Mechanism of the nanoparticle-catalyzed polymerization of furfuryl alcohol and the thermal and mechanical properties of the resulting nanocomposites

Bio-based polyfurfuryl alcohol (PFA) matrix nanocomposites were fabricated by in situ polymerization of furfuryl alcohol (FA) using (natural or organomodified) montmorillonite nanoclays (MMT) or cellulose whiskers (CW) as catalysts and as matrix modifiers, providing enhanced thermal performance. FTIR analysis shows the catalyst-dependent formation of gamma-diketones that are generated from hydrolytic ring cleavage of the furan rings along the PFA chain. Thermogravimetric Analysis (TGA) shows that the PFA-based nanocomposites exhibit a notable increase in the onset of degradation temperature compared to pure PFA. The oxidative degradation behavior, including degradation onset temperature and residual weight, was analyzed and compared for the various nanocomposites. The higher thermal stability of 30BMMT-PFA as compared with NaMMT-PFA is tentatively attributed to blocking of Brönstedt acidic sites on the clay surface by residues of the organic modifier. However, the highest thermal stability among the various PFA-based nanocomposites that were studied in this work was observed in those containing nanocellulose whiskers (CW), even at much lower volume loadings. Finally, in addition to their surprisingly remarkable thermal stability, CW-PFA nanocomposites also exhibited improved mechanical toughness over previously reported PFA systems.