Lap shear specimens were f a b r i c a t e d u s i n g adhesive t a p e prepared f r o m each o f t h e t h r e e polymers. Lap shear t e s t s were performed a t room temperature, 177OC, and 2n4"C b e f o r e and a f t e r exposure t o w a t e r -h o i l and t o thermal a g i n g a t 204OC f o r tip t o In00 hours.
The t h r e e adhesive systems possess p x c p p t i o n a l l a p shear s t r e n g t h s a t room t e m p e r a t u r e and e l e v a t e d t e m p e r a t u r e s h o t h h e f o r e and a f t e r thermal exposure. LARC-STPI, hecaiisc! of i t s h i g h q l a s s t r a n s i t i o n t e m p e r a t u r e p r o v i d e d h i g h l a p shear s t r e n g t h s up t o 26nOC.A f t e r \:ater-hoil, LARC-TPT e x h i h i t s d t h e hiahast. l a p shear s t r s n a t h s a t rnoq
St. C l a i r . Also prepared and evaluated was an endcapped version o f PIS02. These two polymers were compared with LARC-TPI and LARC-STPI, polyimides researched i n our l a b o r a t o r y and r e p o r t e d i n t h e 1 i t e r a t u r e . ' . The adhesive evaluation, p r i m a r i l y based on l a p shear s t r e n g t h (LSS) t e s t s , i n v o l v e d preparing adhesive tapes, conducting bonding s t u d i e s and exposing l a p shear specimens t o 204°C a i r f o r up t o 1000 h r s and t o a 72-hour water b o i l . LSS t e s t s a t RT, 177°C and 204°C were performed before ( c o n t r o l s ) and a f t e r these exposures. The type o f adhesive f a i l u r e as w e l l as the Tg was determined f o r t h e f r a c t u r e d specimens.
The r e s u l t s i n d i c a t e t h a t LARC-TPI provides the h i g h e s t LSSs, 33 MPa a t RT, 30 MPa a t 177"C, and 26 MPa a t 204°C. LARC-F-SO2, LARC-TPI andLARC-STPI a l l r e t a i n t h e i r strengths a f t e r thermal exposure f o r 1000 h r s and PIS02 r e t a i n s g r e a t e r than 80% o f i t s c o n t r o l strengths.Most o f t h e f o u r adhesive systems showed reduced s t r e n g t h s f o r a l l t e s t temperatures a1 though s t i 11 r e t a i n i n g a high percentage o f t h e i r o r i g i n a l s t r e n g t h ( > 60%) except f o r one case.
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