Homogenous and transparent nanocellulosic films from carrot

Abstract

Nano fibrillated cellulose (NFC) and nanocrystalline cellulose (NCC) have been extracted from carrot pulp by using non-conventional ball milling and acid hydrolysis process respectively. Initially, hot water washed carrot raw fibers treated with hydrogen peroxide, yielded the cellulose rich fibers in the absence of β-carotene and lignin. The scanning electron microscopy (SEM) of raw and bleached fibers showed that carrot consisting of both classical and unusual spring shaped fibers. The ensued purified fibers were fibrillated by ball milling process at three different grinding time to obtain NFC. The consequence of grinding time on fibrillation and morphology of the resulted NFC was investigated by SEM. In parallel, alkali treated pure carrot fibers were used to extract the NCC by acid hydrolysis process. The structural, functional, crystalline and thermal properties of resulted NFC and NCC was characterized by means of transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The length and the diameter of the NCC prepared from carrot was in the range of 54–610 nm. Significant improvement in crystallinity was observed for 5NFC (69%) and NCC (78%) compared to that of raw fibers (36%). The obtained NFC and NCC suspensions were separately cast into nanocellulosic films (NCF). The optical and morphological properties of the resulted films were analysed systematically by ultraviolet–visible spectrophotometry (UV–vis) and SEM respectively. NCF exhibited the significant improvement in the transparency and homogeneity with increase in the grinding time. Furthermore, the mechanical properties of the carrot NCF were studied by using the tensile test.