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

Abstract

Epoxies are commonly used as a matrix in a wide range of aerospace applications, electronics, and various diverse industrial applications. Their excellent electrical and chemical properties, high strength, low shrinkage, and low absorption of moisture make them the most used matrix system. Besides incredible mechanical and thermal properties, the highly crosslinked [1] microstructure makes, however, an unmodified epoxy system brittle, resulting also in poor resistance to crack initiation and propagation. As a consequence, epoxies must usually be toughened by the addition of a second component. Various approaches were followed by researchers to toughen brittle epoxy-based systems e.g. the use of chemical modifications that involve chain extenders or plasticizers. The second most common method is introduction of a second phase i.e. liquid rubber. The different types of rubber modifiers that have been in practice so far are a carboxyl-terminated copolymer of butadiene and acrylonitrile (CTBN) [2] or an amine-terminated copolymer of butadiene and acrylonitrile (ATBN) [3]. Rezaifard et al. [4] have used poly(methyl methacrylate) (PMMA) grafted natural rubber instead of CTBN for toughening of epoxy, resulting in an improved adhesive joint failure strength 384

The effect of nano- and micron-scale filler modified epoxy matrix on glass-fiber reinforced polymer insulator component behavior

“…For core-shell rubber particles (CSR), different trends in Tg have also been reported, e.g. a slight increase by Quan et al 13 when adding n-silica (4 wt %) to CSR at volume fractions between 3% and 16%, unchanged Tg for the addition of CSR by, e.g., Bain et al, 11 Chen et al, 30 Bajpai et al 31 and decreasing Tg for the addition of liquid rubber, but no change for that of CSR by Maazouz et al 32 The data shown in Figure 2 clearly indicate that addition of the roughly micron-size CaCO 3 particles did not change Tg of the epoxy significantly for the epoxy system investigated here (within the measurement resolution of the DMTA of about 2 C), while adding various types of nanoclay and also of hybrid types of nanoparticles, including n-silica, CSR, and combinations of these showed a decrease from 157 C down to about 139 C with increasing total amount of filler. This seems to contradict some of the literature cited above.…”

Studies on the Modification of Commercial Bisphenol-A-Based Epoxy Resin Using Different Multifunctional Epoxy Systems

“…The highly crosslinked networks that form, on the other hand, limit the network structure's mobility and induces brittleness in the cured system. The addition of soft fillers like rubber or thermoplastics to thermosets plasticize the structure, enhancing fracture toughness whilst lowering stiffness, strength, and glass transition temperature [1][2][3]. Similarly, Improvements in strength and modulus have also been reported where ceramic-based nanoparticles have been dispersed prior to curing [4][5][6][7][8][9].…”