Relationship between the mechanical properties of epoxy/PMMA-b-PnBA-b-PMMA block copolymer blends and their three-dimensional nanostructures

Abstract

Epoxy thermosets are applied as structural materials and adhesives in many industries, such as aerospace, automotive, and electronics, due to their excellent mechanical properties and heat/solvent resistance. In the applications, polymer blends have been studied to toughen the epoxy thermosets [1-14]. Among various toughening modifiers, block copolymers (BCPs) consisting of chemically distinct block chains have attracted attention in order to give nanostructured epoxy blends [15-40]. After the finding of the nanostructured epoxy blends with amphiphilic BCPs [15, 16], many BCPs were synthesized to study the nanostructures and the mechanical properties of the cured blends. Dean et al. [21] reported that methylenedianiline-cured DGEBA/ poly(ethylene oxide)-b-poly(butadiene) (PEO-b-PB) block copolymer blends showed a phase transition from spherical micelles to branched cylindrical micelles and finally to vesicles, as the volume fraction of the epoxy-miscible PEO block decreased. Ritzenthaler and coworkers [23, 24] studied epoxy/ ABC triblock copolymer blends. Raspberry-like nanostructures were identified in polystyrene-bpolybutadiene-b-poly(methyl methacrylate

High strength epoxy system modified with soft block copolymer and stiff core-shell rubber nanoparticles: Morphology, mechanical properties, and fracture mechanisms

“…Before testing, a notch was machined and then sharpened by tapping a fresh razor blade [34] into the material, so that a sharp crack was initiated with a length a 0 (0.45W ≤ a 0 ≤ 0.55W). The fracture toughness K Ic was then calculated by Equation 1, where F is the maximum force observed in the load-displacement curve and ao is the initial crack length for calculating α = a 0 /W and f(a 0 /W) as shown in Equations (1) and (2) [17]:…”

“…The results from the previous studies have demonstrated that block copolymer toughening has the potential to provide a higher toughness improvement compared to traditional homopolymers and random copolymer toughening agents. But the main problem involved in the addition of BCP is that they can reduce all other properties like elastic modulus, tensile strength, and T g [17,18]. Adding rigid particles can improve the strength and modulus of epoxy nanocomposites while increasing also its fracture toughness, and without decreasing the glass transition temperature.…”

Mechanical properties and fracture behavior of high‐performance epoxy nanocomposites modified with block polymer and core–shell rubber particles

“…Studies show that morphologies of these systems have a direct influence on the properties of modified systems. In contrast, totally different structures of triblock copolymer (ABA) toughened bisphenol A-based epoxy in the nanorange were reported by Kishi et al, 16 who quantified the morphology and respective fracture mechanical properties. 6 The use of CSR particles diminishes the possibility of incomplete phase separation which occur in case of liquid rubbers which hampers the properties like glass transition temperature (T g ) and elastic modulus.…”

Effect of Different Types of Block Copolymers on Morphology, Mechanical Properties, and Fracture Mechanisms of Bisphenol-F Based Epoxy System

“…Barsotti et al [6] reported a higher value of fracture toughness for an epoxy system modified with block copolymer poly (methyl methacrylate)-b-poly (butyl acrylate)-b-poly (methyl methacrylate) (MAM) than that of the epoxy system modified with CTBN at the same wt % of loading. Different researchers from their research have summarized that the BCPs are capable of toughening the epoxy system to a higher toughness when compared to traditional homopolymers and random copolymer toughening agents, but they also tagged the same BCPs as a reason for the reduction of elastic modulus, tensile strength and also the glass transition temperature [7][8][9][10][11][12]. Barsotti et al [6] compared the fracture toughness improvement ability of block copolymer and CTBN in the same epoxy system but using another block copolymer poly (methyl methacrylate)-b-poly (butyl acrylate)-b-poly (methyl methacrylate) (MAM).…”