Changes in Fine Structure and Mechanical Properties Induced by Cyanoethylation of Cotton Yarns

Abstract

Cotton yarns were impregnated with 6% sodium hydroxide and reacted in the relaxed state with acrylonitrile at 60° ('. and different periods of time up to 60 min. to give products with degrees of suhstitution up to 2.6 cyanoethyl groups per anhydroglucose unit.As substitution increases, the x-ray diffraction pattern shows only slight alteration until substitution has exceeded 1.1, after which the crystalline structure rapidly gives way to ' an amorphous structure, complete at about DS = 2.0. At the same time density decreases nearly linearly with substitution. At the stage where the product becomes essentially amorphous, it can be annealed at temperatures of about 175° C. into a new pattern characteristic of cyanoethyl cellulose. This annealing is accompanied by a substantial density increase. Stress relaxation of the cyanoethylated yarns at a substitution of 1.1 suggests a glass-rubber transition point about 140° C. which becomes more distinct and moves to lower temperatures as substitution increases. At a substitution of about 2.0 the stress relaxation reaches its lowest value (about 4% of the value at 20° C.) at the highest temperatures tested (220° C.). With further substitution a minimum relaxation at an intermediate temperature is followed by increasing stress as the temperature is raised. This effect is associated with crystallization. Breaking strength increases slightly at low substitutions but decreases then to less than 50% for the highest substitutions. Elongation at break increases gradually, exceeding 100% above the control at DS = 2 and above.Tensile stiffness decreases to about 3% of its initial value. Work of rupture and recovery show considerable decreases below DS = 2, but sharp rises between 2.0 and 2.6. Immediate elastic recovery is little affected below DS = 2, but rises above this. Delayed elastic recovery shows continuous improvement as substitution increases, eventually exceeding the control by nearly 50%.

X-Ray Diffractometer Thermal Technique for Study of Structural Changes in Cellulosic Compounds1

“…At a temperature of about 300° C apparently some change takes place, and on subsequent examination charring was observed. Figure 6 reproduces a thermal diffractogram of a specimen of cotton yarn cyanoethylated to about 2.60 cyanoethyl groups per anhydroglucose unit [3]. Some crystalline diffraction appears to be present initially.…”

“…It has been shown [3,8] thaidiffraction from highly reacted samples in the initial or unheated form is often very diffuse and indicative of an amorphous or poorly ordered crystalline material. However, after these samples are annealed at some experimentally determined temperature, the x-ray interferences often become much sharper and more intense, indicating an improvement in the crystallite size or form in the sample.…”

“…Although the related reaction of vinyl sulfones with hydroxyl compounds has been generally known [3], the reaction shown in Equation 1 had not been reported in the literature until very recently [1,5]. Since p-oxyethyl sulfones are intermediates in the preparation of the corresponding vinyl sulfones, the use of these precursors for the chemical modification of polymers and fibers offers obvious economic advantages.…”

The Effect of Alkali Treatment on the Properties of Diatcohol Cotton

“…Also investigated was the possibility that dialdehyde or dialcohol cotton, before or after alkali treatnent, has a second-order transition temperature, such as that found for highly chemically modified cottons [3). Breaking strengths and e!ongations-at-break for 10.7% clialclehvde and 10.7% (lialcoliol before and after slack and tension alkali treatments were Fig.…”

Changes in fine structure and mechanical properties induced by cyanoethylation of cotton yarns. II. Reacted without longitudinal shrinkage

“…= 0-2.6) under conditions permitting complete freedom of longitudinal contraction was dealt with in a previous study. 3 Changes in cellulose fine structure were followed by appropriate means and accompanying changes in mechanical properties were reported. The present paper reports the results of a companion study in which the mechanical conditions of reaction prevented any contraction.…”