Gasoline Mixtures on Elastomers - American Chemical

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14 Effects of Ethanol/Gasoline and Methyl t-Butyl Ether/Gasoline Mixtures on Elastomers ISMAT A. ABU-ISA General Motors Research Laboratories, Polymers Department, Warren, MI 48090-9055

The effects of ethanol/gasoline and MTBE/gasoline mixtures on swell and tensile properties of selected automotive elastomers were determined and compared to those of methanol/gasoline mixtures. Two gasolines with aromatic content of 30% and 50% were used in this investigation. Equilibrium swell and tensile measurements were conducted using ASTM standard procedures. The results show that in the case of ethanol/gasoline combinations the elastomers were more severely affected by the mixtures than by the pure components. The ethanol/gasoline mixtures are less severe than the methanol/gasoline mixtures in their effects on most fuel resistant elastomers. In the case of MTBE the effects of mixtures with gasoline were an average of the effects of the pure components. The presence of a higher aromatic content in the gasoline resulted in increased swell and hence increased deterioration of tensile properties of elastomers exposed to the gasoline and its mixtures. Addition of benzene to increase the aromatic content resulted in slightly more detrimental effects on nitrile elastomers than the addition of toluene. The data on all elastomers can be explained in terms of the solubility parameter concept. For most elastomers the ultimate tensile and elongation values were found to be quantitatively related by simple linear equations to the volume fraction of the rubber swelled in mixtures of gasoline and ethanol or MTBE. They were also found to be related to each other by simple logarithmic relationships. Reprinted, with permission, from Rubber Chemistry and Technology, 56(1) 1983,169, American Chemical Society.

In The Effects of Hostile Environments on Coatings and Plastics; Garner, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

EFFECTS OF HOSTILE ENVIRONMENTS

226


Methanol, ethanol, and methy t - b u t y l ether (MTBE) are blended i n t o some commercial g a s o l i n e s . I t was important to determine the e f f e c t s of such blends on automotive elastomers e s p e c i a l l y those used i n the f u e l system, A summary of the r e s u l t s of our s t u d i e s [1] and d e t a i l e d data on the e f f e c t s of methanol/gasoline mixtures on s i x t e e n elastomers [2] have already been p u b l i s h e d . T h i s paper presents d e t a i l e d r e s u l t s of our i n v e s t i g a t i o n of the e f f e c t s of ethanol and MTBE mixtures with g a s o l i n e on mechanical and s w e l l p r o p e r t i e s of automotive elastomers. Comparisons w i l l be made with the e f f e c t s of methanol/gasoline mixtures on elastomers. Experimental The elastomers i n v e s t i g a t e d i n t h i s study are shown i n Table I along with t h e i r percent volume swell i n Indolene HO-III.

TABLE I Elastomers I n v e s t i g a t e d i n Ethanol/Gasoline and MTBE/gasoline Mixtures

Elastomer 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Fluorocarbon (*) P o l y e s t e r Urethane (*) Fluorosilicone E p i c h l o r o h y d r i n Homopolymer (*) B u t a d i e n e - A c r y l o n i t r i l e (*) Polyacrylate Chloroeulfonated Polyethylene (*) Ethylene-Acrylic Ethylene-Propylene-Diene Terpolymer (EPDM) (*) N a t u r a l Rubber

% Swell i n Indolene HO-III 0 11 14 19 34 44 49 84 137 169

(*) Elastomers a l s o i n v e s t i g a t e d i n MTBE/gasoline mixtures.

According to our previous d e f i n i t i o n [2] f i v e of the elastomers are considered to be f u e l r e s i s t a n t , three medium f u e l r e s i s t a n t and two poor f u e l r e s i s t a n t . The study of the e f f e c t s of ethanol/gasoline mixtures was c a r r i e d out for a l l ten elastomers. The study of MTBE/gasoline mixtures was conducted for s i x of the elastomers shown with a s t a r i n Table I . The elastomers were formulated using conventional curing agents, o i l s , carbon b l a c k and other i n g r e d i e n t s . The formulations of eight of the e l a s tomers have already been published i n a previous paper [2]. The


14.

ABU-ISA

Effects of Gasoline Blends on Elastomers

227

formulations of the remaining two elastomers, namely, e p i c h l o r o h y d r i n homopolymer and e t h y l e n e - a c r y l i c elastomer are shown i n Table I I . TABLE I I


Formulations of I p i c h l o r o h y d r i n Homopolymer and E t h y l e n e - A c r y l i c Elastomers

Ingredients 1.

E p i c h l o r o h y d r i n Homopolymer (x21889-33)*

Herclor H Stearic Acid Carbon Black N787 Carbon Black N550 D i o c t y l Phthalate Red Lead Irganox 1024** 2-Mercaptoimidazoline 2.

Concentration (phr)

1

2

100 1.0 90

100 1.0

-10 5·0 2.0 1.2

-

40 10 5.0 2.0 1.2

E t h y l e n e - A c r y l i c Elastomer (91950-296)***

VAMAC B-124 Octadecyl Amine Stearic Acid Carbon Black N760 Vanfre UN**** Hexamethylene Diamine Di-O-tolylguanidine

124 0.5 2.0 35 2.0 1.25 4.0

* Slabs of these compositions were obtained from H e r c u l e s . ** 1,2-bis[(3,5-di-tert-butyl-4-hydroxy) hydrocinnamylamide]hydraz ine *** Slabs of t h i s composition were obtained from DuPont. **** A f a t t y a l c o h o l phosphate mold r e l e a s e agent s u p p l i e d by R. T. V a n d e r b i l t .

As i n the methanol i n v e t i g a t i o n two g a s o l i n e s were used, namely, Indolene Η0-ΙΙΙ c o n t a i n i n g 30% aromatics, and "spiked" Indolene c o n t a i n i n g 50% aromatics. The second g a s o l i n e was prepared by adding 40 ml of toluene to 100 ml of Indolene Η0-ΙΙΙ. In one experiment 40 ml of benzene were added to 100 ml of Indo-


EFFECTS OF HOSTILE ENVIRONMENTS


228

lene HO-III i n order to determine the e f f e c t s of aromatic type on p r o p e r t i e s of elastomers exposed to high aromatic g a s o l i n e s . Mixtures of ethanol with Indolene HO-III and with "spiked" Indolene HO-III were prepared c o n t a i n i n g 5, 10, 15, 25, 50 and 75% a l c o h o l . Mixtures of s i m i l a r concentrations were a l s o prepared with MTBE. Three t e n s i l e bars and two volume change specimens of each elastomer were exposed i n a t e s t tube to each of the pure f u e l s and the mixtures. Exposure f o r 72 hours at room temperature was determined to be s u f f i c i e n t f o r most elastomers to approach e q u i l i b r i u m s w e l l . T e n s i l e p r o p e r t i e s were determined using the ASTM D412 procedure f o r o r i g i n a l samples and f u e l exposed samples immediately a f t e r removal from the f u e l . Swell measurements were conducted per the ASTM D471 procedure. To o b t a i n the amount of e x t r a c t a b l e s the f u e l swelled samples were d r i e d In a vacuum oven at 100°C f o r 24 hours and then weighed. In most samples constant weight was achieved w i t h i n t h i s time p e r i o d . The index of r e f r a c t i o n was measured at 15°C using Abbe-3L Bausch and Lomb refractomer and a Haake FK constant temperature bath. R e f r a c t i v e index was f i r s t measured f o r ethanol, Indolene HO-III, and mixtures of both components of known c o n c e n t r a t i o n s . From t h i s data c a l i b r a t i o n curves were obtained to r e l a t e component c o n c e n t r a t i o n with r e f r a c t i v e index. These c a l i b r a t i o n curves were used to determine whether or not p r e f e r e n t i a l absorpt i o n of one component of the mixture takes place during elastomer s w e l l i n g due to p e r m e a b i l i t y c o n s i d e r a t i o n s , or a f t e r e q u i l i b r i u m s w e l l i s e s t a b l i s h e d due to s o l u b i l i t y c o n s i d e r a t i o n s . R e s u l t s and D i s c u s s i o n E f f e c t s of the Composition of Ethanol/Gasollne Mixtures on the Volume Swell and T e n s i l e P r o p e r t i e s of Elastomers. The complete r e s u l t s on the e f f e c t s of v a r i o u s ethanol/Indolene blends on the ten elastomers i n v e s t i g a t e d i n t h i s study are shown i n Table I I I . Most of the elastomers e x h i b i t a maximum i n the volume change ( s w e l l ) versus c o n c e n t r a t i o n of ethanol p l o t s as seen i n F i g u r e 1 for b u t a d i e n e - a c r y l o n i t r i l e ( n i t r i l e ) elastomer. The maximum i n volume change i s accompanied by a minimum i n t e n s i l e s t r e n g t h and a minimum i n e l o n g a t i o n . Q u a n t i t a t i v e r e l a t i o n s h i p s between s w e l l and t e n s i l e s t r e n g t h and e l o n g a t i o n w i l l be d i s c u s s e d l a t e r i n t h i s paper. The value of maximum s w e l l and the l o c a t i o n on the curve r e l a t i v e to ethanol c o n c e n t r a t i o n depend on the type of polymer (Figure 2 ) . The f l u o r o c a r b o n elastomer e x h i b i t s low s w e l l i n ethanol, i n Indolene, and i n the mixtures. For polyurethane and c h l o r o s u l f o n a t e d polyethylene the polymers s w e l l s l i g h t l y to mode r a t e l y i n Indolene and e t h a n o l . The maximum s w e l l of these polymers i n mixtures of ethanol and Indolene i s moderate (40-56%) and occurs i n a mixture c o n t a i n i n g 15% e t h a n o l . For a c r y l a t e elastomer the s w e l l i n Indolene i s moderate (44%) but the s w e l l i n



Polyester Urethane

Pluorocarbon

Spiked Indolene

Indolene

Spiked Indolene

Indolene

0 5 10 15 25 50 75 100 0 5 10 15 25 50 75 0 5 10 15 25 50 75 100 0 5 10 15 25 50 75

18.3 15.2 12.7 12.3 12.7 12.3 13.0 12.9 14.6 15.2 13.8 12.6 11.8 12.5 14.5 14.1 23.0 20.1 12.9 12.4 12.3 12.0 12.9 13.0 17.1 14.5 11.9 10.6 10.2 8.8 10.6 12.3

Tensile Strength MPa 174 153 153 153 150 150 158 152 160 162 172 185 153 162 168 163 477 413 308 272 267 287 285 315 370 318 262 243 217 205 238 288

Elongation X 7.3 9.5 6.3 5.8 7.0 6.2 6.3 6.7 7.1 6.9 5.9 6.0 5.7 5.7 6.3 6.5 4.2 4.0 3.3 4.0 3.8 3.7 4.0 3.9 3.7 3.5 3.9 3.5 4.0 3.6 3.5 3.3

-_ -70 -

74

Durometer Shore A Points

11 29 37 39 40 33 31 19 24 41 51 54 55 49 33

-

0 3 3 4 4 4 3 2 3 5 6 7 7 4 4

Volume Change %

3 3 3 3 3 3 3 3 3 3 3 3 3 3

-3

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Extractables %

Table I I I — C o n t i n u e d on next

Modulus at 100% Elongation MPA

Effects of Ethanol/Gasollne Mixtures on Properties of Elastomers After Immersion for 72 Hours at Room Temperature

Table I I I



Eplchlorohydrin Homopolymer

Fluorosillcone

Elastomer

Spiked Indolene

Indolene

Spiked Indolene

Indolene

Gasoline 0 5 10 15 25 50 75 100 0 5 10 15 25 50 75 0 5 10 15 25 50 75 100 0 5 10 15 25 50 75

% Ethanol 7.5 6.7 5.1 4.9 4.7 4.1 4.5 4.3 5.6 6.0 4.9 4.3 4.6 4.7 4.7 4.6 16.1 12.4 11.3 11.2 9.1 10.8 10.4 12.4 14.2 9.9 8.0 7.5 6.8 7.3 7.9 10.3

Tensile Strength HPa

Modulus at 100% Elongation MPA 2.8 2.6 2.2 2.3 2.3 2.3 2.1 2.1 2.1 2.9 2.1 2.1 2.2 2.1 2.4 2.3 3.0 3.1 3.0 3.1 3.2 3.2 3.3 3.0 3.1 3.3 3.3 3.6 3.2 3.4 3.4 3.1

Elongation % 241 210 201 190 177 163 183 182 232 178 197 178 185 190 180 182 430 276 255 238 247 237 228 317 332 223 182 165 163 167 190 233

Table I I I — C o n t i n u e d

62 50 47 46 50 43 45 47 49 48 47 44 45 45 48 47 68 47 45 42 46 42 47 50 55 45 47 42 43 42 43 43

Duroraeter Shore A Points

-

5 5 5 5 5 3 2 6 6 6 6 7 6 6

-3

2 2 3 2 2 2 I 2 3 3 3 3 3 2 19 24 28 28 28 24 18 5 36 48 50 50 47 35 24

-2

16 18 18 17 18 13 6 16 19 20 20 19 19 12

Extractables %

-14

Volume Change %


Chloroeulfonated Polyethylene

Polyacrylate

Elastomer Butadiene-Acrylon i t r i l e (Nitrile)

Indolene

Spiked Indolene

Indolene

Spiked Indolene

Indolene

Gasoline

13.0

100

In The Effects of Hostile Environments on Coatings and Plastics; Garner, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1983. 202

100

173 187

9.0 12.3

25

10.5

9.5

15 50

132 148

8.1

10

75

142

8.8

5

222 148

53

17.3 10.7

43

1.7

0

47

1.7 1.6

50 75

50

25

40 45

1.6 1.6 1.9

5 15

47

10

1.8

2.5

100

0

67 80

45

1.7

1.9 2.2

60 47

2.2

15 25 50

62

2.2

10

75

63

2.3

188

5

153

7.3 8.6

50 75

300 122

132

10.2 3.7

133

6.5

15

0

123

6.3 6.8

10 25

152

7.4

5

157

7.5

0

317

175 230

8.1 9.6

25 50

173

8.1

15

75

195 175

7.3 7.1

10

172

Elongation % 383 208

7.2

Tensile Strength MPa 16.4 9.2

5

% Ethanol 0

48 47

50 54 55 65

4.6 4.5 4.1 4.0

4

4

3

3

3

76

63 38

51 45 52

4.7 4.5

-

4.2 8.8 5.2

5.6

5.6

5.7

6.4

13.0

-

-

-

2 2

138 101

48 52

2 2 2

182 179 143

50 49 46 51

1 1 1 0 0 0

57 48 38 17 1

1

I 56

54

Table I I I — C o n t i n u e d on next page

-

49

-

2 2 172

48

87

2 165 156

48

I

2 156 48

120

2 158 50

50

1 2

130 49

1

I 136

44

77

—

44 53 50

3.2

-

-

78

4

4

5

5

4

4

4

4.4

75

75

50 47

4.6 4.9

4.7 4.8

57 68

46 47

4.7

4

52

51

8

51

49

3.5 3.9

2

-

3

34

46

Extractables %

33

-

55 54

3.9

Volume Change %

4.3

71

Duroraeter Shore A Points

4.9

Modulus at 1 0 0 % Elongation MPA

Table I I I — C o n t i n u e d


2"

?8 ο

&

ζ/3 >

C

DO

>

§

-S

es

S

Bien ? on


Ethylene-Propylene Dlene Terpolymer

Ethylene-Acrylic

Spiked Indolene

Spiked Indolene

Spiked Indolene

-

0 5 10 15 25 50 75 100 0 5 10 15 25 50 75

-

0 5 10 15 25 50 75 100 0 5 10 15 25 50 75

0 5 10 15 25 50 75

Ζ Ethanol 5.3 5.9 5.6 6.8 5.3 7.5 13.2 16.5 4.6 4.3 3.8 3.8 3.8 4.1 5.1 7.3 3.8 3.6 3.5 3.4 3.5 3.7 3.8 9.1 3.3 3.9 3.8 4.2 4.3 4.2 6.1 10.6 3.8 3.8 3.8 4.3 4.4 4.6 6.6

Tensile Strength MPa 135 133 112 82 130 155 172 428 125 98 75 65 68 80 113 185 80 67 55 57 57 65 88 217 88 83 80 92 87 93 147 237 72 77 75 80 93 95 160

Elongation %

3.7

3.5

3.6 3.7

3.2

4.5

3.6 3.7 7.0 3.3 4.1

39 36 39 37 37 37 36 38 39 39 44 42 38 40 38 67 45 48 50 45 48 42 47 68 46 46 48 50 45 40 47

-

137 131 124 114 107 94 47 13 146 133 118 115 100 79 43

-

84 130 149 174 187 168 108 55 174 210 221 233 237 195 119

77 77 81 76 73 52 24

_

3.2 4.1 5.0

70

Volume Change %

Durometer Shore A Points

Modulus at 100% Elongation MPA

Table I l l — C o n t i n u e d


-

18 18 19 18 17 10 4 2 18 18 18 18 17 10 4

-

5 6 6 7 7 8 6 4 4 4 4 5 5 6 4

2 2 2 2 2 1 0

Extractables %

in

H

m •ζ

I

r m m •z

Gasoline Mixtures on Elastomers - American Chemical

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