1286
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 39, No. 10
CONCLUSIO~S
The evidence, prcwntcd here can be rcwonatily iriterprc,tcd tis I I .\,11. >w. tor Tehting hIaterialh, S t a n d a r d Xo. 2335--84T'.Xeushowing that one or more polar organic compounds arc prcwnt i l l t r a l i z a t i o n Nilxiher for Petroleum P r o d u c t s by Color I n d i cator. tjhe hydrocarbon phase of the noncorrosive well. This matcrinl L'! Illid., Xo. GCi4--2, S e u t r a l i z a t i o i i Sutnber for Petroleuni l'rodprobably reacts n-ith the steel surface to form an iron salt n-hic.11 u c t - by E l e c t r o m e t r i c T i t r a t i o n . remains on the surfacc as an amorphous, coherent, adliercnt film. D a m i n , l i a t c , ISD. ESO.CHEM., 38,369 (1916). The iron salt would be oriented xvith the cwhouyl group t o n a r d '41 I;ilei%, C. IC., Y . G ~ . 4 . A('ori.04nn . Research Project Corr~tiiiithe metal surface and the hydrocarbon cwd exposed t i ) thil strcxni. tee, Dallas, Ilin lites, Aug., 1945, 19-30. t S I I.:iierts, Carlson. S m i t h . A i r c h e r .a n d Barr. Proc. S a t / . G'asoiirrr The film apparently is capable of repairing itself ~ r h c i i Asaoc. A m . . 1916. 51. I J ~waring occurs. This mechanism n-ould account for tlic l i y [ I r ~ ~ ( t i l t:vana. Cy.11., J . C h r m . Soc.. 1946, 2 O i , phobic nature of the layers, the thinncw of thr f i l i n , the :il~srniv~ ot 171 Giiffiii. 1%.T., n n r l G r w o . E , C'.. Natl. .J~\OC. Corroiion L L I K ~ ~ . tliflerential attack, and the low general rate of attack. M a y 1'346. Both naphthenic acid and sodium dichroniatc alipt~art o I N , '\I Tlnc-kerninn. S o r n ~ a r i a, i d S1ioc.k.' I). -1.. ISD. Ill,
First dip 2 g , benzidine [reiieenti 100 nil. acetone Second dip 10 g . sodium bromide 100 ml. distd. water 2 2 e . benzidine (reagent) 2.5 g . ammonium bromide j g. disodium phosphate (12 HzO) 0.1 g . citric acid (H,O) 4.5 nil. 9.5(% ethyl alcohol .)I) mi. di-rd. u-ater Impregnation a t 40,500 c , :i tir.t dip i n use are the instability of the trace and 2 e . benzidine (reagen I00 mi 8 3 3 ethyl alr the impossibility 01' storing them t'oi hol prolongrti periodr cscept by ihyiiig, +eroiid dip 10 g. a ~ i ~ r n r ~ n i i brca. iiii ivhicli must be follon-rd by rewetting tic.foi,t, niide l1.W. :3.,5 p . disr?diuin phnsphate ( 1 2 H?,01 1 papers of thr tj-pe \ \ - l i i i . l i ; t i t . 1 . 5 g. inonostidiiiin phoq p h a e~ ( H20: irnpregn:itcd with an aqueous m l u t i o i i 0 . 1 g. c i t r i r arid ~ H I W lravr hwii prepared in this 1ahoratiJi.i.. -I First dip 2 p . u-toluidine ireThcy w i i withstand prolonged storngr, crystd.) 100 nil a r c t o n e :it the degree of moisture required f o i . i r r i i n d dip iliisir iisv, and givi. satisfactory trarvr 10 g .odiuiii bruiiiidr I00 n11. d k i d . \niter 1vi)r the \-oltage rangt's tlrmilwd. Othri,. i 2 g . p-ani>idine li:iy(' I i w n prclparc,d n-hirh cBshihit lw10 g rodium broiiiidr (10 ml. distd. vater ~ic~t'mancnct~ of tract) 01' 11.s:. ability t o 10 nil. acetone vinaiii unc.h:inged U V I ' ~ a pc~i~iodl ) ( ~ i o l ~ i ~ 1 , 1 e fluiirebreiri Sufficienr 0 1 I'S u O H 118 8i.i'. S;oinc~of t h i w :iw cliwiihivl i i t tlii. dibwli-e fluiirercein 10 g -odiuiii iironiide I v]Nlrt, Ilistd. u a t c r t o irinke 101) I
1287
Hlire
PerniaThresh- Intensity old Gradation, nence of Voltage 7,51Trace 0.6 I l \ - r ~ l l ~ nEsrellent t
Stability of Paper Browns when kept moist, especially a t elevated ritmperature
Htur
0
ti
tCscellent
t.:scelleIit
Darkens gradually moist, but superior to S o . 1
BllW
0 ti
b:xcellenr
(:owl
Tuviis light zradually
I3lur
I1 1
Escellent
EscelleIir
IIrcwns uhen kept
Rrou-ti
11 X
Ercrlleni
Exrrllent
T u l n s bronn gradually either m o i s t o r dry
fd
[la ir I,
I (I
(;11r>d
F:sceiletir
Quite
__
I
buff
color
i~toist
nirlls
1111.
METHOD OF I ~ l I ' R E ~ ~ A ' ~ I O . 3
.\ niricliincx was built for inipregiiating ; ~ : ~ p (for ' r tliis pu~'pu;.e. T h t y papc'r .tcick
ixiriy. tJ('
t h i , ronipo;ition vas stati,tl t < I Illi':irh(d illifif(' J)lll1) alld 40'
uiiil
(io',
,
Sufficient 20c-; S a O H t o diw,l\-e telluriuin IIi>td w t P r rc make 100
11!1 8.c~lltit~~ (1)lc~~rlicti kmft I ~ J U ~ I J ,It t v ~ i . :I i)urc~ n-hitr paper \!-it11 ii iiigli t v a i -trenptli c'vrn when v x t anti \\-:I,suffiraiciitly c,ompact so that thcl surfaci. \;-as 11ot cut tby thr niiiviiig supplitd in rolls IJE the desired Ividth tind . t ~ - l i ~ s This , paperSI:-I; rolls through the +elution in stain1 tee1 d b(:tn-rt~iiruhber rollers which could lie adlusted in tension to give thc dt..?iretl nloisture content. I t was rll,cferrcd to do some of the iiiipi~rgnatiorisin tn-o stages; CUIIR('(luc,ntly a second dipping tank and rollers w r e incluticd in t 1 1 t h niachinr. Tlic paper ;vas pullid foi,n-ard by the tension between thc, riiblxbr rollers and then n-ax wiunci up on a plastic or hard r u b tler corc which was lockcd on a shaft. This n-inder shaft v a s (iriven t)y a slipping belt so that the paper n-ound under a sliglit rrnsion. The rolls of impregnated papcr xere removed from thr shaft and wrapped in a wised cvllophanc coating n-hich retained the moisture until the rolls were ready t o he used in the recorder. When the paper passed through tn-o surcessive dips it was partially dried with infrared lamps aiid a n ~ ~ h a u fan s t before entering the second tank. 3
METHOD OF TESTING
Testb were made on these papers with an iridium stylus pass111g over the paper a t a rate of 0.2 foot per second or 0.5 foot per second while the paper rested on a metal plate. Between the stylus and the plate was applied a measured voltage which could be altered from 0 to 7.5 volts. K h e n the stylus was traveling a t the higher speed, the threshold voltage was v t r y slightly higher, and ror a given voltage the mark was not so heavy as at the lower >peed. The variation of the mark with increasing voltage (inten.ity gradation) was examined visually by making half a down
.ntisfarrory o \ - ~ r range of nioistiires nnd t?nipern tiire'
p:ir:illeI niarks at c w l i of a wries of graded vo!tagei. .I satisfartory gradation was cwn*idc,rcd onc 1vher.e lines at a diffrrenre of one volt \rere distinguishablc ljy cbyil. Changes in thc intcBiisit!, gradation Ivere macle l>y altei,irig the concentration of the elecrrolyte in thc solutioti. Teats on the stability of the paper b(Jforr mid after tracing i r e i ' i ~iiiadc) tJy leaving dry papers and moist papers in their cellophane Tvrappers for a considerahle period at room tcmprraturc and i i i owns at 40' and 50' C. PREVEXTION OF FUKGUS GROWTH
Uccaude several papers which were stored over a period of time developed mold gron-th, it seemcJd necessary to include a fungicide in the impregnating recipe. The effect on mold growth of twenty compounds at several concentrations was investigated. Three substances which irere most' effectiae are: p-chloro-mcresol, O.OS%; trichlorophenol, 0.05%; and sodium fluoride, 0.5 weight 5 per volume of impregnating solution. Paper (Table I ) itself contained a considerable proportion of alcohol, and no mold growth was detected on it. COMPOSITIOIY AND PERFORM 4NCE OF DETECTOR PAPERS
Table I lists the compositions of solutions used for impregnating the paper. I n each case the impregnating procedure was as described in the preceding section. Each paper was made to have a moisture content of 35-10$ of the w t weight.
SOLUTIOS 1. .4lthough this benzidine paper possessed some advantages, it suffered two dran backs. h poorer contrast re-
*
INDUSTRIAL AND ENGINEERING CHEMISTRY
1288
sulted from thc gradual browning of the paper before tracing. light handling of the paper produced fingerprinting. SOLCTICIX 2. A modified formula permitted the chemicals tri be introduced on the paper in one dip and produced a papcr rvsistant to fingerprinting which darkened much less than did paper 1. A quantity of very successful papers has been produced by this formula, but the use of a warm impregnating solution introduced difficulties in quantity production. SOLUTIOS3. Studies of the behavior of benzidine papers revealed that, if the pH of the impregnating solution was lovercd, a paper was produced which darkened only slightly or not at all. .It the same time the permanence and sensitivity of the trace mere decreased. By placing the reagent on the paper in two dips and by lowering the pH of the second dip, it was found that a paper of superior stability could be produced without sacrificing sensitivity or permanence of trace, provided the pH of the second dip did not fall below 5.5. Efforts to reduce the brown discoloration by the addition of ant'ioxidants as suggested by Wagner (9) either aflected the st'ability or sensitivity adversely or had no effect. These papers darkened only to a light buff color after continuous storage at 40" C. There is no fading of the trace when the paper is allowed to dry out after tracing. SOLUTION 4. Papers made with o-t'olidine mere the most sensitive and the least stable. SOLUTION 5 . The p-anisidine papers were easier to prepare because the reagent dissolved in water. If the papers were used within two weeks of preparation, discoloration waa no problem. SOLUTION 6. Above 1.4 volts there was an electrolytic decomposition of the bromide, and the free bromine formed eosin dye, which gave a permanent trace. SOLUTION 7. The traces on paper impregnated with pyrogallol appeared on both sides of the paper. In all previous examples t,he trace appeared only on the side touched by the anodic stylus. The authors' explanation was that, in addit,ion to anodic oxidation, there was a pH increase a t the cathode side of the paptir. which was followed by air oxidation of the pyrogallol.
.
Vol. 39, No. 10
SOLUTIOV 8. In the tellurium papers the stylus wa9 made c,Athode so that the trace consisted of reduced tellurium. There I\ ds no background discoloration; consequently an excellent contrast was obtained. I t was not found possible to increase t tic sensitivity by thr addition of further reagents. CONCLUSIONS
Several solutio~isfor making electrolytic recording paper auu [lie method of impregnation arc described. One of these, containing benzidine as the sensitizing ingredient, has been the subject of more intense study. Two recipes are given for using thip reagent to prepare a recorder paper of good sensitivity and st>a. hility. ACKNOWLEDGMENT
The authors wish to express their appreciation for the cooperation and assistance of the members of the Technical Department of thc E. €3. Eddy Company. LITERATURE CITED
( 1 ) Electrical Engineers' Handbook, ed. by Pender and DelMar Vol. 11, sect. 14, p. 18, New York, John Wiley & Sons, Inc. 1936. (2) Fagan, C. P., J . Sci. Instruments, 19, 184 (1942). (3) Glas, Emil, Austrian Patent 135,822 (Dee. 11, 1933). (4) Hogan, Ressler. and Tribble, U. S. Patent 2,339!267 (Jan. L X 1944). (5) Schmidt, R., Ibkd., 1,918,199 (July 18, 1933). (6) Solomon, M., Ibid., 9,306,471 (Dec. 29, 1943). (7) Talmey, P., I b i d . , 2,318,013 (April 25. 1942). ( 8 ) Zhid.,2,319,766 (May 18, 1937). (9! Wagner, E. R., U. S.Patent 2,358,839 (Sept. 26, 1944).
Kinetics of Cure of Resol Resins hIANUEL N. FINEhIAS' AND IRA E. PUDDINGTON iVational Research Laboratories, Ottawa, Canada
'rhe rate and extent of cross bonding in phenol-formaldehyde casting resins of varying composition are determined by measuring changes in their electrical resistance and density during the process of cure. The electrical measurements are apparently sensitive to changes in the internal molecular arrangement of these systems while the density determinations are mainly characteristic of their macro properties. The increased rate of cure due to accelerators and retarding effect of plasticizers are indicated experimentally by the results obtained. The procedures are useful for studying the kinetics of cure of these complex systems.
D
URING the past few years investigations of the kinetics of
polymerization and polycondensation have dealt mainlv with linear or partially branched high-polymer systems. For these the experimental procedure has usually involved viscosity or osmotic pressure determinations. However, experiments of this type are not feasible in the case of'highly crosslinked phenolics of the casting resin type where polycondensation continues even after the material has gelled and finally become insoluble. For cross-linked polymers, methods of determining degree of cure have usually been very arbitrary, including tests of hardness, tensile or impact strength, water absorption, surface resistivity, etc. One semiquantitative procedure involves grinding the solid polymer to a powder and extracting whatever soluble material 1
Present address, Stanford University, Calif.
may be present with a suitable solvent, usually acetone ( 2 ) . .I variation on this principle was reported by Barkhuff and Carsre11 (1). They studied the extent of cure of thermosetting resins by determining the time required for polished cured resin blocks to show a characteristic microscopic pattern when treated with acetone. By this method they were able to report the varying effects of accelerator concentration, resin composition, and temperature of reaction on the degree of cureof these materials. However they did not believe that the patterns thup obtained furnished any direct evidence as to the molecular structure of the cured resin. A comprehensive study of the hardening of cast phenolics, or resol resins, was reported by Medvedkov and Polyatskina (16) who investigated variations in F d n e s s , specific gravity, solubility, and coefficients of light absorption for resols curing a t 80" and 90" C. Each of these physical measurements for characterizing the degree of cure of a cast resin showed potentialities Fhich warranted further investigation. Fuoss and co-workers (7) demonstrated that a better understanding of the molecular arrangement in complicated highpolymer systems could be obtained by studying the properties of these materials in an oscillating electrical field. Variations i n dipole concentration and strength, relaxation time, and plastiriaer concentration gave variable dielectric constant and power factor curves with changing temperature and frequency. Though useful for linear polymers, this procedure too was soon shown to be inapplicable in the case of cross-linked materials such as vulcanized rubber (19) or cured phenolics (9). For the latter neither dielectric constant nor power factor is very sensitive to tempera-
