Fillers and Reinforcements for Plastics

18 Hydrated Alumina as a Fire-Retardant Filler

Downloaded via TUFTS UNIV on July 11, 2018 at 17:11:21 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

in Styrene-Polyester Casting Compounds C. V .

LUNDBERG

Bell Laboratories, M u r r a y Hill, N . J. 07974

Hydrated alumina is an effectivefire-retardantfillerfor styrene-polyester casting compounds. When equivalent volume loadings of hydrated alumina are used in place of silica and feldspar, self-extinguishing compounds are ob tained when tested in accordance with ASTM D 635 in contrast to the combustible silica and feldspar compounds. The hydrated alumina compounds have oxygen index values ranging from 25 to 31, depending on the amount of filler present, compared with 20 for the silica and feldspar com pounds and 21 to 22 for the latter compounds modified with 1.5 phr of antimony trioxide and 2.5 phr of chlorinated paraffin.

'T'he

w o r k d e s c r i b e d here w a s started a b o u t three years a g o w h e n

a n t i m o n y t r i o x i d e , w h i c h is u s e d as a fire r e t a r d a n t i n s t y r e n e - p o l y ester c a s t i n g c o m p o u n d s ,

w a s i n short s u p p l y a n d its p r i c e

f r o m 5 0 0 / l b to m o r e t h a n $ 2 . 0 0 / l b .

increased

E v e n at this p r i c e , s u p p l i e r s w e r e

a l l o c a t i n g i t . O n e reason f o r t h e short s u p p l y , a n d p o s s i b l y t h e m a i n one, w a s that designers o f p l a s t i c parts h a d b e c o m e anxious to b u i l d flame

retardance into their products, a n d the d e m a n d for antimony t r i -

oxide rose r a p i d l y a n d e x c e e d e d the s u p p l y . A s t h e p r i c e i n c r e a s e d , other, p r o b a b l y less d e s i r a b l e flame retardants w e r e a d o p t e d .

T h e supply at

t h e mines i n c r e a s e d , a n d the p r i c e d r o p p e d so t h a t t o d a y i t is a b o u t 80fS/lb. W i t h the N i x o n a d m i n i s t r a t i o n ' s p o l i c y o f friendliness a n d trade w i t h m a i n l a n d C h i n a , a shortage o f a n t i m o n y t r i o x i d e m a y n o t o c c u r a g a i n . C h i n a is a source w h i c h has n o t b e e n t a p p e d r e c e n t l y f o r p o l i t i c a l r e a sons b u t w h i c h s h o u l d o p e n u p i f t h e n e e d arises. H o w e v e r , a n t i m o n y t r i o x i d e , S b 0 , often c a l l e d a n t i m o n y oxide, is s t i l l a n expensive m a 2

3

t e r i a l v o l u m e w i s e since i t has a specific g r a v i t y o f 5.7. T h u s , at 8 0 ^ / l b 184 Deanin and Schott; Fillers and Reinforcements for Plastics Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

18.

LUNDBERG

Hydrated

185

Alumina

i t has a p o u n d - v o l u m e cost of $4.56. T h i s compares w i t h p o u n d - v o l u m e costs of 360 f o r c h l o r i n a t e d paraffin, 220 for s t y r e n e - p o l y e s t e r r e s i n , a n d 40 or less for m i n e r a l fillers s u c h as f e l d s p a r a n d s i l i c a .

Pound-volume

cost is the p r o d u c t of t h e cost p e r p o u n d a n d the specific g r a v i t y .

It

relates the cost to the v o l u m e ; the denser the m a t e r i a l , the less v o l u m e one p o u n d of it w i l l o c c u p y . T h e o x y g e n i n d e x test has b e c o m e w i d e l y u s e d i n recent years to rate the

flammability

of plastics. O x y g e n i n d e x is defined i n A S T M

D

2863 as " 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 , expressed as p e r c e n t b y v o l u m e , i n a m i x t u r e of o x y g e n a n d n i t r o g e n w h i c h w i l l just s u p p o r t c o m b u s t i o n of a m a t e r i a l u n d e r c o n d i t i o n s of this m e t h o d . " T h i s test is often r e f e r r e d to as the c a n d l e test since the s p e c i m e n is i g n i t e d at its u p p e r e n d s i m i l a r to a c a n d l e . T h e o x y g e n i n d e x test gives a n u m e r i c a l v a l u e w h i c h c a n b e d u p l i c a t e d f a i r l y closely f r o m t i m e to t i m e i n a g i v e n l a b o r a t o r y a n d b e t w e e n laboratories. A n o x y g e n i n d e x of 28 has b e e n a d o p t e d as the d e s i r a b l e m i n i m u m s t a n d a r d i n our laboratories. H o w e v e r , n o s i n g l e test is satisf a c t o r y for e s t a b l i s h i n g the

flame

r e t a r d a n c e of m a t e r i a l s u n d e r

the

v a r i a b l e c o n d i t i o n s of a n a c t u a l fire. T h e use of 1.5 parts p e r h u n d r e d of r e s i n ( p h r ) of a n t i m o n y t r i o x i d e together w i t h 2.5 p h r of c h l o r i n a t e d paraffin as a

fire-retardant

system

for silica-filled s t y r e n e - p o l y e s t e r c a s t i n g c o m p o u n d s w a s a d o p t e d at B e l l L a b o r a t o r i e s i n 1963. Tests at that t i m e w e r e r u n o n cast b l o c k s m e a s u r i n g 3^4 i n c h X W2 i n c h X 1 i n c h , w h i c h w e r e s i m i l a r i n size a n d shape to 3 A 1 A - 3 p r o t e c t o r b l o c k s ( a p p a r a t u s w h i c h protects t e l e p h o n e e q u i p ment from electrical overloads).

T h i s protector b l o c k , m a d e w i t h the

s t a n d a r d s t y r e n e - p o l y e s t e r c a s t i n g c o m p o u n d i n use at that t i m e , f a i l e d to m e e t the U n d e r w r i t e r s ' L a b o r a t o r i e s

flammability

requirement.

The

a d d i t i o n of 1.5 p h r of a n t i m o n y t r i o x i d e a n d 2.5 p h r of c h l o r i n a t e d paraffin r e s u l t e d i n a p r o t e c t o r b l o c k flame persistence of 18 seconds, w e l l w i t h i n the 60 seconds r e q u i r e d b y U n d e r w r i t e r s . T h e i r test is p e r f o r m e d

by

a p p l y i n g to t h e b o t t o m of a v e r t i c a l s p e c i m e n , at a n angle of 2 0 ° to the h o r i z o n t a l , a flame 5 inches h i g h w i t h a 1 % - i n c h b l u e cone, for

five

p e r i o d s of 15 seconds d u r a t i o n w i t h 15-second i n t e r v a l s . T h e a n t i m o n y t r i o x i d e - c h l o r i n a t e d paraffin

fire-retardant

system w a s later a d o p t e d for

use i n v i r t u a l l y a l l B e l l S y s t e m s t y r e n e - p o l y e s t e r c a s t i n g c o m p o u n d s . W h e n the o x y g e n i n d e x test b e c a m e a v a i l a b l e , the s t y r e n e - p o l y e s t e r c o m p o u n d s w i t h a flame persistence of 60 seconds or less i n the U n d e r w r i t e r s ' test, h a d o x y g e n i n d i c e s of 21 to 22, s l i g h t l y a b o v e t h e p e r c e n t o x y g e n i n a i r ( 2 0 . 9 5 ) . T h e s e c o m p o u n d s c o n t a i n e d 1.5 p h r of a n t i m o n y t r i o x i d e a n d 2.5 p h r of c h l o r i n a t e d paraffin. T h u s , c o m p o u n d m o d i f i c a tions seemed necessary to m e e t the r e q u i r e d o x y g e n i n d e x m i n i m u m of 28.

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

186

FILLERS

AND

REINFORCEMENTS FOR

PLASTICS

H y d r a t e d a l u m i n a has b e e n m e n t i o n e d i n the l i t e r a t u r e at v a r i o u s times as a fire-retardant filler for r u b b e r s a n d plastics. T h o m p s o n , H a g m a n , a n d M u e l l e r ( I ) i n 1958 a n d r e c e n t l y M c C o r m a c k (2) its effect i n neoprene c o m p o u n d s .

r e p o r t e d o n its effect i n e p o x y c o m p o u n d s . literature

reports

a l u m i n a as a

we

decided

fire-retardant

Compound and Specimen

filler

reported on

M a r t i n a n d P r i c e ( 3 ) a n d Stevens to

O n the basis of

investigate

the

use

i n styrene-polyester casting

(4)

favorable

of

hydrated compounds.

Preparation

C o m p o u n d s w e r e p r e p a r e d i n f o r m u l a - w e i g h t or h a l f - f o r m u l a - w e i g h t batches b a s e d o n a f o r m u l a u s i n g 100 grams of r e s i n . M i x i n g w a s d o n e b y h a n d i n 8-ounce p o l y e t h y l e n e - l i n e d p a p e r cups. T h e c o m p o u n d s m i n u s t h e i n i t i a t o r a n d accelerator w e r e e v a c u a t e d at 3 m m of m e r c u r y , a n d B r o o k f i e l d viscosities w e r e r u n w h e r e a p p r o p r i a t e . I n i t i a t o r a n d a c c e l erator w e r e a d d e d , the m a t e r i a l w a s a g a i n degassed at 3 m m of m e r c u r y a n d t h e n cast i n a T e f l o n - f a c e d m o l d to a thickness of Vs i n c h . T h i c k e r specimens ( < ~ % i n c h ) w e r e cast i n a l u m i n u m dishes w i t h stainless steel electrodes for i n s u l a t i o n resistance tests. S p e c i m e n s w e r e g e l l e d for 2 h o u r s at 1 2 5 ° F a n d c u r e d f o r 2 h o u r s at 2 5 0 ° F . T h e c u r e d V s - i n c h t h i c k sheets w e r e c u t to size for the v a r i o u s tests. Table I.

Filler Properties Feldspar 200 Mesh

Chemical Analysis, % loss o n i g n i t i o n silica, S i 0 alumina, A 1 0 i r o n oxide, F e 0 c a l c i u m oxide, C a O m a g n e s i u m oxide, M g O s o d i u m oxide, N a 0 p o t a s s i u m oxide, K 0 Screen T e s t , % o n 100 m e s h o n 200 o n 325 t h r u 325 2

2

3

2

3

2

2

α

0.2 71.5 16.3 0.08 m a x . 0.4 trace 4.0 7.5 0.1 0.2 2.8 96.7

Silica 200 Mesh

—

Hydrated" Alumina

—

99.8

—

0.03 m a x .

0.022 64.9 0.034

— — — —

4 9 80

— —

0.22

—

—

—

1-3 15-20 80-85

C-30BF alumina trihydrate, Alcoa.

Discussion T h e first s t y r e n e - p o l y e s t e r c o m p o u n d m a d e w i t h h y d r a t e d a l u m i n a h a d a m e a s u r e d o x y g e n i n d e x of 26.4 c o m p a r e d w i t h a s i l i c a - a n t i m o n y t r i o x i d e - c h l o r i n a t e d paraffin c o n t r o l of 22.8, b u t i t w a s m o r e than the control.

viscous

T h e p a r t i c u l a r h y d r a t e d a l u m i n a u s e d has a screen

analysis s h o w i n g 9 9 %

t h r o u g h a 325-mesh screen.

A second

grade


of

18.

Hydrated

LUNDBERG

187

Alumina

7Θ0 —

UJ

o:

3 < ce

Lu Û_ 600 S

500

Figure 1. Differential thermal analysis of C-30BF alumina trihydrate (Al 0 -3 H 0). Scan speed, 40°C/min; range, 64 (in nitrogen). 2

3

2

h y d r a t e d a l u m i n a w i t h a screen analysis of 3 - 1 5 % screen w a s t h e n t r i e d .

26.0 a n d 25.4 for c o m p o u n d s paraffin, r e s p e c t i v e l y .

t h r o u g h a 325-mesh

T h e r e s u l t i n g c o m p o u n d s h a d o x y g e n i n d i c e s of w i t h a n d w i t h o u t 2.5 p h r of c h l o r i n a t e d

E v e n t h o u g h this h y d r a t e d a l u m i n a is r o u g h e r

i n p a r t i c l e size t h a n the first, i t s t i l l r e s u l t e d i n c o m p o u n d s cosities greater t h a n that of t h e s i l i c a c o n t r o l for e q u a l

w i t h vis-

filler

volume

loadings. A

t h i r d h y d r a t e d a l u m i n a r e s u l t e d i n f a v o r a b l e viscosities

even

t h o u g h its sieve analysis s h o w e d t h a t it h a d finer p a r t i c l e size t h a n the s e c o n d c o m p o u n d a n d its o i l a b s o r p t i o n ( A S T M D - 2 8 1 ) w a s close to that of the other t w o . A l l three h y d r a t e d a l u m i n a s are m a d e b y the B a y e r process.

T h e t h i r d contains a h i g h e r i r o n content a n d thus is less w h i t e

t h a n the others.

T a b l e I shows some of the properties of the t h i r d h y -

d r a t e d a l u m i n a ( C - 3 0 B F a l u m i n a t r i h y d r a t e , A L C O A ) , the one selected for the w o r k d e s c r i b e d b e l o w ,

a l o n g w i t h s i m i l a r properties f o r

the

200-mesh f e l d s p a r a n d the 200-mesh s i l i c a u s e d for c o m p a r a t i v e purposes.


188

FILLERS A N D REINFORCEMENTS FOR PLASTICS

F i g u r e 1 shows a d i f f e r e n t i a l t h e r m a l analysis ( D T A ) scan for the C - 3 0 B F a l u m i n a t r i h y d r a t e . S o m e s l i g h t e n d o t h e r m occurs at 2 7 0 ° C , b u t the significant e n d o t h e r m is c e n t e r e d at 346 ° C w h e n p r e s u m a b l y w a t e r is released.

T h e c o o l i n g effect associated w i t h the c h e m i c a l c h a n g e is

r e s p o n s i b l e for the

fire-retardant

p r o p e r t y of h y d r a t e d a l u m i n a .

DTA

scans for f e l d s p a r a n d s i l i c a s h o w no s i m i l a r endotherms. T a b l e I I shows d a t a c o l l e c t e d e a r l y i n this i n v e s t i g a t i o n u s i n g ( 1 ) a compound

c o n t a i n i n g 80 p h r of f e l d s p a r p l u s fire r e t a r d a n t s ; ( 2 )

the

same c o m p o u n d w i t h h y d r a t e d a l u m i n a s u b s t i t u t e d for the f e l d s p a r o n a n e q u a l - v o l u m e basis a n d no a d d e d fire r e t a r d a n t s ; ( 3 ) c o n t a i n i n g 100 p h r of s i l i c a p l u s fire r e t a r d a n t s ; a n d ( 4 )

a

compound

the same

com

p o u n d w i t h h y d r a t e d a l u m i n a s u b s t i t u t e d for the s i l i c a o n a n e q u a l volume

basis

a n d no

added

fire

retardants.

The

hydrated alumina

c o m p o u n d s h a v e o x y g e n i n d i c e s 3.7 to 5.3 points h i g h e r t h a n t h e a n t i m o n y t r i o x i d e - c h l o r i n a t e d paraffin c o m p o u n d s b u t s t i l l less t h a n 2 8 — t h e d e s i r e d minimum. Table I I .

Compounds Containing E q u a l Volume Loadings of Fillers Parts by Weight

Styrene-polyester resin F e l d s p a r , 200 m e s h Silica Hydrated alumina F i b e r g l a s s , 1/32 inch T i t a n i u m dioxide Silicone a n t i f o a m Cumene hydro peroxide C o b a l t octoate Sb 0 Chlor. par. (solid) Chlor. par. (liquid) α

2

3

6

6

Oxygen index α

c d

Τ

V

100 80

100 e

— —

73

e

— —

9.80 0.46 0.05

9.80 0.46 0.05

1.10 0.25 1.50 2.50

1.10 0.25

—

—

21.4

W

υ

— —

25.1

100 100

—

100

d

—

91

— —

d

2.50

2.50

0.05

0.05

1.10 0.25 1.50

1.10 0.25

—

—

— —

—

—

2.50 21.1

26.4

Propylene-maleate-phthalate resin, 34.5% styrène. Contains 70% chlorine. These quantities represent approximately equal volume loadings. These quantities represent equal volume loadings.

A b o u t the t i m e that the a b o v e d a t a w e r e o b t a i n e d , t h e styrene c o n tent of the s t y r e n e - p o l y e s t e r r e s i n w a s i n c r e a s e d f r o m 3 4 . 5 %

to

38%.

T h i s r e s i n c h a n g e p e r m i t t e d a n increase of the f e l d s p a r filler f r o m 80 to 125 p h r . It thus b e c a m e d e s i r a b l e to o b t a i n the o x y g e n i n d e x of the n e w


18.

LUNDBERG

Hydrated

189

Alumina

25ι24.5

23.9

24

23

23

23

23

4.5 2.5 C

6 2.5 D

1.5 5 F

22.6 χ

Lu α

22

21.8 21.4 21

21

21 =—AIR-

20.6 20.2 20

19 S b 0 , PHR • CHJ.0R . PAR. , PHR COMPOUND NO. • 2

3

1.5 0 1

0 0 Ε

3 0 Κ

0 2.5 J

0 5 L

1.5 2.5 A

3 2.5 Β

3 5 G

4.5 5 H

NOTE: OTHER INGREDIENTS SAME AS IN COMPOUND Ε , TABLE

Figure

2.

Effect of antimony trioxide and chlorinated compound Ε on oxygen index

ΠΙ

paraffin in base

c o m p o u n d a n d to d e t e r m i n e w h e t h e r i n c r e a s e d q u a n t i t i e s of a n t i m o n y t r i o x i d e a n d / o r c h l o r i n a t e d paraffin w o u l d result i n a n o x y g e n i n d e x of 28. D a t a for these c o m p o u n d s are p r e s e n t e d i n F i g u r e 2; the f o r m u l a t i o n of the base c o m p o u n d is s h o w n i n T a b l e I I I . T h e s y n e r g i s t i c effect k n o w n to exist b e t w e e n a n t i m o n y t r i o x i d e a n d c h l o r i n a t e d m a t e r i a l s is o b v i o u s f r o m the b a r graphs. T h e c h l o r i n a t e d paraffin u s e d i n these

compounds

as w e l l as i n other c o m p o u n d s d i s c u s s e d contains 7 0 % c h l o r i n e . Table III.

Base Compound E

a

Parts by Weight Styrene-polyester resin Feldspar F i b e r g l a s s , 1/32 i n c h T i t a n i u m dioxide Cumene hydroperoxide C o b a l t octoate

6

100.0 125.0 5.0 0.5 1.0 0.5

This compound was modified by addition of antimony trioxide and/or paraffin to produce compounds A,B,C,D,F,G,H>I»J'>K>L'Propylene-maleate-phthalate resin, 38% styrene. a

chlorinated

6


190

FILLERS

AND

REINFORCEMENTS FOR

PLASTICS

A t a c o n c e n t r a t i o n of 2.5 p h r of c h l o r i n a t e d paraffin, o x y g e n

index

does not i m p r o v e as the a n t i m o n y t r i o x i d e is i n c r e a s e d a b o v e 4.5 p h r . U s i n g 4.5 p h r of a n t i m o n y t r i o x i d e a n d 5 p h r of c h l o r i n a t e d paraffin, a n o x y g e n i n d e x of 24.5 is o b t a i n e d .

T h e cost of this c o m p o u n d is greater

( 2 1 . 3 0 / l b - v o l ) t h a n that of o n e u s i n g h y d r a t e d a l u m i n a

(20.40/lb-vol;

o x y g e n i n d e x of 2 9 . 4 ) , yet i t does not m e e t the m i n i m u m d e s i r e d o x y g e n i n d e x of 28. I n c r e a s i n g the a m o u n t s of a n t i m o n y t r i o x i d e a n d c h l o r i n a t e d paraffin m a y increase the o x y g e n i n d e x to a n a c c e p t a b l e

l e v e l of 28 or

greater, b u t i t w i l l be at a cost p e n a l t y . A l s o , i n c r e a s i n g the c h l o r i n a t e d paraffin a b o v e 2.5 p h r m a y a d v e r s e l y affect the e l e c t r i c a l a n d c o r r o s i o n properties. 32|31.1

30 29.4

28 27.3

χ

LU Q

26

24

21.8

22

CONTROL FELDSPAR, 125 PHR 1 . 5 S b 0 , 2.5 CHLOR. PAR. COMP N O . - ^ A 2

Figure 3.

112

125

140

HYDRATED ALUMINA, PHR

3

Μ

Oxygen index of styrene-polyester hydrated alumina

0

Q

compounds filled with

F i g u r e 3 is a b a r g r a p h d e p i c t i n g the o x y g e n i n d i c e s of polyester

compounds

feldspar-antimony

filled

with hydrated alumina compared

t r i o x i d e - c h l o r i n a t e d paraffin c o n t r o l .

The

styrenewith

a

formula

tions of these h y d r a t e d a l u m i n a - f i l l e d c o m p o u n d s are s h o w n i n T a b l e I V . T h e 112-phr h y d r a t e d a l u m i n a is e q u i v a l e n t i n v o l u m e to 125 p h r of feldspar.

[ T h e v o l u m e of e a c h equals 46.3 ( w e i g h t i n p h r / s p . gr.


=

18.

Hydrated

LUNDBERG

Table I V .

191

Alumina

H y d r a t e d Alumina-Filled Compounds Parts by Weight

Styrene-polyester resin" Hydrated alumina F i b e r g l a s s , 1/32 i n c h T i t a n i u m dioxide Cumene hydroperoxide C o b a l t octoate Oxygen index α 6

M

0

Q

Y

Ζ

100.0 112.0 5.0 0.5 1.0 0.5

100.0 125.0 5.0 0.5 1.0 0.5

100.0 140.0 5.0 0.5 1.0 0.5

100.0 125.0 2.5

100.0 140.0 2.5

27.3

29.4

31.1

—

—

1.0 0.5

1.0 0.5

>28.

>2S."

6

Propylene-maleate-phthalate resin, 38% styrene. Estimated.

volume).]

The

oxygen

i n d i c e s of

the

compounds

c o n t a i n i n g these

a m o u n t s of fillers are 27.3 for the h y d r a t e d a l u m i n a c o m p o u n d a n d 21.8 for t h e f e l d s p a r - a n t i m o n y t r i o x i d e - c h l o r i n a t e d paraffin c o m p o u n d .

The

viscosity of the 112-phr h y d r a t e d a l u m i n a c o m p o u n d is c o n s i d e r a b l y less t h a n f o r the f e l d s p a r c o m p o u n d so that m o r e h y d r a t e d a l u m i n a c a n be t o l e r a t e d . I n c r e a s i n g the h y d r a t e d a l u m i n a to 125 p h r ( v o l u m e of 51.7) increases the o x y g e n i n d e x to 29.4, a n d i n c r e a s i n g to 140 p h r

(volume

of 57.9) increases the o x y g e n i n d e x to 31.1. T h e v i s c o s i t y of this latter c o m p o u n d is c o m p a r a b l e w i t h t h a t of t h e 125-phr f e l d s p a r c o m p o u n d . T a b l e V compares

flammability

as m e a s u r e d b y the o x y g e n i n d e x

m e t h o d w i t h f l a m m a b i l i t y as m e a s u r e d b y A S T M D 635, " F l a m m a b i l i t y of S e l f - S u p p o r t i n g P l a s t i c s . " I n this test t h e s p e c i m e n ( 5 inches X V2 i n c h Oxygen Index vs. A S T M D 635 Flammability Ratings

Table V .

Com pound A R U V W

c

d

M Ο Q

c

Filler

phr

vol

ASTM D 2863 0 Index

feldspar feldspar feldspar silica hyd. alumina hyd. alumina hyd. alumina hyd. alumina hyd. alumina

80 125 125 100 73 91 112 125 140

29.6 46.3 46.3 37.7 30.2 37.6 46.3 51.7 57.9

21.4 21.8 24.5 21.1 25.1 26.4 27.3 29.4 31.1

Loading Resin 1 2 2 1 1 1 2 2 2

a

2

ASTM D 635 Burning Time, Sec

B u r n s > 180 B u r n s > 180 30 B u r n s > 180 115 45 20 0 0

b

Resins differ only in styrene content: resin 1 contains 34.5% styrene; resin 2 contains 38% styrene. Time for the burning specimen to extinguish after removal of the burner flame from the specimen, officially called "Average Time to Self-Extinguishment." Specimen thick ness 1/8 inch. Contains 1.5 phr S b 0 + 2.5 phr chlorinated paraffin. Contains 4.5 phr S b 0 + 5 phr chlorinated paraffin. α

b

c

d

2

3

2

3


192 X

FILLERS AND R E I N F O R C E M E N T S FOR PLASTICS

V& i n c h ) is s u p p o r t e d i n the h o r i z o n t a l p o s i t i o n w i t h its transverse axis

( w i d t h ) i n c l i n e d at 45° to the h o r i z o n t a l . A 1-inch b l u e B u n s e n b u r n e r flame is a p p l i e d to the free e n d of the s p e c i m e n for 30 seconds. T h e t i m e for the b u r n i n g s p e c i m e n to e x t i n g u i s h after r e m o v a l of the b u r n e r

flame

f r o m the s p e c i m e n is m e a s u r e d i n seconds. I n this test the f e l d s p a r a n d s i l i c a c o m p o u n d s c o n t a i n i n g 1.5 p h r a n t i m o n y t r i o x i d e a n d 2.5 p h r c h l o r i n a t e d paraffin b u r n . compound

I n c r e a s i n g the

flame

retardants i n the

feldspar

to 4.5 a n t i m o n y t r i o x i d e a n d 5 c h l o r i n a t e d paraffin

(Com

p o u n d H ) p r o d u c e s a c o m p o u n d w h i c h extinguishes i n 30 seconds ( o x y g e n i n d e x of 2 4 . 5 ) .

E a c h increase i n the l o a d i n g of h y d r a t e d a l u m i n a

results i n a decrease i n the b u r n i n g t i m e a n d a c o r r e s p o n d i n g

increase

i n the o x y g e n i n d e x . T a b l e V I shows the m e c h a n i c a l properties of the h y d r a t e d a l u m i n a c o m p o u n d s vs. the f e l d s p a r - a n t i m o n y t r i o x i d e - c h l o r i n a t e d paraffin c o n trol.

T h e viscosities p r e v i o u s l y r e f e r r e d to are s h o w n n u m e r i c a l l y .

The

m e c h a n i c a l properties for the f e l d s p a r a n d the three h y d r a t e d a l u m i n a c o m p o u n d s are s i m i l a r . T h e e l e c t r i c a l properties of the h y d r a t e d a l u m i n a c o m p o u n d s are c o m p a r a b l e w i t h those of the f e l d s p a r

compound.

A n i m p o r t a n t c h a r a c t e r i s t i c of a n y filler u s e d i n a l i q u i d system is its settling properties d u r i n g storage of the m i x e d c o m p o u n d processing a n d cure.

before

final

T h e h y d r a t e d a l u m i n a settles m o r e t i g h t l y o n p r o

l o n g e d s t a n d i n g t h a n the f e l d s p a r a n d s i l i c a

fillers.

T h i s m a y not b e a

serious p r o b l e m w h e n the styrene—polyester c o m p o u n d s are m i x e d w h e r e t h e y are u s e d , a n d thus storage t i m e of m i x e d m a t e r i a l is short. Compound Costs T h e costs of the c o m p o u n d s are s h o w n i n T a b l e V I I a n d are b a s e d o n the i n g r e d i e n t prices s h o w n i n T a b l e V I I I . Costs are s h o w n b a s e d o n the F . O . B . prices at the mines or p o i n t of m a n u f a c t u r e . compound Table V I .

The calculated

costs are satisfactory for c o m p a r i s o n b u t m a y not be

exact.

Mechanical Properties of Hydrated A l u m i n a Compounds Compounds Properties

Hydrated alumina, phr V i s c o s i t y , B r o o k f i e l d , cps, N o . 3 spindle, 4 r p m O x y g e n index, % Hardness, Barcol M o d u l u s of r u p t u r e , p s i M o d u l u s of e l a s t i c i t y , p s i Χ Deflection temperature, °C

A (Control)

10

- 6

M

0

Q

15,250

—

112 5,870

125 9,250

140 17,000

21.8 65 9,600 1.58 95

27.3 60 10,200 1.37 96

29.4 62 9,790 1.46 98

31.1 63 9,060 1.52 99


18.

Hydrated

LUNDBERG

193

Alumina

T a b l e VII shows that use of h y d r a t e d a l u m i n a at t h e 125-phr l e v e l ( o x y g e n i n d e x of 29.4) to r e p l a c e

the

compound

p o u n d - v o l u m e cost b y a p p r o x i m a t e l y 5 % . T h e c o r r e s p o n d i n g

feldspar

increases

compound

cost increase w h e n h y d r a t e d a l u m i n a is u s e d to replace s i l i c a is 3 % . A s p r e v i o u s l y n o t e d , i n c r e a s i n g t h e a n t i m o n y t r i o x i d e - c h l o r i n a t e d paraffin to 4.5 a n d 5 p h r , respectively, i n t h e f e l d s p a r c o m p o u n d , pound-volume

cost b y a p p r o x i m a t e l y 1 0 % ; hence, Table V I I .

Compound A H Ο Q

Compound Costs Sp. Gr.

125 p h r feldspar w i t h F . R . 125 p h r feldspar w i t h F . R . 125 p h r h y d r a t e d a l u m i n a 140 p h r h y d r a t e d a l u m i n a

C d

this f e l d s p a r

corn-

α

Cost per Cost per % Incr. lb,i lb-vol, φ over A b

19.4 21.3 20.4 20.1

11.7 12.7 12.8 12.3

1.66 1.68 1.59 1.63

increases t h e

— 9.8 5.2 3.6 % Incr. over U b

U W Y Ζ

100 p h r silica w i t h F . R . 91 p h r h y d r a t e d a l u m i n a 125 p h r h y d r a t e d a l u m i n a 140 p h r h y d r a t e d a l u m i n a C

a 6 c d

12.0 13.5 12.2 11.7

1.57 1.49 1.59 1.62

—

18.8 20.1 19.4 19.0

7 3 1

Without cumene hydroperoxide and cobalt octoate. Cost per lb-vol % increase over A or U . 1.5 phr S b 0 + 2.5 phr chlorinated paraffin. 4.5 phr Sb 03 4- 5 phr chlorinated paraffin. 2

3

2

Table VIII.

Prices of Ingredients Used in Calculating Compound Costs Material

Sp. Gr.

A n t i m o n y trioxide C h l o r i n a t e d paraffin, s o l i d C h l o r i n a t e d paraffin, l i q u i d Fiberglass Styrene-polyester resin T i t a n i u m dioxide F i l l e r s , F . O . B . , bagged, c a r l o a d : hydrated alumina feldspar, 200 m e s h s i l i c a , 200 m e s h

i/lb 79.5 22.5 23.0 66.0 20.5 26.73

5.7 1.66 1.56 2.54 1.10 3.88 2.42 2.70 2.65

φ/'lb-vol 452.3 37.4 35,9 167.7 22.4 104.0 10.77 3.71 2.05

4.45 1.375 0.775

p o u n d is m o r e costly t h a n the h y d r a t e d a l u m i n a c o m p o u n d

w h i c h has

a n o x y g e n i n d e x of 29.4, a n d y e t t h e f e l d s p a r c o m p o u n d has a n o x y g e n i n d e x of o n l y 24.5. T h u s , t h e m o r e expensive results i n a c o m p o u n d

filler—hydrated

alumina—

w i t h a n o x y g e n i n d e x of 28 m i n i m u m a n d at a

l o w e r cost t h a n f o r a f e l d s p a r - a n t i m o n y

t r i o x i d e - c h l o r i n a t e d paraffin

compound.


194

FILLERS A N D REINFORCEMENTS FOR PLASTICS

Safety E m p l o y e e exposure to s i l i c a d u s t c a n result i n silicosis, a disease of the l u n g s .

G o o d ventilation a n d protective equipment are required for

the safe h a n d l i n g o f s i l i c a .

A s i d e f r o m a c o m p a n y ' s h i g h standards f o r

safety a n d h e a l t h , O S H A r e g u l a t i o n s m a y b e c o m e m o r e r e s t r i c t i v e i n t h e f u t u r e w i t h r e g a r d to s i l i c a .

H y d r a t e d a l u m i n a is n o t k n o w n to cause

l u n g illness s i m i l a r to silicosis, a n d i t s u s e r e q u i r e s o n l y t h e n o r m a l p r e c a u t i o n s w h i c h s h o u l d b e f o l l o w e d w h e n h a n d l i n g m i n e r a l dusts. Conclusions T h e use o f a n t i m o n y t r i o x i d e c o m b i n e d w i t h c h l o r i n a t e d paraffin i n styrene-polyester

c a s t i n g c o m p o u n d s does n o t result i n sufficient

flame

r e t a r d a n c e t o h a v e a n o x y g e n i n d e x o f at least 2 8 % a n d s t i l l b e the m o s t economical.

This requirement c a n be met b y using hydrated alumina

as filler i n p l a c e o f m i n e r a l fillers s u c h as f e l d s p a r a n d s i l i c a a n d o m i t t i n g t h e a n t i m o n y t r i o x i d e a n d c h l o r i n a t e d paraffin. c h a n i c a l properties

T h e electrical and m e

of compounds containing hydrated alumina are i n

line w i t h t h e properties

obtained w i t h feldspar a n d silica compounds.

I n c r e a s i n g t h e a n t i m o n y t r i o x i d e a n d c h l o r i n a t e d paraffin a b o v e 1.5 a n d 2.5 p h r , r e s p e c t i v e l y ,

i n feldspar

a n d s i l i c a c o m p o u n d s increases t h e

o x y g e n i n d e x , b u t the m a x i m u m a m o u n t s o f these m a t e r i a l s u s e d i n this s t u d y r e s u l t e d i n a n o x y g e n i n d e x of 2 4 . 5 — c o n s i d e r a b l y sired 2 8 — a n d the pound-volume

below the de

cost o f this c o m p o u n d is h i g h e r t h a n

that of h y d r a t e d a l u m i n a c o m p o u n d s h a v i n g o x y g e n i n d e x values greater t h a n 28. Acknowledgment T h e author thanks E . W . A n d e r s o n a n d R . J . Caroselli for r u n n i n g t h e e l e c t r i c a l tests, a n d F . X . V e n t r i c e f o r r u n n i n g some o f t h e p h y s i c a l tests.

Literature Cited 1. Thompson, D. C., Hagman, J. F., Mueller, Ν. N., Rubber Age (Aug. 1958) 83, 819-824. 2. McCormack, C. E., Rubber Age (June 1972) 104, 27-36. 3. Martin, F. J., Price, K. R., J. Appl. Poly. Sci. (1968) 12, 143. 4. Stevens, J. J. Jr., "Improved Cycloaliphatic Epoxy Systems for High Voltage Applications," Proc. Electrical Insulation Conf. IEEE, 9th (Sept. 10, 1969). RECEIVED October 11, 1973.


Fillers and Reinforcements for Plastics

Recommend Documents