Cleaning Textiles using Liquid Carbon Dioxide – Evaluation of LCO2’s effect on white natural and synthetic fabrics

The subject of this Master thesis is the use of liquid carbon dioxide (LCO2) to clean textiles. The purpose of the research was to establish whether LCO2 is a suitable cleaning agent for museum textiles.

Cleaning was conducted by Fred Butler, a professional dry-cleaning company using an Electrolux gamma LCO2 machine on programme P3-4 (4 bath). Model textiles were cleaned using liquid carbon dioxide, special antistatic non ionic detergent CLIPCOO and a non ionic fabric softener Arlamol PS15-LQ (RB) at 5 to 10°C and a pressure of 4000kPa (40 bar). Seventeen samples of new, white model textiles comprising cellulose acetate, acrylic, cotton, linen, polyester, silk, wool and viscose (regenerated cellulose) were cleaned. All 17 samples were exposed to one cycle of the LCO2 cleaning solution, 4 of them were exposed to ten cycles, 3 were subjected to ten cycles and an accelerated ageing regimen and dirt was applied to 3 samples prior to cleaning with one cycle.

Deterioration of model textiles induced by cleaning was determined from changes in physical and optical properties before and after treatment. Tensile testing and extension to failure were determined using a tensile testing machine, fibre density and dimensional changes were used to determine shrinkage, weight loss was employed to quantify  removal of material during  cleaning, visual examination was used to examine changes in curling of fibres, matting, texture, gloss, colour change and static electricity, change in colour was measured using spectrophotometry. Cross sections of cellulose acetate samples were examined by optical photomicroscopy.

The ability of LCO2 to remove soil or dirt from textiles was also evaluated. Sources of soil investigated in this research were palm oil which is chemically similar to fingerprint residue, a mixture paraffin oil of and carbon black which represents organic soil. Soils’ removal was evaluated from colour change using spectrophotometry, weight loss and macroscopic and microscopic changes in appearance.

The results of this research clearly indicated that the effect of LCO2 varies between textile types and soil types. The tensile strength of protein-based textiles including wool and silk increases after one cycle of LCO2 cleaning. By contrast, the tensile strength of cellulose-based textiles such as cellulose acetate, linen and viscose is reduced after one cycle. The tensile strength of more than 50% of the samples containing cotton is increased by cleaning. All synthetic textiles including acrylic and polyester, lost strength on cleaning.
The tensile strength of silk, wool and viscose was increased by 10 cycles of LCO2 cleaning while that of cotton was reduced.
Cleaning with liquid carbon dioxide was effective at removing paraffin oil and palm oil but not particulates such as carbon black.