Adhesives from Renewable Resources - American Chemical Society

Downloaded by UNIV OF PITTSBURGH on May 3, 2015 | http://pubs.acs.org Publication Date: December 31, 1989 | doi: 10.1021/bk-1989-0385.ch030

Chapter 30 Polyurethanes from Renewable Resources J o h n L. Stanford, R i c h a r d H. S t i l l , J o h n L. Cawse , and M i c h a e l J. Donnelly Wolfson Polymer Research Unit Department of Polymer Science and Technology University of Manchester Institute of Science and Technology Manchester, M60 1QD, England 1

2

Liquid polyols and diisocyanates specially synthesized from renewable resource materials have been used in separate studies to form various polyurethanes. The polyols studied were hydroxy-functionalized polytetrahydrofuran monoglucoside and bisglucoside, and polymyrcene prepolymers. The polyols, characterized by end-group analysis, GPC, V P O and NMR, were reacted with 4,4'-methylene diphenylene diisocyanate (MDI) to form materials ranging from segmented copolyurethane elastomers to rubber-toughened, glassy polyurethane resins. In addition, different furan-based diisocyanates (FDI) with structures analogous to MDI were synthesized and characterized by elemental analysis, IR and NMR. Comparative kinetics studies indicated that FDI reactivities were intermediate between those of MDI and alkyl diisocyanates. FDI-based segmented copolyurethanes were formed using mixtures of polytetrahydrofuran and 1,4-butanediols. Polyurethane materials were evaluated by DSC, dynamic mechanical, tensile stress-strain, and fracture measurements. The feasibility of deriving liquid polyols and diisocyanates for polyurethane formation from agricultural and wood wastes is discussed. P o l y u r e t h a n e s are a versatile class o f p o l y m e r s d u e m a i n l y t o t h e i r r a p i d a n d easy processing a n d t o some excellent c h e m i c a l a n d p h y s i c a l p r o p e r t i e s , w h i c h can b e t a i l o r e d t o s u i t a very w i d e range o f a p p l i c a t i o n s (1) i n c l u d i n g b u l k C u r r e n t a d d r e s s : Ilford L t d . K n u t s f o r d , C h e s h i r e , W A 1 6 7 H A , U K 2

C u r r e n t a d d r e s s : C o u r t a u l d s R e s e a r c h , R O . B o x 111, C o v e n t r y , C V 6 5 R S , U K 0097-6156/89/0385-0424$06.00/0 © 1989 A m e r i c a n Chemical Society

In Adhesives from Renewable Resources; Hemingway, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.

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Polyurethanes from Renewable Resources

425


p l a s t i c s , elastomers, fibers, foams, surface coatings, a n d s p e c i a l i z e d adhesive p r o d u c t s . T y p i c a l l y , the reactants used t o f o r m h o m o p o l y u r e t h a n e s are p o l y isocyanates a n d p o l y o l s or, i n the case of segmented c o p o l y u r e t h a n e s , p o l y o l s b l e n d e d w i t h c h a i n extenders s u c h as ethylene g l y c o l or 1 , 4 - b u t a n e d i o l . T h e s e reactants are generally o b t a i n e d f r o m o i l - b a s e d sources. T h e c h e m i c a l a n d m o r p h o l o g i c a l s t r u c t u r e a n d final properties o f p o l y u r e thanes d e p e n d m a i n l y o n p o l y o l s t r u c t u r e , m o l a r mass, a n d f u n c t i o n a l i t y , a n d , t o a lesser e x t e n t , o n the n a t u r e o f the p o l y i s o c y a n a t e . T h e s t o i c h i o m e t r i c r a t i o of i s o c y a n a t e to h y d r o x y l groups, the a m o u n t o f c h a i n extender used, a n d the processing m e t h o d also have significant effects o n p o l y u r e t h a n e p r o p e r t i e s (2). T h e p o l y o l s used are u s u a l l y h y d r o x y - t e r m i n a t e d p o l y e t h e r - or polyester-based l i q u i d s w i t h m e a n m o l a r masses i n the range 500 t o 7,000 g - m o l " a n d f u n c t i o n a l i t i e s o f 2 ( d i o l s ) , 3 ( t r i o l s ) , a n d 4 (tetrols). O t h e r low f u n c t i o n a l i t y h y d r o x y prep o l y mers are used, n o t a b l y the l i q u i d r u b b e r s (2) based o n p o l y b u t a d i e n e and butadiene-acrylonitrile copolymers. Higher functionality polyols, although d e r i v e d f r o m n o n o i l - b a s e d p o l y h y d r i c c o m p o u n d s such as s o r b i t o l a n d sucrose, t e n d t o result i n the f o r m a t i o n o f stiff, b r i t t l e p o l y u r e t h a n e s a n d are used m a i n l y for r i g i d f o a m p r o d u c t i o n . 1

T h e m a j o r p o l y i s o c y a n a t e s used (2) are toluene d i i s o c y a n a t e ( T D I ) a n d the less v o l a t i l e 4 , 4 - m e t h y l e n e d i p h e n y l e n e d i i s o c y a n a t e ( M D I ) , w h i c h , because i t is a c r y s t a l l i n e s o l i d i n the pure f o r m , has t o be used i n a r e l a t i v e l y " c r u d e " f o r m . T h e crude p o l y i s o c y a n a t e is a m i x t u r e of M D I v a r i a n t s t h a t is conven i e n t l y a l i q u i d p r o d u c t w i t h a m e a n f u n c t i o n a l i t y greater t h a n 2. T h e use of a p u r e , l i q u i d d i i s o c y a n a t e , however, w o u l d enable p o l y u r e t h a n e s t o be f o r m e d h a v i n g r e l a t i v e l y enhanced p h y s i c a l properties (2) a n d w o u l d also g r e a t l y s i m p l i f y processing b y r e m o v i n g the need to use elevated t e m p e r a t u r e s , solvents, or i s o c y a n a t e p r e p o l y m e r s as w i t h M D I . /

T h i s chapter presents the results of studies o n the syntheses a n d c h a r a c t e r i z a t i o n o f novel l i q u i d p o l y o l s (3-6) a n d diisocyanates (7,8), a n d t h e i r use i n the f o r m a t i o n o f v a r i o u s p o l y u r e t h a n e m a t e r i a l s . T h e p o l y o l s are o f t w o different s t r u c t u r a l types, n a m e l y 1) l i q u i d p o l y t e t r a h y d r o f u r a n ( P T H F ) glycosides d e r i v e d f r o m glucose a n d P T H F diols a n d 2) l i q u i d r u b b e r s t h a t are h y d r o x y f u n c t i o n a l , s u b s t i t u t e d b u t a d i e n e p r e p o l y m e r s derived f r o m myrcene. G l u c o s e a n d the f u r a n - b a s e d P T H F d i o l s , the precursors to the l i q u i d glycosides, are b o t h r e a d i l y a v a i l a b l e f r o m n a t u r a l l y o c c u r r i n g c a r b o h y d r a t e sources. T h e p r e cursor t o the l i q u i d r u b b e r , m y r c e n e , is a terpene o b t a i n a b l e f r o m the t u r p e n t i n e f r a c t i o n o f b l a c k l i q u o r p r o d u c e d essentially as a waste p r o d u c t i n the s u l p h i t e w o o d - p u l p i n g process used i n p a p e r m a k i n g . T h e l i q u i d d i i s o c y a n a t e s are pure d i f u n c t i o n a l c o m p o u n d s , analogous i n s t r u c t u r e t o p u r e M D I , a n d are based o n f u r a n a n d i t s derivatives, c o m m e r c i a l l y a v a i l a b l e i n large q u a n t i t i e s f r o m a g r i c u l t u r a l waste p r o d u c t s s u c h as c o r n cobs a n d oat husks. C o m p a r a t i v e studies are presented t h a t d e m o n s t r a t e t h a t h o m o p o l y u r e t h a n e a n d segmented c o p o l y u r e t h a n e elastomers a n d p l a s t i c s a n d r u b b e r - m o d i f i e d p o l y u r e t h a n e glasses w i t h properties s i m i l a r t o c o u n t e r p a r t s f o r m e d f r o m o i l -


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ADHESIVES F R O M R E N E W A B L ERESOURCES

based reactants c a n b e derived f r o m t h e renewable resource p o l y o l s a n d d i i s o cyanates. Polyurethanes Based o n Polytetrahydrofuran Glycosides


L i q u i d Polyols f r o m Glucose: Synthesis a n d Characterization. L i q u i d p o l y o l s were p r e p a r e d f r o m α-D-glucose ( 1 ) a n d t h e a g l y c o n , a P T H F d i o l ( 2 ) , by a c i d - c a t a l y z e d reactions under n i t r o g e n a t 130 ° C i n N - m e t h y l p y r r o l i d o n e , N M P , s o l u t i o n s (6-9).

Cr^OH π HO

/\0H

Η

Γ|Λ

OH

HO-ftfrtfrO-jn-H

η

R e a c t i o n o f one m o l e o f glucose w i t h one m o l e o f the a g l y c o n y i e l d s P T H F m o n o g l u c o s i d e ( 3 ) , whereas r e a c t i o n o f t w o moles o f glucose w i t h one o f t h e a g l y c o n y i e l d s P T H F - b i s g l u c o s i d e ( 4 ) . T h e p r o d u c t s are m i x t u r e s o f anomers

ÇH 0H 2

HO^J^Q-hcH^O^H H OH

CHjOH

HoVjA-fiC^ H OH

(ca. 8 0 % w / w ) together w i t h more c o m p l e x p r o d u c t s (ca. 2 0 % w / w ) as s h o w n by O t e y (10) for ethylene g l y c o l glucoside ( E G G ( 5 a - c ) ) d e r i v e d f r o m s t a r c h v i a a t r a n s g l y c o s i d a t i o n r e a c t i o n , in bulk, u s i n g excess ethylene g l y c o l . T h u s , structures 3 a n d 4 are i d e a l i z e d representations o f the c h e m i c a l structures o f


30.

427

Pofyurethanes from Renewable Resources

S T A N F O R D E T A L

the P T H F - g l u c o s i d e s a n d a c t u a l l y depict the α-anomers, P T H F - m o n o or bis-o> glucosides t h a t are present i n the m i x e d p r o d u c t .


cx-mono (47%)

tf-mono

5a

(23%)

cx-bis

5b

(11%)

5c

A range o f monoglycosides a n d bisglycosides was synthesized ( 0 ) b y v a r y i n g t h e m o l a r mass of the P T H F a g l y c o n f r o m 90 t o 2,000 g - m o l " " , t h a t i s , i n c r e a s i n g η f r o m 1 t o 28 i n structures 2 t o 4. ( P T H F 9 0 t h u s corresponds t o 1,4-butanediol a n d y i e l d s a s o l i d p o l y o l glucoside s i m i l a r t o E G G , as discussed l a t e r . ) T h e p r o d u c t s were f u l l y c h a r a c t e r i z e d , a n d t y p i c a l d a t a are presented i n T a b l e I for a m o n o g l u c o s i d e , P T H F 6 2 9 m , a n d a bisglucoside, P T H F 6 2 9 b , p r e p a r e d f r o m P T H F 6 2 9 ( M = 629 g - m o l " ) a n d glucose. C a l c u l a t e d values of m o l a r mass ( M ) a n d equivalent weight ( E , the m o l a r mass p e r O H g r o u p ) were based o n i d e a l i z e d structures 3 a n d 4 for P T H F 6 2 9 m a n d P T H F 6 2 9 b , re spectively. T h e effective f u n c t i o n a l i t i e s of b o t h p o l y o l s t o w a r d M D I were deter m i n e d as 2.05 db 0.05. G l a s s t r a n s i t i o n , p r e m e l t c r y s t a l l i z a t i o n , a n d c r y s t a l l i n e m e l t i n g t e m p e r a t u r e s , T ^ , T , a n d T , were d e t e r m i n e d b y D S C ; the a g l y c o n , P T H F 6 2 9 , h a d values o f - 9 3 , - 6 7 , a n d 16 ° C , respectively. 1

1

n

n

n

c

m

T a b l e I. C h a r a c t e r i z a t i o n D a t a of P T H F 6 2 9 m and P T H F 6 2 9 b L i q u i d Polyols Polyol

E,, E„ M„ ( g - m o l 1 ) (cale) ( g m o l ~ l ) 1

2

3

-

1

2

3

M „ M /M (calc) 2

w

T!g

3

n

T

c

(°C) (°C)

T

m

(°C)

PTHF629m

183.0

158.2

651

791

1.42

-87

-56

13

PTHF629b

154.0

119.1

663

953

1.43

-85

-45

14

A c e t y l a t i o n , acetic a n h y d r i d e . E a n d M „ c a l c u l a t e d f r o m i d e a l i z e d structures 3 a n d 4. G P C , P P O calibration. n

T h e percentage glucose conversions for P T H F 6 2 9 m a n d P T H F 6 2 9 b were 83.5 a n d 7 9 . 0 % , respectively, a n d b o t h p o l y o l s h a d less t h a n 0 . 1 % w / w r e s i d u a l


428

ADHESIVES F R O M R E N E W A B L E RESOURCES


N M P solvent a n d low a c i d contents. T h e l i q u i d p o l y o l s t h u s p r e p a r e d a n d c h a r a c t e r i z e d were t h e n a m e n a b l e for direct use i n b u l k p o l y m e r i z a t i o n s w i t h M D I to form polyurethane materials. P o l y u r e t h a n e F o r m a t i o n f r o m G l y c o s i d e s . R e l a t i v e l y s i m p l e glycosides f o r m e d f r o m c a r b o h y d r a t e s b y reactions w i t h low m o l a r mass aglycons are gen e r a l l y a m o r p h o u s solids w i t h h i g h softening p o i n t s or c r y s t a l l i n e solids w i t h h i g h m e l t i n g p o i n t s . A d d i t i o n a l l y , these glycosides are h i g h l y p o l a r a n d do not m i x r e a d i l y w i t h diisocyanates as r e q u i r e d for p o l y u r e t h a n e f o r m a t i o n i n b u l k . T h e s e features a p p l y t o E G G a n d to the m o n o g l u c o s i d e f r o m P T H F 9 0 ( 1 , 4 - b u t a n e d i o l ) p r e p a r e d i n the present w o r k . T h e P T H F 9 0 m was a s o l i d , i m m i s c i b l e w i t h M D I , a n d h a d a s i m i l a r p r o d u c t d i s t r i b u t i o n to E G G (5). In order for such glycosides t o be u t i l i z e d for p o l y u r e t h a n e f o r m a t i o n , f u r ther c h e m i c a l m o d i f i c a t i o n is r e q u i r e d t o reduce h y d r o g e n - b o n d i n g i n t e r a c t i o n s . C h a i n e x t e n s i o n , often b y a l k o x y l a t i o n at elevated t e m p e r a t u r e a n d u n d e r pres sure, is used t o o b t a i n s u i t a b l e l i q u i d p o l y o l s . O t e y (11), for e x a m p l e , has m o d i f i e d E G G i n t h i s m a n n e r i n a bulk a l k o x y l a t i o n to y i e l d p o l y o l s t h a t c o u l d t h e n be used t o f o r m p o l y u r e t h a n e foams. In the present w o r k , however, a m o r e c o n t r o l l e d o x y p r o p y l a t i o n process (12) c a r r i e d o u t i n s o l u t i o n a n d at a t m o s p h e r i c pressure was developed a n d used to convert E G G i n t o a l i q u i d p o l y o l . T h i s p o l y o l , w i t h the i d e a l i z e d s t r u c t u r e (6) i n w h i c h η = 3, h a d a n equivalent weight t o w a r d M D I of 293 g - m o l " . O n r e a c t i o n of o x y p r o p y l a t e d E G G w i t h m o l t e n M D I ( s t o i c h i o m e t r i c r a t i o , r = 1.01) at 50 ° C for 5 m i n u t e s followed b y c u r i n g at 90 ° C for 14 h o u r s , a t r a n s p a r e n t , a m b e r , glassy p o l y u r e t h a n e resin was o b t a i n e d . T h e T ^ of the resin b y D S C was 57 ° C , a n d i t s m e c h a n i c a l properties (23 ° C ) were s i m i lar t o p o l y ( m e t h y l m e t h a c r y l a t e ) w i t h a Y o u n g ' s m o d u l u s of 2.78 G P a , tensile s t r e n g t h of 46.3 M P a , u l t i m a t e e l o n g a t i o n o f 2.6%, a n d C h a r p y i m p a c t energy of 1.5 k J - m - . 1

2

CH

3

CH -£0CH CH^ÎT0H 2

2

H

OH

6


30.

Pofyurethanes from Renewable


429

Resources


However, the disadvantage of u s i n g t h i s route t o l i q u i d p o l y o l s a n d t h e n t o p o l y u r e t h a n e s is t h a t several separate stages are i n v o l v e d , a n d the c h a i n extension stage, despite the success of the s o l u t i o n a l k o x y l a t i o n m e t h o d , u t i l i z e s a n o i l - b a s e d c h e m i c a l . T h e direct conversion of glucose b y r e a c t i o n w i t h a n a g l y c o n f r o m renewable resource, as described i n the p r e v i o u s s e c t i o n , thus demonstrates the advantages a n d v i a b i l i t y of a one-stage synthesis of l i q u i d p o l y o l s . I n a d d i t i o n , the a c i d h y d r o l y s i s of cellulose derivatives w i t h in siiu r e a c t i o n i n v o l v i n g low m o l a r mass aglycons has also been s h o w n to y i e l d l i q u i d p o l y o l s s u i t a b l e for direct, b u l k p o l y u r e t h a n e f o r m a t i o n (6). T h e range of P T H F p o l y o l s synthesized b y the one-stage g l y c o s i d a t i o n p r o cess was used t o f o r m various p o l y u r e t h a n e s r a n g i n g i n properties f r o m soft elas tomers t o stiff p l a s t i c s (9). T h e p o l y u r e t h a n e s were f o r m e d b y r e a c t i o n of M D I w i t h 1) P T H F d i o l s , 2) P T H F - m o n o g l u c o s i d e s , a n d 3) P T H F - b i s g l u c o s i d e s , b o t h alone to y i e l d h o m o p o l y m e r s a n d b l e n d e d w i t h ethylene g l y c o l ( E G ) t o y i e l d segmented c o p o l y m e r s w i t h 4 8 % w / w h a r d segment content. A s e x a m ples, the f o r m a t i o n a n d properties of p o l y u r e t h a n e s are described for systems based o n the P T H F 6 2 9 p o l y o l s d e t a i l e d i n T a b l e I. E a c h p o l y o l , w i t h a n d w i t h o u t E G , was reacted at 50 ° C w i t h m o l t e n M D I (r = 1.05) for 5 m i n u t e s , cast i n t o m o l d s at a m b i e n t t e m p e r a t u r e , a n d t h e n cured at 100 ° C for 16 hours. T h e m a t e r i a l s were characterized b y D S C , d y n a m i c m e c h a n i c a l a n a l y s i s ( D M A , t o r s i o n p e n d u l u m ) , a n d tensile stress-strain measurements. C o m p a r a t i v e d a t a for the h o m o p o l y u r e t h a n e series, P U 1 t o P U 3 , a n d the c o p o l y u r e t h a n e series, c - P U l t o c - P U 3 , together w i t h t h a t for o x y p r o p y l a t e d E G G , are s h o w n i n T a ble I I .

T a b l e I I . T h e r m a l a n d M e c h a n i c a l P r o p e r t i e s of P o l y u r e t h a n e s Based on P T H F 6 2 9 D i o l s , Monoglucosides, and Bisglucosides Material

Polyol

En

1

T

g

(°C)

Ε

a

2

2

u

DSC D M A (MPa) (MPa) PUl PU2 PU3 c-PUl c-PU2 c-PU3 Resin 1

2

PTHF629 PTHF629m PTHF629b PTHF629/EG PTHF629m/EG PTHF629b/EG Oxyprop. E G G

315 -32 183 -45 154 -46 315 -15 183 29 154 36 47 57

-32 -44 -44 -5 30 50 53

1.47 0.387 0.513 609 1,900 2,940 2,780

c

2

u

(%)

8.91 1,400 0.02 1,100 0.29 430 2.2 12.70 1.2 24.10 0.4 13.30 46.30 2.6

P o l y o l equivalent weight ( a c e t y l a t i o n ) i n g - m o l " . E , a , a n d c are tensile m o d u l u s , s t r e n g t h , a n d e l o n g a t i o n . 1

u

u

H o m o p o l y u r e t h a n e s P U l t o P U 3 were t r a n s p a r e n t , pale y e l l o w / a m b e r m a terials w i t h properties t y p i c a l of soft, h i g h l y extensible r u b b e r s . Increasing


430

ADHESIVES F R O M RENEWABLE RESOURCES

the p r o p o r t i o n o f glucose u n i t s tends t o decrease a n d t o soften t h e r u b bers. H o w e v e r , the opposite trends were observed i n the c o p o l y u r e t h a n e s , w h i c h were o p a q u e , phase-separated m a t e r i a l s r a n g i n g f r o m a w h i t e , s e m i r i g i d p l a s t i c ( c - P U l ) t o a d a r k b r o w n , very stiff a n d b r i t t l e p l a s t i c ( c - P U 3 ) . A l t h o u g h t h e c o p o l y u r e t h a n e s are c l e a r l y phase separated, the increase i n Ύ a l o n g the series as the glucose content increases i n d i c a t e s i n c r e a s i n g degrees o f phase m i x i n g b e tween P T H F 6 2 9 - b a s e d soft segments a n d E G / M D I - b a s e d s e m i c r y s t a l l i n e h a r d segments. O v e r a l l , the i n c o r p o r a t i o n o f glucose u n i t s i n t o c o p o l y u r e t h a n e s s i g n i f i c a n t l y improves the stiffness a n d s t r e n g t h o f the m a t e r i a l s . Downloaded by UNIV OF PITTSBURGH on May 3, 2015 | http://pubs.acs.org Publication Date: December 31, 1989 | doi: 10.1021/bk-1989-0385.ch030

9

Polyurethanes Based o n Hydroxy-Functionalized Polymyrcenes Liquid Polyols from Myrcene: Synthesis a n d Characterization. A range o f h y d r o x y f u n c t i o n a l p r e p o l y m e r s was p r e p a r e d f r o m myrcene (7) u s i n g h y d r o g e n peroxide i n i t i a t o r i n n - b u t a n o l s o l u t i o n a t 100 ° C (3). I n the r e a c t i o n (Scheme 1), R is - C H 2 C H 2 C H = C ( C H 3 ) 2 a n d the p r i n c i p a l m i c r o s t r u c t u r a l u n i t s s h o w n were o b t a i n e d b y N M R (the 1,2 u n i t s b e i n g less t h a n 4%). A s the concen t r a t i o n o f h y d r o g e n peroxide used i n p o l y m e r i z a t i o n s was increased f r o m 0.5 t o 5.4% w / w , the equivalent weight ( a c e t y l a t i o n ) o f the p o l y m y r c e n e ( P M ) p o l y o l s decreased f r o m 3,185 t o 1,345, m o l a r mass ( M , G P C ) decreased f r o m 4,030 to 3,100, a n d the f u n c t i o n a l i t y increased f r o m 1.30 t o 2.32. T h e p o l y d i s p e r s i t y , M /M ( G P C ) , o f the P M - p o l y o l s was unaffected. Some o f the P M - p o l y o l s were t h e n used either t o f o r m h o m o p o l y u r e t h a n e a n d segmented c o p o l y u r e t h a n e elas tomers o r as reactive l i q u i d r u b b e r s t o t o u g h e n h i g h l y crosslinked p o l y u r e t h a n e resins. n

w

n

R ~ f - C H - CH=C-CH -]^

(70-80%)

R-C=CH ~-£-CH -CH-}^

(20-30%)

2

CH = CH—C = CH 2

4

3

2

1

2

2

3,4

2

2

Scheme 1 E l a s t o m e r s f r o m M y r c e n e - B a s e d P o l y o l s . A series o f p o l y u r e t h a n e s was f o r m e d u s i n g a P M p o l y o l i n a d m i x t u r e w i t h various a m o u n t s o f 1,4-butanediol ( B D ) a n d reacted w i t h M D I (4)- F o r c o m p a r i s o n , a c o r r e s p o n d i n g series o f elastomers based o n a c o m m e r c i a l l y available p o l y b u t a d i e n e ( P B ) p o l y o l ( A r c o R 4 5 - H T , C o r n e l i u s C h e m i c a l C o m p a n y ) was also p r e p a r e d . C h a r a c t e r i z a t i o n d a t a o f the P B a n d P M polyols are given i n T a b l e I I I .


30.



Resources

431

B o t h series o f p o l y u r e t h a n e s were p r e p a r e d u s i n g a p r e p o l y m e r technique i n w h i c h reactants were m i x e d at 70 ° C / 1 h o u r , cast i n t o m o l d s at 105 ° C / 2 h o u r s , a n d c u r e d at 80 ° C / 1 4 h o u r s . T h e B D / M D I h a r d segment contents r a n g e d f r o m 0 % ( t r a n s p a r e n t , colorless h o m o p o l y u r e t h a n e s ) t o 3 0 % w / w (opaque, w h i t e c o p o l y u r e t h a n e s ) . A l l elastomers were characterized u s i n g D S C , d y n a m i c m e c h a n i c a l , a n d tensile stress-strain measurements.


Table III. Characterization D a t a of P B and P M Polyols Polyol

M„,/M En M„ (g-mol 1) (g-mol 1) 1

2

-

1

2

n

2

f„

-

1,4-content (%)

Iff (°C)

PB

1,088

2,919

1.70

2.7

65

-80

PM

1,322

2,950

1.39

2.2

68

-60

A c e t y l a t i o n (acetic a n h y d r i d e ) . G P C ( P P O calibration).

T h e c o p o l y u r e t h a n e s comprise a two-phase m o r p h o l o g i c a l s t r u c t u r e i n w h i c h the continuous soft segment phase f o r m e d f r o m the P M or P B p o l y o l s c o n t a i n s a dispersed, s e m i c r y s t a l l i n e , glassy h a r d segment ( H S ) phase f o r m e d f r o m M D I / B D oligomers. T h i s two-phase m o r p h o l o g y was c o n f i r m e d b y D S C a n d D M A analyses. F i g u r e 1, for e x a m p l e , shows t y p i c a l d y n a m i c r e l a x a t i o n spec t r a for myrcene- a n d b u t a d i e n e - b a s e d h o m o p o l y u r e t h a n e s ( 0 % w / w H S ) a n d c o p o l y u r e t h a n e s ( 3 0 % w / w H S ) . O v e r a l l , three m o l e c u l a r r e l a x a t i o n s are o b served o c c u r r i n g at i n c r e a s i n g t e m p e r a t u r e s designated T ^ , T j , a n d T ^ . Τ β at a b o u t -140 ° C corresponds t o s m a l l /^-relaxations associated w i t h secondary s e g m e n t a l m o t i o n s w i t h i n the P M a n d P B c h a i n s , whose i n t e n s i t y appears t o decrease as H S content increases. T ^ a n d T ^ are, respectively, the glass t r a n s i t i o n t e m p e r a t u r e s o f the soft segment phase a n d the a m o r p h o u s regions o f the h a r d segment phase. T h e l o c a t i o n ( a n d i n t e n s i t y ) o f the largest peaks at T ^ (-35 a n d -60 ° C for m y r c e n e - a n d b u t a d i e n e - b a s e d p o l y u r e t h a n e s ) are a l m o s t i n d e p e n d e n t o f H S content a n d i n d i c a t e t h a t these are w e l l phase-separated m a terials. T h e r e l a x a t i o n at T ^ (absent i n the h o m o p o l y u r e t h a n e s , H S = 0 % w / w ) is m u c h less intense t h a n t h a t at T ^ as expected a n d is o n l y evident i n the myrcene-based c o p o l y u r e t h a n e as a b r o a d shoulder between 0 a n d 100 ° C . T h e s e observations were confirmed b y D S C d a t a (4) o b t a i n e d f r o m samples quench-cooled f r o m t e m p e r a t u r e s above 200 ° C t h a t gave T**-values o f a b o u t 80 a n d 60 ° C , respectively, for m y r c e n e - a n d b u t a d i e n e - c o p o l y u r e t h a n e s . C o r r e s p o n d i n g T ^ - v a l u e s , -57 a n d -81 ° C , f r o m D S C were a l m o s t i d e n t i c a l t o the T p - v a l u e s r e p o r t e d i n T a b l e I I I for the parent p o l y o l s a n d c o n f i r m t h a t phase


432

ADHESIVES FROM RENEWABLE RESOURCES

s e p a r a t i o n between h a r d a n d soft segments is a l m o s t complete i n these m a t e r i als. T h e m e l t i n g b e h a v i o r o f the s e m i c r y s t a l l i n e h a r d segment phase is c o m p l e x w i t h a c l e a r l y defined p r e m e l t e d c r y s t a l l i z a t i o n e x o t h e r m o c c u r r i n g at 130 ° C a n d a s h a r p c r y s t a l l i n e m e l t i n g e n d o t h e r m ( T ) at 210 ° C for the 3 0 % w / w H S myrcene-based m a t e r i a l . T h e m e l t i n g b e h a v i o r o f the b u t a d i e n e - b a s e d c o p o l y u r e t h a n e was s i m i l a r b u t less c l e a r l y defined. T h e tensile stress-strain d a t a showed the myrcene-based m a t e r i a l s t o be m u c h softer a n d weaker, b u t m o r e extensible t h a n those based o n the b u t a d i ene p o l y o l , as s h o w n i n F i g u r e 2 b y the p l o t s o f tensile properties versus H S content. Differences between the t w o series were s h o w n t o be the result of higher s o l - f r a c t i o n contents a n d lower crosslink densities of the soft segment phase i n the myrcene-based m a t e r i a l s . T h e sol f r a c t i o n o f the myrcene-based h o m o p o l y u r e t h a n e was 2 1 . 5 % w / w , w h i c h decreased t o 5 . 3 % w / w at 3 0 % H S content; the c o r r e s p o n d i n g sol-fractions for the b u t a d i e n e - b a s e d m a t e r i a l s were 3.8 a n d 0 . 7 % w / w . A n a l y s i s (4) of the s o l - f r a c t i o n e x t r a c t e d f r o m the former showed the presence o f low m o l a r mass m a t e r i a l f o r m e d f r o m oligomers w i t h h y d r o x y f u n c t i o n a l i t i e s o f less t h a n t w o c o n t a i n e d i n the o r i g i n a l m y r c e n e p o l y o l . C r o s s l i n k densities i n terms of M , the m e a n m o l a r mass o f P M or P B n e t w o r k chains between crosslinks, were d e t e r m i n e d f r o m M o o n e y - R i v l i n (13,14) a n a l y sis o f the tensile stress-strain d a t a u s i n g the s t a t i s t i c a l t h e o r y o f r u b b e r e l a s t i c i t y . E v e n a l l o w i n g for the presence o f s o l - f r a c t i o n , the value o f M (25,605 g - m o l " ) for the P M n e t w o r k was m u c h higher t h a n t h a t (3,934 g - m o l " ) for the P B a n d , w h e n c o m p a r e d w i t h the M „ - v a l u e (2,950 g - m o l " ) of the parent p o l y o l , f u r t h e r c o n f i r m e d the presence of low f u n c t i o n a l i t y species i n the o r i g i n a l myrcene prep o l y m e r . T h e results o v e r a l l , however, do show t h a t s u b s t a n t i a l i m p r o v e m e n t s i n elastomer properties are achieved b y i n c o r p o r a t i n g a h a r d segment phase, a n d t h a t p o l y o l s derived f r o m myrcene c a n be used to f o r m c o p o l y u r e t h a n e m a t e r i a l s c o m p a r a b l e t o those f o r m e d f r o m s i m i l a r o i l - b a s e d p o l y o l s . Glassy Polyurethane Resins, Rubber-Modified by Myrcene-Based P o l y o l s . I n a p r e v i o u s s t u d y (15), h i g h l y crosslinked glassy p o l y u r e t h a n e s , f o r m e d f r o m f a s t - r e a c t i n g systems (ca. 5 m i n u t e s ) , were s h o w n t o have p r o p erties equivalent t o e p o x y resins often used as adhesives. T h e e p o x y resins, however, are i n t r i n s i c a l l y b r i t t l e b u t m a y be s i g n i f i c a n t l y toughened b y i n c o r p o r a t i n g a reactive l i q u i d r u b b e r d u r i n g p o l y m e r i z a t i o n (16). D u r i n g the c o m p e t i t i v e p o l y m e r i z a t i o n s , the developing h i g h m o l a r mass r u b b e r a n d c r o s s l i n k i n g resin become i n c o m p a t i b l e a n d phase separate t o give a heterogeneous m a t e r i a l c o m p r i s i n g discrete a n d finely dispersed r u b b e r p a r t i c l e s i n a h i g h l y crosslinked resin m a t r i x . T h e l i q u i d r u b b e r s used to t o u g h e n e p o x y resins are u s u a l l y carboxyfunctional, butadiene-aerylonitrile copolymers.


m

c

1

c

1

1

I n t h i s s t u d y , the use o f a P M p o l y o l as a r u b b e r modifier for a h i g h l y crosslinked, p o l y u r e t h a n e resin ( T ^ = 150 ° C ) was assessed a g a i n i n c o m p a r ison w i t h a n o i l - b a s e d P B p o l y o l . T h e p o l y u r e t h a n e resin m a t r i x was f o r m e d from pure M D I and a polyol blend comprising a polyoxypropylene triol, L H T 2 4 0 ( U n i o n C a r b i d e ) o f equivalent weight 227.6 g - m o l " , a n d t r i m e t h y l o l p r o p a n e , 1


30.

S T A N F O R D


E T AL.

433

Resources

Polyol

HS%


butadiene

-150

-100

-50

0

50

100

Temperature

150

(C°)

F i g u r e 1. D y n a m i c r e l a x a t i o n s p e c t r a ( t o r s i o n p e n d u l u m , 1 H z ) o f p o l y u r e t h a n e s based o n p o l y m y r c e n e a n d p o l y b u t a d i e n e p o l y o l s . T y p i c a l r e l a x a t i o n p e a k s are s h o w n at the t e m p e r a t u r e s designated Ύβ, T ^ a n d T ^ .

Myrcene

polyol-

Butadiene

polvol-

.psiyurethaneç

σ CL

en c

250

Φ

200

Vo

/ /

//

D Ο

en c

I

-

fi /

Ο

ioo

10

I

50

F

I

0

150

c ο σ en c ο â

20 Hard

30

10

ι

20

ι

0

30

B l o c k C o n t e n t (w/w7„)

F i g u r e 2. V a r i a t i o n of tensile m o d u l u s Ε(-φ-), tensile s t r e n g t h σ (-0")> ^ u l t i m a t e e l o n g a t i o n e (-Q-), w i t h h a r d b l o c k content, for p o l y u r e t h a n e s based on polymyrcene and polybutadiene polyols. η

u


a n (

434


T M P , w i t h a r a t i o o f T M P : L H T 2 4 0 e q u a l t o 9:1 b y equivalents. A series of r u b b e r - m o d i f i e d m a t e r i a l s was p r e p a r e d b y a one-shot process (5,15) u s i n g i n creasing a m o u n t s o f a d d e d h y d r o x y - f u n c t i o n a l Ρ M (synthesized as described p r e v i o u s l y ) , w i t h a n equivalent weight o f 1410, m o l a r mass ( G P C ) o f 2,810 g m o l " a n d m e a n f u n c t i o n a l i t y o f 1.99. T h e P B p o l y o l used was t h a t re p o r t e d i n T a b l e I I I . A l l m a t e r i a l s f o r m e d showed p h y s i c a l characteristics t y p i c a l of a m o r p h o u s , glassy p o l y m e r s a n d were e v a l u a t e d u s i n g D S C , tensile stresss t r a i n , a n d C h a r p y i m p a c t measurements (5,15). T h e f o r m a t i o n o f a finely d i s persed, p a r t i c u l a t e r u b b e r phase w a s confirmed b y s c a n n i n g electron m i c r o s c o p y of f r a c t u r e surfaces o f various m a t e r i a l s ( F i g u r e 3 ) , a n d a h i g h degree o f phase s e p a r a t i o n between r u b b e r a n d resin m a t r i x was achieved. T h i s i m p l i e d m i n i m a l d i s s o l u t i o n o f r u b b e r i n t h e m a t r i x a n d was confirmed b y D S C d a t a t h a t showed t h e T ^ - v a l u e s (153 t o 156 ° C ) o f a l l m a t e r i a l s t o be a l m o s t i n d e p e n d e n t of r u b b e r content.


1

T h e tensile properties o f t h e P M - m o d i f i e d series are s u m m a r i z e d i n T a b l e I V together w i t h one set o f c o m p a r a t i v e d a t a for a 4 % w / w P B - m o d i f i e d m a t e r i a l . Increasing t h e r u b b e r content s i g n i f i c a n t l y improves m a t e r i a l toughness i n t e r m s o f U (the energy t o r u p t u r e o b t a i n e d f r o m t h e a r e a u n d e r a stresss t r a i n curve) due t o t h e increases i n u l t i m a t e s t r a i n (e ) a n d tensile s t r e n g t h (cr )i despite t h e g r a d u a l a n d e x p e c t e d decrease i n Y o u n g s m o d u l u s ( E ) . T h e i m p r o v e m e n t i n toughness is observed t o reach a m a x i m u m a t r u b b e r contents between 4 a n d 6 % w / w ; above 8 % w / w , t h e properties b e g i n t o deteriorate r a p i d l y w i t h respect t o t h e u n m o d i f i e d p o l y u r e t h a n e r e s i n . T h e C h a r p y i m p a c t d a t a were o b t a i n e d f r o m r a z o r - s h a r p notched b e a m s i n w h i c h the n o t c h d e p t h was s y s t e m a t i c a l l y v a r i e d (5,15). T h e d a t a were a n a l y z e d u s i n g the l i n e a r elas t i c f r a c t u r e m e c h a n i c s m e t h o d o f W i l l i a m s (17) t o give values o f G , t h e c r i t i c a l s t r a i n - e n e r g y release r a t e , or absolute fracture energy, for each m a t e r i a l . V a l ues o f G for r u b b e r - m o d i f i e d m a t e r i a l s relative t o the u n m o d i f i e d m a t r i x ( G = 1.5 k J m " " ) are p l o t t e d against r u b b e r content i n F i g u r e 4 for b o t h P M a n d P B - m o d i f i e d series. T h e results show differences i n t o u g h e n i n g b e h a v i o r between t h e P M a n d P B r u b b e r s , w i t h t h e former g i v i n g i m p r o v e d i m p a c t re sistance w i t h a m a x i m u m G - v a l u e at a b o u t 2 % w / w r u b b e r content, whereas, the p o l y b u t a d i e n e - m o d i f i e d m a t e r i a l s show a g r a d u a l a n d a l m o s t l i n e a r decrease over t h e c o m p o s i t i o n range. T h e d i s p a r a t e fracture b e h a v i o r m a y be a t t r i b u t e d to differences i n m e a n p a r t i c l e d i a m e t e r , d ( T a b l e I V ) , a n d i n t h e e l a s t i c i t y b e h a v i o r o f t h e dispersed h o m o p o l y u r e t h a n e r u b b e r s discussed i n t h e p r e v i o u s section. F i g u r e 4 also shows t h e v a r i a t i o n o f tensile toughness ( U ) w i t h r u b b e r content f r o m t h e d a t a i n T a b l e I V i l l u s t r a t i n g t h e m a x i m u m i n t o u g h e n i n g e n hancement a t r u b b e r contents between 4 a n d 6 % w / w . T h i s a p p a r e n t a n o m a l y between G a n d U d a t a is a t t r i b u t e d t o t h e different n a t u r e a n d d e f o r m a t i o n rates o f t h e i m p a c t a n d tensile tests. y

u

u

c

c

c

2

c

y

c

y

O v e r a l l , t h e r e l a t i v e l y b r i t t l e p o l y u r e t h a n e resin m a t r i x w a s t r a n s f o r m e d b y the i n c o r p o r a t i o n o f a discrete r u b b e r p a r t i c l e phase i n t o a s e m i d u c t i l e m a t e r i a l



30.


Polyurethanes from Renewable

435

Resources

F i g u r e 3. S c a n n i n g electron m i c r o g r a p h of a t y p i c a l fracture surface of a h i g h l y crosslinked p o l y u r e t h a n e resin c o n t a i n i n g 8 % w / w of dispersed

polymyrcene-

based r u b b e r p a r t i c l e s .


436


w i t h i m p r o v e d f r a c t u r e properties, a n d these studies show t h a t P M p o l y o l s are effective as r u b b e r - m o d i f i e r s for b r i t t l e resins. T a b l e I V . Tensile P r o p e r t i e s of Polymyrcene-Modified, Polyurethane Resins Rubber w / w (%)


Matrix PM PM PM PM PM PB

0 2 4 6 8 10 4

d ( H 1

Ε σ„ e ( G P a ) ( M P a ) (%) u

Uy (MJrrr

-

3.00 2.71

79.4

4.8

1.92

79.1

5.6

2.22

81.4 77.5

7.1 7.8

3.08 3.39

5.8 8.1 11.8

2.76 2.53 2.34 1.90 2.73

67.0 57.1 82.2

5.6 5.7 8.3

1.90 1.80 4.90

2.9 3.2 5.2

d = m e a n d i a m e t e r of r u b b e r p a r t i c l e s .

Polyurethanes from Furan-Based Diisocyanates Synthesis a n d Characterization of Furfuryl Diisocyanates ( F D I ) . Fu r a n a n d i t s derivatives are o b t a i n a b l e f r o m m a i z e a n d oat husks a n d , as s u c h , are a t t r a c t i v e renewable resource m a t e r i a l s for the synthesis of m o n o m e r s a n d d e r i v e d p o l y m e r s . F u r f u r y l a m i n e (8) i n p a r t i c u l a r is r e a d i l y a v a i l a b l e a n d was chosen for the synthesis of a series of diisocyanates h a v i n g structures analogous t o the o i l - b a s e d M D I used extensively for p o l y u r e t h a n e p r o d u c t i o n . N o v e l f u r f u r y l d i i s o c y a n a t e s of general s t r u c t u r e 9, i n w h i c h R i , R 2 are either Η, Η or CH3, CH3 or H , CH3, (Scheme 2) were prepared u s i n g a four-stage synthesis route r e p o r t e d i n d e t a i l elsewhere ( 7 ) .

CH NH 2

2

R, 8

R

2

9

Scheme 2 E s s e n t i a l l y , the a m i n e group o n 8 h a d to be p r o t e c t e d b y conversion (i) t o the f o r m a m i d e before the c o u p l i n g r e a c t i o n ( i i ) , i n v o l v i n g either f o r m a l d e h y d e , ace t a l d e h y d e , or acetone t o generate the d i f u r y l - a l k a n e nucleus, c o u l d be effected.



30.



I Ο

ι 2

ι ι ι 4 6 8 Rubber content (%w/w)

Resources

437

ι10

F i g u r e 4. V a r i a t i o n of relative fracture energy, G / G ™ , a n d tensile toughness, U , w i t h r u b b e r content for r u b b e r - m o d i f i e d , h i g h l y crosslinked p o l y u r e t h a n e resins. G /G™ (-φ- p o l y m y r c e n e , - • - p o l y b u t a d i e n e ) ; U ( - A - p o l y m y r c e n e ) . c

y

c

y


ADHESIVES FROM RENEWABLE RESOURCES

438

A f t e r c o u p l i n g , the d i f o r m a m i d e was h y d r o l y z e d (iii) u n d e r a l k a l i n e c o n d i t i o n s t o give the d i a m i n e . F i n a l l y , the d i a m i n e was converted (iv) v i a the h y d r o c h l o ride t o the d i i s o c y a n a t e by p h o s g e n a t i o n . T h e three diisocyanates, designated F D I - a ( R i , R = H ) ; F D I - b ( R i = H , R = C H ) ; and F D I - c ( R R = CH ), were p u r i f i e d b y v a c u u m d i s t i l l a t i o n w i t h y i e l d s between 60 a n d 7 0 % a n d were f u l l y c h a r a c t e r i z e d b y I R , N M R , a n d c o m b u s t i o n a n a l y s i s together w i t h the p r e p a r a t i o n of s u i t a b l e derivatives ( 7 ) . T h e F D I c o m p o u n d s i n the p u r e state were s t a b l e l i q u i d s d o w n to at least 0 ° C a n d showed l i t t l e tendency t o f o r m c r y s t a l l i n e d i m e r or other i m p u r i t i e s o n storage. T h e diisocyanates have m o l a r masses c o m p a r a b l e t o p u r e M D I a n d possess low viscosities a n d v o l a t i l i t i e s (b.p. « 125 ° C at 0.02 m m H g ) , m a k i n g t h e m h i g h l y a t t r a c t i v e for b u l k p o l y u r e t h a n e formation.


2

2

3

l f

2

3

F u r t h e r c h a r a c t e r i z a t i o n o f the F D I c o m p o u n d s , i n c o m p a r i s o n w i t h pure M D I , was o b t a i n e d f r o m u r e t h a n e - f o r m i n g k i n e t i c s d a t a ( 7 ) , f o l l o w i n g the m e t h o d o f B u r k u s a n d E c k e r t (18). D i i s o c y a n a t e s were reacted w i t h n - b u t a n o l i n toluene s o l u t i o n s at 40 ± 0.05 ° C u s i n g either t r i e t h y l a m i n e ( T E A ) or t r i e t h y l e n e d i a m i n e ( T E D ) as c a t a l y s t . T h e d a t a were a n a l y z e d u s i n g second-order k i n e t i c s expressions i n order t o evaluate the apparent r a t e constants, k . Values of k for T E D - c a t a l y z e d reactions for the F D I c o m p o u n d s r a n g e d f r o m 0.112 t o 0.087 m o l " m i n , c o m p a r e d w i t h 1.5 m o l " " m i n " " for M D I , w i t h the r e a c t i v i t y order decreasing a l o n g the series a p p

1

- 1

1

app

1

M D I > FDI-a > FDI-b > FDI-c A l t h o u g h less reactive t h a n M D I , the f u r a n - b a s e d diisocyanates were s h o w n t o behave as b e n z y l i c - t y p e c o m p o u n d s w i t h r e a c t i v i t i e s i n t e r m e d i a t e between those o f a r y l a n d a l k y l diisocyanates. Formation of Polyurethanes from Furfuryl Diisocyanate, F D I - a . C o m p a r a t i v e studies were c a r r i e d o u t o n h o m o p o l y u r e t h a n e s a n d c o p o l y u r e t h a n e s f o r m e d f r o m F D I - a ( F ) a n d M D I ( M ) reacted w i t h , respectively, P T H F d i o l ( P T H F , M = 1,010 g - m o l - ) a n d blends o f P T H F a n d 1,4-butanediol ( B D ) . F D I - a was chosen as i t was the m o s t reactive of the f u r a n - b a s e d d i i s o c y a n a t e s , a n d because o f the m e t h y l e n e nuclear b r i d g i n g g r o u p , i t b o r e the closest s t r u c t u r a l resemblance t o M D I . A n e n d - c a p p i n g process ( 7 ) was used t o prepare c o p o l y u r e t h a n e s w i t h i n c r e a s i n g h a r d segment contents between 0 a n d 5 0 % w / w . T h e o v e r a l l s t o i c h i o m e t r i c r a t i o o f N C O to O H groups was 1.05. F o r M D I - b a s e d p o l y m e r s , a n e n d - c a p p i n g t i m e o f 15 m i n u t e s was used, b u t w i t h F D I - a , longer t i m e s o f 40 a n d 120 m i n u t e s were r e q u i r e d t o p r o d u c e s a t i s f a c t o r y m a t e r i a l s . T h e p o l y u r e t h a n e m a t e r i a l s p r o d u c e d were characterized b y D S C a n d D M A measurements. T h e t r a n s i t i o n b e h a v i o r f r o m D S C studies, s u m m a r i z e d i n T a b l e V , is c o n sistent w i t h the two-phase s t r u c t u r e expected. T h e l o w - t e m p e r a t u r e glasst r a n s i t i o n , T ^ , is associated w i t h the continuous ( P T H F ) soft segment phase, whereas, the t r a n s i t i o n s at T ^ a n d T are associated w i t h the a m o r p h o u s a n d n

1

m


30.

Polyurethanes


from Renewable

Resources

439

c r y s t a l l i n e regions, respectively, o f the dispersed h a r d segment phase, f o r m e d f r o m either F D I - a / B D or M D I / B D oligomers. T a b l e V also shows t r a n s i t i o n d a t a for h o m o p o l y u r e t h a n e s M - P T H F a n d F - P T H F (isolated soft segment phases, t r a n s p a r e n t r u b b e r s ) , a n d o l i g o m e r i c h o m o p o l y u r e t h a n e s M - B D a n d F - B D (isolated h a r d segment phases, w h i t i s h glassy p o w d e r s ) . T h e lower T ^ values for F - P T H F a n d F 5 0 - B a n d the presence o f T f for F 5 0 - B (absent i n M 5 0 ) suggest the F D I - b a s e d m a t e r i a l s t o be m o r e phase separated t h a n those based o n M D I . A l s o , the lower T - v a l u e s of the c r y s t a l l i n e F - B D h a r d segments reflect the m o r e flexible n a t u r e of F D I - a i n w h i c h the N C O groups are a t t a c h e d t o the f u r a n r i n g s v i a m e t h y l e n e groups ( 9 ) , whereas, i n M D I , the N C O g r o u p s are a t t a c h e d d i r e c t l y t o the benzene r i n g s .


m

T a b l e V . T r a n s i t i o n B e h a v i o r ( D S C ) of P o l y u r e t h a n e s Derived from M D I (M) and F D I (F) Polymer

H a r d Segment (%

M-PTHF F-PTHF M50 F50-A F50-B M-BD F-BD x

w/w) 0 0 50 50 50 100 100

2

2

N o t observed.

9

T£

(°C) -55 -67 -61

CO

i)

0) 31 84-89 28

1

-64

-

-

T

m

CO

-

-

C)

181 112-121 118-145 193-209 156

3

3

A a n d Β refer t o 4 0 - a n d 1 2 0 - m i n u t e , e n d capping times. Q u e n c h - c o o l e d , a m o r p h o u s samples.

2

3

T h e d y n a m i c m e c h a n i c a l results c o n f i r m the two-phase m o r p h o l o g y present i n b o t h sets o f c o p o l y u r e t h a n e s . F i g u r e 5 shows t y p i c a l shear m o d u l u s ( G ) versus t e m p e r a t u r e b e h a v i o r for F D I - a ( F ) a n d M D I ( M ) based m a t e r i a l s c o n t a i n i n g 5 0 % w / w H S . M 5 0 , a n opaque, s e m i r i g i d elastomer at r o o m t e m p e r a t u r e ( G = 128 M P a ) , showed a n i n i t i a l d r o p i n m o d u l u s at T ^ a r o u n d -40 ° C f o l lowed b y a p l a t e a u region where the m o d u l u s decreases g r a d u a l l y u n t i l the onset of h a r d segment m e l t i n g at a b o u t 180 ° C . T h e f u r a n - b a s e d m a t e r i a l s , however, showed b r o a d soft-segment t r a n s i t i o n s r a n g i n g f r o m -60 t o 40 ° C , a n d t h e i r higher t e m p e r a t u r e b e h a v i o r was s t r o n g l y dependent o n the e n d - c a p p i n g t i m e used d u r i n g c o p o l y u r e t h a n e p r e p a r a t i o n . T h u s , F 5 0 - A , a t r a n s p a r e n t r u b b e r at r o o m t e m p e r a t u r e ( G = 48 M P a ) , was m u c h less phase separated t h a n F 5 0 - B , w h i c h is a t r a n s l u c e n t , s e m i r i g i d elastomer ( G = 78 M P a ) . Hence, the longer e n d - c a p p i n g t i m e e n a b l e d a higher m o l a r mass soft-segment phase t o de velop i n F 5 0 - B , r e s u l t i n g i n a b e t t e r phase-separated m a t e r i a l w i t h properties 1

1

1

1



440


Temperature (C°)

F i g u r e 5. D y n a m i c shear m o d u l u s - t e m p e r a t u r e b e h a v i o r ( t o r s i o n p e n d u l u m , 1 H z ) o f 5 0 % w / w H S c o p o l y u r e t h a n e s based o n diisocyanates F D I - a ( F ) a n d M D I ( M ) . Soft segment glass t r a n s i t i o n a n d hard-segment m e l t i n g are i n the t e m p e r a t u r e regions i n d i c a t e d , respectively, b y and T . m


30.


Polyurethanes from Renewable

Resources

441

closer t o those o f M 5 0 . F i n a l l y , despite t h e lower c r y s t a l l i n e m e l t i n g b e h a v i o r of F 5 0 - A ( T « 100 ° C ) a n d F 5 0 - B ( T « 120 ° C ) s h o w n i n F i g u r e 5, t h e m o d u l u s p l a t e a u above 150 ° C is i n d i c a t i v e o f stable crosslinks t h a t render the f u r a n - b a s e d c o p o l y u r e t h a n e s m o r e d i m e n s i o n a l l y stable c o m p a r e d t o M D I - b a s e d m a t e r i a l s a t t e m p e r a t u r e s a r o u n d 200 ° C . m

m

Conclusions


T h e s e studies have s h o w n t h a t : (1) G l u c o s e c a n b e reacted w i t h a n a g l y c o n f r o m a renewable resource i n a one-stage synthesis t o y i e l d l i q u i d p o l y o l s s u i t a b l e for direct b u l k p o l y u r e t h a n e formation; (2) H y d r o x y - f u n c t i o n a l i z e d l i q u i d r u b b e r s c a n b e p r e p a r e d f r o m myrcene t h a t are s u i t a b l e for p o l y u r e t h a n e elastomer f o r m a t i o n , a n d as r u b b e r t o u g h e n i n g agents; (3) P u r e l i q u i d diisocyanates c a n be synthesized f r o m the renewable resource f u r f u r a l , a n d used w i t h l o w a n d h i g h m o l a r mass diols also d e r i v e d f r o m f u r f u r a l to form block copolyurethanes. T h e o v e r a l l p h y s i c a l a n d m e c h a n i c a l properties o f the v a r i o u s m a t e r i a l s p r e p a r e d u t i l i z i n g renewable resource diisocyanates a n d p o l y o l s have been s h o w n to b e c o m p a r a b l e t o those o f m a t e r i a l s derived f r o m o i l - b a s e d c h e m i c a l s . A cknowledgment s T h e a u t h o r s w i s h t o t h a n k t h e W o l f s o n F o u n d a t i o n for a g r a n t t h a t s u p p o r t e d t h i s research p r o g r a m . Literature Cited 1. Frisch, K. C. Plast. Rubb. Int. 1983, 8, 1. 2. See for example Hepburn, C. Polyurethane Elastomers; Applied Science: London, 1982. 3. Cawse, J. L.; Stanford, J. L.; Still, R. H. J. Appl. Polym. Sci. 1987, 33, 2217. 4. Cawse, J. L.; Stanford, J. L.; Still, R. H. J. Appl. Polym. Sci. 1987, 33, 2231. 5. Cawse, J. L.; Stanford, J. L.; Still, R. H. Polymer 1987, 28(3), 368. 6. Cawse, J. L.; Donnelly, M . J.; Stanford, J. L.; Still, R. H. Patent Application PCT GB85 00388. 7. Cawse, J. L.; Stanford, J. L.; Still, R. H. Makromol. Chem. 1984, 185, 697. 8. Cawse, J. L.; Stanford, J. L.; Still, R. H. Makromol. Chem. 1984, 185, 709. 9. Donnelly, M . J. Ph.D. Thesis, Manchester University, Manchester, 1984. 10. Otey, F. H. Ind. Eng. Chem. Prod. Res. Dev. 1965, 4(4), 228. 11. Otey, F. H.; Zagoren, B. L.; Mehltretter, C. L. Ind. Eng. Chem. Prod. Res. Dev. 1963, 2(4), 256.


442


12. Cawse, J. L.; Stanford, J. L.; Still, R. H. Patent Application PCT GB85 00500. 13. Mooney, M . J. Appl. Phys. 1948, 19, 434. 14. Rivlin, R. S. Phil. Trans. Roy. Soc. London 1948, A241, 379. 15. Cawse, J. L.; Stanford, J. L. Polymer 1987, 28(3), 356. 16. Kinloch, A. J.; Young, R. J. Fracture Behaviour of Polymers; Applied Science: London, 1983; Chapter 12. 17. Plati, E.; Williams, J. G. J. Polym. Eng. Sci. 1975, 15, 470. 18. Burkus, J.; Eckert, C. F. J. Amer. Chem. Soc. 1958, 80, 5948.


RECEIVED May 27, 1988


Adhesives from Renewable Resources - American Chemical Society

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