Polydopamine-Coated Paraffin Microcapsules as a Multifunctional Filler Enhancing Thermal and Mechanical Performance of a Flexible Epoxy Resin

Abstract

This work focuses on flexible epoxy (EP) composites containing various amounts of neat and polydopamine (PDA)-coated paraffin microcapsules as a phase change material (PCM), which have potential applications as adhesives or flexible interfaces with thermal management capability for electronics or other high-value-added fields. After PDA modification, the surface of PDA-coated capsules (MC-PDA) becomes rough with a globular appearance, and the PDA layer enhances the adhesion with the surrounding epoxy matrix, as shown by scanning electron microscopy. PDA deposition parameters have been successfully tuned to obtain a PDA layer with a thickness of 53 ± 8 nm, and the total PDA mass in MC-PDA is only 2.2 wt %, considerably lower than previous results. This accounts for the fact that the phase change enthalpy of MC-PDA is only marginally lower than that of neat microcapsules (MC), being 221.1 J/g and 227.7 J/g, respectively. Differential scanning calorimetry shows that the phase change enthalpy of the prepared composites increases with the capsule content (up to 87.8 J/g) and that the enthalpy of the composites containing MC-PDA is comparable to that of the composites with MC. Dynamic mechanical analysis evidences a decreasing step in the storage modulus of all composites at the glass transition of the EP phase, but no additional signals are detected at the PCM melting. PCM addition positively contributes to the storage modulus both at room temperature and above Tg of the EP phase, and this effect is more evident for composites containing MC-PDA. As the capsule content increases, the mechanical properties of the host EP matrix also increase in terms of elastic modulus (up to +195%), tensile strength (up to +42%), Shore D hardness (up to +36%), and creep compliance (down to −54% at 60 min). These effects are more evident for composites containing MC-PDA due to the enhanced interfacial adhesion.

Electrospun Shape-Stabilized Phase Change Materials Based on Photo-Crosslinked Polyethylene Oxide

“…In fact, the melting signal is observable in both UV-crosslinked samples as a step in and and, for PEO-XL-C, also as a small peak in This signal is evident between 75 °C and 80 °C for PEO-XL-E and at a slightly higher temperature (between 80 °C and 85 °C) for PEO-XL-C. Interestingly, DMTA allowed monitoring the behavior of the PCM across the phase transition and investigating the impact of this transition on the viscoelastic parameters, which is an uncommon application for DMTA. Similar results have already been observed in previous works of our group [ 49 , 50 , 51 , 52 , 53 ] dealing with polymer-matrix composites containing an organic solid-liquid PCM. The present work demonstrated that this technique can be applied also to a shape-stabilized PCM by itself, which, to the best of the authors’ knowledge, has never been reported before in the open scientific literature.…”

Thermophysical Properties of Multifunctional Syntactic Foams Containing Phase Change Microcapsules for Thermal Energy Storage

“…The adhesion between the outer PCM shell and the epoxy matrix is not optimal and this is better observed on higher-magnification micrographs (not reported for brevity). However, the fact that most PCM microcapsules are broken suggests that the fracture propagates across the microcapsules and not at the interface with the epoxy matrix [ 45 , 46 ]. In any case, the low interfacial adhesion could represent a drawback of the proposed system and will be addressed in future research.…”

Microfluidic Fabrication and Thermal Properties of Microencapsulated N-Hexadecane with a Hybrid Polymer Shell for Thermal Energy Storage

“…Thermal energy storage (TES) systems have received much attention in recent years, due to the increasingly serious energy crisis and environmental problems [ 1 , 2 ]. It is reported that, on a global scale, total primary energy supply was 573 EJ and final consumption was 394 EJ per year, with around 31% energy was lost [ 3 ].…”

“…The most attractive term for the working media of latent heat storage systems is phase-change materials (PCMs), because they do not require external energy input, are low cost, and can meet the heat storage requirements over a wide temperature range [ 6 ]. Even with these advantages, leakage and erosion issues seriously restrict the direct application of bulk PCMs unless they are enclosed or encapsulated upon melting or evaporation [ 2 , 7 ].…”