Document OzyQDrEEgvG9v7evqYxaGLLBw

Pt&ZtjAeA * ^o^mr'OAj SocJeztiEs rm^ tm c h e mic a l mmim m wmm mm mwme s . by W. T. M Jotesoss .dS* <27 , KmJU Laboattogy, |,JiiU88MJSg| In many wye, fete ot imp&ttmt part of a paint film is tSM oorfee of fete tln The oudEfteei is also, possibly, fete least kmm part of cte film. Critical paint performance properties, such m afteatei mmtker^biltty , nod Mppemmm depend m fete chemical amfet* of the surface of the paint fite lldg and ontsoX of fete paint film 9wa; would seem to; be an iaportant step in con trolling fetes Important paint performs properties* of tte filA is different from fete talk of fete film; .it is not the M@ as the fonnsla composition* There or sweral reason Zhis is s@ First, surfaces. % their very nature, differ frsa talk ecsapositions* Second, serfsee N4255 the mmtm of a paint fila pay defined m tbm upper 10 X of fils material. this is about a single lslar layer; this : Is fite surface. Practically, tbs extent to which eppeoadm* tbs analysis of tbs ypr 10 A of 11* surface is tbs extent to which approach surface analysis. tfe develop! a method for detewisissing tbs. chemical eag ' sitim of paint 11* surface a fSw y ssg in this laboratory. Me tmthod appmmtly allows us to approach rather closely, if not actually reach, two surface analysis, ffe estimate that <m analyse about 25 - 59 I f surface, and the nature of our results support tto idea that ws are analysing surfaces; the surfaces m 1 determine mm markedly different from; the total film osspositlons, m Ifethed W discovered that w@ couldj analyse the surface of a paint ; film by lightly polishing the surface; of the film with potassium bromide powder, then collecting the powder ** now contaminated with surface material * pressing it into ; disc, and infrared analysing the disc. This procedure| yields an infrared pctn of the film surface, giving the chemical capositi of the film surface, m defined by the infrared spectrum. this means that one earn get; a fairly cot^neheasive pic ture of the chemical nature f organic film surfaces because of the characteristic definition and broad applicability of infrared spectroscopy . DUP030024816 i the pmblmp for this type &\ mrm& analysis* Is to . mws only a very 'thin layer of the surface* yet fetaim si spl sis that 1 satisfactory m infrared analysis. > To adatewi this goal, w use m large film m* very lights uniform* abrasion* ind efficient seep! eollectien. W we 24" x 24" panels* giving m. 11 asses of 372,1..A The 11 surface is lightly polished by rotating a fin (steel wool pad amid potasaitmi ; ' bromide powder seetteted ever the film surface, the pptaaeiim bromide plus eaeple is titan collected with a vacuum device, : the surface abrasion apparatus. is show in figure 1* the i apparstw consists of two wain partus ; 4 panel support and carriage unit, la which the large sessile panel rides* sad a mrm^drlv ; traversing unit, tits traversing xmlt carries the drive magnet bade and forth across the panel. Hie operation of the apparatus m b visualised with th aid of Figure 2 . the abrading disc is opposed of a bar magnet am* bedded in w ia an slsmdaisB up. this cup fit lot a outer cup to which a steel wool pad is wired. This abrading disc is awed to : rotate and traverse the past! by the action .the drive magnet* m smn in Figure 2. The white lima on the dark paint surface are patterns of swirled potassium broaid powder* caused by the rotation i and trovers the abrasion disc. the abrasion discs mr show in figure 3, the lighter discs me used for softer films h heavier!discs for harder films, the discs rotate at 3@d spa sad traverse eh panel at Z ft, per minute. DUP030024817 Utt@ paml is eowd that with t&ese no ly and t%sodeiMy. manually at tte end ab traverse so thm whole panel surface is abraded 1* d dried before tsssu Depending upon ts barda of the surface helssg analysed, tm used #0000 #00* or #0 steel wool. For the very lightest possible abrasion w& do mot we jsny steel bromide powder (1,5 grams) is sprinkled evenly a<S then simply collected with the v w j collector, Surface sample is obtained in this way. After surface abrasion, usually one or two times over tfs film surfass, the potassium bromide powder, plus the surface sample, is olleeted by srospiiag over the 11 surface with the waemsa* cyelona separator collator* fhis .collector Is sboim in Figure 4. To operate the collector, waduum lias is attached at the top of the collector, As the vacuum foot is draw over the fils surface, tte sample is aspirated into fib# collector sad deposited in the sample eup at the bottom of the cycle separator, tilth this procedure about 951 of the potassium bromide powder used is recovered, Tha collected sample is 20@ms I screamed, ma11 steel wool fibers are r@mrd with a Magnet, and the powder is pressed Into a trarssparaae 13 am, disc ta a potassim tei<a@ die in the iwitiel DUP030024818 -$* the infrared spectra ware obtained with a feiddaEhar - : Met 21 double teat speeteopltetqsseter, lasing a bias* Os? disc in the reference beam, An rdiaat scale'-espender atttehmeafc for the epacteepbetafflrtcr allowed iarg ia detmetleii seasitlvity of p to 75 tines, this aliened as to analyse very smell (thin) ewnEece samples. Balls or total film samples <*bou& 1.0 tag.) neve ground with Or {Kinder in a mmhmleM, vibrator, then pressed into discs for Infrared analysis, this gave t o the total film spectrum of the film. Bates? Absorption ter gotaasiw Bromide there is a problem due to the absorption of water vapor by the potassium braid@ powder during the abrasion process atte aaommal laboratory conditimi. Ttte reason nay be that there is very little grinding of the potassium bromide; a significant reduction in particle eise la the abrasion process. 2ba abrasion time short9 mstsally less than five minutes; a that the potassium hmmide is mt long exposed t ataeospherie water vapor. In contrasts, grinding pot&mhm bromide in a mechanical vibrator gives strong water dferpfeii bands in the spectra. Cp<mBtint using siailarly prepared control discs, is the aly way te miadmiae this effect. DUP030024819 6 im lapottant question about the method ecmmtm the axtmt to nhieii tli@ goal mt txm surface analysis is scUawd, the analysis of only tfas top 10 A ef fttai wfm, fM toquizenent is qualifiod, however, by the posaibillty that actual &mm eoqpoaitions as im< than a stogie nolaetdar layer thick* Surface ooopoaitioas, a tfeidc as 5-10 mol&ml&r layers muld wra that on could remove 39 - 100 1 o surface, and still detonsia the t surface* Qualitatively* &m results suggest that only very thin surface layers am zanoood im our surface sitesion. Tfi surface cfNtiig found am tpit different from the total fil eopsi* tions, 4 are not detected la total fila infrared analysis, further e@i surface saaiyis shorn nearly tlw gas surface ccs^esittotis, indicating relatively thick surface layers and/or very thin surface layer removal. In our lightest abrasions, there is m visual evidence at absaalon, even after several soccoaaivo surface analyses* We bme swfe a rough quantitative estimate of the thickness of surface layer in ate!. Being the .fila area of 3721. csu2, an approadsiato film density of iJ ga/ec,, and a surface sample might of 0*2 -ng. (oatiaatod fton fete intensity of the speetnm), we obtain an average fila tfeidoMsa aqnivalant of spl of DUP030024820 Thtm estinftto is only ag^roslraete for aeMi. reasons, tet van if it is in mmsm bp m factor of 5, It still suggests that me am only rsmd^g about 25 A of surface. We plea to attaspi a direct wsmimt of the wsst of surface ress??! at a later data. Baeulta of Sene Surface Studies flour examples of simple applications of film surface analysis are gin in the f@lI0rf.ng sections. 1. The ferfaea of & Baiafc Ccmtainina Silicone Oil M a^ropr&ate initial test of & paint film surface analysis flMrtdbod is tbs detection of a surface active agent: at the surface of a paint film, A successful result amounts -to a rough certification of tbs method. Ws analysed tbs surface of finish containing 20 pp silicone oil. wr results age shoea la Figure 5. Tb speetrae of the film surface is that of silicone oil; it is completely different f*c the spectrum f the total flla. fls spectra* of the total film shows no trace of sllleone oil. Tho Method ha passed a first rough test Of validity. 2. Pigment and Silicone Plstrikstion at a Faint Film Surface It is raasonsblo to oxpoct that if mm could measure the dstrftmtita a surface active material in & film m&m tho surface, a mould find & high surface eonco&txattan thet decreased rapidly m short distonoo into the interior of tho film. On the other hand. DUP030024821 -8- 1m plgpent near to film surface might lie expected is be Just the %ms@e. Faint chemists have long spectulated that pl#smtad paint films hmm m elear Un layer at to film mrmm free e pigment, out atodiea a a pigwato finish, containing 900 p lillootn oil at a pi^wat/feteter weight ratio of 90/100 provide data m tkrnm qwB&ttmm* Wm @de aeveral sweegsi'f sorfae analyse a the surface of this finish, and our result may ba seen a Figure 6. Both 4istriteti@ns n as expected. The silicone cMees station is very high at to surfam md decrees sharply m short distance into the film, Bsis appears to he the ejected tehswior for a surface active agent in a film and this suggests that mx method of mmmmdMg, the eilieone concentration @ the silicone ratio * is pzotnbly valid* fhe silicone rati la the rati of the absorbance of a siHem hmS (123 aicrons) to a film hand <5.8 microns). Hi pigment 4istril:mtlaa eawe suggest theca actually is a layer of clear film (binder) mer to pipiiat at to palafe fil surface, Its saessawd pigment coacent&etlon is set at to surface and increases gradually going toward the interior of the film. 8a meeeuted to p%aat eoaeeatyafcion ae to ratio pignent to binder using the ahrhaae@ of the 143 micron ptgmmt bmd and the ahsorfeance of the 5.8 micron hinder head. DUP030024822 Hot that tli mrfmm levels of botb ar quite different from tbs total film Imml m mhmm at tbe lower right of the Figure Mb measured in tb total film, the silicon ratio is zm and tbe pfjpjmnt absorbance ratio is nearly on. Tb@ wilt of film tblekmess shown in the graph mm the ssmpl absorbance at 5.8 micronsg they mm proportional to film tfaietaes. A rough estimate suggest that the total film tbl&ttsss rewwed in this study may haws been about 01 nil. The plgaeat distribution result raise the question of ho small pigment particles are in a paint film. If we remove a film layer estimated m 25 - 50 & thick* mm there pigment particles this small in the paint film? It is passible that there -mmy b and that the smallest particles might concentrate neatest the film surface. This sise (SO 1) is below the level classified in pigment particle sire dis tribution iaeasurfflns| where m ssieh m 10"-20X (by weight) of the pigment particles may b classed a below 0.1 micron (1000*A). Our present 'belief is that there may fee pigment particles this siase, and that the distribution curve shorn may be valid. Ht alternatives are that the abrasion shears off portions of pigment particles or removes large pigment particles from the film, if do not presently believe either be probable. DU P030024823 m 3. Warn Surface of a gofantibylano Film As a @ad ttoe of fete ml petfowstfec of tibia 'awetiod of .stRrfana analysis* we aiudysad the mfaeo o a film of omnmlAl pflAjpatfylnna* Ha mmis again* that tte cwfac is esit dtftaant rm the tonal film M8p@@itu Ts iAc layer is a long chain id@* Itsi i4m is proMMy m alip-agants similar naeerlala am fteqtemtly added to plyidiyle at a few hundred parts per million to inpiove fil slip. the surface and total film spectra are shocm iti Kgm 7,, This result also suggest tibafc we mm doing actual surface analysis and shows that fbso poljwer filsw nay 1 surface analysed in this maimer. 4. The Coaceatgatioa of F'iaetieteer at a Feint Fils Sf Surface studies on a lacquer type paint film revealed that the phfhalato plasticiser cmcmtmt4 at the film surface* She fowrnl rati of plasticiser/polyaer for tibia lacquer was 4/10; surface analysis revealed that the siarfac plasticiser ratio wm &mt.t 8/10. m tiben measured the *aatfme* plasticiser level m m function of the plasticiser level la the total film* The results Mm shmm In Figmm 8* The graph sbmm that only at the 2/10 plasticiser level is. tli surface lev! the pane m the total fita level. Above this film lmmtp tibo surface plasticiser level rises r^idly* resetitag a iMKisun DUP030024824  xi, * at 20/10 plmttctmw mtSo r a film level of 7/10 itewi 'tide t&mt ^patently the plmtlclmr with the film in creases* decrease in the s x 6m eoaeeatratioa* 8wrftw MadHtficetion far ifcir--ioa & setiew objection to tMis method wrnld assist if the pf@ets abrasion chemically changed m signlleBt feaetion of the eittfaae sanplo* nr result# tew wt stew lisdlestio of each dW'HjKNWHttv^WM^ M,*# She first ddse that till afessasiosi doe not altar the mrf&ce sample is that, In the analysis of films drying % solvent wageraticai*. wiser these is the least ^frwiity for surface statical 'teg during film formation, the surface spastra we find are those of m film <BHqponsnt, such as a plasticiser* usBOodlfied. These is no witens o eteisteiX change. The sawsad wideaee is that tins sncfece analysis of poly- ethylene films, carried out itt both oxidising and inert atmospheres, km given the mmm results, fits surface spectre wars identical, idicn the dialyses war done in oxygen and nitrogen atmospheres. It is reasonable to expect that these different conditions would magnify diffawttosa caused fey tit abrasion of tjbe aim surface, if sueh <Si* ' ftHMUM existed* The question aurfae sapl dificatia by the absasioa process is still, towt?,, a cootimiag question* DUP030024825 SSt mU -u* W tw briefly described s method for deMstiUiinig. UMi ctesiiesl nater of tte swfaees of pmfnt films based on ffe light atewslo of the fils rs@ with potassiua hmmtd powder* followed % paUatlng this powder, and iiwtr#$ analysis. The netliod appear to b* roMfiwlj siapli Ml reasonably acosltivi. Using tibia *tted w@ have ^eternised tte etwai*! eaupwi* tiosts of sens paint ]at''*uxaeae, fts netted alao appears fe 1 possible utility for the acose^seettonel analysis of paint films. less *y is#rtsat parfoMam properties of paints* such as adhesion and durability* are @mra& pspti@ the ability m mmljm paint fil s Ik m tetsid ba of eoosidawW ?4ia in mid@mtmMmgl. tte Wwtoi: paints. i would iUke to mtammldg& tU capable assistance of E&tsi J, Reilly in this wnfe.. 1 would also like to thank the d# font Cmpmuy for pwi@.si fc@ publish tMs 'material* CD Sebaidt sad fclawia^ Z,, Haturo!tB<3n&g ?, 270*77 <1952) Stisapscs and 0'0tnmall JilfiS 74 s, 1805 (1952) ,, WWi S& 6/14/80 DUP030024826 DUP030024827 PIG S DUP030024828 PIG 3 DU P030024829 WESTCOTt -* RULER DUP030024830 srirl cu SURFACE WAVE LENGTH, MICRONS iso VO CO o st DUP030024831 ABSORBANCE RATIO FIGURE-i J THE DISTRIBUTION OF PIGMENT AND SILICONE OIL ' NEAR THE SURFACE OF A PAINT FILM, DUP030024832 WAVE LENGTH, MICRONS H CM HI S TO VO DUP030024833 SURFACE PLASTICIZER RATIO & PLASTICIZER/ POLYMER RATIO MEASURED AS THE ABSORBANCE RATIO 7.9/8.4 (MICRONS). FIGURE-1 i-lTHE CONCENTRATION OF PLASTICIZER AT THE SURFACE OF A PAINT FILM-AT VARIOUS TOTAL FILM PLASTICIZER LEVELS. DUP030024834