Effect of immersion time in water on the tensile properties of acetylated steam-exploded acacia mangium fibers filled polyethylene composites
2006
R.M., Taib | S., Ramarad | Z.A., Mohd Ishak | H.D., Rozman
Steam-exploded fibers were derived from steam explosion of Acacia mangium wood chips. The fibres, after undergoing water and alkali extractions (AEF) were acetylated with acetic anhydride. Weight percent gain (WPG) of the acetylated fibers (AAEF) were 4.9, 13.7 and 18.3. Composites of high-density polyethylene (HDPE) and acetylated steam-exploded Acacia mangium fibers were prepared using 2 roll mill and compression molding. The composites (tensile specimens)were immersed in water at room temperature for 30 days. All composites absorbed water but the water uptake was found to decreased with increasing WPG of AAEF fibers. Acetylation had decreased the number of accessible hydroxyl groups of AAEF fibers to interact with water molecules. The tensile properties of the immersed samples were tested after 2,4, and 6 days of water immersion. The tensile properties of HDPE-AEF and HDPE-AAEF composites were observed to decreased with immersion time. HDPE-AEF composites showed a reduction in maximum stress and tensile modulus after 2 days of water immersions. HDPE-AAEF composites, on the other hand, showed a distinct decreased in both properties after 4 days of water immersion. All composites exhibited higher percent decreased in tensile modulus than maximum stress. The decrease in tensile modulus in particular was lower for composites filled with AAEF fibers of higher WPG. Tensile modulus too was found to decrease linearly (R2=0.80) with increasing water uptake to the composite system. Acetylation did not improve fiber-matrix interaction but did reduce the amount of water absorbed by the composite system.
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