Mechanical properties of composites are strongly influenced by the quality of the fiber/matrix interface. The objective of this study was to evaluate the mechanical properties of polylactide (PLA) composites as a function of modification of sisal fiber with two different macromolecular coupling agents. Sisal fiber reinforced polylactide composites were prepared by injection molding, and the properties of composites were studied by static/dynamic mechanical analysis (DMA). The results from mechanical testing revealed that surface-treated sisal fiber reinforced composite offered superior mechanical properties compared to untreated fiber reinforced polylactide composite, which indicated that better adhesion between sisal fiber and PLA matrix was achieved. Scanning electron microscopy (SEM) investigations also showed that surface modifications improved the adhesion of the sisal fiber/polylactide matrix. 1. Introduction With the increasing of environmental protection consciousness, natural fibers as a group of environmental friendly reinforcements are in considerable demand in composites [1, 2]. Natural fibers such as flax, hemp, sisal, nettle and jute were the most common reinforced elements [2, 3]. Of course, natural fiber reinforced degradable polymers composite is likely more ecofriendly because that the reinforcement and the matrix (e.g., polylactide (PLA)) are readily biodegradable and such biocomposites are sometimes termed “green composites” [4, 5]. Natural fibers as reinforcement are familiar. However, there is also a major drawback associated with its application for reinforcement of polymeric matrices. The presence of hydroxyl and other polar groups in natural fibers constituents makes them exhibit high hydrophilic nature, which leads to incompatibility and poor wettability in a hydrophobic polymer matrix, and weak bonding in the fiber/matrix interface [6]. Herewith, there are many problems in dealing with the interface of natural fiber and polylactide. Several approaches have been studied, such as surface modification of cellulose (e.g., esterification of cellulose and graft copolymerization onto cellulose substrates) and the use of some compatibilizers (e.g., maleated polylactide and isocyanate [7–11]). Nevertheless, only a limited number of studies had achieved good results. And there is no commercial sale of such interfacial compatibilizers in the market. Among the various natural fibers, sisal fiber is fairly coarse and inflexible. It possesses moderately high specific strength and stiffness, durability, ability to stretch, and resistance to
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