Date of Award

1998

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

First Advisor

John R. Collier

Abstract

Utilization of agricultural crops as alternate raw materials for many industries was investigated for both sugar cane and kenaf. Value-added products with textile and geotextile applicabilities were developed and their properties assessed in direct correlation with their final use. Bundles of fibers were extracted from the rind of sugar cane in three distinct steps: mechanical separation (using a Tilby separator), chemical extraction, and steam explosion. The process of fiber extraction was optimized for an atmospheric pressure alkali delignification, taking into account different factors such as: alkali concentration, reaction time, mixing, and steam explosion. Statistical techniques were used to study the effect of different process variables on the final characteristics of the fiber bundles. The same process was adapted for different types of kenaf. The kenaf rind containing the outer bast fibers was separated from the inner core material, and the separated rind was submitted to a hot alkali partial delignification followed by steam explosion. The length and fineness of the fibers obtained were relatively sensitive to the sodium hydroxide concentration, but were influenced by the presence of steam explosion. The differences in kenaf harvesting, processing, and storage affected the final physical characteristics of the fiber bundles. Lyocell solutions of sugar cane, kenaf, recycled cotton, and dissolving pulp in N-methyl morpholine-oxide (NMMO) were obtained at moderate temperature (80-95$\sp\circ$C). Rheological behavior of these lyocell solutions was studied in both shear and elongational flow, pertaining particularly to the spinning process. A liquid crystalline pattern was noticed in polarized light, by differential scanning calorimetry, and by both shear and elongational rheology. Power-law shear thinning behavior was noticed for all the lyocell systems. The lyocell solution effective elongational viscosities were measured by a novel method, observing the flow characteristics in a hyperbolic die. These measurements correlated with shear-flow determinations were used to estimate the enthalpy and entropy changes as functions of processing conditions. Also, the flow through a converging die provoked cellulose/lignocellulose phase separation and crystallization, microfiber formation, and orientation.

ISBN

9780591904918

Pages

136

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