Surfactant Interactions in Polyvinyl Acetate and Poly (vinyl acetate

13 Surfactant Interactions in Polyvinyl Acetate and Poly (vinyl acetate-butyl acrylate) Latexes

Downloaded by PURDUE UNIVERSITY on June 13, 2013 | http://pubs.acs.org Publication Date: October 7, 1981 | doi: 10.1021/bk-1981-0165.ch013

B. R. VIJAYENDRAN, T. BONE, and C. GAJRIA Celanese Plastics and Specialties Company, Jeffersontown, KY 40299

Recent investigations have shown that the behavior and interactions of surfactants in a polyvinyl acetate latex are quite different and complex compared to that in a polystyrene latex (1, 2). Surfactant adsorption at the fairly polar vinyl acetate latex surface is generally weak (3,4) and at times shows a complex adsorption isotherm (2). Earlier work (5,6) has also shown that anionic surfactants adsorb on polyvinyl acetate, then slowly penetrate into the particle leading to the formation of a polyelectroyte type solubilized polymer-surfactant complex. Such a solubilization process is generally accompanied by an increase in viscosity. The first objective of this work is to better understand the effects of type and structure of surfactants on the solubilization phenomena in vinyl acetate and vinyl acetate-butyl acrylate copolymer latexes. It was reported earlier (1) that surfactant adsorption at a polymer/water interface can be related to the polarity of the polymer surface. The model used in that study was tested satisfactorily by using the available literature data on polymer polarity and sodium lauryl sulfate adsorption on latex surfaces. The second objective is to verify experimentally the predicted relationship between polymer polarity and surfactant adsorption by studying the adsorption of a non-ionic surfactant that shows a saturation type isotherm behavior on vinyl acrylic latexes of varying polarity. In order to achieve the above objectives, three vinyl acrylic latexes of varying butyl acrylate content have been prepared and 'cleaned' for use in the study. Several anionic and nonionic surfactants commonly used in emulsion polymerization have been used to investigate the effects of surfactant structure and polymer composition on the solubilization process. Polarity of latex surface estimated from contact angle measurements have been used to study the effect of polymer polarity on surfactant adsorption.

0097-6156/81/0165-0225$O5.0O/0 © 1981 American Chemical Society

In Emulsion Polymers and Emulsion Polymerization; Bassett, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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Experimental Section Materials; C o m m e r c i a l g r a d e v i n y l a c e t a t e (VA) and b u t y l a c r y l a t e (BA) f r o m C e l a n e s e C h e m i c a l Company were u s e d . Reagent g r a d e p o t a s s i u m p e r s u l f a t e was u s e d as t h e i n i t i a t o r . Sodium l a u r y l s u l f a t e (NaLS) f r o m BDH C h e m i c a l s a f t e r p u r i f i c a t i o n (7) was u s e d as t h e e m u l s i f i e r i n t h e p o l y m e r i z a t i o n . S u r f a c t a n t s u s e d i n t h e a d s o r p t i o n s t u d i e s were t h e f o l l o w i n g : I g e p a l CO-630 QLQ m o l e e t h y l e n e o x i d e a d d u c t o f n o n y l p h e n o l ) and A l i p a l EP-110 and EP-120 f r o m GAF C o r p o r a t i o n ; A e r o s o l A-102 f r o m A m e r i c a n Cyanamid and BDH C h e m i c a l s o l i u m l a u r y l s u l f a t e . According to the m a n u f a c t u r e r ' s l i t e r a t u r e , A l i p a l E P - 1 1 0 and EP-120 a r e ammonium s a l t s o f a s u l f a t e d n o n y l phenoxy p o l y ( e t h y l e n e o x y ) e t h a n o l o f m o l e c u l a r w e i g h t s 708 and 1640 r e s p e c t i v e l y . A e r o s o l A-102 i s an a n i o n i c / n o n - i o n i c type s u r f a c t a n t o f the composition disodium e t h o x y l a t e d a l c o h o l ( C l O - C12) h a l f e s t e r o f s u l f o - s u c c i n i c a c i d o f m o l e c u l a r w e i g h t o f about 1800. Emulsion P o l y m e r i z a t i o n : A t y p i c a l r e c i p e i s give i n Table I . E m u l s i o n p o l y m e r i z a t i o n was c a r r i e d o u t a t 60°C u n d e r a n i t r ogen a t m o s p h e r e u s i n g a b a t c h p r o c e s s . T h e o r e t i c a l s o l i d s c o n t e n t i n a l l t h e f o r m u l a t i o n s was 2 5 % , and g e n e r a l l y t h e c o n v e r s i o n s were b e t t e r t h a n 9 8 % . A p o l y v i n y l a c e t a t e homopolymer and two p o l y ( v i n y l a c e t a t e - b u t y l a c r y l a t e ) c o p o l y m e r s h a v i n g VA/ΒΑ comp o s i t i o n o f 85/15 and 70/30 w e r e p r e p a r e d a c c o r d i n g t o t h e above procedure. I o n E x c h a n g e and D i a l y s i s o f L a t e x e s : The above t h r e e l a t e x e s were ' c l e a n e d b y t h e i o n e x c h a n g e method o f V a n d e r h o f f (8) and d i a l y s i s . I n g e n e r a l , t h e l a t e x e s were s t a b l e a f t e r t h e c l e aning process. I n some c a s e s , t h e i o n - e x c h a n g e r e s i n was f o u n d t o d i s c o l o r a f t e r t h e t r e a t m e n t i n d i c a t i n g some i n t e r a c t i o n , p e r haps h y d r o l y s i s o f t h e l a t e x , b e t w e e n t h e l a t e x and i o n - e x c h a n g e resin. 1

P a r t i c l e - S i z e Determination: P a r t i c l e - s i z e o f the 'cleaned' l a t e x e s were d e t e r m i n e d u s i n g t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y a f t e r f r e e z e - d r y i n g t h e s a m p l e s and c o u n t i n g t h e p a r t i c l e s w i t h a Q u a n t i m e t image a n a l y z e r . The number a v e r a g e p a r t i c l e d i a m e t e r s ( n ) o f t h e homopolymer, t h e 85/15 VA/ΒΑ and 70/30 VA/ΒΑ l a t e x e s were f o u n d t o be 0.Q57 um, 0 . 0 6 2 / c m and 0.073 ^m, r e s p e c t i v e l y . The p o l y d i s p e r s i t y o f t h e t h r e e s a m p l e s were 1.09, 1.05 and 1.06, r e s p e c t i v e l y . d

/

A d s o r p t i o n S t u d i e s : A p p r o p r i a t e amounts o f c l e a n e d l a t e x and s u r f a c t a n t s were m i x e d , e q u i l i b r a t e d f o r 24 h o u r s and t h e e x c e s s s u r f a c t a n t i n serum a n a l y z e d a f t e r s e p a r a t i o n b y c e n t r i f u g a tion. I g e p a l CO-630 and A l i p a l s u r f a c t a n t s were a n a l y z e d b y c o l o r i m e t r i c t i t r a t i o n with cetyltrimethylammonium c h l o r i d e i n t h e p r e s e n c e o f m e t h y l e n e b l u e and a c h l o r o f o r m l a y e r s i m i l a r t o t h e method o f E p t o n ( 9 ) . Some n o n - i o n i c s u r f a c t a n t s and s o l u b i l -


13.

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in Latexes

i z e d serum components were f o u n d t o h a v e a p o s i t i v e i n t e r f e r e n c e i n the c o l o r i m e t r i c a n a l y s i s o f i o n i c s u r f a c t a n t s . C o n t a c t A n g l e M e a s u r e m e n t s and P o l a r i t y o f L a t e x F i l m s : A d v a n c i n g c o n t a c t a n g l e m e a s u r e m e n t s were made a t 250C u s i n g a Rame H a r t c o n t a c t a n g l e g o n i o m e t e r . Latexes 'cleaned b y the above p r o c e d u r e were drawn o n a g l a s s p l a t e and d r i e d a t 40°C. An a v e r a g e o f e i g h t measurements was t a k e n a s t h e c o n t a c t a n g l e . W a t e r and m e t h y l e n e i o d i d e were u s e d a s t e s t l i q u i d s . Polarity o f t h e d r i e d l a t e x f i l m s were e s t i m a t e d a c c o r d i n g t o t h e m e t h o d of Kaelble (10). f

1


R e s u l t s and

Discussion

Shape o f A d s o r p t i o n I s o t h e r m s and L a t e x T h i c k e n i n g : A d s o r p t i o n i s o t h e r m s o f N a L S and A e r o s o l A-102 s u r f a c t a n t s on a c l e a n ' 85/15 VA/ΒΑ c o p o l y m e r l a t e x a r e shown i n F i g u r e 1. I t i s s e e n t h a t t h e s h a p e s o f t h e two i s o t h e r m s a r e q u i t e d i f f e r e n t . A-102 seems t o e x h i b i t a L a n g m u i r t y p e s a t u r a t i o n a d s o r p t i o n be h a v i o r t y p i c a l o f s u r f a c t a n t adsorption at a polystyrene/water interface. NaLS seems t o h a v e a more c o m p l e x a d s o r p t i o n i s o t h e r m , perhaps i n v o l v i n g a m u l t i p l e step process as d i s c u s s e d b y G i l e s e t a l (11). The i n i t i a l r e g i o n o f the i s o t h e r m upto Β appears t o be n o r m a l and b e y o n d t h a t t h e i s o t h e r m become l i n e a r . G i l e s et a l h a v e e x p l a i n e d s u c h a l i n e a r i s o t h e r m ( c l a s s i f i e d a s Type C) b y p e n e t r a t i o n o f s u b s t r a t e b y s o l u t e , l e a d i n g t o new a d s o r p t i o n sites. Compared t o NaLS, t h e s i z e o f A e r o s o l A-102 m o l e c u l e i s much l a r g e r and b u l k i e r and t h u s p e r h a p s h i n d e r e d i n b e i n g a b l e to penetrate i n t o the l a t e x p a r t i c l e . 1

F i g u r e 2 shows a d s o r p t i o n i s o t h e r m s o f two s u l f a t e d e t h o x y l a t e t y p e a n i o n i c s - A l i p a l EP-110 and A l i p a l EP-120 - o n t h e 85/15 VA/ΒΑ l a t e x s u r f a c e . A g a i n i t i s s o e n t h a t t h e l o w e r m o l e c u l a r w e i g h t EP-110 shows a C t y p e i s o t h e r m s i m i l a r t o NaLS w h i l e t h e h i g h e r m o l e c u l a r w e i g h t EP-120 e x h i b i t s a n o r m a l s a t u r a t i o n type isotherm. I t i s w e l l known (3,5,6) t h a t s o d i u m l a u r y l s u l f a t e i n t e r a c t s w i t h some p o l y m e r s s u c h a s p o l y v i n y l a c e t a t e c a u s i n g s o l u b i l i z a t i o n o f the i n s o l u b l e polymer l e a d i n g t o an i n c r e a s e i n v i s c o sity. I n F i g u r e 3, v i s c o s i t y o f t h e homopolymer and 70/30 VA/BA a t v a r i o u s N a L S / p o l y m e r r a t i o i s shown. I t i s s e e n t h a t t h e v i s c o s i t y o f t h e 2% l a t e x d i s p e r s i o n i n c r e a s e s w i t h i n c r e a s e i n NaLS/polymer r a t i o . S i m i l a r v i s c o s i t y d a t a f o r t h e 85/15 VA/BA was i n t e r m e d i a t e b e t w e e n t h e homopolymer and 70/30 VA/BA l a t e x e s . S u r f a c t a n t s t h a t showed a n o r m a l s a t u r a t i o n t y p e a d s o r p t i o n be h a v i o r d i d n o t show any s i g n i f i c a n t v i s c o s i t y i n c r e a s e o f t h e latex. E d e l h a u s e r (3) has e x p l a i n e d h i s r e s u l t s on t h e i n t e r a c t i o n o f a n i o n i c s u r f a c t a n t s ( s o d i u m l a u r y l s u l f a t e and s o d i u m d o d e c y l b e n z e n e s u l f o n a t e ) w i t h a PVAC l a t e x a s a t w o - s t e p mechanism i n v o l v i n g surface adsorption followed by s u r f a c t a n t penetration i n t o



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0

50

100

150

200

SURFACTANT CONCENTRATION MOLES/LTTRE x 1 0

4

Journal of Applied Polymer Science

Figure 1. Adsorption isotherms of NaLS and Aerosol A-102 surfactants at 85/15 VA/BA latex/water interface (11) ((O) sodium lauryl sulfate; (A) Aerosol A-102)

100

0

0.2

0.4

0.6

0.8

1.0

SURFACTANT CONCENTRATION GRAMS/UTRE

Journal of Applied Polymer Science

Figure 2. Adsorption isotherms of Alipal EP-110 and Alipal EP-120 surfactants at 85/15 VA/BA latex/water interface (11) ( Y | j Alipal EP-110; (A) Alipal EP120)



viJAYENDRAN

Figure 3.

ET AL.

Surfactant Interactions

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Thickening of vinyl acrylic latexes in the presence of NaLS (11) ((O) PVAC homopolymer; (A) 70/30 VA/BA copolymer)


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TABLE I


EMULSION P0LYrF9I7.ATI0f! RECIPE

(Π)

MONOMERS

500 GRAMS

SURFACTANT NALS

17.1 GRAMS

K

2

S

2

Og

2.48 GRAMS

DISTILLED WATER

1575 GRAMS

SOLIDS

25! Journal of Applied Polymer Science

TABLE II

ANIONIC SURFACTANTS STUDIED IN (Π)

VINYL ACRYLIC LATEXES

NON PENETRATING TYPE

PENETRATING TYPE (A)

(A)

SODIUM LAURYL SULFATE C

H

12 25

S 0

4

N

A

M

Surfactant Interactions in Polyvinyl Acetate and Poly (vinyl acetate

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