Thermal mending in immiscible poly(ε-caprolactone)/epoxy blends

Cohades, Amaël; Manfredi, Erica; Plummer, C. J. G.; Michaud, Véronique

doi:10.1016/j.eurpolymj.2016.05.026

Cited by 36 publications

(65 citation statements)

References 51 publications

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“…This craze formation observed on the fracture surface is initiated by void formation that follows the interfacial debonding between PCL phases and epoxy matrix, so the energy dissipated by the craze formation when PCL is finely dispersed is greater than that in neat epoxy regions that surround the PCL 3D printed strands. This result is consistent with the information found in literature for epoxy/PCL blends [38,66].…”

Section: Microstructural Behaviorsupporting

confidence: 93%

“…Materials 2020, 13,819 11 of 17 EP-PCL specimen fulfills the linearity and plasticity requirements, with a mean PMAX/PQ value equal to 1.10. The reported value of healing efficiency (see Table 3) is in accordance both with that obtained for EP-PCL(3D), and also with those reported in literature [38,66]. In the case of EP-PCL blends produced with melt-mixing, higher healing efficiency can be obtained when the morphologies of the two phases are completely co-continuous, or even better efficiencies can be achieved with a phaseinverted morphology at high PCL content.…”

Section: Evaluation Of the Thermal Healing Behaviorsupporting

confidence: 90%

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Novel Poly(Caprolactone)/Epoxy Blends by Additive Manufacturing

2020

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The aim of this work was the development of a thermoplastic/thermosetting combined system with a novel production technique. A poly(caprolactone) (PCL) structure has been designed and produced by fused filament fabrication, and impregnated with an epoxy matrix. The mechanical properties, fracture toughness, and thermal healing capacities of this blend (EP-PCL(3D)) were compared with those of a conventional melt mixed poly(caprolactone)/epoxy blend (EP-PCL). The fine dispersion of the PCL domains within the epoxy in the EP-PCL samples was responsible of a noticeable toughening effect, while in the EP-PCL(3D) structure the two phases showed an independent behavior, and fracture propagation in the epoxy was followed by the progressive yielding of the PCL domains. This peculiar behavior of EP-PCL(3D) system allowed the PCL phase to express its full potential as energy absorber under impact conditions. Optical microscope images on the fracture surfaces of the EP-PCL(3D) samples revealed that during fracture toughness tests the crack mainly propagated within the epoxy phase, while PCL contributed to energy absorption through plastic deformation. Due to the selected PCL concentration in the blends (35 vol %) and to the discrepancy between the mechanical properties of the constituents, the healing efficiency values of the two systems were rather limited.Materials 2020, 13, 819 2 of 17 processing and mixing steps are very important to obtain a good morphology and high mechanical properties. Epoxy/thermoplastic polymer blends can be produced through mechanical methods, by using batch or continuous mixers [27] or continuous polymerization reactors [28]. In the low-shear batch mixers, the thermosetting epoxy resin base is heated at high temperature to allow a better homogenization and dispersion with the thermoplastic powders, and then the curing agent is added. After degassing, the mixture can be either partially cured and then quenched or directly casted into molds for final curing. This type of mixing is not efficient for concentrations of the thermoplastic phase higher than about 30 wt %, because the viscosity of the system becomes too high to allow an efficient process. Epoxy/thermoplastic polymer blends can be also produced through non-mechanical methods, such as solvent casting, resonant acoustic mixers, and in-situ polymerization processes. Depending on the chemical nature of the constituents and on the processing route, different morphologies can be obtained for epoxy/thermoplastics blends. Homogeneous microstructures can be produced when the thermoplastic phase is soluble in the epoxy matrix and if this condition is maintained during the curing process. The homogeneity can be either due to low concentration of the thermoplastic component or due to the good affinity between the different phases. Examples of epoxy blends which remain homogeneous are those with polycarbonate and poly(ε-caprolactone) [29,30]. Heterogeneous microstructures can be obtained either with an initial immiscible mixture or starting with a homo...

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Section: Microstructural Behaviorsupporting

confidence: 93%

Section: Evaluation Of the Thermal Healing Behaviorsupporting

confidence: 90%

Novel Poly(Caprolactone)/Epoxy Blends by Additive Manufacturing

2020

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“…The addition of the thermoplastic or rubber phase into the epoxy thermosetting matrix usually produces a toughening of the brittle resin [5,8,20,21] due to the dissipation impact energy induced by the second low modulus polymer separated phase. The morphological study of the fractured surfaces on thermoplastic/thermosetting blends provides useful information about their mechanical behavior [20,21].…”

Section: Thermal and Mechanical Behaviourmentioning

confidence: 99%

“…In particular, the self-healing efficiency of both epoxy resins with 15 wt % PCL was unexpectedly high, despite its morphology, constituted by separated PCL domains into epoxy matrix. This behavior is very interesting since the TS/TP blends keep the excellent behavior of the epoxy matrix with enhanced toughness [8] associated to thermoplastic domains and, in addition, it presents an efficient self-healing ability. In order to explain this last behavior, a digital image analysis of FEG-SEM was carried out.…”

Section: Self-healing Propertiesmentioning

confidence: 99%

Influence of Morphology on the Healing Mechanism of PCL/Epoxy Blends

2020

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Polycaprolactone (PCL) is being researched as a self-healing agent blended with epoxy resins by several reasons: low melting point, differential expansive bleeding (DBE) of PCL, and reaction induced phase separation (RIPS) of PCL/epoxy blends. In this work, PCL/epoxy blends were prepared with different PCL ratios and two different epoxy networks, cured with aliphatic and aromatic amine hardeners. The curing kinetic affects to the blend morphology, varying its critical composition. The self-healing behavior is strongly affected by the blend morphology, reaching the maximum efficiency for co-continuous phases. Blends with dispersed PCL phase into epoxy matrix can also show high self-healing efficiency because of the low PCL domains that act as reservoir of self-healing agent. In this last case, it was confirmed that the most efficient self-healable blends are one whose area occupied by PCL phase is the largest. These blends remain the good thermal and mechanical behavior of epoxy matrix, in contrast to the worsened properties of blends with bicontinuous morphology. In this work, the self-healing mechanism of blends is studied in depth by scanning electron microscopy. Furthermore, the influence of the geometry of the initial surface damage is also evaluated, affecting to the measurement of self-healing efficiency.it depends on both a kinetic curing reaction and the thermodynamics of phase separation. The obtained TP/TS morphology is strongly influenced by TP fraction added. At contents lower than critical composition, the blend morphology is usually a dispersion of TP-rich domains in the TS matrix. However, at high TP percentages, a phase inversion occurs, showing TS-rich modules dispersed into a TP-rich matrix. Close to critical composition, the blend morphology can show co-continuous phases or doubled separated phases. For TS toughening, the desired morphology is the first one, TP domains dispersed into TS matrix [4,5]. The presence of low stiffness thermoplastic domains into brittle thermoset matrix induces the appearance of different toughening mechanisms, such as shear yielding, cavitation, crack deflection, crack bifurcation, and bridging, among others.However, critical compositions are being more investigated [6], in the recent years, as self-healing strategy, due to the better distribution and higher area occupied by TP phase, which really acts healable agent.Self-healing process is usually based on a mobile phase, triggered by external stimuli, which is able to transport melted TP mass to the crack site and local mending connection by chemical bonds or physical interactions. In the case of self-healable TS/TP blends, the healing process is based on the melting of the thermoplastic phase. This means that the main requirement of the TS/TP blend to show self-healing capability is the selection of a semicrystalline thermoplastic polymer, whose melting point (T m ) is significantly lower than the glass transition temperature (T g ) of the TS resin in order to promote enough flow to crack.As it is mentioned above...

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“…For immiscible thermoplastic/thermoset blends, the healing phenomenon is related to i) melting and subsequent volume expansion of the thermoplastic phase, ii) flow of the melt into the damage volume, and iii) characteristic physical or chemical phenomena taking place at the molecular level . This last mechanism can consist of either chain re‐entanglement of the thermoplastic melt, based on thermally enhanced chain mobility, or the formation of reversible noncovalent (e.g., hydrogen or ionic) bonds in the thermoplastic phase.…”

Section: Self‐healing Fiber‐reinforced Polymer Composites: the State mentioning

confidence: 99%

Progress in Self‐Healing Fiber‐Reinforced Polymer Composites

Cohades

Branfoot

Rae

et al. 2018

Adv Materials Inter

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With the potential for small-scale damage to grow or coalesce under subsequent loading, FRP structures incorporate high safety factors to account for this defect sensitivity to ensure they will remain load bearing throughout their service life. This paradigm has resulted in many research groups worldwide exploring and developing the concept of self-healing or selfrepair being applied to FRPs, with the aim of achieving autonomous structural recovery via an embedded functionality, to address damage formation in its early stages before the integrity of the structure is compromised. In principle, this could reduce the structural redundancy and fully realize the mass saving associated with using FRP composite materials. This paper sets out to review the current state of the art in applying self-healing/self-repair to high-performing advanced fiber-reinforced polymer composite materials. Our definition of an advanced fiber-reinforced polymer composite material for this work is as follows:Our review discusses what has been achieved to date, the ongoing challenges which have arisen in implementing selfhealing into FRPs, how considerations for industrialization and large-scale manufacture must be considered from the outset, where self-healing may provide the most benefits (with respect to current FRP approaches to design), and how a functionality like self-healing can be validated for application in real structures.A significant proportion of self-healing studies have focused on assessing the healing efficiency of the system in bulk polymers, liquid (or low fiber volume) polymers, particulate composites, or low-volume fraction fiber-reinforced materials with inferior mechanical properties. [1,2] Comparatively, limited research has been undertaken on self-healing in advanced FRP composite materials, specifically based on systems commonly used in industry or those that possess high-performance characteristics.Two broad categories of self-healing systems can be found in the available literature: [3] i) intrinsic self-healing systems, which can heal a crack through interactions (physical or chemical) at the molecular level; ii) extrinsic self-healing systems, which This paper sets out to review the current state of the art in applying selfhealing/self-repair to high-performing advanced fiber-reinforced polymer composite materials (FRPs). A significant proportion of self-healing studies have focused so far on developing and assessing healing efficiency of bulk polymer systems, applied to particulate composites or low-volume fraction fiber-reinforced materials. Only limited research is undertaken on self-healing in advanced structural FRP composite materials. This review focuses on what is achieved to date, the ongoing challenges which have arisen in implementing self-healing into FRPs, how considerations for industrialization and large-scale manufacture must be considered from the outset, where selfhealing may provide most benefits, and how a functionality like self-healing can be validated for application in real structures. ...

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Thermal mending in immiscible poly(ε-caprolactone)/epoxy blends

Cited by 36 publications

References 51 publications

Novel Poly(Caprolactone)/Epoxy Blends by Additive Manufacturing

Novel Poly(Caprolactone)/Epoxy Blends by Additive Manufacturing

Influence of Morphology on the Healing Mechanism of PCL/Epoxy Blends

Progress in Self‐Healing Fiber‐Reinforced Polymer Composites

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