Synthesis and characterization of functional eugenol derivative based layered double hydroxide and its use as a nanoflame-retardant in epoxy resin†
Aiming to develop a multi-functional flame retardant for epoxy resins, a novel bio-based eugenol derivative containing silicon and phosphorus [((1,1,3,3-tetramethyldisiloxane-1,3-diyl)bis(propane-3,1-diyl))bis(2-methoxy-4,1-phenylene)bis(phenylphosphonochloridate), SIEPDP] was synthesized, and was further used to modify Mg–Al layered double hydroxide (SIEPDP-LDH). This modified SIEPDP-LDH was used as a novel nanoflame-retardant for bisphenol epoxy resins and compared with unmodified pristine LDH. X-ray diffraction (XRD) analysis justified that intercalation of SIEPDP into LDH increased the interlayer distance to 2.95 nm. Morphological analysis (XRD and TEM) revealed that the SIEPDP-LDH was dispersed well in the epoxy matrix in a partially exfoliated manner. Results from the cone calorimeter tests showed that even a low loading of SIEPDP-LDH into epoxy resin led to a significant decrease in heat release rate and total heat release compared to unmodified LDH/epoxy composites. More interestingly, SIEPDP-LDH/epoxy's UL-94 classification passed V-0 with only 8 wt% loading. Moreover, the addition of SIEPDP-LDH enabled the increase in the impact strength and modulus of the cured epoxy. These data indicated that SIEPDP-LDH could serve as not only a nanoflame retardant but a good reinforcing agent as well.