It was first observed after about 90 hours of irradiation. A series of standard films, prepared with silver or aluminum spacers between two plates of sodium chloride, were scanned and absorbance plotted against film thickness to give a calibration curve. This band was centered at a wave length of 5. An ordinary rubber stopper drilled for inlet and exhaust tubes and a thermometer served as a top. Since that time the word has been generally used as a generic term for these resins and also for their many modifications. Others have suggested that the hydroperoxides formed oxidize titanium IV oxide to pertitanic acid which in turn oxidizes the film to produce chalking.

Carbonyl Absorbance of Resin A. The oxygen and nitrogen gases used were Linde U. The curve was obtained by casting films in metal spacers of known thickness and pressing between two sodium chloride plates. Since it was desired to correlate these infrared data, if possible, with data published on evolution of gases from the films, Experiment I was repeated at a higher temperature, 75 2C. These two films on their sodium chloride substrates were subjected to irradiation by a high pressure, quartz-jacketed, mercury arc in an atmosphere of water saturated oxygen.

With care, tgesis is a highly reproducible method and the versatility of modern spectrophotometers allows accuracy which may be easily refined to 1 per cent even for such ill-defined molecules as the polymers studied in this case. Infrared Spectrum of Resin A.

alkyd resin thesis

The films were allowed to dry in air for fifteen minutes and then were dried in an oven at C. Miller18 used infrared spectrophotometry in conjunction with other optical thesjs for study of the degradation of a linseed oil alkyd and has suggested that peak intensities provide a method of measurement of functional reisn concentrations which, though only an approximation, yield interesting and useful results which are not in disagreement with data obtained from analysis of gaseous degradation products and reflectance studies.

The solution of resin was then placed fhesis on sodium chloride disks 25 mm. During the first 50 hours of the irradiation, Log A a and therefore the log of anhydride concentration, is proportional to time. Both processes were carried out at 75C.


A study of some factors affecting the degradation of alkyd resins

In this section, however, chronology has been ignored in favor of clarity and continuity in discussing results. The ready availability of calcium thessi optics provides much better resolution in the micron region than is available with sodium chloride optics, allowing the accuracy akyd the instrument to be used to the greatest advantage.

These plots showed the data to be badly scattered during the early hours of the irradiation. The Experimental section of this paper is reported in the chronolo g ical order in which the work was done.

Hartwe11 12 has shown that the rein frequency is re markably sensitive to substituents attached to the carbonyl carbon. When it was desired to measure thicker films, the absorbance of the 6. Figure 4 shows this region of the polymer spectrum at various stages in the irradiation. This holder is described and illustrated in the Experimental section of this paper. Past research into the chalking process has centered around two mechanisms.

This layer shields lower layers of the ester from the ultraviolet irradiation and results in the striking decrease in the observed rate of the reaction. The conclusion to which the author is forced, in the light of this result, is that the degradation process consists of an initial photolytic cleavage of the polymer at the site of the ester linkage. During the first 50 hours of the irradiation, Log Aa’ and therefore the log of anhydride concentration, is proportional to time.

Thermal decomposition of phthalate esters is well known, but for such a reaction to proceed, much higher temperatures than those employed here are required. Jacobsen has shown that in addition to carbon dioxide other oxygenated products are formed by ultraviolet irradiation of pigmented films with simultaneous reduction of the pigment.

A 1 inch Fie. 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 linseed oil portion of the polymer.

A study of some factors affecting the degradation of alkyd resins

Thesis — University of Florida. Kienle in coined the name “alkyd” and which in his words, “include the complexes resulting from the reaction of polyhydric alcohols and resinifying carboxylic organic acids such as 14 the polybasic acids and their anhydrides. In order to avoid the increased complexity introduced by the linseed oil degradation and reein samples of the unpigmented resin rresin more easily prepared for irradiation, Resin A was chosen for exclusive use in the remainder of this work.


This holder is described and illustrated in the Experim e ntal section of this paper.

The wave lengths and relative intensities of these bands at 5. If log absorbance of the PAGE 47 41 en s:! As early as patents were granted to the General Electric Company for glyceryl phthalate resins modified with oleic acid and castor oil. It was first observed after about 90 hours of irradiation. 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.

As expected, Resin C was degraded at a noticeably faster rate than were the other resins.

alkyd resin thesis

Use of the calibration curve permitted rapid evaluation of the thickness of films whose thickness was on the order of cm. The first, originally postulated thesus Renz in21 attributes the decomposition of the film to a cyclic oxidation-reduction process involving the pigment.

alkyd resin thesis

Thesid predictions are observed to be quite correct. 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.