Novel Poly(Caprolactone)/Epoxy Blends by Additive Manufacturing

Abstract

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...

Healable Carbon Fiber-Reinforced Epoxy/Cyclic Olefin Copolymer Composites

“…In our previous study [49], we found a fracture toughness value (G IC ) for this COC grade of about 3 kJ/m 2 . This value is much higher than the fracture toughness value of the epoxy matrix, which was estimated to be about 1 MPa √ m [51]. Therefore, we can assume that the presence of COC in the epoxy matrix could play a positive effect on its fracture toughness, thus hindering the crack propagation.…”

“…A bicomponent epoxy system (EP) consisting of an epoxy base (EC157) and an aminic hardener (W 342) was kindly provided by Elantas Europe Srl (Collecchio, Italy). After a recommended curing cycle of 24 h at room temperature followed by 15 h at 60 • C, the resin manifested a glass transition temperature (T g ) of 85.4 • C [51]. COC granules (TOPAS ® 8007) were supplied by Ticona (Kelsterbach, Germany).…”

Healable epoxy‐based dielectric semi‐interpenetrating networks with different degrees of cross‐linking

“…The corresponding fluctuation is the result of plastic deformation at the gripping area of the specimens. 40 Among the pure EP samples, the stress-strain curves of EP-D400-00 and EP-HDA-00 display classical brittle failure without apparent plastic deformation. The tensile strength of EP-HDA-00 is about 40 MPa, which is higher than that of EP-D400-00 (about 25 MPa).…”

Three-Dimensional Printing Constructs Based on the Chitosan for Tissue Regeneration: State of the Art, Developing Directions and Prospect Trends

“…It is worth noting that the electro-spinning approach has gained considerable attention from biomedical experts all around the world for manufacturing various polymers, particularly CS-based polymer scaffolds loaded with drugs for biomedical and wound dressing purposes [ 172 , 173 , 174 , 175 , 176 , 177 , 178 , 179 , 180 ]. Application of CS-based biopolymers through 3D [ 181 , 182 , 183 , 184 , 185 , 186 , 187 , 188 , 189 , 190 , 191 , 192 , 193 , 194 , 195 , 196 ] printing for biomedical purposes especially as bio-ink in an effort to fabricate complex tissues will probably be an upcoming pattern of 3D printing materials progression. However, CS and CS/Col designed bio-printed skin tissue has not already obtained the FDA approval, taking into account the similarity of constructed materials with some other permitted materials.…”