Renewable starch/polyvinyl alcohol nanocomposite foams reinforced by cellulose nanofibers isolated from carrot residues using a chemo-mechanical process

In this work, cellulose nanofibers (CNFs) were isolated from carrot residues utilizing chemo-mechanical treatments and then were characterized by different chemical and morphological analyses. High-performance liquid chromatography and Fourier-transform infrared spectroscopy revealed a high efficiency of the treatments for the removal of the non-cellulosic components of the nanofibers. An average diameter of 33.2 nm was recorded for the isolated nanofibers using field emission scanning electron microscopy (FESEM). A fibrillation yield of 68.8% was obtained, suggesting that the CNF isolation method was sufficiently efficient. The isolated CNFs were then added to starch/polyvinyl alcohol (St/PVA) blends to prepare nanocomposite foams. The physical, morphological, and thermal properties and moisture absorption of the foams were investigated to study the effects of different concentrations of PVA and CNFs in St/PVA and St/PVA/CNFs foams, respectively. Among the blend foams, St/PVA15 (15 wt% of PVA) exhibited the lowest density and moisture absorption and the highest compressive strength. The addition of low concentrations of CNFs to St/PVA15 foam further lowered the density and enhanced the moisture resistivity and compressive strength. A more homogeneous morphology, increased cell density, and enhanced thermal stability were observed for the blended nanocomposite foam with the optimum content of CNFs (i.e., 3 wt%) compared to those of St/PVA15. Hence, sustainable foams were prepared with desirable properties for potential applications in the packaging industry and disposable and agricultural products.