INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
986
(20) Kern, W., Ber., 68, 1439 (1935). (21) Kraemer, E. O., IND.ENQ.CHEM., 30, 1200 (1938). (22) Kraemer, E. O., and Lansing, W. D . , J Am. C k e n . Soc., 57. 1389 (1935). (23) Mark, H . , in “Der feste Korper” p . 103, S. Hirzel, Leipzig, 1938. (24) Mark, H., “Physical Chemistry of High Polymeric Systems”, p. 235 ff., New York, Interscience Publishers, 1940. (25) Mead, D. J., and Fuoss, R . M . , J . Am. Chem. SOC.,64, 277 (1942).
(26) Ostwald, W-, Kolloid-Z., 49, 60 (1929). (27) Schulz, G. V., 2.physik. Chem., B30, 379 (1935).
Vol. 35, No. 9
(28) Schulz, G . V., and Blaschke, F , J. prakt, C h e w , 158, 130 (1941). (29) Schulz, V., and Dinglinger, A , , Zbid., 158, 136 (1941). (30) Staudinger, H . , “Die hochmolekularen organischen Verbindungen”, Berlin, J. Springer, 1932. ( 3 t ) Staudinger, H., and Fisrher, K.’, J . prakt. Chem., 157, 19 (1940). (32) Zbid., 157, 158 (1941). (33) Staudinger, H . , and Schneiders, J., Ann.,541, 151 (1939).
c.
I
PRESENCEU before the Division of Rubber Chemistry at the 102th Meeting of the AVERICANC ~ E W X CSocrnry, AL Detroit, Mich Communication 920 from Kodak Research Laboratories.
Neoprene GN, Hycar OR-15, and Perbunan 26 S. M.MARTIN, JR., AND A. E. LAURENCE Thiokol Corporation, T r e n t o n , N. J. The properties of Thiokol FA blends w i t h which will not adversely affect HE use of blends of the N~~~~~~~ GN,H ~0 ~ ~~ 1 and 5 ~, perbunan , ~ the rate of cure of Thiokol FA. various synthetic rubbers Thus, in the Hycar OR-15 in the Of 26 have been studied. Thiokol FA is comand perbunan 26 compounds, stocks is increasing. The purPatible with these synthetics in Proporb e n z o t h i a z y l disulfide and pose is to get better processing stocks, to obtain specific proptions, but properties of the blends do not DPG ( d i p h e n y l g u a n i d i n e ) erties in the cured composition, show a change zuhich i s proportional to the were used for acceleration. amount of each synthetic i n the stock f o r Formulas of the base stocks and to extend the supply of and a summary of their physxny one that might be momenall properties measured. Consequently, ical characteristics are shown trtrily short. Thiokol FA1 is being successfully used in since a number Of the Properties Of the in Table I. The stocks were combination with other synblende do not vary as a linear function of mill-blended so that the crude the composition, i t was necessary to estabsynthetic content of each blend thetic rubbers. I n some of lish trends f o r blends of each of the several w&s that shown in Table 11. the stocks Thiokol FA is the I n the discussion all mention predominant phase; synthetics. Data of a basic nature are of blends refers to the crude some other synthetic is the principal constituent of the Presented which should Prove useful even synthetic content and not to rubber phase and Thiokol FA though any speci& property can be modiparts of compounded stock. .lied to s o m e entent by cornpounding variaThe ~ t o c k blended s easily in all is used to impart specific properties to the compound. tions. proportions. I n all cases the Thiokol FA stock was first millThe purpose of this study warmed by six passes through was to obtain basic information on the properties of Thiokol FA blends with Neoprene GN, Hycar OR-15, and Perbunan 26. It is felt that the data will show general characteristics which prevail in blends even ,though any specific property can be varied within certain TABLE I. J?oR?lrUr..\s OF BASS STOCKS limits by formulation changes. 100 .. .. Ttiiokol F.1 Neoprene O N .. i6o .. A typical FA stock of 70 durometer hardness was selected .. 100 Hycar OR-15 for one part of each series of blends. The other portion was Perbunan 26 .. 100 10 5 8 9 Zinc oxide made up of typical compounds of Neoprene GN, Hycar ORSemireinforcing black 60 50 50 60 0.5 1 1 1 Stearic acid 15, and Perbunan 26. These latter stocks had the same 0.3 .. 1 1 Benzothiatyl disulfide hardness as the Thiokol FA conipound but contained no exDiphenylguanidine 0.1 .. 0.2 Phenyl-a-naph thylamine . . 2 . . tractable plasticizers; the latter were purposely omitted to Extra light calcined magnesia .. 4 .. .. .. 1 . 5 1 .6 simplify the interpretation of the data. Sulfur When stocks are being compounded for blending with Physical Properties of Sheets Cured 60 Min. at 298’ F. Thiokol FA, it is important that accelerators be selected Tensile lb./sq. in. 1290 2820 3000 2760
T
I
.
I
.
.
I
.
1 The trade name “Thiokol” used throughout thin article is registered in the U. 8. Patent O5ce.
Elongaiion, %
410
430
450
I
310
September, 1943
INDUSTRIAL AND ENGINEERING CHEMiSTRY
dered from these blends 318 sunininrized in T a b l e 111. T h e Neoprene GN stock8 :and all ita blends with Thiokol FA weie smooth. T h e Hycni. O R nnd Perbunan stocks were tough ;mI gave wavy or rough slicets 011 calendering. Kith &:%T the roughncss disappeared in the 40 ThiokolMl Hycar blend. With Perbunan 3 smaller amount of Thiokol gave 3 smootli sheet. In
w
20 13 5
The diffusion was measured by puttiiig i 4 ml. of fuel in a half-pint Muson jar
equipped s i t h B Kem top. A disk cut from sheets 0.062 inch thick (cured 40 nrinutes a t 298' F.) was insertod into the top, replacing the regular metal rlisk of the Kern top. The jars were stoved in an inverted position in a eonstbnttemperature rooin (80° F.) with free circulation of air across the surface of the disk and were weighed on a balance sensitive to 0.02 gram. Diffusion through the straight Thiokol FA stock is fairly low and increases slightly on addition of small amounb of another synthetic. Blends containing more than u)per cent Neoprene GN and Perbunan show rapid increase in diffusion u.8 the proportion of either of these synthetics in the blends is raised. With Hycar OR the same general characteristics prevail, but diffusion losses are lower than for Seoprene GN and Perbunan blends.
e4
60
the other e.ttrrn,r.
4a
20
10
0
988
Vol. 35, No. 9
INDUSTRIAL AND ENGINEERING CHEMISTRY TENSILE STRENGTH
Figure 3 also shows tensile strength curves for the 60minute press cure at 298" F. for the various stocks. The tensile strength wa3 determined according to A. S. T. M. proce-
2
I
8
6
4
give better processing stocks than straight Thiokol. Here again it is sometimes better to sacrifice slightly in solvent resistance to gain better vorking characteristics even though the tensile strength of the blend is not materially increased
4
8
Figure 1. Diffusion of 813 Fuel through Thiokol FA Blends with Thiokol FA, Hycar OR, and Perbunan
dure (2) for testing vulcanized rubber. The volume swell of the stocks increases more rapidly with addition of other synthetics to Thiokol FA than does tensile strength. At the same time the tensile strength of the other synthetics decreases to a greater extent with the addition of Thiokol FA than does volume swell. However, it may sometimes be advantageous to sacrifice tensile strength to gain better working characteristics even though the volume swell is only slightly improved through blending. On the other hand, 10 to 20 per cent of the other synthetic rubbers blended with Thiokol FA
TABLE IV. TEARRESISTANCE DATA Cure at 298" F., Min.
90
80
Parts Thiokol FA 60 40 20
10
0
10
Parts Other Synthetic 20 40 60 80
90
100
FA-Neoprene GN Blends 221 350 244 211 316 253 264 210 181 277 199 205
368 353 300
370 323 296
314
340
330
Thiokol FA-Hycar OR-15 Blends 258 351 308 269 246 253 295 301 305 328 311 309 262 285 295 335 340 270
360
247 186 181
100 0
20 40
60
Av. 20
40 60
301 286 290 292
Thiokol 299 305 269
_ _ _ _ - - - 291
_
Av. 20 40 60 Av.
303 280 277 278
278
311
238
207
_
299
277
Thiokol FA-Perbunan 243 224 203 298 262 254 240 243 228
260
218
243
228
281
284 227
_
-
303
290
205
26 Blends 222 208 238 181 189 171
195 165 155
193 173
-
-
-
167 -
216
187
172
174
over that of the original Thiokol compound. It should be pointed out that Neoprene GN-Thiokol FA blends do not cure satisfactorily in open steam. Both the Thiokol FA and the Neoprene GN stocks alone cure well under the same conditions. TEAR RESISTANCE
Tear was determined on five strips at each cure and all values falling with 20 per cent of the highest value were averaged (3). Data were obtained on three separate stock mixes, and tear values for the three mixes checked one another within 20 per cent. Table I V summarizes tear resistance of all stocks; and for the purpose of establishing trends, tear values for the three cures were averaged. Blends of Thjokol FA-Neoprene GN show a decided dip in tear in the middle of the range. Small additions of Neoprene GN to Thiokol FA or of Thiokol FA to Neoprene GN do not affect the tear of either control stock. The reason for the low tear values in the middle of the range is not immediately apparent. It is possible that some constituent present in the crudes may exert this undesirable effect. Since the dip appears in repeated tests, it. signifies an actual trend. The tear resistance of Hycar OR shows great improvement with small additions of Thiokol FA, and the average tear across the whole range of the Thiokol FA-Hycar OR blends is comparatively high. This improvement in tear resistance of the Hycar OR stock by the addition of Thiokol FA has been demonstrated on a number of mixes. Such blends offer possibilities for obtaining better tear-resisting Hycar compounds. Blends of Thiokol FA and Perbunan show practically a linear increase as the amount of Thiokol FA increases beyond 10 parts.
-
-
-
I
September, 1943
INDUSTRIAL AND ENGINEERING CHEMISTRY
989
Figure 3. Swell (in 813 Fuel) and Tensile Strength of Thiokol FA Blends with Neoprene GN, Hycar OR, and Perbunan (Cured 60 Minutes at 298' F.)
COMPRESSION SET
Tables V and VI summarize data on the resilience and compression set of the various stocks. Under momentary distortion as measured by rebound, Thiokol FA shows a relatively high degree of recovery. However, under sustained compression it tends toward high set. Compression set measurements were run by A. S. T. M. method B (1) under constant deflection using plugs ll/sinches in diameter and '/s inch thick. A compression of 25 per cent w a ~uaed and the test assembly was aged 22 hours at 158' F.
990 TABLB
'Thioh,J Syn- Cure at PiasF.4. thetic, 298' F., ticity I'nrts Parts Min. Index
100
Vol. 35, No. 9
INDUSTRIAL AND ENGINEERING CHEMISTRY
0
20 40
0 118
VI.
PROPERTIES' O F
THIOKOL FA BLEKDSWITH HYCAR OR15
Raw Modulus Stock at 300% T e n d c , Shore Corn- Lupke X;!onga- Hard- preasion ReAviaElonga- Elonga- Lb./ tion, 'i/a tion Sq. In. tion, ness Set bound tion gas 490
60
66.5 1005 1130
1050 1315 1340
. 4 S D WITH PERBUNAN
Volume Swell 813fuel
Acetone
T'hiokol FA-Hy car OR-15 Blends 660 66 1.0 100 47.5 1.0 490 70 100 46.5 420 72 100 44.0 1.5
11.0 10.0 8.3
20.8
Ethyl acetate
20.0 20,8
70 Hr. at 212' F. in Circa Light Process Oil HardCClb Swell nebs
23.0 20.0 18.5
38.0 36.0 33.0
-6.0 -6.9 -6.0
z2
38 0 33.0 36.0
-7.5 -2.0 -1.5
70 72 76
74 / I
90
10
20 40 60
0 122
4.50
565 930 1090
960 1265 1380
660 530 460
69 71 72
100 100 io0
36.5 36.5 35.5
1.0 1.5 1.5
12 3 11.0 11.0
Ci0.2 48.2
42 0 32.0 30 5
80
20
20 40 60
0 126
1100
,535 865 1030
875 1255 1420
780 640 530
68 70 71
100 100 100
31.5 31.5 32.0
1.0 1.0 1 6
12.5 12.6 12.5
122.2 107.2 83.7
57,o 44.5 -10 o
38.5 35.0 33.0
-4.0 -0.3 -0.3
70 73 74
GO
40
20 40 60
0 136
1200c
460 775 935
945 1400 1560
970 710 650
66 69 71
100 Y7.5 96.5
26 0 26.5 27.0
1.0 1.0 1.0
18.0 18.0 10.5
329,o 197. 0
76.0 66.0
96.0
39.0 36.5 36.0
-2.0 -2.0 -0.3
70 70 70
40
GO
20 40 60
0 148
lZOO+
500 775 945
1235 1860 1985
980 780 680
ti9
66
95.2 86.2 84.5
22.5 23.5 25 0
2.0 1.5 1.5
23.0 21.5 21.5
339.0 281.5 220.8
111.5 132.0 01 0
39.0 40.0 38.0
2.0 3.5 4 0
68 69 70
20 40 60
0.167
675 1045 1270
2120 2550 2630
69
79 6 67.6 60.1
20.0 20.5 21.0
1.5 2.0 1.5
26.0 27.0 25.0
413.3 300.1 259.9
145.5 127.0 105 0
44.0 42.0 42.0
5.0 5.5 5.5
67
b8
, 630
20 40
0.162
1200f
1010 1440 1885
2760 2770 2620
740 560 430
66 69 70
58.2 54.9 42.9
18.0 19.0 18.5
1.5 1.5 1.5
29.5 27 5 24.0
369.9 259.9 220.Y
146 123.5 107.0
40.5 39.0 38.0
5.5 6.5 8.5
66 69 70
20 40 60
0.158
1200f
1400 1930 1250
3060 2940 3050
620 470 440
67 69 70
31.6 23.1 17.7
16.5 15.5 14.6
1.5 2.0 1.5
30.5 29.5 30.5
254.7 18Y . 3 167.2
142 116 107.0
42.0 39.0 38.0
8.0 8.5 7.0
79
20 40 60
0.117
345
485 936 1140
835 1160 1265
Thiokol FA-Perbunan Blends 67 100 47.5 70 100 47.5 370 72 100 46.0
1.5 1.5 1.5
10.0 11.0 10.0
21 21 20
23.0 20.0 18.0
38.0 37.0 33.0
-5.5 -6.0 -7.0
20
0 122
325
485 Y 50 1190
800 1265 1405
680 4Y2 420
65 71 72
100 100 100
43.0 42.5 40.0
2.0 1.5 1.5
17.0
50 46 34
46.0 35.0 30.5
48.5 44.0 41.0
-4.0
14 5
-0.3 0
70 75
100 100 100
41 41 40+
2.5 2.5 2.5
20.5 21.5 17.0
76
59 50
64.5 47.5 41.5
60.0 48.5 47.5
-2.5 -3.0 +0.3
6G 70 74
64 ti5
20
10
80 90
1200f
60 0
100
100
0
90
10
40 ti0
0.5
660 500
li.O
240.9
67 70
68 69
73 74 76 il
20
0 144
390
510 895 1145
810 1200 1400
G60 480 410
66 70 72
20 40 60
0 174
410
385 890 1135
885 1175 1420
580 440 410
67 70 71
92.8 93.1 91.4
40 40 40.5
5.5 4.0 5.0
35.0 80.5 29.0
115 106
Y!,
106.5 81.0 70.5
77.0 68.0 66.5
5.0 5.5 5.0
20
0 189
YO0
1270 1465
1336 1770 1905
480 450 420
66 B9 70
84.5 72.8 72.6
40 41 41
7.5 6.0 6.5
40.0 35.0 32.0
134 122 112
114.5 102.0 90.5
84.0 17.5 (2.5
8.0 7.5 8.5
05
1450 1950
2145 2460 2405
400 4OO
68
1100
A50
09 70
62.8 48.6 41.7
41 42 41.4
10.0 10.0 10.0
44.5 41.5 41,s
i. 42 118 109
121.0 102.0 91.5
89.0 75.0 74.0
13.5 13.5 13.5
65 66 67
345
1980 2420 2480
2600 2620 2600
410 330 320
69 70 71
49.4 37.3 32.6
41.5 42.0 41.5
11.0 10.0 10.0
46.5 44.0 44.0
112 109 107
119.5 99.0 98.0
81.0 77.5 74.5
11.0 12. c5 13.6
07
260 20 0 236 40 60 See Table V for explanatory notes.
2280 2760 2740
2500 2800 2820
330 310 310
69
24.7 14.0 12.1
39.0 40.0 41.6
11.0 12.0 10.5
51.5 48.5 46.5
118 112
118.0 121.5 103.0
89.0 83.0 83.0,
18.5 18.:
ti9 ti!,
20.3
7U
80
20
(io
40
4il
60
40 60
40
375
00
10
IO
0
'1
880 700
70
i5.0
80
90
100
20 40 60
0 213
20 40 60
0 220
106
70
71
(50" C.). Resilience or percentage 1,eboundwas measured 011 the Lupke resiliometer ( 4 ) . The compression set of Thiokol FA is improved by blendiiig with the other synthetic rubbers. The amount required t o effect a noticeable change varies with the different synthetics. In a great many applications this high permanent set does not detract from serviceability. JVhere greater resistance to set is required, it can be obtained by the use of blends n.ithout sacrificing too much in solvent resistance. Thiokol FA is not generally recoinmended where resistance t o caoinpre$sioii set is a primary consideration in use.
11'
65
63 ti4
cib ti9
A summary of the low teinperature characteristics of thebe blends is shown in Table VII. The flexibility was-determined by mounting strips 4 X X l/la inch on sticks 3/4 x d / 4 inch in cross section, aging in dry air a t the temperatures shown, and pinching the samples with a gloved hand. This method gives a good qualitative index of the rate of stiffening of each sto&. OTHER PROPERTIES
FREEZE RESISTANCE
Tables V and VI include supplementary data on various properties for a series of cures. These data are included to give as complete a picture as possible of the properties of the blends.
In stocks containing no plasticizers, Thiokol F A shows better low temperature flexibility than Neoprene GK, Hycar OR-15, or Perbunan 26. The low temperature flexibility of Hycar OR-15 and Perbunan 26 is improved by blending n-it,h Thiokol FA.
PROCESSING. The addition of Thiokol FA to Hycar and Perbunan improves processing. Smce Xeoprene GN requires no additive to get smooth running stocks, no marked improvement was noticed in processing through the use of
SUMMARY
September, 1943
INDUSTRIAL AND ENGINEERING CHEMISTRY
l h d s . Tbe addition uf Seoi>reiir, Ilyesr, or l'erbunnn to Thiokol gives 3 tougher uncured stork wliich is an sdv:i.nt:igv for many processing operiltions.
gasoline I)IFFCRION. The diffusion of ari~~~~atin-blendeil tlirnogli blends of Thiokol FA :and other synthetics, esi,ressod in gmms per square inch per day, does not increase I i n e d y i r i t h the percentage composition of the blends. h a l l :uimints of the ot.her synthetics added to Tliiokol do not iiirreiw the diusion as much as if the increAse were linear.
Likewise, the addition of smaller anrounts of Thiokol to the otlw synthetics does not lover the diihsion 8 s muclr i ~ fwould i he expected from a linear relation. SWX,L IN SOLVENTS. For blen& of Thiokol FA and Xeoiiiene GN, the linear relation holds for percentage swell i i r 818 fuel, acetone, ethyl acetate, :and mrhon tetrachloride at T i m 1 1 temperature and Circo light process oil at 212" F. The volume swell of Thiokol-Hymr 11lmdsin 818 fuel and cirboo tetrachloride, nt room temperst.iire and in Circa light oil :it 212" F., increases linearly as the percentage of Hycar is increased. In acetone and ethyl acetate the percentage swell incresses linearly with increase in Hycar content until tlie 80 Hycar-20 Thiokol proportion is reached, where tiic s ~ e lholds l constant or perhaps deci.e;t*ea. This is probnbly tliw to the state of cure of the Hycm The vohime swell of Thiokol-P liaewly with increased percentages of Perbunan in 813 fuel at rooni temperature snd Circa tight oil itt ZIZa F. The rolume swell of these blends in aeetorre, ethyl acetate, ami carbon t.etiachloride does not follow a linear relation. The i'ereentzge swell of the hle~iilsis greater than would be experteil if the relation were linear. It should be pointed out that in tile ca8e of Neoprene Gii Tliiokol FA blends, whert: the s>~ell reletion is practically linrsr in all solvents, the difference in volume swell for different cures on any one blend is relatively smI1. In the case of the Elycar OR and Perbuiiau blends with Thiokol FA where tlir reistion is not linear, there i s n relatively large difference i i i tho volume swell between different.cures of the same blend. This leads to the belief that, in blends which swell more then would be expected, that one phme hw not reached a good state of cum. TENSILESTRENOTE. The tensile strength of the blends du uot change linearly with the coinposition. In all eases the tensile st.rength was lower than ~vouldlie expeeted from thc trnsile strength of the stocks blendwl. FREEZE REBISTANCE. The freeze rcsiatance of the blends l)ears practically a linear relation tu the Composition and the freeze resistance of the synthetic blended. TEARRESISTANCE.In Neopreni: GN-Thiokol FA blends the tear resistance decrease8 with the addition of Thiokol to eoprene and with the addition of Neoprene to Thiokol. he curve goes through minimurn in blends that are apivoximntely 50 per cent. Neoprene :wI 50 per cent Thiokol
991
