1868
BUKHAROV et al.
Table 1. Composition of rubber stocks based on SKN-18
and SKN-26 rubbers
inhibit thermal oxidative degradation more effectively
than I and are comparable in this respect with Diafen
FP (Table 2).
Content, wt parts per
100 wt parts of rubber
Component*
EXPERIMENTAL
SKN-18
SKN-26
In our study, we used commercial samples of buta-
diene acrylonitrile rubbers SKN-18 and SKN-26.
Rubber stocks were prepared in two steps with a Bra-
bender plasticorder with the mixing chamber volume
Zinc oxide
4
1
2
1
1
3
0.7
Sulfenamide Ts
N,N-Dithiodimorpholine
Thiuram D
3
of 50 cm . In the first step, the rubber, carbon black,
Stearic acid
1
40
and other components, except the vulcanizing group,
were mixed at 130 C. In the second step, the vulcaniz-
ing group was added. The total mixing time was
7 min, and the rotor rotation rate, 35 rpm. The rubber
stocks based on SKN-18 and SKN-26 were vulcanized
at 143 C for 30 and 40 min, respectively.
Carbon black
EDOS plasticizer
Sulfur
120
45
1.5
2
Stabilizer
4
* Sulfenamide Ts is N-cyclohexyl-2-benzothiazolylsulfenamide;
Thiuram D, tetramethylthiuram disulfide; EDOS plasticizer,
a mixture based on dioxane alcohols; stabilizer, compounds
I III, V, III + V, Diafen FP, or Acetonanil.
Physicomechanical tests were performed with a
Tensometer T-10 tensile-testing machine (Monsanto).
1
The H NMR spectra were recorded on a Varian
Gemini-200 spectrometer (200 MHz) relative to resid-
ual protons of deuterated solvents.
calixarenes I III, benzylated resorcinol V, and a
mixture of III and V obtained in the course of the
reaction of I with IV are listed in Table 1. The results
of physicomechanical tests of these stocks are listed
in Table 2. The performance of the stabilizers was
evaluated by relative changes in the nominal tensile
strength , relative elongation at break , and elonga-
tion set , occurring upon thermal oxidative aging.
4,6,10,12,16,18,22,24-Octahydroxy-5,11,17,19-
tetra(3,5-di-tert-butyl-4-hydroxybenzyl)-2,8,14,20-
3,7 9,13 15,19
tetramethylpentacyclo[19.3.1.1 .1 .1
]octa-
cosa-1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23-
dodecaene III. Formic acid (65 ml) was added to a
solution of 3 g (5.5 mmol) of I and 6.9 g (24.8 mmol)
of IV in 55 ml of acetone. The mixture was allowed
to stand at 20 C for 1 day. Then it was poured into
Table 2 shows that, in the rubber stock of thiuram
vulcanization with a high filler content, modified
calixarenes II and III somewhat surpass II and Diafen
100 ml of water, and an NaHCO solution was added
3
FP (amine stabilizers) as regards preservation of
,
to pH 5 6. A mixture of products (7.75 g) was ob-
1
but are inferior to the latter additives with respect to
preservation of . In the rubber stock of sulfur vul-
canization with a low filler content, exhibiting better
physicomechanical properties, calixarenes II and III
tained, containing, according to the H NMR spec-
trum, compounds V and III in a molar ratio of 3 : 7.
It was dissolved in 25 ml of benzene, and 170 ml of
hexane was added. Compound III was obtained; yield
Table 2. Effect of stabilizers on properties of vulcanized rubbers based on SKN-18 and SKN-26
Stabilizer
Parameter
control*
I
II
III
V
III + V
, MPa
, %
, %
14.0 (21.2)** 13.7 (23.5)
13.3 (18.0)
117 (244)
4 (8)
12.7 (20.1)
133 (308)
4 (8)
13.2 (20.5)
156 (310)
4 (10)
14.7 (21.6)
129 (280)
3 (8)
129 (314)
4 (8)
148 (320)
3 (9)
/ ***
/ ***
0.89 (0.87)
0.95 (0.69)
0.89 (0.78)
0.98 (0.60)
0.94 (1.06)
0.75 (0.82)
0.91 (0.95)
0.80 (0.62)
0.81 (0.95)
0.81 (0.77)
0.89 (0.88)
0.62 (0.69)
* For vulcanized rubber based on SKN-18, Diafen FP : Acetonanil (1 : 3); for that based on SKN-26, Diafen FP.
** The values for SKN-26 are given in parentheses.
*** ( , ) Values obtained after thermal oxidative aging at 100 C for 72 h.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 11 2003
Bukharov
