Nanocellulose reinforced PVA composite films: Effects of acid treatment and filler loading

Abstract

Nanocellulose was prepared by acid hydrolysis of microcrystalline cellulose (MCC) at different hydrobromic acid (HBr) concentrations. Polyvinyl alcohol (PVA) composite films were prepared by the reinforcement of nanocellulose into a PVA matrix at different filler loading levels and subsequent film casting. Chemical characterization of nanocelluloses was performed for the analysis of crystallinity (X c ), degree of polymerization (DP), and molecular weight (M w ). The mechanical and thermal properties of the nanocellulose reinforced PVA films were also measured for tensile strength and thermogravimetric analysis (TGA). The acid hydrolysis decreased steadily the DP and M w of MCC. The crystallinity of MCC with 1.5 M and 2.5 M HBr showed a significant increase due to the degradation of amorphous domains in cellulose. Higher crystalline cellulose showed the higher thermal stability than MCC. From X-ray diffraction (XRD) analysis, nanocellulose samples showed the higher peak intensity than MCC cases. Reduction of MCC particle by acid hydrolysis was clearly observed from scanning electron microscope (SEM) images. The tensile and thermal properties of PVA composite films were significantly improved with the increase of the nanocellulose loading.

Properties of Polymer Composites with Cellulose Microfibrils

“…In the obtained PVA thermograms (Fig. 10) three main weight loss regions can be observed (Lee et al, 2009b;Qua et al, 2009). All the samples show an initial weight loss in the region 75 -150 0 C caused by the evaporation of water.…”

“…The hydrogen bonding between the OH groups of cellulose fibers and similar group of PVA matrix led to improved adhesion between phases which resulted in improved mechanical properties. Lee et al (2009b) explained an increase of about 70% of the elastic modulus and up to 55% of the tensile strength by the intermolecular forces between cellulose fibers and PVA matrix. b.…”

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

“…4 shows that all PVA-cellulose nanocomposites start to degrade at higher temperatures than those of neat PVA. This indicates that the addition of cellulose nanofiber can improve thermal stability of PVA, thus confirming the enhanced thermal stability due to a strong hydrogen bonding between the hydroxyl groups of nanofibers and the PVA matrix (Lee et al, 2009). The 0-9 min of sonication time did not affect the thermal stability of PVA nanocomposites while with 20 min sonication time the degradation temperature shifted to lower temperatures.…”

“…The third region occurred above 390°C, probably due to the cleavage backbone of PVA nanocomposite films or the decomposition of carbonaceous matter. The total weight loss in this range was more than 95 wt% at 500°C (Lee et al, 2009;Lu et al, 2009).…”

“…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%.…”