Isolation and characterisation of nanofibrillated cellulose from waste cotton: effects on thermo-mechanical properties of polylactic acid/MA-g-SEBS blends

Abstract

In garment industry, cotton waste is the major threat for disposal or waste management due to environmental issues. Nanofibrillated cellulose (NFC) from waste cotton was isolated by steam explosion technique, an eco-friendly method in comparison with chemical methods. Nanocellulose was characterised by different analysis techniques like TEM, SEM and XRD. The crystallinity index of nanocellulose was found to be 66% based on Seigel’s empirical method. SEM micrographs showed highly entangled nanofibrils with diameters ranging from 67 to 70 nm. TEM results revealed reduction in the size of fiber from micro to nano upon mild acid treatment along with steam explosion. Bionanocomposites of maleated styrene ethylene butylene styrene (MA-g-SEBS) toughened polylactic acid (PLA) reinforced with nanocellulose were fabricated by twin screw extruder and tested for thermo-mechanical behaviour using injection molded specimen. Mechanical property evaluation showed that the composites containing nanocellulose exhibited higher modulus compared to virgin PLA and PLA binary blend system containing SEBS or MA-g-SEBS. The elongations of bionanocomposites were substantially increased, possibly due to good dispersion of nanocellulose and its plasticizing effect. Morphological studies were also carried out to investigate the effect of nanocellulose on toughened PLA. The impact strength was also found to be higher compared to virgin PLA by the incorporation of nanocellulose to SEBS toughened PLA. Differential scanning calorimetry measurements observed an increase in crystallization of PLA by heterogeneous nucleation effect of NFC.