The Effects of Hostile Environments on Coatings and Plastics

5 New Styrene-Maleic Anhydride Terpolymer Blends W. J. HALL, R. L. KRUSE, R. A. MENDELSON, and Q. A. TREMENTOZZI

Downloaded by CORNELL UNIV on October 24, 2016 | http://pubs.acs.org Publication Date: September 29, 1983 | doi: 10.1021/bk-1983-0229.ch005

Monsanto Company, Indian Orchard, MA 01151

A group of new, fully miscible, polymer blends consisting of various styrene-maleic anhydride terpolymers blended with styrene-acrylonitrile copolymer and rubber-modified versions of these materials have been prepared and investigated. In particular the effects of chemical composition of the components on heat resistance and the miscibility behavior of the blends have been elucidated. Toughness and response to elevated temperature air aging are also examined. Appropriate combinations of the components may be melt blended to provide an enhanced balance of heat resistance, chemical resistance, and toughness. Engineering p l a s t i c s are g e n e r a l l y developed to provide appropriate property response to i n c r e a s i n g l y severe environmental c o n d i t i o n s ; e.g., heat, s t r e s s a t temperature extremes, and chemicals. A number o f such polymers have been introduced i n recent y e a r s , each with i t s own balance o f p r o p e r t y advantages and disadvantages. Simultaneously, research on polymer c o m p a t i b i l i t y has s i g n i f i c a n t l y increased the number o f known completely m i s c i b l e polymer p a i r s (I), which g e n e r a l l y show approximate a d d i t i v i t y o f many p r o p e r t i e s as a f u n c t i o n o f component r a t i o . This c h a r a c t e r i s t i c can, i n p r i n c i p l e , be used to create a f a m i l y o f m a t e r i a l s with optimized property combinations, among which are those p r o p e r t i e s which q u a l i f y such polymer blends as engineering p l a s t i c s . This paper d i s c u s s e s a group o f new f u l l y m i s c i b l e polymer p a i r s c o n s i s t i n g o f v a r i o u s styrene-maleic anhydride random terpolymers (S/MA/X) and s t y r e n e - a c r y l o n i t r i l e random copolymer (SAN) and rubber modified v e r s i o n s of these p a i r s . Appropriate combinations can provide an enhanced balance o f heat r e s i s t a n c e , chemical r e s i s t a n c e , and toughness. The termonomers i n S/MA/X to be d i s c u s s e d are a c r y l o n i t r i l e (S/MA/AN), e t h y l a c r y l a t e (S/MA/ETA), i s o b u t y l e n e (S/MA/IB), methyl a c r y l a t e (S/MA/MEA), and methyl methacrylate

0097-6156/ 83/0229-0049506.00/0 © 1983 American Chemical Society Garner and Stahl; The Effects of Hostile Environments on Coatings and Plastics ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

EFFECTS OF HOSTILE ENVIRONMENTS

50

(S/MA/MM). M i s c i b i l i t y behavior of t y p i c a l matrix p a i r s i s discussed as a f u n c t i o n of composition, and d i s c u s s i o n of m a t e r i a l behavior i n t h i s work emphasizes response to elevated temperatures and to s t r e s s at temperature extremes. Thus, g l a s s t r a n s i t i o n temperature (Tg), d i s t o r t i o n temperature under load (DTUL), and t e n s i l e deformation p r o p e r t i e s as a f u n c t i o n of temperature are reported f o r v a r i o u s t y p i c a l blend combinations. A l s o discussed are the r e s u l t s of elevated temperature a i r aging s t u d i e s on a t y p i c a l blend compared to ABS.


Experimental The v a r i o u s copolymer and terpolymer samples, with or without g r a f t e d polybutadiene rubber, were produced by conventional f r e e r a d i c a l p o l y m e r i z a t i o n s . Blending was performed using one of s e v e r a l methods: Brabender small s c a l e mixing bowl, Brabender 3/4 extruder, large s c a l e Banbury i n t e n s i v e mixer or l a r g e s c a l e extruder, depending on the s c a l e of the experiment d e s i r e d . In the work discussed here no e f f e c t of b l e n d i n g s c a l e was observed. Tg's reported here were measured by d i f f e r e n t i a l scanning c a l o r i m e t r y (DSC), using a DuPont 990 Thermal A n a l y z e r , at 20°C/min. h e a t i n g rate and t a k i n g the onset value as Tg. DTUL measurements were performed according to ANSI/ASTM D648 with 1.82 MPa maximum f i b e r s t r e s s l o a d i n g on unannealed specimens with dimensions given a p p r o p r i a t e l y i n the R e s u l t s and D i s c u s s i o n s e c t i o n . T e n s i l e deformation measurements were performed at v a r i o u s temperatures according to ANSI/ASTM D638 on i n j e c t i o n molded Type I (12.7 χ 3.2 χ 57 mm gauge dimensions) specimens, using an I n s t r o n U n i v e r s a l T e s t e r and Instron constant temperature chamber (the l a t t e r f o r a l l temperatures other than room temperature (R.T. = 23°C)). T e n s i l e t e s t i n g speed was 5.08 mm/min. (0.2 in./min.) g r i p s e p a r a t i o n rate i n a l l cases. Izod impact t e s t i n g was performed according to ASTM D256 on 12.7 χ 3.2 χ 63 mm specimens, i n j e c t i o n molded i n the case of the aging study and compression molded i n the cases given i n Table I. Specimens were notched to a depth of 2.5 mm with a root radius of 0.25 mm. ff

The elevated temperature aging study was performed on i n j e c t i o n molded t e n s i l e , Izod, and DTUL specimens (dimensions given above) which were maintained i n a c i r c u l a t i n g a i r oven at an a c c u r a t e l y c o n t r o l l e d 90°C f o r p e r i o d s of time up to two months. When removed from the a i r oven, these specimens were conditioned at 23°C and 50% R.H. f o r at l e a s t 24 hours before t e s t i n g . Notching of the Izod bars was performed on conditioned specimens. R e s u l t s and D i s c u s s i o n Of major importance i n the development of most engineering p l a s t i c s i s the r e t e n t i o n of r i g i d i t y to as high a use

Garner and Stahl; The Effects of Hostile Environments on Coatings and Plastics ACS Symposium Series; American Chemical Society: Washington, DC, 1983.


5.

H A L L ET AL.

Styrene-Maleic Anhydride Terpolymer Blends

51

temperature as i s p o s s i b l e c o n s i s t e n t with the o p t i m i z a t i o n o f such other p r o p e r t i e s as toughness, r e s i s t a n c e t o chemical a t t a c k , appearance o f the f a b r i c a t e d a r t i c l e , e t c . Thus, temperature, o r heat, may be considered t o be a h o s t i l e environment t o which the engineering p l a s t i c i s submitted. A wide v a r i e t y o f S/MA/X terpolymers were i n v e s t i g a t e d t o create the optimum balance o f p r o p e r t i e s t a k i n g advantage o f the well-known enhancement o f Tg with i n c r e a s e o f MA i n S/MA. In t h i s paper we d i s c u s s the e f f e c t o f terpolymer composition on r i g i d i t y i n terms o f Tg and, i n p a r t i c u l a r , DTUL. F i g u r e 1 shows a p l o t o f DTUL ( i n t h i s case, 12.7 χ 12.7 χ 127 mm i n j e c t i o n molded specimens) vs. MA content f o r S/MA copolymers (from the data o f the l a t e Dr. Y. C. Lee (2)) and, as an example o f the terpolymer cases, o f Tg vs. MA content i n S/MA/MM terpolymer a t ca. 6% (wt.) methyl methacrylate. The rate o f i n c r e a s e o f Tg with MA content i s approximately 2°C/percent (wt.) MA. F i g u r e 2 shows DTUL (12.7 χ 3.2 χ 127 mm, compression molded) vs. weight percent o f the t h i r d monomer f o r the cases o f S/MA/AN, S/MA/IB, and S/MA/MM, both g l a s s y polymer and rubber modified v e r s i o n s , where the data are taken from Lee (2) and Lee and Trementozzi (3, 4). The methyl a c r y l a t e and e t h y l a c r y l a t e cases are not shown i n order t o preserve c l a r i t y i n the f i g u r e , but both give somewhat lower DTUL s a t comparable (wt.) compositions. In a l l rubber-modified (R.M.) cases the percent o f a component given i s based on t o t a l m a t e r i a l , and i n the R.M.S/MA/AN case DTUL data f o r samples v a r y i n g from ca. 17 t o 23% MA are normalized t o a constant 20% MA content. S u r p r i s i n g l y , i n the methyl methacrylate case a broad maximum i n DTUL i s observed. This i s c o n s i s t e n t with Tg data, not shown here, f o r these m a t e r i a l s . Terpolymer composition a l s o a f f e c t s toughness. The p a r t i c u l a r case o f S/MA/AN i s i l l u s t r a t e d i n Table I , where three samples o f v a r y i n g AN content, but roughly comparable MA and rubber contents are d e s c r i b e d i n terms o f Izod impact. In t h i s case i t may be seen that i n c r e a s i n g AN l e v e l i n the terpolymer leads t o a general i n c r e a s e i n the Izod impact s t r e n g t h . The apparent equivalence o f the 0% and 5% AN cases may suggest that 5% AN i n the terpolymer i s too low a l e v e l to cause a s e n s i b l e e f f e c t on impact s t r e n g t h . A l s o shown are two blends o f the 5.1% AN S/MA/AN terpolymer with ABS (one blend c o n t a i n i n g Of-methyl styrene/AN copolymer f o r Tg improvement). Significant toughening i s observed i n these l a t t e r cases. Blending o f polymer with ABS o f f e r s c e r t a i n s i g n i f i c a n t property enhancement o p p o r t u n i t i e s such as r e s i s t a n c e t o chemical a t t a c k which increases with i n c r e a s i n g AN content, toughening, and m o d i f i c a t i o n o f p r o c e s s a b i l i t y c h a r a c t e r i s t i c s . However, such o p p o r t u n i t i e s can only be r e a l i z e d i f s u f f i c i e n t m i s c i b i l i t y of the g l a s s y (matrix) components i s achieved t o r e t a i n or enhance toughness; and p r e d i c t a b l e v a r i a t i o n o f p r o p e r t i e s with blend r a t i o i s t o be expected only f o r l a r g e l y or f u l l y m i s c i b l e matrix components. F o r t h i s reason, a study o f the m i s c i b i l i t y 1


52


Table I.

Izod Impact Strength of S/MA/AN Terpolymers

Material

*% AN


R.M. S/MA R.M. S/MA/AN R.M. S/MA/AN —R.M. S/MA/AN//ABS//of-MS/AN (50/38/12 by wt.) —R.M. S/MA/AN//ABS (60/40 by wt.)

%

MA

and

% Rubber

Blends Izod Impact (J/m)

0 5.1 9.5 2.5

20.7 22.3 19.9 11.1

13.7 14.3 13.4 20.0

112 112 135 157

3.1

13.4

21.9

157

"Percentage based on t o t a l blend composition except % AN includes only terpolymer c o n t r i b u t i o n — B l e n d s with ABS made with 22.3% MA, 5.1% AN terpolymer

given

% MA IN S/MA/MM TERPOLYMER

% MA IN S/MA COPOLYMER Figure 1. Effect of maleic anhydride content on distortion temperature under load (DTUL) and on glass transition temperature (Tg). Key: o, S/MA copolymer; and Δ, S/MA/MM terpolymer (ca. 6% MM).


HALL ET AL.

Styrene-Maleic Anhydride Terpolymer Blends


-.180

Φ

1301

8

12

16

20

WT. PERCENT TERM0N0MER Figure 2. Effect of termonomer content on DTUL in glassy and rubber-modified terpolymers. Key.o, S/MA/AN(25%)MA);e, R.M. S/MA /AN(correctedto 20% MA; ca. 14ψ rubber); •, RM. S/MA/IB(29ψ MA; 18ψ rubber); Δ, S/MA/MM; ν, R.M. S/MA/MM (22.5% MA; ca. 14ψ rubber). 0

0

0

0



54


of the terpolymers with SAN over a range o f compositions o f the components was undertaken. The p a r t i c u l a r case o f S/MA/MM and SAN i s d i s c u s s e d here as an example. Tg behavior and o p t i c a l c l a r i t y were used t o c h a r a c t e r i z e m i s c i b i l i t y . Thus the o b s e r v a t i o n o f a s i n g l e Tg i n a blend, combined with o p t i c a l c l a r i t y , i s taken t o i n d i c a t e t o t a l m i s c i b i l i t y , while two Tg's i d e n t i c a l with those o f the pure components i n d i c a t e i m m i s c i b i l i t y , and two Tg's a t temperatures between those o f the pure components i n d i c a t e p a r t i a l m i s c i b i l i t y (5). F i g u r e 3 i l l u s t r a t e s two immiscible blend composition cases, (a) and ( e ) , and three m i s c i b l e blend composition cases, ( b ) , (c) and ( d ) , where the compositions o f the components are given i n the f i g u r e ; and i n a l l but one case f i v e blend r a t i o s were i n v e s t i g a t e d . (The data i n F i g . 3(a) are f o r SAN//S/MA copolymer.) I t was noted f o r a l l systems s t u d i e d that a t any p a r t i c u l a r p a i r o f component compositions the q u a l i t a t i v e phase s t a t e d e s c r i p t i o n , i . e . , m i s c i b l e , immiscible, p a r t i a l l y m i s c i b l e , does not change with changing component p a i r r a t i o . Moreover, temperature dependent o p t i c a l t r a n s m i s s i o n experiments on a programmed hot stage gave no evidence o f a phase change, i . e . , lower c r i t i c a l s o l u t i o n temperature behavior, t o temperatures w e l l i n t o the p r o c e s s i n g range f o r any o f the ( g l a s s y s t a t e ) m i s c i b l e blends. Moreover, the presence of methyl methacrylate, a t l e a s t t o 13%, i n the terpolymer does not appear to a f f e c t m i s c i b i l i t y (see F i g u r e 3 ) . These observations allow a simple two-dimensional mapping o f the m i s c i b i l i t y composition r e g i o n i n terms o f percent AN i n the SAN vs. percent MA i n the S/MA/MM, as shown i n F i g u r e 4, where both S/MA copolymer and terpolymers o f v a r y i n g MM l e v e l s are represented. As may be seen i n F i g u r e 4, a r e l a t i v e l y wide r e g i o n o f m i s c i b l e component compositions i s a v a i l a b l e , p e r m i t t i n g a l l o y i n g o f the terpolymer with ABS. This r e s u l t i s q u a l i t a t i v e l y c o n s i s t e n t with the roughly s i m i l a r dependence o f s o l u b i l i t y parameter on copolymer composition i n the SAN and S/MA cases, as may be c a l c u l a t e d from molar a d d i t i v i t y r u l e s (see (6)). A l s o , the s o l u b i l i t y o f SAN with i t s e l f and with p o l y s t y r e n e has been reported by Molau (7) and i s c o n s i s t e n t with F i g u r e 4. S i m i l a r m i s c i b i l i t y behavior with SAN was observed i n the cases o f the other terpolymers. Blending o f the high heat r e s i s t a n t terpolymer with ABS t o form a m i s c i b l e matrix phase, as d e f i n e d i n F i g u r e 4, i s o f course, expected t o i n c r e a s e the heat r e s i s t a n c e o f the ABS. The data i n Table I I , taken from references (2-4), provide a systematic r e p r e s e n t a t i o n o f the v a r i a t i o n o f DTUL with terpolymer/ABS blend composition f o r the AN, IB, and MM-containing terpolymers (both g l a s s y and rubber-modified). In some o f these cases, as noted, a copolymer o f Of-methyl s t y r e n e / a c r y l o n i t r i l e was added to the f o r m u l a t i o n . From these data i t i s apparent t h a t DTUL does, indeed, i n c r e a s e with i n c r e a s i n g terpolymer c o n c e n t r a t i o n i n the blends. Moreover, the e f f e c t o f the terpolymer composition on DTUL o f the blends i s



50

100 0 θ A

100 0 θ A 50

100 0 θ A

50

WEIGHT PERCENT COMPONENT Β IN BLEND

50

100 0 Β A

50

190 100 θ

Figure 3. Glass transition temperature-composition plots for various SA N// S/ MA / MM blends to illustrate miscibility behavior.

9Q




70

Γ

60h

The Effects of Hostile Environments on Coatings and Plastics

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