Mohammad L. Hassan

Thermoplasticization of bagasse. I. Preparation and characterization of esterified bagasse fibers

This research was to investigate the conversion of bagasse into a thermo- formable material through esterification of the fiber matrix. For this purpose, bagasse was esterified in the absence of solvent using succinic anhydride (SA). The reaction parameters of temperature reaction, time, and amount of succinic anhydride added were studied. Ester content, Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA) were used to characterize the chemical and thermal proper- ties of the esterified fibers. The results showed that on reacting bagasse with SA in the absence of solvent, ester content up to about 48% could be obtained. Diester formation increased with increasing reaction time and temperature at high levels of ester content. Ester content determination of the esterified fibers and their corresponding holocellu- loses showed that the reaction took place in the lignin and holocellulose components of bagasse. The IR results showed that the crystallinity index of different esterified bagasse samples did not decrease as a result of increasing the ester content. DSC and TGA results showed that esterified-bagasse fibers were less thermally stable than the untreated fibers, DMTA results showed that esterification of the fibers resulted in a decrease in the tan δ peak temperature of the esterified fibers compared to the un- treated fiber.

Thermoplasticization of bagasse by cyanoethylation

To develop a new technique for the effective utilization of bagasse, cyanoethylation was attempted to see if bagasse could be converted into a thermoplastic material. The effects of various reaction parameters (temperature, time, alkali concentration, and acrylonitrile-to-bagasse ratio) on the extent of the cyanoethylation reaction were studied. Fourier transform infrared spectroscopy was done to demonstrate the occurrence of cyanoethylation; thermogravimetric analysis, to study the thermal stability of the produced cyanoethylated bagasse; X-ray diffraction, to follow the change in the supramolecular structure; and scanning electron microscopy of hot-pressed cyanoethylated bagasse to show the occurrence of thermoplasticization.

Thermoplasticization of bagasse. II. Dimensional stability and mechanical properties of esterified bagasse composite

This research was to investigate the conversion of bagasse into a thermo- moldable material through esterification of the fiber matrix. For this purpose, bagasse fiber was esterified in the absence of solvent using succinic anhydride. The dimensional stability and mechanical properties of composites prepared from the esterified fibers were studied. Dimensional stability was found to be dependent on the total ester and monoester/diester content of esterified fibers and increased with increasing total ester and monoester content of the fibers. The mechanical properties (bending strength, tensile strength, and hardness) were enhanced with increasing monoester contents. Scanning electron microscopy was used to prove the occurrence of thermoplasticization of the esterified fibers.

Use of cellulose and oxidized cellulose nanocrystals from olive stones in chitosan bionanocomposites

Cellulose nanocrystals (CNC) and 2,2,6,6-tetramethyl-1-piperidinyloxyl- (TEMPO-) oxidized cellulose nanocrystals (CNC-TEMPO) were prepared from olive stones. The prepared nanocrystals were characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and carboxylic groups content determination. The prepared nanocrystals were used as reinforcing elements in chitosan nanocomposites, which were characterized using X-ray diffraction (XRD) and tensile strength properties. In addition, the bioactivity of the prepared chitosan nanocomposites was studied in vitro in simulated body fluid (SBF) using scanning electron microscopy (SEM) and electron diffraction X-ray spectroscopy (EDX). The results showed positive effect of the nanocrystals on tensile strength properties of chitosan and noticeable reduction in its rate of dissolution in SBF due to presence of cellulose nanocrystals. Chitosan nanocomposites containing CNC-TEMPO showed higher tensile strength properties and higher rate of dissolution in SBF than those containing cellulose nanocrystals. Nanocomposites containing CNC or CNC-TEMPO could not form significant amounts of hydroxyapatite (HAp) upon immersion in SBF for up to 4 weeks. Upon addition of nanohydroxyapatite to chitosan/cellulose nanocrystals films, formation of new hydroxyapatite depositions was observed. Presence of cellulose nanocrystals in chitosan/HAp resulted in formation and deposition of higher amounts of new HAp than in case of using chitosan/HAp without cellulose nanocrystals.

Novel chitosan-ZnO based nanocomposites as luminescent tags for cellulosic materials

Novel chitosan-ZnO composites have been synthesized as luminescent taggants for cellulosic materials. The synthesized chitosan-ZnO nanospheres (CS-ZnO NS), chitosan-ZnO-oleic acid quantum dots (CS-ZnO-oleic QD) and chitosan-ZnO-oleic acid:Eu(3+) doped nanorods (CS-ZnO-oleic:Eu(3+) NR) were characterized by X-ray diffraction, photoluminescence spectroscopy, FTIR spectroscopy and transmission electron microscopy. The prepared luminescent CS-ZnO composites were used in printing paste and applied to different types of papers and textiles by using screen printing technique. The colorimetric values of the printed CS-ZnO-oleic acid and CS-ZnO-oleic:Eu(3+) showed that printing caused slightly change in color values. Scanning electron microscopy images and color values of the printed surface showed that CS-ZnO-oleic QD and highly luminescence CS-ZnO-olic:Eu(3+) NR are suitable for use as a printed security feature.

Improving cellulose/polypropylene nanocomposites properties with chemical modified bagasse nanofibers and maleated polypropylene

The properties of cellulose/polypropylene (PP) nanocomposites with n-octadecyl-modified bagasse nanofibers (MBNF) were compared to those with maleated polypropylene (MAPP) coupling agent. The nanocomposites were prepared by twin-screw extrusion with bagasse nanofiber (BNF) content varying from 2.5 to 10 wt%. The compression molded nanocomposites sheets were characterized regarding their tensile strength properties, dynamic mechanical thermal properties, crystallinity, water absorption, transparency and loss of strength due to composting in soil. As a compatibilizer to improve the tensile strength properties and transparency of PP/cellulose nanofibers nanocomposites, MAPP was more effective than n-octadecyl-modified cellulose nanofibers. The crystallinity of the nanocomposites was lower than that of neat PP except for those prepared using high loading of MBNF. Dynamic mechanical thermal analysis (DMTA) of the prepared materials showed that adding the different nanofibers (treated or untreated) resulted in better mechanical thermal properties above glass transition temperature (Tg) of PP. Water absorption capability in all nanocomposites was weakened while that in PP/MBNF was the lowest. No significant differences were found between the nanocomposites with different kinds of nanofibers regarding the loss of their tensile strength after compositing in soil up to six months.

New Metallo-Supramolecular Terpyridine-Modified Cellulose Functional Nanomaterials

New metallo-supramolecular nanocellulosic derivatives were prepared by surface modification of cellulose nanocrystals with 4-chloro-2,2′:6′,2″-terpyridine and subsequent coupling with other terpyridine-functionalized derivatives via RuIII/RuII reduction. The terpyridine-modified cellulose nanocrystals (CTP) were characterized using transmission electron microscopy (TEM), magic angle spinning 13C nuclear magnetic resonance (MAS-13C NMR), elemental analysis, as well as Fourier transform infrared (FTIR) and UV-Visible spectroscopy. Metallo-CTP with different optical properties, and expected magnetic and catalytic properties, were easily obtained upon reaction of the prepared CTP with different di- and trivalent transition metal ions (Fe+2, Mn+2, Co+2, and Ru+3). Metallo-supramolecular nanocellulosic derivatives with different properties were prepared by subsequent coupling of RuIII-CTP complex with other terpyridine ligands bearing different functionalities.

Improving tensile strength and moisture barrier properties of gelatin using microfibrillated cellulose

Microfibrillated cellulose isolated from bagasse was used to prepare novel nanocomposites using cross-linked gelatin as a biodegradable polymer matrix. Microfibrillated cellulose loadings up to 25% (weight percent) were used. The prepared nanocomposites were characterized regarding their wet and dry tensile strength, water sorption, and water vapor permeability. Nanocomposites’ surfaces were examined by scanning electron microscopy; the scanning electron microscopy images indicated homogeneous distribution of microfibrillated cellulose in the gelatin matrix. Microfibrillated cellulose improved wet and dry maximum tensile stress and modulus of cross-linked gelatin but resulted in a decrease of its strain at break. Microfibrillated cellulose did not affect the water absorption of cross-linked gelatin but significantly improved its moisture barrier property.

Membranes Based on Cellulose Nanofibers and Activated Carbon for Removal of Escherichia coli Bacteria from Water

Cellulosic nanomaterials are potential candidates in different areas, especially in water treatment. In the current work, palm fruit stalks cellulose nanofibers (CNF), TEMPO-oxidized CNF (OCNF), and activated carbon (AC) were used to make thin film membranes for removal of E. coli bacteria from water. Two types of layered membranes were produced: a single layer setup of crosslinked CNF and a two-layer setup of AC/OCNF (bottom) and crosslinked CNF (up) on hardened filter paper. The prepared membranes were evaluated regarding their microstructure and layers thickness using scanning electron microscopy (SEM). Water flux and rejection of E. coli bacteria was tested using dead end stirred cells at 1 MPa pressure. Thickness of the cosslinked CNF layer in both types of membranes was about 0.75 micron. The results showed that exchanging water by isopropyl alcohol before drying increased porosity of membranes, and thus resulted in increasing pure water flux and flux of bacteria suspension. The two-layer AC/OCNF/CNF membrane had much higher water flux than the single layer CNF due to higher porosity seen on the surface of the former. Both types of membranes showed high capability of removing E. coli bacteria (rejection ~96–99%) with slightly higher efficiency for the AC/OCNF/CNF membrane than CNF membrane. AC/OCNF/CNF membrane also showed resistance against growth of E. coli and S. aureus bacteria on the upper CNF surface while the single layer CNF membrane did not show resistance against growth of the aforementioned bacteria.

Cellulose nanocrystals and carboxymethyl cellulose from olive stones and their use to improve paper sheets properties

Olive stones wastes were used to prepare cellulose nanocrystals (CNC) and carboxymethyl cellulose (CMC). Transmission electron microscopy images showed that the prepared nanocrystals had width and length of about 5–7 nm and 174–234 nm, respectively. Mixtures containing CMC and CNC in water were prepared and the effect of CNC ratio (from 2.5–10 wt.% based on CMC) on viscosity of CMC solution was studied. Films casted from CMC/CNC mixtures were characterised regarding their crystallinity, tensile strength, and dynamic mechanical thermal properties. In addition, the prepared mixtures were used for coating of paper sheets and the effect of coating on mechanical properties (breaking length and tear factor), water absorption, and air permeability of paper sheets was studied. Presence of CNC in the coating mixtures resulted in improving mechanical properties and decreasing water absorption and air permeability of paper sheets as compared to paper sheets coated with neat CMC coating mixture.