Wood for Storage Battery
Separators
001)separators f(ir stiiragt. hat,teriea in rnjtoriard vehicles w r e manuf:ictrirrd almost exclusively from Port Orford k \ h i t c s wdar previous tcJ 1941. Rapidly increasing demarids for this wood for u s e :is .-torage hattpry separators during World War 11 btwirnr so Iir.:ivy thiit it \vas pliicrd on the list of critical material. ThiP Inhoratciry t t i t ~ i i started an investigation of other w o i i d s huitrrhle : ~ h1):ittc.ry septrator material. i3attiJry Ycyaratiir> wrvv several purposes. One ie t o rnake r)iAhlr the dcvc~lopnicnt of compact storage hatt,cries. This itllo\\-a :in increase iir the numbtAr of lead plates per cell and thereby the elwtric~capacity of the battery. Separators also prevent contact betveen plates of opposite polarity, and thus avert short circuiting as a result of the vibrating and buckling of the plates. Further. separators must prevent lead from trreing between the negative and the positive plates, for this will produce undesired metallic conductance b e h e e n the 'two elements. On the other hand, tlw separators must alloiv free c4ectrolytic cont iritlurtnnce so as to generate electric current of t h ~ -pwifid tensity for which the batteries are intended. A n appraiml of prospective woods for battery s e p r a t t 1' rrlaterial involves scvcral factors. It comprises a considcxration of their ~ ~ I i y s i c ~and : ~ l chemical properties, supply, and availtibility. as \vcx11 :I* tvsti. with trial chemical treatments and performance t t i s t s . A s :I rcwilt oE R preliminary survey, Douglas .il:i>k:i y ~ l 1 0 cedar, ~ redivood, and bald cypress ~ v i v c:snmination as possible ,-ubstitute r o o d s . ort Orford ivhiti, ccdar o i l the, t i a s i h 01 >upply ording to 1939 cpnsus statistic>. thp cirticr of :iv:iil:ik)ility o f thv fivcz u-ociil sprcics is as follolvs:
Ih4orr the Lnitrcl state- entered the war in 1911, autoinohilr ctorage battery separators from w o o d were manutact tired almost e\clusi\clj from Port Orford white cedar. \ - t h e war progres-ed, the demand for this species ex*.ceded the supply. To reliebe t h e critical situation, a recrarcah project for finding other woods suitable for battery wparator- w a - nndertaken. The work intolted t h e de\elopnient of c*heiniraltreatments for rendering separators I'roni different woods sufficiently porous and flexible to tnret electrical and physical performance requirements in * t orage batteries. The following fite species-Douglas fir. tiohle fir, i l a i k a yellow cedar, redwood, and bald v y pre-9-w ere employed i n t h e experimental work. The tir-t three woods named were found to be acceptable *ub~ i i t u t e s f othePort r Orfordwhitecedar; thelast twowoods h a d \err good electrical properties, b u t their physical propv r t i e s were somewhat below those of t h e first three qpecies.
1. Hatter> 3eparator Treating Apparatui
-Figure
1. 11.
C. I). E. F. C.
780
Condrnaer for large tank Condenaer for small tank Solution supply tank pressuring ronlrol Agitation control air-cock Condenser line from small tank Large tank \lanual ternprraturr rontrol a t r a m \at\*
INDUSTRIAL AND ENGINEERING CHEMISTRY
August, 1946
78 1
MATERIALS Ahl) 4PPAR 4TlTS
I'iiextractrd wood separators of commercial manufacture were employed in thi. work. Those from Douglas fir. nohlt. fir, redwood, and Alaska yrlloiv cedar had the followiiig dimensions: inches parallrl n.ith the grain. ,513 inches ptqwndicular t o t,he grain, 0.070 inch over-all thicknes.k, aiid 0.039 inrli hack-web thickness : t,hoar from bald cypress, -I3/, incher parullcl \vith the grain, 5 1 3 j I n inches perpendicular to tht. graiii, 0.070 inch over-all thickntw, and 0.039 inch bark-n-rh thickness. Four %gallon rectangular iron t,anks (Figure 1F) were lor chemically employed Figure 2. 'ratlks I'srd in Ohtailling Data on Ratio of Voliiriie o f l'reitting Scilrrliiiri tci treating the separators. Weight of Wood Separators They were smaller but similar Left tn right: asaembled tank, tank cover, tank, haaket w i t h separators in design to that of fullsized cwniniercial equipment tor qeparator processing. T h e tanks Mere provided uith ferent treating liquors, agitatiotl oi liquor, arrii ratio I J *oIiitioti ~ to wood. steam coils for heating the treating solution, the temperature of which u a s controlled by steam valves G. A desired constant Each vsriable was considered in t,hc formulation oi iiii tJsprriaolution level was maintained in the tanks by means of tight, mental treating procedure. The procedure chosen thus ut'fittiiig tank covers connected t o condensing system A . Recforded a means of developing separators suitable for h:ittri,y tangular removable n ire baskets suspended from a bracket'on the performance, by modifying the extraction vari:ihlt,x. I t pwinner tidewalls of the tanks provided means for immersing the scribed a concentration of liquor and a solution-wood rxtitr :im1ile, t,o ensure that alkali was not exhausted during an 11-hour I ' X separators so that their ribs were in a vertical position in the treating solution. Circulation of the solution was controlled by t'raction period. This treatment, v a s followtid by xashiiig for :i houw in hot water and for 8 hours in cold running wattJr. 11hcii air bubbling from an air line near the bottom of the tanks. The data 011 the loss in weight were desired, the was1ic.d st*p:ir:itiirs Latter nere also provided ~ i t ah a a t e r line extending to approxiwere oven-dried and weighed. mately 1 inch from the bottom a t one end, an overflow near the Effect of Unmatched Separators!. P'ipurc, '3 -;tiow tlit. lii'rtop a t the other end to facilitate washing the separators, and a drain cock through the tank bottom. caentages of materials removed hy given concentrations of iicjritviiis T u o -mall auxiliary tanks (Figure 2 ) were designed for the puralkali treating d u t i o n froni two different po)s~oi collecting data on the ratio of volume of treating solution rators of the ,same species. It is evident from thct large t l i f f c r t ~ i i t v ~ to neight of dry separators. The tanks were so shaped a5 to between the t\vo curves that unmatchrd separators r~liiy var? allox J. wide range of solution-wood ratios (designated as the considerably in extractable material. .ilthough the rc.l~ai':+tcit+ ratio ( i f gallons of treating solution t o one pound of dry separain each set were similar in grain, growth rings, ctr., the!. tlitTc:rt*ll tors). They operated in similar manner to the large tanks in that radically in these respects from the separators in the othw .tzt. each was provided with a n air line for agitating the treating soluThe two curves are similar and approximat~lpparallel. h t ;I tion, a i t h a metal basket for supportgiven concentratioii t ~ talkali 111 t h l ing the separator&, and with a tight treating liquor, approumately 8 0' 32 r I I " ' more material wa< w t i acted in .et I fitting cover with connections t o a than in set 2. In1 reasing corwcnti .Ic-ondensrr for maintaining a constant tions of sodium hydroxide up to 3 5' level of treating solution. The auxilresulted in the removal oi i n r r e n h g iary tanks were heated by suspendpercentages of material; hctwn~tl ing them in water in one of the large alkali concentration< of 3.5 a i d 6 0' tank< (Figure 1F) maintained at the the increase in material removed v :IS desired temperature'. exceedingly small and iravhed a maximum a t approuimatrlj 6,0yc r R E 4 T I h C VARIABLES alkali concentration. Further Increases in alkali concentration JeThit properties of the separators creased the perrentagr ot rnatn1,il are reflected largely in the percentage removed. 0 2 4 6 8 /O / Z /4 16 /8 20 of material removed by the treatment. Effect of Solution Temperature. S # D / U M HYDRDX/D€ CONC€#TRAT/OH Some of the more important vari(PCRCLNT) The temperature of thr trrahng soluables affecting the percentage retion not only affectril thc. ptsrc*csritage Figure 3. Relation of Alkali Concentramoved from the separators are: wood of material rerno~(~11 frorn matched tion to Material Removed from Two Sets of variable-, conrentration of treating Dorigla. fir wparator., hut alto Zfatched Douglas Fir Separators Extracted soliltinn. temperature of qolution, difrbhanged thc yhalltb of t h c ~ -ol\chrlt for 11 Hours at 77-80' C.
.
~
INDUSTRIAL AND ENGINEERING CHEMISTRY
782
0 2 4 6 8 '0 / 2 /4 16 18 2G 5001 U H HYDROK/DE CONC€fVTRAT/Onl (PERCL
it T,
Figure 4. Effect of Temperature on Relation between Alkali Concentration and RIaterial Extracted in 11 Hours
The sodium sulfide and sudiuni hydroxide curves in Figure 5 show maximum removal of material :it 6.0% and approximately 3.5'3 alkali concentration, respcctively. These data werc emp l o y d as a basis for developing the rc~lativorfficiency-estraction curves for the trro trcnting solutions. KELA'TIYE EFFICIESCY-EXTRACTIOX CURVES. Iiespscing of the two pattern curves in Figure ,5, t o shon. the relative efficiency of aqueous sodium sulfide and sodium hydroxide treating solutions, required that a Douglas fir separat.or from cach of three (inmatched sets of matched separators be subjected to each of t'he treating liquors. Thus, a separator was taken from each of sets 5 , 6, and 7. They \rere treated Kith 6.0y0 aqueous sodium sulfide, other conditions being the same as those employed for developing the pattern curve. The loss in weight of the three ~ found to be 0.67, highcr than the separators was Z Y P T ~ R Pand corresponding point o r 1 the pattern curve in Figure 5. Then, after the value of each point, as raised by 0.67c, thr relative t>fficiencycurve for sodium sulfitic, was drawn.
-
36
concentration-estrartion c111'veI. ;Figure 4 ' , Tht, niasiruuw percentage of material removed ocriirrcd at c*oncentration?of
r----
~-.__
~
I
' I
34
6.0, 4.0, and 3.57, sodiuni llydroxide at 77-80", 87-90", and 97-100" C., respectively. These data slion. that 97-100" c'. is the most efficiont of the three temperatures employed for treating separators; it iy also the most, economical as regards cost of chemicals. Effect of Different Solutions. The effect uf different treating solutions on the percentage of material removed is of value only if the relatiTe efficiency of the treating solutions is shown. Figure 3 gives relatire efficiencies of t v o solutions, such as sodium sultide and sodium hydroxide, for rcmoi-ing material from Doupla. fir separators. PATTERN E x ~ n a c r ~ oCURVES. x Each point' o n the sodium sulfide curve is the average percent'age of material extracted from two separators t,hat mere simultaneously treated in the solution concentration indicated in Figure 5. One of the separators extracted for each point was taken from set 1 of tn-ent'y matched Douglas fir separat,ors; the other separator, from set 2 of tn-enty matched Douglas fir separators. The separators in s r t ' 1 rrere unmatched with those in set' 2.
Vol. 38, No. 8
32
30
s
28
g
2%
?
$
9
5
24
u
7
20
g
/a
z
SOOIUH 5ULflGE
1.2
1
0
2
8 IO I2 I4 /6 18 SOLUT/ON CONCENTRAT/ON (WRCENr) 4
6
20
Figure 6. RelntiTe Efficiency of Extracting Solutions on Rlatched Douglas Fir Separators Treated for 11 Hours at 97-100" C.
0-5€T.5 / AN0 2 0 - 5 E T S 3AND 4
1 -
1 1 1 I l 0 2 4 6 8 /O /2 /4 /6 16 5OLLJTION CONC€NTRA7/OM (P€RC€NT) 1
l 20
Figure 5. Relation of Alkali Concentration to Material Removed from >latched Separators of Unmatched Sets by Different Treating Solution4 at 9i-100" C. for 11 Hours
Data for the sodium hydroxidc u r v i ; Jvilre determintd siniilarly to those for the sodium sulfide curve, except that tlie separators employed were taken from two other unmatched sets oi' matched separators. I n like manner pattern curves m r e developed for solutions of 50 parts of sodium hydroxide p1~1;. 30 parts of sodium sulfide, 80 parts of sodium carbonate plus 20 parts of sodium sulfide, 90 parts of sodium carbonate plus 10 parts of sodium sulfide, and sodium carbonate alont..
Sest,, uiie separator from each of the same sets (5, 6, and 7) was treated x i t h 3.5% sodiuni hydroxide solution, under thc conditions (1mployr:d for obtaining th3 corresponding point on the pattern curve for this treating solution. The average lobs in pnrators v a s 2.1pc higher than the corresponding value on thr psttern curve. Accordingly, each prrint on the curvo of Figure 5 \v:L$ r:aised 2.1y0for the purpose of locating the relative efficiency curve for sodium hydroside treating solutions. The efficiency curvcq for sodium sulfide and sodium hydroxide are recorded in Figure 6. Similarly, relative efficiency-estraction curves (Figure 6) xere developed for the solutions of 50 parts of sodium hydroside plus 50 parts of sodium d f i d e , 80 p:irts of sodium carbon:ite plus 20 parts of sodium sulfide, 90 pnrts of ,sodium carbonate plus 10 parts of sodium sulfide, and sodium carbonate alone. The shape of the curves (Figure 6) showing the relation between concentration of treating solution and material removed depends on changes in the pH and t,he salting-out effect a t differmt alkali concentrations. This is confirmed in Figure 7 by the rapid rise ill material removed in conjunction with the rapid rise of pH a t l o x alkali concentration (Figure 8). At high alkali concentration the reduced solubility of the solutes appeared to result from salting oiit,.
August, 1946
INDUSTRIAL AND ENGINEERING CHEMISTRY
783
laining 80 parts of c.artx)iiatv plus 20 parts of sulfidr~,the percent.4 solution of 3% age of material rc~inovcdfroiii thc, ieparators is a function of aqueous sodium hysodium sulfidc I-oncc~itration. The carbonate has no effect, but droxide, under the' it doc^ have a pronounced negative effect after the sulfide conconditions employed ciwtration of the solution mixture reaches approximately 1.0% in this work, re(Figure 7 ) . At this point approximately 30 5% of material has m o v e d 28.67, of heen removed and the amount of material removed declines m a t e r i a l from aharply. Since this value is greater than the maximum (22.2%) matched Douglas fir material ext,ractable by means of the sodium carbonate (Figure 6 ) , separators. T-nde r the solute salts out. Figure 8 shows that' the pH of the sulfide the same conditions and of the solutions containing 80 parts carbonate plus 20 parts a solution containing d f i d e are the same at that, concentration here the carbonate3 . 0 7,s o d i u m h y sulfide curve branches off from the sulfide curve in Figure 7 . d r o x i d e p l u s 2.91 This seems to indicate a buffering effect. m o l e s of s o d i u n i I n a mixture consisting of 50 parts of sodium hydroxide plus chloride per kg. of 50 parts of sodium sulfide (Figure 9), the hydroxide contributes s oI u t i on remove ti Figure 7 . Influence of Sodium t o the alkalinity a t loiv concentratiorid. As a, result, the solution only 25.3%. T h i s Carbonate in Sodium Sulfide iiiixture a t a given concentration of sulfide removes more material is a reduction of 3.37, Solutions on RIaterial Remoled from the separators than does the sulfide wlicn acting alone at of m a t e r i a l f r o m from Douglas Fir Separatorthe same concentration. At a concentration of approximately matched separat,ors 2.570 sulfide in the solution of 50 parts sulfide plus 50 parts of the same set used hydroxidc, thv hydroxide loscc it= ixtractivt. ~ffcctivenessand the in the preceding 3.0% conceiitratiou treatment. If the 3.0Yc txw curves intersect. sodiurii hydroxide solution ~ v e r eincreased by 2.91 moles 01 Further increase., ill sodium hydroxide per kg. of solution, a solution of 14.670 con- 3 6 . , , clmcentration of the centration would be obtained. The sodium hydroxide curve i i i mixed solution rcsult Figure 6 s h o w that a 14.67, concentration of this solution will in salting out, arid the extract 3.47, less material than will the 3.07, concentration mixed solution beThis clobe check on the comparative effects of equal ruolvs ot clinics less effectivi. sodiuni chloride and sodium hydroxide, added to a 3.0% sodiurii tl1an the sulfide acthydroxide solution, seems to indicate that the decrease in exing alo~ie. tractive efficiency of concentrated alkali is due to salting-out acEffect of Kind of tion. The check furt,lier indicates that the tendency of increasing Alkali. Aqueous si)luhydroxyl ion concentration to increase the extractive effectivetioii.: of sodium >utness of the alkali solution does not extend beyond the peak of thc fide, sodium hydr(JXcurve; beyond this point the sodium chloride, which contributes Figure 9. Influence of Sodium ide, and sodium cat'nothing to the alkalinity, has the same extractive c,ft',c.t 21- the, Hydroxide on Sodium Sulfide Exaddition of cqual moles of sodium hydroxide. h ~ n i t t c plus sodiuw tk-actionof Douglas Fir Separators sulfide, at the conThe pI€ ol alkali solutions is dependent on the hytiroxyl ion at Various Concentrations for 11 ccntration and pH coirccntration. Thus, the shape of the extraction curves ill Hours at 97-100' C. Figiirt' 6 niight a1.o ho cqlairied as follnxys: ii rapidly i r l c r e a ~ i ~ ~ g recorded in Table I , wcre employed for t,xt r a c t i v e effective. . extracting alqmsiiiiately ai1 ei~ual pi:rcciitage of material lieas uf the alkali wliifrom iiiatched sepamtorr. Their relative afflict on the breaking tiotic at low cwriceil'traradius and AcTsibility angle of the separator-: \vas dctermined on tion? is clue to an intlie apparatus in Figures 10 and 11. creme in hydroxyl ion For the breaking radius test, the acparator ivas bent around con c e t i t r a t i o n ; the utivcly smaller cylinders. The raclius of the cylinder on curve flattrns ofr' as which a ..rc~ond break occurred n-as recordctl as the breaking the hydroxyl ion conradius of the ,eparutor. Thcs flexibilit J- angle was dctermined centration approachea . vas riw)rdetl as the angle bewith the separator Lit 25' ( ~and H constant value; t w e i i a liorizontal line arid a h i e through tht, point at n.liich the finally, a declination of free edge of the separator (oppusitv thc clarnped edge) came to the curve begins as the re.1 (Figure 11) v-lieii the estensir~u gage tripped. Sepahydroxyl ion conccnratorb that were trcatccl with difi'crent extr.icting solutions for rration remains nearlv removing like ari~otmts of material v - t w compared on percenttqge LEGEND ronstant, and, in addt80 PclRTS Of SODIUM CARmMTE distribution raiige. fi)r t)reaking ratiiu and flexibility angle. t i o n , t h e -altmg-out WRTS OF SODIUM SULFIDE Data on these ti1-o physical properties &relisted in Figure 12. ,!J A SODIUM SULFIDE pff cct hwornei greater 0 I 2 The percentages ior the separators t,hat jrithstood the 0.31at high solutt. o ~ i i ( ~ i ~ i i S O D I W SULFIDE WNCENTRAUON itich breaking radius are as fol1on.s: odium sulfid(:-trcated separa(PERCENT) t rations. ior-, 94%; cotliiiiri I i y t l r o r i i l ( ~ - t r c ~ .vparators, ~ t ~ ~ ~ ~ 05%; and TPbt. \\I'II iotiFigure 8. Helation of pH to 1 1 1 1 c t c d t o c1rti.1 t i i i n o Concentration of Sodium the. rffectivc.' e x t r a c Sulfide \lone or in 3tixture t i v e p r o p e r t y of s o d i u m sulfide b o t h Material pH of alone and ill iuixture Kith sodium carbonate. In these tests dolucioii solvellt Removed, % the percentage of sodium sulfide in the solution, whether alone 28 7 or in the presence of sodium carbonate, was plotted against the 28 7 percentage of material removed (Figure 7 ) . 29 0 Figure 7 shows'that, a t low concentrations of the mixture con-
P
784
INDUSTRIAL AND ENGINEERING CHEMISTRY ot
Vol. 38, No. 8
the t \\ o t ~ ) ~ n p o n e ~ini tthe > mixture.
For
~ ~ \ a i n ~ )thr l t * ,pH of a solution of 80 parts of mliiirri carbonate plus 20 parts of sodium sult i d ( b at I .Oc; concentration is int,ernietliate het n . c w i the p H values of its two rornponents at, t t i i . satrw ronrrntration.
Effect of Agitation.
Two diffcwnt rates
\v(ar(, cmploycd to test the effect on material
One produred insufficient rirculain that only a few air bubbles broke the -olrrtion surface per minute. I n the other treatment th(. solution was agitated rather vigorously hy air bubbles. h l l other extracting conditions, such as temperature, yolutionwood ratiu, concentration of solution, and tinirs of trtLatnwnt, were kept identical in the The amount of material extracted , from matched Douglas fir separators by the Figure IO. Apparat 115 for Determining Breaking Radius poorly circulating solution was 25.2%; that estracted from the matched separators from the ,-aiiw ;.et by the vigorously circulating solution was 27.9%. sotliuni carbonate plus sodium sulfide-treated $eparators, 88%. The result* indicate that any separator-treating installation This indicates that the three types of treatment produce similar w equipped for adequate solution agitation. ~Iioulilt results. Further, the flexibility angle test s h o w that the pcrEffect of Alkalinity on Separator Strength. Tests for detercentages for the separators having flexibilitics greater than 49 tiiiiiirig thc. tensile strength, flexibility angle, and breaking radius degrees are as follows: sodium sulfide-treated separators, 937"; sodium hydroxitlr,-trcatcd separators, 977&; and sodium rarof t h ( , twated separators were developed a t this laboratory as an aitl i t 1 c~orri~lating strength properties with electrical and battery honate plus sodium sulfide-treated separators, 83y0. pH of Treating Solutions. Figure 13 shoxvs alkuli coriccut n i ~)c~~Corniizncr properties. I n determining the effect of alkalinit,y t i o t i c plottcd against pH of the solution. Thcs pH valncv in of ttir, treating bath on the strength of the resulting separators, ~olution>of 0.25 and l.5Oc7, sodium hydroxide w r e employed. 1:ipire 13 for sodium Iiytlrciside were taken from thc litrrature; T h i s tcxri..ile strength \vas taken as the force required t o rupture others in Figures 8 aiid 13 \\-ere obtained with i~ Uecknian pH 0.5-int.h n-itlv strips of quarter-saved Douglas fir vparators, iiic4er. T h c p H incrcxasci with alkali conwiitration anti al>o frorii \v tien t tic, ltmd vas al)I)lietlin t h e plane of the specinitm and normal sodium carhonate to bodiuin sulfidc~t o sodium hydroxide. \\lien t o til(. tlirchction of thr, fiherz. Tmsilc strength and perccmtage H solution in a lox-cr p H range is niised vi-ith a Jolution of higlitbr of' triatc~rial rcmcivtd \VWI* plotted against time of trc~atnif~nt in p11. t h r rcsulting niisturcb 1x1. a 1" intcJr,iirtliate hctmcn tIi05c, rcmiovwi. ticiri
,
August, 1946
INDUSTRIAL AND ENGINEERING CHEMISTRY
fLfX/BJLITY
''
RANGE
w
3.68 PERCENT No2 C0,t 0.92 PERCfNT Na, S(29.0 PERC€NT €XTRdCTED) 0
4.8 PfRC€NT Na OH (28.7 P€RC€NT EXTRACTED) 0.8 PfRCfN7 Na2 5 (28.7 PERCENT EXTRACTED)
Figlire 12.
8 Lp
Relation of PhFsical Properties of Douglas Fir Separators to Different Extra(-ting %liltions When Percentages of RZaterial Removed Are 4pproximately the Same
14. iYith riiatclictl It!lJaI'atOt'., the l . 5 q c aolutioii rts20C.; of material in 1 Irour, v - h i w w the 0 . 2 5 5 solution re~ { i i i r6dhours for the samv removal. T h e specimen treated for I hoilr with 1.50% sodiuni hydroxide had a breaking strength of 2190 grams, whereas tlir dpecirrien treated for 6 hourh irith 0.25%sodium hydroxide had a breaking strength of 227j grams. If the percentage rxtracted is substituted trip time of treatment, a separatur treated for 207, 10,s iii iyeiglit by the stronger solution ha3 a tensile strength 21BO grams, herea as thr -(!patator treated for the -:-lnie Ins3 in weight by the u mlier wlution has a tensile +trengtli of 2275 grams. Gjmilarly, the percent agt' , ~ f material removed \vas Jiibetituted for time of treatiiwnt i n the plot against ten8 IO I2 id .ilv Ytrength, as shown on tlic SCLUTION CON'XNTRATION (PERCEh T) ,< drastic treatment \vas required for redm-ood than for Douglas fir, noble fir, and .\laaka yellow cedar separators in ordcr t o meet electrical conductance specifications. t-nder the various conditions trics:l, aotliuin hydroxide or sodium sulfide proved unsatisfactory fur treating solutions. On the other hand, sodium carbonate reinowd con4derably less material than did the other tn-o cheniicals ;:Figure 22). TT'hen it \vas uaed alone or in admixture \\-itli low concentrations of sodium hydroxide for treating the redn.oc:d separators, fairly promising results n-ere obtained. Two treating procedures, E and F, employing sodium carbonate and sodium carbonate r i t h sodium hydroxide, respectively, are shown in Table 11. They produced redv-ood separators n-ith fair to good clectrical and battery performance properties but' with st,renyth properties soniewhat inferior to those of separators from D O L Ifir~treated ~ by procedures A, B, C, or D. Bald Cypress Separators. Of the \roc~tl- employed, lxdd cypress xas the rimst resistant t o alkali. Treatments with sodium hydroxide solutions r e d t e t i in wparators with too high
IN GALLON5
JO
*-e-
0
2
4
6
8
l0
/P
I4
/6
/8
20
50DiUM HY'DROXIDL GONGENTRA.TICN (PfRCENT)
Figure 20. Effect of Solution-Wood Ratio on Material Removed from Douglas Fir Separators
INDUSTRIAL AND ENGINEERING CHEMISTRY
788
Vol. 38, No. 8
(GALLON5 OF 50LUTION ?fR POUND U f OVEN-DRY WOOD)
Figure 21.
Solution-Rood Ratio Curlr
4 sharp break occurs at 1.4 galluna of sulution per pound of wood
when ufiing
R
O.7.jv0 sodium hydroxide treating solution o n n n ~ ~ g l a a fir separators.
0
2
4
50L U TION
elertiical Ieyistancr, hair picliiiiiiidii> battciy pciiut tiiaii( C , ai111 m t h w lov strength properties. Of four procedures tt.-tetl. tht one using 5.0yosodium hydroxide plus 5 Ock sodium sulfult~1 I i i o cedure G, Table 11) produced separators Tyith fair elcctrical resistance, good preliminary battery performance, but -trtq$L properties somewhat lower than those of Douglas fir qeparators. The separators appeared t o have heen cut from rather poor grade stock, which may account for the low strength propertie. Selected stock for the separators would perhap.. result in improveil ieparator strength. CONCLUSIONS
Four chemical treatments of practically equal efhc.it.tic> were developed for separators from Douglas fir. They produced treated separators having electrical resistance and perfor nianccproperties comparable with those of separators from Port Orford white cedar, but their strength properties were slightly inferior. 2. One of the chemical treatments which was found suitable for Douglas fir and Port Orford white cedar also rendered scparators from noble fir and Alaska yellow cedar suitable for storapt, batteries. 3. Two chemical treatments M vru developrd for sepuratoi. from redwood. They produced acceptable elrctrical and battery performance properties, hiit qtrength propcrtieq wniewhaf 1111
8 / D /Z l4 16 18 20 CONG€N T 8 A 7 / O N (P€ R C E N T)
6
Figure 22. Relati\e Efficiencj of Extracting Solutioiis on Matched Redwood Separators Treated 11 Hour4 at 97-100" C. t~l10I
t o tllOse O f separitt(Jr3 IlIaIiC
troiii
the other four
\\ooi1*
rested 4. Out rhemical treatment n a s develuped for bald ckprea-tapdiIatorQ It produced treated separatorq having fair t o goou
t4rctrical rwstance and battery performance propertiw, hut Ytrength piopc'rties lower than those of separators from thc, other ltoods employed The comparatively low strength of the bald cypress might have been due t o second grade stock from \vliii*lthe s e p ra t ors M erp c u t 4CKhOW L h D G M h Y T
'The authorz, in behalf of the Foreit ProduLts Laborator?,
H I ~ I
to thanh the Office of Production Research and Development ot
the War Production Board for financial aid in this cooperattvc research. Sincere appreciation is extendrd to 0 IT7. Brov,n oi the Unireraity of Indiana for helpful wggestions, and to E. T Foote, R . P. Hammond, .J. F Harper, G. C. Appel, Rilliarti Thompson, John Schaefer, and associates of Globe-Union, Iiic for valuable advice and for conducting the commercial te>t>on the treated separators. Valuable assistance was furnishrd by the Evans Products Company, the Scparator Manufartiirinu Companr, a n d the Standaril I3attc.n Separator Compani
Temperature Dependence of Water Vapor Permeability .
iibuur i n the film tiy jurlipirig PAUL RI. DOTY, W H. AlI'iEIV, A N D H . 3lAKh: into hole3 in its immrtiiatt. tion of the water vapor Polytechnic Institute, Brooklyn, iV. Y . neighborhood; these holw ;in. permeability of thin, self*upporting films made of constantly forming :tiid (liborganic polymers is often large erivugh t u be of considerable 2ppearing as a result of the random motion of segmrnts i)i' tht long chain molecules. Because of the concentration graditLnt o! practical importance. A st'udy of t,his temperature dependence promises t o lead t o a better understanding of the fundamental the water, the net effect of this nearly random movenirrit i. >I drift of the water molecules toward the dry side of thrs film. nature of water vapor diffusion through organic polymers. Thir: article contains a number of direct measurements of the influence The number of molecules transported across a giverl ari>;i o f temperature on water vapor permeation for several types of within the film during unit time will necessarily be propoltiomwl to the concentration of water molecules and hence to thy soluself-supporting films, and attempts to contribute to a more debility of water in the film. The process of permeation is thu* tailed interpretation of the processes of diffusion and permeation. dependent on both diffusion and solubility. Since hoth diffusiori .is a result of Barrer's work (I) and the measurements previously presented ( 6 ) ,the process of permeation of water through and solubility are temperature dependent. permeation will nlso t w . a n organic high polymer film is considered t o be roughly as folin general, temperature dependent. The following. measurements were cxrricd out in iiri ap1i:ir:i t 11lows: Water molecules dissolve in the film on the side exposed and by a technique previously dclscribed (6). Thry pc*rnlit : I I I to the vapor, migrate by activated diffusion through the film, evaluat,ion of three constants, only two of w-hirh :ire ind(~pt~titli.r~f : and evaporate from the other side. I n general, flow occurs through preformed capillaries only as the result of a mechanical p = permeability constant,, cubic pc.iitimeters of v a ~ ~ u(:11r injury or imperfection. An individual water molecule moves standard temperature and pressure) passing per ~ ~ r o n thronuli tl
T
EMPERATL'KE varia-
