Influence of green extraction process of nano fibrillated cellulose using subcritical water/CO₂ on its properties and development of its bio composite

Abstract

The study proposes a new green extraction method of producing nano fibrillated cellulose (NFC) from softwood pulp (SWP) by using subcritical water/CO 2 . Subcritical water/CO 2 led to a controlled hydrolysis of SWP and the treated SWP was fibrillated by sonication to produce NFC. Effect of process parameters (time, temperature, and pressure) on the crystallinity and thermal properties of NFC was studied to optimize the process conditions for controlled hydrolysis. The influence of the extraction process on the properties of prepared NFC was studied. Nanocellulosic materials were characterized by using field emission scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, wide-angle X-ray diffraction, and thermo gravimetric analysis. The NFC obtained at optimum process conditions (100 bar, 145 C, and 30 min) showed significantly high crystallinity (66%) and high yield (75-80%) compared to the NFC prepared by conventional mechanical grinding method. The present method of producing NFC uses water and pressurized CO 2, and therefore, eliminate use of acids and chemicals. Plasticized poly vinyl alcohol (p-PVA) based nano composite with NFC shows significant improvement in thermal stability (36%), tensile strength (77%) with reduced water vapor transmission rate as compared to virgin p-PVA indicating their potential as nanofiller for making bio composites.

Nano fibrillated cellulose‐based foam by Pickering emulsion: Preparation, characterizations, and application as dye adsorbent

“…In case of CMMC-NFC also with increasing concentration, compression strength was found to be increased and maximum obtained value was 0.14 MPa which is inferior than CMSC-NFC one, probably caused by higher crystallinity of the later. [33] Overall, it can be stated that the properties of dry foams obtained F I G U R E 8 Density of foams with increasing concentrations of CMSC-NFCs F I G U R E 9 (A) Compression strength and (B) typical stress strain curves for foams prepared with increasing concentrations of CMSC-NFCs using SC-NFC, were observed to be superior to the conventionally prepared one.…”

“…SC-NFC was prepared by using subcritical water/CO 2 treatment followed by sonication as per our previous reports. [33,34] The subcritical water/CO 2 treatment of SWP was done in 2 L nonstirrer type high pressure autoclave manufactured by Nano-Mag Technologies, Mumbai, India. One gram of SWP along with 40 ml of de ionised (DI) water was taken in a 50 ml beaker and kept inside the autoclave.…”

“…Then suspended SWPs were fibrillated for 6 h by passing through 180 clearance gauge of super masscolloider, at a speed of 1500 rpm. [33] 2.3 | Carboxymethylation of SC-NFC SC-NFC was modified by partial carboxymethylation as per the literature. [36] The SC-NFCs were dispersed in water by using laboratory stirrer.…”

“…3.2 | Characterizations of nanocellulose and the foam prepared using the same SC-NFC used for this particular study was prepared using subcritical water and carbon dioxide under high pressure and the details about their preparation, process parameters optimization, yield calculation, morphological and thermal characterizations and crystallinity study, and so forth were reported in our previous study. [33,34] Figure 2A,B shows the TEM micrographs of MC-NFC and SC-NFC, respectively. The average diameter of SC-NFC is 30 ± 10 nm whereas the same is 20 ± 10 nm for MC-NFC.…”

“…[32] To avoid lengthy processing time and reduction in crystallinity, in our previous work we have reported a green extraction method of NFC preparation from softwood pulp (SWP) by exploiting subcritical water and CO 2 followed by sonication. [33,34] In this current work, the same methodology was adopted to prepare NFC (referred as SC-NFC) which was further modified by carboxymethylation to help their dispersion in water. The carboxymethylated SC-NFCs (CMSC-NFCs) were then coated with octyl amine to introduce partial hydrophobicity in them and finally employed as Pickering emulsion stabilizer to produce aqueous foam which underwent freeze-drying to yield porous materials.…”