Toughening of semi‐IPN structured epoxy using a new PEEK‐type polymer via in situ azide–alkyne click polymerization

ABSTRACT A new poly(ether ether ketone)‐type polymer prepared from 1,4‐bis(azidomethyl)benzene (p‐BAB), 4,4′‐bis(2‐propynyloxy)benzophenone (PBP) or 4,4′‐sulfonylbis(propynyloxy)‐benzene (SBP) via azide–alkyne click polymerization was used as a toughening agent to improve the fracture toughness, thermal stability of the toughened epoxy and reduce its viscosity during processing. The epoxy was toughened by the polymer [poly(p‐BAB/PBP)] via in situ polymerization during the curing process, which largely decreased viscosity during the epoxy mixing process compared to that of a neat epoxy. The fracture toughness of 5 wt % poly(p‐BAB/PBP) toughened epoxy is two times higher than that of the neat epoxy, and even higher than that of the polyethersulfone‐type [poly(p‐BAB/SBP)] toughened epoxy using the same amount of toughening agents. In addition, the T g of this toughened epoxy is higher than that of engineering plastic, which could be regarded as the evidence for the excellent thermal resistance. These phenomena might be attributed to the formation of semi‐interpenetrating polymer networks composed by the epoxy network and the linear poly(p‐BAB/PBP). In situ poly(p‐BAB/PBP) has unique advantages such as decreased viscosity and improved thermal stability in comparison with in situ poly(p‐BAB/SBP). These features are significant for the development of carbon‐fiber‐reinforced plastics as alternate materials to metals. Therefore, in situ poly(p‐BAB/PBP) is a promising toughener for epoxy systems. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48178. The epoxy resin was toughened by a novel poly(ether ether ketone)‐type polymer via in situ azide–alkyne click polymerization during the curing process, which simultaneously improved the fracture toughness and heat resistance of a cured toughened epoxy resin and reduce its viscosity during processing, attributing to the formation of semi‐interpenetrating polymer networks composed by the epoxy network and the linear polymer.