The degrees of salt sorption were determined in lyocell and viscose fibers immersed in aqueous solutions of salt-alkali mixtures with the aim of using salt sorption as an indirect measure of changes to fiber accessibility in presence of alkali. The salt-alkali mixtures used were combinations of NaOH with NaCl or NaBr, and of KOH with KCl or KBr. In general, salt sorption in fibers increased with increase in alkali concentration up to 2 mol/l, and did not change significantly thereafter. The accessibility of Br ) salts was greater than the Cl ) salts, but that of the Na + salts was greater than the K + salts. These trends in salt sorption indicate that salt accessibility in fibers is not influenced by the size of hydrated salt ions, but by the forces of electrostatic attraction and repulsion between the charged fiber surface and salt cations and anions.Nomenclature: [X] f -Alkali or salt sorbed by fiber (mol/g Fiber); [X] s -Alkali or salt content in treatment liquor (mol/l); [Y] f -Alkali or salt desorbed by fiber (mol/g fiber); [Y] s -Alkali or salt content in wash liquor (mol/l); CLY -Lyocell fibers without spin finish; CLY-sp -Lyocell fibers with spin finish CV -Viscose fibers; MC -Fractional moisture content of fibers; SRV -Solution retention value of fiber (ml/g); V -Volume of wash liquor (ml); W C -Weight of conditioned fibers; W D -Weight of dry fibers (g) W S -Weight of oven-dried fibers (g); W W -Weight of wet fibers (g); q -Density of treatment solution (g/ml)

Summary: Of prime importance in reactions involving insoluble cellulosic fibers is the sorption of reagents, which is governed by their degrees of accessibility in substrates. Swelling treatments of cellulosics in alkali solutions alter substrate accessibility leading to changes in their reactivity. In this paper, the first of a two-part series, we collate and examine the results from various studies involving different techniques to characterize modifications in cellulosic fibers after swelling treatments in alkali solutions. Results from measurements of structure and accessibility in fibers with techniques such as water retention, inverse size exclusion chromatography (ISEC), iodine sorption, fiber diameters, and fiber-splitting propensities indicate that the influence of swelling treatments on fiber structure/accessibility is differs with alkali type. The results show that a non-uniform rather than uniform distribution of reagents within structures is a more accurate representation of reactions involving swollen cellulosic fibers. Hence, the observed changes in cellulose-fiber reactivity are governed by the degrees of fiber swelling, and reagent sorption and accessibility during swelling treatments.

Streaming potential measurements were conducted on lyocell and viscose fibers, to determine the relative order in sorption extents of salt cations and anions. The sorption of K ? was greater than Na ? ions, and the sorption extents of the anions, Cland Br-, were similar. Previously, we had examined accessibility of the same ions in the fibers, and found them to follow the order: K ? \ Na ? and Cl-\ Br-. From these two contrasting results, we find that the mode of salt interaction with cellulose, from aqueous solutions, changes with the salt concentration. At low concentrations, the interaction is governed by ion-exchange processes with the cellulose carboxyl groups and the Donnan equilibrium; but at higher concentrations, the interaction is a function of the mobility (or diffusivity) of the ions. Thus, sorption and accessibility of cellulose fibers as measured with salts may not apply for other solutes, and conversely, similar studies with other probe molecules may not be relevant for salts.

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Molasses is an inexpensive byproduct made during the extraction of sugars from sugarcane. Viscous molasses was converted to powder form under heating process. Molasses black (MB), mainly consisting of carbon, was finally obtained. As a result of elemental analyzer, it is evident that MB containing 56.13 % of carbon. Additionally, Fourier Transform Infrared Spectrophotometer (FTIR) result confirmed that function groups of MB were comparable with carbon black (CB). Nevertheless, the large particle size and low specific surface area of MB was less effective for reinforcement. Therefore, in this research, a feasibility study was carried out on the utilization of MB together with carbon black as hybrid filler in natural rubber (NR). Reinforcement of NR with MB/CB hybrid filler at various ratios was studied. The total hybrid filler content was 30 parts per hundred of rubber (phr). The mechanical properties were determined. The results revealed that the NR vulcanizates containing hybrid filler exhibited the better reinforcement than that filled with single MB filler.