Crystalline Cellulose and Cotton Fiber Strength

Abstract

The variation in the bundle fiber strength measurements of cotton (Gossypium hirsutum L.) fibers due to differences in cellulose crystallinity and chain length have not been examined. This study was conducted to determine the length of the cellulose chains (expressed as the weight‐average molecular weight, M̄w) in the crystalline microfibrillar fragments isolated from different cotton fiber and to relate these values to bundle fiber strength. Crystalline microfibrillar fragments were isolated by treating cotton fibers with acetic acid/nitric acid reagent. The crystalline cellulose was dissolved in a lithium chloride solution of N,N‐dimethylacetamide. The 13C‐nuclear magnetic resonance spectrum of the cellulose solution showed chemical shifts at 103.1, 73.2, 74.2, 75.8, 78.5, and 59.9 ppm for the glucose carbons. The chemical shifts were similar to the chemical shifts in the 13C‐nuclear magnetic resonance spectra of other cellulose solutions. The sharpness of the chemical shifts indicated a true solution of crystalline cellulose. Gel permeation chromatography of the crystalline cellulose solution on three linear columns of 1 × 106 Å to 500 Å of ultrastyragel in a Waters 150C GPC separated the dissolved crystalline cellulose into a population of different sized molecular weight chains. The weight average molecular weight of the population of cellulose chains in the crystalline cellulose from TM‐1 cotton fibers was 1.83 × 105 daltons. The average length of the cellulose chains in the crystalline cellulose (measured as the weight average molecular weight of the crystalline cellulose) from different cotton fibers was correlated (r = 0.94) to the bundle fiber strength of the cotton fibers. The data support the conclusion that the average length of cellulose chains in the crystalline cellulose areas of the microfibrils is a component of bundle fiber strength measurements of cotton fibers.