Palm leaves as a woody lignocellulose, together with polystyrene, were used to produce composites. Chemithermal mechanical pulps (CTMP) were obtained from palm leaves under alkaline or acidic conditions. Appropriate bending strength was obtained from palm leaves and their CTMP pulps prepared under neutral or acidic conditions. The bulky fibers resulted from the alkaline pulps lead to composites of low bending strength. Thus, the cooking conditions of the palm leaves to obtain CTMP pulp play an important role on the properties of the composites. The nonbulky fibers lead to the formation of trapped pockets air as the number of the hydrogen bond are few. The presence of these air pockets allows the polystyrene solution to enter forming bonding between the interfaces. It is also found that the lower the density of the composites, the lower the internal bond strengths. The chemical constituents of the CTMP pulps, as well as the yields of the pulps, may influence the properties of the composites. Increasing the percentage of polystyrene in the composites, the mechanical properties increased. The water uptake and the swellability decreased until 20% polystyrene concentration and then levelled off. The thickness and density behaved the same. However, the type of substrate of the composite and the weight fraction are the important factors in determining the properties of the composites.

SYNOPSISSolubility of methyl cellulose (MC) depends on the degree of substitution (DS), the average degree of polymerization ( D P ) , and the distribution of methoxyl groups. Of these, the DS appears to be the most important. The DS of the MC depends on the conditions of preparation. The conditions studied in this work revealed that the DS of the MC increased as the concentration of sodium hydroxide increased from 10 to 50%. This result is attributed to the increase in the extent of formation of alkali cellulose I1 as a result of the increase in the alkali concentration and hence the increase of the DS of the MC. Decreasing both the ratio of dimethyl sulfate : cellulose and the liquor ratio increased the DS. High DS was achieved within a period of 2 and 3 h. However, the DS increased as the time increased. The decrease of the DS as the liquor ratio increased may be attributed to the sol-gel transition due to the interaction of the hydrophobic methoxyl groups within the polymer chains. To reveal the effect of the thermal sol-gel transition, the reaction was carried out in nonaqueous medium and the results obtained showed an increase of the DS with the increase of the solvent ratio until a maximum. This result may be contributed to the breakdown of the hydrogen bonding in the presence of solvents that transfer the reaction medium to the sol-form and hence more methylating reaction takes place. The degree of the solvation of the methyl groups into the solvents also plays a role.

SYNOPSISTreatment of cellulose by different concentrations of alkali, namely, 5-30% NaOH, changed its fine structure and transferred cellulose I into cellulose 11. The decreased crystallinity due to alkali treatment and the transformation of cellulose I into cellulose I1 lowered the reactivity of cellulose toward the grafting polymerization reactions. Compactness of the structure as a result of the treatment of cellulose with 5% sodium hydroxide concentration decreased the rate of the grafting reaction and the grafting yield. On the other hand, such treatment of cellulose with different concentrations of alkali increased the rate of ceric consumption, i.e., increased the rate of oxidation of cellulose. Thus, the termination reaction of the grafting polymerization process may occur as a result of such oxidation and because of the increase of the active sites onto cellulose, leading to a decrease of the grafting yields and rate of grafting polymerization reaction by using the free-radical grafting process. The use of the ionic-xanthate method of grafting polyvinyl-and polyallyl-on alkali-treated cellulose shows an increase of grafting efficiency and grafting yields. Maximum grafting efficiency and yields were achieved when cellulose was treated with sodium hydroxide concentration below 15%, and maximum crystallinity indices were obtained. Using 15-25% sodium hydroxide lowered the indices of crystallinity, and lower grafting yields and grafting efficiency were achieved. Thus, transformation of cellulose I into cellulose I1 decreased the reactivity of these treated celluloses toward graft polymerization reactions by the use of the ionic-xanthate method. In our opinion, termination reactions may also occur and affect the results.

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Sodium bisulfite–soda lime glass has proved to be a good initiator for polymerization and graft polymerization onto cellulose of some vinyl monomers. A scheme dealing with the mechanism of initiation has been proposed assuming trapping of the bisulfite radical inside the glass frame‐work to form a so‐called sulfur‐impregnated solid. Such a solid has paramagnetic properties and acts on the vinyl monomers and cellulose as any free‐radical‐producing source thus leading to polymerization and graft polymerization onto cellulose. Other radicals containing sulfur, such as sulfite, sulfate, and persulfate failed to give such property with soda lime glass. With the sodium bisulfite–soda lime glass system the reactivity decreases in the order methyl methacrylate > ethyl acrylate > acrylonitrile which is inconsistent with the arrangement of acceptor monomers with decreasing electron‐donating ability. This may reflect interference of the addition reaction which may take place between the monomer and bisulfite and the rate of which may depend on the activation energy of the monomer.