CHEMICAL OF

RESISTANCE

AGGRESSIVE V. V.

Shubin

OF

RUBBERS

IN T H E

VAPORS

MEDIA and

E.

G. K o g a n

UDC 66.018.8:678.7

During the s e r v i c e of r u b b e r - l i n e d c h e m i c a l equipment not only aqueous a g g r e s s i v e media but also their v a p o r s act on the p r o t e c t i v e coating. However, t h e r e is no data in the l i t e r a t u r e on the r e s i s t a n c e of m a t e r i a l s f o r r u b b e r lining in the v a p o r s of a g g r e s s i v e media. In the All-Union S c i e n t i f i c - R e s e a r c h , Design, and Technological Institute f o r Chemical Machinery we have done work on determining the c h e m i c a l r e s i s t a n c e of r u b b e r s in the vapors of 30% aqueous sulfuric acid and sodium hydroxide and for c o m p a r i s o n in the solutions t h e m s e l v e s . The tests were made of Nairit B base c h l o r o p r e n e r u b b e r s without a filler (thermovulcanizate) and with a filler, TM-15 carbon black (40 p a r t s by weight), and vulcanizing agents, m a g n e s i u m and zinc oxides (IRP-1257 rubber). The r u b b e r without filler was vulcanized in a p r e s s at 153~ f o r 30 rain and the r u b b e r with filler in a s t e a m kettle at 143~ for 90 min. Five s a m p l e s of r u b b e r s with filler and without f i l l e r were placed in each of the solutions and an equal n u m b e r of s a m p l e s were placed in the v a p o r above the s u r f a c e of these solutions. The t e s t s were made at 70~ The swelling was d e t e r m i n e d by the weight method (All-Union State Standard 4 2 1 - 70). The test r e s u l t s a r e given in Fig. l a , b. As may be seen, under the action of aqueous sodium hydroxide and sulfuric acid and t h e i r vapors bulging of c h l o r o p r e n e r u b b e r s o c c u r s . In aqueous sodium hydroxide the weight of r u b b e r samples both with and without filler f i r s t drops insignificantly and then after establishment o f s o r p t i o n e q u i l i b r i u m o f t h e r u h b e r - m e d i u m s y s t e m r e m a i n s p r a c t i c a l l y c o n s t a n t f o r 7 2 0 h. By the end of the t e s t s the weight of the r u b b e r s a m p l e s without filler has gradually i n c r e a s e d by 12% and the weight of the r u b b e r s a m p l e s with filler by 4%. 28 20

f l

~- 4

~

I/

.

9 3z

a

-"

0

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L_ .~ -~

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240 480 72g 960 1200 1~40 IGSO t920 2150 2400 2648 288g 3fro

Test time b Fig. 1. Kinetics of bulging of ehloroprene r u b b e r s at 70~ a) in 30% aqueous sodium hydroxide (solid curves) and the v a p o r s above its s u r f a c e (broken curves); b) in 30% aqueous sulfuric acid (solid curves) and in the vapors above its s u r f a c e (broken curves); 1) r u b b e r without filler; 2) r u b b e r with filler.

T r a n s l a t e d f r o m Khimicheskoe i Neftyanoe Mashinostroenie, No. 10, p. 28, October, 1976. This material is protected by copyright registered in the name o f Plenum Publishing Corporation, 227 West 1 7th Street, New York, N.Y. 10011. No part o f this publication may be reproduced, stored in a retrieval system, o r transmitted, in a n y f o r m or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission o f the publisher. A copy o f this article is available from the publisher for $ 7.50.

I 900

In the vapors of the aqueous sodium hydroxide the samples of rubber without filler immediately bulge significantly and the character of the bulging approximates that of osmotic moisture absorption. By the end of the tests their weight had increased by 28% and the weight of the samples of rubber with filler by 8%~ Such a difference may be explained by the fact that lamp black and mag~.esium and zinc oxides promote the formation of thicker three-dimensional lattices and consequently an increases in the chemical resistance of the rubber. In aqueous sulfuric acid the rubber samples bulge significantly less than in its vapors, in the vapors the weight of the rubber samples without filler increases less than the weight of the rubber samples with filler. During an equal period of time of 1200 h the rubber both with and without filler bulges significantly more in sulfuric acid vapor than in sodium hydroxide vapor. In aqueous sulfuric acid the rubber with filler bulges less initially for 400 h than the rubber without filler, the same as in aqueous sodium hydroxide~ However, after that the weight of the samples of rubber with filler gradually increases but the weight of the samples with filler decreases. Therefore, the chemical resistance of the investigated chlorophene sodium hydroxide and sulfuric acid than in the solutions themselves.

r~dbbers is lower in vapors of aqueous

901