"B -

DEVELOPMENT OF IMPROVED H.E. ADHESIVES SYSTEMS

Adhesive System Studies:

and bonding methods f o r their properties and adaptability to production.

A continuous survey of commercially available adhesives

H. P. Christiansen

Quarterly Report for January, February, March, 1964

Engineering Order No. 814-00-002

MASTE

U

- 12 -

Optimum mix of a l l y l g lyc idyl e t h e r , needed as a th inner f o r Aerobond H-7, appears

t o be about 10 pph AGE which reduces v i s c o s i t y t o 165 cps.

a l shear s t r e g n t h t o 930 in- lbs/ in2 versus 1616 in- lbs/ ina i n tests t h i s q u a r t e r

and values as low as 520 in- lbs/ in2 reported previously.

This reduces to r s ion -

Water permeabi l i ty was measured aga in f o r Adiprene, Perm-A-Lon and Estane; Aero-

bond H-7 was a l s o measured us ing a f i l t e r pape r backing material. The va lue f o r

Estane was lower than i n previous tests, 0.27 mg/cm2/hour versus 1.08 and 1.15

mg/cn? hour repor ted earlier.

The d i s c e x t r u d a b i l i t y test w a s set up and prel iminary da ta were gathered f o r

t h ree l o t s of IX-02-1 and seve ra l t i l e mater ia ls .

The experiment t o d e t e c t de f i c i enc ie s i n Adiprene L-100 a s an adhesive f o r H.E.

caused by aging i s i n i t s t h i r d year.

d e t e r i o r a t i o n ; but shear s t r e n g t h r e s u l t s were quest ionable .

breakage occurred i n t h e H.E.

Tens i le s t r eng th r e s u l t s i nd ica t ed no

I n bo th cases ,

PREVIOUS APPLICABLE WORK

I

Prel iminary s t u d i e s t o eva lua te Aerobond H-7 f o r use as a product ion adhesive

are nea r ly completed.

p rope r t i e s , and w i l l wi thstand a thermal shock test .

although pot l i f e is a l i t t l e s h o r t but extendible .

Aerobond H-7 i s compatible wi th H.E., has adequate phys i ca l

The set pe r iod i s d e s i r a b l e ,

Viscos i ty adjustment s t u d i e s

-. .-

3

.'

I

- 13 - have been s t a r t e d ; a l l y l g lyc idy l e t h e r w i l l reduce Aerobond's r e s i n v i s c o s i t y

from 600 t o 105 cps a t 75'F. , help form a t h i n f i l m and an 80% HMX repair mix

which de tona tes a t 6940 m/sec.

Thin, smooth, dimple-free f i lms of Adiprene, Perm-A-Lon, Kel-F, and Estane have

been prepared and t h e i r water permeabi l i t i es measured. Perm-A-Lon and Kel-F

are very impermeable, whi le Estane and Adiprene are permeable.

tests were run f o r each of t he f i l m s , bu t were not successful. Perm-A-Lon, Kel-F,

and Estane, being thermoplast ics , r equ i r e evaporat ion of a so lvent t o se t up; t h e ..

c e n t e r of each of t h e samples were s t i l l s o f t , some even a f te r a three-week cure.

A smooth f i l m of Aerobond was prepared, but due t o Aerobond's bonding c h a r a c t e r i s t i c s

could not be s t r i p p e d ; t he re fo re , no permeabili ty data .

Torsional shear

An experiment designed f o r f ive-year durat ion t o d e t e c t any def ic iency i n Adiprene

L-100's e f f e c t i v e n e s s as an adhesive f o r H.E. caused by aging began t h r e e years ago.

A f t e r two yea r s , according t o shear and t e n s i l e test r e s u l t s , the glue bond had

not d e t e r i o r a t e d and, f o r a l l specimens, the breakage occurred i n the H.E.

DIS CUS SI ON

Aerobond H-7

Aerobond H-7, a n epoxy manufactured by Adhesive Engineering, San Carlos, Cal i forn ia ,

i s being considered f o r u se as a production adhesive and t e s t i n g has continued

over t h e p a s t several quar te rs .

and tests become ava i l ab le .

Additional da ta are being generated as new uses

Previously, t h e t o r s i o n a l shear s t r e n g t h of Aerobond

L J

- 14 -

was repor ted as 520 i n - l b s / i n a , bonding aluminum specimens t o an aluminutn p l a t e .

Rerunning t h i s test y i e lded the fol lowing r e s u l t s :

Tors iona l Shear S t rength ( in- l b s / ind )

0.002 inch Gap - Room Temperature Cure

C i rcu la r Specimens Bonded t o F l a t P l a t e s

1680 1650 1584 1584 1584

A l - to-IX-04- 1'

340 280 328 3 10 300 305

Avg . 1616 Range 96

309 60

' A l l samples broke i n t h e H.E.

Viscos i ty adjustment s t u d i e s have been s t a r t e d i n an e f f o r t t o r e a l i z e all the

p o s s i b i l i t i e s of Aerobond H-7 a s an adhesive i n H . E . app l i ca t ions . Viscos i ty

adjustment i s of i n t e r e s t wi th Aerobond H-7 f o r i t s use as a patch ma te r i a l and

poes ib l e a p p l i c a t i o n a s a coat ing. Of those t r i e d , a l l y l g lyc idy l e t h e r (AGE)

has been found t o be t h e most e f f e c t i v e d i l u e n t f o r Aerobond H-7 i n that 20 pph

AGE w i l l reduce i t s v i s c o s i t y t o 105 cps a t 76'F. Torsional shear tests were

made on var ious mixes of Aerobond and AGE t o determine t h e e f f ec t iveness of 5,

10, and 20 pph AGE on i t s s t r eng th . The curves in Figure 1 show t h e r e s u l t s .

Increas ing amounts of AGE reduce Aerobond's s t r e n g t h much more than v i scos i ty .

It appears t h a t 10 pph AGE would be s a t i s f a c t o r y f o r most uses of Aerobond; i t s

s t r e n g t h - f a r exceeds t h a t of H . E .

.. 31.

9

9

0 - 15 - Viscos i ty adjustment of Aerobond H-7 was s t a r t e d i n connection wi th a s tudy t o

f i l l i t wi th HMX f o r u s e . a s a pa tch m a t e r i a l t o r e p a i r H.E. Previous work

included f i l l i n g Aerobond/AGE w i t h HMX (80%), c a s t i n g i n t o ra te s t i c k s and

f i r i n g . The material d id de tona te ( a t 6940 m/sec), -but t he set per iod is

approximately 24 hours. A t f u l l cure , t h e torsional. shea r s t r e n g t h is only 30

in - lbs / ina , a value which is r a t h e r r e s t r i c t i v e . ._. . . ..

Samples of Aerobond H-7 were run w i t h PBX 9404 and Lx-04-1 f o r D i f f e r e n t i a l

Thermal Analysis ; t hese r e s u l t s i n d i c a t e , as d i d t h e Gas Chromatograph, that

Aerobond H-7 is s t a b l e wi th H.E.

. .

The'curves are shown %n Figures 2 and 3.

I

. .",.

. .

. -.. .

.. ..

3 3 1 1

_. - 16 -

FIGURE 1.

1600

1400

1200

1000

800

6 00

, -

400

200

0 10 15 20 0 5

P P H AGE I N AEROBOND H-7

600

500

io0

IO0

00

30

EFFECT O F ALLYL G i Y C I D Y L ETHER UPON THE STRENGTH O F AEROBOND H-7

+3

+2

+L

0

-1

- 2

+3

+2

+I

0

-1

-2

u’

FIGURE .!

I I

I I I f

I

t I I I I - I I ! I I

I -r- ..d. -4----r.-

I I

.-\EROBOSD H - i t LS-04-1 ! ‘

TEMPER ATUR E. ( ’ C . )

TEMPEHXTUR E. ( * C . )

- 17 -

U

- 18 -

H.E. Coating

A study i s cont inuing t o eva lua te materials f o r coa t ings f o r H.E. sur faces . It

has been shown t h a t such a coa t ing would be advantageous, p r imar i ly f o r pro tec t ion

aga ins t mechanical abuse--mainly abrasion. Several coa t ings are being s tudied ,

express ly as t o t h e i r permeabi l i ty t o moisture. Some t o r s i o n a l shea r s t r eng th

tests have been t r i e d , but these have been unsuccessful.

The water permeabi l i ty test i s pa t te rned a f t e r A.S.T.M. D-697 i n which the water

loss through a f i l m i n ques t ion i s measured a f t e r s to rage i n d e s i c c a t o r f o r 24

hours. Water permeabi l i ty va lues f o r Adiprene, Kel-F, Estane, and Perm-A-Lon

were measured previous ly , bu t t h a t f o r Aerobond H-7 could not be measured as a

f i l m could no t be prepared. Aerobond bonded s o w e l l t o a l l su r f aces t r i e d t h a t

i t could not be s t r i p p e d without t e a r i n g i t a p a r t . To avoid t h i s s t r i p p i n g

problem, Aerobond w a s sprayed on a shee t of f i l t e r p a p e r then the water loss was

measured through both. For comparison, f i lms of Adiprene and Perm-A-Lon were a l s o

prepared i n th$s manner. These va lues a r e l i s t e d below:

Water Permeabi l i ty

I

Materia 1

F i l t e r Adip rene Perm- A- Lon Adiprene F i l t e r Paper Perm-A-Lon F i l t e r Aerobond H-7 Estane

(mg/cd /hr )

5.78 .38 .03 1.00 .03 .19 .27

The va lues f o r Adiprene and Perm-A-Lon were comparable t o those obtained earlier,

although i t appears t h a t t h e Adiprene f i l m on f i l t e r paper w a s of i n f e r i o r qua l i ty .

*. . . * - 19 -

The only s ta tement t h a t can be made f o r t he Aerobond f i l m is t ha t i t is l e s a

permeable than Adiprene, bu t i t may be poss ib l e t o ob ta in a b e t t e r test.

Estane was rechecked because the va lues obtained l a s t q u a r t e r were quest ionably

high s ince Estane was procured f o r i t s 'rlow" water permeabi l i ty .

va lue (0.27 mg/cma/hr) is not extremely OW, i t is much b e t t e r than previous

da ta (1.08 and 1.15 mg/cm'/hr).

Although the

The M l l o n tester w a s i n s t a l l e d l a te t h i s qua r t e r . It w a s purchased f o r t h e

' purpose of developing a p e e l t e s t . t o determine t h e set per iod of S i l a s t i c 140

which i s . t o be used i n a program t o bond a s i l i c o n e rubber w a i s t band t o PBX 9404. I

It had a l s o been hoped t h a t the pee l test could be used as a I method of eva lua t ing

the f i lms used t o coa t unbound H.E. su r f aces , s i n c e the t o r s i o n a l shea r test

has proved t o be v n s a t i s f a c t o r y f o r ma te r i a l s t h a t r e q u i r e evapora t ion of a

so lvent t o o b t a i n optimum prope r t i e s . Prel iminary tests w e r e made bonding 1/16-

inch th i ck rubber s t r i p s t o aluminum.plates as s p e c i f i e d by A.S.T.M. D-903-49.

A ske tch of t h i s se tup is shown i n Figure 4.

t e s t e d ; r e s u l t s were as fol lows:

Adiprene and Aerobond H-7 were

Pee l 'S t rengths - . .

( l b s / i n of width)

Rubber-to-A1 Bonded w i t h Aerobond H-7

3 2 5

27 18 30

Avg - 14

Rubber-to-A1 Bonded w i t h Adiprene E 1 6 7

8 1 7 10 13 11 12 10

.- .._ -

' 2 5 . 15 12 -

. : ..

I

W

Figure 4

I

Grip

Pee l Test Setup

I . . ... . . .~ -

Thick Neoprene

Grip

0 ?

u'

- 2 1 - As s h a m by the r e s u l t s above, t he va lues va r i ed considerably.

not t r e a t e d p r i o r t o bonding, apparent ly oil or d i r t was present on some samples.

The r e s u l t s were v a r i e d somewhat by s t r e t c h i n g of the rubber which i n t u r n slowed

t h e speed a t which the sample was pul led apa r t . New f l e x i b l e ma te r i a l s and

methods of bonding w i l l be s tud ied i n an attempt t o r e f i n e the test.

The rubber was

Disc Test

The d i s c e x t r u d a b i l i t y test was set up i n order t o measure t h e r e l a t i v e extrud-

a b i l i t y of LX-02-1 and o the r p a s t e explosives on d i f f e r e n t su r f aces , a l s o t o

measure between-lot d i f f e rences i n LX-02-1. This tes t has been used a t LRL'

previous ly t o compare d i f f e r e n t t i l e materials.

ing a 3-gram sample of explosive (LX-02-1) under a fo rce of 2000 pounds f o r a

per iod of f i v e minutes.

The test c o n s i s t s of compress-

The diameter of t he r e s u l t a n t d i s c is then taken as a

measurement of i t s e x t r u d a b i l i t y . The test may be run a t two temperatures,

25OC. and 5OoC. LRL has run the test a t both temperatures, but i t appears that

i nc reas ing the temperature does not improve t h e e x t r u d a b i l i t y of LX-02-1

s i g n i f i c a n t l y . * .

Prel iminary tests were made on t h r e e batches of IX-02-1 and f o r su r face materials

t h a t were immediately ava i l ab le .

t h i s time w e do not have t h e c a p a b i l i t y of performing it a t e l eva ted temperatures.

The t e s t s were made only a t ambient s i n c e a t I

Maximum and minimum diameters were averaged t o g ive the d i s c diameter; two samples

were t e s t e d f o r each batch and su r face material. The r e s u l t s were a s follows:

'LRL GCTN-131

- 22 - Disc Test

Disc Diameters of LX-02-1 (cm)

Surface LRL Resul ts Pantex Resul ts Lot A-186l Lot A-187= Lot A-188'

Mylar Polyethylene P lex ig l a s Teflon S t e e l Saran

8.3 7.5 8.0 7.6 7.8 ---

9.0 6.8 7.8 7.0 8.3 7.0 8.8 7.2 7.6 7.2 8.6 6.8

----------- 'Milled on t h e rubber r o l l m i l l be fore t e s t i n g . 'Teeted as rece ived from the vendor.

8.4 7.8 8 . 3 .

7.9 7.9 8.6

On most su r faces , a nea r ly p e r f e c t c i r c u l a r shape was produced; t h e d i f f e rence

between t h e maximum and minimum diameter being, a t most, 0.2 cm. An i r r e g u l a r

shape was produced on Teflon; t h e maximum and minimum diameters varying a s much

as 2.0 c m f o r one l o t . This was caused by adherence of t he LX-02-1 t o t h e Teflon

which was a l s o experienced wi th t h e polyethylene, a l though not t o such an ex ten t

a s Teflon.

temperature.

None of t h e rest of t h e ma te r i a l s exh ib i t ed any adhesion a t ambient . .

Future work will inc lude adapt ing t h e test t o the e l eva ted temperature (5OoC.).

Disc tests i n t h e f u t u r e w i l l be l imi t ed t o those m a t e r i a l s t h a t may poss ib ly

be used a s t i l e materials, but will involve more samples t o obta in a b e t t e r f e e l i n g

I

f o r r e p r o d u c i b i l i t y . . .

Adiprene L-100 Aging Study

Three yea r s ago an experiment was s t a r t e d t o detect any def ic iency i n Adiprene

L-100's e f f e c t i v e n e s s as an adhesive f o r H.E. caused by aging. The tes t was

: c

r'

W'

- 23 - designed f o r f i v e y e a r ' s durat ion. The i n i t i a l phase of t he experiment included

t e s t i n g of t e n s i l e and shear specimens s to red a t +165'F. up t o six months. Each

month f i v e specimens of each type were t e s t e d on t h e Tinius-Olsen E l e c t o m t i c

Machine (feed ra te 0.015 inch/minute) a f t e r being cooled t o ambient temperature.

A l l remaining tests were t o be conducted annual ly on specimens s to red a t ambient

temperature. Unbonded specimens w e r e a l s o s to red and glued af terwards f o r

comparison. Three-year o ld ambient temperature-stored specimens were t e s t e d t h i s

q u a r t e r and t h e r e s u l t s reported below. The average s t r e n g t h s of a l l t h e previous

tests are a l s o reported.

Shear and Tens i le S t rength ( P s i )

Aging Study

PBX 9404 Glued t o PBX 9404 With Adiprene L-100, Curing Agent - 11 pph M.oCA

Test ing Speed - 0.015 inch/minute

Shear S t renpth

Aged 3 Years Aged 3 Years Glued 3 Years Glued 1 Week

I

Avg .

371 379 467 485 518 482

450 -

769 825 825

806*

Tens i l e S t rength Aged 3 Years Glued 3 Years

342 335 322 285 2 84 2 84

309 -

Aged 3 Years Glued 1 Week

3 14 310 300

*No explana t ion can be presented f o r t h i s high value a t t h i s t i m e .

308

LJ W

- 24 - Storage Period

Control 8 hours 1 month 2 months 3 months 4 months 5 iiionths 6 months 1 year 2 years 3 years

Storage Temperature

(OF)

Ambient 165 165 165 165 165 165 165

Ambient Ambient Amb Fen t

Average Shear Strength

( P s i )

378 418 3 83 327 362 366 500

393 372 450

---

Average Tens i le Strength

( p s i >

242

202 206 177 189 221 168 289 325 308

---

The test r e s u l t s i n d i c a t e that the g lue bond has not d e t e r i o r a t e d a f t e r t h ree years

of aging.

t h e H . E . , as a l l breakage occurred i n the H . E .

The only conclusion t h a t can be made i s t h a t t h e g lue i s s t ronger than

FUTURE WORK; COMMENTS; CONCLUSIONS

The new t o r s i o n a l shea r s t r e n g t h r e s u l t s of Aerobond H-7 are remarkably higher

than those prev ious ly reported. The ear l ier values were obtained nea r ly th ree

years ago, probably from a n o ld batch of Aerobond i n which the she l f l i f e had

expired. V i scos i ty adjustment s t u d i e s of Aerobond ind ica t ed t h a t 10 pph a l l y l

g lyc idy l e t h e r and poss ib ly even 5 pph would be e f f e c t i v e ; a l s o , t hese smaller

amounts woyld no t reduce s t r e n g t h s o d r a s t i c a l l y . Two new d i l u e n t s , bu ty l g lyc idyl

e t h e r and benzene w i l l be t e s t e d both f o r compat ib i l i ty and v i s c o s i t y adjustment

on Aerobond. A h e a t aging s tudy has been s t a r t e d i n which t e n s i l e specimens

(aluminum-to-aluminum and aluminum-to-LX-04-1) are heated t o 165'F. and aged

f o r one, two and t h r e e months; con t ro l samples are a l s o t o be t e s t ed .

*

The prel iminary r e s u l t s of t he d i s c e x t r u d a b i l i t y t es t compare - in d i r e c t i o n t o those

obtained a t LRL. Perhaps, i n connection wi th t h i s t es t , t h e e f f e c t of var ious

Li I

- 25 - environmental condi t ions upon t h e behavior of Lx-02-1 should a l s o be s tud ied .

It has been noted t h a t a f t e r s eve ra l weeks of s to rage a f t e r mi l l i ng , LX-02-1

becomes less p l i a b l e and i t s e x t r u d a b i l i t y i s g r e a t l y a f f ec t ed .

r e s t o r e s i t s p l i a b i l i t y .

f o r q u a l i t y c o n t r o l , bu t may be t h e beginning t o eva lua te t h e p rope r t i e s .

Remilling then

Evaluation of these c h a r a c t e r i s t i c s may not prove usefu l

It is hoped t h a t w i t h t he i n s t a l l a t i o n of the Di l lon tester, a new f i e l d of

adhesives t e s t i n g may be r ea l i zed ; that of t h i n films.

designed t o measure t h e p e e l o r s t r i p p i n g s t r e n g t h of adhesives under a spec i f i ed

set of condi t ions .

and t h e i r adhering characteristics on H.E.

The peel test was

It may be poss ib le t o expand t h i s test to 'protect ive films

The pee l test w i l l a l s o be appl ied t o t h e determinat ion of t h e se t per iod of

S i l a s t i c 140 on which t h e t o r s i o n a l shear t e s t cannot be used s i n c e curing of

140 depends upon t h e propagation of atmospheric moisture through the s i l i c o n e

w a i s t band. S i l a s t i c 140 and s i l i c o n e rubber w a i s t band material a r e a v a i l a b l e ,

and pre l iminary tests w i l l be made as soon a s poss ib l e . . .. :.

I