Sequential heat release: an innovative approach for the control of curing profiles during composite processing based on dual‐curing systems

Abstract

The sequential heat release (SHR) taking place in dual‐curing systems can facilitate thermal management and control of conversion and temperature gradients during processing of thick composite parts, hence reducing the appearance of internal stresses that compromise the quality of processed parts. This concept is demonstrated in this work by means of numerical simulation of conversion and temperature profiles during processing of an off‐stoichiometric thiol–epoxy dual‐curable system. The simulated processing scenario is the curing stage during resin transfer moulding processing (i.e. after injection or infusion), assuming one‐dimensional heat transfer across the thickness of the composite part. The kinetics of both polymerization stages of the dual‐curing system and thermophysical properties needed for the simulations have been determined using thermal analysis techniques and suitable phenomenological models. The simulations show that SHR makes it possible to reach a stable and uniform intermediate material after completion of the first polymerization process, and enables a better control of the subsequent crosslinking taking place during the second polymerization process due to the lower remaining exothermicity. A simple optimization of curing cycles for composite parts of different thickness has been performed on the basis of quality–time criteria, producing results that are very close to the Pareto‐optimal front obtained by genetic algorithm optimization procedures. © 2018 Society of Chemical Industry

Epoxy Doped, Nano‐scale Phase‐separated Poly‐Acrylates with Potential in 3D Printing

“…Although a UV post‐curing stage can partially mitigate this problem, curing schedules should be planned so as to avoid these spatial gradients along part dimensions and minimize deformation, cracking, or delamination. [ 16,17 ] Herein, we report the successful incorporation of an epoxy‐anhydride network into a poly(acrylate) network through a two‐step process: a visible light 3D printing followed by thermal curing of the epoxy‐anhydride. Compared to the other papers mentioned, the novelty of the work is twofold: the utilization of visible light in lieu of UV irradiation, and the use of a thermally triggered radical initiator which ensures that all remaining acrylate monomers end up polymerizing at the thermal stage, concurrently with epoxy‐anhydride reaction.…”

Morphology Control in a Dual-Cure System for Potential Applications in Additive Manufacturing

“…Dual-curing mixtures of acrylates and epoxy materials are common in commercial SLA printing [6], and a dual-cure process was recently commercialised by Carbon Co. [18,19] in their continuous liquid interface process. Additionally, multi-component/dual-curing polymer IPNs have been investigated for a range of applications including acrylate urethane for automotive coatings [20] and have been utilised for the control of reaction exotherms in industrial processing of thermoset resins [21].…”

Enhancement of 3D-Printable Materials by Dual-Curing Procedures

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