Characterization of regenerated cellulose prepared from different pulp grades using a green solvent

Abstract

The cellulosic polysaccharide shows many potential applications due to its abundance, renewability, biodegradability and biocompatibility. Nowadays, the dissolution of this biopolymer via the alkaline based green solvent system has gained much attention in developing cellulose based composites for pharmaceuticals, waste water treatment or packaging applications. In this work, we aim at dissolving different grades of sustainable pulps in an aqueous NaOH/urea/thiourea system, involving the freeze thawing process, followed by re-precipitation with distilled water. This particular dissolving medium is chosen as it is economic and environment-friendly. Optical microscopy is used to study the extent of cellulose solubility in this system. Dissolving grade pulp (D.G.P.), with a degree of polymerization DP = 678.27, exhibits higher solubility after 3 freeze thawing cycles, compared to bleached hardwood pulp (B.G.P., DP = 990.67) and tissue grade pulp (T.G.P., DP = 1356.54). DP is further correlated with the average fibre length of the three samples obtained from a Morfi fibre analyser. Additionally, fibre identification through the microscopic slide staining procedure reveals that the long flexible softwood fibres present in the T.G.P. sample are responsible for its high DP. The solubility percentage calculated for D.G.P., B.G.P. and T.G.P. is 72.90%, 57.2% and 57%, respectively. The flow behaviour of each dissolved cellulosic sample is of Newtonian type at high shear rates, considering the same cellulose concentration at ambient temperature. X-ray diffraction patterns (XRD) and ATR-FTIR spectra indicate that the ordered crystalline structure of the samples is successfully destroyed and converted to cellulose II during the dissolution and regeneration process. Field emission scanning electron microscopy (FE-SEM) reveals porous structures for all samples, created due to phase separation of the cellulose solutions during regeneration with distilled water. Thus, the key finding of the study establishes that the regeneration via the green solvent can produce more amorphous cellulosic materials, which may be a suitable additive for papermaking, due to their enhanced bonding ability with wood fibres.

Superabsorbent cellulose-based hydrogels cross-liked with borax

“…Purified cellulose fibers have distinguished peaks initially located at 3,330 and 3,290 cm -1 , corresponding to OH regions generated by O(3)H–O(5) intramolecular hydrogen bonding 33 – 36 . The typical peaks of cellulose I located at 1,430 cm -1 (symmetric CH 2 bending vibrations), 1,374 cm -1 (C–H deformation), 1,316 cm -1 (CH 2 wagging), 1,160 cm -1 (symmetric ring stretching), 1,060 cm -1 (C–O stretching vibration), and 895 cm -1 (asymmetric out-of-plane ring stretching) were observed from these purified cellulose fibers 35 – 37 . After dissolution in mixed NaOH/urea solvent, the differentiation of these typical peaks was observed in comparison to those of the purified cellulose.…”

“…The crystallinity index of the water hyacinth fibers was 77.1%, and this crystallinity degree was reduced to 71.1% after regeneration with the mixed solvent of NaOH and urea. This reduced crystalline regions could be owing to the combined mechanisms: the disruption of original inter- and intra-molecular interaction of cellulose molecules by NaOH, the reduction of cellulose aggregates in the cellulose-NaOH complex by urea hydrates, and rearrangement of new hydrogen bond between hydroxyl groups of cellulose in the cellulose-NaOH complex 35 , 39 , 50 . A similar reduction in the crystallinity index of regenerated cellulose was reported in comparison with that of original fibers 34 , 35 .…”

“…This reduced crystalline regions could be owing to the combined mechanisms: the disruption of original inter- and intra-molecular interaction of cellulose molecules by NaOH, the reduction of cellulose aggregates in the cellulose-NaOH complex by urea hydrates, and rearrangement of new hydrogen bond between hydroxyl groups of cellulose in the cellulose-NaOH complex 35 , 39 , 50 . A similar reduction in the crystallinity index of regenerated cellulose was reported in comparison with that of original fibers 34 , 35 .

Figure 3 X-ray diffraction (XRD) patterns of purified water hyacinth fibers (F) and cross-linked cellulose hydrogels with various concentrations of borax.

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Improving water desalination: Sustainable grafted cellulose acetate reverse osmosis membrane from Egyptian cotton

“…The absorption intensity of this peak rises in tandem with the degree of substitution. 29 Infrared spectroscopy was utilized to analyze the group frequency and chemical structure of the grafted CA-RO membranes. Figure 3A displays the FTIR spectra of AMPSA, where the transmission band, known as the amide I mode, is evident.…”

Development of eco‐friendly bio‐composite by reinforcing pineapple fruit waste crown fiber to ethylene‐propylene rubber modified polyethylene

“…[ 1–5 ] Many NFs plants such as kenaf, cotton, banana, hemp, coir, jute, palmyra, sisal, talipot bamboo, flax, abaca, and pineapple are available with proficiency for use in industries as raw materials for different purposes. [ 6–10 ] NFs have numerous beneficial dominances over synthetic fiber due to thermal insulation, comparable specific mechanical properties, low density, and low cost. [ 7,11 ] NFs have been used in industrial applications such as paper making, packaging, textile, furniture, and building materials.…”