Liquid InterfaceâAn Essential and Active Frontier of

1 The Solid/Liquid Interface— An Essential and Active Frontier of Science

Downloaded by UNIV OF NOTRE DAME on November 17, 2014 | http://pubs.acs.org Publication Date: June 1, 1968 | doi: 10.1021/ba-1968-0087.ch001

W. A. ZISMAN Naval Research Laboratory, Washington, D. C.

In this introductory

review to the symposium, attention is

given to the causes of the serious disagreements in the data reported in the literature on solid/liquid demanding

and

often-ignored

interfaces.

experimental

The

requirements

stem principally from the overriding influence on numerous properties of solid/liquid

interfaces of the outermost molecu-

lar composition of the solid surface and the properties of the first adsorbed monolayer.

Available

methods for puri-

fying chemicals and new and highly specific surface chemical techniques are doing much to assist investigators.

Many

promising subjects of current research interest about solid/ liquid interfaces are briefly discussed along with relevant literature.

Finally, a brief background

is given

concerning

the timeliness and need for each paper being offered in the symposium.

" C a c h p a p e r p r e s e n t e d at this s y m p o s i u m r e p o r t e d progress i n a n i m p o r t a n t area of research o n m o l e c u l a r processes at s o l i d / l i q u i d i n t e r faces.

D e s p i t e the o b v i o u s i m p o r t a n c e of s u c h interfaces i n b o t h f u n d a -

m e n t a l a n d a p p l i e d science, it is n o exaggeration to say that progress w a s p a i n f u l l y s l o w u n t i l a b o u t 20 years ago.

H o w e v e r , since t h e n b o t h

e x p e r i m e n t a l a n d t h e o r e t i c a l r e s e a r c h o n the subject has b e c o m e i n c r e a s ingly active, exciting, a n d productive.

T h a t this s y m p o s i u m s h o u l d b e

h e l d u n d e r the auspices of the A . C . S . D i v i s i o n of O r g a n i c C o a t i n g s a n d Plastics C h e m i s t r y is e s p e c i a l l y a p p r o p r i a t e , for the results of these r e search activities h a v e b e c o m e h i g h l y r e l e v a n t to m a n y of the i m p o r t a n t u n s o l v e d p r o b l e m s e n c o u n t e r e d i n the science a n d t e c h n o l o g y of b o t h o r g a n i c coatings a n d plastics c h e m i s t r y . 1 In Interaction of Liquids at Solid Substrates; Alexander, A.; Advances in Chemistry; American Chemical Society: Washington, DC, 1968.

2

INTERACTION O F LIQUIDS A T SOLID SUBSTRATES

Some General Problems and Concepts S o l i d surface c o n s t i t u t i o n a n d surface-structure sensitive p r o p e r t i e s h a v e l o n g defied the attack of chemists, p h y s i c i s t s , m e t a l l u r g i s t s , e n g i neers, a n d biologists; the difficulties h a v e b e e n e s p e c i a l l y v e x i n g to those w h o h a v e t r i e d to u n d e r s t a n d i n f u n d a m e n t a l terms the great v a r i e t y of p h e n o m e n a o c c u r r i n g at s o l i d / l i q u i d interfaces. a n d c o m p l e x i t y e n c o u n t e r e d arose f r o m ( a )

M u c h of the c o n f u s i o n

l a c k of a d e q u a t e d e f i n i t i o n


a n d c o n t r o l of e a c h s o l i d surface i n v o l v e d a n d ( b )

l a c k of a p p r e c i a t i o n

of the necessity for the often l a b o r i o u s a n d expensive efforts r e q u i r e d to obtain liquid-phase materials h a v i n g adequate

p u r i t y to guarantee r e -

p r o d u c i b l e surface b e h a v i o r . W h y m u s t s u c h w e l l - c o n t r o l l e d m a t e r i a l s a n d the associated s p e c i a l research t e c h n i q u e s be u s e d i n s u r f a c e - c h e m i c a l research?

T h e answer

is that extreme c h e m i c a l p u r i t y a n d care i n m a n i p u l a t i n g m a t e r i a l s w h i c h are i n the interface, or are a b l e to m i g r a t e to i t , are necessary to a v o i d obtaining

incorrect,

unreproducible,

or

confusing

experimental

I n a d e q u a t e a t t e n t i o n to these r e q u i r e m e n t s are responsible, I

data.

believe,

for the a l r e a d y large mass of d a t a w h i c h b u r d e n s so m u c h of t h e o l d e r l i t e r a t u r e w i t h c o n f u s i n g or m i s l e a d i n g d a t a a n d conclusions. T h e f u n d a m e n t a l cause of these s p e c i a l r e q u i r e m e n t s arises f r o m the fact first p o i n t e d out b y L a n g m u i r (40)

that the properties of the first a d s o r b e d m o n o l a y e r

h a v e a n o v e r r i d i n g influence o n m a n y s u r f a c e - c h e m i c a l

and

surface-

p h y s i c a l p r o p e r t i e s . H i g h l y i n d i c a t i v e examples of the t r u t h of the a b o v e statement h a v e a p p e a r e d i n n u m e r o u s p u b l i c a t i o n s o n the influence of a d s o r b e d m o n o l a y e r s o n the surface a n d i n t e r f a c i a l tensions of l i q u i d s , s o l i d / s o l i d f r i c t i o n , a d h e s i o n , l i q u i d s p r e a d i n g , w e t t i n g a n d t h e contact angle, gas a d s o r p t i o n o n solids, surface viscosities, e v a p o r a t i o n - b a r r i e r films,

surface electrostatic properties of metals, electrode potentials of

metals i n electrolytes, p a s s i v a t i o n effects, h y d r o g e n overvoltage, a n d o n a host of c o l l o i d a l p h e n o m e n a .

W h e n several surface-active species of c o m -

p o u n d s are present, t h e i r c o m p e t i t i v e a d s o r p t i o n b e h a v i o r c a n b e

com-

p l e x ; f r e q u e n t l y , the d o m i n a t i n g influence arises f r o m a c o m p o u n d p r e s ent i n trace concentrations.

Experimental reproducibility, identification

of the i m p o r t a n t v a r i a b l e s , a n d a n u n d e r s t a n d i n g of the d o m i n a n t m e c h a n i s m h a v e r e s u l t e d o n l y after investigators l e a r n e d to c o n t r o l a n d i d e n t i f y t h e i r s u r f a c e - c h e m i c a l system. F o r these reasons i t is essential i n research o n the s o l i d / l i q u i d interface that there b e g o o d c o n t r o l of the c o m p o s i t i o n of the l i q u i d a n d s o l i d as w e l l as the r e a l area of the s o l i d / l i q u i d i n t e r f a c e ; i n a d d i t i o n , there is u s u a l l y n e e d for c o n t r o l l i n g the c o m p o s i t i o n , p a c k i n g , a n d o r i e n t a t i o n of the first a d s o r b e d m o n o l a y e r f o r m e d at that interface. H e l p i n c o p i n g w i t h these p r o b l e m s c a m e after W o r l d W a r I I as the result of: ( a ) the i n c r e a s e d c o m m e r c i a l a v a i l a b i l i t y of o r g a n i c c o m p o u n d s

In Interaction of Liquids at Solid Substrates; Alexander, A.; Advances in Chemistry; American Chemical Society: Washington, DC, 1968.

1.

ZISMAN

3

Solid/Liquid Interface

of h i g h p u r i t y , ( b ) i m p r o v e d d i s t i l l a t i o n a n d selective a d s o r p t i o n m e t h o d s for s m a l l v o l u m e l i q u i d samples, a n d ( c ) t h e e v o l u t i o n a n d i n c r e a s i n g a v a i l a b i l i t y of p o w e r f u l p h y s i c a l tools f o r s t u d y i n g s o l i d surfaces.

In

c o n n e c t i o n w i t h items ( a ) a n d ( b ) , t h e r a p i d e v o l u t i o n a n d c o m m e r c i a l a v a i l a b i l i t y of s o p h i s t i c a t e d g a s / l i q u i d c h r o m a t o g r a p h i c e q u i p m e n t f o r the analysis ( o r p r e p a r a t i o n ) of e x t r a o r d i n a r i l y p u r e l i q u i d s a n d gases has b e e n a great b o o n to a l l chemists.

E s p e c i a l l y i m p o r t a n t is t h e f a c t


that s u c h m e t h o d s are h i g h l y effective a n d a d a p t a b l e e v e n w h e n a p p l i e d to v e r y s m a l l q u a n t i t i e s of m a t e r i a l . I n recent years i t has b e c o m e p o s sible to o b t a i n c o m m e r c i a l l y n u m e r o u s c h e m i c a l s a l r e a d y p u r i f i e d b y c h r o m a t o g r a p h i c methods.

A s regards i t e m ( c ) , a list of t h e e s p e c i a l l y

h e l p f u l p h y s i c a l tools f o r o b s e r v i n g s o l i d surfaces s h o u l d i n c l u d e : t h e e l e c t r o n m i c r o s c o p e , t h e electron-scan m i c r o s c o p e ,

the electron diffrac-

t i o n a p p a r a t u s , t h e m u l t i p l e a t t e n u a t e d i n f r a r e d reflection ( M A I R ) spectroscope, t h e o p t i c a l ellipsometer, a n d a v a r i e t y of e x t r a o r d i n a r i l y sensit i v e r a d i o a c t i v e tracer m e t h o d s a n d t h e necessary associated e q u i p m e n t . N o t e w o r t h y progress has b e e n m a d e b y p o l y m e r chemists i n p r e p a r i n g p u r e m o n o m e r s a n d p o l y m e r s , as w e l l as s o l i d p o l y m e r s , of k n o w n surface c o n s t i t u t i o n a n d c r y s t a l structure. T h e c o n t i n u e d efforts f o r m o r e t h a n a d e c a d e b y s o l i d state physicists a n d m e t a l l u r g i s t s h a v e r e s u l t e d i n methods

a n d e q u i p m e n t f o r p r e p a r i n g a n i m p r e s s i v e v a r i e t y of e x t r a -

o r d i n a r i l y p u r e s o l i d materials f o r research o n t h e properties of metals, s e m i c o n d u c t o r s , a n d single crystals. B e c a u s e of t h e a v a i l a b i l i t y of these n e w m e t h o d s , devices, a n d p u r e r materials, i t has b e c o m e m o r e feasible to c a r r y o n effective research w i t h a d e q u a t e s u r f a c e - c h e m i c a l c o n t r o l of gas a n d l i q u i d a d s o r p t i o n , w e t t i n g , adhesion, emulsification, foaming, boundary friction, corrosion inhibition, heterogeneous catalysis, electrophoresis, electrode surface potentials, a n d a v a r i e t y of other subjects of interest i n t h e s u r f a c e - c h e m i c a l a n d a l l i e d fields

of research. I n v i e w of t h e present s i t u a t i o n , serious investigators

s h o u l d n o w b e a b l e to r e p o r t results i n t h e scientific l i t e r a t u r e w h i c h w i l l h a v e m u c h m o r e v a l u e t h a n ever before.

T h e r e is n o excuse f o r a n y

i n v e s t i g a t o r s t a k i n g s u c h i n a d e q u a t e care i n c o n t r o l l i n g surface c o m p o s i t i o n o r surface-active c o n t a m i n a n t s as w a s c o m m o n i n o v e r 5 0 % o f t h e research p u b l i c a t i o n s i n surface a n d c o l l o i d science i n t h e past. O u r o w n investigations h a v e c o n c e r n e d :

( a ) liquid spreading o n

solids a n d t h e l a w s r e l a t i n g t h e e q u i l i b r i u m contact angle a n d t h e c r i t i c a l surface tension o f w e t t i n g to s o l i d a n d l i q u i d c o n s t i t u t i o n (26, 27, 28, 53, 54,62), ( b ) l i q u i d / l i q u i d d i s p l a c e m e n t f r o m s o l i d surfaces (1,5),

(c) the

properties of a d s o r b e d m o n o l a y e r s o n solids a n d t h e i r r e l a t i o n t o t h e m o n o l a y e r r e t r a c t i o n m e t h o d (28, 54, 62), (d) t h e surface electrostatic potentials of a d s o r b e d o r g a n i c m o n o l a y e r s o n metals (9, 10, 11, 58, 59), ( e ) t h e effects of surface c o n s t i t u t i o n o n a d h e s i o n a n d a b h e s i o n


(60),

4


( f ) t h e effect of a n a d s o r b e d m o n o l a y e r o n b o u n d a r y f r i c t i o n a n d w e a r i n r u b b i n g solids (13,15, 45, 46), a n d ( g ) t h e surface c h e m i s t r y o f silicones (24, 25) a n d

fluorochemicals

(3, 4, 21, 22, 23, 34, 35, 36, 37, 51, 52).

I

b e l i e v e these studies h a v e a l l t a u g h t r e l i a b l y a n d w e l l a b o u t t h e d o m i n a t i n g influence i n surface p h e n o m e n a of t h e n e e d f o r c o n t r o l l i n g t h e c o m p o s i t i o n o f b o t h solids a n d l i q u i d s .

T h e y h a v e also r e s o l v e d m a n y

f u n d a m e n t a l a n d a p p l i e d p r o b l e m s , r e v e a l e d n e w a n d u n s u s p e c t e d sur-


face properties a n d m a t e r i a l s , a n d h e l p e d s t i m u l a t e m o r e interest i n s u r face c h e m i s t r y . A l t h o u g h m u c h has b e e n p u b l i s h e d a b o u t t h e role of w e t t i n g a n d s p r e a d i n g o f t h e l i q u i d a d h e s i v e i n f o r m i n g a n a d h e s i v e joint (17, 18, 61, 62, 63), m a n y investigators a n d users of adhesives are s t i l l n o t a w a r e of why

i t is so i m p o r t a n t , despite t h e difficulties of p r e p a r i n g joints free

f r o m i n t e r f a c i a l v o i d s (2,48). why

O u r o w n recent research has s h o w n c l e a r l y

a n d to w h a t extent s u c h v o i d s cause a significant loss of s t r e n g t h i n

c o m p o s i t e m a t e r i a l s a n d w a t e r resistance (2, 48, 63).

O n e of t h e most

p r o m i s i n g c h e m i c a l measures is t h e use of " c o u p l i n g agents," w h i c h are a class of a d h e s i o n - p r o m o t i n g agents n o w finding i n c r e a s i n g a p p l i c a t i o n s (33, 47, 56).

T h e r e is m u c h y e t to b e l e a r n e d a n d p r a c t i c e d a b o u t t h e

p r o p e r w a y to use these m a t e r i a l s (63), a n d I b e l i e v e t h e result of c u r r e n t efforts w i l l b e i l l u m i n a t i n g a n d also o f m u c h a p p l i e d v a l u e ; w e are w i t nessing t h e e v o l u t i o n of a n e w a n d i m p o r t a n t c h a p t e r i n t h e subject of the surface c h e m i s t r y of t h e s o l i d / l i q u i d interface. M a j o r effects of e x t r e m e l y t h i n films of a d s o r b e d w a t e r o n surface p h e n o m e n a o n h y d r o p h i l i c s o l i d surfaces, f o r e x a m p l e t h e great effect o n surface potentials of metals, h a v e b e e n r e c o g n i z e d f o r m a n y years (9, 10, 11,58,59);

o u r o w n recent investigations h a v e d e m o n s t r a t e d that t h e first

a d s o r b e d m o n o l a y e r of w a t e r exercises a p r o f o u n d influence o n t h e w e t t i n g a n d surface energy properties o f h i g h - e n e r g y h y d r o p h i l i c s o l i d s u r faces i n c l u d i n g glasses a n d m i n e r a l s (6, 55) a n d metals (7).

Despite the

l a r g e a m o u n t of past r e s e a r c h o n t h e surface o x i d a t i o n of metals ( 3 9 ) , a n i m p o r t a n t g a p s t i l l exists. I b e l i e v e w e n e e d to l e a r n m u c h a b o u t t h e effect o f e a c h t y p e o f m e t a l o x i d e o n t h e w e t t i n g a n d a d h e s i v e p r o p e r t i e s of metals.

W h e n a s t r e s s - i n d u c e d f a i l u r e occurs i n a n a d h e s i v e joint

i n v o l v i n g a m e t a l l i c s o l i d , t h e o b s e r v e d results m a y h a v e a r i s e n f r o m a cohesive f a i l u r e either w i t h i n t h e surface o x i d e o r w i t h i n t h e m e t a l . E i t h e r adsorbed water or water i n c l u d e d i n the oxide structure m a y p l a y an

i m p o r t a n t role i n d e t e r m i n i n g t h e cohesive

f a i l u r e of t h e oxide.

A n o t h e r p o s s i b i l i t y is that a n a d h e s i v e f a i l u r e m a y h a v e o c c u r r e d b e t w e e n the o x i d e l a y e r a n d t h e u n d e r l y i n g m e t a l . S i m i l a r p r o b l e m s exist w h e n sulfides, sulfates, n i t r i d e s , phosphates, p h o s p h i d e s , o r other i n o r g a n i c c o m p o u n d s a r e present at t h e joint interface.


1.

ZISMAN


On the Papers Presented at This

5

Symposium

T h e first three of the f o l l o w i n g papers i n this s y m p o s i u m a r c c o n c e r n e d w i t h c o u p l i n g agents.

T h e s e investigations w e r e s t i m u l a t e d b y

the r e a c t i o n of a n N R L t e a m of surface chemists to the p u b l i s h e d i n d u s t r i a l r e s e a r c h of the past d e c a d e o n glass-reinforced plastics a n d other c o m p o s i t e m a t e r i a l s . Present c o m m e r c i a l practices s t i l l a p p e a r to i n v o l v e m o r e art t h a n science (63),

a n d these papers g i v e a d e q u a t e e v i d e n c e t h a t


there are o p p o r t u n i t i e s for b o t h b a s i c a n d a p p l i e d r e s e a r c h o n the subject. C r a v e r a n d T a y l o r s (16)

c o n t r i b u t i o n is i m p o r t a n t to the subject of

solvent interactions w i t h p o l y m e r i c solids; i t is e s p e c i a l l y t h o u g h t p r o v o k i n g t h a t this w o r k m a y h a v e o p e n e d a n e w avenue of a p p r o a c h o n the subject of t h e m e c h a n i s m of p l a s t i c i z a t i o n . S c h i c k a n d H a r v e y (49)

s u m m a r i z e a n i n t e r e s t i n g i n v e s t i g a t i o n of

the effect of the c h o i c e of solvent o n the c o n f o r m a t i o n of a p o l y m e r a d s o r b e d at the s o l u t i o n interface w i t h S p h e r o n 6 c a r b o n b l a c k . A notew o r t h y c o n c l u s i o n concerns the o c c u r r e n c e of e x t e n d e d a n d l o o p e d c o n figurations

o f the a d s o r b e d p o l y m e r m o l e c u l e s f o r m e d f r o m g o o d or p o o r

solvents, r e s p e c t i v e l y . M a n y i m p o r t a n t i n d u s t r i a l processes f o r p l a s t i c p r o d u c t s n o w d e p e n d o n some f o r m of surface o x i d a t i o n to c h a n g e the s u r f a c e - c h e m i c a l c o m p o s i t i o n o f o r g a n i c plastics d e s i g n e d for use as coatings or t h i n foils. M o r e d e f i n i t i v e p u b l i s h e d i n f o r m a t i o n has b e e n n e e d e d a b o u t t h e surfacec h e m i c a l processes i n v o l v e d , the effective m e t h o d s for m o d i f y i n g or c o n t r o l l i n g the surface properties of the o r g a n i c p o l y m e r , a n d the extent to w h i c h surface o x i d a t i o n causes the d e t e r i o r a t i o n of u s e f u l p r o p e r t i e s . T h e w o r k of F o x , P r i c e , a n d C a i n

(29)

is a v a l u a b l e c o n t r i b u t i o n to

a n s w e r i n g a l l three questions. T h e i r p a p e r reports a n effective

surface-

c h e m i c a l i n v e s t i g a t i o n of the p h o t o c h e m i c a l changes i n the surface of a well-defined organic polymer.

It m a y s u r p r i s e m a n y chemists to r e a l i z e

that, despite the s u s t a i n e d a n d often large research effort i n p h o t o c h e m i s t r y d u r i n g the past 30 years, little has b e e n d o n e o n the p h o t o c h e m i s t r y of the s o l i d / g a s i n t e r f a c e ; o b v i o u s l y , m u c h m o r e a t t e n t i o n needs to b e d i r e c t e d to this i m p o r t a n t subject. T h e s i m u l t a n e o u s use b y these authors of p o l y m e r c h e m i s t r y , the r e l a t i o n of the contact angle to surface c o n s t i t u t i o n , a n d m u l t i p l e a t t e n u a t e d i n t e r n a l reflection ( M A I R )

spectroscopy

i n the i n f r a r e d is a n i m p r e s s i v e d e m o n s t r a t i o n of the p o w e r of i n t e r d i s c i p l i n a r y research. Lee

(41, 42)

offers a v a l u a b l e c o n t r i b u t i o n o n the m e c h a n i s m of

r e i n f o r c e m e n t a n d e s p e c i a l l y o n the r o l e of a d h e s i o n a n d w e t t i n g i n elastomeric adhesives, pressure-sensitive tapes, n o n p i g m e n t e d

organic

coatings, a n d composites

thermo-

s u c h as r e s i n - r e i n f o r c e d r u b b e r s or

plastics. I a m sure i t w i l l generate m u c h discussion. L e e (43)

presents a


6


s e m i q u a n t i t a t i v e treatment of

the r e l a t i o n s h i p b e t w e e n

the

cohesive

energy d e n s i t y , the s o l i d surface tension, the c r i t i c a l surface tension of w e t t i n g , a n d the glass t e m p e r a t u r e of a h i g h p o l y m e r .

T h i s p a p e r is

b y n o means rigorous or q u a n t i t a t i v e , b u t it is nevertheless i n t e r e s t i n g and imaginative. B e r t o l u c c i , Jantzef, a n d C h a m b e r l a i n (8)

report briefly on their

w o r k u s i n g single-reflection, a t t e n u a t e d , total-reflection, i n f r a r e d specDownloaded by UNIV OF NOTRE DAME on November 17, 2014 | http://pubs.acs.org Publication Date: June 1, 1968 | doi: 10.1021/ba-1968-0087.ch001

t r o s c o p y to s t u d y the m e c h a n i s m of a d s o r p t i o n o n h y d r o x y - a p a t i t e crystals of c i t r i c a c i d , t a r t a r i c a c i d , s o d i u m c i t r a t e , o x y t e t r a c y c l i n e h y d r o c h l o r i d e , a n d g l y c i n e . T h i s w o r k has b e e n of interest to m a n y chemists, b u t i t also has p a r t i c u l a r p e r t i n e n c y to c u r r e n t research o n d e n t a l adhesives

and

the effect of p r e t r e a t m e n t of the t o o t h c a v i t y w a l l . A l t h o u g h e a r l y surface chemists gave m u c h a t t e n t i o n to t h e s p r e a d i n g a n d a d s o r p t i o n of m o n o l a y e r s o n l i q u i d m e r c u r y , except for the b e a r i n g the results h a d o n l a t e r research c o n c e r n i n g p o l a r o g r a p h y , r e l a t i v e l y little a t t e n t i o n has b e e n g i v e n to the subject o n the past 30 years. T h i s is s u r p r i s i n g i n v i e w of the s t i m u l a t i n g a n d i m p o r t a n t investigations e a r l y i n this c e n t u r y b y H e n r i D e x a u x (19, 20).

A l s o , let m e r e c a l l t h e e a r l y

w o r k of W . D . H a r k i n s a n d c o - w o r k e r s (30, 31, 32)

w h o m e a s u r e d the

s p r e a d i n g coefficient a n d w o r k of a d h e s i o n of the large v a r i e t y of pounds

a b l e to s p r e a d spontaneously

m e r c u r y to f o r m m o n o m o l e c u l a r K l e m m , and Otto (57)

films.

o n the surface of c l e a n

comliquid

T h e report b y Schwartz, Ellison,

o n the w a t e r w e t t a b i l i t y of c o n d e n s e d a d s o r b e d

films of fatty acids o n m e r c u r y is a n i n t e r e s t i n g a n d v a l u a b l e c o n t r i b u t i o n . Schonhorn and R y a n (50)

discuss t h e results of recent w o r k w h i c h

is a l o g i c a l extension of t h e i r e a r l i e r i n v e s t i g a t i o n o n the effect of the morphology strength.

of the surface r e g i o n of

a p l a s t i c o n its a d h e s i v e

joint

I n effect, t h e y p o i n t o u t h o w i n c r e a s i n g p o l y m e r e r y s t a l l i n i t y

i n the v i c i n i t y of the free surface c a n increase its a b i l i t y to f o r m stronger joints b y i n c r e a s i n g its l o c a l cohesive strength. T h e i r results are of m u c h interest, a l t h o u g h t h e y are not s u r p r i s i n g . O v e r t e n years ago

Bowers,

C l i n t o n , a n d I i n a n i n v e s t i g a t i o n o n the f r i c t i o n a l properties of ethylene a n d its h a l o g e n a t e d d e r i v a t i v e s (14)

found that the

poly-

surface

regions of s u c h plastics, as n o r m a l l y p r o d u c e d , w e r e so a m o r p h o u s as to e x h i b i t greater b o u n d a r y f r i c t i o n a n d therefore greater t e n d e n c y to f a i l c o h e s i v e l y t h a n the regions just beneath.

S i n c e f r i c t i o n research

has

p r o v e d t h a t a g o o d joint u s u a l l y fails b y a cohesive f a i l u r e i n the w e a k e r m a t e r i a l (13),

a n a m o r p h o u s surface s t r u c t u r e gives a p l a s t i c a l o w e r

a d h e s i v e joint strength. B i k e r m a n (12) considers

gives a d e r i v a t i o n of a n e q u a t i o n w h i c h the a u t h o r

t h e o r e t i c a l l y m o r e s o u n d t h a n the w e l l - k n o w n e q u a t i o n


of

1.

ZISMAN


7

T h o m a s Y o u n g f o r the contact a n g l e o f a l i q u i d w i t h a s o l i d . T h e d e r i v a t i o n a n d r e l i a b i l i t y o f t h e Y o u n g e q u a t i o n has b e e n e s p e c i a l l y w e l l d i s cussed i n recent years (38, 44). A l t h o u g h I d o n o t b e l i e v e B i k e r m a n ' s n e w t r e a t m e n t is s o u n d , i t is a n i n t e r e s t i n g a p p r o a c h nevertheless. Y o u n g a n d R o u c h (60) r e p o r t o n progress i n i n v e s t i g a t i n g the p o t e n tialities o f a t i t a n i u m o r g a n i c c o m p o u n d d e s i g n e d t o react w i t h E - g l a s s a n d s i l i c a b y a c h e l a t i n g m e c h a n i s m a n d so f o r m a n e w t y p e o f c o u p l i n g Downloaded by UNIV OF NOTRE DAME on November 17, 2014 | http://pubs.acs.org Publication Date: June 1, 1968 | doi: 10.1021/ba-1968-0087.ch001

agent.

T h e i r w o r k is o r i g i n a l a n d p r o m i s i n g , a n d i t w i l l attract m u c h

attention. Conclusion I n c l o s i n g , I b e l i e v e i t deserves emphasis that a n y n e w c o n t r i b u t i o n c o n c e r n i n g n e w surface p h e n o m e n a o r a n y n e w m e c h a n i s m o p e r a t i n g a t the s o l i d / l i q u i d interface has a h i g h p r o b a b i l i t y o f e v o k i n g a w i d e r r a n g e of interest t h a n e v e n t h e a u t h o r m a y r e a l i z e . A s u r f a c e - c h e m i c a l m e c h a n i s m o c c u r r i n g a t o n e t y p e o f s o l i d / l i q u i d interface m a y r e a p p e a r a g a i n a n d a g a i n i n u n o b v i o u s b u t nevertheless r e l a t e d p h e n o m e n a o r processes of interest t o m a n k i n d . F o r e x a m p l e , a m o r e d e t a i l e d m e c h a n i s t i c u n d e r s t a n d i n g o f t h e r o l e o f c o u p l i n g agent i n g l a s s / r e s i n - r e i n f o r c e d plastics c a n c o n t r i b u t e g u i d a n c e t o h e l p m a k e a m a j o r a d v a n c e i n another

field.

E x a m p l e s a r e possible uses i n d e n t a l a d h e s i v e restorative materials, i n i m p r o v i n g r u b b e r tires, i n i n c r e a s i n g t h e w a t e r resistance a n d a d h e s i o n of p a i n t s , i n b i o l o g i c a l adhesives, a n d i n i m p r o v i n g t h e properties o f p l a s t i c foils a n d laminates f o r p a c k a g i n g o r other uses.

Literature Cited (1) Baker, H. R., Leach, P. B., Singleterry, C. R., Zisman, W. Α., Ind. Eng. Chem. 59, 29 (1967). (2) Bascom, W. D., Romans, J. B., Proc. Soc. Plastics Ind., Div. Reinforced Plastics, Chicago,Ill.,Feb. 1965 (to be published). (3) Bernett, M. K., Zisman, W. Α., J. Phys. Chem. 65, 448 (1961). (4) Ibid., 66, 328 (1962). (5) Ibid., 70, 1064 (1966). (6) Bernett, M. K., Zisman, W. Α., J. Colloid Interface Sci. (to be published). (7) Bernett, M. K., Zisman, W. Α., J. Colloid Interface Sci. (to be published). (8) Bertolucci, Michael, Jantzef, Fern, Chamberlain, David L., Jr., ADVAN. CHEM. SER. 87, ??? (1968). (9) Bewig, K. W., Zisman, W. Α., ADVAN. CHEM. SER. 33, 100 (1961).

(10) Bewig, K. W., Zisman, W. Α., J. Phys. Chem. 67, 130 (1963). (11) Ibid., 68, 1804 (1964). (12) Bikerman, J. J., "Abstracts of Papers," 154th Meeting, ACS, Sept. 1967, TO14.

(13) Bowden, F. P., Tabor, D., "Friction and Lubrication of Solids," Oxford Press, London, 1950. In Interaction of Liquids at Solid Substrates; Alexander, A.; Advances in Chemistry; American Chemical Society: Washington, DC, 1968.


8


(14) Bowers, R.C.,Clinton, W. C., Zisman, W. Α., Modern Plastics 31, 131 (1954). (15) Cottington, R., Shafrin, E .G.,Zisman, W. Α., J. Phys. Chem. 62, 513 (1958). (16) Craver, J. K., Taylor, D. L., ADVAN. CHEM. SER. 87, 154 (1968). (17) DeBruyne, Ν. Α., Research (London) 6, 362 (1953). (18) DeBruyne, Ν. Α., Nature 180, 262 (1957). (19) Devaux, H., Bull. des Séances de la Societé Francaise de Physique, No. 182 (1923). (20) Devaux, H., Kolloid-Zeitschr. LVIII, 9 (1932). (21) Ellison, A. H., Fox, H. W., Zisman, W. Α., J. Phys. Chem. 57, 622 (1953). (22) Ellison, A. H., Zisman, W. Α., J. Phys. Chem. 59, 1233 (1955). (23) Ibid., 60, 416 (1956). (24) Fox, H. W., Taylor, P., Zisman, W. Α., Ind. Eng. Chem. 39, 1401 (1947). (25) Fox, H. W., Solomon, E., Zisman, W. Α., J. Phys. Colloid Chem. 54, 723 (1950). (26) Fox, H. W., Zisman, W. Α., J. Colloid Sci. 5, 514 (1950). (27) Ibid., 7, 109 (1952). (28) Fox, H. W., Hare, E. F., Zisman, W. Α., J. ColloidSci. 8, 194 (1953). (29) Fox, R. B., Price, T. R., Cain, D. Sandra, ADVAN. CHEM. SER. 87, 72 (1968). (30) Harkins, W. D., Grafton, E. H., J. Am. Chem. Soc. 42, 2534 (1920). (31) Harkins, W. D., Ewing, W. W., J. Am. Chem. Soc. 42, 2539 (1920). (32) Harkins, W. D., "Physical Chemistry of Surfaces," p. 102, Reinhold Publ. Co., New York City, 1952. (33) Hauserman, F. B., ADVAN. C H E M . SER. 23, 338 (1959).

(34) (35) (36) (37)

Jarvis, N. L., Zisman, W. Α., J. Phys. Chem. 63, 727 (1959). Ibid., 64, 150 (1960). Ibid., 64, 157 (1960). Jarvis, N. L., Zisman, W. Α., Encyclopedia of Chemical Technology 9, 707, John Wiley & Sons, Inc., New York, 1966. (38) Johnson, R. E., J. Phys. Chem. 63, 1655 (1959). (39) Kubaschewski, O., Hopkins, Β. E., "Oxidation of Metals and Alloys," Butterworth & Co., Ltd., London, 1962. (40) Langmuir, I., "Collected Works," Pergamon Press, Ltd., London, 1960. (41)

Lee, L. H., ADVAN. C H E M . SER. 87, 85 (1968).

(42) Ibid., 87, 106 (1968). (43) Lee, L. H., "Abstracts of Papers," 154th Meeting, ACS, Sept. 1967, T009. (44) Lester, G. R., J. Colloid Sci. 16, 315 (1961). (45) Levine, O., Zisman, W. Α., J. Phys. Chem. 61, 1068 (1957). (46) Ibid., 61, 1188 (1957). (47) Plueddemann, E. P., Clark, Η. Α., Nelson, L. E., Hoffman, K. R., Modern Plastics 39, 135 (Aug. 1962). (48) Sands, A.G.,Clark, R. C., Kohn, E. J., NRL Report 6498, March 31, 1967, Washington, D. C. (to be published). (49) Schick, M. J., Harvey, Ε. N., Jr., ADVAN. CHEM. SER. 87, 63 (1968). (50) Schonhorn, H., Ryan, F. W., ADVAN. CHEM. SER. 87, 140 (1968). (51) Schulman, F., Zisman, W. Α., J. Colloid Sci. 7, 465 (1952). (52) Schulman, F., Zisman, W. Α., J. Am. Chem. Soc. 74, 2123 (1952). (53) Shafrin, E. G., Zisman, W. Α., J. Colloid Sci. 7, 166 (1952). (54) Shafrin, E.G.,Zisman, W. Α., J. Phys. Chem. 64, 519 (1960). (55) Shafrin, E. G., Zisman, W. Α., J. Am. Ceramic Soc. 50, 478 (1967). (56) Sterman, S., Marsden, J., Ind. Eng. Chem. 58, 33 (1966). (57) Schwartz, A. M., Ellison, A. H., Klemm, R. B., Otto, E. W., ADVAN. C H E M . SER. 87, 133 (1968).


1.

ZISMAN


9

(58) Timmons, C. O., Zisman, W. Α., J. Phys. Chem. 68, 1336 (1964). (59) Ibid., 69, 984 (1965). (60) Young, F. M., Rouch, L. L., "Abstracts of Papers," 154th Meeting, ACS, Sept. 1967, T005. (61) Zisman, W. Α., Ind. Eng. Chem. 55, 18 (1963). (62)

Zisman, W. A., ADVAN. C H E M . SER. 43, 1 (1964).

(63) Zisman, W. Α., Ind. Eng. Chem. 57, 26 (1965). 1967.


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