SCIENTIFIC PAPERS ACADEMIC JOURNAL OF MANUFACTURING ENGINEERING, VOL. 8, ISSUE 1/2010 24 INFLUENCE OF ALKALINE TREATMENT OF ALFA FIBER ON THE MECHANICAL, VISCOELASTIC, THERMAL AND MORPOLOGICAL PROPERTIES OF PVC/ALFA COMPOSITES Amar BOUKERROU 1 , Md. Ameziane RAHMOUNE 1 and Mustapha KACI 1 ABSTRACT: This paper deals with plastic-wood composites based on poly(vinyl chloride) (PVC) and alfa fiber (strippa tenacissima) prepared by melt blending in a high-speed twin steel-wall mixer at various loadings, i.e. 5 and 15 wt. %. In order to improve adhesion between alfa fiber (strippa tenacissima) and matrix, alkaline treatment was used. The effect of the incorporation of virgin and treated fiber in the poly(vinyl chloride) matrix on mechanical, thermal stability, viscoelastic properties and morphology of composites was followed by various techniques, especially tensile testing, thermogravimetric analysis (TGA), Dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM). The experimental results indicated that the chemical treatment of alfa fiber flour with NaOH improved the thermal stability of fiber alfa. The mechanical properties of the treated composites were improved; expect young modulus (for PVC filled with 5 % w/w, 15 %w/w of alfa treated). Also the sodium hydroxide improves the interactions between the two composites components and promoted better dispersion of the filler (at a content of 15 % w/w) in the matrix. The thermal characterization of PVC filled with 15 %w/w of alfa revealed an decrease in the onset temperatures of decomposition for the treated composites. Further, SEM revealed that the surfaces of modified fiber composites are smoother and better dispersion than virgin fiber composites. KEY WORDS: wood plastic composites, Alfa fibers, sodium hydroxide treatment, PVC, thermal and mechanical properties. 1 INTRODUCTION In the last decade, polymer composites filled with natural lignocellulosic fibers have attracted the attention of many researchers and technologists (Belgacem, 2005). Both polymer matrices and natural filler systems have been widely investigated (Ferreira, Antonio, 2003). As a matter of fact, Oksman and Lindberg (Oksman, 1997) as well as the team of Liano et al. (Liano, 1997) studied the mechanical behavior of composites based on polyethylene and wood flour samples. On the other hand, Kaci et al. (Kaci, 2009) investigated the mechanical behavior of polypropylene/wood flour composites. Some authors examined also the mechanical behavior of PS/PEHD/wood flour (Xu, 2001). On the contrary, the research work dealing with PVC/wood flour composites is rather scarce. Although, some papers have been reported in literature including those of Mengeloglu and Matuana (Matuana, 2001), Pedro and Monteiro (Pedro, 2001) which have been devoted to a comparative study of the mechanical behavior of PVC/CaCO 3 with PVC/Agalmatolithe, while Sain et __________________________________________ 1 Laboratoire des Matériaux Organiques, University A. Mira of Bejaia, 06000 Algeria E-mail: aboukerrou@yahoo.fr al. (Sain, 2000), investigated the filled PE/WF, PVC/WF, and PP/ WF formulations. On the other hand, there is a few works, which has been reported in literature on alfa fibers and their uses in many applications involving mainly the production of food for animals. In the present work, Algerian alfa was used as filler to reinforce poly(vinylchloride) composites. The recovery of this renewable waste may have a double positives impact, economic, and ecological. Chemically, the alfa contains cellulose, hemicellulose, and lignin, and cannot be processed as plastics due to both the high degree of crystallinity in the cellulose and the three- dimensional network. To solve this problem, this study examined the plasticization of the alfa by chemical treatment with sodium hydroxide, therefore expecting better processability of the composite materials and higher interfacial adhesion between the polymer and the filler. 2 EXPERIMENTAL 2.1 Materials All the PVC-alfa fiber composite formulations used in this work were prepared based on PVC type 4000 M produced by the Algerian Company named ‘Entreprise Nationale des Industries