R A D I A T I O N S T A B I L I T Y O F P A C K I N G M A T E R I A L S *

B . Z h u k o v

R a d i o s t e r i l i z a t i o n of m e d i c i n a l , p h a r m a c e u t i c a l , and food p r o d u c t s h a s now b e c o m e an e s t a b l i s h e d

b r a n c h of i n d u s t r y in m a n y c o u n t r i e s . T h e b a c t e r i c i d a l a c t i o n of i o n i z i n g r a d i a t i o n s , t h e i r g r e a t p e n e t r a t i n g

p o w e r , t he i n s i g n i f i c a n t r i s e in t e m p e r a t u r e o f the i r r a d i a t e d p r o d u c t s , c o m b i n e to m a k e r a d i o s t e r i l i z a t i o n

the s o l e p o s s i b l e m e t h o d of s t e r i l i z a t i o n of n e w m a t e r i a l s a n d p r e p a r a t i o n s w h i c h a r e no t c a p a b l e of w i t h -

s t a n d i n g t h e r m a l , c h e m i c a l , o r o t h e r s t e r i l i z a t i o n t r e a t m e n t .

T h e b a s i c p o s i t i v e f a c t o r c h a r a c t e r i z i n g t h i s s t e r i l i z a t i o n m e t h o d i s the p o s s i b i l i t y of s t e r i l i z i n g p r e p -

a r a t i o n s and m a t e r i a l s w h i c h a r e a d v e r s e l y a f f e c t e d by h e a t , p r o c e s s i n g o b j e c t s of d i f f e r e n t v o l u m e s p a c k -

a g e d in p a p e r , g l a s s , p l a s t i c s , and p l a c i n g the r a d i a t i o n s o u r c e s d i r e c t l y on the p r o d u c t i o n l i n e , p r e p a r i n g

* B a s e d on r e p o r t s to the I A E A s y m p o s i u m on r a d i o s t e r t l i z a t i o n of m e d i c i n a l p r o d u c t s ( B u d a p e s t , H u n g a r y , 1967).

T A B L E 1. E x p o s u r e D o s e s a t w h i c h P a c k i n g M a t e r i a l s L i s t e d S t i l l R e t a i n T h e i r P h y s i c o m e e h a n i c a l

P r o p e r t i e s

Materials Dose, R Remarks

Rubbers

Polycarbonyl N atur al gBR Butadienestyrene Nitrile

. Silicone

Neoprene Butylene

Thermostable plastics

Polystyrene Polyethylene (high-pressure and tow-pressure) Nylon 6 and nylon 6 : 6

Polyvinylchloride, PVC copolymeranes

Polycarbonates Cellulose ether acetates or nitrites Polypropylene P ol yme th ylm eth acr )11 ate PTFE "teilon" or "fakon"

Polyacetate-polyformaldehyde, or copolymers

Thermostable resins

Epoxy resins

Bakelite phenolformaldehyde UE thioformaldehyde resins Polyester resins, styrene-modified

Textiles

Terylene or Dacron polyester fibres Dicel or Tricel cellulose acetate Orlon, Actylene, Courtelte acrylic fibers Wool and silk Viscose Cotton

Satisfactory to 5.10 8 ,, ,, 10 8 ,, ,, 10 8 ,, ,, 10 s

,, ,, 107

,, ,, 10 7

Unsatisfactory to l0 s

Satisfactory to 5.10 s . . . . 108 ,, , , 10 8

. . . . i0 ~

,, ,, 107 ,, ,, 107

. . . . 2.8. 10 a

. . . . 2 . 5 . l o ~

Unsatisfactory even below 106 Same

Satisfactory to 5. I0 ~

. . . . 1 0 8

,, ,, 10 7

" " i 0 8

,, ,, l0 T

,, ,, 10 7

. . 10 7

,, ,, 10 7

,, ,, 10 7

. . . . 2.5.10 6

Most r adiation-stable Excellent stability S ame

i,

Polydimethylsiloxane more stable than methyl- phenylsilicone

Hydrochloric acid causes corrosion. Breaks down even at comparatively low doses

Most radiation-stable High radiation stability Same Acid-resistant, and more stable than polyvinyl-

chloride Tendency to brittleness at high doses Acetates less stable than nitrocellulose Becomes brittle Darkens, becomes brownish and brittle

Acid-soluble, more stable in absence of air

Becomes brittle

Very stable, especially when resin contains amines

High stability, discolors at same time Same Excellent stability.

Stable to irradiation Loss of strength Crosslinking observed at low doses Loss of strength, silk even less stable Much more stable than cotton 20 % loss of strength at dose of 106 R

Translated from Atomnaya ]~nergiya, Vol. 25, No. I, pp. 75-76, July, 1968.

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medica l a c c e s s o r i e s and p repa ra t ions under other than specia l antiseptic conditions which would r a i se the cos t of the products , t r ea tmen t of those products under o rd ina ry conditions with subsequent s te r i l i za t ion while packaged.

The r e su l t s of this p r o g r a m show that the method makes it poss ible to s te r i l i ze surg ica l suturing and bandaging m a t e r i a l s , equipment for the p repara t ion , s to rage , and t ransfus ion of blood, p las t ic syr inges and tubing with different pha rmaceu t i ca l p repa ra t ions on a throwaway bas i s , var ious surg ica l ins t ruments , syn- thetic p r o s t h e s i s for blood ve s s e l s , and cadave r t ransplan t m a t e r i a l s (vesse ls , bones for graf t ing appl ica- tions), var ious s y s t e m s fo r ar t i f ic ia l blood c i rcula t ion equipment and ar t i f ic ia l kidneys, pha rmaceu t i ca l s (antibiotics, polyvi tamin p repa ra t ions , hormones , many enzymes , anticoagulants , human blood p lasma , blood p repa ra t i ons and blood subst i tutes) .

The following r a d i a t i o n - p r o c e s s e d foodstuffs a re packagefl in f i lms: raw mea t semif in ished products including beef, pork, and rabbi t mea t , d r e s s e d and boned chicken, precooked mea t products (fried and roas ted mea t s , en t reco tes ) , plus bacon, fish, and sea food. Each commodi ty is packaged in air t ight f i lm and is then rad ia t ion- s t e r i l i zed . The choice of packaging m a t e r i a l s becomes a m a j o r p rob lem with this wide va r i e ty of types and shapes of products to be s te r i l ized . Most packaging m a t e r i a l s re ta in thei r phys icochem- ical p r o p e r t i e s intact at doses up to 2.5.106 R. But m a t e r i a l s such as polypropylene and packaging f i lm made of polypropylene become thin at a dosage of 5.106 R and can be used only with grea t ca re .

In the view of mos t spec ia l i s t s on the question, the vapor pe rmeab i l i ty of i r rad ia ted packaging m a t e - r i a l s undergoes ve ry litt le change. This change can be neglected, it s e ems , although some studies have in- dicated that breakdown of the m a t e r i a l se ts in at doses of 106 R in some po lymer s , and this might mean in- c r e a s e d vapor pe rmeab i l i ty .

Table 1 l i s t s some of the basic c h a r a c t e r i s t i c s of re levant packaging m a t e r i a l s .

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