Document XzndE48G12B38M8n5N85j7OKg

P. o. * ..... n n .A_Jtaek*R Labar*t*rio*t 2*c. NGv *0 1957 959 Swelling of Paint Films in Water VIII. Swelling of Linseed Oil Paints in Water and Organic Liquids F. L. BROWNE Chemist, Forest Products laboratory,1 Forest Service, U. & Department of Agriculture Compares the swelling effect of water and five organic liquids marked with reference lines for meas on films of unbodied linseed oil and of five linseed oil paints. All of urement of length and width, and the oil and paint films absorb, swell, and lose soluble ingredients desskated over calcium chloride. The in the organic liquids in much the same manner as they do in water. films for tests in water and in mineral The order of increasing swelling power is nearly the same far ell spirits were 19 days old when im films, both before end after weathering artificially* mersed in the swelling liquid; those for ethyl alcohol and benzol were 22 r e v io u s p a p e r s in this series (1)* P have discussed the swelling of paint films and coatings in water. Of Ethyl tkafcoi Dioxin* Butyl alcohol Btaiol Miner*I spirits 6.790 1.635 course, water is the swelling liquid of chief practical interest, but comparison A few liquids swell wood more of water with other liquid swelling agents should throw further light on the mechanism of swelling. Concern than water does. They are formic add, compounds related to pyridine and moq>holine, and some amines. A pre with swelling by organic liquids for paint removers (2) was not an imme liminary test showed that morpholine swells white lead linseed oil paint diate object of this work. greatly, but makes a slimy film much too difficult to handle in the testing days old, and those for butyl alcohol and dioxane were 23 days old. Weathered films were made by spreading the paints on tinplate. They were allowed to dry for 10 days, and then exposed in a weatherometer to ultraviolet light from a darning carbon art with a Corex D glass filter and sprayed three times an hour with dis tilled water for 13 days. After die artificial weathering, tire films were stripped by amalgamation of fire tin, Swelling Liquids Liquids were chosen whose relative capacity for swelling wood has been given by Stamm (6) as follows: procedure, and it causes zinc oxide paint to disintegrate. Use of so highly add a substance as formic add was considered undesirable. Preliminary tests also showed that cut to size, marked, and desskated for testing- Swelling tests were made as fol lows: the length and width of the film between reference marks were Swelling rtltthre to w*ter dioxane and ethylene glycol mooobutyl measured with a traveling microscope. Witelirquid Pe1i0c0ent ether swell paint films markedly, bat The film was weighed first in air and Ethyl Alcohol Dioxane n-Buryi Alcohol 83 62 13.3 when die films are redried, much of the absorbed liquid is retained for a then under distilled water to obtain the volume by displacement. After the Bensol 0 Mineral spirits, which does not swell wood, was added to the list be cause of its common use as a paint thinner. The ethyl alcohol, butyl alco hol, and benzol were anhydrous, and of chemically pure grade. The dioxane was dehydrated ana freed from perox ide by treatment with metallic sodium and redistillation. The water was distilled. The density of distilled water at the temperature of the laboratory was con sidered to be 1.000, which is within the limits of accuracy required for the experiments. The specific graviy of the other swelling liquids was found by test to be: long time. The retained swelling liquid, however, can be removed by water left on the surface from the brief immersion had evaporated, the soaking the redried films in distilled water for three days and then redty ing them. film was submerged between two pieces of coatse-methed glass doth in 230 cubic centimeters of swelling Paint Films and Test Methods fluid in a crystallizing dish. The glass doth was weighted, and the dish was Free films wore made of unbod covered with a watch glass and sealed ied linseed oil containing a lead- to prevent evaporation of the swelling manganese paint drier, and of each of liquid. The sealed dish was then five linseed oil paints, all with a 30 placed in a water thermostat at 70 F. Kr cent pigment volume, as follows: sic carbonate white lead, paint L; for three days. ' After die film had soaked for three zinc oxide, paint Z; rutile titanium days, it was removed and immediately dioxide, paint T; white lead and zinc weighed under a fresh supply of die oxide, paint LZ,,; and titanium diox swelling liquid. The length and width ide ana zinc oxide, paint TZ,,. The between reference marks on the swol subscript is the parentage of zinc len film were measured with the film 1 Munuioed Wit., in coopera tion with the Unhrcrtity of Wiscomin. a Numbers in parentheses refer to literature cited. oxide in the total pigment volume. The paint films to be tested before weathering were spread on gummed sandwiched between glass microscope slides. The film was. then blotted quick!)' to remove excess swelling liq The Anther- Frederick L Browne received E. Chem. decree from Cornel) U., Ph.SX in colloid chemistry from U. of Wisconsin. He joined the Forest Products lab staff in 2918. helped develop casein glues for wood Airplane* of world War I. In *921-22. he w as a National Research Fellow At Wisconsin. Since 2929. Dr. Browne has edited the GooerAl *d Physical Chemistry section of Chemical Abstracts. paper by doctor blade .and suction plate. The linseed oil was spread by brushing. The films were allowed to dry for 10 days and were then stripped from the gummed paper, cut into spec imens \yi by 2% inches in size. uid from the surfaces, placed in a tared bottle, and weighed to determine the weight of the swollen film in air. A few films were found to be too fragile when swollen to be straight ened out between glass slides for the Reprinted from the August, 19J6, Forest Products Journal (Vol. VI, No. I), pages 512--318 Forest Products Research Society, p. O. Box 2010, University Station, Madison 5, Wisconsi No Glidden Document Exists For This Bates Number: GLD 038029 GLD 038029 TobU 2.--LIQUIDS ARRANGED IN THE ORDER OF THEIR VOLUMETRIC SWELLING Of WOOD AND OF UNWEA7HERED AND WEATHERED MIMS Of EACH KIND OF Oil OR PAINT TESTED. Materia) swollen Liquids* in order of lncreuinmttiDg, left to right Clear linseed oil___ Water Min. sp. White lead. ............ Water Mtn. ap. Titanium dioxide..,, Min. sp. Zinc oxide... Min. sp. Leadline.... Min. sp. Titanium-sine........ Min. sp. tfaweathered Films EtOH BuOH EtOH BuOH EtOH Water Benzol EtOH Benzol EtOH Water BuOH EtOH BuOH Benzol Pioxane Benzol Dtoxane BuOH Dioxane BuOH Water Dioxane Benzol Dioxane Benzol Water Dioxane Weathered Films Clear linseed oilWater Min. _ sp. Benzol EtOH BuOH White lead............ .. Water Min. ap. EtOH Benzol BuOH Titanium dioxide... Water Min. sp. Benzol EtOH BuOH Zinc Oxide............ Min. sp. EtOH Benzol Water BuOH Lead-zinc.......... ...... Min. sp. WateT EtOH Benzol BuOH Titanium-sine____ Min. sp. EtOH Water BuOH Benzol Dioxane Dioxane Dioxane Dioxane Dioxane Dioxane Wood.......................................Min, sp. Benzol Wood BuOH Dioxane EtOH Water Abbreviations or symbols: Min. sp., mineral spirits; EtOH, ethyl alcohol; BuOH, butyl alcohol. creased when the films were dried, except for films soaked in dioxane. Their density was not regained until the redried film had been leached with water and again redried. Water and mineral spirits Jeached only moderate quantities of soluble substances from the films, but the other liquids dissolved large quanti ties, from 36.3 grams per 100 cubic centimeters for benzol to 55.5 grams per 100 cubic centimeters for butyl alcohol. Films that could be measured had swelled in area during soaking, but the ratio of areal to volumetric swelling varied widely (from 0.30 to 0.86). When the films were redried, they shrank to a smaller volume, area, and thickness than they had before soaking. This shrinkage corresponded at least roughly to the loss of soluble matter during soaking. All of the organic liquids, even mineral spirits, swelled linseed oil films more than water did. Wood, in contrast, is more highly swollen by water than by the organic liquids. That might be expected if linoxyn is a gel of low polarity, wood is highly polar, and similar polarity between gel and liquid determines the swelling capac ity of the liquids (2, 3, 4, 5). Such a consideration accounts for the closely related liquids, water, ethyl alcohol, and butyl alcohol, swelling linseed oil films increasingly in the order named and swelling wood in reverse order. But with dissimilar liquids, other fac tors not yet fully understood became important in the swelling of both wood and linseed oil films. Thus di oxane is less polar but swells wood more than butyl alcohol does, and mineral spirits, which is even less polar than benzol, swelled linseed oil films less than highly polar ethyl alco hol did and far less than benzol did. The relative positions of the liquids for the swelling of wood and of the oil and paint films tested are indicated in Table 2. Graham (2) found the same order for water, mineral spirits, ethyl alcohol, butyl alcohol, and benzol in the swelling of films of bodied linseed oil. White Lead Paint: Films of white lead in linseed oil absorbed less liquid and swelled less volumetrically than unpigmented films of lin seed oil in ail of the swelling liq uids. The statement remains true when the absorption and swelling of unpigmented oil films are taken as 70 per cent of the values recorded in Table 1 because the pigmented films contained 70 per cent oil and 30 per cent pigment by volume. In water, white lead was the only pig ment tested that effected such reduc tion. In the other liquids, however, all pigments reduced absorption and swelling to less than 70 per cent of the values for unpigmented linseed oil, and in that respect white lead was no longer more effective than other pigments. The liquids stood in the same order of increasing absorption and swelling for films of white lead paint as they did for unpigmented films of linseed oil, as can be readily seen in Table 2. Swelling efficiencies were 91 and 95 per cent for ethyl and butyl alcohol, respectively, which indicate the de velopment of slight porosity in the films, and 97 to 100 per cent for other liquids. The density of the films de creased when they swelled but was more than regained when they were redried. The increase in density of the redried films corresponded to a shrink age in volume and a loss of soluble material during soaking. Loss of soluble material from white lead paint films during soaking was relatively small, but it was larger than that for unpigmented linseed oil films in water ana mineral spirits. In the other liquids, the solubility always ex ceeded 20 grams per 100 cubic centi meters. but it was much less for films of white lead paint than for films of unpigmented linseed oil. The relation between swelling in area and swelling in volume was more nearly constant in all liquids for films of white lead paint (AQ./AV, = 0.28 to 0.39) than for films of unpigmented linseed oil. When they were redried, all films of white lead paint shrank to less than their volume before soaking. The shrinkage was approxi mately in proportion to the loss of soluble substances. There was a simi lar shrinkage in area when the films were redried except for dioxane, for which the area was greater and the thickness correspondingly less than before soaking. Titanium Dioxide Paint: In water, films of titanium dioxide paint ab sorbed more liquid and swelled more volumctrically than films of unpig mented linseed oil or of white lead paint. In the other liquids, however, the absorption and swelling by films of titanium dioxide paint were less than by films of linseed oil, and did not diner greatly from films of white lead paint. A comparison of the liq uids for their order of swelling (Table 2) of titanium dioxide paint film and dear linseed oil film shows that for the titanium dioxide paint, water moved from a position below mineral spirits to one above ethyl alcohol and that benzol and butyl alcohol changed places. The swelling efficiency of water and mineral spirits for titanium dioxide paint film was 100 per cent and that of dioxane was 98 per cent. Ethyl alcohol, butyl alcohol, and benzol, however, had swelling efficiencies of 56, 80, and 87 per cent only, and presumably left the redried films markedly porous. These liquids re moved much soluble matter from the films, but apparently did not plasticize the linoxyn sufficiently for the film to contract enough to dose the voids when the swelling liquid evaporated. The fact that the redried films gained in density is not inconsistent with this view because the large quantity of soluble matter was much less dense than the pigment, which remained in the films. In all liquids, films of titanium dioxide paint decreased in density when they swelled, but became denser and smaller in volume when they were redried than they were before they were soaked. The solubility of films of titanium dioxide paint in each liquid was some what higher than that of white lead paint films, and was very nearly equal to 70 per cent of that of films of clear linseed oil (the proportion of linseed oil in the paint), except in water and in mineral spirits. In water and mineral spirits, the solubility of titanium diox ide paint films, like that of white lead paint films, was slightly greater than the solubility of the linseed oil films. 3 GLD38030 The ratio of swelling in area to swelling in volume foe titanium diox ide paint films was 0.36 in water, which is within the range of ratios for white lead paint films, but was much higher, 0.55 to 0.85, in all other liq uids in which the measurements could be made. When the films were redried, those that had been soaked in water remained slightly greater in area but were much thinner than they had been before soaking. The films soaked in other liquids shrank in both area and thickness. Paints Containing Zinc Oxide: In water, films of the three paints that contained zinc oxide absorbed more liquid and swelled more in volume than titanium dioxide paint films. Among the three paints, the film of lead-zinc paint had the lowest absorp tion and swelling, followed by zinc oxide and then titanium-zinc with the highest. This order agrees with results previously reported. In liquids other than water, how ever, the films containing zinc oxide did not differ significantly in absorp tion and swelling from the films of titanium dioxide or of white lead paints. The absorption and swelling by pigmented films was less than 70 per cent of that by unpigmented linseed oil in all liquids but water, except that films of straight zinc oxide absorbed more dioxane. Comparison of the liquids for their order of swelling (Table 2) shows that, for zinc oxide and titanium-zinc paint films, water moved from a posi tion below mineral spirits for clear oil and white lead paint films to a posi tion just below dioxane. For the leadzinc film, water took a position above ethyl alcohol, similar to its position for titanium dioxide film. The changes in the position of water among the swelling liquids suggest that white lead makes paint films less hydroph ilic, titanium dioxide makes them more hydrophilic, and zinc oxide makes them still more hydrophilic. The swelling efficiency of water for films of the three zinc-containing paints was 98 or 99 per cent. Mineral spirits had a swelling efficiency be tween 95 and 99 per cent for these films, and benzol had an efficiency of 96 or 98 per cent for titanium-zinc and lead-zinc films but only 74 per cent for straight zinc oxide film. The efficiency of liquids other han water was as low as 59 and no higher than 95 per cent for straight zinc oxide films, and the efficiency of ethyl alcohol, butyl alcohol, and diox ane (after leaching with water) ranged from 69 to 95 per cent for films of lead-zinc and titanium-zinc paint. Thus the organic liquids tend 4 to leave pigmented films porous after soaking and redrying, especially when the films contain zinc oxide. The ten dency is less marked for mineral spir its, which also dissolves less, than for the other organic liquids, and for ethyl and butyl alcohols and benzol the tendency extends to zinc-free titanium dioxide paint. The tendency toward porosity is most marked for straight zinc oxide paint and least marked for straight white lead paint. There is a distinct parallel between the tendency toward porosity and the stiffness and brittleness of the swollen films. Films that become highly flex ible and tough when swollen ao not become porous when redried, but films that become difficult to bend without breaking and often curl badly when swollen may be highly porous when redried. A conspicuous example was the film of zinc oxide paint in dioxane, which was hard, rigid though badly curled, and very brittle despite a 143 per cent swelling in volume. When it was redried, leached with water, and again redried, it had only 59 per cent swelling efficiency and a decidedly lower density than before soaking. Porosity may be caused by loss of soluble ingredients by the film when the swelling liquid fails to plas ticize the film sufficiently (4) to per mit it to shrink enough to close the voids. Films of all three' zinc-containing paints decreased in density when swol len in all liquids. When they were redried, they regained or exceeded their initial density, since they lost soluble material of low density, except for zinc oxide paint in benzol and all three paints in dioxane. The excep tions were always films that became porous, as indicated by low swelling efficiency of the swelling liquid. Films of the three zinc-containing paints that had been soaked in diox ane retained from one-fourth to more than half of the dioxane when they were redried, and the redried volume was from 48 to 158 per cent greater than the volume before soaking. In contrast, the zinc-ftce films retained less than 6 per cent of the dioxane. The reason for this effect of zinc oxide is not dear, but it may be asso ciated with the stiffness and brittle ness of the 2inc-containing films swol len in dioxane. A structure of hard, nearly impermeable walls enclosing cavities filled with dioxane may be formed after the soluble substances have been leached out of the films. When the redried films were soaked in water, they quickly became flexible and reasonably tough again, and the dioxane was leached out by the water. After another redrying, the films shrank considerably in volume. The solubility of the zinc-containing films in water was moderate, but somewhat greater than that of die films with no zinc. In mineral spirits, the solubility was less than that of the white lead and the titanium dioxide films, and less to essentially the same as that of the unpigmented linseed oil film. The other liquids dissolved much more than mineral spirits or water did. Solubility of the 2inc-containing films in ethyl alcohol, butyl alcohol, and benzol was always less than 70 per cent of die solubility of unpigmented linseed oil, and was less than die solu bility of titanium dioxide film and not very different from the solubility of white lead film. The solubility of the zinc-containing films in dioxane was overbalanced by retention of dioxane until the diox ane was leached out with water. After the films were leached the quantity dissolved by dioxane and the leach water came to 104.4 grams per 100 cubic centimeters for zinc oxide film, 65.3 grams per 100 cubic centimeters for titanium-zinc film, and 57.7 grams per 100 cubic centimeters for leadzinc film. Most of this solubility must be attributed to the dioxane. The solubility in dioxane of the zinc oxide paint film, and probably of the leacl-zinc and titanium-zinc films, was so high that some of the dissolved material must have come from the pigment. The soaking liquid was not examined for presence of 2inc compounds, but tests were made on the solubility of dry zinc oxide, white lead, and titanium dioxide in both dioxane and butyl alcohol. None of the pigments proved appreciably sol uble in the liquids. Presumably, then, dioxane dissolves zinc soaps formed in the paint films by the reaction of the zinc oxide with arid decomposi tion products of linseed oil. The ratio of areal to volumetric swelling, AQ./AV,, for the titanium-zmc films varied from 0.32 to 0.69, much like the variation for tita nium dioxide films. The ratio for zinc oxide films ranged from 0.29 to 0.88 in organic liquids, but was 0.24 in water. The ratio for lead-zinc films ranged from 0.20 to 0.38 only, much like the small range foe white lead films. When AQ./AV, is large, the swelling in thickness is correspond ingly less than would otherwise be expected. When redried, films of the zinccontaining paints shrank below their volume before soaking, which corre sponds to the loss of soluble material during soaking with adjustment for any development of porosity. The films soaked in water remained some what swollen in area, but became cor respondingly thinner, as did also the GLD38031 film of lead-zinc paint soaked in dioxane and then leached with water. In the other cases, except when the dioxane was not leached out, the films shrank in area when redried, but usually to less extent than they shrank in thickness. Results with Weathered Films Results with films that had been weathered artificially are reported in Table 3. Linseed Oil without Pigment: Weathered films of unpigmented lin seed oil absorbed less water, dioxane, benzol, and mineral spirits, but about the same amount of ethyl jicohol and butyl alcohol, as the unweathered films. The swelling of weathered films was a little less than the absorption. Swelling efficiencies were 87 per cent in water, 92 per cent in ethyl alcohol and mineral spirits, 95 per cent in benzol, and 99 per cent in butyl alco hol and dioxane. Thus the weathered films were more inclined to become slightly porous than the unweathered films, which is further indicated by failure of the weathered films soaked in water and mineral spirits to regain their original density when redried. The liquids stood in the same order for swelling weathered oil films as for unweathered films (Table 2), ex cept that ben2ol, which fell between butyl alcohol and dioxane for un weathered films, dropped to a posi tion between mineral spirits and ethyl alcohol. The solubility of the weath ered films in water and in mineral spirits was greater than for the uftweathered films, but in the other liq uids the weathered films were consid erably less soluble than the unweath ered films. Nevertheless, the weath ered films remained much less soluble in water and in mineral spirits than in any of the other liquids. Weathered films of white lead paint absorbed less and swelled less than the unweathered films in all liquids. Swell ing efficiencies for weatnered films ranged from 83 to 94 per cent, which indicates the development of porosity. Nevertheless, all white lead films were higher in density after they were re dried than before they were soaked because of loss of lightweight soluble matter to the soaking liquid. The order of the liquids in swelling power (Table 2) was the same for the weathered as for the unweathered white lead films, except that benzol and butyl alcohol exchanged positions. Weathered films were more 'soluble than the unweathered films in mineral spirits, but were much less soluble than the unweathered films in the other liquids. The ratio of areal to volumetric swelling was always less for the weathered than for the unweathered films of white lead paint. All weath ered films of white lead paint shrank in volume when they were redried. Titanium Dioxide Paint: Weath ering greatly reduced the absorption and swelling of titanium dioxide paint films in water. The weathered film, in fact, swelled slightly less than weath ered white lead or linseed oil films. In the other liquids, weathered tita nium dioxide films absorbed and swelled less than the corresponding unweathered films, but the reduction was much less marked. Their absorp tion arid swelling were greater than for weathered white lead films in ethyl alcohol, butyl alcohol, and ben zol, and somewhat less than for white lead in dioxane and mineral spirits. The swelling efficiency of the liq uids for weathered titanium dioxide films ranged from 82 to 95 per cent except in dioxane, where it was 105 per cent. The high efficiency for diox ane may be erroneous, however, be cause the titanium dioxide film curled exceptionally badly in dioxane and proved very difficult to handle. The order of the liquids in swell ing power (Table 2) differed for weathered and unweathered titanium dioxide films in that water dropped from a position above ethyl alcohol for the unweathered films to a posi tion below mineral spirits for -the weathered film, and benzol changed places with ethyl alcohol. In all of the liquids, the solubility of the titanium dioxide films was less for weathered than for unweathered films. The ratio of areal to volumetric swelling was less for the weathered than for the unweathered films in ethyl and butyl alcohols, but greater in water, benzol and mineral spirits. All weathered films of titanium diox ide paint shrank in volume when they were redried. Paints Containing Zinc Oxide: Weathered films of the three paints that contained zinc oxide absorbed and swelled less than the correspond ing unweathered films, except that the weathered straight zinc oxide paint absorbed and swelled slightly more In ethyl alcohol than did the unweath ered film. The extent to which weath ering decreased swelling, however, was usually greater for water than for the other liquids. Nevertheless, the weathered films of zinc-containing paints still swelled much more in water than did weathered films with out zinc oxide. In liquids other than water, the zinc-containing films did not differ gteatly in swelling from the films of titanium dioxide or of white lead paint, and their swelling was less than 70 per cent of that of weathered lin seed oil except in mineral spirits. Water took a lower position ki the series of liquids for swelling (Table 2) the weathered than the unweath ered films of zinc-containing paint, as has already been noted with titanium dioxide paint. Perhaps this indicates that weathering in general diminishes the hydrophilic character of pigmented paint films. The order of liquids other than water was the same for weath ered and unweathered films contain ing zinc oxide, except for a transposi tion of the neighboring liquids Ibenzol and butyl alcohol for the leadzinc films. This transposition occurred also for the weathered and unweath ered films of white lead paint. The swelling efficiency of water for the weathered film of zinc oxide paint was 90 per cent, and that for the lead-zinc and titanium-zinc paints was 98 per cent. Other liquids always had a lower swelling efficiency than water for the same zinc-containing paint. The swelling efficiencies for the weath ered films closely parallel those for the unweathered nlms, and reveal a marked tendency for the zinccontaining paints to become porous when redried. Most of the films in creased in density when redtied be cause of a substantial loss of soluble ingredients of low density during the soaking. There was a decrease in den sity or failure to gain in density, how ever, for the three zinc-containing paints in water and for the zinc oxide and titanium-zinc paints in dioxane. The weathered films of zinccontaining paints, like the unweath ered films, retained dioxane after they were redried until the dioxane was leached out in water and the films were again redried. Such retention by the weathered films was proportion ately less than by die unweathered films, although it was still substantial. The solubility of the weathered films of zinc-containing paints was always less than that of the corre sponding unweathered films in the same liquid. The solubility of the weathered films in water was low, from 0.5 to 1.8 gftms per 100 cubic centimeters. In dioxane it was from 27.4 to 30.6 grams per 100 cubic cen timeters and in the other liquids it was from 2.4 to 11.3 grams per 100 cubic centimeters. The ratio of areal to volumetric swelling, AQ./AV,, for weathered films of zinc-containing paints was always lower in water than in organic liquids, as was the case for unweath ered films of all paints and of linseed oil. This was not always the case for weathered films that contained no zinc oxide, however. Weathering some times raised and sometimes lowered 5 GLD38032 the ratio AQ./AV, for correspond ing films of the zinc-containing paints without revealing any consistent pattern. After films of zinc oxide and of titanium-zinc paints were soaked in water and then redried, they were larger in both volume and area than they had been before they were soaked. Films of lead-zinc paint were larger in area and only slightly smaller in volume than they had been before they were soaked. All zinc-containing films soaked in dioxane were larger in both area and volume after they were redried than before they were soaked, but they shrank when subsequently soaked in water and redried. The films of zinc oxide paint still remained larger in volume and the film of titanium-zinc paint remained larger in both volume and area, however, than they had been before they were first soaked In dioxane. When the final volume of a film was larger than the original vol ume, the final density was lower than the density at the start of the soaking tests. Conclusions Films of linseed oil and of linseed oil paints absorb, swell, and lose sol uble ingredients in a number of organic liquids in much the same man ner as they do in water. The organic liquids can be arranged in an order of increasing swelling power that is nearly the same for all of the oil and paint films, both before and after the films have been weathered artificially. The oeder of the organic liquids in this series is mineral spirits, ethyl alcohol, butyl alcohol, benzol, and dioxane, except that for unweathered films the neighbors butyl alcohol and benzol may exchange places, and for weathered films benzol sometimes drops to a position between mineral spirits and ethyl alcohol. The order of the liquids in the series differs greatly from their order for the swelling of a strongly hy drophilic gel such as wood. Mineral spirits and benzol fail to swell wood measurably, but both swell oil and paint films, with mineral salts at the bottom but benzol next to the top in the series for wood and at the top of the series for oil and paint films. The order of the series of homologous liquids (water, ethyl alcohol, and butyl alcohol) for wood is the reverse of the order for oil and paint films. Polarity appears to be one of sev eral properties of liquids that govern their swelling power. The more polar liquids swell hydrophilic gels to a greater extent and hydrophobic gels to a lesser extent than the less polar liquids. Thus oil and paint films seem to be less hydrophilic than wood, as might be expected. But properties other than polarity also affect the swelling power of liq uids. For oil and paint films, one of the other properties may be the solvent power of the swelling liquid for in- redients of the films, because the igh-swelling organic liquids always table 3 --AFTER WEATHERING--ABSORPTION. SWEUING, AND RELATED DATA FOR FREE FILMS OF UNBODIED LINSEED Oil AND UNSEED OIL PAINTS WHEN SOAKED IN DIFFERENT LIQUIDS FOR THREE DAYS AND THIN REDIIIED. paint ; 0M1H&1 liquid ; j : Dry \ Den*ity Initial Absorption thiek- of liquid :Swollen:*edrled MM */Y,, t Smiling t Smiling MrM MID* rtnim > nffl- ...........ttm Inltlnl to Xb u m: in s elnaqr Vol<a* i Ant 9Uek<ii4rti condition AR, ttUck-lbY, " t mnn I AT, AV* t* s **** * 4**i *- MU* s Percent z Percent :Percent: An xPercent xPercentt iSSr * tSr * t x seat t t t cant i cant t ;Vater xSthyl alcohol Llnaeed :Butyl alcohol oil rDioxaae zBenzol :Mineral spirits s 1.1S t 1.17 : 1.15 t 1.02 > 1.15 : -97 : 1.17 : 1.07 ; 1.17 : 1.07 : 1.18 : 1.19 1.17 8.5 > 1.16 t 3.* X.15 9.9 1 1.15 X 2.8 s 1.17 8.6 t 1.17 8.9 t 6.8 60.2 9.X 388 56.8 11.0 : t > ( t 5.1 57.0 , 95.0 > 3X9 53.1 1 10.1 x 6.1 -l.l 1 87.5 14X0.0 > 57.0 >430.5 8 3.1 > 46,6 > AT > *1.9 > -aa > 0 > 98 > -86.0 1 (1) > 99 > -83.I j-15.8 t 8*9 1 99 s -26.3 1 (X) > 95 > -19.7 w> 98 # -tj t .J > ,3 X 4$ White lead L ;(Alter : 3,02 : 2.95 xStfcyl alcohol t 3-0J s 2.90 :Butyl alcohol ; 3.06 ; 2*70 tDloxMM $ 3.0? : 2,0* :Dloxaae,tb*fi water:...... sBensol i 3.06 x 2.87 DHoeral spirit* : 3.0* : 2.90 :Water : 2.28 : 2.22 ztthyl alcohol : 2.2* : 2.05 Tit*aiu*:Butyl alcohol s 2.28 * 1,91 <lloxlde:Dlomne t 2,26 x 1.73 T xlHomae* than water:. xBsntol : 2-2* t 2.06 ;Ktoeral spirit* } 2.25 1 2,l6 Zinc oxide 2 ;Water ; 2.60 : 2.3* xYtfcyl alcohol t 2,59 ' 2*35 :Butyl alcohol : 2.60 : 2.2* zDioxaae 1 2.61 z 1,65 jDioxane, then water:........... .i.,,,,. ;Benzol s 2.65 : 2.36 :Mineral eplrite e 2.60 s 2.*2 3.03 3.86 3.87 3.16 3.85 3.86 3.19 3.1 1 3-3 t 3.1 t 8.9 X 3.0 X 3.0 1 2.28 8.35 8.39 8.36 8.39 *5 2.26 3.0 X 3.X X 8.9 l 3.8 l 3-3 t 3.9 1 8.57 8.69 8.60 1.80 x.71 8.69 8.68 3.0 3.8 3.8 8.9 i. 2.* 3.X I t l 1 1 X 6.2 20.0 31.9 1x7 120 22.3 19.8 5.3 89.7 93.6 71.5 71.9 83.8 9.7 33.x 86.8 35.8 116 X9X 87.3 X5-S 5.3 > 16.5 > 88.5 1 110 > 113 > 18.9 x 13.5 .8 1 49.9 t 5.8 >411.8 > 8,5 >419.5 > 31*9 >459.0 > 33.9 >460.7 > (1) >......> 1.7 >411.8 > *.9 * 89.6 i 39.3 * 79.7 > 75.8 1 19.5 9.2 t 3.7 4l.l > 19.0 > 45.9 > 88.6 >419.7 > ..................... .. (1) >......I 18.6 1 41.8 t 5.9 t 43.6 1 89.7 > 88.9 > 3X.1 1C7 > 107 t 83.7 l 18.7 t 8,8 >480.0 1 11.6 >410.0 1 19.9 >415.7 1 36.7 >499.0 1 38.T >499.0 1 19.8 > *8.9 t 3.9 > *8.6 1 85 *1 91 99 99 85 n 98 90 109 105 88 95 90 86 87 98 T 83 -JL2 s 0 t *.8 * -U.5 1 2.6 x -9* x -10.5 > 8,6 x <6.2 t -6.2 1*10.6 i-XT.O 1 -11.6 1 49,0 X-lO.8 X 10.1 > (1) ............... -6,8 1 -.1 1 -6.6 > -.3 > 1.7 IE 41*6 1 -9.1 1 -6.3 t -8.8 : 4.9 > 6.3 < -8.3 > -10.0 > (1) >........... .. -U.l I W >......> -7.3 > -5.9 > -1.6 > -8.3 > -3.0 > 4.7 > *.3 > 1.2 t -.8 | *6. 1 5.0 > -1.8 1 -6.7 > -5.9 1 -1.8 > *98,8 > 43.8 1*93.6 1 39.5 1 -3.0 >438.7 -3.1 t -3.8 t *.8 > 1.2 > -1*1 * *! x -8.6 *1V.0 -13.3 -17.8 -81.8 -13.8 -11.6 -.6 -13.8 -13.8 -1*0` 19.1 -11.2 1.8 -7.6 -9.5 45.5 -30.6 -9.5 *1.* Lead* tine L2_ ** jVeter : S.frf X 2.60 xXtfcyl alcohol : 2.86 x 2.65 zButyl alcohol t 2.88 s 2.50 :Dioxane : 2.89 x 2.06 ;Dl<ucaoe, then water:..,... :Bensotl x 2.88 t 2.51 :Xiaeral spirits : 2.6$ x 2.70 8.86 3.01 3.01 8.98 8.98 8.99 3.5 3.5 3.5 3.3 i* 3.9 3.9 1 X 1 t X X7.3 19* 30.9 89.0 107 29.0 13.6 16.9 1 8.5 >419.0 > 98 -.3 > 41.8 > -1.3 > 18.6 t 7.8 >411.9 1 -7.3 1 -3.8 1 -9.0 > 88.7 t 9.7 >418.9 1 79.? t 99.0 >439,1 1 Q* K *7.9 -3.9 -3*9 1 .* f 41.8 1 -1.9 > 91.8 > 89.9 >450.0 1 8n -12.2 t -0.1 1*12.3 * 87.6 > 15.0 >4lH3 t 95 -5-J > 1,1 > -9.0 > 12.1 > 8.9 > 49.0 > 89 -3-3 1 --.7 S -1.0 X xMater : 2.2* x 1.97 2,2* 3-6 s 88.3 87.7 1 18.3 1*19.3 t 96 a 1 0,7 s 9.6 rittaiv-^kthyl alcohol z 2.27 * 2*09 8.39 8.9 } 83.9 22.0 x 15.9 > *5.0 > 98 -9.8 1 -8.5, -.7, stse xButyl eJcohnl i 2.26 s 1.9* 8.37 3.7 I 37-5 35.6 > 88.5 >415.0 s 95 -9-9 1 -8.5 > -.9 sDioxaaa . 1 2.26 t 1,69 2.07 3.6 1 103 95.5 > 60.1 >488.8 t 93 47-7 > 48.0 1 *5.9 *5 :DloKane then water;. 2. Si s. 139 t 106 t (1) ............... 88 UoO.x (1) X......I zBenxoi 1 2.26 : 1.90 2.32 3.5 I 90,5 1 39.31 31.3 > *6.9 1 97 -*.l X -3.9 1 -.8 > zXlneral eplrite t 2.28 x 2.10 8.30 8.9 t 16.3 g 15.6 > T>9 > *7.3 > 96 -8.0 > -3.0 1 41.1 > -1.3 8*5 4.9 -81.9 -5.8 -3-6 -5 -10.7 -11.3 -3.8 88.6 4.2 -8.9 -Tila too fragile to aeaeure. 6 GL038033 dissolved relatively large quantities work of paint films so well as water films of zinc-containing paints, the of soluble constituents from the films. does. ratio of areal to volumetric swelling, The position of water in the series Dioxane exhibits peculiar behavior AQ,,/Ay,, seems always to be larger of swelling liquids varies greatly with toward zinc-containing films that may in organic liquids than it is for films the composition of the film. For films be related to the plasticity of the insol* of ffie same kind in water. The rule of unpigmentfd linseed oil and of uble framework of the films. Zinc- is generally true, but there are some white lead paint, water has less swell containing films swollen in dioxane exceptions for weathered films of ing power than mineral spirits, but become stiff and brittle and when re white lead and of titanium dioxide for unweathered films of zinc oxide dried retain much of the dioxane for paints. The difference in action be anq of titanium-zinc paint, water has a long time. tween water and organic liquids may a i ery high swelling power, and is Wood presents a parallel in that, be related to the varying position of exc teded only by dioxane. Water when impregnated with organic liq water when the liquids are arranged stai ds about in the middle of the uids of high volatility but little or no in order of swelling power, and to setjes for unweathered films of tita swelling power, the liquids dry out toe greater tendency for films swollen nium dioxide and of lead-zinc paints. much less rapidly than do less vola in organic liquids to become porous The marked shifting of the position tile liquids that swell wood appre when redried than is the case when of water suggests that its position is ciably. The nonswelling liquids do not they are swollen in water and then determined chiefly by the hydrophobic penetrate the walls of the wood cells, redded. character of the fum, and that titanium and therefore must dry by the slow The volume, area, and thickness of i dioxide makes paint films less hydrophobic, zinc oxide makes them still less so, but white lead makes them process of evaporation in place and escape of the vapor through the tor tuous channels connecting the cavi films of linseed oil or paint are usu ally reduced when the Alms are swol len in organic liquids and then re more hydrophobic. If so, weathering ties. Dioxane, then, may be quite dded, as was found with water. The partly offsets the effects of titanium unable to penetrate and plasticize reduction is roughly proportional to dioxide and zinc oxide, because the the insoluble framework of zinc- the loss of soluble material to the position of water drops one or two containing paint films left after the soaking liquid. The shrinkage, how places in the series after the titanium soluble components have been leached ever, is reauced in proportion to any dioxide paint and the zinc-containing out, and thus remains trapped in the porosity developed in the redded paints are weathered. voids formed by loss of the soluble film, and, if the film becomes porous Organic liquids have less than 100 per cent swelling efficiency for oil and paint films more often than water does. This may be due largely to the greater quantity of soluble material leached from the films by most of the components. The solubility of oil or paint films in mineral spirits is low, seldom much greater than their solubility in water. Their solubility in the other organic liquids, however, is high, more than enough in relation to the solubility, its volume may actually be increased. When the films are rearied, much the same irregularities in distribution of the volumetric shrinkage between area and thickness occur as are observed during swelling. organic liquids. Low swelling effi-_ 20 grams per 100 cubic centimeters ciency probably results from voids for unweathered films, except those literature Cited left by dissolved material when the film fails to shrink sufficiently in vol of zinc-containing paints in benzol, where it is about 15 grams per 100 1. Browne, F. L. 1955-56. Swelling of point films in water, I through VII. ume as the swelling liquid evaporates. If so, a second factor in the develop ment of porosity in films may be the plasticity of the remaining insoluble cubic centimeters. Clear oil films are more soluble than pigmented films in the organic liquids other than mineral spirits, except that zinc-containing Jour, of FPRS III (5): 108-24; IV (6):591-400; For. Prod. Jour. V (1): 92-6: V (2) :l42-6; V <J):192-200, VI (4):152-9; VI (6):235-40. 2. Graham, I. 1955. The effect of solvents portion of the film, particularly the plasticity when the last portions of swelling liquid are evaporating. Voids may be readily closed in a highly films are more soluble than clear oil films in dioxane. Weathered films, which have al ready lost much soluble matter during on linoxya films. Jour, of Oil and Colour Chemists Assoc. 56:500-6. 3. Gul, V. E. 1953. The role of molecular forces in the mechanism of swelling. Kolloid, Zhur. 15:170-7; Chem. Abs. plastic film, but remain in a more rigid film. Consistent with this view are the the weathering, are less soluble in organic liquids other than mineral spirits than the corresponding un 47:9723f. 4. Houwink, R. 1947. Dissolving, swell ing, and plasticizing of polymers. Proc. XI International Congress of Pure and facts that unpigmented films seldom weathered films, but even the weath Applied Chemistry, London. 5:575:83. become seriously porous, and weather ered films have moderate to high 5. Salomon, G. and van Amerongen, G. J. 1 * ing, which makes films harder and more brittle, also increases the ten solubility. The distribution of volumetric 1947. Influence of structure on polymerliquid interaction. I. Relative and abso lute values of swelling equilibria. Jour, dency for the films to become porous swelling between area and thickness of Polymer Science. 2:355:70. when soaked and redried. It may then be concluded that the organic liquids do not plasticize the structural frame of films varies widely in the organic liquids, just as it does in water. For unweathered films and for weathered 6. Stamm, A. J. 1952. Surface properties of cellutosic materials. Chap. 18, Vol. 2. Wood Chemistry, by Wise, L. E. and Jahn, E. C. 7 I GLD38034