Ahmed A. Oun

Preparation and characterization of sodium carboxymethyl cellulose/cotton linter cellulose nanofibril composite films

Crystalline cellulose nanofibril (CNF) was isolated from cotton linter pulp using an acid hydrolysis method and used as a filler to reinforce sodium carboxymethyl cellulose (CMC) film. The CNF was in rod shape with the diameter of 23-38 nm and the length of 125-217 nm and crystallinity index (CI) was 0.89. The effect of CNF concentration (1, 3, 5, and 10 wt% based on CMC) on the optical, morphological, mechanical, water vapor barrier, surface hydrophobicity, and thermal properties of the nanocomposites were studied. The CNF was evenly distributed in the polymer matrix to form smooth and flexible films indicating the CNF is highly compatible with the CMC. The tensile strength (TS) and elastic modulus (EM) of CMC film increased by 23% and 27%, respectively, while the elongation (E) decreased by 28% with 5 wt% of CNF inclusion. The WVP of CMC film decreased at low content of CNF, and increased with increase in CNF content, then decreased but to the same level of the control CMC film with the inclusion of 10 wt% of CNF. Transparency of CMC film decreased slightly from 87.7% to 86.2% with 5 wt% of CNF. The CMC/CNF composite films have a high potential to be used as an edible coating or packaging films for the extension of shelf life of fresh and minimally processed fruits and vegetables.

Effect of post-treatments and concentration of cotton linter cellulose nanocrystals on the properties of agar-based nanocomposite films.

Cellulose nanocrystals (CNCs) were prepared by acid hydrolysis of cotton linter pulp fibers and three different purification methods, i.e., without post purification (CNC1), dialyzed against distilled water (CNC2), and neutralized with NaOH (CNC3), and their effect on film properties was evaluated by preparation of agar/CNCs composite films. All the CNCs were rod in shape with diameter of 15-50 nm and length of 210-480 nm. FTIR result indicated that there was no distinctive differences in the chemical structure between CNCs and cotton linter cellulose fiber. No significant relationship was observed between the sulfate content and crystallinity index of CNCs. The CNC3 showed higher thermal stability than the other type of CNCs due to the less adverse effect on the thermal stability of sulfate groups induced by the neutralization with NaOH. The tensile strength (TS) of agar film increased by 15% with incorporation of 5 wt% of CNC3, on the contrary, it decreased by 10% and 15% with incorporation of CNC1 and CNC2, respectively. Other performance properties of agar/CNCs composite films such as optical and water vapor barrier properties showed that the CNC3 was more effective filler than the other CNCs. In the range of concentration of CNC3 tested (1-10 wt%), inclusion of 5 wt% of CNC3 was the maximum concentration for improving or maintaining film properties of the composite films. The neutralization of acid hydrolyzed cellulose using NaOH was simple and convenient for the preparation of CNC and bionanocomposite films.

Isolation of cellulose nanocrystals from grain straws and their use for the preparation of carboxymethyl cellulose-based nanocomposite films

Cellulose nanocrystals (CNCs) were isolated from rice straw (RS), wheat straw (WS), and barley straw (BS) by using acid hydrolysis method. They were fibrous in shape with length (L) of 120-800nm and width (W) of 10-25nm, aspect ratio (L/W) of 18, 16 and 19, crystallinity index (CI) of 0.663, 0.710, and 0.634, and yield of 64, 75, and 69wt% for RS, WS, and BS respectively. Carboxymethyl cellulose (CMC)/CNC composite films were prepared with various concentration of the CNCs. SEM results showed that the CNCs were evenly distributed in the polymer to form homogeneous films. Mechanical and water vapor barrier properties were varied depending on the type of CNCs and their concentration. Tensile strength (TS) increased by 45.7%, 25.2%, and 42.6%, and the water vapor permeability (WVP) decreased by 26.3%, 19.1%, and 20.4% after forming composite with 5wt% of CNCs obtained from RS, WS, and BS, respectively.

Preparation of antimicrobial hybrid nano-materials using regenerated cellulose and metallic nanoparticles

In this study, antimicrobial hybrid nano-materials were prepared by one-pot syntheses of silver (Ag), copper oxide (CuO), or zinc oxide (ZnO) nanoparticles (NPs) during regeneration of cellulose from cotton linter (CL) and microcrystalline cellulose (MCC). SEM micrographs indicated that the metallic nanoparticles were attached to the surface of the regenerated cellulose. EDX and ICP results showed that more AgNPs were adsorbed on the cellulose than CuONPs or ZnONPs. FTIR results revealed that the metallic nanoparticles were attached to the cellulose through the interaction with the hydroxyl group of cellulose. XRD results showed the characteristic diffraction peaks of individual metallic nanoparticles. The thermal stability of the R-CL and R-MCC increased in the hybrids with AgNPs and ZnONPs. The R-cellulose/metallic NPs hybrids showed strong antibacterial activity against E. coli and L. monocytogenes. Thus, the hybrid nano-materials can be used as nanofillers for the preparation of antibacterial packaging films.

Preparation of multifunctional chitin nanowhiskers/ZnO-Ag NPs and their effect on the properties of carboxymethyl cellulose-based nanocomposite film

Chitin nanowhiskers (ChNW) were isolated and used for the synthesis of hybrid ChNW/ZnO-Ag NPs. The hybrid nanoparticles were used for the preparation of multifunctional carboxymethyl cellulose (CMC) films. A ChNW was needle shape with the width of 8-40nm, the length of 150-260nm, and crystallinity index of 93.6%. The ZnO-Ag NPs were spherical with the diameter of 10.5-16.2nm. STEM, EDX, XRD, and UV-vis analyses confirmed the formation of ZnO-Ag NPs on the surface of ChNW. The thermal stability of ChNW was increased by incorporation of ZnO-Ag NPs. A CMC-based nanocomposite film incorporated with 5wt% of ChNW/ZnO-Ag NPs was homogeneous and showed the high UV-barrier property. The tensile strength (TS) and elastic modulus (E) of the composite film increased by 18-32% and 55-100%, respectively, while the elongation at break (EB) decreased by 23-33%. CMC composite films showed strong antibacterial activity against E. coli and L. monocytogenes.

Characterization of carboxymethyl cellulose-based nanocomposite films reinforced with oxidized nanocellulose isolated using ammonium persulfate method

Cellulose nanocrystals (CNCs) were isolated from cotton linter (CL) and microcrystalline cellulose (MCC) using an ammonium persulfate (APS) method for a simultaneous isolation and oxidation of CNCs. The CNCs were in rod-like shape with a diameter of 10.3nm and 11.4nm, a length of 120-150nm and 103-337nm, a crystallinity index of 93.5% and 79.1% for the CNCCL and CNCMCC, respectively. The suspensions of oxidized CNCs were transparent and stable with the zeta potential values of -50.6mV and -46.9mV. The CNCs were uniformly distributed within the carboxymethyl cellulose (CMC) polymer matrix. The tensile strength (TS) increased by 102% and 73%, and elastic modulus (E) increased by 228% and 166% with the incorporation of at 10wt% of CNCCL and CNCMCC, respectively. Conclusively, the CNCCL showed a more uniform particle size distribution, higher crystallinity, transparency, thermal stability, and superior mechanical strength compared with the CNCMCC.

Effect of oxidized chitin nanocrystals isolated by ammonium persulfate method on the properties of carboxymethyl cellulose-based films

Oxidized chitin nanocrystals (ChNCs) were isolated from crab shell chitin using ammonium persulfate (APS) method. The oxidized ChNCs were in needle shape with a diameter of 15nm, the length of 400-500nm, and crystallinity index of 93.5%. Carboxymethyl cellulose (CMC)-based films reinforced with the ChNCs (0, 1, 5, and 10wt.%) were flexible and transparent. The mechanical strength of the CMC film increased significantly (p<0.05) after blending with the ChNCs. The tensile strength (TS) and elastic modulus (EM) increased by 88% and 243% when 10wt.% of ChNCs were incorporated. Water vapor barrier property of the composite films decreased and the hydrophilicity increased compared with the neat CMC film. The oxidized ChNCs obtained using the APS method have a high potential for being used as a reinforcing filler to improve the mechanical properties of nanocomposite films for the application in food packaging, nano-papers, hydrogels as well as biomedical applications.

Effect of isolation methods of chitin nanocrystals on the properties of chitin-silver hybrid nanoparticles

Chitin nanocrystal (ChNC) was isolated using sulfuric acid hydrolysis (ChNCH2SO4), TEMPO-oxidation (ChNCTEMPO), and ammonium persulfate (ChNCAPS) methods, and used for the preparation of hybrid nanoparticles of ChNC/silver nanoparticles (AgNP). The ChNC exhibited a needle-shaped structure with a sulfate group content of 135 μmol/g for ChNCH2SO4 and carboxyl content of 0.71 and 1.42 mmol/g for ChNCTEMPO and ChNCAPS, respectively. ChNC worked as a reducing and stabilizing agent for the production of AgNP and reduced the size of AgNP from 23.9 nm to 6.3 nm in the ChNC/AgNP hybrid. The carboxyl content of ChNC played a significant role for the nucleation, size distribution, and antibacterial activity of ChNC/AgNP. ChNC/AgNP hybrid, especially ChNCAPS/AgNP, exhibited strong antibacterial activity against food-borne pathogenic Gram-negative (E. coli) and Gram-positive (L. monocytogenes) bacteria. The prepared ChNC/AgNP hybrid nanomaterials have a high potential for the application to be used as a nanofiller to improve the properties of food packaging materials to extend the shelf-life of packaged food.