Experimental analysis of toughness and modulus of rupture increase of sisal short fiber reinforced hemihydrated gypsum.pdf

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Composite Interfaces, Vol. 14, No. 7–9, pp. 605– 616 (2007)  VSP 2007.

Influence of chemical treatments on the interfacial adhesion between sisal fibre and different biodegradable polymers
V. ALVAREZ 1 , I. MONDRAGÓN 2 and A. VÁZQUEZ 1,∗
1 Research

Institute of Material Science and Technology (INTEMA), CONICET- Engineering Faculty, Juan B. Justo4302 (7600) Mar del Plata, Argentina 2 Materials and Technologies Group, Dpto. Ingeniería Química y M. Ambiente, Escuela Universitaria Politécnica, Euskal Herriko Unibertsitatea/Universidad del País Vasco, Pza Europa 1, 20018 Donostia-San Sebastián, Spain Received 11 June 2006; accepted 11 October 2006 Abstract—The influence of chemical treatments on the interfacial adhesion of sisal fibres andbiodegradable matrices were studied in the present work. For that purpose, four different polymers were used: polycaprolactone (PCL), cellulose acetate, MaterBi Z (a commercial starch/polycaprolactone blend) and MaterBi Y (a commercial starch/cellulose derivatives blend). Alkaline and acetylation treatments were performed on sisal fibres. Properties were determined by means of tensile tests, adhesionmeasurements and contact angle determination. The interfacial shear strength was correlated with the hydrophilic character of the material. Keywords: Biodegradable polymers; natural fibres; interfacial adhesion; chemical treatments; mechanical properties.

1. INTRODUCTION

Composites based on natural fibres and biodegradable polymers are very interesting from economical and environmental points ofview. The mechanical properties of composites are strongly dependent on the fibre–matrix interfacial bonding that is related to their physical and chemical characteristics [1]. All vegetable fibres are hydrophilic in nature, which is one of their main disadvantages because of their incompatibility with non-polar polymers, especially thermoplastics. In addition, their poor resistance to moisturemakes them less attractive for outdoor applications
∗ To

whom correspondence should be addressed. E-mail: anvazque@fi.mdp.edu.ar

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[2]. In order to improve the mechanical properties of natural fibre–thermoplastic polymer composites, several strategies have been developed: one of these is the surface modification of the fibres, and in this area, alkaline-treatment andacetylation are the most used. Since the interface plays a very important role in the stress transfer to the fibres, it is very useful to determine the adhesion level that affects the composite behaviour [3]. There are several methods used to describe the interfacial adhesion in fibrous composites. Micromechanical techniques, such as the microbond and pull-out tests allow the characterization of thefibre–matrix interfacial bonding [4 –10]. These techniques have been shown to be relatively simple, reproducible and very sensitive to the state of the interface, i.e. to fibre surface treatments [11 –16]. Only a few works about interfacial adhesion of natural fibre have been found in the literature [17], and most of them are based on thermosetting matrixes. Baley et al. [18] have demonstrated, usingthese techniques, that chemical treatments (sodium hydroxide + acetic anhydride or formic acid) improve the adhesion between flax fibre and unsaturated polyester resin. Eichhorn and Young [19] have shown that it is possible to obtain the work of adhesion from surface energy calculations in the case of hemp fibres and epoxy resin. The measurements indicate that the interfacial shear stress of epoxy/hempcomposites is as good as that of the glass/epoxy systems. Towo et al. [20] have studied the effect of the alkaline treatment of sisal fibre on the tensile and the interfacial shear strength. The treatment produces a moderate decrease in the average tensile strength but a substantial increase in the interfacial shear strength. Recently, Park et al. [21] have evaluated the interfacial shear...
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