Toughening Mechanisms in Vat-Photopolymerised Thermosets: Network Topology, Phase Morphology, Reinforcement and Process Trade-Offs
Segurola, Juan
2026-08-27 · Informe · Versión 1.1
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Vat photopolymerisation requires rapid spatial fixation of a liquid resin, a condition that commonly favours multifunctional precursors, early gelation and highly crosslinked glassy networks. These features support print fidelity but can suppress chain extensibility and concentrate deformation. The resulting stiffness- toughness conflict has generated multiple toughening routes that are frequently grouped together despite operating through different physical mechanisms. This review organises dry VPP thermoset toughening into homogeneous co-reactive blending, bimodal long-chain/short-crosslinker networks, elastomeric click networks, sacrificial non-covalent interactions, semicrystallinity combined with dynamic bonds, core-shell particles, covalently incorporated hyperbranched rubbers, controlled phase morphology, nanofiller crack bridging, thiol-acrylate chain transfer and light-directed molecular orientation. Representative studies show that similar improvements in tensile work, elongation, impact response or cracked-specimen resistance can arise from fundamentally different structures. The same additive can also increase viscosity, attenuation, shrinkage, anisotropy or post-cure sensitivity. A mechanism claim therefore requires more than a property increase: it requires direct evidence of the proposed topology or morphology, a matched formulation control, process-state data and a response that is consistent with the claimed dissipation route. Fracture-test validity remains outside this paper and is treated in ER-70. The central conclusion is that toughening is a causal architecture, not a marketing label or a single number. A defensible VPP material claim must link precursor structure, resin optics and rheology, gelation and conversion, final network or phase state, conditioning, deformation mechanism and failure mode.