Chemical Substitution in Fibrous Cotton and Resistance of Substituted Cotton to Microbiological Deterioration

Abstract

The resistance for months to deterioration by microorganisms (in soil burial) of suitably acetylated fibrous cottons, some with only one-third of the hydroxyl groups substituted, depends upon the distribution of the acetyl groups as well as upon the total number of such groups present.Under usual conditions of acetylation, according to the literature, reaction takes place first in the amorphous cellulose, starting at the most accessible places. According to the present experimental acetylations and special dyeing tests, the reaction, which is probably confined at first to the amorphous cellulose, takes place along fibers in various segments and throughout cross sections rather than as a layer increasing in thickness from the surface inward. At one-third substitution the amorphous cellulose is converted to triacetate; the cotton fiber still contains about two-thirds of the original cellulose, which is present as crystalline material surrounded by acetylated cellulose. The swelling capacity of the cotton in water is greatly reduced.While the mode of attack by microorganisms is not completely understood, they apparently begin at the most readily accessible amorphous cellulose. From the literature and from the present experiments, protection by partial acetylation is believed to be due to the blocking of hydroxyl groups, the filling of spaces between chains in the amorphous cellulose, and the suppression of swelling. It represents a general method of rendering cellulose unsuitable, or at least inaccessible, as a food for microorganisms.A relatively low degree of partial saponification may detract greatly from the rot-resistance of a well-protected acetylated cotton owing to the restoration of amorphous cellulose, with loss of blocking groups and a restoration of swelling capacity. Partial methylenation by treatment with formaldehyde may impart a moderate degree of rot-resistance, which seems best explained as being due to the suppression of swelling by crosslinking. Formaldehyde-containing resins which impart rot-resistance apparently act similarly.The evidence obtained indicates that the amorphous cellulose is the part which is normally attacked, and that its ability to swell in water may be a more important factor in microbiological attack than is commonly recognized.The use of dyeing has been exemplified for qualitative tests to supplement other evidence regarding substitution and the composition and properties of substituted cottons.

Preparation of reverse osmosis membranes by surface modification of polymeric films. I. Surface acetylation of cellulose

“…However, for fol-lowing acetylations more closely by the aid of a microscope, a particular violet, Pontamine Fast Heliotrope B (DuPont).is used. 6 The films were dyed in a manner similar to that reported previously.6 The acetylated films were treated with the direct-dyeing Pontamine Fast Heliotrope B (DuPont), which dyes cellulose violet without staining acetate, and with Acetamine Yellow RR (DuPont), which dyes acetylated cellulose but does not stain cellulose that is unacetylated.…”

Physical Properties of Fibers and Yarns of Partially Acety lated Cottons

“…It is well established that the acetylation reaction hegins with the more accessible disordered '-(amorphous ) > regions, converting these to the triacetate I)efore the larger crystalline areas are reacted [ 7,11,12). Increases in breaking load and elongation of fibers above an acetyl content of 17~ possibly result from the breaking up of smaller crystallites and suhsequent release of strain within the fiher.…”

Preparation of Microbiologically Resistant Wool by Means of Chemical Modification: Part I

“…, Buras, _and Cooper[10], the real cause for resistance of acetylated and formalized cotton to fungous attack.Numerous papers (Speakman,Harris, Kirst, E16d, Hartmann …”