Document M0NwLbnRe38E1nLG7Lan25VV

BET1II TO MARSHALL LABOflATOflY INDEXED'irzM DATES JULY 15a 1944 REPORT HO, 901 h. ^. ^ C^C telBEHCt COW v>' p f o r ORCUUTION PAHLJH LABORATORY REPORT SUBJECTS COLD CRACKING OF MAROON METALLIC DUCO" 1' . PERIOD8 FEBRUARY 1944 TO JUNE 1944 NOTEBOOK NO. 2066 REPORTED BY8 I0 R> HARDY APPROVED BY 8 E T, / HU; O/ES \ N29345 PABLXK LABORATORY REPORT i;0, 901 SUSJ3GT8 COLD CRACKING- Of MARGOS METALLIC "Dt?CO INTRODUCTION In 19^2* numerous complaints ware received from the raflnish field on account of the early failure toy crackTM ing experienced In Maroon Metallic `'Duco*,. A study v&s Bade of this problem and the trouble was- diagnosed aa cold crack ing,, Although very few complaints were actually received on the original, finish* it became apparent that the cracking was prevalent with this particular color before 5h cars were refinishedU These cracks were hardly ever completely removed when the oars were refinishod, and. therefore* served as a starting point for cracking of the refiniah film,, As a result of the study* the formula was slightly modified whereby the ratio of nitrooellulose to other film forming ingredients' was reduoedc This was don by eliminating the '9;* of clear base called for in the original formula* (See formulas on page 3 ) Sven though this change was relatively small* it appeared* from teats carried out at the tine to have accomplished the purpose desired* however* this was apparently due to the fact that the testing equipment* then available* was Inadequate*; for when the new formula was re tested* using improved equipment* It was found to lack auffiTM cient odd orack resistance, even though it represented a noticeable improvement (Table I),. Experimental-Project No., J~330 was drawn up to cover further work on this problem of cold racking with the object of obtaining a satisfactory answer-. SI- SUMMARY The present work embodied the testing of thirtyfive compositions representing modifications in nitrooelluTM lose* resin* pigment and plaeticizer content.,, and has reTM suited in the formulation of a finish which combines aatia~ factory hardness and buffing properties with greatly improved cold crack resistance,, This product has been given the ex perimental code J-213'dC~6493 It is formulated from 3/ aeo, nitrocellulose and raw castor oil (Hr>22) substituted for 1/4 sea,: nitrocellulose and pale blown castor oil (EUX20)* Otherwise,, i,t is identical in composition to the material previously used in the field? equaling it in hardness and buffing properties*. Therefore* it should be possible tc use this new lacquer without any ohange in application technique* nio CONCLUSIONS It has been concluded that the most important single factor affecting- odd orack resistance in maroon finishes ia the viscosity of the nitrocellulose used,, Tit. IV, And V) Withii: the pr&otios^ DUP030001037 nitrocellulose viscosity rang* for this work* 1/3 sec? to 1/2 seo0* the oold crack resistance improved as the nitron- cellulose viscosity incrsaaedo It was found that in order to incorporate good oold crack real stance with the necessary degree of hardness* the nitrecellulose viscosity had to be increased from 19,-9 seconds (5015) to a minimum of 23 seconds (5015)0 The latter figure represents about the middle of the range for 3/6 seo? nitrocellulose* If the viscosity of the nitrocellulose is permitted to drop below 26 seconds (5015),, the formula cannot safely tolerate the additional clear- base so neceseary for hardness, ' Formulations containing raw oaator oil (H-22) proved to bo superior in oold crack resistance to like formulae containing pale blown castor oil (H120? Thin iat provement was not attended by a sacrifice in hardness*, an added recommendation for the raw oil? Of the other plasticisers tested* the Baker oils* ?D^13 and PD~l6Ka were the only ones that gave improved oold oraok resistance without corresponding softening of the finish,, Ehey app'eared tb be about equal to raw castor oil (K-22) in this reepeot and could presumably be.used to. re place the latter if ever the need arose? Their use* of course,, would be contingent on satisfactory durability results? This work has demonstrated marked differences In odd crack resistance between the 2133303$M! Maroon Metallic and 253"2122 Black on one hand and 214-36259 Lancaster Gray on the other? The latter two were included in the expert mental work as controls for the maroon? However* at equal film thicknesses* the blaok proved to be little better in cold oraok resistance than the maroonj whereas* the gray was shown to be definitely superior? These differences can-' not be explained on the basis of solids ratios* plasticizer differences or nitrocellulose viaoosity (Table II* 4 mil panels)? The average viscosities for the nitrocelluloses used in these lacquers are 19?9 sec? (5015) for the maroon, 20?4 sec,, (5015) for the blaok and 22 sec? (5015) for the gray? Those differences are too slight to explain their cold cracking behavior? The gray is not only auoh more cold crack resistant but it is also harder than either the maroon or the blaok? It is believed that the pigment themselves must be important factors in explaining, these differences (Table II-B),, The nature of the maroon pigment is probably accountable for much of the weakness experienced in the maroon finish? Th # * v- *> * a* ** < ** ttIn practice,, the blaok la applied at considerably lower film thiokneases than the maroon because of the wide difference in hiding power. This, no doubt* explains the fact that no cold cracking difficulty has bean experienced in the field with black except in a'few special instances where excessive, film thicknesses were employed;. e?ga on hearses and ambulances DUP030001038 c.* higher viscosity nitrocellulose la believed to compensate for the presumably inherent weakness of the pigment* therebyproducing finishes of sufficient toughness and flexibility to resist cold cracking* 17o JCKPgaSKEKTAL The cold oraok data for this report were obtained by spraying thinned enamels on 4 x 12 inch panels'which had been prepared with standard automotive undercoats, The lac~ quera were sprayed at approximately 2 dnd 4 miis thicknesses* baked at XfiO*Fo for 20 minttea and then buffed, The lacquers used in this work were 213~3303<M-: (issued October 21* 1941}* 3-33G39-K (issued July 7, 1942} and modifications of the l&ttero The solids composition of the two Maroon het&llios ooded 2i3-33039M are? 21 >33039=* (Issued 10/21/43 21>-33039K (Issued 7/7/42) Bonig"..fYfc&o PX (19o 9w HL-233 . H-.120 H-lll W-S21 W2S4 v ?-173 5015) , 13v 4^ 5 4 2*7 3 3) 5,,o 0,1 Co 05 10.0 4o0 40 5 37 "7 *04 11,9,1 5,S 3*0} 3o $S 55 ,1 lCc.0 4.9 >5 4 o03 cC4 The testing equipment used throughout this work consisted of an ovsh kept at 100F0 and a dry ios capable of maintaining the reduced temperatures required*, "lie time, lapse between changing the panels from the oven to the ioe-bcx : Sr-aia the loe-box to the oven was as short as pc saible. Preliminary work was carried out to make certain that the conditions chosen for the oold crack cycle vers strenuous enough to demonstrate differences in the finishes yet not strenuous, enough to eliminate those of proven .flexi bility. The cycle selected consisted of 20 minutes at XOGeF.,. one hour at >20P and finally 20 minutes at 100?,.. again* * The panels ware .examined for oraoks after each oyele,. In the tables that follow* formula 213~33039-* C issued. 7/7/42) ia taken as the standard maroon to which the others ar compared-. All the lacquers are modifications of this formula unless otherwise stated* In each table tbs results of the first and last cycle are recorded along with the cycles in which, changes c courredo DUP030001039 , Results of the first set of oold orach tests are recorded in Table 1 along with panel hardness measurements which were run on the two mil panels after they had been subjected to 20 cold crack cyoles*0 Xn the attaohed Tablea I-A and X=B,, the first three results show the effects of increasing the nitroeellu* lose content of the formulae Hardness increased but cold crack resistance decreased The next resulta 14-10) show the effects of vari ous plasticisers., B&w castor oil (E-22) caused a narked provement in oold crack resistance, Bractioally no improve ment was gained by substituting blown cottonseed oil (E103) for pale blown castor oil (K-120) or by replacing dibutyl phthalate (H-lll) with 2-ethyl butyl phthalate,-. The latter, used as the total plasticizer^ produced some improvement in cold crack resistance, however,? difficulties were inourred in preparing the Maroon Toner Stock*, The Baker oils,, ?D16 and PB-16E, seemed to possess good, oold oraok resletanoe when substituted for the pale blown castor oil (K-120). A formulation using Baker5 e PD~l6 as the total plaeticizer was attempted but the Maroon Toner Stock could not be prepared from ito Dibutyl eebacate greatly improved cold oraok resis tance but caused too much softening of the finish,. When the plasticizer content of the formula was raised,, cold crack resistance increased, but hardness de creased (11-12) and reduction in plasticiser content produced the opposite effect whloh was expected (13) Cold oraok resistance improved when the pigment content was reduced (14) and when the pigment.content was increased, the opposite result was expeotedj the discrepant result (15) is probably an experimental error., The following results (16-13) show the effect of nitrocellulose viseeaityj l/S sec. PX is inferior to 1/4 sec., PX (1), and 3/3 seco and l/2 sec, PX are superior Relatively no improvement was gained by using l/4 eeo0 PXO nltrooollulose il9) and it was found to be rather unsuitable for use in the pulp process, Replacement cf ooooarmt oil resin (HtrH33) with hydrogenated castor oil resin (Rh'272) produced no improve ent,, The refinish panel (21) was Included to compare a typloal refinish system involving Karoon Metallic to the original factory finish. This accounts for the differences in hardness laea&Mremsnts between Tables I and XT. Xn the latter table the pencil hardness measurements were made on glass panels prepared for that purpose.-, DUP030001040 The last two results show that the black control (22) is hardly any better than the maroon (1) and that the gray control (23) la markedly superior* She finishes that showed promising results in the first aeries of cold cracking experiments were rsohecked along with some new formulations* which the previous work seomsd tc suggest. The results obtained in this series* Tables 11"A and XX~B, check the first* , The first four results in Table II are arranged to show the. effect of increasing the nitrocellulose vis cosity* and the second four show the effect of increasing the nitrocellulose, viscosity plus the effect of substituting raw oastor oil (H-22) for blown oastor ell (H--120) The last two compositions were formulated to prove that the difference in cold crack resistance between ths gray and the maroon has something to do with the pigments themselves* These'results substantiate that opinion for the saareon composition based on t;he gray solids (I3) was rola- . tively no better than 213~33039~M (2)5 whereas,- the gray (12) wag definitely superior* This maroon was formulated merely to obtain data., for the pigment content of the gray' formula is too low to give good hiding power in the maroon* Therefore., a composition was formulated containing plaati-ciEsr, rosin, and nitrocellulose in the same solids ratio as the gray but with the pigment oontent of the maroon (1.4)* The results show this finish to be definitely inferior* The panels in Tables 11-A and IIB that withstood 20 cold crack cycles at.2C*F without cracking, were sub-* jest ad to 11 cycles of progressively lower ioe-bos tempera tures* The results aye found in Tables 111-A and III~n The changes in ioe-box temperature are recorded above the cycles* The oven temperature was maintained at 1C0*FV The results In Table# IXX-A and Z2XB demonstrate the importance of nitrocellulose viscosity on cold cracking and also shew that formulas containing raw castor oil (H-23) are better than like.ones containing blown castor oil (3^X20). The results obtained from "}}& see* ?X with 3vl20. and 3/6 sec ?X with K22 appear to be discrepant, for past experiments have -shown the- latter plasticiser to be superior.. However,, this difference is believed to be due to a variation In the nitrocellulose viscosities, (See the note at the end of Table XII-3}* Thus farc this work has mainly stressed, the is portanca cf cold orach yealetanos* for that seemed to be the first problem. However* the' importance of hardness has not been overlooked Since 213^3303$"^ (10/21/41) was used in the field and found satisfactory in hardness and buffing properties, it was considered desirable to at least eial DUP030001041 it in har&neee., Thereforas the formulations* that seemed cold. rack resiafcant enough to tolerate an increase in nitrcoellulese eenfent? vara selected for tlia following' cold oraak teats* The modifications containing 1/2 sac., nitrocellulose ware omit tad In order net to r-aia the vis cosity cf the finished product any higher than neo*; jsary.. The results cf the third aeries of cold crack tests along with pencil hardness measurements ara found in Table IV,, The cold crack cycle used in this series consisted cf 20 minutes at 100*F,,., on hour at ~40eF,, and. 2C minute* at 100 F0 > Only the formulations containing 3/3 sec*. nitre* cellulose with no inorease in plasticizer (? and 7) equaled 213-33039-H (10/21/41) in hardness*. To reoheok tha results obtained thesa two lacquers were prepared from new material.using tha.same lota of nitrocellulose.. Tha results are found in Table V0 It was necessary to run these at ">4c*F,, in order to demonstrate differences in tha last two compositions., Tha temperature change from 100F,, to -20*Fo waa not sufficient to make them oracko . * The composition containing 3/3 sec.-, nitrooellu* lose and raw castor oil (H~22) waa finally selected and given the experimental code number J-21>=^6493 This com bination pxoduced relatively little increase in the thinning viscosity of the finished product compared with the standard using l/4 sac,, nitrocellulose, and equaled 213-3JO39-M (10/21/41) in hardness and buffing properties,-. The first two compositions in Table V represent the past standard and the present standard,, resulting from previous laboratory work The last two represent what was accomplished in the work described in this report*. V MISCELLANEOUS SATA Included in this work.were 4 z 12 inch durability panels for Pari i:.i and Florida exposure., These were sprayed with the laoqus'ru described in Table % and opposed at two and four mils thicknesses^ No* J2973r 1-46.covers this eeriea* These panels will furnish durability information cn tha various pla-atioisera used in this work,. Large 12 x 22 inch panala were prepared for ?arlin exposure.. These wars also sprayed at approximately two and four mila with tha lacquers in Table X0 They are being ec.b--footed to weathering conditions such as those experienced *d j cars whan cjpved from heated garages to- below freezing srahii'e,, At is hoped that tnls typo of exposure-will bring .cut differences not manifested by continuous exposure IHH3BICS . DUP030001042 s . <n iH 1 i H1 6 H ' A iu| i I h| | I d i ill t i I t l I i I I li am I i i i l " i I l t i i I i t va*t i i s i i i i ii*iii tti ti gi iI t i i i iii iiii i ii i i s i iO ii i i ii i ii i i ii s> t i i i i i i i i i I i $ t i i i i i I ** H i i trill iiiii ii II Legend: 81. S lig h t; Def. - D e fin ite ; T r. = Trace The re s in o o n te n t was ra is e d o r low ered as re q u ire d to keep th e s o lid s a t 2 9 9 5 6 .. 3aq cu C3 TW Oi -jt CVJ " 's. \id*- cf-u4 OH Hto a SC KorKOrs>\\ XO9 S !> 0 KV rH CVJ HCKU\ HOH1J> A0gft. HCV1J r*T cu It * <0r~ 3?>- ? o> 43 43 I -KK0\\ 1 a 5 fa 4 # *aHcu ^ (ft ? a a s 0 (ft 0 2 It 0 iOSHt 2 a a - & s * a 0* P,St s9c fOd si0r4 !d 8 8 R 5^ &a 2 A < < < < i aHV*H0d, a aA. cu O K\ X pcfl H 4p3 >> ** X3i 9*UJ O 4-* vO H VO HH <i A A <k KHo\ SC J>O d o m o, a Q He(ft. u ocu . o 5* r4. o J * 43 J? t* 3 ff H* ma ui> ua MM 00 nm K , P fO 8 8S u u H cu aSCc IT\ v> r- 0 <J\ O <H ft CVJ Oi rvd ..* oli c gft dII 9c +oH* pf0 a i-af A* 0 ri Pi vlf>t CU UL cu # cHu K\ H . H as i tj\ fO o fO K\ H CU X fe X At *a* At 5 ft cCruU- ,a-( IO *d m a & 5? d O d fot dft o u a A H Pi H Ik I* Ii ft CU ^ X X X k Xt'~ At At At JJ C~ *? & cu VO lO A r4. rt H rt ,0 AS tcfu\ O rk CU CU CU IO CU CU DUP030001043 p Vi Vi PP P p I H v! p + v* V p + HV V p V p H r-f P P 1\ g* V* * .%! H r-4 P P v p 3 T3 Vt ffi P p IIII P E-* p o pp *a cd v np If h p e* V#i rt V* P PP a mp H PP d fj rt | pp p *d mp V 6* pP H ra p A a n iph i aoo rH mp .v Q a .V pP u v 3 Hp V4 E- P P p V 64 p p p 4* mp J Vi J.* P EH ! i dP * b64 Jp? I* h H H 64 64 P P i >* i t f i > d H pP V P 64 Vi rt I 6>>4*4 ,Ptj?g i I * |j ^ >,, d 64 p 2 ' r-4 PP i Vi O *Eh*. i i i * d* 01 i *fh* &V p * Hb b K* ad r-l PP I u <9 H I I > I Vi I u | 64 p * I I; i. ii rt 64 f4 64 P I a I Qx Jfr*t * * * * H I M I t *4 t* P 64 P 64 H I | I 'I 1 ` 1 ' r-4 ! U H I I I U P 64 P 64 | 9 I p It II (M ft r** C\J ->s. .46* H <M J9*-; H-d* 1A4ijf ii o^ o ' K> rrv K\ K\ hi ^oi <vi 01 K> 0 l*\ T r? O H* At A At 01 3 Si * ^ Si 3; * * ri ri ll fji* #if 0p ?11I 4 8" 13 S'- 9 I ^ u .h * I 2 I I <, ", H 11 9 ' .9 WL h hm ft 0. ft m ft St ^ H 5 * t 21 i wR 5w - .'* H H H H J7 S $ % & < AJ c o a H .r : ? DUP030001044 I I IjA Panels cta! 2o3 alia lo 1/4* PX replaced by ljg{5 PX 2,3 213-33039-24 (7/7/42} Ja i/4* FK replaced by 3 A* PX 4, l/4,} PX replaced by 1,< 2!' PX 5 l/g" PX wltsfe H-22 Of o 1/4" PX with E-22 * 3/gR PX with H-22 g. 1/2" PX with H--22 21>^33039-M U0/21/41} 10a Plasticizer increased 25# >S *A o 253-2122 Bl&ok 12, 2.14^3 6255 Gray o Formula using solids* ratio of gray 14. Formula using solids** ratio f gray but with pigment orutent Of maroon Solids Fir^" EL-233 lb-120 H-Ul W*S21 14o 2JS 7-1, 2o p 3J. ' * Rati ITOT 5,0 P;> 0- Cp, __x__ w> =rrs> ~. - =. - => Cycles JKT - if" c.-J -> - .-r* rzj C,." - ' 7r,, Tsv, Solida Tr,*r 6.4 COo *;* 0 Rati 10.0 " -5*o [3*l *'> 5V; DUP030001045 81 g jj i 1 id I i 1 Vi A t& ' Si 1lo*!w*5 K I I Sa *g a 4 A I m sj s s' cj i o AA *11 s i i i i O' i S * Vi ' M01 O _m.( v. I# * v** h! g * $ ' & & rH VAi oi n , * F*1 W rfl JD H I OW ft 1 * g . HA I s01? jpp I *5 / 1 3 ` + V ` 5 ' H A | A A I sa . J ' I I IH 01 I + Vi & q- , oVi t*A r I BU f I 0w1 I H CD | ' <9 AH u I 8) rI S3 i S V '& M| *H4 Vi I I I I I . rI 01 r01i * V 0) Q I rj | | W 01 01 ol A ^3 * > A 5 A &0 6 Vi Vi 9O XX 0* A + &A CM W *0 *A9 AAAO > CM > &^ 9a *hH rAo Ofa A < .D .o CM CM CM CM H CM A W 0 <rl A HB 0 w* *d A SVA N. 0N A a o A O 7 S 5A A Ww A faA X A A A u Ol * A ll t CM 1 X X 4* t 1 X 4 7 as > r* . & 1 cr\ & M O 5 m > A O dco tco*O M MA A AA a ts*> .a JO s*H fe*H B X 0* oX m. K\ 0* X * H lb X p. X e. X KN K> c m in 3$ A CM t*\ *3 e AO 51 * m m -A r A < c < 10 < CM H CM H pH H .H KN rl t Pf> is 4 1 II CM W ON OCH * f . A H CM to NO r*^ 10 CUj * W HCM K\ Jt . 1MMWW1 AA HH Q .O hA lAi vv oo d*0 cc AA OO f Vu AA V* Vi 9A ff DUP030001046 t o o o 0 ? G r01i o0 & 0 0 f a 9 0 8 3 . 3t0 T HOO!e > DVO t o tti b o R D 8 <t C 9Onh3. rn O R8 0 lb J 3 OH 0 0 0 0 0 0 00 fl B R t C B 80J6 800f0 00 B 00 r & VOi X XX A* At At m *5 S. eB . CM "^va w. tf\ CM 8fafl H in H H CM t., > .Q t s* C n H <$ a of *3 H*3 a 4) m' fa t~) aX . At o <~t cu *> 5 cm cn--4 *5 "~v. N- C* X 0 o H O* , Ort fji. p) c\ fa + too X X !0 As At KV 0& W> .st AT p-< CM ri H CM CM CM CM CM; CM' CM 0 CM 0 A3 w m A3 ;d a * Si +- S3 ** -H<ei. 5s A XXXX At At At At n *s V) ..si- : ' rl e to "''a SO <i CM H CM o fa o *H""3 *Sc3t J*a-Si: fa 6 CT> M m OO fn m 3 KV at ri H CM At H O o X o OS $> fOaf cT H (X) 6} OS CM in CM CM ai H VO CM KV j0 rib -=r In ri H P S fa 0 CM CM Sb OJ -5 a o 0 o 0 A, CM r-l CM K\ 4- in VC o 0 9 o 0 <j o to Ov O SHI CM m v*< H r-i DUP030001047 Panels 4.1-4.5 mils 3 31//g4u*' PX replaoed by 40 1/4" PX replaoed by 1/2" PX 60 1/4" PX with IT 22 To 3/8" PX with H-22** 80 1/2" PX with H-22 10o Plasticizer increased 25$ X20 214-36259 Gray CD era - U) =D> -- < > TABLE I1I~B Gyolee 0 "4o *f V" 5o 6f 0 6 a ; JL,v Cl Tr. -5*P. Tro cc r=3 <TD Tr Tr0 Slo- Slo- Slo aju (=3 Tr.o Tr.. Tro Ts*o C9 CD >.T, c.;> CD CD CO ' <- ?r<, CT3 CD CO r-,-. yieoosity of nitrocellulose used is 3ltt (5OI5' *#Vl8ooslty of nitrocellulose used is 2T2" (5015? DUP030001048 CSJ CM ^1 A m X A* XAt a CM ft.*| S'l A,* 10 "-S. X A. *A . 10 UN UN UN CM CM CM CM CM ^ O CM 83 A A CM O 04 *0 M) 10 a H ft m CM O P u 3 o * *4 O u ** O CM M| X 3aI ON KN H> S !O 0 O c c c SB XL S * A4 *1 g H T5 h * Ci *S 0 A 4 A M *4 N A *4 X O o w O *4 X At 2i &h -i o q>CO c m ur CM CM H M} I K\ 1 8. K> K\ 8 Hft CM S Zm * A x o tfl ^s. s I*N ft A* ft H At $ H At m CM K> Z m Ai o>R l*> CM CM W K\ 4 IT pw W o\ ft CM * irv \ H H ft H i-t n H at,o fc. a3 A I* $ bn 3(TrHH OO a*cH wV: c J*C ** *e o * .c ca !* Si. s *- **g kK fOc.XD* DUP030001049 Panel 2 inlla 213-33039-* ao/2i/4i3 21333039-M 17/7/42) 3/B PX and H-22 3/3 ?X and H-120 TABUS Y "Tm.B .. -a Slo* Si a d#ns*-5 Dttf 0 Slo 0 Tr<> Cyoles Kx43*-rrm''" _ 4 _"' D*fo+ Def<* 81,* 51> Tr>~ Tjto3 Tr Tr0 crtr.4*r*i Bad '-- V*e-r*r* Bad Defo Tr0*=* *. Tr0*> ?Tc Tio Bad Bef. Tro Tr<> DUP030001050