Ozone Fading Research Articles

Ozone fading of natural organic colorants: mechanisms and products of the reaction of ozone with indigos

Indigo, dibromoindigo, and colorants containing thioindigo and tetrachlorothioindigo were exposed in the dark to dry, purified air containing ozone (10 ppm) for 4 days, and the exposed samples were analyzed by mass spectrometry. Under the conditions employed, indigo and dibromoindigo were entirely consumed, and the major reaction products were isatin and isatoic anhydride from indigo and bromoisatin and bromoisatoic anhydride from dibromoindigo. Thioindigo and its chloro derivative also reacted with ozone, though at a slower rate; the corresponding substituted isatins and anhydrides were tentatively identified as reaction products. These results can be rationalized in terms of a mechanism involving electrophilic addition of ozone onto the unsaturated carboncarbon bond. This mechanism adequately describes the observed loss of chromophore (fading) for all indigos studied and presumably applies to other indigo compounds as well. The reaction products of indigo, isatin and isatoic anhydride, were not ozone fugitive under our conditions.

The Ozone Fading of Traditional Japanese Colorants

The Ozone Fading of Traditional Japanese Colorants

The ozone fading of traditional Japanese colorants

The colorfastness of several traditional Japanese colorants upon exposure to atmospheric ozone was tested in a chamber exposure experiment. Samples, in the form of colorants applied to paper, dyes on silk cloth, and colorants on a nineteenth- century Japanese woodblock print, were exposed to an atmosphere containing 0•40 parts per million ozone at 220C and 50% RH, in the absence of light, for 12 weeks. Color differences, calculated from the measured diffuse reflectance spectra, were used to assess the rate and extent of the ozone fading. Of the colorants applied to paper, orpiment was the only inorganic pigment that showed severe color loss after ozone exposure. Several organic colorants on paper also reacted, including the widely used plant colorants ɑi (indigo) and ukon (turmeric). The woodblock print, produced using the plant-derived colorants beni (safflower), ɑi (indigo), shio (gamboge) and aigami (dayflower), showed significant ozone fading only in the blue and green areas, which contain ɑi. Several of the dyed silk cloths also exhibited some color change in this experiment, suggesting that prolonged exposure to atmospheric ozone could pose a risk to these materials as well.

The Ozone Fading of Traditional Natural Organic Colorants on Paper

This report details the results of an ozone exposure experiment performed on a large number of traditional natural organic colorants applied to watercolor paper with no binder. These colorants were exposed in an environmental chamber to an atmosphere containing 0.397 ± .007 parts per million (ppm) ozone at 72°F and 50% RH in the absence of light for 12 weeks. This ozone concentration is typical of that found in the Los Angeles atmosphere during a heavy smog episode. The total ozone dose delivered to the samples is equivalent to about four years of exposure to outdoor air in Los Angeles or to about eight years inside a typical air conditioned building in Los Angeles.The ozone sensitivity of these colorant systems was evaluated by monitoring the color changes which occurred during the exposure. Almost all colorant systems tested showed some degree of fading after ozone exposure, and a few of these (curcumin, dragon's blood, indigo, and madder lake) should be considered very ozone-fugitive.

The Ozone Fading of Traditional Natural Organic Colorants on Paper

This report details the results of an ozone exposure experiment performed on a large number of traditional natural organic colorants applied to watercolor paper with no binder. These colorants were exposed in an environmental chamber to an atmosphere containing 0.397 ± .007 parts per million (ppm) ozone at 72°F and 50% RH in the absence of light for 12 weeks. This ozone concentration is typical of that found in the Los Angeles atmosphere during a heavy smog episode. The total ozone dose delivered to the samples is equivalent to about four years of exposure to outdoor air in Los Angeles or to about eight years inside a typical air conditioned building in Los Angeles.The ozone sensitivity of these colorant systems was evaluated by monitoring the color changes which occurred during the exposure. Almost all colorant systems tested showed some degree of fading after ozone exposure, and a few of these (curcumin, dragon's blood, indigo, and madder lake) should be considered very ozone-fugitive.

Comment on "Microspectrophotometric Study of Ozone Fading of Disperse Dyes in Nylon"

Comment on "Microspectrophotometric Study of Ozone Fading of Disperse Dyes in Nylon"

Microspectrophotometric Study of Ozone Fading of Disperse Dyes in Nylon

The fading of disperse-dyed nylon by atmospheric ozone can pose a problem at high environmental temperatures and humidities. In attempting to devise ways to inhibit such fading, researchers have suggested that the reaction between ozone and dye occurs chiefly at the fiber surface—that ozone does not penetrate inward, but that the dye diffuses outward from the fiber interior due to the concentration gradient set up as surface dye is destroyed. This mechanism has been supported, though not proved, by observations that dye diffusion is also sensitive to humidity in such systems, that rates of dye loss due to ozone exposure correlate with dye desorption rates into water, and that dye loss, like dye diffusion, depends on the square root of time and on the size of the dye molecule. These findings were based on determinations of total dye content in fiber specimens; however, adapting the techniques of microspectro photometry to fibers, as described in this paper, makes it possible to observe directly the locus of dye destruction in the fiber and to determine the relative dye loss at selected locations, such as at the edge and center of a fiber cross section. The coefficient of diffusion of the dye within the fiber can also be evaluated using the micropho tometer. These capabilities have been applied to the ozone fading of nylon 6 dyed with C.I. Disperse Blue 3, and the experimental results do not correlate with a math ematical model based on the hypothesis of dye destruction exclusively at the fiber surface. On this basis it is postulated that, in addition to dye diffusion toward the fiber surface, ozone penetration into the fiber contributes substantially to the fading process.

Ozone Fading of Disperse Blue 3 on Nylon 6 Fibers. The Influence of Physical Fiber Properties

Based on the diffusion concept of the dyestuff molecule, a model is presented to account for the influence of the physical properties of nylon 6 fibers on the ozone-fading phenomenon. To develop the model, a special series of fibers was made using widely different cross sectional shapes and texturing conditions. The fibers were dyed in a bath containing Disperse Blue 3 as the ozone-fading sensitive dyestuff. In order to study situations closely related to practice, we confined our selves to carpet yarn like types of fiber, both before and after steam heat-setting. Fitting of a mathematical model, relating structural parameters to ozone fading, showed that the molecular porosity of the structure and the specific area of the surface are the main factors involved. The contribution of the orientation did not turn out to be significant in our model. Another series, containing yarns from a considerable variety of bulking processes and producers, was analyzed in the same way to check the applicability of the model Although a rather good fit was found for most samples, some dis crepancies remained. Suggestions are given for the interpretation of these deviations.

Studies on the Ozone Fading of Anthraquinone Dyes on Nylon Fibers

A study has been made of the in service fading of a numher of blue anthraquinone dyes on nylon carpot yarns before and after heat setting. Samples were exposed to indoor and outdoor atmospheres in various parts of the U. S. A. The importance of the atmospheric humidity and temperature in the fading, suggested by laboratory testing, was confirmed. The laboratory test was shown to rank dye/fiber combinations in order of resistance to fading, and such a ranking was reproduced in the fading of samples exposed outside the houses. Inside the houses the laboratory ranking was less accu rate, illustrating the difficulties of using laboratory tests to predict the service life of a dyed nylon carpet.

Studies on the Ozone Fading of Anthraquinone Dyes on Nylon Fibers

The effects of humidity, temperature, and ozone concentration on the ozone fading of a number of blue anthraquinone dyes on nylon yarns have been studied before and after steam heat-setting. Disperse and basic dyes were found to be sensitive to the presence of atmospheric ozone at high humidity, whereas acid dyes were, in general, less sensitive. The rate of fading varied for different dyes within each of these three classes. The effect of fiber properties on the degree of fading was also studied, and the results illustrate the importance of dye diffusion in the ozone fading phenomenon.

The Effect of Atmospheric Contaminants on Light Fastness*

The reaction of dyes with atmospheric contaminants, including ozone and oxides of nitrogen, is shown to be an important factor in light‐fastness testing. Ozone, present to the extent of 0·05 to 0·2 p.p.m., is responsible for fading in exposures away from sunlight. Oxides of nitrogen also contribute to anomalous fading in industrial areas when present in concentrations up to 0·3 p.p.m. Fading has been observed on cotton dyed with certain vat, direct, sulphur, and reactive dyes, and on nylon and acetate dyed with typical dyes. Fading is greater in areas of high humidity, including sunlight exposure stations. Ozone fading is discussed in terms of occurrence, vulnerable dyes, chemical reaction, and effect of humidity. The experimental results are used to explain certain variations in light‐fastness results obtained by the AATCC in exposures at a constant number of Lacg'eys, equivalent temperatures and humidity, but in different localities.Data on various dyes and fibres are presented for three‐month exposures protected from sunlight in Los Angeles, California (an area of high NO2, very low SO2, and high ozone contents), Chicago, Illinois (moderate NO2, high SO2, and low ozone), Phoenix, Arizona (a sunlight testing station of moderate ozone, no NO2 or SO2, but low humidity) and Sarasota, Florida (a sunlight testing station of moderate ozone, no NO2 or SO2, but high humidity). Laboratory test methods for fading clue to oxides of nitrogen and ozone are correlated with the actual service‐exposure results. Exposure to irradiated car‐exhaust fumes in a laboratory chamber representing a combination of NO2 and ozone duplicates the Los Angeles exposure results. It is concluded that consideration should be given to the combined effects of atmospheric contaminants and sunlight on dyed fibres.

Correlation between Colorfastness and Structure of Anthraquinone Blue Disperse Dyes

A correlation is estahlished between the structure of blue amino anthraquinone dyes for cellulose acetate, cellulose triacetate, and the polyester fibers and the colorfastness they exhibit towards the atmospheric agents responsible for gas and ozone fading and towards the action of light. Any structural modification which reduces the electron density on the amino nitrogen attached to the anthraquinone ring, whether it is an amino, an alkylamino, or an arylamino nitrogen, will increase the resistance of the molecule to the electrophilic agents responsible for the chemical changes which occur during fading. Several anthraquinone structures with improved resistance to fading are reported. These contain, as substituents on the arylamino radical, groups which withdraw electrons from the aromatic ring, leaving the amino nitrogen with a low electron density.