Properties of Compatible Blends of Poly(vinylidene fluoride) and Poly

32 Properties of Compatible Blends of Poly(vinylidene fluoride) and Poly(methyl methacrylate) Downloaded by UNIV OF SYDNEY on September 29, 2015 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/ba-1975-0142.ch032

D. R. PAUL and J. O. ALTAMIRANO Department of Chemical Engineering, University of Texas, Austin, Texas 78712 Evidence of the miscibility of poly(vinylidenefluoride)and poly(methyl methacryate) is confirmed by the extensive studies of the dynamic behavior of their blends that are reported here. The blends, as well as the pure polymers, have multiple transitions. There is a single transition which shifts with blend composition as would be expected in compatible systems; however, for PVF this is not the transition generally identified as T . The T of the blend, the T of the PVF , and the relative amount of crystallinity as a function of blend composition were examined by DTA. Density data indicate a lack of volume additivity caused primarily by the varying crystallinity of PVF -rich blends. 2

g

m

g

2

2

B

e c a u s e of t h e r m o d y n a m i c s , t r u l y m i s c i b l e p o l y m e r p a i r s a r e r a r e ( 1 ) . E v i d e n c e s t r o n g l y suggests t h a t p o l y ( v i n y l i d e n e f l u o r i d e ) , P V F , a n d p o l y ( m e t h y l m e t h a c r y l a t e ) , P M M A , a r e m i s c i b l e w h e n m e l t b l e n d e d ( 2 , 3, 4, 5 ) . B l e n d s c o n t a i n i n g c e r t a i n p r o p o r t i o n s of t h e s e t w o p o l y m e r s a r e a v a i l a b l e c o m m e r c i a l l y ( 6 ) . C o n s e q u e n t l y , m o r e extensive studies of blends m a d e f r o m t h i s p o l y m e r p a i r w e r e i n t e r e s t i n g t o u s . P r e v i o u s efforts t o e s t a b l i s h t h e c o m p a t i b i l i t y o f t h i s p a i r w e r e b a s e d o n o b s e r v i n g t h e glass t r a n s i t i o n b e h a v i o r of b l e n d s , m a i n l y b y t h e r m a l a n a l y s i s a n d d i l a t o m e t r y ( 2 ) . T h i s r e p o r t d e a l s w i t h a d d i t i o n a l t h e r m a l a n a l y s i s i n c l u d i n g e x a m i n a t i o n of P V F c r y s t a l l i z a t i o n f r o m c e r t a i n b l e n d s . E m p h a s i s is o n t h e t r a n s i t i o n a l b e h a v i o r i n d i c a t e d b y d y n a m i c mechanical properties w h i c h has not been reported previously. Specific v o l u m e measurements are discussed briefly. 2

2

T h e P V F , K y n a r 301, was obtained from Pennwalt, a n d the P M M A , Plexiglas V ( 811)-100, was from R o h m a n d Haas. Blends were made b y melt m i x i n g i n a B r a b e n d e r P l a s t i c o r d e r 1 0 m i n at 2 0 0 ° C . S h e e t s w e r e c o m p r e s s i o n m o l d e d , a n d s a m p l e s w e r e a n n e a l e d at 1 1 5 ° C f o r 2 0 m i n t o d e v e l o p m a x i m u m crystallinity. O t h e r w i s e , c r y s t a l l i z a t i o n of s o m e b l e n d s w o u l d o c c u r l a t e r d u r i n g testing. 2

Thermal

Analysis

of

Blends

D i f f e r e n t i a l t h e r m a l a n a l y s i s ( D T A ) of b l e n d s a n d p u r e c o m p o n e n t s w a s d o n e c y c l i c a l l y b y s u c c e s s i v e h e a t i n g a n d c o o l i n g at 1 0 ° C / m i n b e t w e e n — 1 0 0 ° 371

In Copolymers, Polyblends, and Composites; Platzer, N.; Advances in Chemistry; American Chemical Society: Washington, DC, 1975.

372

COPOLYMERS,

POLYBLENDS,

A N D COMPOSITES

and 200°C. F i r s t heat analyses often differed somewhat f r o m subsequent h e a t s w h i c h g a v e i d e n t i c a l d a t a f o r as m a n y as six r e p e t i t i o n s . O n l y t h e l a t e r h e a t a n a l y s e s a r e d i s c u s s e d b e c a u s e t h e y a r e r e p r o d u c i b l e . A s N o l a n d et ai. ( 2 ) observed, certain blends r i c h i n P V F have a melting endotherm characteristic of P V F w h e r e a s b l e n d s r i c h i n P M M A a r e t o t a l l y a m o r p h o u s . 2

2

F i g u r e 1 shows the m e l t i n g e n d o t h e r m area w i t h arbitrary units n o r m a l i z e d f o r s a m p l e m a s s . B l e n d s c o n t a i n i n g 5 0 % o r less P V F h a v e n o m e l t i n g e n d o t h e r m ; b e y o n d this p o i n t , h o w e v e r , c r y s t a l l i n i t y increases r a p i d l y w i t h P V F content. T h e dashed line connects the zero value f o r amorphous p u r e P M M A w i t h the observed area f o r p u r e P V F . T h i s is the peak area expected i f P M M A d i d not interfere w i t h P V F crystallization b u t merely diluted the s a m p l e m a s s . O b v i o u s l y , b l e n d i n g does i n t e r f e r e w i t h c r y s t a l l i z a t i o n . F i r s t h e a t areas f o r a n n e a l e d s a m p l e s w e r e l a r g e r t h a n these o b t a i n e d w i t h c y c l i c a l heating. Blends containing 5 0 % P V F s h o w e d slight crystallinity after the first h e a t b u t n o n e a f t e r s u b s e q u e n t h e a t s w h e r e a s b l e n d s c o n t a i n i n g 4 0 % or less P V F n e v e r s h o w e d e v i d e n c e of c r y s t a l l i n i t y . 2

2

2

Downloaded by UNIV OF SYDNEY on September 29, 2015 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/ba-1975-0142.ch032

2

2

2

T h e temperature location of the m e l t i n g peak, T , v a r i e d slightly w i t h b l e n d c o m p o s i t i o n (see u p p e r p o r t i o n of F i g u r e 2 ) . T h e m a x i m u m d e p r e s s i o n in T w a s about 1 0 ° C . T h e r m o d y n a m i c calculations based o n conventional m i x t u r e theories w h i c h account f o r the r e d u c t i o n i n c h e m i c a l p o t e n t i a l that o c c u r s o n m i x i n g (7) i n d i c a t e t h a t a m i s c i b l e d i l u e n t w i t h t h e m o l e c u l a r w e i g h t of P M M A c a n n o t p r o d u c e a d e p r e s s i o n t h i s l a r g e . It is l i k e l y t h a t t h e m a j o r e f f e c t is m o r p h o l o g i c a l , e.g. s m a l l e r o r less p e r f e c t c r y s t a l l i n e r e g i o n s d e v e l o p w l

m

301

1

1

1

Weight % P V F Figure 1.

τ

2

Relative crystallinity of PVFa-PMMA as determined by DTA

blends


32.

Compatible

AND ALTAMIRANO

PAUL

π

1

1

1

1

Polymer

1

Blends

1

ι

373

1 —1170

Ο ο


A160

Ο ο ,cr>

60

20

40

60

80

Weight % P V F Figure 2. from blends. blends

100

2

DTA observed transitions for PVF -PMMA

blends

2

Similar reductions

in T

m

have

been

observed i n incompatible

(8).

A l l the blends s h o w e d a single T

0

b y D T A , w i t h i n t h e l i m i t s of d e t e c t i o n

w h i c h w a s quite strong for the w h o l l y amorphous samples.

T h e lower portion

of F i g u r e 2 s h o w s t h e l o c a t i o n of t h i s t r a n s i t i o n as a f u n c t i o n o f b l e n d c o m position.

A s crystallinity increases w i t h increasing P V F

of t h i s t r a n s i t i o n d i m i n i s h e s r a p i d l y . DTA

of a Τ

g

2

content, the intensity

Beyond 6 0 % P V F , 2

for blends were comparable

a l l indications b y

i n m a g n i t u d e to instrument

noise,

a n d c o n s e q u e n t l y n o values are r e c o r d e d i n this range i n F i g u r e 2. D T A also f a i l e d t o r e v e a l a n u n a m b i g u o u s glass t r a n s i t i o n f o r p u r e P V F of 1 0 ° C / m i n .

T h e d e p e n d e n c e of T

g

2

at c o o l i n g rates

on blend composition shown i n Figure 2

is c o n s i s t e n t w i t h t h e e x p e r i m e n t a l d a t a of N o l a n d et al. ( 2 ) , a n d t h i s c o n f i r m s t h e i r c o n c l u s i o n of m i s c i b i l i t y f o r t h i s p o l y m e r p a i r , at least t o P V F

contents

2

where crystallinity develops.

F o r blends w i t h crystallinity, one might picture

a two-phase

the crystalline regions

structure where

a m o r p h o u s r e g i o n s a r e a c o m p a t i b l e m i x t u r e of P V F

are p u r e P V F 2

and P M M A .

a n d the

2

This mix

t u r e c o m p o s i t i o n d i f f e r s f r o m t h a t of t h e t o t a l b l e n d a n d is r i c h e r i n P M M A


374

COPOLYMERS,

POLYBLENDS,

A N D COMPOSITES

b e c a u s e of loss of P V F b y c r y s t a l l i z a t i o n . P a r t i t i o n i n g of P V F b e t w e e n t h e s e phases m a y o c c u r o n a k i n e t i c rather t h a n a t h e r m o d y n a m i c basis. Some e v i d e n c e f o r c o m p a t i b i l i t y i n t h e a m o r p h o u s r e g i o n s is p r e s e n t e d b e l o w (see section o n d y n a m i c m e c h a n i c a l p r o p e r t i e s ) . 2

2

N o l a n d et al. (2) e n c o u n t e r e d s i m i l a r d i f f i c u l t y i n m e a s u r i n g b y t h e r m a l analysis or d i l a t o m e t r y the T of blends v e r y r i c h i n P V F . H o w e v e r , t h e y state t h a t t h e i r T d a t a , w h i c h c o v e r a c o m p o s i t i o n r a n g e s i m i l a r t o t h a t i n F i g u r e 2, are consistent w i t h extrapolation to —40° to — 4 6 ° C f o r p u r e P V F . T h e y w e r e a b l e t o m e a s u r e T d i r e c t l y (— 4 6 ° C ) u s i n g t h e r m a l a n a l y s i s f o r rapidly quenched P V F samples. I n subsequent discussions, it is i m p o r t a n t to r e m e m b e r t h a t f o r t h i s p o l y m e r c o n s i d e r a b l e u n c e r t a i n t y m a y b e a s s o c i a t e d w i t h t h i s o b s e r v a t i o n o r i t s i n t e r p r e t a t i o n b e c a u s e of t h e d i f f i c u l t i e s p o s e d b y h i g h c r y s t a l l i n i t y (2). T h e r e is c o n s i d e r a b l e e v i d e n c e (9-16) t o s u p p o r t a Τ v a l u e f o r P V F i n t h i s r a n g e ; h o w e v e r , as N o l a n d et al. (2) n o t e d , t h e r e is s o m e c o n t r o v e r s y a b o u t t h i s s i n c e h i g h e r v a l u e s , 1 3 ° a n d 2 7 ° C , h a v e b e e n s u g g e s t e d (17, 18). W e m e n t i o n this here because the subsequent d y n a m i c m e c h a n i c a l p r o p e r t y data are n o t d i r e c t l y consistent w i t h this s i m p l i s t i c e x t r a p o l a t i o n o r a c c e p t a n c e o f t h e — 4 0 ° C r e g i o n as t h e T f o r P V F . M o r e r e c e n t l y N a k a g a w a a n d I s h i d a (19) r e p o r t e d a s m a l l s p e c i f i c h e a t j u m p by D S C for P V F that occurs between - 5 0 ° a n d - 3 0 ° C . More thorough e x a m i n a t i o n of o u r P V F p o l y m e r b y D S C (20) r e v e a l e d a s l i g h t b a s e - l i n e drift over the —40° to 0 ° C range. T h i s change w a s v e r y small a n d indis tinct i n some t h e r m a l traces. O u r T data presented i n F i g u r e 2 are n o t at a l l c o n c l u s i v e r e g a r d i n g e x t r a p o l a t i o n s to p u r e P V F . I f t h e s l i g h t c u r v a t u r e is r e a l , t h e n a n i n t e r c e p t of + 2 0 ° C o r h i g h e r w o u l d b e p o s s i b l e . H o w e v e r , i f 2

g

g

2

g


2

g

2

2

g

2

2

g

2

h-V 20

40

60

Weight % P V F Figure 3.

100

80

2

Specific volume of annealed PVFz-PMMA

blends


r


32.

P A U L AND ALTAMIRANO

Compatible

Polymer

375

Blends

t h i s c u r v a t u r e i s i g n o r e d a n d t h e e x t r a p o l a t i o n i s b a s e d o n t h e first f e w P M M A r i c h points, it w i l l meet the P V F Specific

Volume

The

of

2

axis at - 2 0 ° t o

Blends

s p e c i f i c v o l u m e of a n n e a l e d

technique.

-25°C.

blends was measured b y a

pycnometer

T h e d a t a a r e p l o t t e d vs. b l e n d c o m p o s i t i o n i n F i g u r e 3 .

Estimates

of t h e s p e c i f i c v o l u m e f o r t o t a l l y c r y s t a l l i n e , V , a n d t o t a l l y a m o r p h o u s , V , c

PVF

2

reported b y N a k a g a w a a n d Ishida

the right.

The V

a

a

( 2 1 ) are i n d i c a t e d b y the arrows o n

v a l u e differs c o n s i d e r a b l y f r o m the estimate ( 0 . 6 7 6 c m / g )

of D o l e a n d L a n d o

3

( 2 2 ) , b u t i t is c o n s i d e r e d m o r e a c c u r a t e .

agrees w e l l w i t h that r e p o r t e d b y D o l e a n d L a n d o . mined

value

amorphous sample.

of V for pure

a n d crystalline

PVF

values

2

lies

indicates

halfway

50%

a

for pure P V F .

PMMA.

T h e data for

2

the a m o r p h o u s , P M M A - r i c h blends lie closer to the b r o k e n line whereas 2

a d d i t i v i t y as d e f i n e d b y e i t h e r l i n e s h o u l d n o t b e e x p e c t e d analysis

of these data

blend

the

crystallinity for our

f o r t h e c r y s t a l l i n e , P V F - r i c h b l e n d s l i e c l o s e r to t h e s o l i d l i n e . c a u s e of v a r i a t i o n i n c r y s t a l l i n i t y w i t h

deter-

between

T h e solid line connects this p o i n t w i t h that f o r a m o r p h o u s

T h e b r o k e n line connects the latter w i t h the V

value

c

T h e experimentally

approximately

which

The V

composition.

those

Strict v o l u m e

for all blends beA more

can be effected b y defining a n apparent

detailed

density for


376

COPOLYMERS, POLYBLENDS, A N D COMPOSITES

PVF

2

i n the b l e n d , ρ

Ρ ν

ρ , as: 2

1 _ Ρ

w

(1 - w)

PPVF2

PPMMA

w h e r e ρ is t h e o b s e r v e d d e n s i t y o f a b l e n d c o n t a i n i n g a w e i g h t f r a c t i o n , w, o f PVF , 2

PPVF

2

a n d P MA PM

i

s

the observed

density

of p u r e

is r e l a t e d

to t h e p a r t i a l specific

F i g u r e 4 shows apparent P V F

2

v o l u m e of this c o m p o n e n t ,

but not simply.

1, t h e d e n s i t y i s t h a t o b s e r v e d f o r p u r e P V F , b u t i t d e c r e a s e s as P M M A

w =

2

on blending when P V F

2

Figure

(see

1).

Annealed blends

crystallinity that

occurs

showed no endotherm

at a l l

2

c o n t e n t w a s 4 0 % o r less; t h u s o n e w o u l d e x p e c t t h a t t h e a p p a r e n t

density w o u l d a p p r o a c h the a m o r p h o u s density of P V F i n g t o R e f . 20) PVF

T h e calculated

d e n s i t y as a f u n c t i o n o f b l e n d c o m p o s i t i o n . A t

is a d d e d , p r i m a r i l y b e c a u s e o f t h e r e d u c t i o n i n P V F


PMMA.

v a l u e i s t h e d e n s i t y t h a t is n e e d e d t o a s s u r e v o l u m e a d d i t i v i t y , a n d i t

2

2

(1.667 g / c m

3

accord

a t 4 0 % a n d t h e n w o u l d r e m a i n c o n s t a n t at t h i s l e v e l f o r l o w e r

contents if crystallinity were the only factor.

experimentally until P V F

2

content has been

T h i s value is not reached

r e d u c e d to 3 0 % , a n d i t appears

10'

^ÎOÔ

^50

0

50

100

Temperature, °C Figure 5.

Dynamic mechanical properties of annealed PVF

2

at 110 Hz



32.


Compatible

Polymer

377

Blends

Temperature, °C Figure 6. to

continue

Dynamic mechanical properties of annealed PMMA

decreasing

thereafter

although

experimental

at 110 Hz

uncertainty

i n the

a p p a r e n t d e n s i t y i n c r e a s e s r a p i d l y as w a p p r o a c h e s z e r o . L a c k o f v o l u m e a d d i tivity i n the amorphous phase

(arising f r o m molecular interactions)

c o n t r i b u t e to t h e o b s e r v e d apparent density. m a y be operative here,

with

c a n also

T h e data suggest that this effect

the volume changes o n m i x i n g being

for P V F - r i c h blends a n d positive for P M M A - r i c h blends. 2

negative

H o w e v e r , the con

c o m i t a n t a n d m o r e massive effect of c r y s t a l l i n i t y makes this c o n c l u s i o n u n c e r t a i n . Dynamic

Mechanical

Properties

of

Blends

T h e d y n a m i c m e c h a n i c a l p r o p e r t i e s , £ ' , E " , a n d t a n 8, o f a n n e a l e d b l e n d s and pure components tometer.

w e r e m e a s u r e d at 1 1 0 H z b y a R h e o v i b r o n v i s c o e l a s -

Data for pure P V F

2

are presented i n F i g u r e 5.

Three principal re

l a x a t i o n r e g i o n s , l a b e l e d « , β, a n d γ , w e r e o b s e r v e d p r e v i o u s l y f o r t h i s p o l y m e r type b y various techniques.

M a r k e r s i n d i c a t e t h e range of p e a k

temperatures

for each transition reported i n the literature f o r a f r e q u e n c y of 110 H z . F o r u n k n o w n r e a s o n s , o u r a p e a k o c c u r s at a s o m e w h a t l o w e r t e m p e r a t u r e ; ever, w e believe this is the same transition.

how

L o c a t i o n s of the β a n d γ peaks


378

COPOLYMERS,

POLYBLENDS,

A N D COMPOSITES

agree w e l l w i t h the literature. M o s t reports w o u l d be compatible w i t h the m e c h a n i s m s f o r these d i s p e r s i o n regions g i v e n b y Y a n o ( 1 0 ) : a , m o l e c u l a r m o t i o n s a s s o c i a t e d w i t h c r y s t a l l i n e r e g i o n s a n d t h e i r d e f e c t s ; β, m o t i o n o f t h e m a i n c h a i n i n t h e a m o r p h o u s r e g i o n w h i c h m a y t h u s b e r e g a r d e d as t h e m a i n T ; γ, local molecular m o t i o n i n the amorphous regions. H o w e v e r , Peterlin a n d H o l b r o o k (17, 18) a s s i g n e d d i f f e r e n t m e a n i n g s t o t h e s e p e a k s ( w h i c h t h e y l a b e l e d d i f f e r e n t l y ) . T h e y suggest that t h e a peak discussed here is c a u s e d b y r o t a t i o n of d i p o l e s o f c h a i n s i n c r y s t a l d e f e c t s . T h e y m e n t i o n e d a p r e m e l t i n g peak at h i g h e r temperatures, b u t they d i d n o t extend their measurements to l o w e n o u g h t e m p e r a t u r e s t o see t h e γ r e g i o n . T h e y r e f e r r e d t o c a l o r i m e t r i c a n d d i l a t o m e t r i c m e a s u r e m e n t s (17) t h a t l o c a t e T at 1 3 ° C a n d r e f e r e n c e o t h e r d i l a t o m e t r i c d a t a o f t h e i r s (18) t h a t fix t h i s v a l u e a t 2 7 ° C . g


g

D a t a for p u r e P M M A ( F i g u r e 6) indicate t w o major relaxation regions l a b e l e d a a n d β. M a r k e r s i n d i c a t e t h e r a n g e s r e p o r t e d i n t h e l i t e r a t u r e f o r t h e s e t r a n s i t i o n s at 1 1 0 H z . T h e a p e a k is t h e m a i n T ( 2 3 ) , a n d the data l o c a t e i t at 1 0 5 ° C b y E" a n d at 1 4 2 ° C b y t a n δ. T h i s w i d e s e p a r a t i o n o f t h e g

Figure 7.

Dynamic mechanical properties at 110 Hz for an annealed 80 wt % PVF blend 2


32.


Compatible

Polymer

379

Blends


10'

I

I

I

-100

I

-50

ι

0

I

50

L_l

100

150



p e a k s i s c o m m o n f o r w h o l l y a m o r p h o u s p o l y m e r s (24).

T h e β region is be

l i e v e d t o a r i s e f r o m r o t a t i o n s o f t h e ester s i d e g r o u p ( 2 3 ) , a n d i t a p p e a r s h e r e as a s h o u l d e r i n E" a n d t a n δ i n t h e v i c i n i t y o f 5 0 ° C .

T h e presence of w a t e r is

k n o w n to p r o d u c e a l o w t e m p e r a t u r e r e l a x a t i o n (23)

w h i c h is w e a k l y e v i d e n t

here. T h e d y n a m i c m e c h a n i c a l p r o p e r t i e s of v a r i o u s P V F - P M M A 2

shown i n Figures 7 - 1 1 . F o r the 8 0 % a n d 6 0 % P V F

2

blends are

blends (Figures 7 a n d 8)

w h i c h a r e p a r t i a l l y c r y s t a l l i n e , t h e r e a r e t w o m a j o r p e a k s i n e i t h e r E" o r t a n δ. T h e h i g h e r t e m p e r a t u r e p e a k is m o r e d o m i n a n t a n d w o u l d a p p e a r t o b e t h e T

g

of t h e b l e n d .

As P M M A

content

shifts t o w a r d h i g h e r temperatures. of p u r e P V F

2

increases,

this peak

becomes

larger a n d

It a p p e a r s t o d e g e n e r a t e i n t o t h e a p e a k

shown i n Figure 5 when P M M A

content decreases to zero. T h e

l o w e r t e m p e r a t u r e p e a k decreases i n m a g n i t u d e a n d shifts t o w a r d l o w e r t e m p e r a t u r e s as P M M A c o n t e n t i n c r e a s e s ; w h e n a l l P M M A i s e l i m i n a t e d , i t a p p e a r s to r e d u c e to t h e P V F

2

β peak.


380

COPOLYMERS,

POLYBLENDS,

A N D COMPOSITES

F o r the noncrystalline 4 0 % , 2 0 % , a n d 1 0 % P V F blends ( F i g u r e s 9, 10, a n d 1 1 ) , t h e r e i s o n e m a j o r p e a k w h i c h o c c u r s v e r y n e a r t h e e n d of t h e t e m p e r a t u r e r a n g e . T h i s p e a k is v e r y l a r g e , a n d t h e m a g n i t u d e o f t a n 8 is a l m o s t t h e s a m e f o r a l l t h r e e m a t e r i a l s . Its l o c a t i o n s h i f t s t o h i g h e r t e m p e r a t u r e s as P M M A c o n t e n t i n c r e a s e s . It i s c l e a r l y t h e m a i n T f o r t h e b l e n d s , a n d i t merges directly into the pure P M M A T peak w h e n a l l P V F is e l i m i n a t e d . T h e s h o u l d e r at a b o u t + 5 0 ° C is e s p e c i a l l y a p p a r e n t f o r t h e 1 0 % P V F b l e n d . T h i s is e v i d e n t l y the P M M A β dispersion, a n d i t does n o t shift a p p r e c i a b l y o n b l e n d i n g , a l t h o u g h i t s m a g n i t u d e d i m i n i s h e s as t h e P M M A is d i l u t e d w i t h P V F . A n o t h e r s i g n i f i c a n t s h o u l d e r a p p e a r s at o r b e l o w — 5 0 ° C f o r a l l t h r e e blends. T h i s is discussed b e l o w . 2

g

g

2

2


2

F i g u r e 1 2 s h o w s p e a k l o c a t i o n s as a f u n c t i o n of b l e n d c o m p o s i t i o n f o r the well-defined peaks i n F i g u r e s 7 - 1 1 (shoulders are not i n c l u d e d ) . Since the storage m o d u l u s drops p r e c i p i t o u s l y at the highest temperature transition, t h e t a n 8 a n d E" p e a k s o c c u r at q u i t e d i f f e r e n t t e m p e r a t u r e s ( 2 4 ) ; conse quently, both positions are indicated. Smooth curves, although sigmoidal i n





32.

P A U L AND A L T A M I R A N O

Compatible

Polymer

381

Blends

shape, c a n be d r a w n t h r o u g h the u p p e r transitions for the blends w h i c h nect w i t h the major

T

g

p e a k of p u r e P M M A

a n d t h e a p e a k of p u r e

O n l y t h e E" p e a k is s h o w n f o r t h e l o w e r t e m p e r a t u r e p e a k s at s u b s t a n t i a l l y t h e s a m e l o c a t i o n .

2

T h e y can be connected

β peak b y a simple curve.

F o r miscible p o l y m e r blends, one expects a single T

w h i c h depends on

g

c o m p o s i t i o n i n s u c h a w a y as t o c o n n e c t t h e T s g

(25, 2 6 ) .

2

transition since t a n δ

O n l y t w o points are s h o w n f o r blends

s i n c e these are t h e o n l y ones t h a t s h o w a d i s t i n c t p e a k . to t h e p u r e P V F

con PVF .

of t h e t w o p u r e

components

T o d a t e , h o w e v e r , t h e r e is v e r y l i t t l e to suggest w h a t s h o u l d h a p p e n

to s e c o n d a r y a m o r p h o u s p e a k s o r those a s s o c i a t e d regions w h i c h w o u l d i n c l u d e P M M A interpretations

noted

P M M A are m i s c i b l e . temperatures

above.

β and P V F

A l l evidence

w i t h motions i n crystalline 2

a a n d γ a c c o r d i n g to the

strongly

T h u s one might expect the P V F

suggests t h a t P V F 2

2

and

β peak to shift to h i g h e r

as P M M A is a d d e d , a n d to c o n n e c t w i t h t h e T

g

of P M M A ,


given

382

COPOLYMERS,

POLYBLENDS,

A N D COMPOSITES

that t h e β p e a k is T . F u r t h e r , o n e m i g h t expect t h e a p e a k to d i m i n i s h i n m a g n i t u d e as P M M A is a d d e d a n d s u b s e q u e n t l y t o d i s a p p e a r w h e n a l l c r y s t a l l i n i t y is lost, g i v e n t h a t t h e a p e a k is a s s o c i a t e d w i t h P V F c r y s t a l l i n e r e g i o n s . H o w e v e r , t h e d a t a f o r t h e b l e n d s , s h o w n i n F i g u r e 1 3 as t a n 8 c u r v e s , do n o t c o n f o r m to these expectations. I n s t e a d , w h e n P M M A is a d d e d , t h e PVF t a n 8 a n d E" p e a k s s h i f t as f o l l o w s . T h e β p e a k d i m i n i s h e s i n m a g n i t u d e a n d e v e n t u a l l y d i s a p p e a r s ( a p p r o x i m a t e l y w h e n a l l c r y s t a l l i n i t y i s lost ) . T h i s p e a k s e e m s t o s h i f t t o l o w e r t e m p e r a t u r e s as P M M A i s a d d e d ; h o w e v e r , t h i s m a y n o t b e r e a l , as i t c o u l d reflect t h e i n c r e a s e i n r e l a t i v e i m p o r t a n c e of t h e l o w e r t e m p e r a t u r e γ r e g i o n w h i c h o n l y a p p e a r s as a s h o u l d e r i n p u r e P V F . W h a t is e v i d e n t l y t h e s m a l l a p e a k increases i n m a g n i t u d e a n d shifts t o w a r d h i g h e r t e m p e r a t u r e s as P M M A i s a d d e d (see t h e h i g h t e m p e r a t u r e p o r t i o n of t h e 8 0 % a n d 6 0 % t a n 8 curves i n F i g u r e 1 3 ) . A f t e r a l l crys t a l l i n i t y h a s b e e n lost ( b e t w e e n 6 0 a n d 4 0 % P V F ) , t h i s p e a k n o l o n g e r increases i n m a g n i t u d e w i t h a d d e d P M M A , b u t i t does c o n t i n u e to shift t o w a r d higher temperatures. g

2

2


2

2

10'

10% PVF 90% PMMA 2

10',10

Ε ο CO

φ c

CO

ιο-

10"

-σ ο

c σ

108

-2

10'

-100

-50

50

0

100

150


Dynamic mechanical properties at 110 Hz for an annealed 10 wt % PVF blend S



32.

P A U L AND A L T A M I R A N O

1

1 0

1 20

Compatible

1

1 40

ι

Polymer

ι 60

ι

ι 80

Weight % P V F

383

Blends

ι

I 100

2

Figure 12. Effect of blend composition on temperature location of major peaks (locations of shoulders are not indicated)

T h e s e results a r e e a s i l y e x p l a i n e d b y t h e i n t e r p r e t a t i o n a n d β p e a k s g i v e n b y P e t e r l i n a n d H o l b r o o k (17,

18).

of t h e P V F

Figure

2

a

12 p l u s t h e

r e s u l t s d i s c u s s e d i n e a r l i e r sections

s t r o n g l y s u p p o r t this v i e w , a n d i t i s v e r y

t e m p t i n g to d r a w this c o n c l u s i o n .

H o w e v e r , this a p p r o a c h d e a l s t o o l i g h t l y

w i t h the considerable (JO). plex,

evidence

for the interpretations

a n d they

pose

some

intriguing

questions

about

explanation requires additional investigative techniques speculate

i n this d i r e c t i o n at t h e p r e s e n t

a b o u t t h e t r a n s i t i o n a l b e h a v i o r of P V F (16)

2

g

2

time.

polymer

blends;

H o w e v e r , other

are appropriate.

this

so w e c h o o s e n o t t o comments

N a k a g a w a a n d Ishida

recently described very extensive a n d t h o r o u g h investigations of relaxa

tions a n d m o l e c u l a r m o t i o n s i n P V F . Τ

summarized by Yano

I f t h e l a t t e r v i e w is c o r r e c t t h e n e x p l a n a t i o n o f o u r d a t a i s m o r e c o m

T h e y c o n c l u d e t h a t t h e β r e g i o n is t h e

f o r P V F ; h o w e v e r , t h e y d i d n o t e a n u m b e r of p e c u l i a r i t i e s b y w h i c h t h e T 2

behavior of P V F

g

2

differs f r o m that of other p o l y m e r s , a n d they suggest


that

384

COPOLYMERS,

POLYBLENDS, A N D COMPOSITES

— 3 8 ° C is o n l y a n a p p a r e n t T . T h e y d i s c u s s these m o t i o n s i n t e r m s of t h e size of t h e c o o p e r a t i v e l y r e a r r a n g i n g r e g i o n w h i c h is m a c r o s c o p i c at a v e r y l o w t e m p e r a t u r e , T , a n d w h i c h decreases to a m i n i m u m at T = + 3 0 ° C . S t a r k w e a t h e r (27) h a s p u b l i s h e d s o m e v e r y t h o r o u g h a n d i n t e r e s t i n g studies on molecular motions i n a n alternating ethylene-tetrafluoroethylene copolymer w h i c h of c o u r s e is i s o m e r i c w i t h P V F . H e also o b s e r v e d α, β, a n d γ r e g i o n s , a l t h o u g h t h e t e m p e r a t u r e l o c a t i o n s a r e n o t e x a c t l y t h e s a m e as those f o r P V F . H e c o n c l u d e s f r o m a v a r i e t y of e v i d e n c e t h a t t h e a a n d γ r e l a x a t i o n s reflect m o t i o n s i n a m o r p h o u s o r d i s o r d e r e d r e g i o n s , a n d that t h e β r e l a x a t i o n o c c u r s i n c r y s t a l l i n e r e g i o n s . H e notes t h a t these a s s i g n m e n t s p a r a l l e l those m a d e f o r polytetrafluoroethylene. g

2

3

2

2


Summary It is c l e a r f r o m o u r findings a n d t h e e a r l i e r w o r k o f N o l a n d et al. (2) that P V F a n d P M M A are compatible. H o w e v e r , no definitive mechanism has been i d e n t i f i e d t h a t e x p l a i n s t h e s p e c i f i c i n t e r a c t i o n s b e t w e e n these m o l e c u l e s t h a t m a k e s t h i s so. 2

ι

1

1

1

r

0

50

100

PMMA -100

-50

150

Temperature, °C Figure 13. For

Tan δ at 110 Hz for pure PVF and PMMA selected blends (broken lines) Z

(solid lines) and

clarify, portions of curves have been omitted; no significant peaks appear in omitted regions


32.


Compatible

Polymer

385

Blends

S e v e r a l serious q u e s t i o n s a b o u t t h e t r a n s i t i o n a l b e h a v i o r o f p u r e P V F have been raised. O n e might identify the a peak of P V F as i t s a m o r p h o u s p h a s e T i n o r d e r t o e x p l a i n F i g u r e 1 2 i n t e r m s of p r e v i o u s e x a m p l e s o f p o l y m e r c o m p a t i b i l i t y t h a t s h o w s i m p l e c o n n e c t i o n s b e t w e e n t h e TJs o f t h e p u r e c o m p o n e n t s ( 2 5 , 2 6 ) . T h e s i g m o i d a l s h a p e of t h e c u r v e i n F i g u r e 1 2 c a n n o t b e d e s c r i b e d b y t h e u s u a l t y p e of e q u a t i o n ( 2 5 , 26) t h a t g e n e r a l l y fits b l e n d d a t a . T h i s , h o w e v e r , m i g h t easily b e explained b y crystallinity w h i c h changes t h e amorphous phase composition b y r e m o v i n g P V F . T h e T f r o m D T A ( F i g u r e 2) has a different dependence o n overall b l e n d composition, perhaps because c r y s t a l l i n i t y is l o w e r as a r e s u l t o f c y c l i c h e a t i n g t h a n i t w a s i n t h e a n n e a l e d b l e n d s ( F i g u r e 1 2 ) . C r y s t a l l i z a t i o n of P V F from blends rich i n P V F does not necessarily signal i m m i s c i b i l i t y since t h e evidence indicates that a l l t h e P M M A a n d the r e m a i n i n g P V F f o r m a homogeneous amorphous phase. 2

2

g

2

g

2

2


2

Acknowledgments

The authors gratefully acknowledge helpful discussions and correspondence with J. W . Barlow, C . E . Locke, Y. Ishida, and A. Peterlin.

Literature Cited 1. Paul, D. R., Vinson, C. E., Locke, C. E., Polym. Eng. Sci. (1972) 12, 157. 2. Noland, J. S., Hsu, N. N.C.,Saxon, R., Schmitt, J. M., "Multicomponent Polymer Systems," ADVAN. CHEM. SER. (1971) 99, 15.

3. Koblitz, F. F., Petrella, R. G., Dukert, Α. Α., Christofas, Α., Pennsalt Corp., U.S. Patent 3,253,060 (1966). 4. Miller, C. H., American Cyanamid Corp., U.S. Patent 3,458,391 (1969). 5. Schmitt, J. M., American Cyanamid Corp., U.S. Patent 3,459,834 (1969). 6. Dohany, J. E., private communication. 7. Flory, P. J., "Principles of Polymer Chemistry," Cornell University, Ithaca, 1953. 8. Natov, M., Peeva, L., Djagarova, E.,J.Polym. Sci. Part C (1968) 16, 4197. 9. Mandelkern, L., Martin, G. M., Quinn, F. Α., J. Res. Nat. Bur. Std. (1957) 58, 137. 10. Yano, S.,J.Polym. Sci. Part A-2 (1970) 8, 1057. 11. Sasabe, H., Saito, S., Asahina, M., Kakutani, H.,J.Polym. Sci. Part A-2 (1969) 7, 1405. 12. Koizumi, N., Yano, S., Tsunashima, K., J. Polym. Sci. Part Β (1969) 7, 59. 13. Kakutani, H.,J.Polym. Sci. Part A-2 (1970) 8, 1177. 14. Ishida, Y., Watanbe, M., Yamafuji, K., Kolloid Z. (1964) 200, 48. 15. Koo, G. P., in "High Polymer Series," Vol. 25: "Fluoropolymers," L. A. Wall, Ed., Chap. 16, Interscience, New York, 1972. 16. Nakagawa, K., Ishida, Y.,J.Polym. Sci. Part A-2 (1973) 11, 1503. 17. Peterlin, Α., Holbrook, J. D., Kolloid Z. (1965) 203, 68. 18. Peterlin, Α., Elwell, J. (Holbrook), J. Mater. Sci. (1967) 2, 1. 19. Nakagawa, K., Ishida, Y., J. Polym. Sci. Part A-2 (1973) 11, 2153. 20. Locke, C. E., private communication. 21. Nakagawa, K., Ishida, Y., Kolloid Z. (1973) 251, 103. 22. Doll, W. W. Lando, J. B.,J.Macromol. Sci. Phys. (1968) B2, 219. 23. McCrum, N.G.,Read, Β. E., Williams,G.,"Anelasticand Dielectric Effects in Polymer Solids," Wiley, New York, 1967. 24. Locke, C. E., Paul, D. R., Polym. Eng. Sci. (1973) 13, 308. 25. Koleske, J. V., Lundberg, R. D.,J.Polym. Sci. Part A-2 (1969) 7, 795. 26. Krause, S., Roman, N.,J.Polym. Sci. Part A (1965) 3, 1631. 27. Starkweather, H. W., J. Polym. Sci. Part A-2 (1973) 11, 587. ;

RECEIVED February 20, 1974.


Properties of Compatible Blends of Poly(vinylidene fluoride) and Poly

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