Fillers and Reinforcements for Plastics

4 Asbestos-Reinforced Rigid Poly(vinyl chloride) A. CRUGNOLA and A. M. LITMAN

1

Downloaded by EAST CAROLINA UNIV on January 4, 2018 | http://pubs.acs.org Publication Date: June 1, 1974 | doi: 10.1021/ba-1974-0134.ch004

L o w e l l Technological Institute, L o w e l l , Mass. 01854

Two rigid poly(vinyl chloride) polymers (a low and a high molecular weight sample) were reinforced at several concen trations with four chrysotile asbestos fibers of varying length and openness. Mechanical, thermal, and other physical tests were done on the resultant composites: load/elongation curves, impact, hardness, heat deflection temperature, and flammability. Complete analyses of the before and after processed polymers' molecular weight and molecular weight distribution were also done. X-ray radiographs of the com posites established fiber distribution in the molded speci mens; infrared analyses on the polymers showed possible changes in chemical structure. A new mixing technique incorporated the asbestos in the plastic. Resultant composite properties generally depended on four factors. In decreasing importance they are: (1) matrix polymer molecular weight, (2)fiberconcentration, (3) fiber "openness," (4) fiber length. T i t t l e r e s e a r c h has b e e n d o n e o n t h e r e i n f o r c i n g effects of asbestos o n rigid poly (vinyl chloride)

( P V C ) plastics ( I ) . T h i s c o m b i n a t i o n is

i n t e r e s t i n g because o f t h e i n h e r e n t p r o p e r t i e s of P V C a n d t h e u n i q u e characteristics o f asbestos fibers. R i g i d ( u n p l a s t i c i z e d ) P V C is a l o w cost, t o u g h t h e r m o p l a s t i c n o t e d f o r excellent c h e m i c a l a n d flame resistance a n d extensive p r o c e s s i n g v e r s a t i l i t y — p r o p e r t i e s w h i c h l e a d to countless a p p l i c a t i o n s i n b o t h t h e b u i l d i n g a n d t h e c h e m i c a l areas.

T w o such

p o l y m e r s w e r e u s e d i n this w o r k : a l o w m o l e c u l a r w e i g h t p r o d u c t of M

w

=

49,900 a n d a h i g h m o l e c u l a r w e i g h t p r o d u c t o f M

w

=

116,380.

Asbestos is a b r o a d t e r m a p p l i e d to a n u m b e r of n a t u r a l s i l i c a t e d m i n e r a l s that a r e i n c o m b u s t i b l e a n d c a n b e s e p a r a t e d either m e c h a n i c a l l y o r c h e m i c a l l y i n t o fibers o f v a r y i n g lengths a n d thicknesses.

L o w cost,

Present address: Army Materials and Mechanics Research Center, Watertown, Mass. 02172.

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

30

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

excellent h e a t resistance, a n d e x c e p t i o n a l m e c h a n i c a l b e h a v i o r

account

f o r the g r o w i n g use of asbestos i n t h e r e i n f o r c e d plastics i n d u s t r y . T h e r e are t w o

d i s t i n c t m i n e r a l o g i c a l classifications of

asbestos:

those

from

serpentine r o c k f o r m a t i o n s a n d those f r o m a m p h i b o l e r o c k f o r m a t i o n s . Asbestos

Mineral

— I . Amphibole

Serpentine


Chrysotile

— I Anthophyllite

Amosite

Crocidolite

Tremolite

Actinolite

O f the six varieties c a t a l o g e d o n l y f o u r h a v e c o m m e r c i a l use as r e i n f o r c e m e n t s : c h r y s o t i l e , amosite, a n t h o p h y l i t e , a n d c r o c i d o l i t e .

T h e chrysotile

asbestos accounts for a b o u t 9 5 % of w o r l d p r o d u c t i o n a n d is the m o s t w i d e l y u s e d i n plastics. T h e advantages of this fiber as a r e i n f o r c e m e n t a r e : (1) h i g h e r strength a n d m o d u l u s vs. glass fibers, ( 2 ) a p o s i t i v e s u r face charge w h i c h promotes

fiber/matrix

w i d e r a n g e of lengths a n d d i a m e t e r s , ( 4 )

bonding, (3) a soft,

availability i n a

flexible

results i n m i n i m u m w e a r o n p r o c e s s i n g e q u i p m e n t .

quality w h i c h

T h e four chrysotile

fibers u s e d i n this s t u d y are d e s c r i b e d i n T a b l e I. Table I. Fiber

Asbestos Fibers Used"

Size, inch

7RS7

1/32

Paperbestos N o . 5

3/64

Paperbestos N o . 1

1/4

P l a s t i b e s t N o . 20

1/8-3/16

α

Description s h o r t s t a n d a r d fiber used i n t h e r m o p l a s t i c systems shorter v e r s i o n of Paperbestos No. 1 c l e a n , w e l l opened fiber of good length clean, m e d i u m l e n g t h fiber n o t opened v e r y m u c h

Fibers supplied by Johns Manville Co. and classification/descriptions are theirs.

Experimental Specimen Fabrication. A m e a s u r e d a m o u n t of P V C w a s p l a c e d i n a H e n c h e l m i x e r a n d m i x e d at m a x i m u m s p e e d ( 3600 r p m ) u n t i l the b a t c h t e m p e r a t u r e r e a c h e d 2 0 0 ° F . A t this t e m p e r a t u r e the s t a b i l i z e r w a s a d d e d ( 2 p p h b y w e i g h t of A d v a n c e s ' T - 3 6 0 , a s u l f u r - c o n t a i n i n g o r g a n o t i n c o m p o u n d ) , a n d m i x i n g c o n t i n u e d u n t i l the t e m p e r a t u r e r e a c h e d 2 5 0 ° F ; at this t i m e the m a t e r i a l w a s d i s c h a r g e d i n t o a r i b b o n b l e n d e r for c o o l i n g (approximately 5 m i n ) .

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


4.

CRUGNOLA A N D L i T M A N

Asbestos-Reinforced

PVC

31

Figure 1. Impact fracture surfaces (notched Izod). Top: Paperbestos No. 5/PVC; bottom: Plastibest No. 20/PVC. T h e asbestos w a s d r i e d i n a n o n - c i r c u l a t i n g a i r o v e n at 250° F f o r 24 hrs t o r e m o v e m o i s t u r e that o t h e r w i s e m i g h t p r e v e n t the fiber b u n d l e s f r o m s e p a r a t i n g i n the p r e m i x i n g o p e r a t i o n . T h e b r e a k u p o f t h e asbestos c l u m p s a n d the d r y - b l e n d i n g w i t h the stabilized polymer were done i n a specially designed m i x i n g device consisting o f a glass jar, a b a l l m i l l , a n d a n i t r o g e n source. T h e m i x i n g jar was e q u i p p e d w i t h a p e r f o r a t e d shaft r u n n i n g d o w n i t s l e n g t h w h i c h p e r m i t t e d the n i t r o g e n i n t r o d u c e d u n d e r a n o m i n a l pressure t o b e u n i f o r m l y d i r e c t e d t h r o u g h o u t the jar. A T e f l o n b e a r i n g seated at the center of the jar c o v e r p e r m i t t e d the b o t t l e to t u r n o n t h e b a l l m i l l i n d e p e n d e n t of the shaft. T h e P V C / a s b e s t o s mixtures obtained b y dry-blending were m i l l e d o n a F a r r e l l t w o r o l l m i l l a t 360° ± 5 ° F . S m a l l q u a n t i t i e s ( a p p r o x i m a t e l y 200 grams at the t i m e ) w e r e fluxed o n the 1 5 - i n c h l o n g rolls to



32


ensure t h o r o u g h f u s i o n a n d m i x i n g i n a short t i m e . T h e m i x i n g / f l u x i n g times d e p e n d e d s o m e w h a t o n fiber t y p e a n d content a n d v a r i e d b e t w e e n IV2 a n d 2 m i n . D e s p i t e the short times u s e d , t h e r e w a s n o e v i d e n c e of i n c o m p l e t e f u s i o n e i t h e r d u r i n g f l u x i n g or o n v i e w i n g t h e i m p a c t f r a c t u r e surfaces. T h i s is n o t to say t h a t e v e r y fiber w a s w e t w i t h p o l y m e r w h i c h w e t t i n g i n s t e a d d e p e n d e d o n the d e g r e e of fiber openness. T h i s is v i v i d l y d e m o n s t r a t e d i n the p h o t o g r a p h s of F i g u r e 1. F i n a l l y t h e c o m p o s i t e panels w e r e c o m p r e s s i o n m o l d e d i n a W a b a s h press at 2000 p s i . S e v e r a l sheets f r o m the m i l l i n g o p e r a t i o n w e r e crossp l i e d , p l a c e d i n a n o p e n f r a m e m o l d a n d b r o u g h t to t e m p e r a t u r e ( 3 5 5 ° ± 5 ° F for the h i g h m o l e c u l a r w e i g h t m a t r i x a n d 330° ± 5 ° F for the l o w m o l e c u l a r w e i g h t m a t r i x ) b e f o r e a p p l y i n g pressure. T h e pressure w a s m a i n t a i n e d for 1 m i n hot, t h e n the f r a m e w a s t r a n s f e r r e d to a c o l d press a n d the m a t e r i a l c o o l e d u n d e r the same pressure ( 2000 p s i ). C o m p o s i t e s of e a c h of the f o u r asbestos fibers w e r e f a b r i c a t e d at 15, 30, a n d 4 5 % fiber content i n e a c h of the t w o p o l y ( v i n y l c h l o r i d e ) plastics. Specimen Testing. T h e composites w e r e m e c h a n i c a l l y tested for tensile m o d u l u s , b r e a k i n g e l o n g a t i o n , b r e a k i n g s t r e n g t h , i m p a c t , h a r d ness, a n d heat deflection. A S T M flammability e v a l u a t i o n s w e r e also p e r f o r m e d . T h e effectiveness of t h e s p e c i m e n p r e p a r a t i o n t e c h n i q u e w i t h r e g a r d to the d i s t r i b u t i o n of the fibers w i t h i n t h e c o m p o s i t e w a s estab l i s h e d b y x - r a y r a d i o g r a p h s of selected samples. T h e p o l y m e r / m a t r i x m a t e r i a l s w e r e s t u d i e d b y ( 1 ) g e l p e r m e a t i o n c h r o m a t o g r a p h y to f o l l o w changes i n m o l e c u l a r w e i g h t a n d m o l e c u l a r w e i g h t d i s t r i b u t i o n c a u s e d b y t h e p r o c e s s i n g of the fiber/plastic m i x t u r e s into t h e composites a n d ( 2 ) i n f r a r e d analysis i n a n a t t e m p t to p i c k u p p o s s i b l e changes i n the c h e m i c a l s t r u c t u r e of the p o l y m e r s . Table II. 7RS7 Molecular

Weight

% Asbestos

α

High

Low

— 5.58 6.75 8.25

4.24 5.27 7.82 8.03

High

Low

— 5.47 6.65 8.07

4.24 6.46 6.70 7.28

Fiber

0 15 30 45 6

Tensile Modulus No. δ

6

Strain rate 4 . 5 % / m i n ; variation in values used to obtain average value = =fc 4%. Χ 10+ psi. 6

Results and

Discussion

T h e results of the t e s t i n g d o n e o n the composites

and their com

ponents are p r e s e n t e d i n T a b l e s I I , I I I , I V , V , a n d V I a n d i n F i g u r e s 2, 3, 4, a n d 5. T h e findings are s u m m a r i z e d b e l o w . Tensile Modulus.

I n t r o d u c t i o n of asbestos fiber r a i s e d the m o d u l i

of the P V C plastics. T h e increase g e n e r a l l y i n c r e a s e d w i t h fiber c o n t e n t a n d was as m u c h as 1 0 0 %

at 4 5 % r e i n f o r c e m e n t .

Usually the higher

m o l e c u l a r m a t r i x plastics e x h i b i t e d h i g h e r m o d u l i t h a n the c o r r e s p o n d i n g l o w m o l e c u l a r w e i g h t m a t e r i a l s a l t h o u g h this effect was n o t consistent.


4.

Asbestos-Reinforced

CRUGNOLA AND L I T M A N

33

PVC

N o clear effects of either fiber l e n g t h o r fiber openness w e r e a p p a r e n t i n the results. Tensile Strength. A n increase i n tensile s t r e n g t h w a s g e n e r a l l y n o t e d u p o n the i n i t i a l i n t r o d u c t i o n of asbestos

fibers

i n P V C plastics.

increase p e a k e d , a n d t h e n the s t r e n g t h decreased

This

at t h e h i g h e r

fiber

content levels to the p o i n t w h e r e the r e i n f o r c e d samples e x h i b i t e d b r e a k i n g stresses l o w e r t h a n those of the n o n r e i n f o r c e d m a t e r i a l s . U s u a l l y the h i g h e r m o l e c u l a r w e i g h t m a t r i x composites

showed

somewhat

higher

strengths t h a n d i d the c o r r e s p o n d i n g l o w m o l e c u l a r w e i g h t s p e c i m e n .


T h e reason for the u n e x p e c t e d l o w e r i n g at h i g h e r fiber contents is not c l e a r unless the h i g h e r fiber concentrations b r o u g h t w i t h t h e m a h i g h e r c o n c e n t r a t i o n of i n t e r n a l stress c o n c e n t r a t i n g flaws i n the

compression

m o l d e d sheets. Breaking Strain. A l t h o u g h the n o n r e i n f o r c e d plastics at this strain rate ( 4 . 5 % fibers

p e r m i n u t e ) w e r e p r o n e to n e c k i n g a n d d r a w i n g , o n c e the

w e r e i n t r o d u c e d the b r e a k i n g strains f e l l to a b o u t 2 %

(for

15%

fiber ). F u r t h e r increases i n fiber content f u r t h e r decreased t h e e l o n g a t i o n to b r e a k to levels of the o r d e r of 1 % .

N o c l e a r effect of fiber l e n g t h or

fiber openness w a s seen. I n g e n e r a l , u p to 3 0 % fiber content, the h i g h e r m o l e c u l a r w e i g h t samples e x h i b i t e d s o m e w h a t h i g h e r b r e a k i n g strains. Impact Strength. T h e m o s t i m p o r t a n t f a c t o r i n f l u e n c i n g the i m p a c t strength was the extent to w h i c h the asbestos fibers w e r e o p e n e d . of P V C Asbestos Composites" No. 1

No.

The

20

High

Low

High

Low

— 6.65 6.86 5.57

4.24 5.94 5.54 6.52

— 5.80 6.37 7.53

4.24 5.15 6.20 7.66

c l o s e d fiber structures a l w a y s gave h i g h e r i m p a c t strengths.

Somewhat

h i g h e r strengths w e r e associated w i t h the h i g h e r m o l e c u l a r w e i g h t m a t r i x p l a s t i c , the greater

fiber

concentrations, a n d the l o n g e r

fiber

lengths.

P h o t o g r a p h s of the f r a c t u r e surfaces of a c l o s e d fiber a n d a n o p e n

fiber

r e i n f o r c e d P V C a p p e a r i n F i g u r e 1. T h e s e , w e b e l i e v e , r e v e a l the m e c h a n i s m b y w h i c h t h e n o n - o p e n e d fibers e n h a n c e the i m p a c t s t r e n g t h of the composite.

Considerable energy must be i n v o l v e d i n p u l l i n g apart the

asbestos fibers d u r i n g the i m p a c t — e n e r g y u s e d i n o v e r c o m i n g f r i c t i o n a l forces, i.e., forces r e q u i r e d to p u l l i n d i v i d u a l fibers a w a y a n d past others. O n e m i g h t v i s u a l i z e these forces i n a m o d e l w h e r e a fasces s t r u c t u r e is p u l l e d a p a r t b y g r a s p i n g some of the rods o n one e n d a n d s o m e o n t h e i r


34

FILLERS AND REINFORCEMENTS

Table III.

Tensile Breaking Stress

7RS7 Molecular

Weight

% Asbestos

High

a


No. δ Low

High

Low

4,656 5,251 4,726 4,679

6,256 6,978 7,270 5,734

4,656 5,572 5,889 5,435

Fiber

0 15 30 45 6

6,256 5,756 6,347 5,787

6

Strain rate 4.5%/min; variation in values used to obtain average value = ± Psi.

Table IV.

Molecular

Weight,

% Asbestos 0 15 30 45 α

High

4%.

Tensile Breaking Strain

7RS7

6

FOR PLASTICS

No. δ Low

High

Low

187 2.6 1.8 0.8

67 1.7 1.2 0.9

Fiber 187» 1.2 1.4 0.9

67 2.0 1.2 0.9

Strain rate 4.5%/min. Percent strain.

Table V . Polymer SCC—686* Ο—H—O 1—H—30 7—H—30 b

e

d

Molecular Weight before and after Processing/Molding M

N

56,570 52,730 58,630 46,140

M

w

116,380 129,500 125,700 125,100

M /M W

N

1.98 2.46 2.14 2.71

° Polymer before processing (non-reinforced). Polymer extracted after processing/molding (non-reinforced).

b

Table V I . Polymer SCC—600 Ο—L—Ο 1—L—30 7—L—30 6

e

d

α

Molecular Weight before and after Processing/Molding M

N

23,500 20,320 21,880 22,640

M

w

49,900 48,200 50,340 48,190

M /M W

2.11 2.38 2.30 2.13

° Polymer before processing (non-reinforced). Polymer extracted after processing/molding (non-reinforced).

6


N

4.

Asbestos-Reinforced


of PVC/Asbestos Composites


No. 20

High

Low

6,256 7,343 5,315 3,709

4,656 5,406 4,349 3,748

of P V C Asbestos Composites

High

Low

6,256 6,319 6,423 3,618

4,656 5,508 3,876 4,719

α

No. 1

187 2.4 1.6 0.8

35

0

No. 1

High

PVC

No. 20 Low 67 1.6 1.0 0.7

High

Low

187 2.2 2.1 0.7

67 1.7 1.2 0.9

with Chrysotile Asbestos Fibers for H i g h Molecular Weight P V C M

z

186,600 234,200 219,600 238,300

Mz/Mw 1.61 1.81 1.75 1.91

Mz+i 249,100 350,800 325,000 370,000

Mz+i/Mz 1.30 1.30 1.48 1.56

Polymer extracted after processing/molding reinforced with No. 1 asbestos fibers— 30% fiber content. Polymer extracted after processing/molding reinforced with 7RS7 asbestos fibers— 30% fiber content c

d

with Chrysotile Asbestos Fibers for L o w Molecular Weight P V C Mz 94,120 93,100 94,920 86,620

Mz/Mw 1.88 1.93 1.89 1.79

Mz+i 159,200 148,800 149,800 133,700

Mz+i/Mz 1.69 1.59 1.58 1.54

Polymer extracted after processing/molding reinforced with No. 1 asbestos fibers— 30% fiber content Polymer extracted after processing/molding reinforced with 7RS7 asbestos fibers— 30% fiber content c

d



36


Figure 2.

Variation of impact strength with fiber content (reinforced rigid

other e n d .

T h e extent of this m e c h a n i s m a p p a r e n t l y d e p e n d s

PVC)

o n the

asbestos fiber b u n d l e s not b e i n g t h o r o u g h l y w e t out b y t h e m a t r i x since the better w e t o p e n asbestos fibers are f r a c t u r e d at t h e f r a c t u r e surface of the p o l y m e r . Heat Deflection Temperature.

I n a l l cases the heat deflection t e m -

p e r a t u r e w a s r a i s e d b y the i n t r o d u c t i o n of the asbestos

(6°-12°C

for

the h i g h m o l e c u l a r w e i g h t p l a s t i c a n d 2 ° - 8 ° C for the l o w m o l e c u l a r w e i g h t m a t e r i a l ) . T h i s t e m p e r a t u r e i n c r e a s e d w i t h i n c r e a s i n g fiber c o n -

Figure 3.

Variation of HOT with fiber content (reinforced rigid PVC)


4.

Asbestos-Reinforced


37

PVC

c e n t r a t i o n a n d / o r d e c r e a s i n g fiber openness. T h e m o l e c u l a r w e i g h t o f the s t a r t i n g plastics p r o v e d most i m p o r t a n t i n e s t a b l i s h i n g t h e a m o u n t o f i m p r o v e m e n t i n H D T . W h e r e a s the n o n - r e i n f o r c e d m a t e r i a l s differed b y o n l y 1 ° C the r e i n f o r c e d m a t e r i a l s d i f f e r e d b y as m u c h as 9 ° C . Hardness. T h e asbestos composites consistently s h o w e d l o w e r values of hardness t h a n d i d the n o n - r e i n f o r c e d plastics. T h e l o w e r i n g w a s greater the greater t h e c o n c e n t r a t i o n o f fiber. T h e s o m e w h a t h i g h e r hardness of the s t a r t i n g h i g h e r m o l e c u l a r w e i g h t m a t e r i a l a p p e a r e d t o b e reflected


i n the s o m e w h a t h i g h e r hardness o f t h e h i g h e r m o l e c u l a r w e i g h t c o m -

Figure 4.

Variation of hardness with fiber content (reinforced rigid PVC)

posites. T h e l o w e r i n g o f the hardness w i t h the a d d i t i o n o f asbestos

fibers

m i g h t be e x p l a i n e d o n the basis o f the l o w stiffness o f these fibers. D e s p i t e the f a c t that the fiber has a v e r y h i g h m o d u l u s (ca. 20 X 1 0 p s i vs. 6

10 X 1 0 p s i f o r g l a s s ) , c h r y s o t i l e is also a n asbestos o f finest d i a m e t e r 6

7 Χ 10" i n c h vs. 2.6 Χ 10" i n c h f o r glass. T h e hardness test p r o b a b l y 7

4

subjects the fibers t o b e n d i n g , a n d as s u c h the stiffness ( E I ) d e p e n d s o n the fiber d i a m e t e r as w e l l as the m o d u l u s .

Since t h e asbestos is l o w e r

i n d i a m e t e r b y three orders o f m a g n i t u d e w h i l e o n l y h i g h e r b y a factor of 2 i n m o d u l u s , o n e w o u l d expect to observe l o w e r values o f b e n d i n g stiffness a n d l o w e r hardness. T h e densities o f t w o o f the 3 0 % composites w e r e d e t e r m i n e d , a n d values o f 1.65 a n d 1.58 g r a m s / c m

3

w e r e o b s e r v e d f o r samples 2 0 - H - 3 0

a n d 7-H-30, respectively. These compare favorably w i t h a theoretically c a l c u l a t e d 1.66 g r a m s / c m

3

f o r this fiber content a n d suggest t h a t t h e



38

FILLERS AND REINFORCEMENTS

Figure

5.

Radiographs

of non-reinforced PVC

and

FOR PLASTICS

reinforced

e n t r a p m e n t of a i r i n the c o m p o s i t e is not a significant factor i n the o b s e r v e d hardness l o w e r i n g . Flammability. A l l t h e composites w e r e classified as n o n - b u r n i n g acc o r d i n g to A S T M 635. Fiber Distribution. A s s h o w n b y F i g u r e 5 the a i r m i x i n g t e c h n i q u e w e u s e d r e s u l t e d i n a u n i f o r m d i s p e r s i o n of the fibers i n the plastics. T h i s

Figure 6. Infrared spectra of polymer before and after processing with asbestos. Solid line: stabilized low molecular weight polymer before processing; dashed line: stabilized low molecular weight polymer after processing with No. 1 asbestos.


4.


Asbestos-Reinforced

39

PVC

w a s d o n e w i t h o u t affecting the r e l a t i v e degree of fiber openness

and/or

d a m a g i n g the fiber l e n g t h . Effect of Processing on the Asbestos Fibers. T h e N o . 1 fiber c o m posites w e r e e x a m i n e d f o r fiber d e g r a d a t i o n , a n d fibers d i d not a p p e a r to b e s i g n i f i c a n t l y s h o r t e n e d b y processing.

The microscopic view r e -

v e a l e d that the asbestos b u n d l e s h a d b e e n sheared so as to give rise t o somewhat

t h i n n e r b u n d l e s o f a p p r o x i m a t e l y t h e same

l e n g t h as t h e

original. and Molecular Weight Distribution. M o d i f i c a -

Molecular Weight


tions i n average m o l c u l a r w e i g h t a n d m o l e c u l a r w e i g h t d i s t r i b u t i o n w e r e a c o n s e q u e n c e o f the m i x i n g / p r o c e s s i n g / m o l d i n g c y c l e o f the

asbestos

r e i n f o r c e d P V C plastics. T h e s e modifications w e r e m o r e a p p a r e n t i n the h i g h m o l e c u l a r w e i g h t m a t r i x m a t e r i a l t h a n i n the l o w . I n g e n e r a l , t h e y w e r e n o t m a r k e d l y different w h e n t h e plastics w e r e subjected

to t h e

p r o c e s s i n g / m o l d i n g c y c l e w i t h o u t the i n c l u s i o n o f the asbestos. A s a r u l e , the n u m b e r average m o l e c u l a r w e i g h t i n c r e a s e d , a n d t h e h i g h e r m o l e c u l a r w e i g h t averages i n c r e a s e d . T h i s o f course r e s u l t e d i n a significant increase i n t h e p o l y d i s p e r s i t y o r the broadness o f the m o l e c u l a r w e i g h t d i s t r i b u t i o n . F i n a l l y , a l t h o u g h f u r t h e r c o n f i r m a t i o n is c a l l e d for, t h e results also suggest that t h e N o . 1 fiber ( d e s c r i b e d as c l e a n ) m i n i m i z e s the changes i n m o l e c u l a r w e i g h t a n d m o l e c u l a r w e i g h t d i s t r i b u t i o n u n d e r g o n e b y t i i e p o l y m e r s (see T a b l e s V a n d V I ) . Table VII.

Glass vs. Asbestos-Reinforced Rigid P V C Glass Reinforced 20%

Property Impact strength, f t - l b s / i n notch H e a t deflection t e m p e r a t u r e , °F Density, grams/cm Flammability Tensile strength, psi U l t i m a t e elongation, % R o c k w e l l hardness, M C o s t of fiber 3

1.0-1.6

Asbestos

Reinforced 80%o

15% 1.2

1.4

170-180 176 1.49-1.58 non-burning non-burning 10,000 7,500 1.5-4.0 2.0-1.5 M80-88 M71-93 4.5(é/lb 55-60^/lb

—

176 1.62 7,500

Changes i n Chemical Structure. T h e i n f r a r e d s p e c t r a ( F i g u r e 6 ) s h o w e d several changes i n the p o l y m e r / s t a b i l i z e r c o m b i n a t i o n as a c o n sequence o f p r o c e s s i n g . cm"

1

O n e o f these, the loss o f a n a b s o r p t i o n a t 1550

w a s t i e d to alterations i n the s t a b i l i z e r m o l e c u l e .

i n v o l v e d t h e a p p e a r a n c e o f a b a n d at 1030 c m " . 1

Another change

This would

suggest

reactions l e a d i n g t o the o x i d a t i o n o f the S i n the s u l f u r c o n t a i n i n g o r g a n o t i n s t a b i l i z e r . P l a u s i b l e reactions (2) a r e :


40


0 R S S n —> R S 0 H 3

Ο Sn S R + — C

Ι

ci

>SnCl +

—C

I

> — Ο

I

s

o=s=o

R

R

I

I

T h e p r o p e r t i e s o b t a i n e d i n this s t u d y w e r e c o m p a r e d w i t h those i n


t h e l i t e r a t u r e for glass r e i n f o r c e d r i g i d P V C (3)

(see

Table V I I ) .

The

m e c h a n i c a l a n d t h e r m a l p r o p e r t i e s o b t a i n e d b y r e i n f o r c i n g w i t h the 4.50 asbestos are f u l l y c o m p a r a b l e w i t h those o b t a i n e d w i t h c h o p p e d

glass

fibers. Literature

Cited

1. Cameron, A. B., Heron, G . F., Wicker, G . L., "Asbestos Reinforced Thermo plastics," 28th Ann. Tech. Conf. Reinforced Plastics/Composites, Institute S.P.I. 1973 section 11-B, p. 1. 2. Deanin, R. D . , L o w e l l Technological Institute, private communication. 3. Owens-Corning Fiberglass C o r p . , C o m p o u n d Selector, Jan. 1970. R E C E I V E D October 11,

1973.


Fillers and Reinforcements for Plastics

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