Polymer decomposition initiated by high energy radiatio

Wall, L. A.

English

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3 1102 - 11 -3 110540 
POLYMER DECOMPOSITION INITIATED BY HIGH ENERGY RADIATION 
NASA Contract R-56 
by T e n  A .  Wall 
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Covering Three Quar t e r ly  Per iods 
November 1965 t o  May 1966 
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National  Aeronautics and Space Administration 
Washington, D.C. 
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April 1966 
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POLYMER DECOMPOSITION INITIATED BY 
HIGH ENERGY RADIATION 
P a r t i c i p a t i n g  I n v e s t i g a t o r s :  
Leo A .  Wall 
Roland E. F l o r i n  
Sidney S t r a u s  
The sub jec t  mat te r  o f  t h i s  p r o j e c t  i s  the k i n e t i c s  and 
mechanisms o f  t h e  chemical and phys ica l  changes occurr ing  
i n  polymers exposed t o  vacuum u l t r a v i o l e t  and gamma r a d i a t i o n  
a t  temperatures i n  the  range from ambient ( 2 5 O C )  upward t o  
500°C. I n  a d d i t i o n  t o  temperature and Padia t ion ,  t h e  condi t ions  
of exposure involve both vacuum and t h e  presence o f  r e a c t i v e  
gaseous atmospheres. I n t e r p r e t a t i o n  o f  r e s u l t s  obtained 
wi th  vacuum u l t r a v i o l e t  r a d i a t i o n  i s  a r a t h e r  formidable 
problem because of t he  la rge  absorpt ion c o e f f i c i e n t s  and 
consequent inhomogeneous exposure wi th in  samples .  
STATUS OF PRESENT RESEARCH 
Progress  i n  t h e  p a s t  qua r t e r ly  per iods  w a s  a long t h e  
fol lowing l i n e s :  
A.  The a r t i c l e  on the  gamma ray  i n i t i a t e d  thermal 
depolymerization o f  po ly te t ra f luoroe thylene  w i l l  s h o r t l y  
appear  i n  t h e  Jou rna l  of Research National Bureau of  Standards.  
The mechanism i s  shown t o  cons is t  o f  random i n i t i a t i o n ,  
t e rmina t ion  by combination, a t  least  99.4$, and t h e  k i n e t i c  
chain lengths  a r e  shor t ,  5 t o  100 depending on tenpera ture .  
. 
- .  
. 
-2- 
I n  o rde r  t o  improve our measurements f o r  these  gamma 
ray  i n i t i a t e d  s tud ie s ,  a new apparatus  i s  being cons t ruc ted  
and t e s t e d .  It i s  a n t i c i p a t e d  t h a t  s t u d i e s  on o t h e r  fluorocarbon 
polymers w i l l  be i n i t i a t e d  sho r t ly .  
B. Severa l  vacuum u l t r a v i o l e t  lamps, i . e . ,  xenon resonance 
lamps, which previously f a i l ed  by developing l eaks  a t  t h e  
complicated s e a l  holding the  l i th ium f luo r ide ,  now appear  to 
be vacuum t i g h t .  After  s eve ra l  t r ia l s ,  a lamp has been 
constructed which has held a t  2 5 O C  and s e v e r a l  polymers have 
been exposed to t h i s  lamp. A t  p resent  we a r e  t e s t i n g  t h e  
exposed polymers by s o l u b i l i t y  and swel l ing techniques,  s i n c e  
i t  i s  a n t i c i p a t e d  t h a t  c ross l ink ing  should occur i n  the out -  
sk in .  However, s i n c e  a l l  e f f e c t s  a r e  expected t o  occur  i n  
t h e  f i r s t  1000 l aye r  o f  the  sample, i t  i s  not  s u r p r i s i n g  
t h a t  s o  f a r  a l l  t h e  samples appear to d i s so lve  a s  r e a d i l y  as 
t h e  unexposed samples. 
C .  A thermal decomposition study of a n i o n i c a l l y  
prepared polymers of 1,2-dihydronaphthalene was c a r r i e d  out .  
The polymer was inves t iga t ed  because re ferences  i n  t h e  
l i t e r a t u r e  suggested t h a t  i t  had outs tandingly  thermal and 
r a d i o l y t i c  s t a b i l i t y .  It  was found that t h e  polymer was 
only s l i g h t l y  b e t t e r  than polystyrene,  and un l ike  polystyrene 
appears  t o  decompose exothermically. This exothermic process  
depends a t  l e a s t  t o  some extent  on the aggregat ion of t h e  
. 
? 
-3 - 
- polymer ma te r i a l .  This  work has been completed, w r i t t e n  up 
and i s  now i n  e d i t o r i a l  review. 
D. During t h e  p a s t  q u a r t e r l y  per iods,  an improved 
appara tus  f o r  isothermal  and non-isothermal r a t e s  o f  
v o l a t i l i z a t i o n  measurements was cons t ruc ted  f o r  use wi th  
both t h e  vacuum u l t r a v i o l e t  and pu re ly  thermal s tud ie s .  
Attached i s  a desc r ip t ion  of the instrument .  
STATUS OF PUBLICATIONS FROM THE PROJECT 
1. "Pyrolys is  o f  New Fluoropolymers", by S. S t r aus  and 
L.A. Wall, SPE Trans. - 4, [l], 56 ( Jan .  1964). 
2. "Pyrolys is  o f  Poly t r i f luoroe thylene .  In f luence  o f  Gamma 
Radiat ion and Alka l i  Treatment", S. St raus  and L.A. Wall, 
SPE Trans. - 4, [l], 61 ( Jan .  1964). 
"Pyro lys is  of Vinyl and Vinylidene F luor ide  Polymers-- 
Inf luence  of P r i o r  Gamma I r r a d i a t i o n " ,  L.A. Wall, 
S. S t r aus ,  and R.E. F lor in ,  manuscript accepted by 
J. Polymer Sci. 
" S t r e s s  Relaxat ion o f  y - I r r ad ia t ed  Fluorocarbon Elastomers", 
by T. Yoshida, R.E. F lor in ,  and L.A. Wall, J .  Polymer 
S c i .  -J 3 A  151 1685 (May 1965). 
3 .  
4. 
11 5. On t h e  Measurement of Random Chain Sc i s s ion  by S t r e s s  
Relaxation",  by Hyuk Yu, Polymer L e t t e r s  - 2, [4], 631 (1964). 
" E f f e c t s  o f  Composition and I r r a d i a t i o n  on t h e  Glass 
T r a n s i t i o n  Temperature of Methyl Methacrylate S tyrene  
Copolymers", by MIS. Parker, V.J .  Krasnansky and B.G. 
Achhammer, J. Appl. Polymer S c i .  - 8, [ 4 ] ,  1825 ( J u l y  1964). 
6. 
. 
' V  
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I .  
8. 
9. 
10. 
11. 
12. 
13 
"The Mechanism o f  the  Radio ly t ic  and Pyro ly t i c  I n i t i a t e d  
Depolymerization o f  Po l y t  e t r a  f luoro ethylene",  
R.E. F lo r in ,  M.S. Parker, D.W. Brown, and L.A. Wall, 
J.  Research NBS, April-May 1966. 
"Radiolyt ic  S t r e s s  Relaxation of- a n  Ethylene-Propylene 
Copolymer", by H. Yu and L.A. Wall, J .  Phys. Chem. 69, 
[ 6 ] ,  2072 (June 1965). 
11 The Thermal Degradation Mechanism o f  Polystyrene",  by 
L.A. Wall, 5 .  Straus,  J . H .  Flynn, D. McIntyre, and 
R. Simha, J .  Phys. Chem. 70, [l], 53 (Jan.  1966). 
11 The E f f e c t  o f  Gamma I r r a d i a t i o n  on a Polyamide", by 
V.J.  Krasnansky, M.S. Parker, and R.E. F lo r in ,  J .  Phys. 
Chem. - 70, [l], 40 (Jan.  1966). 
11 Kinet ics  of  the  Hydroxyl Radical  i n  Aqueous Solut ion",  
by F. S i c i l i o ,  R.E. F lor in ,  and L.A. Wall, J .  Phys. 
Chem. - 70, [l], 47 (Jan.  1966). 
"Polymerization and Pyro lys is  of  Poly-1, 2-dihydronaphthaleneV1, 
L.A. Wall, L.J. F e t t e r s ,  and 5 .  Straus ,  p resented  a t  t h e  
150th Am. Chem. SOC. Meeting, September 1965, A t l a n t i c  City,  
manuscript i n  e d i t o r i a l  review. 
by 
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Thermogravimetric Instrument, by 5 .  St raus  and L.A. Wall, 
copies  a t tached .  
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FUTURE PLANS 
I n v e s t i g a t e  : 
1. Kinet ics  and mechanism o f  polymer, p o l y t e t r a f l u o r o -  
e thylene,  polyethylene and other, decompositions i n i t i a t e d  
by xenon resonance r a d i a t i o n  (1475 E ) ,  . 
2. a t  25OC and 
3 .  upward to 500°C. 
4. Explore t h e  e f f e c t s  of s h o r t e r  wave length  r a d i a t i o n  
by g o i n t  to krypton, argon o r  another  r a r e  gas  resonance 
lamp. 


Polymer decomposition initiated by high energy radiation Progress report, Nov. 1965 - May 1966

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