Cure Kinetics of Epoxy/Thermoplastic Blends

Francis, Bejoy

doi:10.1007/978-3-319-18158-5_22-1

Cited by 4 publications

(3 citation statements)

References 101 publications

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“…In the last few decades, epoxy resins-thanks to their high mechanical properties, thermal and chemical stability, good processability, and adhesion to different substrates-have found wide application in different fields [1][2][3]. However, in many technological applications, the mechanical properties of epoxy resin are not able to fulfill all the technical requirements imposed during the service conditions [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

Novel Poly(Caprolactone)/Epoxy Blends by Additive Manufacturing

2020

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“…With a 5-molar excess of DA a complete abatement is achieved, on the contrary, with a 3-molar excess, MDA settles around 100 ppm. This trend may be explained considering that in all three cases other reactions involving other less reactive NÀ H groups [47,48] present in the recycled polyol occur, however the higher the molar excess, the higher the diminishing of MDA content. Diamines, indeed, present four reactive sites [49] represented by each active hydrogen linked to the nitrogen.…”

Section: Deamination With 2-ehgementioning

confidence: 91%

Deamination of Polyols from the Glycolysis of Polyurethane

Donadini,

Boaretti,

Scopel

et al. 2023

Chemistry A European J

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Methylenedianiline (MDA) is a secondary, undesired, product of the glycolysis process of polyurethane (PU) scraps due to hydrolysis and pyrolysis side reactions. As an aromatic and carcinogen amine, MDA poses different problems in handling, transporting, and labelling recycled polyols derived from glycolysis, hindering the closure of PU recycling loop.Aiming to provide a solution to this issue, in this work different deaminating agents (DAs) where investigated with the purpose of analyzing their reactivity with MDA. A first part of the study was devoted to the analysis of MDA formation as a function of reaction time and catalyst concentration (potassium acetate) during glycolysis. It was observed that the amount of MDA increases almost linearly with the extent of PU depolymerization and catalyst content. Among the DAs analyzed 2‐ethylhexyl glycidyl ether (2‐EHGE), and acetic anhydride (Ac2O) showed interesting performance, allowing to diminish MDA content below the limit for labelling prescription in 30 minutes. PU rigid foams were therefore synthesized from the corresponding recycled products and characterized in terms of thermal and mechanical performance. Ac2O‐deaminated polyols led to structurally unstable foams with poor compressive strength, while 2‐EHGE‐deaminated products allowed the production of foams with improved mechanical performance and unaltered thermal conductivity.

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“…The number of epoxy and amine reactive groups are the key elements that drive the properties of epoxy polymers. A judicious choice of an epoxy monomer and the further curing agent permits thus to obtain highly crosslinked epoxy thermosets with outstanding physico-chemical properties [8][9][10][11]. Other parameters like the preparation conditions, the duration and the temperature of curing are of prime importance in the network structure of a given epoxy based polymer [12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%