The Smathers Libraries would like to learn more about this item and invite individuals or organizations to contact the RDS coordinator ufdissertations uflib. In order to shed some light on this question, films of Resin A were placed in the irradiation cell but were shielded by aluminum foil from the ultraviolet rays. The number of fringes and the wave lengths between which they are observed are related to cell thickness by the equation where bis cell thickness in microns and n is the number of fringes observed between the wave lengths Al and A 2 also measured in microns. Oxygen was bubbled through trap B, which, in this case, was filled with water, and then passed through the irradiation cell and out through mercury trap M, adjusted to maintain the pressure in the system at about 10 mm. Degradation of Ester Carbonyl in Moist Air at 30c. The ready av a ilability of calcium fluoride optics p rovides much better resolution in the micron region than is available with sodium chloride optics, allowing the accuracy of the instrument to be used to the greatest advantage. University of Florida Holding Location:
A study of some factors affecting the degradation of alkyd resins Added title page title: The samples were located about 10 cm. Rearranging this equation gives, PAGE 41 35 Table 3 shows the data calcul a ted from this equation and Fi g ure 9 shows the deviation o f these data from the 0 constant value, Ae Two possible explanations for this devi a tion of the total carbonyl concentration from the initial carbonyl concentration are: This erosion of the vehicle results in loss of gloss due to scattering and absorption of light by particles of the pigment which are now on the film’s surface. Degradation of Ester Carbonyl in Moist Air at 30c. In an effort to determine if a peroxy-ester intermediate could be involved in the degradation, Experiment II was repeated with an atmosphere of dry nitrogen substituted for moist oxygen.
With care, it is a highly reproducible method and the versatility of modern spectrophotometers allows accuracy which may be easily thrsis to 1 per cent even for such ill-defined molecules as the polymers studied in this case.
Phthalic anhydride and the resin showed less association in solution than did phthalic acid and there fore more concentrated solutions of the anhydride and resin could be used. The ready availability of calcium fluoride optics provides much better resolution in the micron region than is available with sodium chloride optics, allowing the accuracy of the instrument to be used to the greatest advantage. Because of the difficulty of transferring ether solutions quantitatively, several solutions were prepared by weighing samples of the anhydride and dis solving them and then running the spectra as soon as possible to avoid concentration changes due to evaporation.
A study of some factors affecting the degradation of alkyd resins
Comparison of Figures 4 and 5 was considered to constitute sufficient evidence for the identification of the degradation product rein phthalic anhydride.
Cell thicknesses were measured by measuring interference fringes produced by the empty cell.
The initial cleavage of the polymer is thought to occur at the site of the ester linkage and is probably free radical in nature. This is not to say that subsequent reactions in the overall degradation process are not of the thermal type.
Film Thickness for cm. VVO’ A second film was irradiated simultaneously with that described above and was of such a thickness that the ester carbonyl absorbance could always be measured by the Model 21 spectrophotometer. The irradiation was discon tinued after hours. The principal degradation product was identified as phthalic anhydride. Both processes were carried out at C.
This method has, on occasion, been successful when films were cast on the surface of a pool of water or mercury and allowed to harden. These plots showed the data to be badly scattered during the early hours of the irradiation.
The resin used was an unmodified glycerol phthalate which will be designated as Resin A throughout the remainder of this paper. In general these are long chain fatty acids with as many as three carbon-carbon double bonds per carboxylic acid group.
One would predict qualitatively that the rates of degradation of Resins A and B should be approximately equal and the rate for Resin C should be somewhat greater due to attack at the sites of unsaturation in the aloyd oil portion of the polymer.
These two films on their thfsis chloride substrates were subjected to irradiation by a high pressure, quartz-jacketed, mercury arc in an atmosphere of water saturated oxygen. PAGE 21 15 Fig. Thermal decomposition of phthalate esters is well known, but for such a reaction to proceed, much higher temperatures than those employed here rsein required.
It was also found that concentrations of phthalic acid and phthalic anhydride as low as l and lO-3 molar respectively could be detected by infrared by use of mixed solvent systems of chloroform and absolute ethanol or ether in thick cells, and with a slit width of about microns. To further eliminate errors due to solvent absorption, a cell of approximately the same thickness as the sample cell was filled with the solvent mixture and placed in the thedis beam of the spectrophotometer.
The change of slope near 50 hours, it is felt, indicates the build-up of a layer of phthalic anhydride on the surface of the film.
The methods of determination of thinner films described in Chapter II gave erratic results. Since that time the word has been generally used as a generic term for these resins and also for their many modifications. The wave lengths and relative intensities of these bands at 5.
The very rapid rate at which the ester is attacked in the presence of oxygen, as illustrated by Figures 10, 11, and 13, raises the question of whether the degradation is essentially a thermal process or whether a free radical type process is operating.
A study of some factors affecting the degradation of alkyd resins
Wlkyd this temperature, alkkyd thinner film was rapidly eroded to the extent that the carbonyl band at 5. In this section, however, chronology has been ignored in favor of clarity and continuity in discussing results. Miller used infrared spectrophotometry in conjunction with other optical techniques for study of the degradation of a linseed oil alkyd and has su g gested that peak intensities provide a method of measurement of functional group concentrations which, thou g h only an approximation, yield interesting and useful results which are not in disagree ment with data obtained from analysis of gaseous degradation pro d ucts and reflectance studies.
Hartwell 12 has shown that the carbonyl Ifrequency is remarkably sensitive to substituents attached to the carbonyl carbon. Formulation of Alkyd Resins. The tuesis were usually prepared in two classes as indicated in irradiation Experiment I. Appreciation is also expressed to the General Motors Corporation for the Fellowship w hi c h made this work possible and to the Renshed-Mason Company for formation of the resins used in this stu d y.