Sound and Vibration Damping with Polymers - American Chemical

Chapter 25

Dynamic Mechanical Response of In Situ Polyurethane—Poly(methyl methacrylate) Interpenetrating Polymer Networks

Downloaded by UNIV MASSACHUSETTS AMHERST on September 9, 2012 | http://pubs.acs.org Publication Date: May 1, 1990 | doi: 10.1021/bk-1990-0424.ch025

Influence of Kinetics of Formation M. T. Tabka, J. M. Widmaier, and G. C. Meyer Institut Charles Sadron (CRM-EAHP), Ecole d'Application des Hauts Polymères, 4, rue Boussingault, 67000 Strasbourg, France A rather new synthesis principle yielding the so– called in situ simultaneous interpenetrating polymer networks (IPNs) has been elaborated: by selecting an adequate synthesis parameter, the kinetics of formation of both networks, followed by Fourier transform infra-red spectroscopy, interfer more or less, and a not negligeable change in the final structure results without having to change the composition. Thus, in a series of polyurethane/poly(methyl methacrylate) IPNs, the damping behavior differs according to the amount of the polyurethane catalyst added, showing either two transitions, or, more interestingly, one broad transition extending over a large temperature scale. The morphology o f multicomponent systems i s p r i m a r i l y r e l a t e d t o t h e m i s c i b i l i t y between polymers and t o t h e type o f b l e n d i n g . U s u a l l y , mechanical blends e x h i b i t large phase domains o f v a r i o u s t y p e s . S m a l l e r , and w e l l - d e f i n e d m o r p h o l o g i e s a r e o b t a i n e d by f o r m i n g b l o c k and g r a f t c o p o l y m e r s . I n t e r p e n e t r a t i n g polymer networks (IPNs), i n which t h e polymers are held t o g e t h e r i n t h e i r network form by permanent entanglements, have shown t o l e a d t o s m a l l e r domains than o t h e r polymer m i x t u r e s ( 1 ) . I n such m a t e r i a l s , any f u r t h e r e v o l u t i o n of t h e morphology i s impeded once both c o n s t i t u e n t s have been c r o s s l i n k e d , and t h e r e f o r e no subsequent change i n p r o p e r t i e s has t o be f e a r e d . In our l a b o r a t o r y , much a t t e n t i o n has been d e v o t e d t o t h e investigation o f in situ sequential polyurethane/poly(methyl m e t h a c r y l a t e ) i n t e r p e n e t r a t i n g polymer networks (SEQ PUR/PAc IPNs) (2-5) i n which t h e e l a s t o m e r i c p o l y u r e t h a n e network i s c o m p l e t e l y formed i n t h e p r e s e n c e o f t h e m e t h a c r y l i c monomers b e f o r e t h e o n s e t o f t h e r a d i c a l c o p o l y m e r i z a t i o n which l e a d s t o t h e second network. To each p o l y m e r i z a t i o n p r o c e s s c o r r e s p o n d s a t y p i c a l k i n e t i c s , which however i s n o t c o m p l e t e l y independent from each o t h e r ( 6 - 8 ) . The r e s u l t s o b t a i n e d w i t h such SEQ IPNs show t h a t t h e p r o p e r t i e s do i n 0097-6156/90/0424-O445$06.00/0 © 1990 American Chemical Society

In Sound and Vibration Damping with Polymers; Corsaro, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.


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SOUND AND VIBRATION DAMPING WITH POLYMERS

f a c t n o t change s i g n i f i c a n t l y when the v a r i o u s s y n t h e s i s parameters are changed. D i f f e r e n t p r o p e r t i e s can be o b t a i n e d o n l y by v a r y i n g the c o m p o s i t i o n o f the components. A more s e l e c t i v e approach c o n s i s t s i n t r y i n g to i n f l u e n c e the k i n e t i c s o f f o r m a t i o n o f a t l e a s t one network; i n t h i s c a s e , the two networks a r e formed more o r l e s s s i m u l t a n e o u s l y , and the r e s u l t i n g morphology and p r o p e r t i e s can be e x p e c t e d to v a r y t o some e x t e n t without changing the overall composition. The same system as p r e v i o u s l y s t u d i e d , PUR/PAc, has been u t i l i z e d i n o r d e r t o p r e p a r e a series of in situ simultaneous IPNs (SIM IPNs), by acting essentially on two s y n t h e s i s parameters: the temperature o f the r e a c t i o n medium and the amount o f the p o l y u r e t h a n e c a t a l y s t . Note t h a t the term s i m u l t a n e o u s r e f e r s t o the o n s e t o f the r e a c t i o n s and not n e c e s s a r i l y to the p r o c e s s . The k i n e t i c s o f the two r e a c t i o n s are f o l l o w e d by F o u r i e r t r a n s f o r m i n f r a - r e d (FTIR) s p e c t r o s c o p y as described earlier (7,8). In this contribution, the dynamic mechanical p r o p e r t i e s , e s p e c i a l l y the l o s s tangent b e h a v i o r , have been examined w i t h the aim t o c o r r e l a t e the p r e c e d i n g s y n t h e s i s parameters to the shape and temperature o f the t r a n s i t i o n s o f the IPNs. E X P E R I M E N T A L MATERIALS PLURIISOCYANATE. Desmodur L75, p r o v i d e d by Bayer AG, i s a 1,1,1t r i m e t h y l o l p r o p a n e / t o l u e n e d i i s o c y a n a t e adduct c o n t a i n i n g 25% e t h y l a c e t a t e by w e i g h t . D e n s i t y : 1.17 g/ml; NCO e q u i v a l e n t weight p e r kg: 3.06 (by s t a n d a r d t i t r a t i o n w i t h d i - n - b u t y l a m i n e ) . Desmodur L75 was u s e d as r e c e i v e d . G e l p e r m e a t i o n chromatography has shown t h a t this product c o n t a i n s i n f a c t four s p e c i e s o f d i f f e r e n t molecular weights and f u n c t i o n a l i t i e s ( 9 ) . POLY(OXYPROPYLENE GLYCOL). The diol used i n t h i s work was p o l y ( o x y p r o p y l e n e g l y c o l ) (POPG) s u p p l i e d by A r c o C h e m i c a l Co. under the t r a d e name A r c o l 1020. I t has a number-average m o l e c u l a r w e i g h t of 1890 g/mol w i t h a p o l y d i s p e r s i t y index o f 1.5. Hydroxyl content: 1.06 mol/kg; d e n s i t y : 1.0 g/ml; v i s c o s i t y a t 25°C: 370 cP. Before use, POPG was d r i e d a t l e a s t f o r t h r e e weeks over m o l e c u l a r sieves, and the water c o n t e n t checked by a K a r l F i s c h e r t i t r a t i o n . CATALYST. Stannous o c t o a t e (OcSn) from G o l d s c h m i d t was s t o r e d under nitrogen at low temperature and was used without further p u r i f i c a t i o n . T i n c o n t e n t : 29.1% by weight; d e n s i t y : 1.25g/ml. METHACRYLIC SYSTEM. M e t h y l methacrylate purchased from Merck and 1,1,1-trimethylol propane trimethacrylate (TRIM) supplied by Degussa, u s e d as c r o s s l i n k e r , were d r i e d over m o l e c u l a r sieves but n o t o t h e r w i s e p u r i f i e d , so t h a t they s t i l l c o n t a i n e d 15 ppm and 100 ppm m e t h y l e t h y l h y d r o q u i n o n e , r e s p e c t i v e l y . The i n i t i a t o r o f radical p o l y m e r i z a t i o n was a z o b i s i s o b u t y r o n i t r i l e (AIBN).


25.

TABKAETAL.

Kinetics of Formation

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SYNTHESIS The synthesis o f polyurethane/poly(methyl m e t h a c r y l a t e ) IPNs was p e r f o r m e d by the f o l l o w i n g g e n e r a l p r o c e d u r e (2.) . The r e a g e n t s were mixed together and s t i r r e d under d r y n i t r o g e n , stannous o c t o a t e b e i n g added l a s t , as i t s c a t a l y t i c a c t i o n begins immediately upon c o n t a c t w i t h the p o l y u r e t h a n e p r e c u r s o r s . The end o f m i x i n g was s e t as the o r i g i n o f the r e a c t i o n t i m e s . The m i x t u r e was p o u r e d i n t o a g l a s s mold and a l l o w e d t o r e a c t . The IPNs were a n n e a l e d a t 75°C f o r one night and f u r t h e r cured a t 120°C f o r 3 h o u r s . For a g i v e n composition, the following values have been taken : [NCO] / [OH] = 1 . 0 7 , TRIM = 5 wt-% and AIBN = 1 wt-%. KINETICS The k i n e t i c s o f IPN f o r m a t i o n were f o l l o w e d by F o u r i e r t r a n s f o r m i n f r a - r e d (FTIR) s p e c t r o s c o p y . For FTIR e x p e r i m e n t s , t h e m i x t u r e was i n j e c t e d i n a c e l l formed by two NaCl windows s e p a r a t e d by a 20 /zm thick gasket. The s p e c t r a were obtained on a N i c o l e t 60SX spectrophotometer equipped with a Specac h e a t i n g chamber with a u t o m a t i c temperature c o n t r o l l e r . R e a c t i o n c o n v e r s i o n was c a l c u l a t e d from the change o f the n o r m a l i z e d absorbance o f the i s o c y a n a t e peak a t 2275 cm" and C=C peak a t 1639 cm" . 1

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DYNAMIC MECHANICAL MEASUREMENTS Dynamic m e c h a n i c a l measurements were p e r f o r m e d w i t h a Rheometrics model RMS 7200 m e c h a n i c a l spectrometer a t a f i x e d frequency o f 1 r a d / s through a temperature range from -100°C t o 150°C under d r y nitrogen. The t e s t specimens were p r e p a r e d i n r e c t a n g u l a r shape about 60 mm i n l e n g t h , 11 mm i n w i d t h , and 4 mm i n t h i c k n e s s . The a p p l i e d s t r a i n was 1%. R E S U L T S

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F i g u r e 1 shows c o n v e r s i o n v e r s u s time c u r v e s i n the case o f an in situ sequential s y n t h e s i s . Due t o differing s y n t h e s i s modes ( p o l y a d d i t i o n and r a d i c a l c o p o l y m e r i z a t i o n ) , these curves are not s u p e r p o s a b l e , and may t h e r e f o r e o n l y c r o s s each o t h e r when moved a l o n g the temperature s c a l e o r when t h e i r s l o p e s change. By s e t t i n g the temperature o f the r e a c t i o n medium a t 60°C from the beginning o f t h e IPN f o r m a t i o n , t h e PUR s y n t h e s i s i s a c c e l e r a t e d , and t h a t o f the m e t h a c r y l i c system b e g i n s a f t e r the u s u a l i n h i b i t i o n p e r i o d . The c o m p e t i t i o n between the two p r o c e s s e s can s t i l l f a v o u r the complete f o r m a t i o n o f PUR b e f o r e appreciable r a d i c a l c o p o l y m e r i s a t i o n may have taken p l a c e , though the k i n e t i c c u r v e s may change o r even c r o s s . For t h i s r e a s o n , a second f a c t o r , the c o n t e n t o f PUR c a t a l y s t , i s v a r i e d too : w i t h l e s s stannous o c t o a t e , the f o r m a t i o n o f the f i r s t network i s more o r l e s s d e l a y e d , even a t 60°C, and c o u n t e r b a l a n c e s t o some e x t e n t the e f f e c t o f temperature. I n such a c a s e , the c o n v e r s i o n o f the m e t h a c r y l i c phase may p r o c e e d f u r t h e r b e f o r e h i g h e r o r even p o s t - g e l c o n v e r s i o n s are r e a c h e d f o r p o l y u r e t h a n e . Thus, IPNs i n which b o t h networks have been formed more o r l e s s simultaneously, a r e o b t a i n e d by t h i s procedure

American Chemical Society Library 1155 16th St. N. W.

In Sound and Washington, Vibration Damping 0.with C. Polymers; 20036 Corsaro, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

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For a s e r i e s o f 25/75 SIM PUR/PAc IPNs, t h e OcSn c o n t e n t was v a r i e d from 1.0 t o 0.1 wt-%; t h e f i r s t amount i s a l s o u s e d i n t h e in situ s e q u e n t i a l IPNs (2) and a l l o w s t h e r e f o r e comparison between t h e both types o f m a t e r i a l s . Conversion c u r v e s o b t a i n e d by FTIR a r e given i n Figures 2 t o 4. Curves c o r r e s p o n d i n g t o t h e f o r m a t i o n o f

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F i g u r e 2. C o n v e r s i o n p r o f i l e s f o r PUR f o r m a t i o n (open symbols) a n d PAc f o r m a t i o n ( f u l l symbols) i n 25/75 SIM PUR/PAc IPNs as a f u n c t i o n of c a t a l y s t c o n c e n t r a t i o n : ( a ) : 1.0% ; ( b ) : 0.5% ; ( c ) : 0.25% ; (d) : 0.1% .



25.

TABKAETAL.

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the PUR phase a r e d i s p l a y e d i n F i g u r e 3 and t h a t o f the PAc phase i n F i g u r e 4 : f o r b o t h components, though m a i n l y f o r polyurethane, they d i f f e r l a r g e l y w i t h the c a t a l y s t c o n t e n t , i n d i c a t i n g t h a t the two p a r a m e t e r s chosen i n f l u e n c e a d e q u a t e l y the k i n e t i c s . Arrows on the p o l y u r e t h a n e c o n v e r s i o n c u r v e s show the a c t u a l c r o s s i n g by the c o r r e s p o n d i n g m e t h a c r y l i c curves. For 1% OcSn, PUR i s completely formed b e f o r e c r o s s i n g o c c u r s , and o n l y about 10% a c r y l i c doublebonds have been converted at i t s gelation p o i n t ( i . e . 70% NCO c o n v e r s i o n ) . Such an e x p e r i m e n t a l s i t u a t i o n i s i n f a c t c l o s e t o t h a t realized i n an in situ s e q u e n t i a l IPN (6) , though a slight difference i n methacrylic conversion exists.

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F i g u r e 3. Conversion profile f o r PUR formation i n 25/75 SIM PUR/PAc IPNs as a function of catalyst concentration: (•) : 1.0%; (•): 0.5%; (•): 0.35%; ( A ) : 0.25%; (•): 0.1%. Arrows i n d i c a t e l o c a t i o n o f c r o s s i n g w i t h the c o r r e s p o n d i n g PAc c o n v e r s i o n c u r v e . As the c a t a l y s t c o n t e n t decreases, c r o s s i n g occurs at earlier NCO c o n v e r s i o n . Above 0.5% OcSn, p o l y u r e t h a n e s t i l l r e a c h e s g e l a t i o n b e f o r e c r o s s i n g ; below t h a t c o n t e n t , i t s c o n v e r s i o n i s uncomplete even a f t e r 150 minutes, a r a t h e r l o n g time as compared to the usual 30 minutes r e q u i r e d to r e a c h g e l a t i o n . F o r 0.1% OcSn, the c o n v e r s i o n i s s t o p p e d a t around o n l y 30% o f the a v a i l a b l e NCO f u n c t i o n s . I f a d e c r e a s e i n c o n v e r s i o n r a t e i s normal w i t h d e c r e a s i n g the amount of c a t a l y s t , more d e t a i l e d s t u d i e s have shown t h a t a t l e a s t two other f a c t o r s are i n v o l v e d i n b o t h slow down and low l e v e l o f f i n a l NCO d i s a p p e a r e n c e . F i r s t , an i n t e r a c t i o n e x i s t s between OcSn and AIBN, which forms an 1:1 complex (Tabka, M. T.; Widmaier, J . M.; Meyer, G. C., to be p u b l i s h e d ) , and the part o f OcSn i m p l i e d i n t h i s complex i s no more a v a i l a b l e as c a t a l y s t . On the o t h e r hand, the p a r t i a l l y c o n c o m i t a n t development o f a r i g i d m e t h a c r y l i c phase, may p e r t u r b the f o r m a t i o n o f p o l y u r e t h a n e .



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f o r PAc f o r m a t i o n i n 25/75 SIM catalyst concentration: (•): 1.0%;

( T ) : 0.35%; ( A ) : 0.25%; (•): 0.1%.

Once t h e s y n t h e s i s i s completed, t h e IPNs a r e a n n e a l e d . I n t h e materials with i n c o m p l e t e NCO c o n v e r s i o n , t h e u n r e a c t e d f u n c t i o n s disappear within a week a t 60°C, even i n t h e absence o f water. However, t h e p a r a l l e l o c c u r r e n c e o f new u r e t h a n e , u r e a . . , groups could n o t be d e t e c t e d a c c u r a t e l y by FTIR s p e c t r o s c o p y o r o t h e r methods. I t remains t h a t these IPNs c o n t a i n no more r e a c t i v e groups when u t i l i z e d f o r t e s t i n g . F i g u r e 4 shows t h a t t h e f o r m a t i o n o f the m e t h a c r y l i c network i s also somewhat i n f l u e n c e d by t h e amount o f OcSn, though a 100% c o n v e r s i o n i s always r e a c h e d a f t e r about two h o u r s . T h i s o b s e r v a t i o n may be r e l a t e d t o t h e v i s c o s i t y o f t h e r e a c t i o n medium : i t s increase accelerates the r a d i c a l copolymerization. The a l r e a d y mentioned OcSn-AIBN i n t e r a c t i o n has a s i m i l a r e f f e c t , by i n d u c i n g a f a s t e r d e c o m p o s i t i o n o f AIBN i n t o r a d i c a l s (Tabka, M. T.; Widmaier, J . M.; Meyer, G. C , t o be p u b l i s h e d ) . The above r e s u l t s demonstrate t h a t a r a t h e r minor change i n some parameters i s a b l e t o i n f l u e n c e l a r g e l y t h e k i n e t i c s ; t h i s i n turn signifies that materials of various morphologies may be obtained a t constant IPN c o m p o s i t i o n ; whether this change i n morphology w i l l induce appreciable differences i n the f i n a l properties, has s t i l l t o be demonstrated, and depends on t h e polymers i n v o l v e d and t h e p r o p e r t y wanted. For t h i s purpose, t h e dynamic m e c h a n i c a l p r o p e r t i e s o f a s e r i e s o f 25/75 in situ SIM IPNs have been i n v e s t i g a t e d ( F i g u r e 5 ) . W i t h 1% OcSn, t h e t a n 8 v s temperature c u r v e shows a c l a s s i c a l shape, as f o r in situ SEQ IPNs and c o r r o b o r a t e s the k i n e t i c r e s u l t s : two s e p a r a t e d t r a n s i t i o n s , broadened and damped, e x i s t (10). The lower transition corresponding to the polyurethane phase, i s shifted


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temperature ( C) F i g u r e 5. Loss tangent versus temperature c u r v e s f o r 25/75 SIM PUR/PAC IPNs as a f u n c t i o n o f c a t a l y s t c o n c e n t r a t i o n : (•) : 1.0%,

(*): 0.75%, (•): 0.5%; (•): 0.35%; ( A ) : 0.25%; (•) : 0.1%.

towards a h i g h e r temperature; i n some c a s e s , i t o v e r l a p s w i t h t h e ft peak o f PMMA i n t h e s e systems, so t h a t t h e i r r e s p e c t i v e c o n t r i b u t i o n cannot be p r o p e r l y s e p a r a t e d . The upper t r a n s i t i o n i s lower t h a n f o r the n e a t m e t h a c r y l i c network, and i n d i c a t e s some m i x i n g with the elastomeric component. A t lower catalyst contents, a third



452


transition appears in t h e 75°C temperature range. Such a supplementary t r a n s i t i o n has been r e p o r t e d b y o t h e r a u t h o r s (11,12)• As i t h a d n o t been o b s e r v e d i n o u r p r e v i o u s work, i t may w e l l c o r r e s p o n d t o a new phase, i . e . a s p e c i a l s t a t e o f i n t e r p e n e t r a t i o n o f t h e two components due t o t h e s p e c i f i c e x p e r i m e n t a l conditions used. Simultaneously, t h e peak c o r r e s p o n d i n g t o the m e t h a c r y l i c phase i s shifted towards h i g h e r temperatures and becomes a g a i n s h a r p e r , a s i g n t h a t l a r g e r domains o f PMMA, c o n t a i n i n g no o r l i t t l e PUR, e x i s t i n such m a t e r i a l s . F o r 0.35%, one v e r y b r o a d transition extends from -50°C t o 100°C, an i n d i c a t i o n o f t h e e x i s t a n c e o f one phase o f c o n t i n u o u s l y v a r y i n g c o m p o s i t i o n (13,14). The PMMA peak is shifted t o an unexpected 150°C, perhaps due t o a v e r y h i g h crosslink d e n s i t y made p o s s i b l e b y a more complete c r o s s l i n k i n g reaction i n a n e a r l y pure m e t h a c r y l i c medium, t h a n when PUR i s p r e s e n t . F o r s t i l l lower amounts o f c a t a l y s t , two more and more individualized peaks indicate an i n c r e a s i n g s e p a r a t i o n o f the phases : due t o t h e i n c o m p l e t e f o r m a t i o n o f t h e f i r s t network, an i r r e v e r s i b l e and i n t i m a t e i n t e r p e n e t r a t i o n o f t h e two components i s not possible. In this 25/75 series, t h e SIM IPN w i t h 0.1% OcSn c o n t a i n s t h e most u n c o m p l e t e l y formed PUR, and t h e lower peak i s s h i f t e d t o -56°C ( T g = -40°C) due t o f r e e o r pendant d i o l c h a i n s . p u R

T a b l e I . S t o r a g e modulus and l o s s t a n g e n t v a l u e s a t room temperature and a t 100°C f o r a s e r i e s o f 25/75 SIM PUR/PAc IPNs o b t a i n e d w i t h v a r i o u s amounts o f stannous o c t o a t e

Temperature 24°C [OcSn] (%) 0.10 0.25 0.35 0.50 0.75 1.00 1.00* PAc *

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730 550 440 405 445 555 650 1360

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SEQ IPN

The v a l u e s o f t a n 8, g i v e n i n T a b l e I , v a r y also with the concentration o f OcSn, b y a f a c t o r o f 2 t o 4 depending on temperature. So, f o r b o t h t h e p o s i t i o n on t h e temperature s c a l e and the l o s s v a l u e , quite different loss b e h a v i o r s c a n be o b t a i n e d by i n f l u e n c i n g t h e k i n e t i c s o f f o r m a t i o n o f t h e networks. The v a r i a t i o n of the storage moduli G' w i t h temperature, shown i n F i g u r e 6, complete t h e s e r e s u l t s . They d i f f e r most at higher temperatures, upwards 50°C/60°C. A t low c a t a l y s t c o n t e n t s , they a r e h i g h e s t , due



25.

TABKAETAL.

453


temperature (*C) F i g u r e 6. Shear s t o r a g e modulus v e r s u s temperature f o r a s e r i e s o f 25/75 SIM PUR/PAc IPNs o b t a i n e d w i t h v a r i o u s amounts o f stannous o c t o a t e : (•): 1.0%; (•): 0.5%; (•): 0.35%; ( A ) : 0.25%; (•): 0.1%. to the well individualized rigid phase ( 1 5 ) ; when the l a t t e r d i s a p p e a r s p r o g r e s s i v e l y w i t h i n c r e a s i n g c o n c e n t r a t i o n o f OcSn, t h e s t o r a g e modulus o f the IPNs a t 100°C d e c r e a s e s by a f a c t o r of t e n (Table I ) . The l o s s p r o p e r t i e s o f SIM IPNs w i t h o t h e r PUR c o n t e n t s , from 15 t o 50 wt-%, have a l s o been examined. O b v i o u s l y , the amount o f elastomer influences the overall p r o p e r t i e s b y i t s e l f , b u t the s p e c i f i c behavior o b s e r v e d f o r the 25/75 s e r i e s i s r o u g h l y found a g a i n f o r the o t h e r c o m p o s i t i o n s . However, i n the 15/85 SIM IPNs, the l o s s c u r v e s are not q u i t e d i f f e r e n t from each o t h e r , and p r e s e n t a l l a d i s t i n c t methacrylic t r a n s i t i o n . For such a c o m p o s i t i o n , the low p o l y u r e t h a n e c o n t e n t does not c o n t r i b u t e much t o the shape o f the c u r v e , and the networks have a l s o many d e f e c t s ( 9 ) , so t h a t , a t the same time, t h e lower transition i s weak, and n o t p r e c i s e l y l o c a t e d on the temperature s c a l e , whereas the upper t r a n s i t i o n i s s h a r p e r and w e l l d e f i n e d . The 50/50 SIM IPNs, on the o t h e r hand, show ( F i g u r e 7) a most r e g u l a r and b r o a d t r a n s i t i o n f o r the higher OcSn c o n t e n t s , [OcSn] > 0.50%, and a l s o h i g h e r l o s s v a l u e s a t low temperatures, due to t h e i r e l a s t o m e r c o n t e n t . The e x t e n s i o n t o the o t h e r c o m p o s i t i o n s g i v e s t h e r e f o r e the p o s s i b i l i t y to combine both appropriate loss b e h a v i o r and e l a s t o m e r i c p r o p e r t i e s f o r an IPN, depending on the s p e c i f i e d end-use. More g e n e r a l l y , the composition i s no more the o n l y parameter a v a i l a b l e f o r c h a n g i n g the p r o p e r t i e s o f such m a t e r i a l s . However, a f u l l q u a n t i t a t i v e i n t e r p r e t a t i o n o f the p r e c e d i n g r e s u l t s cannot y e t be g i v e n , due t o the v e r y complex morphology o f IPNs ( 1 ) . I t seems normal t h a t a l l o w i n g the PUR, o r any o t h e r host network, t o form more o r l e s s c o m p l e t e l y , w i l l i n d u c e morphological changes i n the r e s u l t i n g IPNs. I n so f a r , o b t a i n i n g e i t h e r r a t h e r


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F i g u r e 7. Loss tangent versus temperature c u r v e s f o r 5 0 / 5 0 SEQ (open s y m b o l s ) and SIM ( f u l l s y m b o l s ) PUR/PAc IPNs as a f u n c t i o n of catalyst concentration: (0,4): 1.0%; (#) : 0 . 5 % ; (•) : 0.35%; (A): 0.2%; ( • ) : 0.1%. i n d i v i d u a l i z e d phases o r on the c o n t r a r y i n t e r p e n e t r a t e d phases can be explained by the experimental procedure utilized. But no t h e o r e t i c a l model a l l o w s to f o r e s e e a t h i r d t r a n s i t i o n (16.) o r one very broad transition (17,18). One must admit that interphases resulting from specific synthesis conditions are formed, which


25. TABKAETAL.


455


correspond to combinations o f PUR and PAc w i t h well defined composition and degree o f i n t e r p e n e t r a t i o n . A c c o r d i n g l y , a phase enriched i n PUR w i t h regard t o t h e i n i t i a l c o m p o s i t i o n , would c o e x i s t w i t h a (perhaps p u r e ) m e t h a c r y l i c phase. Transmission electron microscopy and small-angle X-ray scattering experiments, still at t h e i r beginning, corroborate at l e a s t q u a l i t a t i v e l y these f i n d i n g s and i n t e r p r e t a t i o n s , so t h a t more a c c u r a t e s y n t h e s i s - p r o p e r t i e s r e l a t i o n s h i p s may be e s t a b l i s h e d soon, d e s p i t e t h e c o m p l e x i t y o f t h e problem. C O N C L U S I O N Two c o n c l u s i o n s emerge from this i n v e s t i g a t i o n : an a d e q u a t e l y selected s y n t h e s i s parameter i s able t o change t h e k i n e t i c s o f f o r m a t i o n o f one o r b o t h networks t o a n o t n e g l i g e a b l e e x t e n t ; t h e subsequent e v o l u t i o n i n k i n e t i c s allows a stepwise m o d i f i c a t i o n o f properties o f IPNs, without the n e c e s s i t y to change their composition. This approach, which y i e l d s t h e so c a l l e d "in situ simultaneous" class o f IPNs, offers new p o s s i b i l i t i e s f o r t h e s e m a t e r i a l s . A c c o r d i n g t o t h e i r f i n a l d e s t i n a t i o n , i t becomes p o s s i b l e to select, after chemical nature and c o m p o s i t i o n , a synthesis parameter which m o d i f i e s the s p e c t r a o f p r o p e r t i e s i n t h e e x p e c t e d way. E s p e c i a l l y , i n t h i s example, m a t e r i a l s w i t h a b r o a d temperature range o f damping were o b t a i n e d by t h i s means.

LITERATURE 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

CITED

Sperling, L. H. Interpenetrating Polymer Networks and Related Materials; Plenum Press: New York, 1981. Djomo, H.; Morin, A.; Damyanidu, M.; Meyer, G. C. Polymer 1983, 24, 65 . Djomo, H.; Widmaier, J. M.; Meyer, G. C. Polymer 1983, 24, 1415. Morin, A.; Djomo, H.; Meyer, G. C.Polym.Eng. Sci. 1983, 23, 94. Hermant, I.; Damyanidu, M.; Meyer, G. C. Polymer 1983, 24, 1419. Jin, S. R.; Meyer, G. C. Polymer 1986, 27, 592. Jin, S. R.; Widmaier, J. M.; Meyer, G. C. Polym. Comm. 1988, 29, 26. Jin, S. R.; Widmaier, J. M.; Meyer, G. C. Polymer 1988, 29, 346. Tabka, M. T.; Widmaier, J. M.; Meyer, G. C. Macromolecules 1989, 22, 1826. Curtius, A. J.; Covitch, M. J.; Thomas, D. A.; Sperling, L. H. Polym. Eng. Sci. 1972, 12, 101. Lipatov, Y. S.; Chramova, T. S.; Sergeeva, L. M.; Karabanova, L.V. J.Polym.Sci., Polym. Chem. Ed. 1977, 15, 427. Frisch, H. L.; Frisch, K. C.; Klempner, D. Pure Appl. Chem. 1981, 53, 1557. Lee, D. S.; Kim, S. C. Macromolecules 1984, 17, 268. Akay, M.; Rollins, S. N.; Riordan, E. Polymer 1988, 29, 37. Fox, R. B.; Bitner, J. L.; Hinckley, J. A.; Carter, W. Polym. Eng. Sci. 1985, 25, 157. Wang, K. J.; Hsu, T. J.; Lee, L. J. Polym. Eng. Sci. 1989, 29, 397.


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17. Jordhamo, G. M.; Manson, J. A.; Sperling, L. H. Polym. Eng. Sci. 1986, 26, 517. 18. Rosovizky, V. F.; Ilavsky, M.; Hrouz, J . ; Dušek, K.; Lipatov, Y. S. J. Appl.Polym.Sci. 1979, 24, 1007. RECEIVED January 24, 1990


Sound and Vibration Damping with Polymers - American Chemical

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