Characterization of polylactic acid polymer reinforced with microcrystalline cellulose composites extracted from paper sludge by tetrakis ionic liquid / Siti Nuramirah Rabbani Muhammad Zaki

The large amount of paper sludge generated from wastepaper industries emphasizes the importance of developing green waste management solutions. Tremendous researchers have reported cellulose extraction from sludge in various sources, such as municipal sludge, domestic sludge, palm oil wastewater, and paper wastewater. This study aimed to isolate microcrystalline cellulose (MCC) from paper sludge using tetrakis (hydroxymethyl) phosphonium chloride ionic liquid combined with (0.1, 1.0, 2.0, 3.0, 4.0 M) hydrochloric acid. The effect of the acid concentrations was characterized using FTIR, SEM, XRD, TGA, and UV-Vis. The disappearance of peaks at 1425 cm-1, 1176 cm-1, and 868 cm-1 in the (FTIR) spectroscopy were related to removing the non-cellulose component, while peaks at 1453 cm-1, 1380 cm-1, and 895 cm-1 indicated the presence of cellulose. Scanning electron microscope micrograph confirmed that the diameter of MCC was smaller with the increasing acid concentration, where 3.0 M shows the average minor diameter of 29.73 μm. Thermogravimetric analysis showed 3.0 M HCl MCC started to decompose at 268 °C with a maximum temperature of 288 °C. 3.0 M reflected UV-B at 28 % and UV-A at 39 % due to the high crystallinity index (CrI) of 31 %. Results showed that 3.0 M HCl concentration had optimum properties, and further, this concentration was used for composite fabrication. The solvent casting technique was used for composite fabrication. The fiber loadings were varied from (1 wt. %, 2 wt. %, 3 wt. %) and the effect of fiber loading on the properties of the composite was assessed through analysis including (TGA, DSC, FTIR, XRD, FESEM, and UV-Vis). The maximum degradation temperatures of 1 wt. % PLA/MCC was 328 °C with glass transition temperature (Tg) of 82 °C and crystallization temperature (Tc) of 169 °C. 1 wt. % PLA/MCC displayed small domains with typical sea-island morphology and homogeneously dispersed filler, indicating excellent dispersion in composites. UV-A and UV-B transmittance were observed at the lowest transmittance without sacrificing transparency at 29 % and 26 %, respectively. SEM and XRD investigations revealed reduced agglomeration with a higher crystallinity index of 26 % in 1 wt. % PLA/MCC composite film. The novelty of this work is the possible extraction of microcrystalline cellulose from paper sludge using tetrakis (hydroxymethyl) phosphonium chloride ionic liquid to reinforce polylactic acid in film packaging. The findings conclude that the best conditions for cellulose extraction were 80 °C and a ratio of 1:10 ionic liquid, 3.0 M HCl is the optimum concentration for extracting MCC, while 1 wt. % MCC is the optimum fiber loading to enhance interfacial adhesion, promote MCC dispersion in the polymer matrix, improve stress transfer, and avoid filler aggregation.