Durability of Macromolecular Materials - American Chemical Society

9 Degradation of Chlorinated Polyethylene: Effect of

Durability of Macromolecular Materials Downloaded from pubs.acs.org by UNIV OF ARIZONA on 10/24/15. For personal use only.

Cross-Linking on Dehydrochlorination ISMAT A. ABU-ISA Polymers Department, General Motors Research Laboratories, Warren, MI 48090

Chlorinated polyethylene (CPE) polymers used in this study are made from high density polyethylene and chlorine gas. Several thermoplastic and elastomeric grades of the polymer are available, having different molecular weights and chlorine content. The elastomeric grades of the polymer contain 36 to 48% chlorine and have only a slight residual crystallinity. The degradation of the polymers prior to crosslinking has been studied by dehydrochlorination and oxygen absorption tech niques [1,2]. The effects of crosslinking and compounding ingredients on the stability of the elastomers have been reported, but only in terms of changes in mechanical and oil swell prop erties [3]. This report deals with the effects of chemical and radiation crosslinking on the rates of dehydrochlorination of CPE with and without stabilizers. Experimental The apparatus used for measuring the rates of dehydrochlo rination of CPE has been described elsewhere [1]. It allows for the volumetric measurement ofHClevolved from the polymer with time at a constant temperature. The CPE material used in this study is CM 0342 supplied by The Dow Chemical Company. This CPE grade has a specific gravity of 1.25, a chlorine content of 42 percent, an average Mooney Viscosity [ML1+4(100°C)] of 65 and a residual crystallinity of less than 2 percent. Molded slabs of the pure and compounded polymer were used. Molding was conducted at 163°C for ten minutes which for most compounds is an optimum cure condition. Samples molded under other conditions will be so noted in the text. For dehydrochlorination measurements the samples were cut into about 2 mm cubes. All chemical crosslinking agents were used as received from the suppliers. These include 2-mercaptoimidazoline (NA-22 Dupont), Ν,Ν'-m-phenylenedimaleimide (HVA-2, Dupont), trimethylol propane trimethacrylate (TMPT, Sartomer), dicumyl peroxide, 40% 0-8412-0485-3/79/47-095-127$05.00/0 © 1979 American Chemical Society

128

MATERIALS

on Burgess c l a y (Dicup 40KE, H e r c u l e s ) , α, α ' - b i s ( t - b u t y l peroxy)diisopropylbenzene, 40% on Burgess c l a y (Vulcup 40KE, Hercules) and e t h y l - 3 , 3 - d i ( t - b u t y l peroxy) butyrate (R233, L u c i d o l ) . A n t i o x i d a n t s used i n t h e study i n c l u d e t e t r a k i s [ m e t h y l e n e - 3 ( 3 , 5 - d i - t - b u t y l - 4 - h y d r o x y p h e n y l ) propionate]methane (Irganox 1010, Ciba Geigy) and d i s t e a r y l t h i o d i p r o p i o n a t e (NONOX DSTDP,ICI). A l l other chemicals were reagent grade chemicals used without further purification. The r a d i a t i o n c u r i n g was performed using a 1.5 MEV e l e c t r o n beam a c c e l e r a t o r made by R a d i a t i o n Dynamics with a maximum c u r r e n t c a p a c i t y o f 15 ma. The CPE s l a b s were i r r a d i a t e d by p l a c i n g them on a motorized c a r t which r a n p a s t the e x i t s l i t o f the a c c e l e r a t o r . The t o t a l r a d i a t i o n exposure was c o n t r o l l e d by v a r y i n g the c a r t speed, the c u r r e n t , and t h e number o f passes. G e n e r a l l y the samples were i r r a d i a t e d a t a c u r r e n t o f 15 ma, and a c a r t speed o f 400 mm p e r second, t o a t o t a l dose o f e i t h e r 10 o r 20 megarads (Mrad). Samples were i r r a d i a t e d i n a i r o r n i t r o g e n atmospheres. 1


DURABILITY O F M A C R O M O L E C U L A R

1

1

Results I n v e s t i g a t i o n o f C r o s s l i n k i n g Systems. C r o s s l i n k i n g o f c h l o r i n a t e d polyethylene was attempted w i t h s e v e r a l conventional and novel systems. These i n c l u d e r a d i a t i o n c u r i n g with and without added c r o s s l i n k i n g coagents such as TMPT, peroxide c u r i n g systems with and without c r o s s l i n k i n g coagents, and other c r o s s l i n k i n g systems such as: a l i c y c l i c amines, p o l y a l c o h o l s , metal oxides, metal s a l t s , 2-mercaptoimidazoline, and dipentamethylenethiuram h e x a s u l f i d e . Most o f the above systems were e l i m i n a t e d from f u r t h e r study, because they e i t h e r degraded t h e CPE or d i d not e f f e c t s u f f i c i e n t c u r i n g o f t h e polymer. The o n l y c r o s s l i n k i n g systems t h a t were i n v e s t i g a t e d and w i l l be d i s c u s s e d i n t h i s r e p o r t are the r a d i a t i o n c r o s s l i n k i n g and c r o s s l i n k i n g by peroxides and NA-22. Dehydrochlorination Measurements During C r o s s l i n k i n g . I n production, CPE i s normally c r o s s l i n k e d ( i . e . , cured) a t a temperature around 175°C i n e i t h e r a c l o s e d compression mold o r i n a h i g h pressure steam autoclave. I n order t o simulate a study of t h e degradation o f the polymer under the above c o n d i t i o n s , CPE was degraded i n a g l a s s apparatus a t 175°C i n a n i t r o g e n atmo sphere. The r a t e s o f d e h y d r o c h l o r i n a t i o n o f t h e pure polymer and the polymer c o n t a i n i n g the chemical c r o s s l i n k i n g agents, i . e . , peroxides and NA-22, were determined. Rates o f dehydrochlo r i n a t i o n d u r i n g r a d i a t i o n c u r i n g were not measured. The r e s u l t s o f t h i s study a r e shown i n F i g u r e 1. Pure CPE, which under above c o n d i t i o n s underwent degradation r e a c t i o n s and very l i t t l e c r o s s l i n k i n g r e s u l t e d i n a maximum r a t e o f dehydro c h l o r i n a t i o n o f 0.117 mg. eq. HCl/g. polymer-hour. Most o f the weight l o s s from the sample a f t e r degradation can be accounted

Degradation

of Chlorinated

Polyethylene

129


9. ABu-iSA

0

1

2 Time in Hours

3

4

Figure 1. Dehydrochlorination (175°C, N ) during cross-linking of CPE compounds containing: (1) control; (2) 5 phr Dicup; (3) 5 phr Dicup + 2 phr ZnO; (4) 5 phr Dicup + 6 phr TMPT; (5) phr Dicup 4- 3 phr HVA-2; (6) 3 phr R233 + 3 phr HVA-2; (7) 8 phr NA-22; and (8) 8 phr NA-22 + 2 phr ZnO. 2


130

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MACROMOLECULAR

MATERIALS

f o r by the l o s s of HC1. A d d i t i o n o f Dicup peroxide o r R233 peroxide with or without coagents TMPT and HVA-2 r e s u l t e d o n l y i n minor m o d i f i c a t i o n s of the r a t e of d e h y d r o c h l o r i n a t i o n o f the CPE, thus y i e l d i n g r a t e s t h a t v a r i e d between 0.108 and 0.182 mg. eq. HCl/g. polymer-hour. A d d i t i o n o f ZnO to a CPE compound c o n t a i n i n g Dicup r e s u l t e d i n a very high r a t e o f dehydrochlo r i n a t i o n , 6.00 mg. eq. HCl/g. polymer-hour. Using NA-22 as a c r o s s l i n k i n g agent, the r a t e o f dehydro c h l o r i n a t i o n during c r o s s l i n k i n g was higher, 0.817 mg. eq. HCl/g. polymer-hour, than when peroxides were the c r o s s l i n k i n g agents. A d d i t i o n o f ZnO t o CPE c o n t a i n i n g NA-22 r e s u l t e d i n t h i s case i n a lower r a t e o f d e h y d r o c h l o r i n a t i o n , than when NA-22 alone was present. Dehydrochlorination o f Peroxide C r o s s l i n k e d CPE at 180°C i n Oxygen. The e f f e c t s of peroxide c r o s s l i n k i n g on the r a t e s o f d e h y d r o c h l o r i n a t i o n of CPE are shown i n Table I . The c r o s s l i n k i n g coagents trimethylolpropane t r i m e t h a c r y l a t e (TMPT) and Ν,Ν'-m-phenylenedimaleimide (HVA-2) are used f o r c u r i n g CPE and l e a d t o a higher c r o s s l i n k d e n s i t y o f the polymer when used i n peroxide c u r i n g systems. As seen from Table I c r o s s l i n k i n g o f the CPE u s i n g Dicup alone or Dicup, Vulcup, or R233 with coagents i n v a r i a b l y leads t o decreased maximum r a t e s o f d e h y d r o c h l o r i n a t i o n . However, the o v e r a l l r a t e of d e h y d r o c h l o r i n a t i o n as can be c a l c u l a t e d from the t o t a l HC1 evolved d i v i d e d by the t o t a l time o f degradation i s comparable f o r the u n c r o s s l i n k e d polymer (0.07 mg. eq. HCl/g. polymer-hour) and the c r o s s l i n k e d polymers (0.06 - 0.12 mg. eq. HCl/g. polymer-hour). E f f e c t s o f A n t i o x i d a n t s and S t a b i l i z e r s on Dehydrochlo r i n a t i o n o f Chemically C r o s s l i n k e d CPE a t 150°C i n Nitrogen. The a n t i o x i d a n t system i n v e s t i g a t e d i s a s y n e r g i s t i c system composed o f a phenol, namely, tetrakis[methylene 3-(3*,5'-di-tbutyl-4 -hydroxyphenyl)propionate]methane (Irganox 1010) and a s u l f u r compound, namely, d i s t e a r y l t h i o d i p r o p i o n a t e (DSTDP), both added a t 0.5 phr t o the CPE. The d e h y d r o c h l o r i n a t i o n s t a b i l i z e r s c o n s i s t e d of a bisphenol A epoxy r e s i n (DER331) added at 4 phr c o n c e n t r a t i o n and PbO added a t 5 phr c o n c e n t r a t i o n . The e f f e c t s o f these systems on the d e h y d r o c h l o r i n a t i o n r a t e s of peroxide c r o s s l i n k e d CPE and 2-mercaptoimidazoline c r o s s l i n k e d CPE are shown i n F i g u r e 2. Since the d e h y d r o c h l o r i n a t i o n was conducted i n n i t r o g e n , the a n t i o x i d a n t system alone had no e f f e c t on the d e h y d r o c h l o r i n a t i o n r a t e . However, the combined a n t i o x i d a n t and s t a b i l i z e r system had an a p p r e c i a b l e e f f e c t on peroxide c r o s s l i n k e d CPE, g i v i n g r i s e t o an i n d u c t i o n p e r i o d o f 105 hours when Dicup was used f o r c r o s s l i n k i n g and 90 hours when Dicup and TMPT were combined t o c r o s s l i n k the polymer. The maximum r a t e ^ o f d e h y d r o c h l o r i n a t i o n was a l s o a p p r e c i a b l y reduced from 55x10 t o 3.1x10 mg. eq. HCl/g. polymer-hour due to the i n c o r p o r a t i o n o f the s t a b i l i z e r f


ABU-ISA

Degradation

of Chlorinated

Polyethylene

Table I Dehydrochlorination o f CPE C r o s s l i n k e d with Peroxides and 2-Mercaptoimidazoline, Measured a t 180°C i n Oxygen

Crosslinking System

Rates o f Dehydrochlorination mg. eq. HCl/g Polymer-Hour Maximum Overall

None

0.27

0.070

6 phr Dicup

0.16

0.065

6 phr Dicup + 5 phr TMPT

0.084

0.059

6 phr Dicup + 3 phr HVA-2

0.12

0.11

6 phr Vulcup + 3 phr HVA-2

0.10

0.075

3 phr R233 + 3 phr HVA-2

0.18

0.12


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0

MATERIALS

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 Time in Hours

Figure 2. Effects of antioxidants and stabilizers on dehydrochlorination (150°C, N ) of chemically cross-linked CPE containing; (·), uncross-linked control; (O), uncross-linked control + 0.5 phr DSTDP + 0.5 phr Irganox 1010; (0), 6 phr Dicup; (A)>6 phr Dicup + 0.5 phr DSTDP + 0.5 phr Irganox 1010 + 4 phr DER + 5 phr PbO; ( V ) , same as A + TMPT; (-*-), 8 phr NA-22; ( • ), 8 phr NA-22 + 0.5 phr DSTDP + 0.5 phr Irganox 1010 + 4 phr DER + 5 phr PbO. 2

9.

ABU-ISA

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of Chlorinated

Polyethylene

133


and a n t i o x i d a n t systems. The b e n e f i c i a l e f f e c t s of these systems were not observed f o r the NA-22 c r o s s l i n k e d CPE. Without the s t a b i l i z e r s and a n t i o x i d a n t s a h i g h maximum r a t e of d e h y d r o c h l o r i n a t i o n o f 140x10 mg. eq. HCl/g. polymer-hour was measured and with these s t a b i l i z i n g a d d i t i v e s the maximum r a t | o f d e h y d r o c h l o r i n a t i o n rose to a higher value namely 150x10 . I t i s apparent t h a t t h i s mixed system i s i n e f f e c t i v e i n s t a b i l i z i n g NA-22 c r o s s l i n k e d CPE. E f f e c t s of A n t i o x i d a n t s and S t a b i l i z e r s on Dehydrochlor i n a t i o n o f Chemically C r o s s l i n k e d CPE at 180°C i n Oxygen. The e f f e c t i v e n e s s of the combined a n t i o x i d a n t (Irganox + DSTDP) and d e h y d r o c h l o r i n a t i o n s t a b i l i z e r s (DER + PbO) i s dramatic i n reducing the r a t e of d e h y d r o c h l o r i n a t i o n and g i v i n g r i s e t o a long i n d u c t i o n p e r i o d i n uncured CPE as seen i n F i g u r e 3. The maximum r a t e o f d e h y d r o c h l o r i n a t i o n i s reduced from 0.27 t o 0.031 mg. eq. HCl/g. polymer-hour and an i n d u c t i o n p e r i o d o f 22 hours i s observed due to the a d d i t i o n of the combined a n t i o x i d a n t s t a b i l i z e r system. The system i s l e s s e f f e c t i v e i n s t a b i l i z i n g the peroxide c r o s s l i n k e d polymer. Thus o n l y a marginal r e d u c t i o n from 0.084 t o 0.071 i n the maximum r a t e o f d e h y d r o c h l o r i n a t i o n and an i n d u c t i o n p e r i o d of 6 hours are observed when the s t a b i l i z e r systems are incorporated i n t o the polymer c r o s s l i n k e d by Dicup and TMPT. The maximum r a t e o f d e h y d r o c h l o r i n a t i o n o f NA-22 c r o s s l i n k e d CPE c o n t a i n i n g the s t a b i l i z e r s continues t o be very high (0.60 mg. eq. HCl/g. polymer-hour) under the above degradation conditions. E f f e c t s of R a d i a t i o n C r o s s l i n k i n g on Dehydrochlorination of CPE a t 180°C i n Oxygen. Four CPE compounds were chosen f o r r a d i a t i o n c u r i n g and subsequent d e h y d r o c h l o r i n a t i o n experiments. The f i r s t compound (Rad 1) was pure CPE, the second (Rad 2) contained 8 phr TMPT, the t h i r d (Rad 3) contained 8 phr TMPT and 0.5 phr o f each of the a n t i o x i d a n t s , Irganox 1010 and DSTDP, whereas the f o u r t h (Rad 4) contained the d e h y d r o c h l o r i n a t i o n s t a b i l i z e r s DER 331 (4 phr) and PbO (5 p h r ) i n a d d i t i o n t o TMPT, Irganox 1010 and DSTDP. Radiation c u r i n g of these compounds was conducted at two dose l e v e l s , namely, 10 Mrad and 20 Mrad. I r r a d i a t i o n a t each dose l e v e l was a l s o c a r r i e d out i n an a i r and i n a n i t r o g e n atmosphere. In order t o estimate the l e v e l o f c r o s s l i n k i n g a f t e r i r r a d i a t i o n , the compounds were immersed f o r one week i n toluene and the percent s w e l l and s o l u b l e f r a c t i o n s were measured and compared to chemically cured compounds o f CPE (Table I I ) . Except f o r pure CPE the same l e v e l o f c r o s s l i n k i n g i s observed i n n i t r o g e n and i n a i r i f samples are exposed t o the same dose. A d d i t i o n of TMPT as expected enhances the degree o f c r o s s l i n k i n g . A d d i t i o n of the a n t i o x i d a n t system or the dehydroc h l o r i n a t i o n s t a b i l i z e r system does not hinder c r o s s l i n k i n g by r a d i a t i o n . By comparing with chemically c r o s s l i n k e d systems i t can be deduced t h a t CPE i n the presence of TMPT r e q u i r e s l e s s


134

DURABILITY O F M A C R O M O L E C U L A R M A T E R I A L S

Time in Hours

Figure 3. Effects of antioxidants and stabilizers on dehydrochlorination (180°C, Og) of chemically cross-linked CPE containing: (O), uncross-linked control; (Φ), uncross-linked control + 0.5 phr DSTDP + 0.5 phr Irganox 1010 + 4 phr DER + 5 phr PbO; 5 phr TMPT + 6 phr Dicup; (0),5 phr TMPT + 6 phr Dicup + 0.5 phr DSTDP + 0.5 phr Irganox 1010 + 5 phr PbO + 4 phr DER; (0),8 phr NA-22 + 0.5 phr DSTDP + 0.5 phr Irganox 1010 + 5 phr PbO + 4 phr DER.

7.7 10.7

7.5 10.5

11.1 14.6

13·7 14.0

168 179

173 179

193 207

216 199

Rad 3 (CPE + TMPT + Irganox + DSTDP)

Rad 4 (CPE + TMPT + Irganox + DSTDP + DER + PbO)

316 466 352 304 358 341

CPE + NA-22 + Irganox + DSTDP + DER + PbO

CPE + Dicup + Irganox + DSTDP + DER + PbO

CPE + Dicup + TMPT + Irganox + DSTDP + DER + PbO

CPE + Dicup + HVA-2

CPE + Vulcup + HVA-2

CPE + R233 + HVA-2

16„2

16.3

14.2

18.6

18.2

8.8

% Soluble F r a c t i o n

7.7 9.3

16.8

15.8

201

205

270

273

Rad 2 (CPE + TMPT)

% Volume Swell

12.9 20.1

28.0

27.6

358

478

613

615

Rad 1 (CPE)

Β - Chemically Crosslinked

20/Air

2O/N9

10/Air

10/N?

20/Air

20/N?

% Soluble F r a c t i o n a f t e r I r r a d i a t i o n a t (Dose Mrad/Atmos.)

10/Air

% Volume Swell a f t e r I r r a d i a t i o n at (Dose Mrad/Atmosphere) 10/N2

Polymer

Radiation Crosslinked

Toluene Swell C h a r a c t e r i s t i c s o f Radiation and Chemically Crosslinked CPE

Table I I



136


MATERIALS

than 10 Mrad o f r a d i a t i o n f o r proper cure. This i s f u r t h e r v e r i f i e d by t e n s i l e property measurements shown i n Table I I I . Dehydrochlorination measurements o f the r a d i a t i o n cured compounds were conducted a t 180°C i n oxygen (Table I V ) . Radi a t i o n c r o s s l i n k i n g o f pure CPE reduces the maximum r a t e o f d e h y d r o c h l o r i n a t i o n from 0.27 f o r the u n c r o s s l i n k e d polymer t o 0.17 - 0.20 mg. eq. HCl/g. polymer-hour. The o v e r a l l r a t e o f d e h y d r o c h l o r i n a t i o n i s s i m i l a r f o r the uncured and r a d i a t i o n cured CPE. A d d i t i o n o f TMPT t o the polymer enhances the o v e r a l l r a t e o f d e h y d r o c h l o r i n a t i o n from 0.070 t o 0.14 - 0.16 mg. eq. HCl/g. polymer-hour. A d d i t i o n o f the a n t i o x i d a n t system reduced the o v e r a l l r a t e back t o 0.069 - 0.079. When t h e dehydrochlo r i n a t i o n s t a b i l i z e r s a r e added along with the a n t i o x i d a n t s an i n d u c t i o n p e r i o d i s produced but t h e r a t e o f d e h y d r o c h l o r i n a t i o n remains s i m i l a r t o t h a t observed i n the case o f a n t i o x i d a n t s alone. A t 10 Mrad dose the i n d u c t i o n p e r i o d l a s t s f o r 10 hours, whereas a t 20 Mrad dose i t i s reduced t o 5 hours. The dose l e v e l and the i r r a d i a t i o n atmosphere do not have a marked i n f l u e n c e on the r a t e o f d e h y d r o c h l o r i n a t i o n as seen i n Table IV. Discussion Of about twenty d i f f e r e n t c r o s s l i n k i n g systems t r i e d i n CPE only three were considered f o r t h e d e h y d r o c h l o r i n a t i o n s t u d i e s . These a r e the r a d i a t i o n , the peroxide and t h e 2-mercaptoimi d a z o l i n e systems. The others were e l i m i n a t e d from f u r t h e r c o n s i d e r a t i o n because they e i t h e r s e v e r e l y degraded t h e polymer o r d i d not induce s u f f i c i e n t c r o s s l i n k i n g . The suggested mechanisms o f c r o s s l i n k i n g o f t h e three systems s t u d i e d w i l l now be d i s c u s s e d . Two mechanisms a r e suggested i n the l i t e r a t u r e f o r t h e c r o s s l i n k i n g o f c h l o r i n a t e d polymers by 2-mercaptoimidazoline : when the compound i s used alone, and when ZnO i s used with i t . Csaszar and G a l i n s k y [4] proposed t h e f o l l o w i n g mechanism o f c r o s s l i n k i n g CPE by NA-22: -CH -CH -CHC1-CH -CH - + C H — C H 2

2

2

2

2

HN,

2

Ν SH

CH —CH I 2 2 HN 0

0

-HC1

HN^^N

S -CH -CH -CH-CH -CH 2

2

2

S

2

- C H

2

- C H

2

- C H - C H

2

- C H

2

-


9.

A B U - i S A

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of Chlorinated

Polyethylene

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Table I I I Mechanical P r o p e r t i e s o f Radiation C r o s s l i n k e d CPE

Polymer

Dose Mrad Atmosphere

Tensile Strength MP a

100% Modulus MPa

Elongation %

Tear N/M

Hardness, Durometer Points

Rad Rad Rad Rad Rad

1 1 1 1 1

0 10/Air 10/N 20/Air 20/N

10.27 13.51 15.44 16.82 12.20

2.48 2.21 2.41 2.41 2.34

505 470 470 415 425

25.0 22.2 23.1 23.6 22.6

77 72 73 70 72

Rad Rad Rad Rad Rad

2 2 2 2 2

0 10/Air 10/N 20/Air 20/N

12.13 17.10 16.82 18.96 19.17

7.58 9.93 9.17 10.20 9.65

405 300 312 230 230

40.4 30.2 29.4 25.9 28.7

75 65 73 72 76

Rad Rad Rad Rad Rad

3 3 3 3 3

0 10/Air 10/N 20/Air 20/N

9.79 17.51 17.17 17.10 18.41

1.24 8.41 8.41 10.27 10.43

600 377 315 200 210

16.6 42.7 41.7 30.8 35.2

62 90 91 75 91

Rad Rad Rad Rad Rad

4 4 4 4 4

0 10/Air 10/N 20/Air 20/N

5.24 12.48 12.96 11.72 15.38

0.90 7.79 7.72 8.96 9.45

560 270 260 190 230

14.4 39.9 40.4 37.5 39.0

52 88 88 90 88

2

2

2

2

2

2

2

DURABILITY OF MACROMOLECULAR MATERIALS


138

Table IV Dehydrochlorination o f R a d i a t i o n C r o s s l i n k e d CPE a t 180°C i n Oxygen

Polymer

Dose, Mrad/ Atmosphere

Rad

1

Rad

1

10/N

Rad

2

Rad

0

Rates o f Dehydrochlorination mg.eq. HCl/g polymer-hour Maximum Overall

Induction Period Hours

0.27

0.070

0

2

0.17

0.092

0

10/N

2

0.27

0.14

0

3

10/N

2

0.18

0.079

0

Rad 4

10/N

2

0.12

0.060

10.5

Rad

1

10/Air

0.20

0.089

0

Rad

2

10/Air

0.22

0.14

0

Rad

3

10/Air

0.086

0.069

0

Rad

4

10/Air

0.12

0.076

10.5

Rad

2

20/N

2

0.24

0.16

0

Rad 4

20/N

2

0.15

0.097

5.0

Rad

1

20/Air

0.18

0.11

0

Rad 4

20/Air

0.15

0.10

5.0

9.

Degradation

ABU-iSA

CH —CH 0

I

2

of Chlorinated

139

Polyethylene SH

0

I

-CH -CH -CH-CH -CH "

2

2

2

2

2

C

-CH -CH -CH-SH 2

CH Durability of Macromolecular Materials Downloaded from pubs.acs.org by UNIV OF ARIZONA on 10/24/15. For personal use only.

+

2

C1-CH-CH -CH 2

CH

2

—

2

-CH -CH -CH-CH -CH 2

2

2

2

-CH -CH -CH-CH -CH -

2

2

2

2

+HC1 When NA-22 i s used i n c h l o r i n a t e d elastomer with ZnO the f o l l o w i n g c r o s s l i n k i n g mechanism i s suggested by P a r i s e r [5]:

-CH -CH -CHC1-CH -CH 2

2

2

2

HN

NH

-CH -CH -C-CH -CH 2

2

2

2

HN^l'^NH

CI

I

ι

ZnO

-CH -CH -C-CH -CH 2

2

2

2

S

t

HN^^NH +

IZnCl I

-CH -CH -C-CH -CH 20

0 2

,

ZnCl II

20

2

+

0

+

HIT ι

NH ι

J

-CH -CH -C-CH -CH 9

II + -CH -CH -CHC1-CH -CH 2

2

2

2

2

2

+

m»

S

K3i -CH

Durability of Macromolecular Materials - American Chemical Society

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