Influence of liquid ammonia on the structure of wool fiber

Green chemistry works towards making chemistry more benign and environmental friendly. In previously done studies N-heterocyclic carbene catalysis has been used in synthesis creating a range of different molecules. This was done with aerial oxygen as the terminal oxidant and made possible by the help of so called electron transfer mediators, ETMs, creating a low energy path for the oxidation step of the reaction. One way to make this type of reaction even greener would be to use a more benign solvent, like water. This proves to be a problem since organic molecules tends to be hydrophobic. This thesis shows that by changing the used hydrophobic ETM to a more hydrophilic one made the model reaction possible to be carried out in water.

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Implementation of water as solvent in aerobic oxidative NHC-catalysis

In order to enhance the shrink-resistant properties of wool to achieve a machine washable effect, the effect of water-soluble polyurethane polymer on a worsted wool fabric which was modified by liquid ammonia and protease was investigated. The worsted wool fabric was pretreated by a continuous liquid ammonia finishing machine and then treated by protease, followed by polyurethane nano-emulsion coating. The results showed that, after liquid ammonia and protease treatment, the surface scales of wool were seriously damaged, even partly peeling off, and the disulfide bond content of the wool decreased while the active group content of the wool increased. Furthermore, after polyurethane finishing, the surface scale and the gap between the scales were covered with a thin film, and the area shrinkage reached 3.1% when the concentration of polyurethane was 20 g/L, showing an effective improvement in the shrink resistance of the worsted fabric. As far as our knowledge goes, this is a systematic report on the synergistic effect of liquid ammonia, protease, and polyurethane on the shrink resistance of wool fiber, and provides a new method for the commercial application of shrink-resistant finishing of wool fabric.

Synergetic Effects of Liquid Ammonia, Protease, and Polyurethane Nano-Emulsion on Improving Shrink Resistance of Wool

Liquid ammonia as a non-aqueous medium has many physical properties close to water, such as small molecular weight and strong permeability. It has been widely used for the ecological processing of cellulosic fibers to improve their luster, softness and dyeing properties. However, there are few reports on the dyeing of wool treated with liquid ammonia, especially at a lower temperature. Herein, a continuous liquid ammonia finishing machine was used to batch process wool followed by dyeing in a commonly-used wool dyeing machine. The results showed that many scale flakes and some cuticle cracking were seen on the fiber surface, and the disulfide bonds of cystine were broken down after liquid ammonia treatment, which promoted the diffusion of dyestuff into the fiber. Moreover, the uptakes and K/S value of wool dyed with Lanaset and Lanasol CE dyes were higher than the untreated wool, and the dyeing temperature could decrease to 85 °C, while the degree of fiber strength reduction merely decreased by 3–5%. Furthermore, for the reactive dyes, the dyeing temperature can reduce to 70 °C with the chemical auxiliaries Miralan LTD, while the degree of strength reduction decrease by 8–10%. Liquid ammonia treatment can be used for dyeing at a lower temperature than boiling temperature (100 °C), reduce energy consumption and reduce the degree of fiber strength reduction of wool. The method shows considerable to great value and is significant in providing a feasible approach for the industrial application of low-temperature dyeing technology.

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Liquid-Ammonia-Mediated Dyeing Process of Wool at a Lower Temperature

The changes caused in wool fibres by treatment with liquid ammonia were investigated with DTA, TG and DTG. It was established that the thermal stability of wool undergoes a significant increase, depending on the duration of treatment with liquid NH3.

E. Stelmasiak

Papers

Change in thermal properties of wool after treatment with liquid ammonia