Fiber Diffraction Methods - ACS Publications - American Chemical

17. Electron Diffraction and Dark Field on Ultrathin. Sections of Textile Fibers. R. HAGEGE ... 0,1 M solution of silver nitrate. Sorbed H2 S i s ... ...
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17 Electron Diffraction and Dark Field on Ultrathin Sections of Textile Fibers R. H A G E G E

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Institut Textile de France, 35 Rue des Abondances, 92100 Boulogne S/Seine, France

X-Ray d i f f r a c t i o n studies of t e x t i l e f i b e r s have led to the development of techniques to c a l c u l a t e or estimate the following f i b e r c h a r a c t e r i s t i c s : • percents crystallinity (% c r y s t a l l i n e fraction) • c r y s t a l l i n e perfection (as characterized by various indexes) • mean dimensions of c r y s t a l l i t e s • long-period as estimated by small angle X-Ray scattering, e t c . . . However, electron d i f f r a c t i o n , although frequently used for polymer single c r y s t a l s studies, has s e l dom been applied to t e x t i l e f i b e r s , and p a r t i c u l a r l y to u l t r a t h i n sections of those m a t e r i e l s . (1,2) the majority of published papers dealing with electron d i f f r a c t i o n of f i b e r s i s concerned with i s o l a t e d fibrils or fragments prepared by mechanical m i l l i n g . As far as we know, apart from a preliminary report about mercerization of cotton f i b e r s (3) and a recent paper about chemically etched PETP filaments (4), high modulus aramide fibers and carbon f i b e r s are p r a c t i c a l l y the only systems with d e t a i l e d (recently) published work on electron d i f f r a c t i o n and dark field of u l t r a - t h i n sections of t e x t i l e or p a r a t e x t i l e f i b e r s (5, 6, 7). Here we report s i m i l a r studies on 2GT polyester and 66 polyamide f i b e r s and define l o c a l order indexes.

0-8412-0589-2/80/47-141-279$05.75/0 © 1980 American Chemical Society French and Gardner; Fiber Diffraction Methods ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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methods

Various kinds of m u l t i f i l a m e n t coutinuous yarns o f 2GT p o l y e s t e r ( r e f e r r e d t o as PETP i n the p r e s e n t paper) were i n v e s t i g a t e d : . 1 FT t e x t u r e d c o n t i n u o u s y a r n (PETP^) . 1 m u l t i f i l a m e n t from a g e o t e x t i l e spun bond membrane made o f BIDIM ( R h o n e - P o u l e n c - T e x t i l e (RPT) - marque deposee) (PETP ) . 1 thermoset m u l t i f i l a m e n t f o r t i r e - c o r d a p p l i c a t i o n (PETP ) 2

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3

V a r i o u s 66 p o l y a m i d e c o n t i n u o u s y a r n s were a l s o examined ( r e f e r r e d t o as, "type 2", "type 4" and "type 5") : t h e s e are e x p e r i m e n t a l y a r n s p r e p a r e d i n d i f f e r e n t c o n d i t i o n s and s u p p l i e d by RPT. Only transverse s e c t i o n s ( i . e . s e c t i o n s c u t as p r e c i s e l y as p o s s i b l e , normal t o the f i b e r a x i s ) were examined. The p r o d u c t i o n o f e l e c t r o n m i c r o d i f f r a c t i o n p a t t e r n s and d a r k f i e l d m i c r o g r a p h s has t o be done on very t h i n s e c t i o n s ( i f p o s s i b l e s e c t i o n s thinner than those used f o r o r d i n a r y b r i g h t f i e l d work). T h i s i s v e r y d i f f i c u l t t o do w i t h t h i s k i n d o f m a t e r i a l . S t a i ning with A g f o l l o w i n g the u s u a l method i n our l a b o r a t o r y (8) o f t e n , i f n o t always, i s u s e f u l i n improv i n g the q u a l i t y o f the s e c t i o n s , w i t h o u t d i s t u r b i n g e i t h e r the p r o d u c t i o n o f a d i f f r a c t i o n p a t t e r n c h a r a c t e r i s t i c o f the polymer s p e c i e s , or the p h o t o g r a p h i n d a r k - f i e l d c o n d i t i o n s . Ag2S s t a i n i n g p r o c e d u r e : the f i b e r s are t r e a t e d under 15 Atm a t 2 0 ° C by gazeous H S. A f t e r m i l d r i n s i n g w i t h a l c o h o l or acetone, they are immersed f o r 16 h o u r s a t 2 0 ° C i n t o an aqueous 0,1 M s o l u t i o n o f s i l v e r n i t r a t e . Sorbed H S i s t h u s t r a n s f o r m e d i n t o A g S and " i n s i t u " p r e c i p i t a t e d i n t o the a c c e s s i b l e r e g i o n s . The f i b e r s are t h e n r i n s e d by water and d r i e d b e f o r e embedding and c u t t i n g . #

s

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E l e c t r o n D i f f r a c t i o n Micrographs P r o d u c t i o n o f the n e g a t i v e p r i n t s . In o r d e r t o a l l o w a q u a n t i t a t i v e t r e a t m e n t o f the m i c r o g r a p h s , the w i d t h o f the e l e c t r o n beam was c a r e f u l l y c o n t r o l l e d . The " i r r a d i a t e d a r e a " i s the a r e a o f the s e c t i o n i l l u m i n a t e d by the e l e c t r o n beam, whereas the

French and Gardner; Fiber Diffraction Methods ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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" s e l e c t e d a r e a " i s i s o l a t e d from t h e i r r a d i a t e d a r e a by means o f a s e l e c t i o n a p e r t u r e which has a diameter o f 0.5 o r 1 pm, i . e . , 1/10 t o 1/5 o f t h e l a t t e r . The s e c t i o n i s searched under v e r y m i l d c o n d i t i o n s o f i r r a d i a t i o n so t h a t t h e a r e a o f i n t e r e s t does n o t d e t e r i o r a t e , the filament being g e n e r a l l y undersaturated and a l l o t h e r s e t t i n g s t o t h e minimum. In the p r e s e n t work, we have t r i e d t o examine t h e v a l i d i t y o f t h e f o l l o w i n g method f o r q u a n t i t a t i v e p u r poses : f i r s t we p h o t o g r a p h t h e " i n t a c t " d i f f r a c t i o n p a t t e r n under d e f i n e d c o n d i t i o n s , then we photograph the amorphous p a t t e r n under -bhe same c o n d i t i o n s . The amorphous p a t t e r n i s o b t a i n e d b y i n c r e a s i n g t h e r a d i a t i o n rate u n t i l the c r y s t a l l i n e d i f f r a c t i o n d i s a p p e a r s . I n o r d e r t o r e c o r d t h e " c r y s t a l l i n e " and "amorphous" p a t t e r n s o f t h e same s e l e c t e d a r e a on t h e same photographic emulsion ( t o minimize the i n f l u e n c e o f photographic processing c o n d i t i o n s ) , the f o l l o w i n g p r o c e d u r e was adopted : a) v i s u a l l y i d e n t i f y t h e " c r y s t a l l i n e " p a t t e r n i n m i l d i r r a d i a t i o n c o n d i t i o n s (those c o n d i t i o n s a r e i n a dequate f o r t h e photography) b) i n t r o d u c e an o b j e c t i v e a p e r t u r e o f 75 ym: t h i s i s o f s u f f i c i e n t s i z e so n o t t o h i d e t h e main d i f f r a c t i o n a r c s . T h i s aperture prevents the i r r a d i a t i o n o f the p h o t o g r a p h i c e m u l s i o n f a r away from t h e c e n t e r o f t h e " i n t a c t " p a t t e r n , which a l l o w s f o r o t h e r p r i n t s t o be taken on t h e same p l a t e o r f i l m c) c e n t e r t h e " d i f f r a c t i o n spot" ( i . e . t h e impact o f the u n s c a t t e r e d beam) i n a c o n v e n i e n t p o s i t i o n ( e . g. near one c o r n e r o f t h e p h o t o g r a p h i c p l a t e ) and r e c o r d t h e d i f f r a c t i o n p a t t e r n w i t h c a r e f u l l y def i n e d c o n d i t i o n s o f i r r a d i a t i o n and exposure time d) " d e s t r o y " t h e c r y s t a l l i n e o r d e r o f t h e s e l e c t e d a r e a and i t s s u r r o u n d i n g s ( c o n t r o l l i n g i t v i s u a l l y ) b y a s t r o n g i n c r e a s e o f t h e r a d i a t i o n r a t e d u r i n g adequate time e) r e c o r d t h e " d e s t r o y e d " p a t t e r n i n t h e same c o n d i t i o n s as i n c) w i t h t h e c e n t e r o f t h e d i f f r a c t i o n spot i n a d i f f e r e n t p a r t o f t h e p h o t o g r a p h i c p l a t e

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r e p e a t d) a n d e) t o g e t a s e c o n d e x p o s u r e o f t h e " d e s t r o y e d " p a t t e r n . T h i s i s t o check the d i s a p p e a rance o f the c r y s t a l l i n i t y r e t u r n t o "image" c o n d i t i o n s and e x p o s e t h e irrad i a t e d z o n e a n d i t s s u r r o u n d i n g s ; t h e beam s h o u l d b e f o c u s e d ( l e s s t h a n i t was f o r t h e r e c o r d i n g o f d i f f r a c t i o n p a t t e r n ) and d e f l e c t e d and t h e p r e p a r a t i o n s h i f t e d so t h a t t h i s e x p o s u r e i s n o t s u p e r i m p o sed on the p r e c e e d i n g o n e s .

T h r e e d i f f r a c t i o n p a t t e r n s and one m i c r o g r a p h a r e t h u s r e c o r d e d o n t h e same p l a t e o r f i l m . I n some c a s e s , we t r i e d t o e v a l u a t e t h e d e g r a d a t i o n o f t h e c r y s t a l l i ne p a t t e r n s d u r i n g one e x p o s u r e ; t h i s i s a n a l o g o u s to an i d e a o f a p r e v i o u s w o r k o f Dobb (9) who h a s s t u d i e d the k i n e t i c s o f the disappearance o f the main i n t e r f e rences i n the e l e c t r o n d i f f r a c t i o n p a t t e r n of c e l l u l o se u n d e r c o n s t a n t i r r a d i a t i o n r a t e b y a m e t h o d o f " t i m e - l a p s e s e r i e s " . O u r a i m was t o t r y t o d e t e r m i n e a " t r u e " c r y s t a l l i n i t y b y an e x t r a p o l a t i o n t o z e r o d o s e . I n s u c h a mode, the " c r y s t a l l i n e " p a t t e r n o f t h e same s e l e c t e d a r e a i s r e c o r d e d t h r e e t i m e s ( o n t h e s a me e m u l s i o n ) t h e i r r a d i a t i o n r a t e c o r r e s p o n d i n g t o an exposure b e i n g set o n l y d u r i n g the exposure time. On t h e same p l a t e o r f i l m , 4 d i f f r a c t i o n p a t t e r n ( t h r e e "crystalline" patterns with a beginning of degradation and a n " a m o r p h o u s " o n e o b t a i n e d a s a l r e a d y e x p l a i n e d ) and o n e m o r p h o l o g i c a l v i e w a r e o b t a i n e d . F i g u r e 1 shows a n e x a m p l e o f a s l i d e w i t h 5 e x p o s u r e s o f a P A 66 f i l a m e n t (4 d i f f r a c t i o n p a t t e r n s a n d 1 m o r p h o l o g i c view) o b t a i n e d f r o m a p a r t i c u l a r zone o f the c r o s s - s e c t i o n o f an A g S - s t a i n e d f i b e r ; the 3 " c r y s t a l l i n e " p a t t e r n s show a n i n c r e a s i n g d e g r a d a t i o n ( i n t h e follow i n g way 1 , 2 , 3) a n d " A " i s t h e a m o r p h o u s p a t t e r n . 2

T h i s p r o c e s s ( u s i n g one o f t h e m o d e s p r e v i o u s l y d e s c r i b e d ) was a p p l i e d t o a s e t o f 3 t o 12 d i f f e r e n t s e l e c t e d a r e a s on t h e t r a n s v e r s e s e c t i o n o f one f i b e r . The p h o t o g r a p h i c s e r i e s i s a c o m p l e t e d r e c o r d o f t h e w h o l e f i b e r c r o s s - s e c t i o n a t an a d e q u a t e m a g n i f i c a t i o n . On t h e l a t t e r m i c r o g r a p h t h e i r r a d i a t e d a r e a s c a n b e seen because o f t h e i r l e s s e r e l e c t r o n d e n s i t y i n b r i g h t f i e l d c o n d i t i o n s . I n some c a s e s , t h e s e i r r a d i a t e d a r e a s c o u l d a l s o be seen u n d e r d a r k f i e l d c o n d i t i o n s .

French and Gardner; Fiber Diffraction Methods ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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Ultrathin Textile Fibers

Figure 1.

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A slide with 5 exposures on the same emulsion.

In the lower left corner, zone (arrowed) of the cross section of an Ag S stained PA 66 fiber, which is responsible for crystalline pattern 1. Numbers 1, 2, and 3 are three successive exposures of the same pattern with an equal radiation rate—notice progressive fading of the outer, less intense (010) arc A: amorphous pattern (photographed in the same conditions) corresponding to the same area. s

French and Gardner; Fiber Diffraction Methods ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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Q u a n t i t a t i v e P r o c e s s i n g . P l a t e s or f i l m w i t h the d i f f r a c t i o n p a t t e r n s were scanned w i t h a J o y c e - L o e b l m i c r o d e n s i t o m e t e r . R a d i a l (20) d e n s i t o m e t r i c p l o t s o f the c r y s t a l l i n e p a t t e r n ( e v e n t u a l l y t h r e e s u c c e s s i v e e x p o s u r e s o f the c r y s t a l l i n e p a t t e r n are analyzed) and of the c o r r e s p o n d i n g amorphous p a t t e r n were r e c o r d e d on the same c u r v e . In t h i s way, the p l o t o f the amorphous p a t t e r n was used as a r e f e r e n c e s t a n d a r d . The d e n s i t o m e t r i c r e c o r d i n g began w i t h the o p t i c a l d e n s i t y of the n o n - i r r a d i a t e d e m u l s i o n ; t h i s a l l o w e d the e v a l u a t i o n and n o r m a l i z a t i o n o f the o p t i c a l d e n s i t y o f the d i f f r a c t i o n p a t t e r n . When the a n a l y t i c a l s l i t p a s s e d t h r o u g h the image o f the b o r d e r o f the 75 ym o b j e c t i v e a p e r t u r e , the d e n s i t o m e t r i c c u r v e showed a sudden d e n s i t y r a i s e " A d . ( F i g . 6) The p l o t s o f the amorphous and c r y s t a l l i n e p a t t e r n s were thus n o r m a l i z e d t o the same r e f e r e n c e " A d" . C r y s t a l l i n i t y was determined on the n o r m a l i z e d c u r v e s by measuring the areas "C + A" and "A" under the c r y s t a l l i n e and amorphous p l o t s r e s p e c t i v e l y . In some c a s e s , an " a z i m u t a l c o r r e c t i o n " was app l i e d by the f o l l o w i n g method : an a z i m u t a l p l o t o f the d i f f r a c t e d i n t e n s i t y was o b t a i n e d u s i n g a p o l a r c o o r d i n a t e s t a b l e . The c o r r e c t i v e f a c t o r f o r "C/A" was e/e where i s the a r e a under the a z i m u t a l p l o t and e i s the a r e a o f the r e c t a n g l e h a v i n g the same base and w i t h the h e i g h t e q u a l t o the maximum d e n s i t y o f the a z i m u t a l p l o t . C o r r e c t e d o r u n c o r r e c t e d C v a l u e s were t r a n s f o r m e d t o C% v a l u e s by means o f the A C formula : % A 1 + C A M

Q

Q

1

c

0

0

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which h o l d s f o r C% v a l u e s near b u t n o t e q u a l t o 100 because we have no f u l l y c r y s t a l l i n e s t a n d a r d .

%

Dark F i e l d M i c r o g r a p h s . Dark f i e l d m i c r o g r a p h s were o b t a i n e d by i s o l a t i n g a main d i f f r a c t i o n a r c on the m i c r o d i f f r a c t i o n p a t t e r n and, by t i l t i n g the e l e c t r o n beam a t a c o r r e c t a n g l e , r e c o r d i n g the image w i t h the d i f f r a c t e d beam o n l y . F o r the p o l y e s t e r , we have n o t been a b l e as y e t t o o b t a i n such m i c r o g r a p h s o f acceptable q u a l i t y .

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F o r 66 p o l y a m i d e , we have o b t a i n e d a c c e p t a b l e r e s u l t s by s e l e c t i n g the s t r o n g e r r e f l e c t i o n , t h a t i s i n gener a l the n e a r e s t one t o t h e c e n t e r o f the p a t t e r n ( i n the t r a n s v e r s e s e c t i o n ) .

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Results 2GT p o l y e s t e r . F i g u r e 2 i s a montage showing t h e c r o s s - s e c t i o n o f a t e x t u r e d p o l y g o n a l - s h a p e d PETP s t r a n d s t a i n e d w i t h Ag 2 s ; the m e t a l i s e s s e n t i a l l y p e r i p h e r i c w i t h some r a d i a l i n c l u s i o n s . The d i f f r a c t i o n p a t t e r n s o f 5 d i f f e r e n t s e l e c t e d areas a r e a l s o p r e s e n t . I r r a d i a t e d areas and s e l e c t e d areas c a n be r e s o l v e d b y t h e i r h i g h e r t r a n s m i s s i o n . There i s c o n s i d e r a b l e v a r i a t i o n i n the azimutal width o f the 3 main d i f f r a c t i o n a r c s w h i l e t h e o r i e n t a t i o n o f t h e e q u a t o r i s o n l y s l i g h t l y v a r i a b l e . On t h i s montage (as w e l l as on t h e f o l l o w i n g o n e s ) , t h e d i f f r a c t i o n p a t t e r n s have been p o s i t i o n e d i n t h e i r t r u e s p a t i a l p o s i t i o n , a f t e r c o r r e c t i o n o f t h e image r o t a t i o n depending on m a g n i f i c a t i o n and on camera l e n g t h . F i g u r e 3 i s another example on A g S s t a i n e d PETP w i t h 3 s e l e c t e d a r e a s , t h e d i f f r a c t i o n p a t t e r n s o f w h i c h have q u a s i - p a r a l l e l e q u a t o r s . F i g u r e 4 c o r r e s p o n d s t o PETP^ ( A g S s t a i n e d ) w i t h 12 d i f f e r e n t s e l e c t e d a r e a s and c o r r e s p o n d i n g d i f f r a c t i o n p a t t e r n s . One c a n see t h a t : 5 p a t t e r n s have t h e same o r i e n t a t i o n , 3 a r e p r a c t i c a l l y a t r i g h t a n g l e s from t h e l a t t e r , 2 have an i n t e r m e d i a t e o r i e n t a t i o n and t h e l a s t 2 are h i g h l y d i s o r i e n t e d , w i t h one Debye S c h e r r e r type p a t t e r n . F i g u r e 5 i s an example o f a d e n s i t o m e t r i c p l o t f o r PETP,. The s h o u l d e r c o r r e s p o n d i n g t o t h e "amorphous h a l o " o f t h e d e s t r o y e d p a t t e r n i s c l e a r l y v i s i ble. The n o r m a l i z a t i o n p r o c e d u r e i s i l l u s t r a t e d : i n t h a t s p e c i f i c c a s e , t h e amorphous p a t t e r n i s u n d e r exposed i n comparison w i t h t h e c r y s t a l l i n e p a t t e r n . Point A corresponds t o the o p t i c a l d e n s i t y d of the background o f t h e s l i d e ( t h a t i s o u t s i d e t h e image o f the b o r d e r o f t h e o b j e c t i v e a p e r t u r e ) ; p o i n t B corresponds t o the " i n i t i a l " d e n s i t y d o f the c r y s t a l l i n e p a t t e r n and B t o t h e " i n i t i a l " d e n s i t y o f t h e amorphous p a t t e r n ; i f t h e c r y s t a l l i n e p l o t i s t a k e n as t h e r e f e r e n c e , t h e amorphous p l o t d e n s i t y has t o be m u l t i p l i e d by t h e n o r m a l i z a t i o n f a c t o r e i . e . 2

2

Q

Q

1

French and Gardner; Fiber Diffraction Methods ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

O

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286

FIBER

Figure 2.

DIFFRACTION

METHODS

Cross section of a textured polygonal-shaped PETP strain stained with Ag S. t

The photograph (positive print) of the cross section of the fiber has been cut around with scissors, leaving a small amount of embedding araldite around the fiber-end stuck on a "bristoV paper The diffraction patterns were stuck close to the corresponding areas (to which they are related by arrows) and their orientations are corrected according to the image j diagram rotation introduced by the microscope.

Figure 3.

Ag S-stained PETP with three selected areas, the diffraction patterns of which have quasi-parallel equators fsee also Figure 2) t

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Figure 4.

Ultrathin Textile Fibers

287

Ag S-stained PETP with 12 different selected areas and corresponding diffraction patterns (see also Figure 2) t

S

Figure 5.

Densitometric plot for PETP

t

French and Gardner; Fiber Diffraction Methods ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

288

d

FIBER

o

- d

DIFFRACTION

METHODS

oo

- d oo Table I.

Electron diffraction crystallinity

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PETP

1

PETP, 2

X-Ray c r y s t a l l i n i t y (RULAND's Method)

28,8

%

27,0

%

33,4

%

32,0

%

66 Polyamide^ F i g u r e s 6 and 7 are montages o f 66 p o l y a m i d e . The d i f f r a c t i o n p a t t e r n s are much c l o s e r t o "powder" type t h a n were the PETP p a t t e r n s . In f i g u r e 8 the a l t o g e t h e r v i e w i s i n dark f i e l d conditions and the 5 d e s t r o y e d zones appear v e r y clearly. F i g u r e s 8 and 9 are d e n s i t o m e t r i c p l o t s o f v a r i o u s k i n d s o f p a t t e r n s . In f i g u r e 8, the p r o c e d u r e f o r the n o r m a l i z a t i o n o f the amorphous p l o t i s f u r t h e r e x p l a i n e d . In t h i s c a s e one has t o m u l t i p l y each i n d i v i d u a l d e n s i t y by the f a c t o r #

oo

. T h i s g i v e s the c o r r e c t e d curve (dashed l i n e ) and l e a d s t o t h e e v a l u a t i o n o f the - d o oo " C " and "A" v a l u e s . In f i g u r e 9, c r y s t a l l i n e p l o t s o f the same a r e a (two s u c c e s s i v e photographs) are shown. The f a d i n g o f the weaker l i n e i s v i s i b l e , b u t n e v e r t h e l e s s , t h e r e i s o n l y a minor v a r i a t i o n o f the a r e a under the whole c r y s t a l l i n e curve. F i g u r e 10 shows an example o f an a z i m u t a l scan, t o g e t h e r w i t h the e x p l a n a t i o n o f the " a z i m u t a l c o r r e c t i o n " . The s t r i p e d a r e a i s d i v i d e d by the a r e a o f the r e c t a n g l e b u i l t on the dashed l i n e s .

French and Gardner; Fiber Diffraction Methods ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

289

Ultrathin Textile Fibers

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Figure 6. Montage of 66 polyamide (see also Figure 2)

Figure 7.

Montage of 66 polyamide (see also Figure 2)

French and Gardner; Fiber Diffraction Methods ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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290

FIBER DIFFRACTION

METHODS

Figure 8. Densitometric plot of various kinds of patterns. The fiber is photographed in darkfieldconditions as opposed to other montages. (See also Figure 2.)

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Ultrathin Textile Fibers

Figure 9.

Densitometric plot of various kinds of patterns

PA 66 T y p e

4

Cross section - Azimutal scan

Figure 10.

Example of an azimuthal scan

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T a b l e I I g i v e s the c r y s t a l l i n i t y v a l u e s f o r v a r i o u s k i n d s o f p o l y a m i d e y a r n s . I n one c a s e , the o c c u r e n c e o f a r e l a t i v e l y amorphous s k i n can be d e t e c t e d . There i s a l s o an example o f t h e e f f e c t o f an a z i m u t a l c o r r e c t i o n . A b s o l u t e c r y s t a l l i n i t y v a l u e s do n o t agree w e l l w i t h X - r a y based c r y s t a l l i n i t y v a l u e s . N e v e r t h e l e s s , t h e r e i s a g e n e r a l q u a l i t a t i v e agreement i n the d i f f e r e n c e between polyamide and p o l y e s t e r y a r n s ( i t i s w e l l known t h a t c r y s t a l l i n i t y i s g e n e r a l l y h i g h e r f o r polyamide than f o r p o l y e s t e r commercial f i l a m e n t s ) . I n t a b l e I I I , the " c r y s t a l l i n i t y " v a r i a t i o n s e s t i m a t e d a f t e r m u l t i p l e i r r a d i a t i o n s are shown. In s p i t e o f t h e d e g r a d a t i o n which i s c l e a r l y n o t i c e a b l e ( g r a d u a l f a d i n g o f the weaker i n t e r f e r e n c e ) the e s t i mated c r y s t a l l i n i t y o f t e n shows v e r y l i m i t e d d e c r e a s e (the s t a n d a r d d e v i a t i o n s are a p p r o x i m a t e l y 8 % ) . F i g u r e s 11 t o 13 are d a r k f i e l d m i c r o g r a p h s o f 66 polyamide m o n o f i l a m e n t s . F i g u r e 11 show an A g S s t a i n e d f i l a m e n t . S i l v e r s u l f i d e p r e c i p i t a t e s , which appear as b l a c k areas (as t h e y d i d i n b r i g h t f i e l d images) as w e l l as polyamide c r y s t a l l i t e s ( b r i g h t spots) are v i s i b l e . F i g u r e 12 c o r r e s p o n d s t o a t y p e 4 f i b e r ( w i t h s k i n - c o r e morphology) where t h e r e i s a lower d e n s i t y o f c r y s t a l l i t e s i n the s k i n r e g i o n . F i g u r e 13 c o r r e s p o n d s t o the c a s e o f type 5 f i b e r which has s m a l l e r c r y s t a l l i t e s . 2

Discussion L o c a l O r i e n t a t i o n . The most s t r i k i n g o b s e r v a t i o n o f t h i s work i s t h a t the s e l e c t e d a r e a d i f f r a c t i o n p a t t e r n s are not i n g e n e r a l o f a Debye-Scherrer t y p e . Among t h e v a r i o u s h y p o t h e s e s which can be drawn t o u n d e r s t a n d such a f a c t , the most p r o b a b l e one i s t h a t the s e c t i o n s are n o t t r u l y t r a n s v e r s e ones ; i n d e e d , i f one supposes the e x i s t e n c e o f a c y l i n d r i c a l symmet r y a t the l e v e l o f each s e l e c t e d a r e a , 0.5 t o 1 ym i n d i a m e t e r (the symmetry a x i s b e i n g always p a r a l l e l t o the f i b e r a x i s ) the " d e t e c t a b l e " network main p l a n e s have t o be p a r a l l e l t o the " c " a x i s o f the i n d i v i d u a l

French and Gardner; Fiber Diffraction Methods ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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Table II.

Type* 4

293

Crystallinity of PA 66-C%

Type 4 (+Ag S) 2

Type 5

Type 2 (+Ag S) 2

Core

Without Skin azimutal corr.

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o n

With azimutal corr. o n

%

%

%

%

38,5

32,3

51,6

36,4

6,2

8,2

4,4

6

Table III.

%

°/o

44,1

57,6

Mean

9,7

7,8

Standard deviation

Type 2 Polyamide Degradation of the Diffraction Pattern

N° of the C r i s t a l l i n i t y % after selected the 1st i r s a d . the 3rd i r r a d . the 2nd i r r a d . area 68,9

66,3

56,2

55,3

53,3

63,4

61,5

62,7

65,0

63,8

65,4

63,5

61,3

58,8

55,5

46,7

45,4

45,1

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294

FIBER

Figure 11.

DIFFRACTION

METHODS

Dark field micrograph of 66 polyamide microfilaments

Figure 12. Dark-field micrograph of the cross section of an Ag S-stained Type 2 (see text) PA 66 fiber. Notice black deposits of silver sulfide in the periphery and white dots in the whole section, corresponding to crystallites in Bragg position. 2

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17.

HAGEGE

Ultrathin Textile Fibers

295

Figure 13. Dark-field micrograpn oj tne cross section of a Type 4 PA 66 fiber. No silver sulfide deposits; notice the skin-core effect and the dimensions of the crystallites (white dots).

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296

FIBER

DIFFRACTION

METHODS

c r y s t a l l i t e s , and t h e i r angle w i t h the i n c i d e n t beam has t o be e q u a l t o the Bragg angle 0. F o r a rough e s t i m a t e , one can n e g l e c t t h i s Bragg angle ( t h i s i n f a c t i s v e r y s m a l l because o f the low v a l u e o f the wavelength a s s o c i a t e d t o the e l e c t r o n s ) and a l s o the mean o r i e n t a t i o n angle o f the c - a x i s o f the i n d i v i d u a l c r y s t a l l i t e s ( p e r f e c t o r i e n t a t i o n ) . In such a s i t u a t i o n the " v i s i b l e " network p l a n e s have a c o n s t a n t o r i e n t a t i o n i n space ; t h e y must be p a r a l l e l t o the i n c i d e n t beam and t o the f i b e r - a x i s . The e q u a t o r o f the r e s u l t i n g d i f f r a c t i o n p a t t e r n i s normal t o these p l a n e s , i . e . , normal t o t h e l o n g a x i s o f the t h e o r e t i c a l l y e l l i p t i c s e c t i o n . As a s u p p o r t t o t h i s h y p o t h e s i s , the e q u a t o r s o f v a r i o u s l o c a l d i f f r a c t i o n p a t t e r n s are most f r e q u e n t l y p a r a l l e l t o one a n o t h e r . T h i s i s n o t o n l y t r u e f o r the same c r o s s s e c t i o n b u t a l s o i n d i f f e r e n t f i b e r s which have been s e c t i o n e d as an embedded bundle o f p a r a l l e l f i b e r s . N e v e r t h e l e s s , we were n o t a b l e t o f i n d any r e l a t i o n s h i p b e t ween the o r i e n t a t i o n o f the l o n g a x i s o f the pseudo e l l i p t i c a l s e c t i o n and t h a t o f the e q u a t o r o f the d i f f r a c t i o n pattern. F i g u r e 14 i s a scheme o f the s e c t i o n (S) t h a t was c u t s l i g h t l y o b l i q u e t o the f i b e r a x i s ( A Q ) • the beam a x i s (I) impinges n o r m a l l y i n the c e n t e r o f the s e l e c t e d a r e a (S) ; a cone o f r e v o l u t i o n (C) has been drawn round the a x i s ( A ) , p a r a l l e l t o ( A Q ) and i s supposed t o be a l o c a l r e v o l u t i o n symmetry a x i s . The angle 0 o f t h i s cone c o r r e s p o n d s t o the mean o r i e n t a t i o n o f the c - a x i s o f t h e i n d i v i d u a l c r y s t a l l i t e s ; another r e v o l u t i o n cone ( e ) i s centered around (I) : i t s angle 0 i s one o f the main Bragg a n g l e s (0 i s g e n e r a l l y much s m a l l e r than 0}. "DetectabJe" network p l a n e s show two main f e a t u r e s : they are t a n g e n t t o ( e ) and t h e y c o n t a i n one g e n e r a t o r o f the cone ( C ) . A p l a n e normal t o (I) i n t e r c e p t s on (C) as an e l l i p s a (E) and on ( e ) a s a s m a l l c i r c l e Q

Q

( Y

o>-

In f i g u r e 15, examples o f these two g e o m e t r i e s are shown. T r a c e s o f the d e t e c t a b l e network p l a n e s must have an o r i e n t a t i o n comprised between the two i n t e r n a l common t a n g e n t s t o ( Y ) and (E) ? i t i s t h u s p o s s i b l e t o b u i l d g e o m e t r i c a l l y (as the f i g u r e shows)

French and Gardner; Fiber Diffraction Methods ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Ultrathin Textile Fibers

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Figure 14. Similar to Figure 13, but with Type 5 PA 66 fiber (the cross sections have been thermally treated; notice very tiny, well-defined crystallites)

French and Gardner; Fiber Diffraction Methods ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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298

FIBER

DIFFRACTION

METHODS

Figure 15. (Lett) Case of PETP: constant local orientation and variable local rotation axis; (right) case of PA 66; variable local orientation and constant local rotation axis

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17.

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the a z i m u t a l opening o f t h e i n t e r f e r e n c e c o r r e s p o n d i n g to t h e Bragg angle 0 . There a r e two d i f f e r e n t ways t o g e t l o c a l d i f f r a c t i o n p a t t e r n s "Debye-Scherrer" type (such p a t t e r n s a r e o b t a i n e d i f ( y ) i s found w i t h i n (E) . I n t h e f i r s t case ( f i g u r e 15? the o r i e n t a t i o n o f the l o c a l symmetry a x i s ( A ) i s v e r y c l o s e t o t h a t o f (I) w i t h the c o n s e quence triat the whole cone ( e ) i s l o c a t e d w i t h i n t h e cone (C) even i f the l o c a l o r i e n t a t i o n i s r e l a t i v e l y good, i . e . , angle 0 i s s m a l l . I n the second case, the l o c a l o r i e n t a t i o n i s poorer, i . e . , 0 i s f a i r l y l a r g e . As a r e s u l t 0 and a) (angle between ( A ) and ( I ) ) have e q u i v a l e n t v a l u e s and a g a i n cone (C) surrounds cone ( e ) . The f i r s t case may c o r r e s p o n d t o PETP i n which t h e r e would be a n o t i c e a b l e d i s p e r s i o n o f t h e l o c a l symmetry a x i s around f i b e r a x i s . T h i s c o u l d e x p l a i n the r e l a t i v e l y f r e q u e n t v a r i a t i o n s i n t h e o r i e n t a t i o n of the d i f f r a c t i o n p a t t e r n i n t h e s p e c i f i c case o f PETP. The second case would c o r r e s p o n d t o 66 polyamide which h a s l o c a l v a r i a t i o n s o f o r i e n t a t i o n and l e s s o v e r a l l o r i e n t a t i o n t h a n i n PETP. The two c a s e s a r e p r e s e n t e d i n f i g u r e 15. Local C r y s t a l l i n i t y . The " a z i m u t a l c o r r e c t i o n " p r e v i o u s l y mentioned s h o u l d be a p p l i e d o n l y i n t h e second case d i s c u s s e d above, i . e . , when t h e v a r i a t i o n of the l o c a l o r i e n t a t i o n i s the main f a c t o r i n a f f e c t i n g t h e observed d i f f r a c t i o n p a t t e r n . I n t h i s s p e c i f i c c a s e , t h e d i f f r a c t e d i n t e n s i t y i s spread over t h e whole i n t e r f e r e n c e . As a r e s u l t , t h e c o r r e c t i o n s h o u l d be made f o r 66 polyamide and n o t f o r PETP. T h i s c o r r e c t i o n c o u l d have a l a r g e e f f e c t and would r e s u l t i n l o w e r i n g the c r y s t a l l i n i t y d i f f e r e n c e s between the two kinds o f f i b e r s . This azimutal c o r r e c t i o n gives a bett e r account o f the whole a z i m u t a l i n t e n s i t y than t h e n o r m a l i z a t i o n o f t h e h a l f - h e i g h t w i d t h v a l u e as p r o p o sed i n another paper ( 1 0 ) . Nevertheless, numerical values obtained i n the p r e s e n t work are p r e l i m i n a r y r e s u l t s and f u r t h e r exp e r i m e n t s are underway. A t the moment, we are unable t o say whether s e c t i o n t h i c k n e s s c a n i n f l u e n c e t h e c r y s t a l l i n i t y v a l u e s o b t a i n e d even t h r o u g h the use of "c" t e c h n i q u e . A

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( T h i s method p a r t i a l l y e l i m i n a t e s the i n f l u e n c e o f t h e t r a n s m i s s i o n o f the sample " y t " f a c t o r ) . Moreover, i t seems r e a s o n a b l e t h a t the s e c t i o n s l a c k p l a n a r i t y and have a t i l t i n g a r t i f a c t i n a t l e a s t p a r t o f the c r y s t a l l i t e s due t o the a c t i o n o f the k n i f e . These f a c t o r s might have a l a r g e i n f l u e n c e on the v a r i a t i o n s o f o r i e n t a t i o n and i n t e n s i t y o f the l o c a l d i f f r a c t i o n p a t t e r n s .

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Conclusion We have p r e s e n t e d p r e l i m i n a r y r e s u l t s on s e l e c t e d area e l e c t r o n d i f f r a c t i o n of "pseudotransverse" u l t r a t h i n s e c t i o n s o f PETP and PA66 f i l a m e n t s . These r e s u l t s suggest t h a t the c l a s s i c a l h y p o t h e s i s o f r e g u l a r c y l i n d r i c a l symmetry i n c i r c u l a r - s h a p e d s y n t h e t i c f i l a m e n t s i s i n c o r r e c t . A l t h o u g h the b e s t way t o study l o c a l v a r i a t i o n s o f o r i e n t a t i o n i s t o work on l o n g i t u d i n a l s e c t i o n s , our r e s u l t s s t r o n g l y s u g g e s t t h a t the c y l i n d r i c a l symmetry has t o be c o n s i d e r e d a t the l e v e l o f a s m a l l a r e a o f l e s s than 1 ym i n d i a m e t e r (and p r o b a b l y much l e s s ) and not a t the l e v e l o f the whole f i l a m e n t , as X - r a y d i f f r a c t o m e t r y has s u g g e s t e d . However, i n PETP, a p o s s i b l e d i s p e r s i o n i n the o r i e n t a t i o n o f l o c a l symmetry a x i s , around the f i l a m e n t a x i s , i s t o be c o n s i dered. The c r y s t a l l i n i t y i n d e x , as o b t a i n e d u s i n g the "amorphous" d i f f r a c t i o n p a t t e r n (by d e s t r u c t i o n o f l o c a l o r d e r under the e l e c t r o n beam) g i v e s r e l i a b l e i n f o r m a t i o n , i . e . , i n agreement w i t h dark f i e l d images. I t should be emphasised t h a t the s e a r c h and p h o t o graphy o f the d i f f r a c t i o n p a t t e r n ( u s i n g the p r o c e d u r e s o u t l i n e d above) does n o t b r i n g about major d e g r a d a t i o n o f the o r i g i n a l c r y s t a l l i n i t y . T h i s i s p o s s i b l y i n p a r t due t o our use o f a h i g h vacuum e l e c t r o n m i c r o s c o p e , i n which the r a t e o f c o n t a m i n a t i o n o f the sample i s small. Acknowledgments The author wishes t o thank the workers o f the l a b o r a t o r y f o r t e c h n i c a l a s s i s t a n c e and the "RHONE POULENC TEXTILE" S o c i e t y f o r f i n a n c i a l s u p p o r t o f p a r t o f the p r e s e n t work.

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Literature cited 1. HARRIS, P . H . , 5th i n t e r n , Acad. Press. N.Y. (1962)

cong.

for E l e c . Micr. BB-8

2. SCOTT, R . G . , Symposium on resinographic methods s p e c i a l t e c h n i c a l p u b l i c a t i o n N 60348 ASTM (1963)

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3. BULEON, A . , CHANZY, H., HAGEGE, R . , B u l l . 4, 229-233 (1975)

Scien.ITF

4. MURRAY, R., DAVIS, H . A . , TUCKER, P . , J. Appl. Sci., 33, 177-196 (1978)

Polym.

5. Brevet, Francais, DU PONT, n ° 2, 134, 582, Enregistrement n ° 15,014 (1972) 6. DOBB, M . C . , JOHNSON, D.J., SAVILLE, B.P., J. Polym. S c i . Polym. Phys., 15, 2201 (1977) 7. DOBB, M . C . , JOHNSON, D.J., SAVILLE, B . P . , J. Polym. S c i . Polym. Symp., 58, 237-251 (1977) 8. SOTTON, M . , C . R. Acad. S c i . Paris 270B (1970) 9. DOBB, M . C . , MURRAY, R . , J. Micros. 101, 299-309 (1974) 10.

SOTTON, M . , ARNIAUD, A . M . , RABOURDIN, C., J. Appl. Polym. Sci., 22, 2585-2608 (1978).

RECEIVED May 21,

1980.

French and Gardner; Fiber Diffraction Methods ACS Symposium Series; American Chemical Society: Washington, DC, 1980.