PVA Nanocomposites Reinforced with Cellulose Nanofibers from Oil Palm Empty Fruit Bunches (OPEFBs)

*Corresponding author: Farah Fahma, Department of Agroindustrial Technology, Faculty of Agricultural Engineering and Technology, Bogor Agricultural University, Bogor, Indonesia. E-mail: farah_fahma@yahoo.com Akio Takemura, Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan. E-mail: akiot@mail.ecc. u-tokyo.ac. jp Received: 01 March 2016; Revised: 28 February 2017; Accepted: 09 March 2017; Published Online: 19 March 2017 Fahma, et al.: PVA nanocomposites reinforced with cellulose nanofibers from oil palm empty fruit bunches (OPEFBs) 324 Emir. J. Food Agric ● Vol 29 ● Issue 5 ● 2017 groups on PVA matrix are expected to interact with the hydrophilic surfaces of the cellulose nanofibers, leading to strong hydrogen bonding. PVA-based fibers have been considered as an attractive choice in tissue scaffolding, filtration materials, membranes, optics, protective clothing, enzyme immobilization, drug release, and so on (Peresin et al., 2010). Gea et al. (2010) prepared bacterial cellulose-PVA nanocomposites by an in-situ process. Meanwhile, Lu et al. (2008) prepared PVA composites reinforced with microfibrillated cellulose (MFC). The mixing process between MFC and PVA solution was done by 1 min of sonication time and followed by stirring for 24 h to let the polymer penetrate into the cellulose network. The tensile strength and modulus increased with increasing the MCC content up to 10 wt% and then tends to level off at higher MFC content. Cheng et al. (2009) prepared PVA nanocomposites reinforced with cellulose fibrils (regenerated cellulose fibers, pure cellulose fibers, and MCC). The mixture solution of PVA nanocomposites was sonicated for 1 min with 50% power level. Adding more than 6 wt% cellulose fibrils did not increase more strength and modulus. Chen et al. (2008) prepared PVA-pea starch nanocrystals composites by adding glycerol. The mixture solution was stirred for 30 min at 100oC. The tensile strength and elongation at break of nanocomposite films with 5 and 10 wt% of nanocrystals were slightly higher than that of neat PVA film. With an increase of cellulose nanocrystals, the tensile strength and elongation at break of nanocomposite films decreased and become lower than that of neat PVA film. Cho and Park (2011) prepared PVA nanocomposites reinforced with nanocellulose isolated by sulfuric acid hydrolysis using commercial microcrystalline cellulose (MCC). The MCC added in PVA matrix was 1, 3, 5, and 7 wt% loadings. The PVA nanocellulose suspension was further stirred mechanically for 2 h and sonicated for 10 min. The tensile strength and modulus increased with an increase in the nanocellulose content up to 5 wt% followed by leveling off at higher nanocellulose content. Lee et al. (2009) prepared PVA composite films reinforced with nanocellulose obtained by acid hydrolysis of MCC at different hydrobromic acid (HBr) concentrations. The nanocelluloses added to the PVA solution were 1, 3, and 5 wt%. The mixture was stirred at 80oC for 2 h and followed by ultrasonication for 1 h. The nanocellulose loading of 3 and 5 wt% to PVA matrix gradually decreased the tensile strength. Sonication is often used in the dispersion of nanoparticles into polymer matrix. The basic principle of the enhanced dispersion is the ultrahigh shear rate attained during cavitation events (Huang et al., 2009). Although many works have been done on the PVA nanocomposites reinforced with cellulose nanofibers, how long the sonication treatment effectively help dispersing nanofibers into the matrix is not clear. Therefore the objective of this study is to investigate the effect of sonication time on the morphology and properties of PVA cellulose nanocomposite. MATERIALS AND METHODS