Macromolecular Nanotechnology Cellulose whiskers reinforced polyvinyl alcohol copolymers nanocomposites Mehdi Roohani a,b , Youssef Habibi a , Naceur M. Belgacem a , Ghanbar Ebrahim b , Ali Naghi Karimi b , Alain Dufresne a, * a Ecole Française de Papeterie et des Industries Graphiques, Institut National Polytechnique de Grenoble (EFPG-INPG), BP65, 38402 Saint-Martin d’Hères Cedex, France b Department of Wood and Paper Technology, Faculty of Natural Resources, The University of Tehran, Karaj, P.O. Box 31585-4314, Iran article info Article history: Received 15 February 2008 Received in revised form 14 May 2008 Accepted 26 May 2008 Available online 2 June 2008 Keywords: Nanocomposite Cellulose Polyvinyl alcholol Whiskers abstract Nanocomposite materials were prepared from copolymers of polyvinyl alcohol and polyvi- nyl acetate and a colloidal aqueous suspension of cellulose whiskers prepared from cotton linter. The degree of hydrolysis of the matrix was varied in order to vary the hydrophilic character of the polymer matrix and then the degree of interaction between the filler and the matrix. Nanocomposite films were conditioned at various moisture contents, and the dynamic mechanical and thermal properties were characterized using dynamic mechanical analysis and differential scanning calorimetry, respectively. Tensile tests were performed at room temperature to estimate mechanical properties of the films in the non linear range. All the results show that stronger filler/matrix interactions occur for fully hydrolyzed PVA compared to partially hydrolyzed samples. For moist samples, a water accumulation at the interface was evidenced. The reinforcing effect was found to be all the higher as the degree of hydrolysis of the matrix was high. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Poly(vinyl alcohol) (PVA) is the largest synthetic water- soluble polymer produced in the world [1]. It is prepared by the hydrolysis of polyvinyl acetate. The degree of solu- bility, and the biodegradability as well as other physical properties can be controlled by varying the molecular weight (M W ) and the degree of hydrolysis (saponification) of the polymer [2]. Indeed, the chemical characteristics of these polymers, e.g. the reactivity of the numerous hydro- xyl groups depends strongly on the residual acetyl group content or the degree of hydrolysis. In practice, the par- tially hydrolyzed grades can be considered as copolymers of vinyl alcohol and vinyl acetate. In the range from about 97 to 100 mol% (or fully hydrolyzed grades) hydrolysis the relationship between the degree of hydrolysis and proper- ties of the ensuing polymers produces very clear differ- ences in the property profiles 17 opening the way of using them in a broad field of applications, of among which ma- trix for biodegradable nanocomposites. In recent years, nanocomposites have attracted signifi- cant scientific attention because of their phenomenal elec- trical, barrier and mechanical properties. They are defined as composite materials for which one of the phases has at least one dimension in the nanometer range (1–100 nm). A large variety of nanocomposites have been prepared using PVA as a matrix and nanoreinforcement like layered sili- cate [4–8], silica [9–11], cadmium sulfide nanoparticles [12] and carbon nanotubes [13–15]. The preparation meth- ods are usually solution casting or in situ polymerization. As most of the present-day nanofillers used to prepare nanocomposites are inorganic, their processability, bio- compatibility and biodegradability are much more limited than those of naturally organic ones. 0014-3057/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.eurpolymj.2008.05.024 * Corresponding author. Tel.: +33 4 76 82 69 95; fax: +33 4 76 82 69 33. E-mail address: Alain.Dufresne@efpg.inpg.fr (A. Dufresne). European Polymer Journal 44 (2008) 2489–2498 Contents lists available at ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj MACROMOLECULAR NANOTECHNOLOGY