Effect of acid hydrolysis on the properties of nanocrystalline cellulose-reinforced polyvinyl alcohol composites

Abstract

Cellulose nanocrystals (CNC) was extracted from Empty Fruit Bunch (EFB) fiber by different types of acid during acid hydrolysis. The acids used include sulphuric acid, hydrochloric acid and phosphoric acid. A few tests were carried out to determine the suitable CNC extracted from three acids which was suitable for the reinforcement of polyvinyl alcohol biocomposites. Due to the highest yield and stability of CNC extracted from sulphuric acid, it was choosen as a filler added into Polyvinyl Alcohol (PVOH) solution. Different content of CNC (1 wt%, 3 wt% and 5 wt%) was reinforced into the PVOH solution and produced a transparent film. Several tests were carried out to study the effect of different concentration of CNC on the mechanical properties, morphological structure and water absorbability of PVOH composites. The tensile strength and modulus of elasticity of PVOH composites were higher than pure PVOH film and they were increased along with an increment of CNC content. While the elongation at break of PVOH film decreased with the increase of CNC content in PVOH composites. PVOH film with 1 wt% of CNC content showed the best condition as the tensile strength and modulus of elasticity increased when CNC added. At the same time, the elongation at break of PVOH film decreased at 1 wt% content of CNC. For scanning electron microscopy (SEM), pores, rough surface and smooth surface on the PVOH composites were observed from the micrographs. At the same time, the percentage of weight changes on PVOH reinforced CNC was higher than pure PVOH film during water absorption testing. The weight changes increase with the CNC content increase.