Morphological and Mechanical Characterization of Nanostructured Thermosets from Epoxy and Styrene-block-Butadiene-block-Styrene Triblock Copolymer

Abstract

Styrene-block-butadiene-block-styrene (SBS) triblock copolymers epoxidized at several epoxidation degrees by hydrogen peroxide in water/dichloroethane biphasic system were blended with epoxy based on diglycidyl ether of bisphenol A (DGEBA) and DDM (4,4′-diaminodiphenyl methane) as curing agent. The incorporation of epoxidized block copolymers in epoxy resulted in the formation of nanostructured blends. The morphologies of the blended polymers were studied using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS) analysis. The key factor controlling the morphology is the mole percentage of epoxidised butadiene units in SBS. In fact, the morphologies changed from macroscopic phase separated domains in unmodified SBS to nanostructured domains in epoxidised SBS and the resulting morphologies were fixed by the cross-linking reaction. Nanostructured morphologies such as worm-like and spherical micelles (radius 8 nm) were generated due to reaction induced phase separation of PS phase followed by the self-assembly of PB sub chains. The mechanical properties such as fracture toughness (stress field intensity factor (K IC )), and impact strength of these blended systems were measured. It was established that nanostructured blends significantly improved fracture toughness and impact strength. Field emission scanning electron micrographs of fractured surfaces were examined to understand the toughening mechanism.

Improving the toughness of epoxy with a reactive tetrablock copolymer containing maleic anhydride

“…In this study, neat epoxy showed a K IC value of about 1 MPa m 1/2 . Because the critical stress intensity value of the 10 wt % epoxidized polystyrene-block-poly(n-butyl acrylate)-block-polystyrene in DGEBA/DDM blends was slightly higher than that of the neat epoxy, as reported in literature, 29 the 69% increase in K IC of the 10 wt % SMA-SBAS in the DGEBA/DDM blends was attributed to the strong interfacial adhesion between reactive BCP and the epoxy matrix. Cured blends containing 5 and 10 wt % of SMA-SBAS with nanospheres and vesicles imparted 31 and 69% increases in K IC , respectively.…”

“…20 The main concept of BCPs in modifying epoxy blends is their miscibility in epoxy blends. [28][29][30] In previous studies, the reactive groups introduced into the BCPs were not able to react with DGEBA or were randomly distributed. 16,19,[21][22][23][24][25][26] In the cases where the BCP does not have any segments miscible with the epoxy resin, it is essential to chemically modify one of the blocks to make it miscible with the epoxy resin.…”

Effect of clay and PEO-PPO-PEO block copolymer on the microstructure and properties of cyanate ester/epoxy composite

“…5 a. The large specific surface areas can be provided by nano-sized PPO particles, which will help stress transfer between PPO particles and BCE/EP matrix [32]. Nano-sized PPO particles have very high surface areas and thus relatively more energy will be consumed due to the nano-sized PPO particles to prevent the production of microcracks and propagation of the flaws when the samples suffer impact testing, and hence contributing to the improvements in the impact resistance.…”

Polymer Blends: State of the Art, New Challenges, and Opportunities

“…In general, the compatibility between the polymer phases decides the properties of a heterogeneous polymer blend [6,7]. The interface between the polymer phases in a polymer system is characterized by the interfacial tension which, when approaching zero, causes the blend to become miscible.…”