Synthesis and characterization of polybenzoxazine/layered double hydroxides nanocomposites

Abstract New polybenzoxazine/LDH nanocomposites were synthesized using three types of LDH (layered double hydroxides) and various LDH concentrations (1, 5, 10 and 30% wt.). Microcomposites were obtained if unmodified LDH (LDH A or LDH B) was used, while exfoliated nanocomposites were produced if modified LDH with sodium dodecyl sulfate (SDS) was employed. The influence of LDH on the benzoxazine polymerization was investigated by DSC showing a catalytic effect on the polymerization process, which is quite significant if LDH–SDS is used, a decrease with ∼20° of the temperature corresponding to the maximum rate of polymerization being noticed. XRD, SEM and TEM were employed to determine the morphology of the composite materials. Thus high exfoliation degree was revealed for 5% LDH–SDS. The introduction of LDH in the polybenzoxazine matrix decreases the thermostability of the neat resin considering the value of the temperature at which the mass loss is 1% (T d1% ), but stabilizes the composite material at higher degradation stages promoting the residual char formation. The best thermal properties were achieved for the exfoliated nanocomposites containing 5% LDH–SDS, a good interaction between LDH–SDS and polybenzoxazine being the key factor for the overall properties of the nanocomposites.