NaCl dehydrates hydrophilic group nonionic surfactants. Therefore, CMC decreases. The length of the hydrophobic block polymer micelles is not reduced. All these substances are poorly soluble in water and therefore soy lecithin does not have CMC in an aqueous solution, The lecithin phospholipids can form. Nous supposerons que dans la phase aqueuse, la concentration de ces molécules est* égale à leur concentration micellaire critique (CMC). Considérons un.
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This suspension has dealt a major blow to the conservation community, especially in the United Kingdom, where it is the primary surfactant used. A substitute was needed, and so from an initial list of 24 possible replacements, 11 were selected for testing.
The critical micelle concentration for each of the 11 surfactants was determined experimentally, as it was not available from every manufacturer. By testing washing efficiency through observation cgitique color change before and after washing, and also recording the pH and conductivity of the wash liquor, the 11 surfactants were reduced to 5. Further testing of the remaining 5 surfactants involved accelerated aging of washed textiles and measurement of the resulting color, pH, and tensile strength.
Se necesitaba un substituto por lo que de una lista inicial critiaue 24 posibles substitutos, se seleccionaron 11 para ser evaluados. Synperonic N, previously known as Lissapol, has been widely used in conservation since its recommendation in Plenderleith’s book on the conservation of antiquities and works of art Plenderleith Nonionic surfactants are generally low foaming and unreactive to metal ions. Anionic surfactants may form insoluble compounds with multivalent ions such as calcium and magnesium.
Hence the use of anionic surfactants in hard cirtique or, for example, with metals, rcitique stones, and calciumor nicellaire fibers such as paper, produce problematic insoluble deposits. In such cases, a nonionic surfactant may be a better choice. Degradation of nonylphenol ethoxylates occurs by a progressive shortening of the polyoxyethylene hydrophilic chain, making the compound progressively less soluble and increasingly associative to other suspended solids.
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The shortening of the chain also makes further biodegradation more difficult, and critiquee nonylphenol ethoxylates are ultimately biodegradable, i.
In vitro studies showed that nonylphenol has an estragenic concdntration three to six orders of magnitude less potent than estradiol Jobling and Sumpter ; Jobling et al. Structure of a Synperonic N molecule with the average polyoxyethylene chain length of eight ethoxy repeat units. The recommendation followed that nonylphenol ethoxylates be phased out for domestic purposes by and for industrial use by ICI no longer sells these products within the EU.
Although a range of Synperonic surfactants still exists, in these a large alkyl group replaces the hydrophobic nonylphenol group of the Synperonic N. The fact that Synperonic N is no longer available has dealt a major blow to the conservation community in Europe, where it was the dritique of choice, as it was the only surfactant recommended by a scientist Plenderleith and has proved highly efficient on cotton and wool. In the few comparison investigations with an alternative nonionic detergent used in Europe Gentle and Muller ; Lewis and Eastopthe results were inconclusive or served to underline the cleaning power of Synperonic N.
The need to replace Synperonic N is immediate due to the phasing out of its use in Its replacement mixellaire be not only an environmentally sound nonionic surfactant but also efficient and acceptable to micellairs conservation community.
Washing is a nonreversible, interventive treatment and should be carried out with maximum efficiency to deter the need for repetition. The critiqie of the present study was to find one or more suitable alternatives to Synperonic N, principally by studying their cleaning properties on artificially soiled textiles.
Surfactants are at their most effective at or above their critical micelle concentration CMC. As the micelles solubilize the soil, the concentration of available micelles is reduced and the surfactant becomes less effective. Therefore, it was decided that the surfactant solutions should be used in concentrations that were several times their CMC. This technique allows for some of the surfactant micelles to be used up concentation the washing process without reducing the cleaning efficiency.
In textile conservation, surfactants are used at 2 to 10 times the CMC, with the higher values saved for heavily soiled textiles. For the purpose of this experiment, the surfactants concentartion tested in a solution at five times their CMC. As air bubbles leave a capillary tube immersed in a liquid, the pressure of the air in the tube varies as the bubble is formed and then leaves the capillary.
In this apparatus, the variation in pressure of nitrogen bubbles as they were formed and left the capillary was recorded graphically micellaore a transducer connected to a computer for recording results.
The pressure transducer consisted of a silicon diaphragm. The disc distorts when pressure is applied, in turn altering the electrical resistance of the silicon in an anisotropic way, the resulting resistance difference reflecting the pressure difference.
The apparatus is calibrated with toluene to obtain the apparatus constant A.
For each surfactant, the pressure change during bubbling in a range of solutions from 0. The values were introduced to Sugden’s equation, and the surface tension of each solution calculated g is the acceleration due to gravity Sugden The resulting CMC values can be seen in table 1. After consultation with conservators and the conservation literature, a list of surfactants suitable for testing was compiled by a working group that included the authors and two other members of the conservation department at the British Museum.
Judy Daniels Uniqema advised on alternatives from the new Synperonic range. The initial list of 24 alternative surfactants was reduced to 11 with due consideration given to availability and the technical literature. The cleaning efficiency of distilled-water solutions of these 11 surfactants and Synperonic N were determined experimentally using distilled water as a control.
The pH and conductivity of the wash liquors were also monitored. Along with its availability and expense, the other main factors that should be considered include efficiency of cleaning and residue Cobcentration de Graff ; Timar-Balazsy and Eastop Initially conentration cleaning power of detergents is the most important consideration.
The detergent should be capable of removing common dirt types and solubilizing waxes and greases. There should be no residue of detergent deposited on the surface of the textile. To achieve this result, detergents with low fiber affinity are used, although this quality often reduces washing efficiency.
Residues may be directly observed using scanning electron microscopy or measured quantitatively using time-of-flight secondary ion mass spectrometry Howell and Carr These techniques were not used in this critiquee, as we were not directly interested in determining the actual residues on the textile.
Instead, the levels of water-soluble acids and ionic species were monitored by following the pH and conductivity of the wash water. This first set of experiments aimed to provide a subset of approximately six surfactants for further testing.
The selection criteria were based chiefly on efficiency of cleaning, taking into account the conductivity and pH of the washing solutions as indications of rinsing efficiency. To determine the cleaning efficiency, the color change was measured after experimental washes were performed on standard soiled wool and cotton fabrics. Many standard crltique fabrics are commercially available; those used for these experiments were manufactured by Testfabrics.
The soiling had an initial concentrahion of keltex 1. The fabric comes in a strip half printed with the standard soil fig.
Rolls of both wool style and cotton style textile were obtained. These fabrics were kept in a refrigerator when not in use to prevent mold growth.
JAIC , Volume 43, Number 1, Article 5 (pp. 55 to 73)
A textile conservator devised a standardized manual cleaning technique so that it reflected the standard cleaning regime that would apply to a textile table 2. The use of a mechanical shaker was investigated instead of using manual sponging of the object. By lengthening the washing time, the mechanical cleaning regime produced approximately the same color-change results as the manual hand washing table 3.
The mechanical regime was used in the first round of tests, and the manual method in the second round. Photograph of fabric samples after washing wool on the left, cotton on the critiqe. Discs of test fabric 80 mm diameter were cut from the wool and cotton fabrics so that half of the disc was clean and the other half soiled see fig.
Using a Minolta CR Chroma Meter, which was calibrated using the standard tile provided by the manufacturer, the color of the surface was measured five times at three points on each half of the fabric using a Melinex template to locate the measuring areas. The textile discs were then placed faceup in a cm3conical flask with a screw-top stopper, and cm3of the test solution was added.
The washing followed the regime described in table 2. As the solutions were emptied from the flasks, 50 cm3 was saved for pH and conductivity measurements. The fabric discs were placed on a Melinex sheet miicellaire dry overnight before the color was remeasured as described above.
The conductivity behavior of solution samples obtained during the cleaning of the model textiles was similar whether wool or cotton was being washed. The conductivity of samples from nonionic cleaning was low-ranging from 7. The pH readings ranged from 4. Triton XL80N samples varied from 4. Otherwise the pH readings fell within the acceptable limits. The results were transferred to two graphs for initial analysis, with each graph figs.
These graphs were useful, concentratioj they gave a direct indication of the cleaning ability of each surfactant, with the gray columns representing the soil liberation from the presoiled areas.
The white column on figures 5 and 6 represents soil redeposition to the clean area, but this finding concejtration only confirmed by reviewing the original data.
In all instances the values for color change of the soiled areas were opposite in sign to those of the unsoiled areas, representing soiling of the clean side through redeposition.
In all cases the clean concentratino of textile became darker due to redeposited soiling, while micellaier dirty area became cleaner. The pH of the wash water of all the surfactants except Triton XL80N was within the ranges discussed above, and therefore Triton XL80N was eliminated from further testing because of its low wash-water pH. The conductivity of the wash water of all the surfactants was so similar that no surfactants were further eliminated on this basis.
The combined list contained seven surfactants for further testing: Irgasol PL and Saponin were not brought forward for Fig.
The selection process was reviewed, and the list for further crifique agreed to by the rest of the group. The seven best surfactants identified in the first phase of this study included two pairs of chemically similar nonionic surfactants from the same manufacturers: Phase 2 was to investigate whether artificially aged samples of surfactant-cleaned cotton and wool textile produced any effect that would cause a change in color or pH or reduce the tensile strength.
The five surfactants listed above were tested with water as a control. Tensile testing was to be carried out on 15 strips each of the Testfabric cotton and wool textiles, each measuring 15 x 70 mm and cut parallel to the weft.
To minimize any variation that might occur in the fabric, three sequential blocks of fabric measuring x 70 mm were cut from the roll. Each of these blocks was equally divided into six parts and numbered 1—6 accordingly. When washed and dried, the pieces were then cut into 5 equal strips, giving a total of 15 strips for each surfactant fig. These samples were then aged as described below. A second set of samples was prepared in exactly the same manner, but these samples were not aged.
Critical micelle concentration – Wikipedia
Color measurements on the cleaned samples were made as previously described, and these were aged in a light box fitted with Philips PL-L 36W compact fluorescent lamps color 84, lumen, color temperature K Daniels and McIntyre Pictorial description of the division of the fabric for tensile testing to prevent any bias due to natural variation Concentratlon.
Allocation of Sequence Number to Surfactant for Washing was To even out differences in environment, the samples were rotated in position and turned over at weekly intervals during the day aging period. For tensile testing, the samples were concentratoon using a scalpel into strips measuring 15 x 70 mm, as described above.