One-pot nanofibrillation of cellulose and nanocomposite production in a twin-screw extruder

Abstract

Oil palm mesocarp fiber (OPMF) is rich in cellulose and suitable to be used as raw material for the production of cellulose nanofiber (CNF) and biocomposite. Recently, there have been reports on the use of CNF as filler in polypropylene (PP) for improving the mechanical properties of PP, however the process requires two steps: (i) nanofibrillation for CNF production and (ii) biocomposite compounding. In this study, a one-pot process was developed whereby nanofibrillation of cellulose and subsequently melt-blending of the CNF with PP were conducted at once, in a twin-screw extruder. Morphological analysis of the biocomposites by SEM showed that the cellulose was successfully fibrillated into CNF and compounded homogeneously with PP. The highest tensile strength, Young’s modulus, flexural strength, and flexural modulus recorded were 34.9 ± 0.5 MPa, 12.1 ± 0.1 GPa, 59.3 ± 1.3 MPa, and 2.3 ± 0.05 GPa, respectively when 3 % CNF was used in the biocomposite. The reinforcement of CNF-OPMF in PP improved the mechanical properties of the biocomposite by 33.4 % compared to neat PP. It is interesting to note that the addition of CNF managed to improve the crystallinity of the biocomposite (54.6 %) compared to neat PP (50.1 %), despite of the lower crystallinity of CNF compared to PP. This observation can be attributed to the high density of covalent bonds per cross-sectional area and the large number of hydrogen bonding sites. Additionally, the observation can be explained by the role of CNF in composite which acted as nucleation agent, which eventually increased the crystallinity of the biocomposite.