AbstractsChemistry

Interpretation of numerous X-ray studies has shown that cellulose consists of crystalline regions embedded in a matrix of more randomly distributed amorphous material. Since both the proportions and the detailed structure of these regions have great influence on physical properties, auch as tenacity and flexibility, the adsorption of liquids and gases and on the ability of the fibers to swell in liquids, their measurement is of considerable interest. A chemical analogy of the strictly physical definition, divides the fiber into accessible and inaccessible regions, the accessible portion being defined as that into which the reagent can penetrate. Since the amount of accessible material may be inereased by swelling or decreased by crystallization depending on the nature of the reaction, the estimates from various reactions usually differ. Nor will the amorphous region necessarily coincide with the accessible, the one being arrived at by a truly physical measurement, the other resulting from the imposition of a chemical reaction upon an already complex physical system. This concept of accessibility, however, continues to arouse wide interest since the processing of cellulosic materials, of major importance to most countries, necessarily depends upon the chemical behavior of the fibers, rather than on their ultimate x-ray pattern. [...]