Chemical kinetics of photo-oxidative degradation of dried linseed oil and trilinolein films

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Chemical kinetics of photo-oxidative degradation of dried linseed oil

and trilinolein films

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ERRATUM SHEET

"CHEMICAL KINETICS OF PHOTO-OXIDATIVE DEGRADATION OF DRIED LINSEED OIL AND TRILINOLEIN FILMS"

by R. S. Yamasaki

(DBR Internal Report No. 289)

o

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filter 6527 A was used. "

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sodium. chloride prism" should read "infra-red

spectro-photometer with a sodium chloride prism"

Page 15, first-line of footnote - "CH

3(CH2) 4 - CH = CH - CH ... "

should read "CH

3(CH2)4 - CH

=

CH - c"H ... "

hr

Page

16,

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+

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2ｾ II should read

"

Page 17, hr equation (16) - ＢｒｉｃｈＲｃｏｒｾ "R ICH 2COR hv ) " " should read

Page 17, equation (17) - "RICOCOR hr) RICO.

+

RCO" should

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PREFACE

The performance of paints appears to be a continuing

problem in every country in which they are widely used. It is

still not possible to predict. from relatively simple, short-time te sts in a laboratory, what the performance of a given paint is likely to be and this presents a real challenge in paint research. The study now reported was planned to provide information on the chemical reactions involved in the degradation of linseed oil which is commonly used as the film-forming constituent in house paints as part of a program on the assessment and improvement of paint durability.

The author. a physical chemist, is a re search officer in the Organic Materials Section of the Division, engaged in paint studies.

Ottawa June 1964

N. B. Hutcheon, As sistant Director

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-TABLE OF CONTENTS

INTRODUCTION

GENERAL PROCEDURE LINSEED OIL FILM

(a) Procedure

Selection of film

Selection of degradative agents Selection of analytical techniques Study of degradation

(b) Results and Discussion Gas analysis

Analysis of infra-red spectra of film Analysis of ultraviolet spectra of film (c) Interpretation of Results

(d) Conclusions TRILLNOLEIN FILM

(a) Procedure

Selection of film material Special apparatus

Study of degradation (b) Results and Discussion

Analysis of volatile products Film analysis

(c) Interpretation of Results (d) Conclusions

SUGGESTIONS FOR FURTHER WORK REFERENCES Page 1 1 2 2 2 2 3 4 5 5

6

7 7

9

10 10 10 12 13 13 14 15

19

20 21

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CHEMICAL KINETICS OF PHOTO-OXIDATIVE

DEGRADATION OF DRIED LINSEED OIL

AND TRILINOLEIN FILMS

by

R. S. Yamasaki

Paint films, on exposure to weathering, undergo deterioration and eventual breakdown which may be characterized visually by

yellowing, loss of gloss, chalking, cracking, blistering or peeling. Many

investigations have been made in efforts to find ways of improving the

durability of paints. Most of these have been empirical in nature and

have not contributed greatly to a knowledge of the basic degradation

processes. The present study, primarily concerned with the performance

of house paints, was de signed to develop a better unde rstanding of the degradation reactions.

Of the components in paint, the film-former or the binder is considered the most essential since it determines the useful life of the

film. For exterior house paints one of the most common binders used

is linseed oil. Therefore, study of the degradation of linseed oil was

considered for investigation.

The literature shows that Elm (1) has summarized the work on dried linseed oil film up to 1949 and Crecelius et al have since studied the chemical effects of ultraviolet radiation and oxygen on thick and thin

dried linseed oil films by infra-red spectroscopy (2,3). Miller (4) and

Cowan (5) have written more recent reviews. These studies show that

further information is required to elucidate the mechanism of the

degradation processes taking place in linseed oil film. A study was

undertaken, therefore, to investigate the chemical kinetics of photo-oxidative degradation of dried films of linseed oil and of one of its pure components trilinolein.

GENERAL PROCEDURE

One of the main difficulties in obtaining more basic knowledge on this subject is that there are many factor s to contend with, both with

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2

-are chem.ical and physical change s to consider. Thus for this study

an effort was directed toward selection of simple st paint systems and

isolation and better control of the degradative agents. Only chemical

changes were observed.

I. LINSEED OIL FILM

(a) Procedure

Selection of film

In general, paint consists of .pigment, vehicle and drier. Of

these the essential component in the coating is the vehicle since the nature of the film-former or the binder resulting from it determines the

useful life of the film. For exterior house paints the most widely used

binder is the linseed oil. Therefore it was chosen as the first film-former

to be studied.

To obtain a satisfactory dried film, driers are normally

incorporated in the binder. Here lead and cobalt salts were chosen to

promote body and surface drying, re spectively, with negative radical

octoate rather than naphthenate since its composition is known. The se

drier s were added in small amounts to minimize contamination and yet produce a satisfactory dried film.

Free films rather than supported films were selected for study to provide double the surface for reaction and for subsequent analysis since, it was a s su me d that much of the reactions of interest take place

at the surface. In addition, free films enabled instrumental analysis of

a given film at both infra-red and ultraviolet regions, thus obviating the difficulty of f irid irig substrates that give adequate transmission of both radiations for satisfactory analysis.

Selection of degradative agents

Of the weathe ring agents to which exterior paint films are normally exposed, oxygen, ultraviolet radiation, and water vapour were considered

for study. The degradative process for linseed oil film is primarily

oxidative (4). Therefore for environm.ental abnosphere gaseous tank

oxygen (99.7 per cent) was used, and in pure form to encourage film deterioration.

The ultraviolet radiation should in the first instance simulate

that of the sun with respect to spectral distribution. To isolate possible

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4

-different times and detected by their influence on the thermal

conductivity of the carrier gas. Thus, by determining the retention

time and the difference in thermal conductivity, relative qualitative and quantitative analyse s , re spectively can be carried out.

Here, two Perkin-Elmer Vapor Fractometers, Model 154C, were used in tandem with synthetic zeolite column for separation of perma nent gases and silica gel column for separation of carbon dioxide, hydrogen and C

l to C3 hydrocarbons.

Study of degradation

After some experimentation, linseed oil solution, containing minimum quantities of drying agents for the production of satisfactory film, was prepared by adding 0.030 per cent of lead and 0.025 per cent

of cobalt as octoates to alkali-refined oil. Free films about 251-1 in

thicknes s were prepared by drawing the solution on a tin panel with a 121-1 doctor-blade, letting it dry overnight for 17 hr at 22.±.loC, relative humidity of 53.±. 1 per cent, and under normal i.ndoor illumination and

subsequently loosening the film by mercury amalgamation of the substrate. Films were cut to suitable size and placed on rectangular (2.0 x 1. 5 cm)

pyrex rod frames fitted with handles. Then a pair of films was enclosed

in each T - shaped pyrex exposure tube (250 ml) as shown in Figure 1. The

vertical arm of the exposure tube when immer sed in dry ice -acetone bath served as a cold trap for the volatile products.

To determine the over-all volatiles evolved, tubes were individually filled with water vapour saturated oxygen, and dry oxygen and were

irradiated with uv radiation for 437 hr. The volatiles were analyzed by

mass spectrometry. For the main experiments two sets of three tubes

each were indivually filled to 62 cm mercury pressure with dry oxygen, water vapour saturated (at 25°C) oxygen, and water vapour saturated

high purity nitrogen

(99.99

per cent, 02

<

20 ppm). The moisture-laden

nitrogen was obtained by bubbling the gas via filter stick through water

which had previously been deoxygenated. Deoxygenation in turn was carried

out by bubbling through nitrogen until the effluent showed no traces of oxygen.

One set of tube s was exposed to monochromatic uv radiation, the other to normal indoor illumination such that the effect with respect to

time of each individual exposure agent could be studied. Linseed oil film

typically absorbed 30 per cent of the incident uv radiation. The cells were

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5

-Films and atmosphere were analyzed periodically during the

course of exposure. After each set of analyses the films were returned

to the tube, which was then refilled with the appropriate atmosphere, and

subjected to further exposure. Check exposures were made. Irradiated

and non-irradiated films were studied up to 3000 hr.

For the analysis of volatiles, 25 cc of gas was removed from each

tube. For this the precision sampler attachment was connected to the

exposure cell, the gas chromatography apparatus, ｾｮ､ the vacuum pump

so that the sampler could alternately be evacuated and filled with test

gas which is then swept in with carrier gas for analysis. Silica gel

column J was employed for carbon dioxide and hydrogen analyses and

molecular sieve column I for carbon monoxide. For carbon dioxide and

carbon monoxide analyses the sample gas was passed through the J column

kept at 100°C and then through the I column at 80°C, using helium as a

carrier gas. For hydrogen analysis a separate sample was passed through

the J column thermostatted at 50°C using dry nitrogen as a carrier gas.

Because of the difficulty of "tailing" with the column material available, the substance with mass 58, as determined by mass spectrometry, and

water vapour wer e not further analyzed. Gas mixture G- 7 (Phillips

Petroleum Company, Special Products Division, Bartlesville, Oklahoma) containing known concentrations of carbon dioxide, carbon monoxide and hydrogen, among others, was used for calibration.

-1

For infra-red analysis films were scanned from 4000 to 670 ern and changes in band intensity and half-band width were studied.

For uv analysis films were placed in a special holder as shown

in Figure 2. This was necessary because the film absorbed very strongly

at about 225 rn ｾ and in order to obtain meaningful "on scale" readings, the

comparison reference beam itself had to be partially closed off. The

working reference, in turn, was referred to a normal one to obtain true absorption. The strong sample absorption also attenuated the incident radiation so much that the stray light error became appreciable.

Neverthe-less, this was not considered serious enough to affect the interpretation

of the general trend studied here. Use of thinne r films to decrease

absorption resulted in premature rupture of the films. The spectra were

plotted from 210 to 310 m u to follow the changes in concentration of

two and three conjugated double bonds at 230 and 260 to 280 m

u

respectively.

(b) Re suIts and Discus sion

Gas analysis

Mass spectrometric analytical data on volatiles evolved as a

result of exposure of linsee d oil films are given in Table 1. They show

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••

6

-one -tenth each of hydrogen and probably carbon monoxide.

In order to identify further any trace volatile compounds evolved a larger amount (65 cm 2) of linseed oil film on pyrex tubing was dried for twelve days and exposed to dry oxygen and uv radiation for 356 hr.

The substance with mass of 58 was found as well as traces of formaldehyde. Thus volatile s evolved in any significant amounts are carbon dioxide,

hydrogen, probably carbon monoxide, substance with mass of 58 and also probably water vapour.

The kinetics of evolution of carbon dioxide and carbon monoxide

per film are illustrated in Figures 3 am 4. The dotted portions of the lines

denote time lapse for analysis. Films exposed to highly humid oxygen

and uv radiation ruptured after the second exposure period. Moreover,

for some reason, carbon monoxide could not be detected in such exposure. Hydrogen was not detected in all exposure s although sensitivity of the instrument for it was comparable to that for carbon monoxide.

Analysis of infra-red spectra of film

Typical infra-red spectra of linseed oil, liquid and dried film are given in Figure 5 to illustrate changes before and after exposure to oxygen and uv radiation for 172 hr.

The change s which occur are at:

3600 to 2400 cm-l. Increase in intensity and broadening

of the band attributed to formation and hydrogen bonding of hydroxyl, hyd r ope r oxi.de and carboxyl groups.

-1

1746 ern . Broadening of the bond probably due to

formation of carbonyl products such as ketone s, carboxylic acids and aldehyde s ,

-1

1635 ern . Disappearance of shoulder on exposure. Band

probably due to double bond.

1450 to 725 cm -1. General increase in absorption

attributed to carboxylic acids, alcohols and ethers.

980 cm -1. Absorption by a mixture of isolated (967 ern -1)

and conjugated (988 cm- l) trans double bonds. Decrease

in absorption due to destruction of these bonds.

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7

-To rna k e the intensity results of the bands a rne na.b Ie to c orrrpa ris on

a.rriorig fi l rn s of different thicknesses and also to allow for thickness

changes of the fil rn in course of exposure, each absorbance value was

corrected by referring to that of the corresponding rne thyle n e group at

1460 CITl- l which is a function of thickness. This is possible because

the rne thylerie group is relatively stable to oxidation and rnu c h of the

population of the f il rn is due to this group so that even if SOITle of it is

lost during degradation, absorption would prima r ily depend upon fil ITl

thickness (12). The standard thickness itself was set at 25 ｾ . The

baseline rne thod (9) was e rnp.lo ye d to d ete r rnine absorbance of the bands.

Changes with fi Irn exposure in absorbance of ｢｡ｮ､ｾ at 1635 and 980 CITl- l

are illustrated in Figures 6 and 7

The band 3600 to 2400 CITl -1, a c ornpo s ite and con sidered as one -1

for s irnplicity , is very broad and subtends still another band at 2900 CITl

attributed to rne thy.lerie stretching rn od e , On f'i l m exposure the fo r m e r

band p rirna ri.Iy broadens and changes in intensity. These rriay be gauged

with the concept of half-band width of the band, i , e., band width at half

the absorbance of the band. The effect of the interfering methyIen e band,

however, mu st be accounted for. Fortunately this band, like that of

1460 CITl- l has been found to be essentially a function of thickness only.

Thus appropriate corrections can be rria.d e , The changes in corrected

apparent half-band width are given in Figure 8. The increases in apparent

half-band width for 1740 CITl- l band are illustrated in Figure 9.

Analysis of ultraviolet spectra of filITl

The changes in absorbance of f iIrn s at 230 and 270 ｉｔｬｾ due to

two and three conjugated double bonds, respectively, on exposure are given in Figures 10 and 11.

(c) Inte rpretation of Re sults

To aid in the interpretation of results the present general knowledge

pertaining to degradation will be su mrnariz e d , When linseed oil is exposed

to oxygen it oxidizes to fo r rn hydroperoxides at carbons adjacent to the

double carbon to carbon bonds. The products rriay in turn c ornbi.ne with

the unreacted esters to fo r rn d irne r s and poIyrne r s with perhaps peroxide

or ether linkages and solidify, or the hydroperoxides ITlay initiate chain

reactions to split oil and poly me r s , On exposure to oxygen and uv

radiation the po.lyrne r s ITlay further cross -Li.nk and gradually f'o r rn brittle f'i lrn s or rna y break down producing, a rnon g others, ketones and alcohols.

Thus fo r rriation , n onc fo r rna.tion , and deterioration of f'i l rn take place

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8

-Interest here is primarily in reactions that contribute to the breakdown of the solidified film and to a lesser extent the non-formation

of the film. The problem here then is to pick out such re actions from

those of beneficial film formation and analyze them.

Since the test exposures were unavoidably interrupted for analysis for relatively long periods and the films exposed to air, the films may have undergone retrograde and other extraneous changes. The results, therefore, were interpreted with some :r:eserve.

(i) The film is oxidized by the environmental gaseous

oxygen in the production of carbon dioxide. The rate

of evolution of carbon dioxide gradually falls and is promoted by uv radiation.

(ii) Evolution of carbon monoxide cease s early in the

exposure period. Amount of gas produced is about

25 per cent of that of carbon dioxide and is aided by oxygen and uv ,

(iii) In the film, hydroperoxide sandi or hydroxyls and carboxylic acids are formed as re action products in all case s and the over-all rate apparently gradually

decreased with time. The uv radiation promoted an

increase in the rates of the reactions. Oxygen and

water vapour did not seem to alter the rates

significantly. The idle - sitting period in air may

have influenced the re su lt s , The unusual band

broadening sugge sts hydrogen bonding of the hydroxyl with the neighbouring carbonyl group.

(iv) Carbonyl compounds are also produced in all case s,

the rate apparently falling with time. The uv

radiation hastens the reactions and oxygen seems to aid in the generation.

(v) Trans double bondings are gradually destroyed in

all cases, the rate being promoted by uv radiation. Similar response of the 1635 cm- l band due to double bonding suggests that destruction is mostly by loss of double bonding rather than by

trans-formation to cis isomer. Oxygen and water vapour

did not seem to affect the rate to any appreciable

extent. Here again, idle - sitting time in air

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9

-(vi) In absence of uv radiation, double bonds undergo further conjugation in different

atmosphere s , The uv radiation in the pre sence

of oxygen destroys conjugation presumably by p'r ornot.ing the reaction to proceed beyond conjugation and then to destruction.

(d) Conclusions

Upon drying in air, linseed oil film formed hydroxyls and/or

hydroperoxides and/ or carboxylic acids as well as carbonyl compounds

such as ketones and aldehydes. The original isolated trans bonds were

converted to conjugated trans bonds. On aging and exposure to oxygen

and/ or ultraviolet radiation am/ or water vapour more of the same products

were formed but at different rate s . Trans bondings were gradually

destroyed. Ultraviolet radiation promoted the change s in film composition

presumably by the absorption of radiation by ketones. Oxygen and water

vapour generally aided the reactions. The results for analyses between

test-exposures were not clear -cut probably because of relatively long exposure of the films to air, resulting in contamination of the reactions. Thus reactions during drying, presumably film formation, non-formation and deterioration continued in the dried film on test-exposure but at

different rates. The principal volatile products evolved were carbon

dioxide and carbon monoxide. Volatiles with a mass of 58, hydrogen, and

probably water vapour were also formed. Evolution of carbon oxides and

formation of carbonyls suggest carbon-carbon scission reactions which may lead to eventual breakdown of the film.

The volatiles evolved and the functional groups involved in the film were similar to those obtained by Crecelius (3) using a stronger and broader spectrum source of ultraviolet radiation.

Changes in film composition seem to occur most rapidly in the early stages of exposure to ultraviolet radiation when pre sumably the

mobility of the molecules is greatest. Also the early reactions could

determine to a large extent the later deterioration processes. Therefore

next stage of this inve stigation was concentrated in this area with

conditions more closely controlled and with improved and faster methods of analysis to obtain more detailed knowledge of the deterioration reactions.

2. TRlLINOLEIN FILM

Following the preliminary re sults on the combined film formation and deterioration reactions in dried linseed oil film, and with experience of the expe rimental technique s, a detailed study of the chemical kinetic s of trilinolein film in the early stages of exposure was initiated.

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lO

-(a) Procedure

Selection of film material

In order to make the analytical results more amenable to

interpretation a simpler film system was sought to replace linseed oil, a complex mixture of esters of seven component fatty acids. It was considered that:

(a) The primary active centre s for drying of linseed oil are the double bonds (13). Hence it follows that the reactivity of the oil for film formation is determined by the concentration of the se bonds. Linseed oil consists mainly of triglycerides of three, two, and one_double-bonded acids, which are linolenic, linoleic and oleic acids, respectively. The individual esters may be pure or mixed. Thus, esters with (2 x 3

=

6)

six double bonds should represent the average react-ivity of the components in oil.

(b) The composition of raw linseed oil based on the random pattern of distribution of components (14) in terms of esters with the same number of double bonds is given in Table II.

Now compounds of mixed acids are difficult to obtain in the pure state as compared to those of one acid, in this case those with seven and five double bonds. Thus, compounds with six double bonds are favoured

here also. Glyceryl trilinoleate and glyceryl- monolinolenate (3), - monolinolea: (2), - monoleate (1) were considered. Since glyceryl trIl.Inole at e or trilinolein

could be obtained in a purer state it was chosen as the film material. Special apparatus

For this detailed study closer control of the variables and conditions was sought. Therefore, a controlled-atmosphere box and exposure -infra-red

cells, among others, were fabricated and employed. (i) Controlled-atmosphere box

To minimi ze premature deterioration of trilinolein by oxygen prior to film preparation, an inert atmosphere chamber was desired in whic'h to prepare solut ions., For this a controlled-atmosphere box wa s designed and

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•

11

-constructed of lucite as shown in Figure 12 in which necessary manipulations could be carried out in dry nitrogen free of oxygen.

In operation, the main chamber (127 Htres) and an auxiliary transfer chamber (12 Htres) were purged with certified high purity dry

nitrogen (02 max. 20 ppm, H20

<

10 ppm) until the oxygen content in

the effluent. as monitored with a Beckman Oxygen Analyzer. fell to

0.00 per cent. Then objects. some of which were flushed out with nitrogen

beforehand, were introduced into the transfer chamber. purged of oxygen.

then transferred into the main chamber. Gas valve s were closed to

prevent subsequent suction of air into the box and solutions were pre pared

gravimetrically. To prevent significant diffusion of oxygen into the

system during manipulations. mainly through rubber gloves. the box

was repurged in the middle of operations. The oxygen content increased

typically from 0.00 to 0.2 per cent after use.

The box was constructed of O. 25-in. lucite sections press-sealed

with the aid of chloroform as solvent. Ports and the front window were

made of O. 37 -in. lucite; the latter was removable and sealed with a

0.030-in. rubber gasket and wing nuts. Neoprene gloves were used and

gloves and ports were sealed with O. 25-in. "0" rings and O. 50-in. rubber

tubings. respectively. Hollow gas inlet cylinders with O. 015-in. diameter

holes sp aced 2 in. apart were used to facilitate nitrogen gas distribution. The main chamber required 5.5 volumes of nitrogen at 3.6 litres/min to

lower the oxygen content from 20.7 to 0.01 per cent. Plumbing was of

0.25-in. copper tubing and vacuum-pressure valves.

(ii) Exposure -infra-red cell

For the present kinetic study. rapid and broader spectrum methods

of analysis were required with minimum of system disturbance. Therefore

the infra-red technique was chosen for gas as well as for film analyse s so that water and any organic vapour s could be analyzed in addition to

carbon dioxide and carbon monoxide. Hydrogen could not be determined

s irice it possesses no infra-red band but, because the relative amount evolved with linseed oil film was previously found to be very small. and probably small here too. this limitation was not considered serious.

Thus number of exposure -infra-red cells as illustrated in Figure 13

was designed and fabricated. In use. the film in an appropriate atmosphere

is exposed to radiation at position 1. At suitable intervals the cell is

removed and placed in the infra-red spectrophotometer and with the aid of ordinate scale expansion (20X) the spectrum of the gas is determined for

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pz

ＭＭＭｾＭｾＭＭＭｾ

12

-are scanned at IX. To obtain the spectrum of the film only, the gas

spectrum is next run at IX at position 1 and subtracted from the combined spectrum.

For exposure in a dry atmosphere, sodium chloride windows were

usually used and were sealed with glyptal. For humid atmosphere

water-insoluble magnesium fluoride windows were employed. To maintain

the original dry atmosphere the finger was kept cooled with liquid nitrogen.

Spectra from 10,000 to 650 cm -1 were taken on a Perkin-Elmer Model 221 infra-red spectrophotometer with sodium chloride prism optics.

(iii) Ultraviolet radiation

For these determinations radiations at two wavelengths were

°

employe d , one at 3130 A to simulate short uv . fr om the sun and the other

°

at 3660 A to simulate long uv , As before, intensities of these components

were comparable to those of the noon-day sun. A Hanovia lamp in

conjunction with filter 6527 B and heat-deflecting Vycor 6527 F was used.

Study of degradation

An ampoule containing 5 g of trilinolein (97 per cent

+ )

sealed in nitrogen and obtained from Hormel Foundation, Austin,

Minnesota, was opened in the controlled-atmosphere box in the absence of oxygen and a solution containing 0.030 per cent lead and 0 .025 per cent

cobalt as octoate s was prepared gravimetrically. Drier solutions were

previously deoxygenated by bubbling nitrogen through them. About 1 ml

portions of the solution were then dispensed in gas -tight nitrogen-filled vaccine bottles and stored at -20°C to minimize deterioration.

Prior to initial film preparation trilinolein solutions were aged at room temperature for about 48 hr to allow driers to reach full

effectiveness (15). Then about 0.1 ml portions of the solution per panel

were removed with a syringe and free films 251-1 in thickness were prepared

and mounted on pyrex frames as for linseed oil films. Films relatively

free of imperfections were selected for study to minimize premature rupture.

Cells containing one film each were evacuated and filled with appropriate atmosphere at slightly under atmospheric pre ssure,

i. e. 69 cm of me rcury. This time, dry oxygen, water vapour saturated

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13

-tank oxygen (99.7 per cent) through dry ice-acetone trap. Water vapour

saturated oxygen was generated as before. High purity certified dry

nitrogen was used without further purification.

Initial spectra of the films and the atmospheres were taken. Then the films were subjected to exposure and at appropriate intervals

further spectra were taken for analysis. Non-irradiated films were

air-thermostatted at 25

+

lOC under normal indoor illumination. The

irradiated films were maintained at 27.!.. lOC, higher due to radiation

heating. Exposures were usually run in duplicates. Films were followed

up to 120 and 1200 hr for radiation exposed and unexposed films,

respectively. The former period was short because of film rupture.

Since the primary volatile products may subsequently undergo further

chemical changes, auxiliary check runs were made. Finally, calibration

curves were determined for each volatile product and the analytical results were interpreted in terms of chemical changes in the film.

(b) Results and Discussion

Analysis of volatile products

The organic volatile product with an apparent mass of 58 was finally identified from its infra-red spectrum as formic acid vapour

consisting of a mixture of monomer and dimer. Bands at 1770 and

1122 cm- l were utilized for quantitative analysis. Carbon dioxide,

carbon monoxide, and water vapour were analyzed by their bands at

2300, 2250 and 1550 crnr I , respectively.

Calibration curve s for formic acid vapour were determined by

using 98 per cent formic acid. Those of carbon dioxide and carbon

monoxide were obtained by employing gas mixture G-7. Air of known

relative humidity was mixed with dry nitrogen to draw up the water vapour curve.

The kinetic results for formic acid vapour, carbon dioxide, carbon monoxide, and water vapour are shown in Figures 14,15,16, and 17,

respectively. Time is plotted logarithmically to allow presentation of

data more commensurate with rate and also for economy of space. The

results for formic acid vapour are uncorrected for apparent subsequent

decomposition of the acid in the test condition. For example, in oxygen

atmosphere under uv radiation, formic acid vapour concentration

decreased as a first order reaction with specific reaction rate constant

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14

-Film analysis

As an illustration of changes observed, the infra-red spectrum for the trilinolein oil and working spectra for dried film, before and

after exposure to radiation, and dry oxygen for 85 hr, and the corre sponding

atmospheres at IX are given in Figure 18. Comparison of the spectra

with the corre sponding one s for linseed oil shows that they are the same

except for the bands for the liquids in the 980 cm- l region. This

similarity strongly suggests similar film reactions. To aid in the

interpretation of such spectra chemical analytical results for tack-free trilinolein film 31 fl. in thicknes s and dried for 13 hr are given in Table III (l6).

(i) 3400 cm- l Band

Increase in band intensity and apparent half-band width and also the apparent frequency shift of the absorption maximum at 3400 cm- l

were observed. Corre sponding kinetic s are illustrated in Figure s 19 and

20. Shifts were found to be characteristic of the exposure.

The increase in absorption at the initial stage s of exposure is probably due to formation of more hydroperoxide (3450 cm -1) (Table III),

carboxylic acids and alcohols (Table Ill). Broadening and shift of the

band peak are probably caused by the increase in concentration and hence

association of the monomers to polymers by hydrogen bonding (17). Thus

formation of formic and other carboxylic acids brought about increase in band intensity and as the acid concentration increased the monomer (3500 cm- l) reverted to dimer (3150 cm- l) causing broadening and shift

in band peak. The corresponding general increase in carbonyl band

absorption at 1200-1300 cm- l tends to confirm this. Formation of

monohydric and even dihydric alcohols in any significant amount would also re sult in rrionorrie r hydrogen bonding with consequent shift in

absorption band as for acids. Here the band peaks are slightly higher,

3635 cm- l for monomer, 3500 cm- l for polymer (17,18,19). The mixture

of acid and alcohol hydrogen bondings could then account for the observed peak at 3225 cm- l•

(ii) 1740 cm- l Band

The apparent half-band width of this carboxyl band increased on

film exposure. The kinetics are given in Figure 21. The 1740 cm- l

band initially is mostly due to carboxyl group of the ester as for the liquid

in Figure 18. As the film dries and undergoes deterioration the band peak

shifts to 1725 ｣ｭｾｬ and broadens owing to formation of carboxylic acids

(1715-1690 cm- l), ketones (1730-1600 cm-l)(Table III) and aldehydes

(20)

t R.

+ .

OOH (I)

15

-(iii) 980 cm- l Band

Band decreased in intensity and in some cases disappeared on

film exposure. This band may be attributed to a mixture of original

isolated trans-trans (967 cm- l), and conjugated trans-trans (988 cm- l) bonds formed on hydroperoxidation, as shown in Figure 18, which were

gradually destroyed (Table III). The kinetics are illustrated in Figure

zz.

(c) Interpretation of Results

Interest here is primarily in the deterioration reactions.

Nevertheless, since other reactions are also concurrently taking place in the film and some are even intimately connected with the degradation

processes, the ove-rc al.l reactions will be studied and interpreted to gain

insight into the degradation reactions. Reactions will be cla s sified into

film formation, non-formation and deterioration reactions, and probable

mechanisms employing free radicals will be suggested. For convenience,

reaction equations are given first. Thus:

(i) Initiation (5)

*

RH

+

0z ｾ

ZROOH (metal ､ｲｩ･ｲｾ RO.

+

RO

Z'

+

HZO (Z) (Hydroperoxide) (ii) Propagation (5)

...

( 3) ROOH

+

R.

_.

.

₍₄₎ CH_3(CHZ)4 - CH

=

CH - CH - CH

=

CH (CH) -COOCH Z 7

I

Z CH 3(CHZ)4 - CH

=

CH - CH

_{z -}

CH

=

CH (CH Z)7 - COjCH CH 3(CH

_z)

4 - CH

=

CH - CH

_{z -}

CH

=

CH( CH Z)7 - COOCH

z

t

= free radical isolated trans trans glycery trilinoleate radical !l -ＧＢｾｾＢＢｾｾ

(21)

16

-(iii) Polymerization and cross-linking (4, ZO)

RO

Z'

+

R. ｾ ROOR 0 0 0 • • 0 " (5)

RO.

+

R. ｾ ROR

ROOH

+

RH ｾ ROR

+

HZO

ｾｒｉｏｏｈ

+

R'H ｾ RIO RI

+

H 0 Z

(6)

(7) (8) (9)

RIO Zo

+

R'C

=

C-C

=

C-RI ｾ RO RICCC

=

CRI (10)

Z •

(iv) Non-formation or cleavage (z r)

=

S .. (11)

+

CH

3(CHZ)4 CH

=

CH-CH

=

CH-CHO

(Z,4-decadienal)

hr

S

+

0z ---i HCOOH

+

COZ

+

RCOOH

+

HZO ..

0...

u

z)

(formic acid) (acid)

R"CH(OOH) Rill ---t R"COR"I

+

HZO ｾ R"CO.

+

R".I ( 13)

...

(22)

pi

17

-(v) Depolym.erization ＨｚｾＬ 23)

RICHZO.

+

0z ｾ RI.

+

HCOOH

RICHZCOR

ｾ

RtCOCOR

RICOCOR

ｾ

RICO.

+

RCO

(14) (15) (16) (17) RtCO. _ｾ R",

+

CO (18) RtCO.

+

0z RO.

(19)

RICH(OOH)R ｾ RICHO

+

(aldehyde) ROH (alcohol) ( ZO)

(i) When trilinolein film., dried in air for 17 hr is placed in an inert

oxygen -free atm.osphere, in absence of te st uv radiation, principally

water vapour is evolved. Rate of evolution falls to zero rather rapidly,

however, indicating initiation (Eq. Z) and m.ostly polym.erization and

eros s -linking reactions (Eq. 8, 9). Sm.all am.ount s of form.ic acid and

carbon dioxide are also produced probably from. residue cleavage

(Eq. 11, i

z)

and depolym.erization reactions (Eq. 15, 19,

z

i). In the

film. further form.ation of hydroperoxide (Eq. 4), hydroxyl (Eq. ZO) and

carboxyl (Eq. i

z.

15, Zl) products is term.inated. Trans double bondings

are very slowly lost (Eq. 10). Thus, in short, on exclusion of gaseous

oxygen the reactions in the film., principally radical form.ation and probably polym.erization and cross-linking, that is drying, proceeded until the oxygen was exhausted; then they term.inated.

(ii) The film. on exposure to uv radiation but still in inert atm.osphere

evolved greater quantities of form.ic acid vapour and sm.all am.ounts of

carbon dioxide and carbon m.onoxide. These volatiles were probably

produced by photolytic decom.position of the carbonyl com.pounds, ketone s

and aldehydes (Eq. i

z.

!6,

17. 18,

z

i), by radiations at 3130

A

and to

a lesser extent at 3660 A. Thus chain-scission increased. In the film.

(23)

ｾＭＭＭＭＭｾＭＭｾＭＭＭＭＭＭＭｾＭＭ］ＭＭＭＭＭＭＭＭＭＭＢ

18

-but none for carbonyl. Trans double bondings were destroyed at a greater rate. Thus, radiation in absence of oxygen increased deterioration

presumably by depolymerization and cleavage.

(iii) On exposure of film to oxygen, but in absence of test uv radiation, the production of water vapour increased. Formic acid and carbon

oxides were evolved at a greater rate and quantity indicating acceleration of chain-scission reactions. In the film more hydroperoxides and/or hydroxyls and/or carboxylic acids were generated. The 3400 cm- l band peak shifted to a final position at 3225 cm- l signifying increased

concentration of carboxylic acids and alcohols to form hydrogen bonded polymers. Carbonyl concentration increased. Trans bondings were rapidly de stroyed. This, coupled with the fact that CIS bonds were absent, led to the conclusion that all double bonds were lost so that further film formation through unsaturated hydroperoxide terminated. Thus it is obvious that environmental oxygen is required for further polymerization, cleavage and increased depolymerization of the film after initial drying and solidification of trilinolein.

(iv) The presence of uv radiation in addition to dry oxygen encouraged the formation of the products. As trilinolein oil through drying assumed a more viscous cros s -linked structure, further polymerization reaction, which involves linking of two large molecules, is retarded because of lower mobility of the molecules, in favour of cleavage of the molecules. Thus, more carbon oxides (Eq. 18, 19) were produced presumably through the absorption of uv radiation by the carbonyls. Increased formation of water vapour could signify greater depolymerization

reaction (Eq. 21). Increase in changes in 3400 cm- l band probably reflects the production of more carboxylic acids (Eq. 11, 12, 21). The destruction of trans bondings was even more rapid (Eq. 10). Thus uv radiation probably accelerated the cleavage and depolymerization reactions.

(v) The presence of water vapour in high concentration in oxygen decreased the apparent rate of evolution of formic acid and carbon oxides as well as formation of non-volatile s in the film. The 3400 ern -1 band peak shifted only slightly, to 3375 cm- l. The presence of water vapour probably shifted the reaction equilibrium to the left through mas s action and retarded the reactions.

The film became soft and tacky presumably through sorption of water vapour. Now in the process of oxidative polymerization and deterioration of the film, carboxyl, hydroxyl and other groups are formed, among others. These are polar substances and sorb water vapour from the surroundings. As a result, the film imbibes water

(24)

19

-and undergoes swelling. In turn the polar substances dissolve in

water so that the film becomes tacky and weakens mechanically

and eventually rupture s , Thus the pre sence of high concentration

of water vapour retarded the film reactions and mechanically weakened the film to rupture.

(vi) Exposure of the film to uv radiation in the presence of highly

humidif ied oxygen encouraged the rate of evolution of formic acid

and carbon oxide s and the formation of non-volatile alcohols, carboxylic

acids, and other carbonyl compounds. The 3400 cm- l band peak shifted

more, to 3330 cm- l. The rate of formation of the products was generally

comparable or slightly lower than with uv and dry oxygen. Film became

soft and tacky and ruptured after about 100 hr of exposure to radiation. Thus, probably more cleavage and depolymerization reactions took place with possibly more cross-linking than in the absence of radiation.

(d) Conclusions

(i) Similarity in infra -red spectra of trilinolein with respect to

those of linseed oil, both as liquid and as dried film, before, during,

and after exposure signifies the occurrence of similar gross chemical changes and supports the selection of trilinolein as a suitable simpler "replacement" for linseed oil, which is a complex mixture.

(ii) Trilinolein film dried for 17 hr and subsequently subjected to

exposure to oxygen, ultraviolet radiation and water vapour underwent chemical changes, in the early stages, resulting in formation of hydroperoxides, hydroxyls, carboxylic acids, ketones and probably

aldehydes, and destruction of trans-trans double bondings. Volatiles

were also evolved in the form of carbon dioxide, formic acid, carbon

monoxide and water vapour. The formation of these products was

probably due to reactions involving formation, non-formation and deterioration of polymer film.

(iii) Concerning the degradation of the film, the increase in apparent

half -band width of the carbonyl band gives a measure of the non-volatile ketones, carboxylic acids and probably aldehydes formed when the

molecules undergo internal body scissions and break off relatively large

molecules. Evolution of the volatile carbon compounds is probably

mostly from the chain ends and as such give s the measure of the end

chain-scission reactions. These reactions combined then give the

measure of the non-formation and deterioration of the polymer s .

Comparison of the rates of formation of the above products among different exposure conditions provides an assessment of the degrading quality

(25)

!'

20

-(a) Oxygen and uv

(b) Oxygen, water vapour (high c on c . ) and uv (c) Oxygen

(d) Oxygen and water vapour (high c onc , ) (e) Nitrogen and uv

(f) Nitrogen.

(iv) Oxygen is required in the deterioration of the film. Ultraviolet radiation promoted the degradation of the film by cleavage and

depolymerization, presumably through absorption of the radiation by the carbonyl compounds. Water vapour effectively slightly decreased the degradation of the film as far as chain scission is concerned. It made the film swell, however, and become tacky and lose its mechanical

strength and caused rupture.

SUGGESTIONS FOR FURTHER WORK

1. Hydroperoxide gives a characteristic band in the near-infra-red region free from other interfering bands as at 3450 cm- l. This could profitably be employed to determine hydroperoxide concentration and thus elucidate its role in film deterioration process.

2. Individual products of film reaction could be identified by Il'Eans

of paper or thin film chromatography to clarify further the mechanism of film deterioration.

3. Effects of different temperatures, pigments and additives such as ultraviolet absorbers on film degradation could be studied by the present technique.

4. Effects of long-term exposure on trilinolein film both indoors and outdoors could be studied where deterioration reactions of the polymer film presumably predominates.

5. The present technique may profitably be employed to study the degradation of other clear coatings.

(26)

' '

21

-REFERENCES

1.

A. C. Elm, Deterioration of dried oil films, Ind. Eng. Chern.

!!'

319- 324 (1949).

2. S. B. Crecelius, R. E. Kagarise and A. L. Alexander, Drying oil oxidation mechanism, film formation, and degradation, Ind. Eng. Chern.

!2.,

1643-1649 (1955). 3. S. B. Crecelius and L. L. Alexander, Mechanism of linseed

oil film degradation under ultraviolet irradiation, NRL Report PB 121330, Naval Research Laboratory,

Washington, D.C. (1956).

4. C.D. Miller, Degradation of drying oil films, J.Am. Oil Chemists' Soc. 36, 596-600 (1959).

5. J. C. Cowan, After dry, what? A general survey, Official Digest 34, 561-574 (1962).

6. R. E. Bedford, Measurement of radiant energy emitted by a mercury quartz lamp, NRG Report APHSSP-823,

National Research Council of Canada, Ottawa (1959). 7. E. Pettit, Spectral energy-curve of the sun in the ultraviolet,

Astrophys. J. 91, 159-185 (1940).

8. F. L. Browne, Understanding the mechanisms of deterioration of house paint, Forest Prod. J.

1,

417-427 (1959).

9. Chicago Society for Paint Technology, Infrared Spectroscopy. Its use as an analytical tool in the field of paints and coatings, Official Digest 33, March, Part 2 (1961). 10.

11.

C. R. Bragdon, Editor, Film formation, film properties and film deterioration, Interscience Publishers, Inc. t New

York (1958), p. 143.

A.I. M. Keulemans, Gas Chromatography, Reinhold Publishing Corporation, New York (1959), 234 pp.

12. Reference 10, p. 124. 13. Reference 10, p. 347.

(27)

22

-14. H. J. Dutton and J. A. Cannon, Glyceride structure of

vegetable oils by countercurrent distribution.

1. Linseed oil, J. Am. Oil Chemists' Soc.

12.,

46-49 (1956).

15. Reference 10, p.35.

16. J. R. Chipault and E. McMeans, Studies on oxidized

films of trilinolein and trilinolenin, Official Dige st

ｾＬ 548-553 (1954).

17. G. C. Pimentel and A. L. McClellan, The hydrogen bond,

W.H. Freeman and company, San Francisco (1960), 475 pp.

18. R.F. Blanks and J.M. Prausnitz, Infrared studies of

hydrogen bonding in isopropanol and in mixtures of isopropanol with poly (m-butyl methacrylate) and with

poly(propylene oxide), J. Chern. Phys. 38, 1500 -1504

(1963).

19. U. Liddel and E.D. Becker, Infrared spectroscopic studies

of hydrogen bonding in methanol, ethanol, and tert-butanol, Spectrochimica Acta 1..,2, 70 -84 (1957).

20. F. R. Mayo, Some new ideas on oxidation, Ind. Eng. Chern.

52, 614-618 (1960).

21. H. T. Badings, Isolation and identification of carbonyl

compounds formed by autoxidation of ammonium

linoleate, J. Am. Oil Chemists' Soc. 36, 648-650 (1959).

22. A. Finkelstein and W. A. Noyes, Jr. , The reactions of

radicals from diethyl ketone with oxygen. Part 1, Discussions, Faraday Soc. No. 14, 76-84 (1953).

23. J. E. Guillet and R. G. W. Norrish, Photolysis of poly methyl

vinyl ketone: Formation of block polymers, Nature 173, 625- 627 (19 54) •

(28)

ｾＺＺＢ

TABLE I

ANAL YSIS OF VOLA TILE PRODUC TS OF DEGRADATION OF LINSEED OIL FILMS

Exp osure Agents _Gas _Mole,

_%

Oxygen, water vapour (high con c , ) _COZ

_7.0

and uv HZ

0.5

NZ+CO

0.8

CH 4 O.OZ C ZH6

0.08

others O. 1 Oxygen and uv

_8.3

0.7

(29)

TABLE II

LINSEED OIL COMPOSITION IN TERMS OF ESTERS WITH SAME NUMBER OF 00 UBLE BONDS

No. of Double Bonds

7

6

5

9

Per Cent

23

19

15 14

(30)

TABLE III

*

COMPOSITION OF TACK-FREE TRILINOLEIN

FILM DRIED FOR 13 HOURS+

Functional Groups _{Dried Film} _{Or iginal Oil}

(Theory)

Wt. or Number 10- 6 Mole

i. Peroxidex ₂₂ ₀

2. Hydroxyl ₂₈ ₀

3.

Alpha glycolic group 10 0

4. Unsaturated double bonds ₃₉ ₈₄

5. Carbonyl (Ketonic. aldehydic) 4-8 0

*

For l4X10 -6 mole equivalent in monomeric tril in ol e in , By analysis of reduced fatty acids.

+

Dried at 21°C and 61 per cent relative humidity. Drier content 0.025 per cent Co and 0.03 per cent Pb.

x

(31)

"

1·00

r·t'·

LINSE.EV OIL FILMS

...- - - COLD ｔｾａｐ

FIGURE I

(32)

SIIUTT£.!j

FILMS

FIGURE

2 FI LM HOLDER FOR UV ANALYSI S WITH A

BECKMAN DU SPECTROPHOTOMETER

(33)

ｾ 15.0 ｾ o :E o 0::: U

.

-UJ :: 10.0 l --c ｾｾ :E ｾ u c UJ > ｾ o 5.0 > UJ VI -c <.:l 0.0 l£G£ND

0 - 0 o.ygen and uv.

ｏｾｹｧ･ｮ

6----6 Oxygen, Water Vapour tHighCone, I and uv.

A_ - - - _6 Oxygen and WaterVapour tHigh cenc.r D-o-o-o-O Nitrogen, Water vacur(HighCone.I and uv.

____l{_.

Nitrogen and Water Vapour (High Cone.I

ｔｩｭ･ｬｾｾｦｯｲａｮｬｬｬｹｳＮ･ｳ

0··· ···0

1::./ !Y'I::. /

_---A

... A . . • . . . • . . .

-

--0···· ｾ｟ＭＭ

:

i

A • • • • • • • • • • • - _ .

I

_..-

.---

_0-0

I

_.k-::J..

...

--

I

l

•

J

• • _ 0 -

i-=

ｾＭｾﾷﾷﾷﾷﾷﾷＺＺｉＺﾷﾷＺﾷﾷﾷＢＭＺＭＭｉﾷ

X-.' • • • . • . • • • • • • •_X

.

ﾷｯＭﾰＺｴＭｾ］ｾｾｄﾷ

. . . 1::.' . ll' ｬＨＢＧＭｾ 0-0=0::. ｏ］ｏＧＺＢ［ｏＢＧＺＢｏｾｯＧＭ ::Z:X-X

o

10 20 30 40 50 60 70 80 90 100 110 120

CUMULATIVE AGING AND ｔｅｓｔＭｾｘｐｏｓｕｒｅ PERIOD, DAYS

FIGURE 3

(34)

In ｾＳＮＰ o :E o e::: u

0 - 0 O.ygen anduv.

Oxygen

6 - -- -A Oxygen,Water Vapour (HighCone. 1and uv.

Oxygen andWater Vapour IHigh Cone. ) 0-0-0-0-0 Nitrogen, water V.,ur 'High Cone., Ind uv.

NitrDql!ln Ind water Vapour lHigh Cone. , ••••••••• Time lapselor Analyses

0·· ···· .. · · · 0 - - 0 0 10

o

e e - _ e e __ / ' I Ｎｾ :': ...• 0o-o-o-(} ...••••••••••..••0 - 0 - 0 - 0 - 0 - 0 - 0 - 0 - 0 - 0

I

....

.

...•

---

-

•...•

---

-

----

.

...__...

｟ＭｾｾｾｸＺＮＺＮ

-=---:

ｾｾ

...

.I. ...•

-x-x-xLx•...

J...•

Jx-x-x-Lx-x-xLJ

20 30 40 50 60 70 III 90 100 110 120

CUMULATIVE AGING AND TEST-EXPOSURE PERIOD, DAYS

0.0 LI.J >

i=

2.0

«

_...

::::I :E ::::I U C LI.J >

...

01.0 > LI.J In

«

ｾ FIGURE 4

(35)

"-f1ＳＱＴＭＸＭｾ > ｾ II I,

I'

ＧＱｉｉｮｬｬｩｬｩｬｬＢｉﾷｬｩｬｬＢＧｩｬｾＺﾷｾｮｾﾷﾷﾷｉＺｾ

I

I'

' 1 ' 1

'I

I

. i!

I i i

li!l I

till)1jlii1Th-h..ｴＮＫＭｫｾＱＱＱｉｩｬｾＡｉｉＮｷｾＮｩｩｬＬＺｉｉ｛ｉ｛ＧｬｩＡｩＡ i , 1 ,

.!".

Ｏ［ＧｾＬＡ I ｾ I ! O' 00 0:0

C. Dried linseed Oil Film After Exposure for 172 hr.

.>

Ilrmnmffi

0.0

I

B. Dried linseed Oil Film Before Exposure.

'ch1_l ｾｬｖＧ

i

I

II

A. li nseed Oi I. FIGURE 5

(36)

0 - 0 Oll'ygen and uv.

. - - - . Oxygen

6 - - - -6 Oxygen, Willer VapourtHigh Cone.) and uv. A- - - -_.6. Olygen and Water Vapour(HighConeI 0-':'-0-0 - 0 _{ｎｩｬｲｾｮＮ} _{Waler vaour (High Cent. I and}_U'I

ＮＭＮＭｾＭＮ Nitrogen and WaterVapour(High Cone, I

••• •••••• Timeｬ｡ｰｾ･ for AnillY5es

6 I

I

10 0.040 0.030 0.010

,.

Ｇｾ

_,

｜ｾ

ｾ

\ '

y

•

Ｌｾ

y

"

_X...

'

_,

ｾ

_,0

y

X... \ I X 0 -,, \1 , X...lC " ｾ

'

...\. ｾ 1 Ｎｾ , 6 ...• 6

'''X

<,

ｾ

\ '

...

X<, , ｾ _ _ .

""-...

...

""-1

ｾｾＮＮＮＮＮＮＮＮＮＮＮ

----,

.

ｾ

_-

--.

, ｾｸＧ ••••••••.•••••.0--'1;;;:0-0-0-0_0-0 0.000 L..-_....l...-_---l._ _

l__

...L.-_. . . ,. ,•••_ ••_ ••_ ••_ ••. ,_••. ,. ,

ｯＭＭＧｾｯＮ

J..

ｾ

•.••...1. .::::;.

ｾﾷｾｉＺＮＺＺﾷｨＱ

o

20 30 40 50 60 70 80 90 100 110 120

w U z

«

eo l:X: o VI 0.020 a:l

«

FIGURE 6 -I

(37)

ＭＭＢＭＭＭＭＭＭＭＭＭｾｩＧ

L[G[N D

0 - 0 Okygen and uv.

120

e • Okygen

6--- - I i ｏｾｹｱ･ｮＬ Water Vapour (HighConeI and uv Okyqen and Water Vapour(Hi9h Cone.I

n-e-e-e-u Nitrogen. Waterｖｾｵｲ IHi9hConeI and uv.

.---)(-. Nitrogen and WaterVlpOur IHi9h Cone,I ••••••••• TIme lapse forAnalyses

Ｇｾ

....

',

...

"",.<)"

'£!C..il· • ·· · · ...,...

1

...<,...

1\...

....

0,

,0,

ｾｾ £ •••••••••.A _

'\

_ｾｾＧ _ｾ

----..::::..

ｾＭＭＭＭ _ｾ

-.

0··· .0\0'0

0_0:1\

<,

1\

x

-A,

0_ 0 ...)( ＭｯＭｯ｟ｾｾ

o-

'O-"-7"---.-_l

20 30 40 50 60 70 80 90 100 110

I I

I

l:J.---l:J. \ \ l:J. l:J. I I

I

10 0.000

o

O. 150 0.050 UJ U Z -e co0.100 a:: o VI co -e FIGURE 7

(38)

120

e • ｏｬＨｾｮ

0 - 0 o.ygen itnd UY,

LEGEN D •

6----lJ. OIygen. Wlter VlpOur tHighConc.1 itIld uv. A- - - - -6 OJ:ygen and WaterVlpOur(HighCone. 1 O-o-C'--o-Q Nilroqen, Waler vaour(HighConc.landw.

... - . - . NHroqen Ifld Witter VlpOur tHigh Cone. ) ••••••••• Time lapse forAnitlyses

20 30 40 50 60 70 80 90 100 110

CUMULATI VE A GIN G AND TE ST- EX P0 SUR E PER I 0 D. DAY S

ｾ

I

/

li.... · .. li I I

I

10 o - - - -__- -__---,r---.----.----..,._ _--..,._ _--..,._ _--,- _ _--,- _ _--,- _ _--,----::.

x/I

ｸＯｾｏ

/,:;,:.:-..-,

...

'"

.'."

,

"'./

ｾ

• • • • • • • • • •ｾａ 0 0··· 'f' 0

p"

'Qo-o-o-o-o-o-I

I

_I

/

_{/ 0 , .}/0 • • • • • . • • • • • - - - -_{_} -:::..==-=--.-...,1 x .

if,."

__

D,. . . .

·i ... ·.... ·..

ｾＬＮ

" /

/

•...

...•

"

, x l / '

/1

.

'I /

o

700

400

I :E u ｾＧＶｯｯ t -o o z -e CO ｾＵｯｯ ....l -e ::J: FIGURE 8 - I

(39)

lEGEN 0 120 110

100

DAYS 6

I

,,

I

r:

,

I

ｯｾｯ O.yqen anduv.

. - - - . Olygen

6- --- 6 OIY9'!n, Water V'lIPJur (High Conc.! and uv .&- - - - -.& Oxygen and Wirier Vapour (High Cone.I O-('l-O-l-O Nilrogen. Waterｖｾｵｲ (High Cone.I anduv.

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