced by the lower heat capacity of our model system. At the same time, the front hindrance was attributed to changes in reaction kinetics and the heat distribution around the front. These results set up essential narratives for the design and practical applications of frontally polymerized foams with non-reactive fillers.

Graphical abstract: Frontally polymerized foams: thermodynamic and kinetical aspects of front hindrance by particles

Supplementary files

Article information

Article type
Communication
Submitted
21 Dec 2022
Accepted
09 May 2023
First published
09 May 2023
This article is Open Access
Creative Commons BY license

Mater. Horiz., 2023,10, 2989-2996

Frontally polymerized foams: thermodynamic and kinetical aspects of front hindrance by particles

P. Lepcio, J. Daguerre-Bradford, A. M. Cristadoro, M. Schuette and A. J. Lesser, Mater. Horiz., 2023, 10, 2989 DOI: 10.1039/D2MH01553F

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