Epoxy/layered double hydroxide (LDH) nanocomposites: Synthesis, characterization, and Excellent cure feature of nitrate anion intercalated Zn-Al LDH

Layered double hydroxides (LDHs) belong to two-dimensional (2D) nanoparticle family. Best known as anionic clays, LDHs were the promising choice for a wide range of applications. Despite the widespread research on synthesis and application of LDH as an additive in thermoset resins, a few was known about its curing ability. In this work, Zn-Al LDH intercalated with nitrate anion (Zn-Al-NO3) was synthesized, characterized and incorporated into epoxy resin at low content of 0.1 wt.%. Fourier-transform infrared spectrophotometry (FTIR), X-ray diffractometry (XRD), and thermogravimetric analysis (TGA/DTG) techniques were employed to characterize LDH. Nonisothermal differential scanning calorimetry (DSC) at different heating rates allowed for evaluating curing state of epoxy/Zn-Al-NO3 LDH nanocomposites containing 0.1 wt.% of LDH in terms of Cure Index universal criterion. Zn-Al-NO3 LDH assisted epoxy in curring with an amine precursor resulting in much more heat release in a shorter curing temperature interval with respect to the blank epoxy system whatever heating rate. Such promising feature was signaled by Excellent cure state demonstrated by Cure Index, which was attributed to Lewis acid effect of Zn that catalyzed epoxy curing reaction. Moreover, it was discussed that an enlarged LDH interlayer space brought about by incorporation of nitrate anion between layers facilitated the curing reaction.