Different mechanisms for the protection of polymers against photodegradation are discussed. (1) The u.v.-absorbers of the 2-(2-hydroxyphenyl)-benzotriazolc and the o-hydroxybcnzophenone type havc rates of internal conversion much higher than the rate of intersystem crossing and of fluorescence dccay. Evidence is presented that this rapid non-radiativc deactivation cannot be explaincd very satisfactorily by a simple 'cnol-keto'-cquilibrium in the first excited singlct state only.(2) At the concentrations used in practice the quenching rate oflight stabilizers is so low that qucnching cannot compete successfully with other deactivation processes of triplet states, while excited singlet states of primary scnsitizers can be quenched efficicntly only by additives with extinction coefficients ofmore than 5 000 to 10000.(3) The derivatives of 2,2,6,6-tetramethyl-pipcridines of the structurcs I to IV cannot quench excited singlet states in the apolar solvent heptane. The corresponding N-oxyls inhibit the Norrish reaction of aralkylkctones. Spccific N-oxyl-and N-methyl-2,2,6,6-tetramethyl-piperidines as weil as certain nicket chelates decelerate the singlet oxygen induced photo-oxygenation of rubrene and 9,1 0-dimethoxy anthracene.

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Naval O r d n a n c e Laboratory(U-) HNS/Teflon ( 9 0 / 1 0 ) i s a new p r e s s e d e x p l o s i v e developed f o r use i n t h e APOLLO program. The major a d v a n t a g e s of HlS/Teflon a r e i t s , (1) e x c e l l e n t t h e r m a l s t a b i l i t y a t e l e v a t e d t e m p e r a t u r e s (2) s u p e r i o r r e s i s t a n c e t o s u b l i m a t i o n at h i g h t e m p e r a t u r e s and low p r e s s u r e s and ( 3 ) ease of molding powder p r e p a r a t i o n , p r e s s i n g and machining.T h e impact s e n s i t i v i t y o f HIS/Teflon i s between t h a t of Comp B and Comp A-3 w h i l e i t s e x p l o s i v e performance is a b o u t t h e same as TBT. Under t h e severe e n v i r o n m e n t a l c o n d i t i o n s of t h e moon's s u r f a c e , t h i s e x p l o s i v e s u c c e s s f u l l y performed i t s i n t e n d e d f u n c t i o nof g e n e r a t i n g s e i s m i c waves i n t h e APOLLO ALSEP and LSPE e x p e r i m e n t s . e i n t h e a c t i v e s e i s m i c e x p e r i m e n t s in b o t h t h e APOLLO A c t i v e Lunar S e i s m i c Experiments Peckege (ALSEP) and t h e Lunar S e i s m i c P r o f i l i n g Experiments (LSPE). T h i s r e p o r t d e s c r i b e s t h e dzvelopment, t e s t i n g , p r o p e r t i e s and performance of HNS/Teflon c h a r g e s and s h o u l d be of i n t e r e s t t c i e n g i n e e r s and s c i e n t i s t s who r e q u i r e e x p l o s i v e s t h a t most w i t h s t a n d h o s t i l e envircnmeqts.(U) HIS i s one o f a s e r i e s o f h e a t -r e s i s t a n t e x p l o s i v e s s y n t h e s i z e d a t t h e Neval Ordnance L a b o r a t o r y , as p a r t of a n a c t i v e and c o n t i n u i n g program w i t h t h e o b j e c t i v e o f . s t u d y i n g t h e c h e m i s t r y of n i t r o com-

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