Procedures for fluorination and alkylation of glass fabric for subsequent use in production of laminate

Bertolucci, M. D.

Chamberlin, D. L., Jr.

Christensen, M. V.

English

NASA Technical Reports Server

May 9, 1967 
Report No. 12 
Quarterly Progress Report No. X January 1 to March 31, 1967 I 
STUDY OF BONDING €EWEEN GLASS AND PLASTIC 
IN GLASS - RE I NFORCED PLASTICS - - EXTENDED WORK 
By: David L. Chamberlain, Jr. 
Mark V .  Christensen, and 
Michael D. Bertolucci 
SRI Project FRU-4525 
Prepared f o r :  
National Aeronautics and Space Administration 
Lewis Research Center 
2100 Brookpark Road 
Cleveland, Ohio 44135 
Attn: D r .  Tito Serafini 
Contract NASr-49 (14) 
Approved : 
A. G. Brown 
Associate Executive Director 
Physical and Industrial Sciences 
4 copy No. 
https://ntrs.nasa.gov/search.jsp?R=19670021481 2020-03-12T11:05:12+00:00Z
1 
I * .  
INTRODUCTION 
The general objective of this research program is to evaluate the 
effect of deliberate and known chemical bonding between the glass 
reinforcement and the plastic matrix of a glass-reinforced plastic com- 
posite material. 
Previous described studies of the methods by which 
siliceous surfaces can be modified with organic groups that are bonded 
to surface-based silicon atoms by silicon-carbon bonds. These surface- 
modifying organic groups can be chosen for specific interaction with the 
resin matrix of the composite material. Surface modification was accom- 
plished in two steps: 
(1) Reactive-intermediate groups such as chlorine atoms, fluorine 
atoms, or alkoxy1 groups were bonded to surface-based silicon 
at oms. 
(2) Reactive-intermediate groups were converted to surface- 
modifying organic groups by reaction with an organometallic 
compound. 
The objectives of the present phase of this project are (1) to 
evaluate the effects of surface modification upon a realistic composite 
material (such as a filament-wound NOL ring or a woven glass cloth lami- 
nate), (2) to study optimum characteristics for surface-modifying groups 
and improved methods for obtaining them, and (3 )  to study methods for 
application of surface modification to reinforcement materials other than 
glass and silica. 
This is the fourth quarterly report for this phase of the project. 
Work during this quarter was directed primarily toward the preparation 
of experimental laminates for evaluation. 
1 
SUMMARY 
Procedures for the fluorination and alkylation of glass fabric f o r  
subsequent use in the production of laminates have been established. 
Several test specimens were made from untreated glass fabric in 
order to perfect a technique for the production of laminates. The lay-up 
procedure for the specimens to be used in the evaluation studies has been 
chosen. 
A detailed study of the effect of surface modification upon the 
position of the Si-0 fundamental stretching frequency was made. The 
study required attenuated total reflection (ATR) spectral techniques 
for the attainment of highly resolved spectra. 
2 
DISCUSSION AND EXPERIMENTAL 
F luor ina t ion  of Glass Fabr ic  
F luo r ina t ion  of a g l a s s  f a b r i c  s e rves  a twofold purpose, F i r s t ,  
r e s i d u a l  carbon remaining a f t e r  the  manufacturing procedure is burned 
o f f  wi th  f l u o r i n e  gas leav ing  a c lean  su r face .  Second, r eac t ive -  
in te rmedia te  groups (-di-F) formed on t h e  su r face  can be converted t o  a 
d e s i r e d  su r face  modifying group (-Si-R). 
I I 
I 
Table  I shows t h e  r e s u l t s  of carbon ana lyses  before  and a f t e r  
f l u o r i n a t i o n  of t h e  "E"-glass f a b r i c s  which w i l l  be used f o r  laminate  
product ion.  The s m a l l  v a r i a t i o n  i n  carbon content  a f t e r  f l u o r i n a t i o n  
of t h e  t h r e e  samples i n d i c a t e s  t ha t  t h i s  is  not s u r f a c e  contamination 
but carbon which is  trapped i n  the  mat r ix  of t h e  "Etr-glass f i b e r .  
f o r e ,  the f i r s t  purpose of f l u o r i n a t i o n  is  met--the removal of su r f ace  
contamination. 
There- 
Table I 
CARBON ANALYSIS OF GLASS FABRICS 
BEFORE AND AFTER FLUORINATION 
G l a s s  
Fabrica 
~ ~ _ _  
2P181b 
1P8lC 
1P8 1 
Carbon Analysis  
before  
F luo r ina t ion  
(ppm carbon) 
215 
238 
247 
Carbon Analysis 
a f t e r  
Fluor i n a t  ion  
(ppm carbon) 
89 
88 
91 
Remarks 
Samples w e r e  degassed 
a t  5 x 106 mm Hg and 
100°C f o r  24 hours 
before  carbon a n a l y s i s .  
2P181 and 1P81 "E"-glass f a b r i c  suppl ied by Coast Manufacturing 
and Supply Co., Livermore, C a l i f .  
a 
b2P181 suppl ied wi th  s t a r c h  o i l  s i z i n g .  
n 
C 1P81 hea t  cleaned and washed t o  n e u t r a l  pH by manufacturer.  
3 
Fluoride analysis for 1P81 glass fabric and Cab-0-Si1 after fluori- 
nation and high vacuum degassing indicated surface population of 5.6 and 
5.3 fluorine atoms per 100 A ,  respectively. The presence of polyvalent 
cations should result in ionic fluorides and a somewhat higher fluoride 
population. Since the 1P81 glass fabric was water washed to neutral pH, 
its surface should contain few, if any, cations such as Ca++, and there- 
fore approximate the surface of silica. This appears to be the case since 
the fluorine atom population for both Cab-0-Si1 and 1P81 glass fabric are 
very nearly the same. 
0 
e 
Alkylation Reactions 
A series of fluorinated glass fabric samples was alkylated with 
selected organometallics to gain information about the generation of 
organic surface groups with terminal substituents that may undergo reac- 
tion with the resin phase. The data on these samples are summarized in 
Table 11. 
Table I1 
ALKYLATION REACTIONS OF FLUORINATED GLASS FABRICS 
Glass 
Fabric 
1. 2P181 
2. 1P81 
3. 1P81 
Reagent 
Allyl-magnesium 
bromide 
Allyl-magnesium 
bromide 
Pentane-l,5-di- 
magnesium bromide 
followed by 
oxidation of the 
terminal 
-C% -MgBr group 
Solvent 
Tetrahydrofuran 
Diethyl ether 
Diethyl ether 
Product 
(-Si = Silicon 
Atom in 
Glass Surface) 
H H  
I I  
-Si-C& -C=CH 
H H  
I 
-si-ck -c=h 
-Si- (m -OH 
Carbon 
Ana 1 y s is 
Groupso 
per 100 A 
5.52 
18.1 
12.1 
The terminal hydroxyl group on a five-carbon chain (No. 3, Table 11) 
and 1P81 glass fabric will be used f o r  the preparation of epoxy laminates 
in the present work. 
4 
Since d i e t h y l  e t h e r  is  a poor so lvent  f o r  a lkoxides  and polymers of 
acetone,  t h e  high surface population of groups ( N o s .  2 and 3,  Table 11) 
can be reasonably a t t r i b u t e d  t o  organic  res idues  which were not  removed 
by t h i s  so lven t .  Polymers of acetone can poss ib ly  be formed by a l d o l  
condensation catalyzed by bas i c  magnesium alkoxides  formed i n  t h e  Grignard 
r e a c t i o n .  In  f u t u r e ,  t e t rahydrofuran  w i l l  r ep l ace  d i e t h y l  e t h e r  i n  t h e  
pentane-1,5-dimagnesium bromide system and acetone w i l l  be omit ted from 
t h e  f a b r i c  washing procedure. 
Laminate Prepara t ion  
To i n v e s t i g a t e  var ious  lay-up techniques,  s e v e r a l  4 i n .  x 4 i n .  test 
specimens were made us ing  unt rea ted  2P181 glass f a b r i c .  The r e s u l t s  
obtained from four  8-ply laminates and one 14-ply laminate ,  using d i f -  
f e r i n g  lay-up techniques,  w e r e  very s a t i s f a c t o r y .  The ca l cu la t ed  void 
conten ts  of t h e  8-ply specimens ranged from 0 . 1  t o  1% by volume. The 
ca l cu la t ed  va lue  f o r  t h e  14-ply specimen w a s  10%. 
The r e s i n  formulat ion used f o r  t h e  test laminates  i s  as fol lows:  
100 p a r t s  Epon 825, 9 1  p a r t s  Nadic Methyl Anhydride, and 0.3% by weight 
(based on t o t a l  charge) N-benzyldimethylamine i n i t i a t o r .  
The 6 i n .  x 6 i n .  x 0.125 in .  12-ply laminates  which w i l l  be used 
f o r  t h e  eva lua t ion  s t u d i e s  w i l l  be prepared from t h e  above r e s i n  formu- 
l a t i o n ,  us ing  t h e  fol lowing lay-up procedure suggested by E a k i ~ ~ . ~  The 
r e s i n  is  divided i n t o  f i v e  equal por t ions ,  t h e  f i r s t  of which i s  placed 
on a shee t  of cel lophane.  Three 6 i n .  x 6 i n .  squares  of g l a s s  f a b r i c  
are placed on t h e  r e s i n ,  and the  squares  are covered wi th  another  po r t ion  
of  t h e  epoxy formulat ion.  This procedure i s  repeated i n  3-ply increments 
u n t i l  t h e  lay-up conta ins  12 plys .  The cel lophane i s  folded over t h e  
laminate  and sea led  on t h r e e  s ides .  The f o u r t h  s i d e  is folded loose ly  t o  
a l low vent ing  of gases .  The lay-up is then  c a r e f u l l y  and gen t ly  r o l l e d  
t o  work t h e  r e s i n  i n t o  t h e  f a b r i c  and t o  d i s p l a c e  t rapped a i r .  The lay- 
up i s  placed i n  a cold laminating p res s  and t h e  p l a t e n s  closed very 
slowly aga ins t  0 .125 i n .  gauge blocks. The p res su re  is  increased t o  
125 ps ig ,  and t h i s  p re s su re  i s  maintained throughout t h e  cu r ing  cyc le  
a t  240' F. 
5 
I n f r a r e d  S tudies  of Surface Modified S i l i c a  
I n  t h e  course of o t h e r  work i n  t h i s  l abora to ry ,  an in f r a red  s p e c t r a l  
technique w a s  deve lope8  which allows semi-quant i ta t  i v e  i n v e s t i g a t i o n  of 
broad, i n t ense  absorp t ion  regions such as t h e  S i -0  s t r e t c h i n g  frequency 
of s i l i c a .  Spec t r a l  d a t a  a r e  obtained f o r  inorganic  s o l i d s  by applying 
a t h i n  f i l m  of d r y ,  f i n e l y  divided s o l i d ,  e .g . ,  Cab-0-Sil, t o  t h e  f a c e  
of a s i n g l e  r e f l e c t i o n  KRS-5 ATR pr i sm.*  
s e n s i t i v i t y  and 5X s c a l e  expansion. The high degree of r e s o l u t i o n  
obta ined  allows assignment of s p e c t r a l  band p o s i t i o n s  reproducibly wi th in  
* 2 cm-l . 
The spectrum is  run a t  high 
From t h e  i n f r a r e d  s p e c t r a  of a s e r i e s  of su r f ace  modified s i l i c a s  
it appears  t h a t  the  frequency a t  which l a t t i c e  Si-0 bonds of Cab-0-Si1 
absorb i s  r e l a t e d  t o  the s u r f a c e  environment. Using unt rea ted  Cab-0-Si1 
(175-180 I# /g s p e c i f i c  s u r f a c e ) ,  conta in ing  s u r f a c e  s i l a n o l  groups, as a 
r e fe rence  s i l i c a ,  i t  was shown tha t  su r f ace  modi f ica t ion  r e s u l t s  i n  a 
s h i f t  (A value)  i n  t h e  p o s i t i o n  of t h e  absorp t ion  band due t o  asymmetric 
S i -0  s t r e t c h i n g .  The d i r e c t i o n  of t h e  s h i f t  ( p o s i t i v e  or negat ive A 
value)  i s  r e l a t e d  t o  t h e  tendency of t h e  su r face  modifying groups t o  
withdraw or  donate e l e c t r o n s .  Pos i t i ve  s h i f t s  ( t o  lower f requencies )  
r e s u l t e d  from e l e c t r o n  donat ing groups such a s  methoxy, and negat ive  
s h i f t s  ( t o  higher  f requencies )  r e su l t ed  from e l e c t r o n  withdrawing groups 
such a s  halogen. N o  s h i f t  i n  t he  Si-0 p o s i t i o n  w a s  observed with methyl 
or phenyl a s  surface-modifying groups. 
A study of t hese  e f f e c t s  should c o n t r i b u t e  t o  a b e t t e r  understanding 
of the chemistry of s u r f a c e  modif icat ion,  and of t h e  r o l e  t h a t  su r f ace  
modified inorganic  f i b e r s  may play i n  t h e  product ion of  improved re inforced  
m a t e r i a l s .  A d e t a i l e d  s tudy of t h i s  na tu re  must be reserved f o r  a f u t u r e  
e f f o r t .  
Hydrogen bonding of po la r  adsorbates  t o  t h e  s u r f a c e  Si-OH groups has 
t h e  o v e r a l l  e f f e c t  of withdrawing e l e c t r o n s  from t h e  su r face .  The e f f e c t  
i s  observed a s  a s h i f t  i n  t h e  l a t t i c e  Si-0 absorp t ion  band. Table I11 
* 
Connecticut Instrument Corporation s i n g l e  ATR assembly. 
6 
Y 
Simple Untreated 
S i 0  l a t t i c e  1080 
fre‘quency (cm-1 ) 
summarizes t h e  effect  of adsorbed phenol (500 mole % on S i & )  on t h e  
p o s i t i o n  of t h e  Si-0 s t r e t c h i n g  frequency of Cab-0-Si1 1167. 
A B C Control  
A 
1085 -5 1083 -3 1078 +2 1079 +1 
- A - A - A - 
Table I11 
Samples A-C i l l u s t r a t e  t h e  e f f e c t  of adsorbed phenol and t h e  s tep-  
w i s e  a t tempts  t o  remove t h e  adsorbate.  
Sample A r ep resen t s  t h e  ma te r i a l  a f t e r  absorp t ion  of phenol and 
vacuum degassing a t  1 mm Hg a t  room temperature f o r  1/2 hour. Sample B 
is an a l iquo t  of A a f t e r  i t  w a s  r i go rous ly  degassed a t  1 mm H g  a t  7OoC 
f o r  66 hours.  Sample C is  an a l iquot  of A which w a s  thoroughly washed 
wi th  benzene and vacuum d r i e d .  The con t ro l  sample r ep resen t s  Cab-0-Si1 
a f t e r  washing with benzene and vacuum drying.  
Replacement of t h e  su r face  hydroxyl group wi th  t h e  more e l ec t ro -  
nega t ive  ch lo r ine  atom has  t h e  o v e r a l l  e f f e c t  of s h i f t i n g  t h e  Si-0 
absorp t ion  t o  higher  f requencies  (1091 cm’l , A = -11). 
repor ted  earlierJ6 is  present ly  a t t r i b u t e d  t o  t h e  e l e c t r o n  withdrawing 
tendency of t h e  halogen. Hydrolysis of t h e  su r face  Si-C1 groups t o  Si-OH 
groups r e s t o r e s  t h e  l a t t i c e  Si-0 band t o  i ts  o r i g i n a l  pos i t i on ,  as can be 
seen  i n  Table I V .  
This  e f f e c t  , as 
It has been observed t h a t  replacement of su r face  hydroxyl groups 
wi th  less polar  methyl, phenyl, or p-hydroxyldodecyl groups does not  
a l t e r  t h e  pos i t i on  of t h e  l a t t i c e  Si-0 band wi th in  t h e  l i m i t s  of  sens i -  
t i v i t y  of t h e  method. 
Methoxylation of t h e  surface causes a l a r g e  s h i f t  i n  t h e  p o s i t i v e  
d i r e c t i o n .  This  i s  understandable on t h e  b a s i s  t h a t  t h e  h ighly  po la r i z ing  
-OC% group may se rve  as a n  e l ec t ron  donor t o  t h e  s i l i c a  su r face .  The 
7 
L 
A (cm‘l ) 
r e s u l t a n t  increase  i n  e l e c t r o n  dens i ty  between su r face  S i  and 0 l a t t i c e  
atoms should be r e f l e c t e d  i n  a s h i f t  of t h e  Si-0 s t r e t c h i n g  frequency a t  
1080 cm” t o  longer  wavelengths. 
t h e  e f f e c t s  of a l k y l a t i p n  and a lkoxyla t ion  on t h e  pos i t i on  of t h e  l a t t i c e  
S i -0  s t r e t c h i n g  frequency i n  t h e  high-surface Cab-0-Sil. 
Table I V  i l l u s t r a t e s  t h e  magnitude of  
Table I V  
~~ ~~~ 
C-H S t r e t ch ing  
Pos i t  iona 
( c m - l )  
EFFECT OF SURFACE MODIFICATION ON LATTICE Si-0 FREQUENCY 
+1 
+2 
Surface  Species  I si-0 (cm-1) 
3082, 3062 
-C% 
con t ro l  
-0CH3 
con t ro l  
b hydrolyzed 
hydro 1 yzedC 
1081 
1081 
1073 
1081 
1075 
1079 
-% Y 
con t ro l  
1079 
1078 
OH 
- 0 C I L d L  %1 
con t ro l  
hydrolyzed 
1078 
1081 
1082 
-1 
-1 
2979, 2959, 2856 
 
+2 I 2964, 2932, 2860 
-1 
-2 
+7 
-1 
+5 
+1 
2993, 2961, 2859 
-- 2965, 2862 
2994, 2960, 2858 
-- 28 59 -- 
a Values obtained from transmission s p e c t r a  of  t h i n  powder samples 
between N a C l  d i s c s  on a l i n e a r  wave number Perkin Elmer  221 
spectrophotometer.  
bSample boi led i n  h0 for 20 min and d r i e d .  
C Sample boi led i n  d i l u t e  NaOH, r in sed  wi th  d i l u t e  HC1, then r in sed  
wi th  &O, and d r i e d .  
Alkylated su r faces  were prepared through t h e  r e a c t i o n  of t h e  appro- 
p r i a t e  metal a l k y l  wi th  halogenated Cab-0-Sil. The con t ro l  samples 
received t h e  i d e n t i c a l  treatment except f o r  t h e  halogenat ion s t e p .  
8 
I 
rL 
't 
4 
p-hydroxydodecoxylated s i l i c a  w a s  prepared from t h e  BF3-etherate 
ca ta lyzed  r e a c t i o n  of dodecene oxide wi th  the s i l a n o l  su r face  of Cab-O-Sil. 
The con t ro l  was a s i m i l a r  r eac t ion  uncatalyzed.  
Methoxylation of t h e  Cab-0-Si1 s u r f a c e  w a s  c a r r i e d  out  i n  a s t a i n l e s s  
s t e e l  high p res su re  bomb r e a c t o r  a t  200' C f o r  21 hours. The c o n t r o l  w a s  
obtained by b o i l i n g  Cab-&Si1 i n  %OH f o r  f i v e  minutes ,  The appearance 
of weak C-H bonds i n  t h e  con t ro l  i n d i c a t e s  a small  degree of hydroxyl 
replacement r e s u l t i n g  from t h i s  m i l d  t rea tment .  The presence of C-H 
bonds i n  t h e  t ransmission spectrum w a s  a p o s i t i v e  i n d i c a t i o n  of t h e  sur-  
face environment. The i n t e n s i t y  of these bonds i n  r e l a t i o n  t o  t h e  l a t -  
t i c e  S i -0  i n t e n s i t y  w a s  used as'a q u a l i t a t i v e  measure of t h e  ex ten t  of 
s u r f a c e  coverage and t h e  degree of hydro lys is .  No attempt has been made 
t o  account f o r  t h e  s m a l l  d i f f e r e n c e s  i n  t h e  C-H f requencies  t h a t  appear 
i n  these samples. 
Ana ly t i ca l  S tud ie s  
F luor ide  ana lyses  were c a r r i e d  out  us ing  an Orion f luo r ide - ion  e lec-  
t r o d e  and a Corning Model 12  expanded s c a l e  pH meter.  The g l a s s  sample 
w a s  hydrolyzed i n  2N NaOH. An equal volume of 2N % S Q  w a s  added, and 
t h e  e l e c t r o d e  response t o  t h e  s o l u t i o n  is  read i n  m i l l i v o l t s .  The corre- 
sponding F- concent ra t ion  is  determined from a s tandard curve for f l u o r i d e  
ion  i n  1 N  N%SQ s o l u t i o n .  
- - 
- 
FUTURE WORK 
. The p repa ra t ion  and eva lua t ion  of experimental  laminates  w i l l  
r ece ive  a l l  e f f o r t  expended i n  t h e  remaining work per iod.  
9 
. .I . - 
REFERENCES 
1. D. L. Chamberlain, Jr., A Study of Bonding Between Glass and Plastic 
in Glass-Reinforced Plastics, Phase I, Summary Technical Report 
No. 1, Contract NASr-49(14), July 31, 1964. 
2. D. L. Chamberlain, Jr., A Study of Bonding Between Glass and Plastic 
in Glass-Reinforced Plastics, Phase 11, Summary Technical Report 
No. 2, Contract NASr-49(14), November 15, 1965. 
3. D. L. Chamberlain, Jr., A Study of Bonding Between Glass and Plastic 
in Glass-Reinforced Plastics, Extended Work, Quarterly Report No. IX, 
Contract NASr-49(14) , March 23, 1967. 
4. W. J. Eakin, Avco Corporation, private communication. 
5. D. L. Chamberlain, Jr., M. Bertolucci, and M. V. Christensen, 
Mechanism of Adhesion to Teeth, Progress Report for the Seventh 
Quarter of Work, Contract No. A2(230)PH 43-65-82, January 25, 1967. 
6. D. L. Chamberlain, Jr., A Study of Bonding Between Glass and Plastic 
in Glass-Reinforced Plastics, Extended Work, Quarterly Report 
No. XIII, Contract NASr-49 (14) , December 28, 1966. 
10 


Study of bonding between glass and plastic in glass-reinforced plastics - Extended work Quarterly progress report, 1 Jan. - 31 Mar. 1967

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