Plasma Polymerization - American Chemical Society

18 Mechanical Properties of Polymer Composites Using Plasma-Modified Mica Filler

Downloaded by UNIV OF NEW ENGLAND on February 9, 2017 | http://pubs.acs.org Publication Date: September 24, 1979 | doi: 10.1021/bk-1979-0108.ch018

H. P. SCHREIBER Department of Chemical Engineering, Ecole Polytechnique, P.O. Box 6079, Montreal H3C 3A7, Québec, Canada M. R. WERTHEIMER and A. U. SRIDHARAN Department of Engineering Physics, Ecole Polytechnique, P.O. Box 6079, Montreal H3C, 3A7, Québec, Canada The use o f polymer-based composites has been i n c r e a s i n g r a p i d l y i n recent y e a r s . Mica has been an important m i n e r a l f i l l e r i n the e v o l u t i o n o f composites, i t s use being favored p a r t i c u l a r l y i n mechanical and i n e l e c t r i c a l i n s u l a t i o n a p p l i c a t i o n s because of i t s well-proven i n s u l a t i n g p r o p e r t i e s , i t s r e l a t i v e abundance, low cost and environmental s a f e t y . In any p r e p a r a t i o n of p o l y m e r - f i l l e r composites, there i s concern about the q u a l i t y of adhesion a t the f i l l e r / m a t r i x i n t e r face, and consequently over the i n t e r a c t i o n between f i l l e r and molten polymer a t the compounding stage. Various technologies have been proposed t o enhance adhesion; i n our l a b o r a t o r i e s , we have developed s u r f a c e treatment (encapsulation) techniques i n which mica i s exposed t o a " c o l d " microwave plasma ( i . e . T i t r o n T » 1) i n a "Large Volume Microwave Plasma Generator"(LMP) p r i o r t o being contacted with the polymer matrix. T h i s method of s u r f a c e m o d i f i c a t i o n i s b r i e f , n o n - p o l l u t i n g , and i n v o l v e s only low-cost m a t e r i a l s . Cold plasmas i n organic vapours are known to produce t h i n , s o l i d polymer f i l m s (2-40 which are g e n e r a l l y highly c r o s s - l i n k e d , adhere s t r o n g l y to the s u b s t r a t e and can be made f r e e of imperfections such as " p i n h o l e s " . In e a r l i e r work we have shown that mica s u r f a c e s can be rendered e i t h e r more h y d r o p h i l i c or hydrophobic through LMP treatments (5) and that c e r t a i n mechan i c a l p r o p e r t i e s of mica f i l l e d polyethylene (PE) and p o l y s t y r e n e (PS) can be enhanced when the f i l l e r was p r e - t r e a t e d i n ethylene (E) and styrene (S) plasmas, r e s p e c t i v e l y ( 6 ) . The e l e c t r i c a l prop e r t i e s of such composites were a l s o shown to respond f a v o r a b l y to plasma-modification o f the f i l l e r s u r f a c e (_7, 8) . e

e c

g a s

The present paper extends i n i t i a l work (6) on the m o d i f i c a t i o n o f mechanical p r o p e r t i e s i n m i c a - f i l l e d PE and PS, and i n p a r t i c u l a r explores the p o s s i b i l i t y of upgrading the p r o p e r t i e s of ΡΕ/PS blends. These two polymers are incompatible and are known to form 2-phase systems both i n the molten and s o l i d s t a t e s (9). In order t o modify f a v o r a b l y the i n t e r a c t i o n balance a t PE/PS c o n t a c t s , mica was subjected to LMP treatments using Ε and S mono mers i n sequence. In p r i n c i p l e , the generation of plasma-polymeri zed ethylene (PPE) and styrene (PPS) on the mica s u r f a c e might 0-8412-0510-8/79/47-108-287$05.00/0 © 1979 American Chemical Society

Shen and Bell; Plasma Polymerization ACS Symposium Series; American Chemical Society: Washington, DC, 1979.

288

PLASMA POLYMERIZATION

c r e a t e wetting/adhesion s i t e s f o r each of the matrix polymers with b e n e f i t s to the mechanical responses of the composite systems. An i n i t i a l view of t h i s p r i n c i p l e i s presented i n t h i s work.


EXPERIMENTAL A low-density, e x t r u s i o n grade polyethylene, melt flow index (10) = 1.2 ( s u p p l i e r Canadian I n d u s t r i e s , L t d ) , and a general pur pose polystyrene r e s i n ( s u p p l i e r Dow Chemical Co.) were the base polymers f o r t h i s study. Blends of these polymers i n 1:1 weight r a t i o s (ΡΕ/PS) were prepared by r o l l - m i l l i n g the m a t e r i a l s at 20tfc for 10 min, with the a d d i t i o n of 0.1% (wt.) of a commercial t h e r mal s t a b i l i z e r (Santonox - TM, Monsanto Co.) R o l l - m i l l e d stocks were reduced to f i b r i l consistency by mechanical g r i n d i n g . A high aspect r a t i o phlogopite mica with low water content s u p p l i e d by M a r i e t t a Resources I n t e r n a t i o n a l L t d . under the trade name of " S u z o r i t e " , was used as the f i l l e r i n t h i s r e s e a r c h . Dry-screened f r a c t i o n s (-40/70 mesh) were used i n s u r f a c e m o d i f i c a t i o n e x p e r i ments. In t h i s procedure approx. 5 gm samples were placed i n the quartz tube of the plasma generator (1, J5) and the charged tube was evacuated to about 10" 3 t o r r . A flow of e i t h e r Ε or S monomer gas was then e s t a b l i s h e d and c o n t r o l l e d with a needle v a l v e and flow meter to produce (dynamic) constant pressures i n the e x p e r i mental range 0 . 5 - 5 t o r r . Plasma discharges were produced w i t h about 1.0 KW of 2.45 GHz microwave power. Except where otherwise i n d i c a t e d , plasma treatments were of 90 sec. d u r a t i o n . In a number of i n s t a n c e s , mica samples were exposed to s e q u e n t i a l treatments i n Ε followed by S-monomer (E/S); the r e v e r s e , S/E sequence, was a l s o s t u d i e d . In these s e q u e n t i a l treatments, uniform c o n d i t i o n s of 2 t o r r monomer gas pressure were maintained. Mica samples were re-evacuated to ~ 10~3 t o r r f o l l o w i n g the f i r s t plasma exposure, and only then was the second monomer introduced i n t o the apparatus. The quartz tube r e a c t o r c o n t a i n i n g the mica was continuously r o t a ted during a l l plasma-treatments, to ensure uniform exposure of s u r f a c e s . Following treatment, mica samples were aged i n the LMP apparatus f o r 24 h r . under dry n i t r o g e n , and were then dispersed i n molten (190°C) PE, PS and ΡΕ/PS, i n a Brabender P l a s t i c o r d e r , to give stocks w i t h f i l l e r contents of 10 - 30% (W/W) . These stocks were then compression molded at 190°C. Specimens cut from the mol ded p l a t e s were used f o r determination of e l a s t i c modulus (ε) and of u l t i m a t e t e n s i l e strength (U.T.S.) i n s t r e s s - s t r a i n measure ments, with the I n s t r o n T e s t e r operating at jaw-separation speeds of 0.5 in/min and 5 in/min., r e s p e c t i v e l y . Impact r e s i s t a n c e data were obtained using the T i n i u s - O l s e n pendulum apparatus. A number of mica samples was examined by thermo-gravimetric a n a l y s i s , using the M e t t i e r Thermoanalyser and a heating r a t e of 5°C/min. C o n t r o l stocks of f i l l e d polymers included some i n which micas were heated under n i t r o g e n (300°C, 30 min) but were not exposed to plasmas. RESULTS AND DISCUSSION A) E l a s t i c Modulus:

The e l a s t i c moduli of c o n t r o l and t e s t



18.

scHREiBER E T A L .

Mechanical

Properties

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Composites

289

composites c o n t a i n i n g plasma-modified micas a r e represented as f u n c t i o n s of f i l l e r weight per-cent i n Figures 1, 2 and 3. F i g u r e 1 shows r e s u l t s f o r PE-based systems, F i g u r e 2 those f o r PS, and F i g . 3, the ε values f o r ΡΕ/PS composites. In a l l cases, the ε datum i s a mean of at l e a s t 5 separate determinations, with a r e p r o d u c i b i l i t y of about + 10%. The data f o r P E ( F i g . 1) may be compared with the f i n d i n g s of Woodhams and co-workers (11). In c o n t r a s t with these authors, no reinforcement due to untreated mica can be discerned - indeed, there i s a decrease of some 60% i n ε at 30% mica l o a d i n g . S i m i l a r l y , untreated mica produces no " b e n e f i t s " i n terms of modulus enhancement i n PS and ΡΕ/PS stocks ( F i g s . 2, 3 ) . We conclude that wetting and adhesion at mica/polymer i n t e r f a c e s i s poor, l e a d i n g to s i g n i f i c a n t decreases i n the e l a s t i c modulus. A very d i f f e r e n t s i t u a t i o n e x i s t i n composites with plasma-modified micas. As seen i n F i g . 1, micas produced by E, S/E and E/S plasmas r e i n f o r c e the PE matrix, the s e q u e n t i a l l y S/E t r e a t e d f i l l e r s more than t r i p l i n g the e l a s t i c modulus r e l a t i v e to PE, and i n c r e a s i n g t h i s by an order of magnitude r e l a t i v e to the (20%) composite using untreated mica. On the other hand, S-treated mica i s m a r g i n a l l y l e s s "compa t i b l e " with the polymer than i s the untreated f i l l e r . The p e r s i s t e n c e of the above p a t t e r n i n F i g u r e s 2 and 3 i s s e l f - e v i d e n t . Ε-modified micas produce a decrease i n ε of PS compo s i t e s , w h i l e S-treatment and s e q u e n t i a l l y - t r e a t e d micas enhance the e l a s t i c modulus. The o v e r a l l reinforcement of ~ 40% r e l a t i v e to v i r g i n PS i s not as pronounced as i n the case of PE, though a t 20% mica, the r e l a t i v e i n c r e a s e i n ε i s s t i l l a s u b s t a n t i a l one (e.g. ~ 250% f o r E/S v s . unmodified, f i l l e d s t o c k s ) . The r e s u l t s for ΡΕ/PS blends are analogous to those f o r PS. The data i n F i g s . 1 and 2 c l e a r l y i n d i c a t e the need t o match the monomer used i n plasma-treatment with the matrix polymer. A l l o wing f o r c e r t a i n s t r u c t u r a l d i f f e r e n c e s between PPE or PPS and t h e i r conventional counterparts (4.), i t i s n e v e r t h e l e s s suggested that much stronger bonding occurs a t the p o l y m e r / f i l l e r i n t e r f a c e , when the f i l l e r contains contact s i t e s which a r e e s s e n t i a l l y poly e t h y l e n e - l i k e , or p o l y s t y r e n e - l i k e . In view of the i n c o m p a t i b i l i t y of PE and PS (9) the d e t e r i o r a t i o n i n ε when the monomer used i n plasma-polymerization and matrix polymer are mismatched, may be r a t i o n a l i z e d . The s u p e r i o r performance i n a l l cases ( F i g . 1, 2, 3) of s e q u e n t i a l l y - t r e a t e d micas i s p a r t i c u l a r l y noteworthy. Plasma exposure times i n these micas have been doubled hence a more e f f e c t i v e encapsulation of the f i l l e r s u r f a c e by plasma-polymer i s i n d i c a t e d . The frequency of matrix polymer/mica contacts (inherent l y unfavorable) i s thereby reduced, with b e n e f i c i a l consequences. Assuming that polymer s i t e s formed i n the f i n a l step of s e q u e n t i a l plasma treatments are more r e a d i l y a c c e s s i b l e , the advantages of S/E sequences i n F i g . 1 and of E/S i n F i g . 2 appear l o g i c a l . The evident advantage of S/E over E/S sequences i n the PS/ΡΕ blends ( F i g . 3) may be due to the f a c t that styrene i s a more r e a d i l y plasma-polymerized monomer (2) . Conceivably, under present c o n d i t i o n s , PPS l a y e r s may tend to obscure PPE s i t e s i n E/S sequences, while i n S/E sequences both types of polymer a r e more r e a d i l y



290

PLASMA

POLYMERIZATION

/

/ / / (S/E)

/

(E/S)

V / .

-»-'/

/ /

/ / /

/(E)

(HEATED) """S^

^

10 WT

Figure

1.

Elastic modulus

T~

(CONTROL)

20 %MICA

of Ρ Ε stocks—effect ments

30

of mica and various surface


treat


.

scHREiBER E T A L .

Mechanical

Properties

of

Composites

(E/S)

70

I

/

(S/E)_

ρ-

- •

/

6.0 h

/

s

/

ιϊ S'o

(S)

0\

\ \

I- CO CO Q. < 4.0

\ \

Δ

* ON

\ \

Ν Ν

Ν Ν

3.0

^ \

Ν

(CONTROL)

Ν

(E).(HEATED)

Ν

Κ . 10

Figure

2.

Elastic modulus

20 WT % MICA

of PS stocks—effect ments

30

of mica and various surface


treat


292


a v a i l a b l e on the mica s u r f a c e f o r bonding with the matrix polymers. The l a t t e r treatments thus appear to produce the more e f f e c t i v e " b r i d g i n g " agents, and a p p r e c i a b l y modify the inherent incompati b i l i t y problem i n t h i s polymer p a i r . F i n a l l y , c o n t r o l experiments u s i n g heated micas were p e r f o r med i n order to separate plasma and simple h e a t i n g e f f e c t s . As shown i n F i g . 1, 2 and 3, m o d i f i c a t i o n s i n e l a s t i c modulus are plasma - and not heat-generated. B) T e n s i l e and Impact Performance: Table I presents a summa ry of t e n s i l e impact and u l t i m a t e t e n s i l e data f o r the three s e t s of composites. For ease of comparison both sets of data are norma l i z e d to the r e f e r e n c e t e n s i l e impact or u l t i m a t e t e n s i l e p e r f o r mance of the u n f i l l e d polymer m a t r i x . The t a b u l a t i o n makes c l e a r the e m b r i t t l i n g e f f e c t of mica on the i n h e r e n t l y d u c t i l e PE; on the other hand, the t e n s i l e impact r e s i s t a n c e of f i l l e d PS stocks i s s l i g h t l y i n c r e a s e d , hence mica acts as a toughener f o r t h i s polymer. Both sets of performance data i n PS/ΡΕ blends are d e t e r i o r a t e d by the a d d i t i o n of the f i l l e r . The general trend, already e s t a b l i s h e d by the ε values i s repeated i n Table I : Marked property improvement i s a s s o c i a t e d with a match of monomer environment used i n plasma-treatments of mica and the intended polymer matrix. Mismatches again tend to produce r e s u l t s which are i n f e r i o r to those obtained with untreated micas. The most i n t e r e s t i n g r e s u l t s again are those f o r stocks using sequen t i a l l y - t r e a t e d micas. The " b i f u n c t i o n a l " f i l l e r surfaces are the near equivalents of matched - monomer f i l l e r s when used with s i n g l e polymer m a t r i x e s . The e f f e c t i v e c o u p l i n g tendency shown by these b i f u n c t i o n a l f i l l e r s are p a r t i c u l a r l y evident i n the PE/ PS b l e n d . Here, t e n s i l e s t r e n g t h i s r a i s e d by 30 - 50% over that of u n f i l l e d c o n t r o l s , and by w e l l over 100% r e l a t i v e to compounds with comparable q u a n t i t i e s of untreated micas. Even more appre c i a b l e inprovements are observed i n the t e n s i l e impact performan ce. These r e s u l t s demonstrate the t e c h n i c a l f e a s i b i l i t y of produ c i n g complex, m u l t i - f u n c t i o n a l s u r f a c e p r o p e r t i e s by the LMP route, and consequently suggest the p o s s i b i l i t y of s i g n i f i c a n t l y upgra ding and s t a b i l i z i n g the p r o p e r t i e s of i n h e r e n t l y incompatible polymer combinations. These concepts warrant more d e t a i l e d study i n the f u t u r e . I t was not w i t h i n the scope of t h i s work to perform d e t a i l e d analyses of the chemical m o d i f i c a t i o n s imparted to plasma-treated mica s u r f a c e s . Thermogravimetric analyses were performed, however, and these p r o v i d e i n d i r e c t c o n f i r m a t i o n f o r the presence of plasmaproduced polymers on the f i l l e r s u r f a c e . Weight l o s s observations i n h e a t i n g v a r i o u s mica specimens to 300°C are given i n Table I I . Thermogravimetry was a l s o performed on micas as r e c e i v e d , without f u r t h e r p r e p a r a t i o n of the f i l l e r . Plasma-treated micas, however, were s t o r e d f o r periods of about 1 week a t 70% r . h . and ambient temperature p r i o r to a n a l y s i s . Of the plasma-modified f i l l e r s , only Ε-treated micas d i s p l a y a p p r e c i a b l e w e i g h t - l o s s , though even here t h i s i s g r e a t l y reduced i n comparison with untreated mica. A t t r i b u t i n g the bulk of weight l o s s e s to the e v o l u t i o n of p h y s i sorbed and chemisorbed water (12), the data i n Table I I a t t e s t to



S S S

Ε Ε Ε

S/Ε S/E S/E

E/S E/S E/S

10 20 30

10 20 30

10 20 30

10 20 30 0.172 0.163 0.115

0.180 0.167 0.188

0.206 0.217 0.188

0.044 0.030

0.16 0.11

heat heat

10 20

2.88 2.39 2.90

1.85 1.53 2.15

0.65 0.47 0.45

2.90 2.66 2.21

1.17 1.20

1.18 1.13 1.07

0.097 0.055 0.047

10 20 30

normalization

0.20 1.00

Treatment

1.88 2.06 1.88

1.86 1.45 2.17

0.56 0.51 0.40

0.73 0.59

0.63 0.50

0.65 0.47 0.39

0.96 1.00

ΡΕ/PS

1.41 1.18

1.25 1.18

1.72 1.59 1.51

0.33 0.22

0.61 0.54

0.55 0.47 0.31

1.92 1.00

PE

1.16 1.20

0.95 0.90

0.11 0.07

0.48 0.36

0.23 0.20

0.20 0.15 0.09

5.84 1.00

1.43 1.37

1.16 1.11

0.93 0.88

1.26 1.19

0.80 0.60

0.79 0.58

1.84 1.00

PE/PS

PS

PS

PE

3

U.T.(p.s.i. χ 1θ" )

T e n s i l e Impact ( f t - l b / i n )

18.6 1.00

%

Filler:

TENSILE IMPACT AND ULTIMATE TENSILE PERFORMANCE OF PLASMA - TREATED MICA STOCKS

TABLE I


PLASMA

294

POLYMERIZATION

20.0 h CO

•

3

15.0

ο»

^

(S/E) —

_ •

(E/S)

z2 Downloaded by UNIV OF NEW ENGLAND on February 9, 2017 | http://pubs.acs.org Publication Date: September 24, 1979 | doi: 10.1021/bk-1979-0108.ch018

ο* (OQ. -I UJ

10.0

—

Q -

\

—

5.0

_

•

_ Δ

10 WT. % Figure

3.

Elastic

modulus

φ ^(CONTROL)(HEATED)

(Ε)

30

20 MICA

of ΡΕ/PS stocks—effect treatments

Δ_

of mica and various

surface

TABLE I I THERMOGRAVIMETRIC LOSS TO 300°C

AW(%) at

Sample

C o n t r o l mica (a)

E-Plasma (a) S-Plasma E/S P l a s m a S/E Plasma

(a)

ANALYSES ON VARIOUSLY TREATED MICAS: WEIGHT

( a )

at

at

at

50°C

100°C

200°C

300°C

0.07

0.11

0.33

0.36

nil

0.02

0.06

0.11

nil

nil

0.02

0.04

nil

nil

< 0.01

0.06

nil

nil

nil

A l l plasma sequences a t 2 t o r r pressure,

< 0.02

90 s e c . d u r a t i o n .



18.

SCHREIBER E T A L .

Mechanical

Properties

of

Composites

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the presence of e s s e n t i a l l y impenetrable hydrophobic l a y e r s a t the f i l l e r s u r f a c e , f o l l o w i n g plasma treatment. The l e s s impressive performance f o l l o w i n g ethylene-treatment may be due t o incomplete s u r f a c e coverage; we assume that the a r b i t r a r i l y chosen plasmatreatment c o n d i t i o n s were i n s u f f i c i e n t t o produce such a l a y e r with the l e s s r e a d i l y polymerized monomer. C) Plasma-treatment v a r i a b l e s : In a l l o f the above comparisons, the v a r i o u s mica samples had been exposed to plasmas under a r b i t r a r i l y s e l e c t e d , constant c o n d i t i o n s of monomer pressure, plasma d u r a t i o n and a p p l i e d power. I t i s very probable (2,_4) that these v a r i a b l e s and p o s s i b l y others, such as r e a c t o r geometry and post-treatment h i s t o r y , may i n f l u e n c e s t r o n g l y the magnitude o f s u r f a c e m o d i f i c a t i o n e f f e c t s a t t a i n e d by the present route. For t h i s reason the performance m o d i f i c a t i o n s of polymer composites w i l l a l s o depend on the exact s e l e c t i o n of treatment v a r i a b l e s . A d e t a i l e d study of the problem i s c a l l e d f o r to permit the design of s u r f a c e m o d i f i c a t i o n procedures capable of meeting d e s i r e d degrees of performance m o d i f i c a t i o n . As a f i r s t step i n t h i s d i r e c t i o n , we s t u d i e d the e f f e c t of S monomer pressure and of treatment d u r a t i o n on the p r o p e r t i e s of 10% m i c a - f i l l e d PS s t o c k s . Monomer pressure was v a r i e d i n the range 1 - 4 t o r r , i n a l l cases f o r 90 sec plasma d u r a t i o n . On the other hand, the standard 2 t o r r pressure was maintained i n a s e r i e s of treatment durations i n the range 60 - 360 sec. The e f f e c t of v a r y i n g S monomer pressure i s d i s p l a y e d i n F i g . 4; that of v a r y i n g d u r a t i o n i n F i g . 5. Impact s t r e n g t h and e l a s t i c modulus are the performance c r i t e r i a used i n each sequence. I t i s evident that monomer pressure and plasma d u r a t i o n s t r o n g l y a f f e c t the modifying i n f l u e n c e of mica f i l l e r i n the PS stock. An optimum monomer pressure i n the 2-3 t o r r range i s i n d i cated, the t e n s i l e impact being p a r t i c u l a r l y s e n s i t i v e to t h i s v a r i a b l e ( F i g . 4 ) . Treatment time i s even more s i g n i f i c a n t ( F i g . 5), both modulus and impact r e s i s t a n c e responding s t r o n g l y to i t s v a r i a t i o n s . An optimum treatment time i n the range 100 - 150 s e c . appears to be a s s o c i a t e d with e l a s t i c modulus response. We assume that t e n s i l e impact of mica f i l l e d PS improves with plasma durat i o n up to about 240 s e c , and remains near an "optimum p l a t e a u " i f longer treatment times a r e used f o r s u r f a c e m o d i f i c a t i o n s of the mica. Considering the probable l a r g e number of important treatment v a r i a b l e s and the l i k e l i h o o d of interdependence among them, the subject becomes one of c o n s i d e r a b l e complexity and importance. D e t a i l e d s t u d i e s a r e underway to c l a r i f y the s i t u a t i o n . CONCLUSIONS I t i s concluded that s u r f a c e m o d i f i c a t i o n of mica, produced by exposing the m a t e r i a l to microwave plasmas, can create l a r g e p o s i t i v e or negative e f f e c t s i n the mechanical p r o p e r t i e s of f i l l e d polymers and polymer blends. Property enhancement i s assoc i a t e d with the production of s u r f a c e l a y e r s on the f i l l e r which



296

PLASMA

2.0

Figure

Figure

4.

5.

Influence

Influence

POLYMERIZATION

3.0

Ρ (torr)

of S monomer pressure of PS mechanical

on effect of mica (10%) as properties

modifier

of S-monomer plasma duration on effect of mica (10% ) as modifier of mechanical properties in PS


18.

scHREiBER E T A L .

Mechanical

Properties

of

Composites

297


are chemically s i m i l a r to the matrix polymer. I t i s assumed that strong adhesion a t p o l y m e r / f i l l e r contacts i s promoted by such plasma-treatments and accounts f o r the observed property enhance ment. I t has been shown that s e v e r a l d i s s i m i l a r surface s t r u c t u r e s can be produced on micas by s e q u e n t i a l plasma treatments with appropriate monomers, a l l o w i n g the f i l l e r to serve as a b r i d g i n g ( s t a b i l i s i n g ) agent f o r incompatible polymer p a i r s . Comprehensive s t u d i e s of the v a r i a b l e s i n plasma p o l y m e r i z a t i o n w i l l be r e q u i r e d to optimize documented e f f e c t s i n the behavior of composites and polyblends. ACKNOWLEDGMENT F i n a n c i a l support f o r t h i s research was r e c e i v e d from the N a t i o n a l Research C o u n c i l of Canada, and from the Quebec M i n i s t r y of Education. We thank P r o f . R.G. B o s i s i o f o r the loan of equip ment.

ABSTRACT A "Large Volume Microwave Plasma Generator" (LMP) has been used for surface treatment of phlogopite mica flakes in plasmas of styrene, ethylene and in sequences of these organic vapors. Plasma-modified mica flakes were used as fillers, at 10 - 30 wt.% levels, in polyethylene (ΡΕ), polystyrene (PS) and in 1:1 mixtures of these polymers. Tensile and impact properties of the composites show that ethylene and styrene-plasma treatments enhance the pro perties of PE and PS, respectively, but weaken the composite when the treatment monomer and matrix polymer are mismatched. Micas exposed to the two monomer vapors in sequence are particularly effective in enhancing the mechanical properties of inherently incompatible ΡΕ/PS blends, seemingly acting as coupling or compa tibilizing agents for this polymer pair. The results are consis tent with the formation of plasma-polymerized layers which either act as "bridges" between the polymer matrix and the mica f i l l e r , or else (in the case of mismatch due to incompatible polymers) prevent effective bonding. Initial studies have been carried out on the variation in plasma effectiveness due to changes in mono mer pressure and treatment time. LITERATURE CITED 1): R.G. BOSISIO, M.R. WERTHEIMER and C.F. WEISSFLOCH, J.Phys. Sc. Instr. 6, 628 (1973). 2): J.R. HOLLAHAN and A.T. BELL: "Techniques and Applications of Plasma Chemistry", Wiley-Interscience Publishers, New York,Ν.Y. (1974). 3): M.R. HAVENS, M.E. BIOLSKI and K.G. MAYHAN, J. Vac. Sci. and Technol. 13, 575 (1976). 4): "Plasma Chemistry of Polymers" M.Shen, Ed. Marcel Dekker, Inc. New York, N.Y. (1976). 5): A. BIALSKI, R. St.J. MANLEY, M.R. Wertheimer and H.P. E.,




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SCHREIBER, J. Macromol. Sci., Chem. A10, 609 (1976). 6) H.P. SCHREIBER, Y. TEWARI, and M.R. WERTHEIMER, J. APpl. Poly. Sci. 20, 2663, (1976). 7) M.R. WERTHEIMER, L. PAQUIN and H.P. SCHREIBER, J. Appl. Poly., Sci. 20, 2675 (1976). 8) L. PAQUIN, A.U. SRIDHARAN, M.R. WERTHEIMER and H.P. SCHREIBER. In Press: Proc. 2nd Int'l Conference on Composite Materials, (ICCM II) Toronto, Canada, April 1978. 9) C.D. HAN and T.C. YU, Polym. Eng. Sci. 12, 81 (1972). 10) A.S.T.M. D-1238-62& Amer. Soc. for Test. Mat. Philadelphia (1962). 11) J. LUSIS, R.T. WOODHAMS and M. XANTHOS, Polym. Eng.Sci. 13, 139 (1973). 12) M.S. METZIK, V.D. PEREVERTAEV, V.A. LIOPO, G.T. TIMOSCHENKO and A.V. KISELEV, J. Coll. Interface Sci. 43, 4223 (1974). Received March 29, 1979.


Plasma Polymerization - American Chemical Society

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