Chemical test procedures for analyzing potting compound bases for spacecraft construction material

Fishman, N.

Muraca, R. F.

Thomas, H. G.

Whittick, J. S.

English

NASA Technical Reports Server

Monthly Technical Progress  Repor t  N o .  18 
November 10 t o  December 9 ,  1965 
December 15, 1965 
POLYMERS FOR SPACECRAFT HARDWARE 
MATERIALS SPECIFICATIONS AND ENGINEERING INFORMATION 
Prepared f o r :  
JPL Cognizant 
Engineers : 
Jet Propulsion Laboratory 
C a l i f o r n i a  I n s t i t u t e  of Technology 
Pasadena, Ca l i fo rn ia  91103 
JPL Contract  N o .  950745 
under NAS7-100 
Robert Harr ington 
Hugh G .  Maxwell 
by: R .  F .  Muraca, N .  Fishman, 
H .  G .  Thomas, and J. S .  Whittick SRI P ro jec t  ASD 5046 
W66 IACCESSION 24984 NUM ERI ITHRU) : /# f Approved : R .  F.  Muraca, Di rec tor  
/YODE) Analyses and Instrumentat ion g IPAQ SI 
( d s k  C R  7466d O R  TMX O R  AD NUMBER) ICATEOORI) 
GPO PRICE $ 
CFSTI PRICE(S) $ 
Hard copy (HC) /* m 
Microfiche (M F) 
Copy No. E$ 
ff 663 July 65 
._..- 
- 
https://ntrs.nasa.gov/search.jsp?R=19660015695 2020-03-16T20:01:41+00:00Z
8 
SCOPE 
Th i s  r e p o r t  covers  the  work performed dur ing  t h e  per iod  November 
10 t o  D e c e m b e r  9 ,  1965 on "Polymers f o r  Spacec ra f t  Hardware--Materials 
S p e c i f i c a t i o n s  and Engineer ing Information," SRI P r o j e c t  ASD-5046 under 
JPL Cont rac t  No. 950745. 
The primary o b j e c t i v e s  of t h i s  program are t o  assist t h e  Jet Pro- 
pu l s ion  Laboratory i n  t h e  development and p repa ra t ion  of polymeric ma-  
t e r i a l  s p e c i f i c a t i o n s  t o  be used i n  connection wi th  JPL s p a c e c r a f t ,  and 
t o  provide a study of t h e  e f f e c t s  of simulated space environment on se- 
l e c t e d  commercial polymeric products.  The materials and products t o  be 
s tud ied  and the  e x t e n t  of work t o  be performed are s p e c i f i e d  by t h e  JPL 
Cognizant Engineers.  
The program is  being conducted as two i n t e r r e l a t e d  phases,  running 
concurren t ly :  The purpose of Phase I ,  Polymeric Materials S p e c i f i c a t i o n s ,  
i s  t o  o b t a i n  q u a n t i t a t i v e  va lues  f o r  parameters which may be used t o  as- 
s u r e  t h e  performance of a g iven  batch of material i n  a s p a c e c r a f t  environ- 
ment. The purpose o f  Phase 11, Engineering Information, i s  t o  e s t a b l i s h  
material l i m i t a t i o n s  and t o  obta in  d e t a i l e d  des ign  informat ion ,  
1 
PHASE I .  POLYMERIC MATERIALS SPECIFICATIONS 
WORK PERFORMED 
Two chemical t es t  procedures have been e s t a b l i s h e d  f o r  RTV-type 
s i l i c o n e  potting-compound base materials: f i l l e r  c o n t e n t ,  and hydrolyz- 
ab le  h a l i d e  con ten t .  The r e s u l t s  of t h e s e  ana lyses  f o r  r e p r e s e n t a t i v e  
materials (General E lec t r ic  Company RTV-11, -60, -560, -615) are summa- 
r i z e d  i n  Table I .  Complete d e t a i l s  of t h e  procedures have been sub- 
mi t ted  t o  t h e  JPL Cognizant Engineer as sugges t ions  f o r  i nco rpora t ion  
i n t o  t h e  appropr i a t e  S p e c i f i c a t i o n s .  
The procedure f o r  f i l l e r  conten t  is  q u i t e  s t r a igh t fo rward  and t y p i c a l  
of those which involve complete s o l u t i o n  of a material i n  a s u i t a b l e  s o l -  
vent i n  o r d e r  t o  s e p a r a t e  i t  from a material which i s  inso lub le :  
About 0.3-0.4 g of t he  s i l i c o n e  base material i s  mixed 
thoroughly wi th  50 m l  of chloroform and 0.2-0.3 g of 
C e l i t e  f i l t e r - a i d ,  and then the  s i l i cone-chloroform i s  
e x t r a c t e d  from t h e  mixture by f i l t r a t i o n .  The material 
remaining on t h e  f i l t e r  i s  d r i ed  and weighed, and the  
weight i s  c o r r e c t e d  f o r  C e l i t e  f i l t e r - a i d .  The f i l l e r  
conten t  i s  computed as wt-$.  
Although a c h l o r i n a t e d  si lane i s  an  in t e rmed ia t e  product i n  t h e  pro- 
duc t ion  of s i l i c o n e  polymers, v i r t u a l l y  a l l  c h l o r i d e  i o n  must be absent  
f o r  q u a l i f i c a t i o n  of t h e  end-product as a space-grade material, s i n c e  
evo lu t ion  of c h l o r i d e  i o n  as ch lo r ine  o r  hydrochlor ic  a c i d  would be d e t r i -  
mental t o  s p a c e c r a f t  ope ra t ions .  The fo l lowing  is  a suggested procedure 
f o r  de te rmina t ion  o f  hydrolyzable h a l i d e  i n  RTV-type s i l i c o n e s :  
About 5-6 g of s i l i c o n e  base material i s  t r e a t e d  wi th  
50 m l  of e t h a n o l .  The r e s u l t i n g  s o l u t i o n  i s  t i t r a t e d  
p o t e n t i o m e t r i c a l l y  w i t h  0.1N sodium hydroxide and re- 
s u l t s  are repor ted  as wt-$ hydrolyzable h a l i d e  (as chlo- 
r i d e ) .  
2 
Table I 
RESULTS OF ANALYSES OF REPRESENTATIVE RTV-TYPE" 
SILICONE POTTING COMPOUNDS 
Sample 
RTV- 11 
RTV-60 
RTV- 560 
RTV-615 
Property 
F i l l e r  con ten t  (TiO,  ) 
Hydrolyzable ha l ide  con ten t  
F i l l e r  con ten t  (Fe,O,) 
Hydrolyzable ha l ide  con ten t  
F i l l e r  conten t  (Fe,O,) 
Hydrolyzable ha l ide  con ten t  
F i l l e r  con ten t  
Hydrolyzable ha l ide  con t e n t  
Value, wt-$ 
29.77 -29.90 
0.005- 0.003 
50.08 -50.33 
0.003- 0.002 
42.68 -42,71 
0.005- 0 ,004  
(none ) 
0.002- 0.002 
* General Electr ic  Company 
A simple e x t r a c t i o n  procedure wi th  chlorobenzene o r  methylethyl 
ketone has  been s u i t a b l e  f o r  most epoxy adhes ives ,  but ques t ionab le  re- 
s u l t s  have been obtained* f o r  Epon 4225 (She l l  Chemical Company) glass- 
f i b e r  tape impregnated w i t h  an epoxy-phenolic adhesive con ta in ing  an 
aluminum f i l l e r .  Continued work wi th  t h i s  material has  i n d i c a t e d  t h a t  a 
Soxhle t  e x t r a c t i o n  procedure i s  requi red ,  and t h a t  acetone i s  a s u i t a b l e  
so lven t  : 
About 10 g of t he  epoxy adhesive t ape  i s  weighed i n t o  a 
Soxhlet  e x t r a c t i o n  cup, and e x t r a c t e d  wi th  250 m l  of ac- 
e tone  f o r  a period of 4 hours. The cup and c o n t e n t s  are 
d r i e d  overn ight  a t  l l O ° C ,  then cooled and weighed. The 
amount of acetone-soluble ma te r i a l  i s  c a l c u l a t e d  and re- 
por ted  as wt-$.  
The q u a n t i t y  of acetone-soluble material, 42.87-42.33 wt-$,  c o n s i s t s  of 
both t h e  epoxy-phenolic r e s i n  and t h e  cu r ing  agen t .  Details of t he  pro- 
cedure have been submitted t o  the JPL Cognizant Engineer as a sugges t ion  
f o r  i nco rpora t ion  i n t o  S p e c i f i c a t i o n s  f o r  epoxy-base adhesive tapes. . 
* Muraca, R .  F . ,  e t  a l . ,  Stanford Research I n s t i t u t e ,  P r o j e c t  5046, --- 
I n t e r i m  Report N o .  1, August 9 ,  1965. 
3 
Vacuum-weight-loss de te rmina t ions  by a s tandard ized  procedure w e r e  
made f o r  epoxide coa t ings  designated as Eccocoat EC/200 and Eccocoat VE, 
supplied by Emerson and Cuming, Inc.  The base materials are s u i t a b l e  
f o r  a p p l i c a t i o n  b y  brushing o r  dipping; t hey  d e p o s i t  an i n i t i a l  c o a t i n g  
of about 5 m i l  th ickness .  The coa t ing  th i ckness  i s  subsequently in -  
creased by success ive  app l i ca t ions  a f t e r  each c o a t  i s  cured ,  according 
t o  manufac turer ' s  i n s t r u c t i o n s .  Since g iven  s p e c i f i c a t i o n s  are based on 
1 0 - m i l  c o a t i n g s  t o  s imula te  end-use, sample c o a t i n g s  of t h i s  t h i ckness  
w e r e  prepared as follows: 
I n  o r d e r  t o  provide a s u f f i c i e n t  amount of sample f o r  weight 
l o s s  de t e rmina t ions ,  t h e  coa t ings  w e r e  appl ied  t o  copper w i r e  
c o i l s  of s u i t a b l e  s i z e  t o  f i t  i n  t he  sample chambers: three- 
foot  l eng ths  of  16-gage copper w i r e  were wound on a ha l f - inch  
mandrel. The c o i l s  were dipped i n  t h e  coa t ing  material, 
d ra ined ,  and cured; then a second c o a t  w a s  appl ied  as r equ i r ed  
and treated i n  the  same fash ion .  
6 hours a t  room temperature 
Eccocoat VE, 6 hours a t  room temperature and 
2 hours a t  95OC (one coa t ) .  
A s  i n d i c a t e d  i n  Tables 11 and 111, weight l o s s e s  for both materials 
are f a r  i n  excess  of acceptab le  l i m i t s  and no i n d i c a t i o n  of l e v e l i n g  o f f  
i s  given af ter  192 hours of exposure i n  the  thermal-vacuum environment. 
Evidence observed thus  f a r  i n d i c a t e s  t h a t  these resins requi re .  more ex- 
tended cu r ing  a t  e l eva ted  temperatures,  t h a t  t h e y  undergo slow decompo- 
s i t i o n  i n  t h e  vacuum-thermal environment, o r  that  the  cu r ing  cyc le  is  no t  
long enough t o  remove any so lven t s  t h a t  are p resen t .  
Weight loss data  w e r e  a l s o  obtained f o r  a modified-epoxy coa t ing  
material, Clear Varnish B-276, supplied by Westinghouse Electric Corpo- 
r a t i o n .  
f o r  4 hours a t  room temperature followed by 1 hour a t  165OC, according t o  
manufac turer ' s  i n s t r u c t i o n s .  
p a r e n t l y  l e v e l s  o f f  i n  96 hours,  bu t  neve r the l e s s  i s  w e l l  o u t s i d e  of ac- 
c e p t a b l e  l i m i t s .  I n  t h i s  i n s t ance ,  an extended cu re  a t  t h e  e l eva ted  
temperature may h e l p  q u a l i f y  t h i s  material f o r  spacec ra f t  use;  t h i s  w i l l  
be checked. 
Samples w e r e  appl ied  t o  copper c o i l s  as descr ibed  above and cured 
A s  shown i n  Table I V ,  t h e  weight loss ap- 
4 
Table I1 
1 
W t .  Loss, g W t .  Loss, 3 
0.0235 3.02 
0.0148 3.02 
0.0234 3.48 
0.0288 3.40 
0.0311 5.56 
0.0312 6.09 
WEIGHT LOSS DATA FOR ECCOCOAT EC/200* 
(125OC and t o r r )  
Time,  H r s .  S.  W t . ,  g 
Time ,  H r s .  
192 
W t .  Loss, g Wt. LOSS, $ 
s. W t . ,  g 
0.7788 
0.4901 
0.6727 
0.8463 
0.5589 
0.5123 
1.1800 
1.4074 
0.0647 
0.0978 
* Emerson and Cuming, Inc. 
Table I11 
1 2.64 
2'79 I 48 1.5612 0.0435 I 1.4761 1 0.0389 
I 96 
0.0892 
* Emerson and Cuming, Inc. 
5 
. 
0.0222 
0.0182 
0.0206 
1 0.0223 
I 1 0.0201 
1 0.0220 
Table I V  
WEIGHT WSS DATA FOR C U A R  VARNISH B-276* 
(125OC and t o r r )  
Time,  H r s .  
48 
96 
Time,  H r s .  
192 
S. W t . ,  g W t .  Loss, g W t .  Loss, '$ 
1.1956 0.0086 0.72 
1.7707 0.0095 0.54 
1.6003 0.0121 0.76 
1.0117 0.0099 0 .98  
s. W t . ,  g 
1.1778 
2.0229 
0.0233 
0.8092 
0.8341 
0.7937 
0.7838 
0.8442 
0.0096 0.82 
0.0121 0.60 
W t .  Loss, g W t .  Loss, $3 
2.81 
* Westinghouse E l e c t r i c  Corp., Micarta Div i s ion  
Samples of a s i l v e r - f i l l e d  epoxy pas t e  s o l d e r ,  Eccobond Solder  
56C/9, suppl ied by Emerson and Cuming, I n c . ,  w e r e  appl ied  t o  copper c o i l s  
by brushing, and cured f o r  2 hours a t  5OoC, according to  manufacturer ' s  
i n s t r u c t i o n s .  
t o  l e v e l  off a t  48 hours  (see Table V ) ,  bu t  understandably would be much 
g r e a t e r  w e r e  no t  such a g r o s s  amount of s i l v e r  p re sen t .  Since t h i s  i s  a 
The near ly-acceptable  weight l o s s  of t h i s  material appears  
unique and important material, the e f f e c t  of extended cu r ing  
checked. 
Table V 
WEIGHT IDSS DATA FOR ECCOBOND SOLDER 56C/9* 
(125OC and t o r r )  
1 1 I I 
w i l l  be 
* Emerson and Cuming, Inc .  
6 
FUTURE WORK 
Vacuum weight loss de termina t ions  v i a  s tandard ized  procedures w i l l  
be made on a cont inuing  b a s i s  i n  order  t o  e s t a b l i s h  l i m i t a t i o n s  f o r  speci- 
f i c a t i o n s  requirements f o r  var ious  polymeric materials. Coro l l a ry  s t u d i e s  
w i l l  be conducted v i a  thermogravimetry i n  o r d e r  t o  v e r i f y  and supplement 
t h e  d a t a  obtained by s tandard ized  procedures.  
Determinations of phys ica l  and chemical p r o p e r t i e s  of polymers w i l l  
be continued as requi red  f o r  incorpora t ion  i n t o  s p e c i f i c a t i o n s  requi re -  
ments and test procedures. 
7 
PHASE I1 - ENGINEERING INFORMATION 
WORK PERFORMED 
Fabr ica t ion  and assembly has been completed f o r  t h e  long-term m e -  
chanical-property test u n i t s .  The fou r  u n i t s ,  assembled on a s i n g l e  
support-and-control s t and ,  a r e  being checked-out for  vacuum ope ra t ion ,  
e l e c t r i c a l  c o n t i n u i t y ,  and thermal uniformity.  (A detailed d e s c r i p t i o n  
of t he  u n i t s  and a photograph w i l l  be presented i n  the  next  repor t . )  
The polymers i n  t h e  long-term tests w i l l  be checked p e r i o d i c a l l y  
f o r  any observable  e f f e c t s  of t he  thermal-vacuum environment (125OC and 
t o r r ) .  A t  t h e  terminat ion of a n  8-month exposure period (repre-  
s e n t a t i v e  of a f l i g h t  to  Mars), t h e  t e n s i l e  p rope r t i e s  of surv iv ing  ma- 
terials w i l l  be determined on an Ins t ron  machine. 
Three of the  u n i t s  soon w i l l  be loaded f o r  cons t an t  s t r a i n  tests 
wi th  materials which have been se l ec t ed  from p r i o r  work as those  most 
q u a l i f i e d  thus f a r  f o r  long-term spacec ra f t  use:  General  E l e c t r i c  e l a s -  
tomer SE-3604, DuPont e las tomer Viton A-4411A-990, and Goodrich elastomer 
Hycar-520-67-108-1. 
m a t e r i a l  i n  order  t o  e l imina te  poss ib le  cross-contamination i n  such a 
long-term exposure. Also,  i n  order  t o  prevent any poss ib l e  r a d i a t i o n  e f -  
fects ( f luorescent  l i g h t i n g  f i x t u r e s )  dur ing  long-term s t o r a g e ,  t he  g l a s s  
Loading of each u n i t  w i l l  be confined t o  a s i n g l e  
I t  b e l l  tubes" w i l l  be covered with aluminum s h i e l d s .  The f o u r t h  u n i t  i s  
temporar i ly  reserved f o r  s e l e c t i o n  of a s i g n i f i c a n t  m a t e r i a l  which may be 
subjec ted  e i t h e r  t o  cons t an t  s t r a i n  or cons tan t  load.  
Necessary modi f ica t ions  t o  a bas ic  vacuum console have been com- 
p l e t ed  for  the  accommodation of the r a p i d ,  maximum-VCM test assembly. 
The max-VCM u n i t  is  near  completion and w i l l  be placed i n  opera t ion  dur- 
i n g  t h e  next working per iod.  
maximum-volatile-condensable-material d a t a  on a weight basis f o r  both 
engineer ing  information and s p e c i f i c a t i o n s  requirements.  
I n i t i a l l y ,  t h e  max-VCM u n i t  w i l l  provide 
- 
A l t e r n a t i v e l y ,  
8 
t h e  u n i t  may be adapted t o  provide semi-quant i ta t ive  i d e n t i f i c a t i o n  of 
t h e  VCM which is re leased  by polymeric materials subjec ted  t o  a thermal- 
vacuum environment; work i s  underway on t h e  l a t te r  modi f ica t ion .  Mate- 
r ia ls  t o  be  t e s t e d  i n  t h e  max-VCM unit  w i l l  be s e l e c t e d  on t h e  b a s i s  of 
i n t e r e s t  t o  both phases of t h i s  program. 
Work is  cont inuing on t h e  assembly of t h e  "clam-shell' '  u n i t s  which 
w i l l  permit es tabl ishment  of VCM curves over long per iods  of t i m e .  I t  
may be pointed out  t h a t  t h e s e  assemblies w i l l  accommodate polymeric s a m -  
p l e s  of almost any conf igura t ion  (wi th in  s i z e  l i m i t a t i o n s ) ,  i . e . ,  f i l m s ,  
elastomers, t a p e s ,  e l e c t r o n i c  component assemblies  } etc.  
Mass s p e c t r a  have been obtained (CEC Model 21-10% mass spectrom- 
e ter)  of t h e  substances evolved from seve ra l  samples of General Electr ic  
Lexan (polycarbonates)  dur ing  t h e i r  exposure t o  t h e  thermal-vacuum en- 
vironment of 125'C and t o r r .  A sample i s  pumped overnight  i n  a 
modified i n l e t  s y s t e m  a t  ambient temperature t o  remove s u r f a c e  gases  
and moisture; then  it is  brought quickly t o  a temperature  of 125OC and 
t h e  evolved vapors are immediately scanned. S ince  t h e  s p e c t r a  f o r  t h e s e  
materials have not y e t  been completely i n t e r p r e t e d }  it has not been de- 
termined whether t h e  Lexan i t s e l f  is  decomposing under t h e s e  cond i t ions ,  
but  a t  least 3 o r  more extraneous materials are r e a d i l y  i d e n t i f i a b l e ,  
e . g . ,  w a t e r ,  p l a s t i c i z e r ,  e t c .  
I n  s i t u  measurements of t h e  changes i n  cons tan t  and i n t e r m i t t e n t  - -  
stress r e l a x a t i o n  are underway i n  t h e  thermal-vacuum environment of 
125'C and 
(24/480) and SE-3713 (24/480). 
f i r s t  annealed i n  a i r  f o r  1 hour a t  15OoC,  are being s t o r e d  i n  t h e  same 
environment f o r  c reep  tests under 600 p s i  loading .  Add i t iona l ly ,  un- 
loaded con t ro l  specimens of a l l  materials are being s t o r e d  f o r  pos t - t e s t  
obse rva t ions .  Prel iminary outgassing of materials a t  5OoC w a s  completed 
after about 145 hours .  
t o r r  f o r  General Electric s i l i c o n e  elastomers  SE-3613 
Samples of Lexan (General E l e c t r i c ,  
9 
FUTURE WORK 
Work w i l l  be completed on the i n s t a l l a t i o n  and ope ra t ion  of t he  
assembly f o r  r ap id ,  maximum-VCM determina t ions ,  and assembly of t h e  
VCM clam-shell  u n i t s  w i l l  be acce le ra t ed .  
Long-term (8-month) mechanical p r o p e r t i e s  tests w i l l  be i n i t i a t e d  
f o r  s e v e r a l  e las tomers .  
Work w i l l  cont inue on t h e  s p e c t r a l  s t u d i e s  of polymers exposed t o  
a thermal-vacuum environment and on the  measurements of changes f o r  se- 
l ec t ed  mechanical p r o p e r t i e s  of polymers dur ing  t h e i r  exposure t o  a 
thermal-vacuum environment . 
10 
I 


Polymers for spacecraft hardware materials specifications and engineering information Monthly technical progress report no. 18, Nov. 10 - Dec. 9, 1965

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