Ahmed Nagaty

Grafting of synthetic polymers to natural polymers by chemical processes

Greffage de monomeres sur la cellulose et la lignocellulose. Preuve du greffage. Methodes de polymerisation radicalaire. Greffage par addition et condensation. Copolymerisation greffee ionique. References

Chemical and Spectral Studies on Hemicelluloses Isolated from Bagasse

Hemicelluloses were extracted from bagasse at room temperature with potassium hydroxide. After hydrolyzed with IN HC1 the extract contains a high percentage of monomeric sugars. Significantly lower amounts of monomeric sugars were identified in the extract of black liquor when treated by acetic acid (first fraction). This finding may be due to the degradation of sugars at the high temperature during the pulping process. Only a small second fraction of hemicelluloses obtained from black liquor by dilution with alcohol was found to be less degradated, probably due to difference in the structure. Hemicelluloses of bagasse showed similarity in sugar contents; the difference was only in the molar ratios of the sugars. Paper Chromatographie analysis showed that xylose äs expected predominates, followed by arabinose and then ribose. Fructose and galactose were in traces. IR spectra revealed that hemicelluloses were obtained in three forms: Free from lignin, combined with lignin and in mixture with it. Differences still exist in the IR spectra of the hemicelluloses relating to each form. Hemicelluloses, free, combined and mixed showed differences towards their solubilities in organic solvents.

Structure of Alkali Lignins Fractionated from Ricinus communis and Bagasse. 3. IR Spectra

Abstract The lignin fractions isolated by one- and multistage soda and sulfate cookings showed almost identical IR spectra, indicating the similarity of the lignin skeletal structure throughout the plant. However, the absorbances reveal some differences. Similarity of the spectra includes: 1) chelation and bonding of the hydroxyl groups. 2) Stretching vibration of C-H bonds in methyl, methoxyl, and methylene groups. 3) Stretching vibration of C[tbnd]N. 4) Carbonyl unconjugated β-ketone, conjugated acids, or esters at 1725 cm−1. There is no change in the intensity of absorption at this band from that at 1515 cm−1 with the cooking stage. 5) Aromatic skeletal vibration at 1610 and 1515 cm−1, affected by ring substituents at 1425 cm−1. 6) The band at 1465 cm−1 showed a higher intensity for soda and soluble kraft lignins than for insoluble kraft ones. 7) The band at 1370 cm−1, assigned to phenolic OH bending, is affected by the methoxyl group. 8) The absence of condensed guaiacyl and the presence of syringyl a...

Structure of Alkali Lignins Fractionated from Ricinus communis and Bagasse. 1. Chemical Constituents

Abstract Fractionation of alkali lignins of the soda and sulfate pulping processes of Ricinus communis and bagasse was carried out by using successive equal concentrations of the alkaline reagent. Soda lignins were soluble in organic solvents, while the sulfate ones were sparingly soluble. Thus, two fractions of the sulfate lignins, soluble and insoluble, could be obtained from acetone. The different alkali lignin fractions were subjected to elemental and functional group analyses. For both Ricinus communis and bagasse, the carbon content of the fractions of the various types of lignin is in the order: soluble sulfate > soda > insoluble sulfate, while the methoxy is in the order: soda > soluble sulfate > insoluble sulfate. The phenolic OH content, as well as OH/C9 of soda lignins of bagasse, are lower than those of soluble sulfate lignins. For Ricinus communis, the phenolic OH content and OH/C9 is higher for some of the fractions (first three stages of cooking) of soda lignin than the corresponding fracti...

Carboxymethylation of Cellulose Acetate

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Lignocellulose polymer composites as γ-dosimeter in the kilorad range

Abstract The induced changes in the electrical resistance by γ-irradiation was measured for some cellulose-polymer composites. Increasing the percentage of the polymer in the composite samples results in an increase of the activation energy. When the polymer is replaced by another, the activation energy changes accordingly. The addition of glass to the composite gives rise to lower activation energy. Still further decrease is achieved if glass is replaced by cupric oxide. The results obtained show that the resistance was changed to a lower value by γ-irradiation. This may allow such composites be used as γ-dosimeters in the kilorad range.

Structure of alkali lignins fractionated from Ricinus Communis and bagasse. 2. Alkaline nitrobenzene oxidation

Abstract Alkaline nitrobenzene oxidation of the different lignin fractions isolated from Ricinus communis and bagasse yielded mainly vanillin, followed by syringaldehyde and then p-hydroxybenzaldehyde. The number of the guaiacyl units is higher than the sum of both syringyl and p-hydroxyphenyl propane units in soda lignins and acetone-soluble sulfate lignins for both Ricinus communis and bagasse. For acetone-insoluble sulfate lignins, the number of guaiacyl units is less or equal to the sum of both syringyl and p-hydroxyphenyl propane units for both Ricinus communis and bagasse.