1384
INDUSTRIAL AND ENGINEERING CHEMISTRY
is shown by the data plotted in Figure 3. The addition of rosin makes no difference on the water resistance of neoprene a t room temperature, but it appreciably improves the resistance a t elevated temperatures. The litharge stock containing rosin actually appears to be more resistant a t 100” C. than a t some intermediate temperatures. Amounts of rosin greater than 5 parts per 100 parts of neoprene do not improve the water resistance; 10 parts are no more effective than 5 parts, but 20 parts of rosin decrease the water resistance.
VOL. 29, NO. 12
’
J
TABLEV.
EFFECTOF SOFTENINGAGENTSON LITHARGE-CARBON BLACKSTOCKS
Formula No. Neoprene Type E FF wood rosin Litharge Carbon black (Thermax) Cottonseed oil Mineral oil Barrett No. 10 oil
21 100 5
20
150
. . ... ,
22
23
100 5
IO! 0
20
20
150
150
...
5 5
...
...
..
10
Stability, Plasticity-Recovery Numbers Aged a t 50° C., Hr. 0 24 48 96
Effect of Sulfur
200-14 250-46 285-61 352-116
130-14 162-7 189-27 238-69
130-5 173-8 202-30 270-89
Stress-Strain Data”
M. A. Youker of the du Pont Company observed that the water absorption of a magnesiazinc oxide gum stock was increased from 16.1 to 26.7 per cent by increasing the sulfur content from 1 to 3 parts per 100 parts of neoprene. The influence of sulfur was less marked in the case of carbon black stocks. N. L. Catton of the du Pont Company investigated in more detail the influence of sulfur and observed not only this effect on the water resistance of magnesia-
Cure at
153’ C.,
,
Min. 10 20 40 60
56( 800) 83 1175) 9011275) 90(1275)
Days qf Immersion 4 16 32 32
121(1725) 121(1725) 139 1975) 13411900)
330 180 230 210
28 400) 97(1375) 260 421600) 121(1725) 290 40(575 121(1725) 290 42(600] 125(1775) 250
37(525) 54 776) 541776) 53(750)
114 121 121 121(1725) 240
Stress-Strain Data after Immersion in Water a t loOD C.
102(1430) 144(2050) 190 65( ’325) 127(1800) 200 86(1225) 132(1875) 200 118(1675) 135(1925) 130 93 1 3 2 ~ ) ? 128(1823) 180 104(1425) 127(la00) 160 lIl(1578) 140(2075) 160 071 95;) 130(1850) 180 93(1325) 127(1SOO) 160
% Loss of Material after Immersion in Water at looo C. 0.67
--
4.84
3.34
Apparent % Volume Water Absorption (Weight Method) av
NEOPRENE
foe
48
noun
PERIOD.
Days 2 4
100 NEOPRLNL T Y P E E , 10 HgO, 5 In0
S
I ROSIN 5 ROSIN
0
16 32 51 71 81
0
30°C. 0.14 0.23 0.29 0.33
100°C.
0:is
0.34 0.60 0.75 0.97 1.17 0.98 0.72
3OOC. 0.39 0.62 0.64 0.76
1 :26
1
100DC. 1.87 2.47 2.77 2.75 2.00 1.18 0.67
3OOC. 0.00
0.02 0.04 -0.09
....
-0.35
....
100°C. -3.76 -3.40 -3.25 -3.11 -2.32 -2.20 -2.53
....
0:iz .. 1:4 .. -0.72 The figures for each formula represent stress a t 100% elongation in kg. per sq. cm. (lb. er sq. in.), tensile strength in kR. per sq. om. (Ib. per sq. in.), and per cent elonpatlon at %reak.
0
shown in Figure 3. These results indicate that the hydration of magnesia occurs a t room temperature as well as a t elevated temperatures. They show clearly the superiority of the litharge stocks.
Literature Cited
1I-
I
10
so
40 80 so T E M P E R A T U R E ‘C.
70
no
so
(1) Bridgwater a n d Krisman, IND. ENG.CHEM.,25, 280 (1933). 100
(2) Clapson, Ibid., 29, 789 (1937). (3) E.I. du P o n t de Nemours and Co., Inc., D u Prene Manual, Aug.,
1934.
zinc oxide stocks but an even greater effect with lithargemagnesia stocks. I n a stock containing 20 parts litharge, 2 magnesia, and 5 rosin, as the sulfur was varied from 0, 1,3, 5 to 10 per cent the water absorption in 48 hours a t 100” C. increased from 7.53 to 11.09, 43.0, 76.2, and 96.5 per cent, respectively. Here again the effect was less marked in a carbon black stock than in a gum stock. This decrease in the water resistance in the presence of sulfur may be attributed to the formation of water-soluble products by reactions of the sulfur with neoprene. A greater activating influence of litharge as compared with magnesia and zinc oxide on these reactions would account for the greater impairment by sulfur of the water resistance of a litharge compound than of a magnesia-zinc oxide compound.
Variations with Temperature The water absorption for both magnesia-zinc oxide and litharge gum stocks a t temperatures from 30’ to 100’ C. is
(4) India Rubber World, “Compounding Ingredients for Rubber,”
1936. (6) Starkweather a n d Walker, IND. ENG.CHEM.,29, 872 (1937). REOEIVXID September 23, 1937. Presented before the Division of Rubber Chemistry a t the 94th Meeting of the American Chemical Society, Rochester, N. Y., September 6 to 10, 1937. Contribution 36 from Jackson Laboratory, E. I. du Pont de Nemours and Company, Inc.
Correction On page 968 of the September, 1937, issue of INDUSTRIAL AND ENGINEERINQ CHEMISTRY an error occurs in the very important definition of “Molecular Distillation.” The sentence which begins on the iifth line of the section on “Apparatus and Methods” should read: “The free path of the majority of the moleculen emerging is then greater than the distance between the surfaces, and distillation occurs at the lowest possible temperatures.” The word “less” was printed instead of “greater.” K. C. D. HICKMAN
