Properties of Filled Polyphenylene Sulfide Compositions

15 Properties of Filled Polyphenylene Sulfide Compositions

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H.

WAYNE

HILL,

JR., R O B E R T T.

WERKMAN,

and G .

E.

CARROW

Phillips Petroleum Co., Research and Development Dept., Bartlesville, Okla. 74004

Blends of polyphenylene sulfide and variousfibrousfillers yield a variety of new reinforced thermoplastics which can be readily injection molded. Compounds containing 40% glassfibercombine good processability with excellent me chanical properties. Fybex inorganic titanate fiber and asbestos which can be used at levels up to 20% reinforce to a lesser extent than glass fiber. The glass-reinforced compounds are equal in mechanical properties to other glass-reinforced thermoplastics up to 300°F and generally are superior from 300°-500°F. The compounds are non burning, possess excellent electrical properties, and have superior resistance to a variety of chemical environments. Compression molded compounds and applications for vari ous filled polyphenylene sulfide compositions are also discussed.

"polyphenylene

sulfide ( P P S ) is a n e w l y a v a i l a b l e , c o m m e r c i a l r e s i n

w h i c h possesses t h e u n u s u a l c o m b i n a t i o n of h i g h t h e r m a l s t a b i l i t y a n d o u t s t a n d i n g c h e m i c a l resistance. affinity f o r a v a r i e t y of r e i n f o r c i n g pression m o l d i n g compositions.

T h e p o l y m e r shows a n excellent fillers

i n both injection a n d com

These properties a n d t h e availability of

the r e s i n i n several different grades p r o v i d e u t i l i t y i n v a r i o u s c o a t i n g applications α

as w e l l

as i n j e c t i o n a n d c o m p r e s s i o n

molding

markets

2,3). R y t o n P P S grade V - l is a s u b s t a n t i a l l y l i n e a r p h e n y l e n e

sulfide

p o l y m e r of r e l a t i v e l y l o w m o l e c u l a r w e i g h t as i n d i c a t e d b y a m e l t

flow

of greater t h a n 2000 g r a m s / 1 0 m i n m e a s u r e d i n a m e l t i n d e x e r at 315 ° C w i t h a 5-kg weight.

G r a d e V - l is a c r y s t a l l i n e p o l y m e r m e l t i n g a t ca. 149

Deanin and Schott; Fillers and Reinforcements for Plastics Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

150

FILLERS

AND

REINFORCEMENTS FOR

PLASTICS

2 8 5 ° C a n d is u s e f u l for c o a t i n g a p p l i c a t i o n s a n d as a feedstock f o r p r e paring molding compounds

(1,2,3).

W h e n g r a d e V - l p o l y m e r is h e a t e d

i n a i r a b o v e a b o u t 2 6 0 ° C , c h a i n extension a n d c r o s s l i n k i n g o c c u r , p r o d u c i n g a c u r e d p o l y m e r of h i g h e r m o l e c u l a r w e i g h t .

R y t o n P P S grade

P - 4 is a c u r e d p o l y m e r w i t h a n o m i n a l m e l t flow of 50 g r a m s / 1 0 m i n a n d is i n t e n d e d f o r i n j e c t i o n m o l d i n g alone or i n c o m b i n a t i o n various

fillers.

Injection Molding Downloaded by UNIV OF NEW SOUTH WALES on April 12, 2016 | http://pubs.acs.org Publication Date: June 1, 1974 | doi: 10.1021/ba-1974-0134.ch015

with

Compounds

Preparation. A n y filler w h i c h is stable at the 6 0 0 ° - 7 0 0 ° F p r o c e s s i n g temperatures r e q u i r e d c a n b e u s e d i n P P S m o l d i n g c o m p o u n d s . fillers

Fibrous

s u c h as glass are of p a r t i c u l a r interest since t h e y p r o v i d e t h e great-

est i m p r o v e m e n t i n m e c h a n i c a l properties at t h e lowest cost.

Injection

m o l d i n g c o m p o u n d s are p r e p a r e d b y d r y b l e n d i n g the d e s i r e d filler w i t h P P S g r a d e P - 4 . I n t e n s i v e d r y m i x e r s c a n b e u s e d for b l e n d i n g p a r t i c u l a t e fillers

a n d for some short

fiber

fillers

s u c h as F y b e x i n o r g a n i c t i t a n a t e

fiber w h e n l o w rotor speeds are u s e d . C o n e b l e n d e r s o r d r u m t u m b l e r s are p r e f e r r e d f o r d r y b l e n d i n g c h o p p e d glass to m i n i m i z e fiber d a m a g e . G l a s s fibers c a n b e most r e a d i l y i n c o r p o r a t e d i n t o P P S i n t h e f o r m of r o v i n g i n t r o d u c e d t h r o u g h t h e vent of a t w i n screw extruder. T h e p r e f e r r e d glass is of l o w ( 0 . 3 % ) s i z i n g l e v e l a n d free of c o u p l i n g agents since these are p r o n e to d e c o m p o s e a n d generate gas at the h i g h t e m peratures i n v o l v e d . A l s o , P P S b o n d s w e l l to glass, a n d c o u p l i n g agents are not r e q u i r e d . T h e glass fibers i n t h e P P S c o m p o u n d s

prepared i n a

t w i n screw e x t r u d e r h a v e a n average aspect r a t i o of 20. T h e filler content of these c o m p o u n d s

is l i m i t e d b y the i n j e c t i o n m o l d i n g process a n d

ranges f r o m a b o u t 2 0 % f o r asbestos or F y b e x to a b o u t 40 w t % f o r glass fiber.

T h e i n j e c t i o n m o l d i n g flow decreases s h a r p l y as t h e percentage

filler is i n c r e a s e d a b o v e t h e levels i n d i c a t e d for the respective Table I. S t o c k t e m p e r a t u r e , °F M o l d t e m p e r a t u r e , °F I n j e c t i o n pressure, p s i F i l l speed Nozzle H o l d pressure, p s i B a c k pressure G a t e size, i n c h

of

fillers.

Injection Molding Conditions 600-700 150-300 12,000-18,000 fast nondrool 5,000-10,000 none o r l o w 0.050-0.30

Molding Conditions. P P S c o m p o u n d s c a n b e i n j e c t i o n m o l d e d p r e f e r a b l y i n r e c i p r o c a t i n g s c r e w m a c h i n e s u n d e r c o n d i t i o n s s i m i l a r to other filled resins except f o r h i g h e r stock temperatures. T h e s e c o n d i t i o n s are l i s t e d i n T a b l e I. P P S c o m p o u n d s h a v e a s l i g h t t e n d e n c y to gas at m o l d i n g


15.

HILL, JR. E T A L .

temperatures.

Polyphenylene

151

Sulfide

T h e r m o g r a v i m e t r i c analyses s h o w t h a t this amounts

a b o u t 0 . 1 % / h r at 6 0 0 ° F a n d a b o u t 0 . 5 % / h r at 7 0 0 ° F .

to

T o prevent v o i d

f o r m a t i o n e s p e c i a l l y i n t h i c k e r p a r t s , t h e l o w e r stock temperatures a l o n g w i t h h i g h i n j e c t i o n a n d h o l d pressures are r e c o m m e n d e d .

W i t h proper

m o l d i n g c o n d i t i o n s a n d g o o d m o l d d e s i g n , w e l l f o r m e d parts free

of

v o i d s a n d sink m a r k s c a n b e p r o d u c e d . T h e m o l d i n g c o n d i t i o n s w i l l h a v e s o m e effect o n t h e properties of the m o l d e d parts. H i g h e r m o l d t e m p e r a tures f a v o r h i g h e r tensile p r o p e r t i e s a n d better surface a p p e a r a n c e w i t h


some loss i n i m p a c t strength. T h e p r o p e r t i e s of t h e c o m p o u n d s

reported

h e r e are b a s e d o n specimens m o l d e d at 600° F stock t e m p e r a t u r e , 150° F m o l d t e m p e r a t u r e , 15,000 p s i i n j e c t i o n pressure, a n d 5,000 p s i h o l d p r e s sure.

T h e compounds

h a v e b e e n r e m o l d e d t h r o u g h three cycles

with

o n l y 1 0 % loss i n tensile strength.

Properties. A s s h o w n i n F i g u r e 1, tensile s t r e n g t h a n d flexural m o d u l u s of P P S increase m a r k e d l y w i t h i n c r e a s i n g glass fiber content, a n d at 50 w t %

glass, tensile is i n c r e a s e d m o r e t h a n t w o f o l d a n d m o d u l u s

more than threefold.

I n c o m p a r i s o n asbestos i m p a r t s o n l y a m o d e r a t e

increase i n these p r o p e r t i e s u p to 25 w t % i n P P S . T h e l o w e r r e i n f o r c e m e n t r e a l i z e d f r o m asbestos c o m p a r e d w i t h glass is a t t r i b u t e d to p o o r e r d i s p e r s i o n a n d l o w e r a d h e s i o n w i t h asbestos.

W h i l e not s h o w n , F y b e x

i m p a r t s a b o u t t h e same i m p r o v e m e n t i n properties as glass fiber u p to 20 w t % .

Asbestos a n d F y b e x fillers r e d u c e t h e m e l t flow of P P S c o m -

p o u n d s m o r e d r a s t i c a l l y t h a n glass

fiber.

Thus, injection moldable P P S

c o m p o u n d s are l i m i t e d to a b o u t 2 0 % asbestos or F y b e x vs. 4 0 % T y p i c a l p r o p e r t i e s of v a r i o u s i n j e c t i o n m o l d e d c o m p o u n d s

glass.

are g i v e n i n

T a b l e I I . T h e a d d i t i o n o f 2 0 % asbestos to P P S gives a m o d e s t increase i n tensile a n d s u b s t a n t i a l i m p r o v e m e n t s i n

flexural

modulus a n d heat


152

FILLERS

deflection t e m p e r a t u r e .

AND

REINFORCEMENTS

T h e a d d i t i o n of 4 0 %

FOR

PLASTICS

glass fiber to P P S gives

t h e greatest r e i n f o r c e m e n t a n d d o u b l e s most m e c h a n i c a l p r o p e r t i e s . compound

with 20%

F y b e x has p r o p e r t i e s i n b e t w e e n

those

The

of

the

asbestos a n d glass-filled c o m p o u n d s b u t is s u p e r i o r to t h e m i n c o l o r a n d surface a p p e a r a n c e . P P S is a m o n g the least c o m b u s t i b l e of t h e r m o p l a s t i c s . F o r e x a m p l e , t h e m i n i m u m c o n c e n t r a t i o n of o x y g e n b u s t i o n of P P S is 4 4 % . slightly the percentage

oxygen

required.

com

T h e electrical properties

several P P S c o m p o u n d s h a v e b e e n d e s c r i b e d ( 4 ) .


to s u p p o r t

T h e a d d i t i o n of glass o r asbestos to P P S increases of

A l t h o u g h the addition

of fillers degrades the e l e c t r i c a l p r o p e r t i e s — F y b e x m o r e so t h a n g l a s s — the compounds

r e t a i n l o w d i e l e c t r i c constants a n d d i s s i p a t i o n factors

over a w i d e f r e q u e n c y r a n g e .

T h u s these c o m p o u n d s

e l e c t r o n i c a p p l i c a t i o n s at h i g h frequencies

are s u i t a b l e for

w h e r e d i s s i p a t i o n factor is

i m p o r t a n t , a n d t h e y are finding use i n s u c h a p p l i c a t i o n s . Table II.

T y p i c a l Properties of Reinforced PPS

PPS Density Tensile, psi Elongation, % F l e x , mod., psi Χ 10~ Flex, strength, psi Impact, ft-lb/in. n o t c h e d (% X Y ) u n n o t c h e d (% X ]/ ) H a r d n e s s , shore D H e a t deflection a t 264 p s i , ° F Compressive strength, psi M o l d shrinkage, i n c h / i n c h 3

2

2

1.35 9,000 3 600 20,000

80/20' PPS/ Asbestos*

80/20" PPS/ Fybex

60/40"

1.52 12,000 2 1,000 22,000

1.53 15,000 2 1,400 25,000

1.65 22,000 2 2,200 35,000

0.4 2.0 86 278 16,000 0.01

0.4 3.0

1.0 3.0

89 >425

88 >425

— —

° Parts by weight Johns Manville 7RF1 Owens Corning 497 X 5

PPS/ Glass"

1.0 4.0 90 >425 21,000 0.002

— —

6

c

T h e effect of t e m p e r a t u r e o n tensile s t r e n g t h a n d of 4 0 %

glass-reinforced P P S is s h o w n i n F i g u r e 2.

flexural

modulus

T h e curves

k

s i m i l a r trends w i t h a m a r k e d decrease i n b o t h p r o p e r t i e s b e t w e e n

show 175°

a n d 275° F as t h e p o l y m e r undergoes a glass t r a n s i t i o n . A b o v e 2 7 5 ° F the p r o p e r t i e s d e c l i n e m o r e g r a d u a l l y u p to 5 0 0 ° F . u n f i l l e d p o l y m e r , the P P S c o n t a i n i n g 4 0 %

Compared with

the

glass fiber has a m a r k e d s u

p e r i o r i t y i n p r o p e r t i e s over the t e m p e r a t u r e r a n g e s h o w n . A c o m p a r i s o n of t e n s i l e s t r e n g t h vs. t e m p e r a t u r e for several p o l y m e r s r e i n f o r c e d w i t h 30%

glass fiber is l i s t e d i n T a b l e I I I .

These compounds

have similar

tensiles at 7 5 ° F , a n d a l l decrease i n tensile w i t h i n c r e a s i n g t e m p e r a t u r e .


15.

Polyphenylene

HILL, JR. E T A L .

153

Sulfide

T h e P P S c o m p o u n d has s o m e w h a t greater loss i n tensile b e t w e e n 150° F a n d 2 5 0 ° F , b u t r e t e n t i o n of tensile a b o v e 300° F is s u p e r i o r . O v e n a g i n g


tests at 400° F h a v e i n d i c a t e d no significant loss i n tensile over 1000 hours.

O

100

200

300

TEMP.*F

Figure 2.

400

500

0

100

200

300

TEMP.°F

Effect of temperature on tensile and flexural

400

500

modulus

F l e x u r a l creep, w h i c h is a measure of the l o n g t e r m l o a d b e a r i n g c a p a b i l i t y of a m a t e r i a l , is s h o w n i n F i g u r e 3. A t 75° F a n d 5000 p s i fiber stress, t h e glass-reinforced P P S shows l o w t o t a l creep a n d a v e r y l o w creep r a t e t h r o u g h 1000 hours a n d a v e r y s u b s t a n t i a l i m p r o v e m e n t over the base p o l y m e r . A t 150° F u n d e r the same stress, the glass-reinforced P P S shows s o m e w h a t h i g h e r creep rate u p to 500 hours. Table III.

Tensile vs. Temperature for Various Glass-Reinforced Polymers

Temp.j °F

Polycarbonate + 80% glass

75 150 250 300 350 400 500 550

15,600 12,000 7,000 0

Modified Polyphenylene Oxide + 30% Glass 17,000 14,000 8,900 5,000 2,000 0

Polysulfone + 80% Glass

PPS + 30% Glass

15,700 13,000 11,000 8,000 4,000 0

18,000 15,000 8,000 7,000 6,000 4,000 1,000 0

0

T h e results of f r i c t i o n a n d w e a r tests p e r f o r m e d o n a n L F W - 1 f r i c t i o n a n d w e a r tester are g i v e n i n T a b l e I V . V a r i o u s P P S c o m p o u n d s w e r e tested as flat b l o c k s against s t a n d a r d h a r d e n e d steel rings. U n f i l l e d P P S s h o w e d i n t e r m e d i a t e f r i c t i o n a n d w e a r values. T h e a d d i t i o n of glass fiber


154

FILLERS

A N D R E I N F O R C E M E N T S F O R PLASTICS

or F y b e x gave a s m a l l r e d u c t i o n i n coefficient o f f r i c t i o n b u t a m a r k e d increase i n w e a r . Tests o n P P S - f i b e r g l a s s c o m p o u n d s c o n t a i n i n g v a r i o u s l u b r i c a t i n g fillers s h o w e d 5 % m o l y b d e n u m d i s u l f i d e w a s ineffective i n reducing friction or wear, 9 % graphite reduced wear quite markedly, a n d 2 5 % P T F E reduced both friction a n d wear. pounds

S e v e r a l of these c o m

have friction a n d wear properties comparable

w i t h those o f

acetal homopolymer a n d are being further investigated i n sliding-friction a n d j o u r n a l - b e a r i n g tests.


1.0

0.8

-

-

6 0 / 40 Ρ P S - G L A S S F I B E R ( l 5 0 F )

6 0 / 4 0 P P S - G L A S S FIBER ( 7 5 F )

-

1 10

1

Figure 3. Table I V .

1 100

T I M E , HRS

1000

Flexural creep at 5000 psi

L F W - l Friction and Wear D a t a Coefficient of

Friction*

Compound

0 rpm

100 rpm

190 rpm

PPS 60/40 PPS-glass 80/20 P P S - F y b e x 70/25/5 PPS-glass-MoS 55/36/9 PPS-glass-graphite 50/25/25 P P S - g l a s s - P T F E 75/25 P P S - P T F E Acetal homopolymer PTFE

0.64 0.50 0.52 0.50 0.50 0.30 0.27 0.29 0.20

0.64 0.55 0.59 0.56 0.48 0.32 0.31 0.32 0.26

0.59 0.53 0.50 0.53 0.52 0.35 0.33 0.35 0.27

2

β b

Wear, mils per 10 min

b

8.0 >15 >15 >15 3.7 3.3 5.2 2.6 1.5

Flat test block, 15-lb load. Flat test block, 90-lb load.

P S S is resistant to m a n y o r g a n i c solvents. T e n s i l e specimens exposed at 200° F f o r 24 h o u r s w e r e unaffected b y h y d r o c a r b o n s , alcohols, ketones, esters, ethers, a n d o r g a n i c acids. U n d e r these c o n d i t i o n s some c h l o r i n a t e d solvents a n d n i t r o g e n c o m p o u n d s s l o w l y attack t h e p o l y m e r w h i l e others d o not. C o n c e n t r a t e d i n o r g a n i c acids ( 9 6 % s u l f u r i c ) a n d s t r o n g o x i d i z i n g


15.

HILL, JR. E T A L .

Polyphenylene

155

Sulfide

agents ( c h r o m i c a c i d a n d s o d i u m h y p o c h l o r i t e ) attack P P S w h i l e w e a k e r acids ( 3 0 %

s u l f u r i c ) a n d strong bases d o not.

W h e n compared

with

other p o l y m e r s exposed u n d e r t h e same c o n d i t i o n s ( T a b l e V ) , P P S is resistant to a greater v a r i e t y of c h e m i c a l e n v i r o n m e n t s t h a n most t h e r moplastics. Table V .

Chemical Resistance ( 2 0 0 ° F , 24 hours)


Tensile

30% H S0 30% NaOH Acetic anhydride E t h y l e n e chloride Toluene A m y l alcohol M e t h y l e t h y l ketone Pyridine 2

Modified Phenylene Oxide

Polycarbonate

Reagent 4

Compression Molding Preparation.

Retained,

102 102 55 0 0 62 0 0

101 0 0 0 0 48 0 0

%

Polysulfone

PPS 101 114 100 72 98 102 112 93

105 101 0 0 0 48 0 0

Compounds

F o r c o m p r e s s i o n m o l d i n g , as w i t h i n j e c t i o n m o l d i n g ,

v a r i o u s t h e r m a l l y stable m a t e r i a l s h a v e b e e n u s e d for cases c o m p r e s s i o n m o l d i n g c o m p o u n d s t h a n the i n j e c t i o n m o l d i n g c o m p o u n d s .

fillers.

I n most

c o n t a i n h i g h e r l o a d i n g of

filler

Compression molding compounds

are p r e p a r e d b y b l e n d i n g the u n c u r e d p o l y m e r w i t h the d e s i r e d

filler.

T h e u n c u r e d p o l y m e r has a l o w m e l t v i s c o s i t y a n d tends to w e t t h e filler

better t h a n the m o r e viscous c u r e d m a t e r i a l u s e d i n the i n j e c t i o n

m o l d i n g blends.

S t a n d a r d m i x i n g e q u i p m e n t s u c h as H e n s c h e l m i x e r ,

d r u m t u m b l e r s , W a r i n g b l e n d e r , a n d other i n t e n s i v e mixers c a n b e u s e d f o r most

fillers.

T h e most i m p o r t a n t considerations i n b l e n d i n g are t h a t

t h e filler p a r t i c l e s are u n i f o r m l y d i s t r i b u t e d t h r o u g h o u t the m i x t u r e a n d t h o r o u g h l y c o a t e d w i t h the P P S p o w d e r .

F o r glass fibers l o n g e r t h a n

1/32 inch, special equipment a n d techniques are required for good blends. G l a s s w i t h l o n g e r fibers is difficult to separate p r o p e r l y a n d to o b t a i n t h o r o u g h c o a t i n g of t h e i n d i v i d u a l

fibers.

B o t h filled a n d u n f i l l e d P P S m u s t be h i g h l y c u r e d to r e d u c e the m e l t flow

p r i o r to its use as a c o m p r e s s i o n m o l d i n g c o m p o u n d .

C u r i n g can

b e d o n e b y e x p o s i n g the m i x t u r e to a i r at e l e v a t e d temperatures. t i m e a n d t e m p e r a t u r e u s e d are c o n t r o l l e d b y the b u l k d e n s i t y of

The the

m i x t u r e . C o m p o u n d s of l o w b u l k d e n s i t y s u c h as those of h i g h asbestos content c a n be c u r e d sufficiently i n 1 h r at 700° F i n a n a i r - c i r c u l a t i n g oven.

C o m p o u n d s c o n t a i n i n g short glass fiber a n d of i n t e r m e d i a t e b u l k


156

FILLERS

AND

REINFORCEMENTS

FOR

PLASTICS

d e n s i t y r e q u i r e s e v e r a l h o u r s c u r e at 550° F a n d t h e n 1 h r c u r e at 7 0 0 ° F . U n f i l l e d P P S a n d b l e n d s w i t h p o w d e r s or p i g m e n t s are u s u a l l y c u r e d 16 h o u r s at 5 1 0 ° - 5 4 0 ° F a n d t h e n 1 h r at 7 0 0 ° F .

T h e cure b e l o w the

m e l t p o i n t of h i g h b u l k d e n s i t y b l e n d s is r e q u i r e d to increase t h e m e l t viscosity.

T h i s p r e v e n t s p u d d l i n g a n d a l l o w s a i r to contact t h e P P S

t h r o u g h o u t the entire m i x t u r e d u r i n g t h e 700° F c ur e .


Table V I .

Properties of Compression Molded PPS Compounds 60/40" PPS/ Fybex

60/40" PPS/ Asbestos

60/40" PPS/ Glass

10,700 8,300 3,200 2,200

11,000 8,000 4,000 2,400

8,400 6,600 4,000 2,200

4,800 4,200 600

1,200 1,200 190 100

1,200 1,000 340 180

1,200 1,100 240 120

420 370 10

Flexural strength, psi 75°F 175°F 275°F 400°F

13,680 10,420 6,110 3,070

11,190 8,940 3,520

13,790 12,240 4,780 3,560

9,000 8,600

Compression strength, psi 75°F 175°F 275°F 400°F

21,700 18,800 16,300 8,800

21,000 19,000 15,000 9,000

20,500 17,200 13,800 7,100

14,900 10,600

Tensile, psi 75°F 175°F 275°F 400°F Flexural modulus, psi X 1 0 75°F 175°F 275°F 400°F

PPS

3

T h e r m a l expansion, i n c h / i n c h / ° F X 10~ 75°-200°F 200°-300°F 300°-400°F

6 6

5

2.0 3.5 5.5

2.0 4.2 6.9

2.0 3.0 6.1

" Parts by weight. Ductile, showed no yield point or break. 6

C u r i n g is u s u a l l y d o n e b y p l a c i n g t h e b l e n d e d m a t e r i a l i n a n o p e n t o p p e d p a n at d e p t h s of % to 2 inches. C o m p o u n d s of l o w b u l k d e n s i t y c a n b e c u r e d w i t h b e d d e p t h s u p to 2 i n c h e s w h i l e p o w d e r b l e n d s a n d u n f i l l e d P P S of h i g h b u l k d e n s i t y s h o u l d b e c u r e d at a p p r o x i m a t e l y V2 inch.

T h e c u r e d m a t e r i a l u s u a l l y forms a sheet o r s o l i d mass s l i g h t l y


15.

HILL, JR. E T A L .

Polyphenylene

157

Sulfide

m o r e c o m p a c t t h a n t h e u n c u r e d m a t e r i a l . T h i s mass r e q u i r e s g r a n u l a t i n g to p a r t i c l e s a p p r o x i m a t e l y % i n c h i n d i a m e t e r before m o l d i n g . M o l d s w h i c h c a n w i t h s t a n d pressures of

Molding Procedure.

4000

p s i at 750° F are r e q u i r e d for c o m p r e s s i o n m o l d i n g P P S c o m p o u n d s .

In

most cases steel m o l d s h a v e b e e n used. T o p r e v e n t s t i c k i n g a n d to i m p r o v e the p a r t finish, the m o l d s h o u l d b e c l e a n a n d c o a t e d w i t h a m o l d release.

T h e p r e p a r e d m o l d is filled w i t h m o l d i n g c o m p o u n d a n d c o l d

pressed at 2 0 0 0 - 3 0 0 0 p s i pressure.

T h e filled m o l d is t h e n h e a t e d u n t i l


a m i n i m u m t e m p e r a t u r e of 600° F i n the m o l d is r e a c h e d . r e q u i r e s f r o m 1 to 3 hours i n a 6 5 0 ° - 7 5 0 ° F o v e n .

This usually

T h e hot m o l d is t h e n

p l a c e d i n a press a n d subjected to 1000 to 4000 p s i pressure, t h i c k e r parts r e q u i r i n g the h i g h e r pressures. C o n t r o l l e d c o o l i n g is r e q u i r e d to p r e v e n t v o i d s or c r a c k i n g of large parts. A m a x i m u m c o o l i n g rate of a p p r o x i m a t e l y 4 ° F / m i n m u s t b e h e l d u n t i l the t e m p e r a t u r e is b e l o w 4 5 0 ° F .

The

p a r t c a n b e r e m o v e d f r o m the m o l d after the t e m p e r a t u r e reaches 3 0 0 ° F . T h i s t e c h n i q u e has been u s e d to m o l d rods, tubes, slabs, a n d p r e f o r m s w h i c h o n l y r e q u i r e d s l i g h t m a c h i n i n g for Properties.

T h e compression

finished,

close-tolerance parts.

molded compounds

containing 4 0 %

asbestos, glass fiber or F y b e x d i s p l a y a s u b s t a n t i a l increase i n m e c h a n i c a l properties over the u n f i l l e d r e s i n as s h o w n i n T a b l e V I . T h e p r o p e r t i e s of the filled c o m p o u n d s

are s i m i l a r over the t e m p e r a t u r e range s h o w n ,

a n d c o n s e q u e n t l y the fillers a p p e a r e q u a l w i t h respect to p r o p e r t i e s i m p a r t e d to the c o m p o u n d s . compounds

T h e properties of the c o m p r e s s i o n

are w e l l b e l o w those of the 4 0 %

molding compound.

molded

glass r e i n f o r c e d i n j e c t i o n

T h e difference i n properties is a t t r i b u t e d to the l o w

c r y s t a l l i n i t y of the h i g h l y c u r e d c o m p r e s s i o n m o l d i n g r e s i n as i n d i c a t e d b y the l o w heat of f u s i o n b y D T A . L i n e a r coefficient of expansion of these c o m p o u n d s is l o w a n d constant f r o m 75° F to 200 ° F , the glass t r a n s i t i o n . A b o v e 200° F the coefficient of e x p a n s i o n g r a d u a l l y increases w i t h i n c r e a s ing temperature.

Applications I n s u m m a r y , p o l y p h e n y l e n e sulfide c o m p o u n d s

offer a c o m b i n a t i o n

of d e s i r a b l e properties s u c h as g o o d t h e r m a l s t a b i l i t y , o u t s t a n d i n g c h e m i c a l resistance, l o w coefficient of f r i c t i o n , excellent e l e c t r i c a l p r o p e r t i e s , and precision moldability.

These

properties

a v a i l a b l e to m a n y other p l a s t i c m a t e r i a l s .

l e a d to a p p l i c a t i o n s

F o r example, a number

not of

p u m p m a n u f a c t u r e r s are u s i n g P P S c o m p o u n d s as s l i d i n g vanes, i m p e l l e r cases, gage guards, a n d seals i n corrosive service i n v o l v i n g materials s u c h as 6 0 % s u l f u r i c a c i d , l i q u i d a m m o n i a , a n d v a r i o u s h y d r o c a r b o n streams. P o l y p h e n y l e n e sulfide c o m p o u n d s w i t h l o w f r i c t i o n a n d l o w w e a r p r o p erties h a v e b e e n e v a l u a t e d as cages for n o n - l u b r i c a t e d b a l l bearings at


158

FILLERS A N D REINFORCEMENTS FOR PLASTICS

3 5 0 ° F a n d 5 0 p s i load. These materials have operated longer than 6 0 0 hrs w h i l e o t h e r m a t e r i a l s f a i l i n less t h a n 2 0 hrs.

I n another type of

application, electrical properties a n d t h e ability to injection m o l d very s m a l l parts w i t h great p r e c i s i o n h a v e l e d t o the use o f a v a r i e t y o f c o n nectors, c o i l f o r m s , etc., i n t h e electronics i n d u s t r y . I n a n o t h e r a p p l i c a t i o n a 1 0 . 5 - i n c h d i a m e t e r p i s t o n f o r a n o n - l u b r i c a t e d gas c o m p r e s s o r has b e e n i n service a t 1 0 0 0 r p m f o r over 6 m o n t h s a n d is p e r f o r m i n g better than the a l u m i n u m piston it replaced.

This piston was machined from

a 3 5 - l b c o m p r e s s i o n m o l d e d b l o c k o f P P S . I n a d d i t i o n t o these uses f o r


v a r i o u s m o l d e d parts,

filled

p o l y p h e n y l e n e sulfide coatings a r e

finding

u t i l i t y as release coatings for c o o k w a r e a n d as c o r r o s i o n resistant coatings f o r the c h e m i c a l a n d p e t r o l e u m i n d u s t r i e s .

Literature Cited 1. Hill, H. Wayne, Jr., Edmonds, J. T., Jr., Preprints, Amer. Chem. Soc., Div. Org. Coatings Plastics Chem. (1970) 30 (2) 199. 2. Short, J. N., Hill, H. Wayne, Jr., ChemTech (1972) 2, 481. 3. Hill, H. Wayne, Jr., Edmonds, J. T., Jr., Preprints, Amer. Chem. Soc., Div. Polym. Chem. (1972) 13 (1) 603. 4. Hill, H. Wayne, Jr. et al., ADVAN. CHEM. SER. (1973) 129, 80. RECEIVED October 11, 1973.


Properties of Filled Polyphenylene Sulfide Compositions

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