Polycaprolactone/Modified Bagasse Whisker Nanocomposites with Improved Moisture-Barrier and Biodegradability Properties Mohammad L. Hassan, 1,2 Julien Bras, 3 Enas A. Hassan, 1 Shaimaa M. Fadel, 1 Alain Dufresne 3 1 Cellulose and Paper Department, National Research Center, Dokki, Giza 12622, Egypt 2 Center of Excellence for Advanced, Advanced Materials and Nanotechnology Group, National Research Center, Dokki, Giza 12622, Egypt 3 Laboratoire de G enie des Proc  ed  es Papetiers (LGP2), Unit  e Mixte de Recherche (France) Centre National de la Recherche Scientifique 5518, Grenoble Institute Polytechnique de Grenoble (INP), Pagora 461, Rue de la Papeterie, 38402, Saint-Martin-d’He `res Received 24 March 2011; accepted 7 October 2011 DOI 10.1002/app.36373 Published online 3 February 2012 in Wiley Online Library (wileyonlinelibrary.com). ABSTRACT: Bagasse whiskers isolated from bleached ba- gasse pulp were chemically modified with n-octadecyl iso- cyanate in the presence of dibutyltin dilaurate as a catalyst. The modified cellulose whiskers were used in ratios from 2.5 to 15% with polycaprolactone (PCL) polymer to prepare nanocomposite films by a solution/casting technique. The prepared nanocomposites were characterized with regard to their biodegradability in soil and moisture-barrier, mois- ture sorption, mechanical, thermal, and thermomechanical properties. The use of the modified cellulose whiskers resulted in improvements in the moisture-barrier, biodisin- tegration, and tensile properties of PCL. The nanocompo- sites containing different modified whisker loadings had very low moisture absorption (1.88–2.49%) after 4 weeks of exposure to 75% relative humidity, but these values were slightly higher than that of neat PCL (1.79%). Modified whiskers in the PCL matrix did not noticeably affect the glass-transition and melting temperatures of PCL. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 125: E10–E19, 2012 Key words: biodegradable; biopolymers; cellulose; nanocomposites INTRODUCTION Cellulose whiskers have attracted attention as rein- forcing fillers in nanocomposites because of their low cost, renewability, and the wide availability of the starting raw materials. Their length is usually up to several hundreds of nanometers, and their diame- ters are up to 10 nm. Cellulose whiskers have the advantages of a very high surface area, rodlike mor- phology with a high aspect ratio, possibility of sur- face chemical modification, and low density com- pared to other inorganic fillers. They are promising reinforcing materials with good mechanical responses to stress and significant improvements in mechanical properties at very low volume fractions. 1–3 One limitation of using cellulose whiskers is their noncompatibility and poor dispersion in hydropho- bic polymers. This results in poor interfacial adhe- sion between cellulose whiskers and the polymer matrix and negatively affects nanocomposite proper- ties. Thanks to the hydroxyl groups at the surface of cellulose, chemical modification with hydrophobic moieties makes it possible to prepare high-perform- ance nanocomposites with hydrophobic polymer matrices. The surface modification of cellulose whiskers by acetylation, esterification with long alkyl chains, silylation, and polymer grafting have already been reported to impart the hydrophobic surface. The hydrophobic surface of modified cellu- lose whiskers has resulted in good dispersion in nonpolar solvents and interfacial adhesion with hydrophobic polymer matrices. 4,5 Although most synthetic thermoplastic polymers are nonbiodegradable, polycaprolactone (PCL) is among the few synthetic biodegradable polyester polymers with a hydrophobic nature. 6 Composites of PCL with hydrophilic fillers require the use of com- patibilizers or the modification of the surface proper- ties of the hydrophilic filler to obtain high-perform- ance composites. In the area of PCL/cellulose nanocomposites, cellulose whiskers from ramie fibers were grafted by PCL chains with various molecular weights with an isocyanate-mediated reaction. The grafting of cellulose whiskers with PCL chains induced a decrease in the modulus values and an increase in the strain at break of the prepared nano- composites. 7 In another study, sisal whiskers and nanofibers were incorporated into the PCL matrix Correspondence to: M. L. Hassan (mlhassan2004@yahoo. com). Journal of Applied Polymer Science, Vol. 125, E10–E19 (2012) V C 2012 Wiley Periodicals, Inc.