Comparison of Diol Cross-Linkers in Castable Urethane Elastomers

34

Downloaded by UNIV OF TENNESSEE KNOXVILLE on February 13, 2017 | http://pubs.acs.org Publication Date: November 30, 1981 | doi: 10.1021/bk-1981-0172.ch034

Comparison of Diol Cross-Linkers in Castable Urethane Elastomers I. SIOUN LIN, JEROME BIRANOWSKI, and DONALD H. LORENZ Polymer Department, GAF Corporation, 1361 Alps Road, Wayne, NJ 07470

There are regulatory and handling problems in using methylene bis(2-chloroaniline) as a chain extender (curative or cross-linker) for toluene diisocyanate (TDI)-terminated prepolymers, to produce urethane elastomers (1,2). There is, therefore, a strong interest in achieving similar elastomer properties with other curatives and methylene diphenyl diisocyanate (MDI)-terminated prepolymers(3,4). EXPERIMENTAL A.

Materials

The materials used are listed in Table I. All curatives were dried overnight at 80ºC in vacuum. MDI prepolymer were used as received. B.

Polyurethane Elastomer Preparation

Amine stoichiometry was kept at 95% based on prepolymer con tent. Except where noted, prepolymers were preheated at 93°C and mixed with curatives at desired temperature. The prepolymer, cur ative and prepolymer-curative mixture were each vacuum degassed prior to pouring the mixture into a preheated mold. Degassing before and after mixing is especially important to achieve optimum cures. The mold was closed when gelation started. Demolding time was one hour or less. The sample was then post-cured for 16 hours at 120°C. The elastomer was conditioned for one week at 50% rela tive humidity at room temperature prior to physical properties measurement. B.

Physical

Testing

A f t e r the samples had been aged and c o n d i t i o n e d , the f o l l o w i n g t e s t s were run according t o the f o l l o w i n g s p e c i f i c a t i o n s : 1. 2. 3.

Shore Hardness Durometer A ASTM D-2240 S t r e s s - S t r a i n P r o p e r t i e s ASTM D-412 Tear Resistance Grave, d i e C, p l i ASTM D-624 0097-6156/81/0172-0523$05.00/0 © 1981 American Chemical Society

Edwards et al.; Urethane Chemistry and Applications ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

524

URETHANE CHEMISTRY AND

APPLICATIONS

R e s i l i e n c e (Rebound, Bashore) ASTM D-2632 Compression set Method Β (22 h r s . at 70°C) ASTM D-395 RESULTS AND DISCUSSION


4. 5.

Urethane elastomers based on MDI type prepolymer extended w i t h 1,4-butanediol and other c u r a t i v e s have been formulated. The r e s u l t s o f t h i s work are summarized i n Tables I I - I V . In g e n e r a l , p o l y e t h e r and polyester-based urethane elastomers both have e x c e l l ent p h y s i c a l p r o p e r t i e s . There are s e v e r a l d i f f e r e n c e s between them. Among them a r e : (1) P o l y e s t e r s u s u a l l y are more v i s c o u s at p r o c e s s i n g temperatures, making p r o c e s s i n g d i f f i c u l t . (2) P o l y e s t e r g e n e r a l l y have s h o r t e r pot l i f e than p o l y e t h e r s . (3) P o l y ether-based urethanes e x h i b i t h i g h e r r e s i l i e n c e and lower com p r e s s i o n s e t . I t appears t h a t diamine c u r a t i v e (Polacure) i s more r e a c t i v e than g l y c o l s . 1,4-Butanediol/MDI systems show not n e a r l y as much s e n s i t i v i t y to s t o i c h i o m e t r y as ethylene g l y c o l or p o l y o l 50-1180. HQEE and Polacure have r e l a t i v e l y low t e n s i l e s t r e n g t h and h i g h compression s e t . However, both gave improved elastomer hardness and t e a r s t r e n g t h . V i b r a c u r e cured elastomers have ap p r o x i m a t e l y the same p h y s i c a l p r o p e r t i e s as HQEE cured urethanes This may be due to t h e i r chemical composition. S i m i l a r r e s u l t s a l s o found i n ethylene glycol/MDI and p o l y o l 50-1180/MDI systems. The c o n c l u s i o n s which can be drawn from t h i s work are summarized as f o l l o w s : 1.

2.

3.

4.

1,4-Butanediol v s . Ethylene G l y c o l a)

Stoichiometry less sensitive

b)

I n f e r i o r on compression set c h a r a c t e r i s t i c s

1,4-Butanediol v s . P o l y o l 50-1180 a) b)

Stoichiometry less sensitive S u p e r i o r t e n s i l e modulus, t e a r s t r e n g t h and rebound

c)

I n f e r i o r on compression set

1,4-Butanediol v s . HQEE a)

S u p e r i o r t e n s i l e and rebound

b)

Somewhat i n f e r i o r t e a r and e l o n g a t i o n

1,4-Butanediol v s . V i b r a c u r e same as HQEE

5.

6.

1,4-Butanediol v s . Polacure a) S u p e r i o r t e n s i l e and compression set b) I n f e r i o r i n modulus and t e a r 1,4-Butanediol v s . 4,4 -Methylene b i s ( 2 - c h l o r o a n i l i n e ) (published p r o p e r t i e s ) a) Superior t e n s i l e modulus, t e n s i l e and t e a r b) Inferior i n elongation 1


34.

LIN ET AL.

525

Diol Cross-Linkers

TABLE I - MATERIALS


1,4-Butanediol (B^D) Ethylene g l y c o l (EG) 4,4'-Methylene b i s (2-chloroaniline) (MOCA) Hydroquinone b i s (2-hydroxyethyl) ether (HQEE) Trimethylene g l y c o l di-p-aminobenzoate (Polacure #740M)

Eq. Wt.

Chemical

45.06

HOCH CH CH CH OH

31.03

2

2

Composition

2

2

HOCH CH OH 2

H

2

N ^ — C H

2

r

© - N H

2

133.5

99

HOCH CH O^OCH CH OH 2

2

2

2

H N

157

2

^y

( C H

2

) 3

°-C-^-NH

P o l y o l 50-1180

47.26

Mixture o f ethylene g l y c o l p l u s short c h a i n d i o l

V i b r a c u r e 3095

97.86

HQEE p l u s other c u r a t i v e

Toluene d i i s o cyanate (TDI)

87

80/20, 2,4/2, 6 - t o l y l e n e d i i s o c y a n a t e , a mixture o f isomers

Methylene d i p h e n y l diisocyanate (MDI)

125

OCN-

2

NCO

Vibrathane B-635

530 +_ 15

Polytetramethylene ether g l y c o l - b a s e d MDI prepolymer

Vibrathane 6020

665 +_ 25

Polyester-based MDI p r e polymer

Adiprene L-100

1050

Polytetramethylene ether g l y c o l - b a s e d TDI prepolymer

Adiprene APX 381

1072

P o l y e s t e r based TDI prepolymer


526

URETHANE

CHEMISTRY AND APPLICATIONS

TABLE I I - P r o p e r t i e s o f Elastomers Prepared from Polyester-MDI Prepolymer (Vibrathane 6020) Cured w i t h B.D, EG, HQEE Polacure No. 740M, P o l y o l 50-1180 and V i b r a c u r e 3095.


Formulation VIBRATHANE 6020 (AE=640 + 2 5 ) , 1,4-Butanediol, Ethylene g l y c o l , HQEE , Polacure No. 740M, P o l y o l 50-1180 , V i b r a c u r e 3095 , C u r a t i v e Mole R a t i o ,

1

2

3

100

100

100

g g g g g g g

6.64 4.70 14.97

0.95

0.95

0.95

60 93

60 93

120 93

60/93

60/93

120/93

Conditions C u r a t i v e , Temp., °C VIBRACURE 6020, Temp.°C Mix. Temp. °C (curative/prepolymer Pot L i f e at Mix. Temp., min. Cured i n Mold.min/°C Post Cure, hrs/°C

8

7

3

60/120 24/120

60/120 16/120

60/120 16/120

85 35

84 35

97 44

Physical Properties Hardness, Shore A Shore D 100% Modulus, p s i (MPa)

866 (6.0)

892 (6.2)

1578 (10.8)

300% Modulus, p s i (MPa)

1498 (10.4)

1624 (11.2)

2001 (13.8)

T e n s i l e Strength, p s i (MPa)

6427 (44.4)

5385 (37.2)

4265 (29.4)

Elongation, %

555

Tear Strength, Die C, p l i 543 (kN/m) (95)

581

650

596 (104.3)

754 (131.9)

Bashore Rebound, %

37

32

27

Compression S e t , 22 Hrs/70°C Method B, %

40

30

25


34.

LIN ET AL.

TABLE I I (cont'd.)

P r o p e r t i e s o f Elastomers Prepared from Polyester-MDI Prepolymer (Vibrathane 6020) Cured w i t h Β D, EG, HQEE Polacure No. 740M, P o l y o l 50-1180 and V i b r a c u r e 3095.

Formulation Downloaded by UNIV OF TENNESSEE KNOXVILLE on February 13, 2017 | http://pubs.acs.org Publication Date: November 30, 1981 | doi: 10.1021/bk-1981-0172.ch034

527

Diol Cross-Linkers

VIBRATHANE 6020 (AE=640 +_ 25), 1, 4-Butanediol, Ethylene g l y c o l , HQEE , Polacure No. 740M, P o l y o l 50-1180, V i b r a c u r e 3095, C u r a t i v e Mole R a t i o ,

1

2

3

100

100

100

— — —

— — — —

—

g g g g g g g

23.07

--

— —

6.69

0.95

0.95

125 93

60 93

—

— —

--

15.02 0.95

Conditions C u r a t i v e , Temp., °C VIBRATHANE 6020, Temp °C Mix. Temp. °C (curat ive/prepo1ymer Pot L i f e at Mix. Temp., min. Cured i n Mold. min/°C Post Cure, hrs/°C

125/93 1 30/120 16/80

120 93

60/93 10

120/93 7

15

60/120 16/120

60/120 16/120

96 43

Physical Properties Hardness, Shore A Shore D

55

75 30


1782 (12.3)

490 (3.4)

1372 (9.5)


2324 (16.0)

1125 (7.8)

2040 (14.1)

T e n s i l e Strength, p s i (MPa)

4070 (28.1)

6164 (42.5)

4680 (32.3)

544

526

478 (83.6)

725 (126.8)

Elongation, % Tear S t r e n g t h , Die C, p l i (kN/m)

550 800 (140.0)

Bashore Rebound, %

42

24

34

Compression Set, 22 Hrs/70°C Method B, %

39

20

29


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URETHANE CHEMISTRY AND

APPLICATIONS

TABLE I I I - P r o p e r t i e s o f Elastomers Prepared from Polyether-MDI Prepolymer (VIBRATHANE B-635) Cured w i t h B.D, EG, HQEE, Polacure No. 740M, P o l y o l 50-1180 and Vibracure 3095. Formulation


VIBRATHANE B-635 (AE-530 + 15), 1,4-Butanediol, Ethylene g l y c o l , HQEE, Polacure No. 740M, P o l y o l 50-1180, V i b r a c u r e 3095, C u r a t i v e Mole R a t i o

1

2

3

100

100

100

g 8.31

g g g g g g

6.24

—

17.93

— —

—

—

—

—

—

—

0.95

0.95

1.05

60 93

60 93

60/93

60/93

120/93

20

10

Conditions C u r a t i v e , Temp. °C VIBRATHANE B-635, Temp.°C Mix. Temp., °C (Curat ive/Prepo1ymer) Pot L i f e a t Mix. Temp,, ,min.

7

120 93

Cured i n Mold, min/°C

60/120

60/120

60/120

Post Cure, hrs/°C

16/120

16/120

16/120

Hardness, Shore A Shore D

93 37

84 31

55


1386 (9.6)

1089 (7.5)

2433 (16.8)


3778 (26.1)

—

2783 (19.2)

T e n s i l e Strength, p s i (MPa) Elongation, %

6115 (42.2) 338

5788 (39.9) 268

3450 (23.8) 432

590 (103.2)

423 (74.0)

680 (119.0)

Bashore Rebound, %

39

19*

42

Compression S e t , 22 hrs/70 C Method Β, %

24

18

31

Physical Properties

Tear S t r e n g t h , Die C, p l i (kN/m)

e

*sample was s o f t and s t i c k y a f t e r demolding.


—

34.

LIN ET AL.

Diol Cross-Linkers

529

TABLE I I I - P r o p e r t i e s o f Elastomers Prepared from Polyether-MDI (cont'd.) Prepolymer (Vibrathane B-635) Cured w i t h B.D, EG,HQEE, Polacure No. 740M, P o l y o l 50-1180 and Vibracure 3095. Formulation


VIBRATHANE B-635 (AE-530 + 15), 1,4-Butanediol, Ethylene g l y c o l , HQEE, Polacure No. 740M, P o l y o l 50-1180, V i b r a c u r e 3095, C u r a t i v e Mole R a t i o

100

100

100

28.44 8.56 0.95

0.95

17.39 0.95

125 80

60 93

120 93

125/80 (40 sec) 30/120 16/80

60/93 10 60/120 16/120

60/93 10 60/120 16/120

60

82 31

52

Conditions C u r a t i v e , Temp. °C VIBRATHANE B-635, Temp. °C Mix. Temp., °C (Curative/Prepolymer Pot L i f e a t Mix. Temp., min. Cured i n Mold, min/°C Post Cure, hrs/°C Physical Properties Hardness, Shore A Shore D 100% Modulus, p s i (MPa)

3160 (21.8)

919 (6.4)

2224 (15.4)


4868 (33.6)

3610 (24.9)

2641 (18.2)

Tensile Strength, p s i (MPa)

5335 (36.8)

4681 (32.3)

4000 (27.6)

342

305

466

871 (152.4)

415 (72.6)

657 (115)

Elongation, % Tear S t r e n g t h , Die C, p l i (kN/m) Bashore Rebound, %

40

15*

35

Compression S e t , 22 hrs/70°C Method B, %

50

19

29

*Sample was s o f t and s t i c k y a f t e r demolding.


530

URETHANE CHEMISTRY AND APPLICATIONS

TABLE IV - GENERAL SUMMARY OF PHYSICAL PROPERTIES Compound

B DVMDI 1

Polyether-MDI prepolymer

M0CA*/TDI

100

ADIPRENE APX-381


Polacure*/TDI

100

ADIPRENE L-100

100

Polacure No. 740M

14.2

MOCA

12.5

1,4-Butanediol

8.31

C u r a t i v e Mole Ratio

0.95

0.95

0.95

Mixing and Curing Polymer Mix Temp. °C Cured: hours/°C Pot L i f e

93 16/120 7

100 16/120 4

93

93

100 3/100 10-12

Physical Properties Hardness, Shore D 100% Modulus, p s i (MPa) 300% Modulus, p s i (MPa) T e n s i l e Strength, p s i (MPa) Elongation, %

1386 (9.6)

1100 (7.6)

1100 (7.6)

3778 (26.1)

2200 (15.2)

2100 (14.5)

6115 (42.2)

6425 (44.3)

4500 (31.0)

338

Tear Strength, Die C, p l i 590 (kN/m) (103.3) Bashore Rebound, %

90

460 350 (61.3)

450 240 (42.0)

39

40 40

Compression Set, 22 hrs/70 C Method B, % e

24

27 42

*Data from 1978 F a l l Meeting PMA, Point C l e a r , Alabama, October, 1978.

1,4-Butanediol



34.

LIN ET AL.

DM Cross-Linkers

531

These data show t h a t urethane elastomers based on MDI type p r e polymer cured w i t h 1,4-butanediol e x h i b i t e q u i v a l e n t o r even b e t t e r p h y s i c a l p r o p e r t i e s , such as t e n s i l e s t r e n g t h , compression set, r e s i l i e n c e , t e a r s t r e n g t h and e l o n g a t i o n when compared t o e l a s t o mers extended w i t h methylene b i s ( 2 - c h l o r o a n i l i n e ) , t r i m e t h y l e n e g l y c o l di-p-aminobenzoate o r hydroquinone b i s ( 2 - h y d r o x y e t h y l ) ether i n MDI o r TDI system (at equal hardness). Other advantages f o r 1,4-butanediol c u r a t i v e are low t o x i c i t y , l i q u i d s t a t e a t room temperature, ease o f h a n d l i n g and lower cost than o t h e r well-known curatives.

REFERENCES 1. Polaroid Corporation, Recent Developments in the Use of Polacure® No. 740M Diamine Curative, October, 1978. 2. Polaroid Corporation, Trimethylene Glycol Di-p-Aminobenzoate - A Development Diamine Curative for Cast Elastomers, October, 1977. 3. The Quaker Oats Company, Polyurethane Elastomers Based on MDI-QO® Polymeg® Prepolymer Extended with 1,4-Butanedio1,1976. 4. Uniroyal Chemical, MDI-Prepolymer Systems - Viable Alterna tives to MOCA Cured Urethanes. April 18, 1978. RECEIVED April 30,

1981.


Comparison of Diol Cross-Linkers in Castable Urethane Elastomers

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