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

Abstract

The effect of adding different types of soft block copolymer on the tensile properties, fracture mechanic properties, and thermo-mechanical properties of bisphenol F based epoxy resin were studied. Two different self-assembling block copolymers, (a) constituting of a center block of poly (butyl acrylate) and two side blocks of poly (methyl) methacrylate-co-polar co-monomer (BCP 1) and (b) poly(ethylene oxide)-b-poly(butylene oxide) (PEO-PBO) diblock copolymer (BCP 2), were used with an epoxy-hardener system. The maximum fracture toughness and fracture energy were measured as KIc = 2.75 MPa·m1/2 and GIc = 2.37 kJ/m2 for the 10 wt % of BCP 1 modified system, which were 366% and 2270% higher in comparison to reference epoxy system, and a 63% reduction in tensile strength was also observed. Similarly, for BCP2 modified systems, the maximum value of KIc = 1.65 MPa·m1/2 and GIc = 1.10 kJ/m2 was obtained for epoxy modified with 12 wt % of BCP2 and a reduction of 32% in tensile strength. The fracture toughness and fracture energy were co-related to the plastic zone size for all the modified systems. Finally, the analysis of the fracture surfaces revealed the toughening micro-mechanisms of the nanocomposites.

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

“…The knowledge of the critical stress intensity factor K Ic , the elastic modulus E t and Poisson's ratio ν (~0.35) [18] allows calculating the critical energy release rate G Ic defined in Equation (3):(3)…”

“…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

“…4,5 As an alternative, the addition of CSR particles showed also an improvement in fracture toughness of bulk epoxy systems. Various studies explained that the BCP morphology and thus the fracture properties of epoxy BCP systems depend on the BCP-block composition, 17 the molecular weight of the immiscible block, 10 the length of the BCP 18,19 the curing agent, 20 and the curing process. The main toughening mechanisms responsible for the increase in fracture toughness are cavitation of the rubbery core followed by plastic void growth and shear deformation in the epoxy matrix.…”

“…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. Various studies explained that the BCP morphology and thus the fracture properties of epoxy BCP systems depend on the BCP-block composition, 17 the molecular weight of the immiscible block, 10 the length of the BCP 18,19 the curing agent, 20 and the curing process. 21 Many authors have studied the use of filler particles such as silica (SiO 2 ) 22,23 silk fibroin, 24 bamboo fibrils, 25 and glass.…”

PPG-Terminated Tetra-Carbamates as the Toughening Additive for Bis-A Epoxy Resin

“…Thus, understanding the interaction and miscibility between components becomes the key to achieve the ordered morphology in high-performance epoxy polymers. There is a large amount of literature on the subject of mediating the interaction and miscibility of PEO blocks with the epoxy matrix to get the ordered morphology through the appropriate design of the molecules of BCs, such as the PEO/PPO ratio, reducing molecular weight, introducing epoxy-phobic alkane blocks, and epoxidizing the block [11,14,15,16].…”