Influence of Molecular Structure and Substituents on Antiozonant Properties of Aryl Diamine Compounds A. D. DELMAN, A. E. RUFF, Β. B. SIMMS, and A. R. ALLISON
Downloaded by UNIV OF TEXAS EL PASO on January 5, 2015 | http://pubs.acs.org Publication Date: January 1, 1959 | doi: 10.1021/ba-1959-0021.ch027
U. S. Naval Material Laboratory, New York Naval Shipyard, New York, Ν. Y.
The influence of molecular structures a n d substituents on the antiozonant properties of a series of related aromatic diamine compounds was studied. The rela tive effectiveness of the compounds was determined by viscometric techniques and by comparison of the rate of degradation of protected vulcanizates. Re sults indicate that unsymmetrical p-phenylenediamine derivatives are less effective than analogous sym metrical compounds as antiozonants. The protective capacity of the antiozonants decreases as the size or number of the N-hydrogen substituents, or the dis tance between the amine groups, increases. The comparative stability of the free radicals of aryl diamines, in terms of the theory of resonance, is utilized to explain the relative inhibiting properties of the chemicals examined.
Degradation of elastomers d u r i n g w e a t h e r i n g is n o w g e n e r a l l y a c c e p t e d as d u e l a r g e l y to t h e p o w e r f u l o x i d i z i n g p r o p e r t i e s of a t m o s p h e r i c ozone. D u r i n g t h e f a b r i c a t i o n of rubber a n d synthetic rubber items, manufacturers have attempted to improve the resistance of t h e i r p r o d u c t s t o ozone d e t e r i o r a t i o n b y u t i l i z i n g c h e m i c a l a d d i t i v e s , k n o w n as a n t i o z o n a n t s . A l t h o u g h t h e a d d i t i o n of s u c h c h e m i c a l s as a r o m a t i c a m i n e s has e x t e n d e d c o n s i d e r a b l y t h e s e r v i c e life of r u b b e r v u l c a n i z a t e s , t h e y a r e s t i l l s u b j e c t t o c o m p a r a t i v e l y e a r l y surface c r a c k i n g . F o r t h i s reason, a f u n d a m e n t a l s t u d y w a s m a d e of t h e v a r i o u s c h e m i c a l a d d i t i v e s u s e d c u r r e n t l y t o d e t e r m i n e w h e t h e r m o l e c u l a r s t r u c t u r e a n d s u b s t i t u e n t g r o u p s influence t h e i r a n t i o z o n a n t p r o p e r t i e s . A simple, r a p i d , a n d reliable viscometric technique for evaluating the protective c a p a c i t y of c o m m e r c i a l l y a v a i l a b l e m a t e r i a l s as i n h i b i t o r s of o z o n e - i n d u c e d polymer c h a i n scission h a s b e e n d e s c r i b e d (1). T h i s w o r k i n c l u d e d t h e results of a n e v a l u a t i o n of s e v e r a l c h e m i c a l s s u c h as A ^ i V ' - d i - s e c - b u t y l - p - p h e n y l e n e d i a m i n e , n i c k e l d i b u t y l d i t h i o c a r b a m a t e , l - ( r a - a m i n o p h e n y l ) - 2 , 5 - d i m e t h y l p y r r o l e , a n d 2,6-di-£er£-butyl-4-methylp h e n o l as a n t i o z o n a n t s ; i V , i V - d i - s e c - b u t y l - p - p h e n y l e n e d i a m i n e e x h i b i t e d s u p e r i o r i n h i b i t i n g c h a r a c t e r i s t i c s . H o w e v e r , because of t h e p o t e n t i a l t o x i c effects a n d r e l a t i v e l y h i g h v a p o r p r e s s u r e of t h i s c h e m i c a l , i t s use is c o n s i d e r e d i m p r a c t i c a l . A m e t h o d w a s r e p o r t e d (2) f o r m o d i f y i n g t h e m o l e c u l a r s t r u c t u r e of N,N'-di-secb u t y l - p - p h e n y l e n e d i a m i n e t o m a k e i t m o r e s u i t a b l e f o r use as a r e t a r d e r of t h e effects 176
In OZONE CHEMISTRY AND TECHNOLOGY; Advances in Chemistry; American Chemical Society: Washington, DC, 1959.
177
DELMAN, RUFF, SIMMS, A N D ALLISON—ARYL DIAMINE C O M P O U N D S
of ozone o n e l a s t o m e r s . S e v e r a l w o r k e r s ( 7 , 11, 12) d e v e l o p e d a d d i t i o n a l p - p h e n y l e n e d i a m i n e d e r i v a t i v e s f o r t h i s p u r p o s e . A n u m b e r of t h e c h e m i c a l s — e . g . , N,N'-aip h e n y l - p - p h e n y l e n e d i a m i n e , A ^ , i V - d i - 2 - n a p h t h y l - p - p h e n y l e n e d i a m i n e , a n d i s o m e r s of A f j A ^ - d i o c t y l - p - p h e n y l e n e d i a m i n e — a r e n o w a v a i l a b l e c o m m e r c i a l l y f o r use b y r u b b e r r
/
compounders. T h i s p a p e r p r e s e n t s t h e r e s u l t s of a n i n v e s t i g a t i o n of some of t h e a b o v e m a t e r i a l s a n d o t h e r s t r u c t u r a l l y r e l a t e d a r y l d i a m i n e c h e m i c a l s . D a t a a r e also p r e s e n t e d o n t h e c o m p a r a t i v e i n h i b i t i n g p r o p e r t i e s of t h r e e r e p r e s e n t a t i v e p r o t e c t a n t c h e m i c a l s u s e d as additives i n typical S B R vulcanizates.
Downloaded by UNIV OF TEXAS EL PASO on January 5, 2015 | http://pubs.acs.org Publication Date: January 1, 1959 | doi: 10.1021/ba-1959-0021.ch027
Experimental Test C o m p o u n d s . T h e aromatic diamine chemicals were obtained f r o m various c o m m e r c i a l sources a n d u s e d w i t h o u t f u r t h e r m o d i f i c a t i o n . A l i s t of these m a t e r i a l s is p r e s e n t e d i n T a b l e I . Table I.
A r y l Diamine Additives ν
Hs y
P-PHENYLENEDI AMINE
S"
*'
Η >N 3 H /CH
N,N'-DIMETHYL-P-PHENYLENE DIAMINE
Η
/
Ν
/
S
Ν,Ν'-DIETHYL-P- PHENYLENEDI AMINE ÇH C
N.N'-DI-SEG-BUTYL-P-PHENYLENEDIAMINE
2
H
5
ÇH N.N'-DI-SEC-N-OCTYL-P-PHENYLENEDIAMINE
ÇH
3
C H
N
N
CH
3
CH (CH ) CH\ >,NV H' 3
2
5
Ç 3 fz 5 N N'-DI-3(5-METHYL HEPTYU-P-PHENYLENEDIAMINE C HjCHC^CHs^ > H
H
2
t
Ν,Ν'-DIPHENYL-P-PHENYLENEDIAMINE
< Z >
N,N'-DI-2-NAPHTHYL-P-PHENYLENEDI AMINE
N
H
5
5
^ /CHICH ) CH >N H 2
S
3
N
f2 5 C H ν /CHCH CHC H H
3
N
