Transparent and toughening epoxy thermosets modified by linear telechelic polymer containing rigid spiroacetal moieties: Uncovering the relationship between the heterogeneous crosslinked network and thermoset performances

Abstract

Spiroacetal moieties containing linear telechelic polymers (LTPs) with two terminal epoxy groups were facilely synthesized via the successive thiol‐ene and thiol‐epoxy click additions. The LTPs were incorporated into epoxy matrix to fabricate the transparent and toughening thermosets. In term of the miscibility of epoxy with the adduct of ethanedithiol and 3,9‐divinyl‐2,4,8,10‐tetraoxaspiro[5.5]undecane (BTU), it is proposed that the size of the formed nanostructures was small enough to allow light penetrate. Therefore, the modified thermosets were transparent, which was further confirmed by small‐angle X‐ray scattering (SAXS) measurements. The LTPs with an alternating structure of rigid spiroacetal moiety and soft thioether could formed heterogeneous crosslinked networks (HCNs) and obviously toughen epoxy thermosets. Flexural strength increased from 1.06 GPa for neat epoxy to 2.09 GPa for toughening thermosets modified with 15 wt% LTPs. The stress field intensity (KIC) value reached up to 3.93 by more than 125% compared with that of the control sample (1.75). This work uncovered the role of HCNs on performance and paved a way for technological advances toward transparent and toughening materials in epoxy thermosets.

Fabrication of cellulose/plant oil based flexible epoxy thermoset with excellent UV‐blocking performance

“…Epoxy thermosets as important thermosetting polymers have attached more and more attentions due to their advantages in excellent mechanical property, high thermal stability, and chemical resistance, and have been widely applied in adhesives, coatings, electronic packaging, and advanced composites. [1][2][3][4] Typical epoxy thermosets are derived from petroleum-based diglycidyl ether of bisphenol A, but the intrinsic rigid structure of bisphenol A made the cured resin too brittle to be applied in high-end fields. [5][6][7] Meanwhile, social and academic concerns on environmental pollution and sustainable use of fossil fuel have driven the development of bio-based flexible epoxy thermosets to a new level.…”