Bio-based nanocomposites by in situ cure of phenolic prepolymers with cellulose whiskers.pdf

Bio-based nanocomposites by in situ cure of phenolic prepolymers with cellulose whiskers Hongzhi Liu ? Marie-Pierre G. Laborie Received: 26 October 2010 / Accepted: 10 January 2011 / Published online: 26 January 2011  Springer Science+Business Media B.V. 2011 Abstract A series of resole-type phenolic resin- based nanocomposites, uniformly filled with cellulose nanowhiskers (CNWs), was successfully fabricated via direct solution mixing, then solvent-exchange with DMF and finally stepwise thermal curing. Dynamic mechanical analysis evidenced a moderate reinforcing effect with a minimum CNWs weight content of 5.0 wt% especially above the resin glass transition temperature (Tg). The Halpin–Kardos model provided a good description of the CNWs reinforcing effect, suggesting perhaps the contribu- tion of whiskers/matrix interactions rather than that of whiskers/whiskers interactions. Differential scan- ning calorimetry (DSC) further indicated that the nanowhiskers enhanced the resin cure, resulting in a more extensive degree of cure. Finally, the CNWs were found to only slightly lower the thermal stability of PF resins. In spite of a modest reinforcing effect, it is proposed that CNWs are also interesting fillers for high modulus and high Tg thermosetting resins that require high temperature cure. Keywords Thermoset  Cellulose whiskers  Nanocomposites  High glass transition temperature Introduction Phenolic resins (PF) result from the polycondensation of phenol and formaldehyde and yield highly cross- linked structural adhesives under basic conditions (Pizzi 1994). They combine excellent mechanical properties and chemical resistance and are widely used as adhesives for wood-based composites and glass or foundry binders. They are also valuable resins for honeycomb composites in aircrafts which require materials with high fire resistance. Recently, the reinforcement of phenolic matrix with nanofillers, such as carbon nanofillers (Yeh et al. 2008), layered silicates (Byun