S. Sreenivasan

Influence of delignification and alkali treatment on the fine structure of coir fibres (Cocos Nucifera)

The present communication reports the effect of a softening treatment carried out with 18% NaOH on the fine structure and structure-property relations in coir fibres. The effect of successive removal of lignin and hemicelluloses on the fine structure has also been studied. Unlike other cellulosic fibres, alkali treatment failed to produce any increase in fibre elongation in coir. However, the spiral structure was found to be considerably modified by swelling. X-ray and infrared spectral measurements revealed that a part of the noncellulosic components does occupy the intracellular space and plays a significant role on fine structural changes produced during the alkali treatment.

Quantitative Analysis of Crystalline Phases in Chemically Treated Cotton Fibers

This paper deals with the evaluation of crystal lattice transformations and decrys tallization brought about in cotton fibers by chemical treatments, using x-ray diffiaction techniques. Suitable indices have been evolved to quantify cellulose II and total crys tallinity values, and cotton fibers subjected to widely different chemical treatments have been evaluated. The accuracy of the new indices and their usefulness in routine analysis are enumerated.

Crystallization of Amorphous Cellulose

Recrystallization behavior of the hydrolysates of native and thrice mercerized cotton, ball-milled to yield samples of different amorphity, was studied using x-ray diffraction. For crystallization of amorphous cellulose into cellulose I lattice, the presence of cellulose I nuclei seems to be a prerequisite. In a partially ball-milled cellulose I . sample, crystallization into cellulose II does not start until the amorphous content is as high as 75% or more. Results are discussed on the basis of the current ideas of the fine structure of fibers.

Quantitative X-Ray Phase Analysis in Cottons Through Simple Indices

It is well known that crystal-lattice changes and decrystallization can be brought about in cotton cellulose .by using appropriate chemical reagents. 1-ravdiffraction (XRD) methods have been employed by manv workers to monitor such changes, and different procedures have been followed to evaluate parameters like crystallinity, crystal-lattice composition, etc. In the case of the familiar mercerization treatment, easily-measurable indices such as the lattice-conversion ratio (LCR) E4] and the ratio of the heights of the (101 ) and (002) XRD peaks El] have been used to study the fine structure of the samples. In the case of such treatments with reagents like ethylenediamine (EDA) or zinc chloride, which only increase the disorder in cotton and do .not produce new crystal lattices, the changes have been evaluated by indices like the crystallinity index (CI) [3~. Apart from such indices, more &dquo;absolute&dquo; methods E2] have also been developed. However, they are generally a little more dif~cult to use in routine studies. The purpose of th note is 1) to evaluate the utility of LCR in estimating the cellulose II and amorphous contents in samples consisting of these phases of cellulose as’well as the native cellulose I lattice, and 2) to similarly evaluate the utility of CI in estimating the amorphous contents in samples containing only cellulose I and amorphous phases. For the present study, mercerized and EDA-decrystallized samples were prepared as described by Patil el al. [2]. The XRD diagrams were obtained using Ni-filtered Cu K. radiation from a Philips stabilized x-ray generator PW 1130 with diffractometer and recording accessories, and operating in the reflection

Effect of an Alkali Treatment on the Enzymolysis of Never-Dried Cotton Cellulose

The effect of an alkali pretreatment on never-dried fibers prior to enzymolysis has been studied using x-ray diffraction and electron microscope techniques. The reduced susceptibility of the never-dried fibers to enzymolysis after the alkali pretreatment has been traced to the specific morphological state of the fibrils.

Reversals in Cotton: A Study with Scanning Electron Microscopy

The fibrillar morphology of the reversal zones in cotton fibers swollen in aqueous zinc chloride (ZnCl 2) is examined using scanning electron microscopy. There are dis tinct differences in the size of fibrillar aggregates on the two sides of structural reversals in some of the ZnCl2 treated fibers in all four varieties of cotton studied. These dif ferences seems to suggest that fibrils flanking a structural reversal could differ in their fineness levels.

X-Ray Orientation of Equatorial Planes in Swollen and Stretched Cellulosic Fibers

X-ray orientation profiles were recorded that pertained to the three equatorial planes from cotton fibers containing both cellulose I and II lattices and from viscose fibers. The changes in orientation brought about by swelling and stretching treatments could be accurately followed by studying the distribution of any one of the diffraction arcs.

Recrystallization of Cellulose

Hydrolysates of fibers swollen in various intracrystalline swelling agents were ball- milled for separate periods. These samples containing different proportions of cellulose I (C I) Cellulose II (C II) and amorphous (Am) phases were subjected to a mild hy drolysis, and their recrystallization behavior was studied by x-ray diffraction methods. Recrystallization into C I occurs only by nucleation, whereas recrystallization into C II is also caused by accretion of the long disordered molecular segments severed from crystallites.

Birefringence of Stretched Cellulose Films

Birefringence in three orthogonal directions was determined at normal incidence by the compensator method on thin sections of cellophane sheets, before and after subjecting them to swelling and stretching treatments. Considerable increase in crys tallinity and longitudinal orientation of molecular chain axes was achieved by stretch ing. From the course of variation in the three birefringence values with increasing stretch up to 42.5% imparted during treatment, it was possible to ascertain the biaxial orientation of the molecular chains in the crystalline and amorphous celluloses. If the crystallites are oriented with the (101) plane parallel to the film surface, the glucose rings in the amorphous regions align themselves parallel to the film surface. The stacking tendency of crystallites leading to the planar orientation of the (101) planes parallel to the film surface is also evident from crystallite dimension data.

Enhanced enzymolysis of cotton fibres and cotton plant stalks

The results of enzymolysis studies on cotton fibres and cotton plant stalks using Penicillium funiculosum Thom F4are reported. The substrates were used in the never-dried state as well as in the dried condition. In addition, the effect of using substrates which were not dried subsequent to alkali pretreatment and aqueous removal of alkali thereafter was also investigated. Higher saccharification efficiencies were observed when the substrates used were kept in a wet condition prior to reaction with the enzyme. Investigations on the changes in the three-dimensional structural order in the substrates as well as the changes in the degree of polymerization during the course of enzymolysis, were helpful in understanding the differences in the results obtained with the various substrates.