Cellulose and Fiber Science Developments: A World View

In connection with my earlier reference to person. -accomplishments ... (CF2 )e. I. 0. I. Η. 0. Figure 7. Fluorochemicals. FLUOROCHEMICAL EVENLY DIST...
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11 Recent Canadian Developments in Fiber Science D. M. WILES

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Chemistry Division, National Research Council of Canada, Ottawa, Canada K1A 0R9

Although it undoubtedly doesn't come close to matching the level of activity in the USA, textile r e s e a r c h and development i n Canada p r o b a b l y does approximate in scope the American endeavours in the same area. In other words although there is a very large difference in scale of R&D between our two countries, consumers expect the same varieties of products and so a similar array of textile technologies is called for. In many instances, such technologies cannot be based uniquely on Canadian science; there isn't enough of it. It is frequently both desirable and possible to import appropriate technologies and, in numerous instances, American technology is used. Nevertheless, it is obvious that scientific and innovative advancements are not restricted by national boundaries and a brief account of some Canadian developments in textile and fiber science may be of interest. I propose to describe five different kinds of R&D activities; these examples have been selected arbitrarily although not necessarily at random. It is hoped that this spectrum of "case histories" will represent the scope of Canadian activities. This is of course, an account of people rather than of laboratories or institutions. I

N o v e l Yarn Manufacture

No d e s c r i p t i o n o f Canadian achievements i n t e x t i l e s R&D would be complete w i t h o u t r e f e r e n c e t o the major advances i n t r o d u c e d by the Bobtex C o r p o r a t i o n of Montreal. Most o f you will have h e a r d Dr. Andrew Bobkowicz ( o r one o f h i s c o l l e a g u e s ) d e s c r i b e h i s company's I n t e g r a t e d Composite S p i n n i n g System ( F i g u r e 1) i n more d e t a i l than can be accommodated i n 219

In Cellulose and Fiber Science Developments: A World View; Arthur, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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CELLULOSE AND FIBER SCIENCE

this lecture. F i g u r e 2 i l l u s t r a t e s the p r o c e s s i n g concept, and F i g u r e 3 shows a model o f a t h r e e component ICS y a r n . Of the many p o t e n t i a l advantages f o r t h i s y a r n making system, a few r e l a t i n g to v e r s a t i l i t y and e f f i c i e n c y are as f o l l o w s : ( i ) a wide range o f ICS y a r n c o m p o s i t i o n s ; ( i i ) y a r n e n g i n e e r i n g t o meet s p e c i f i c end use a p p l i c a t i o n s ; ( i i i ) h i g h p r o d u c t i o n speeds; ( i v ) lower y a r n m a t e r i a l c o s t s . The f l e x i b i l i t y o f the concept and the machinery i s r e f l e c t e d i n the f o l l o w i n g c o m p o s i t i o n a l o p t i o n s : F i b e r s - 30 to 60%; T h e r m o p l a s t i c polymer - 20 t o 50%; Carrier f i l a m e n t ( s ) - 10 t o 60?. T h i s Bobtex b r e a k t h r o u g h , o f which the Canadian s c i e n t i f i c and t e c h n o l o g i c a l community i s very proud, i s a t y p i c a l "overnight" success. I t i s based on many y e a r s o f d i f f i c u l t , e x p e n s i v e , fundamental r e s e a r c h and i t has r e l i e d upon the complete d e d i c a t i o n as w e l l as the i n n o v a t i v e genius o f i t s i n v e n t o r s i n o r d e r t o r e a c h the* m a r k e t p l a c e . The impact o f ICS yarn manufacturing technology i s only j u s t beginning to be apparent, f o l l o w i n g the ITMA 75 demonstration and the concomitant announcement o f the n o n - e x c l u s i v e l i c e n s e arrangement under which the Leesona Corpor a t i o n ( T e x t i l e Machinery D i v i s i o n ) i s a b l e t o manuf a c t u r e and s e l l the Bobtex ICS equipment on a worldwide b a s i s . T

II

T r i a c e t a t e Polypropylene

Carpet F i b e r s

A second example o f Canadian i n d u s t r i a l R&D i n t e x t i l e and f i b e r s c i e n c e i s the development at Celanese Canada L t d . o f c e l l u l o s e t r i a c e t a t e and polypropylene carpet yarns. While the use o f t h i s example c o n s i d e r a b l y s t r e t c h e s the meaning o f the word " r e c e n t " i n the t i t l e o f t h i s t a l k , i t a l s o r e p r e s e n t s a m u l t i - m i l l i o n d o l l a r b u s i n e s s based on p a t e n t s and p r o c e s s e s which were unique t o Canada at the time. While i t i s by no means a t e c h n i c a l l y a c c e p t a b l e d e s c r i p t i o n o f the r e s e a r c h performed at the Celanese Canada l a b o r a t o r i e s , the essence o f what was accomp l i s h e d i s i n d i c a t e d i n the next t h r e e F i g u r e s : F i g u r e 4 r e f e r s to the Palmer-Larue p r o c e s s ; F i g u r e 5 r e f e r s t o p o l y p r o p y l e n e c o l o r a t i o n and e x t r u s i o n ; F i g u r e 6 l i s t s the f u r t h e r p r o c e s s i n g p r o c e d u r e s as w e l l as the end p r o d u c t o f the e n t i r e R&D e f f o r t . As f a r as I know, these p o l y p r o p y l e n e / c e l l u l o s e t r i a c e t a t e p i l e y a r n c a r p e t s are s t i l l unique t o Canada. I know from p e r s o n a l e x p e r i e n c e t h a t these c a r p e t s

In Cellulose and Fiber Science Developments: A World View; Arthur, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

WILES

Canadian Developments in Fiber Science

The w o r l d s T

first

integrated

composite s p i n n i n g system To combine c o n t i n u o u s f i l a m e n t p r o p e r t i e s w i t h p o l y m e r r e s i n economics and s t a p l e

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f i b e r o u t e r t e x t u r e and a e s t h e t i c s i n t o a new t y p e o f c o m p o s i t e spun y a r n . Figure 1. Bobtex ICS process

ICS YARN PACKAGE

Figure 2. ICS process diagram

CARRIER POLYMER STAPLE FIBER

Figure S. Model of a threecomponent ICS yarn

In Cellulose and Fiber Science Developments: A World View; Arthur, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

222

CELLULOSE AND FIBER SCIENCE

- Development o f the Palmer-Larue the

process f o r

melt-spinning of c e l l u l o s e

triacetate

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fibers - Development o f a c o n t i n u o u s c o l o r - s p i n - d r a w crimp p r o c e s s

(>100

man

y e a r s o f R & D)

- More than 100,000,000 l b s . o f melt triacetate

carpet f i b e r s

spun

produced.

Figure 4. Celanese triacetate RirD

- C o l o r a t i o n o f the f i b e r s by b l e n d i n g pigments

w i t h p o l y p r o p y l e n e i n powder

form - Design and development u s i n g apparatus remains one

o f melt e x t r u d e r s

i n which

i n a molten

the

polymer

state for less

than

minute. Figure 5.

Celanese polypropylene Rà-D

In Cellulose and Fiber Science Developments: A World View; Arthur, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

11.

WILES

r e p r e s e n t as good a c a r p e t v a l u e as one can buy. In c o n n e c t i o n w i t h my e a r l i e r r e f e r e n c e t o p e r s o n - a c c o m p l i s h m e n t s , I w i s h t o draw y o u r a t t e n t i o n t o t h e f o l l o w i n g item. The same s c i e n t i s t who headed t h e Celanese r e s e a r c h team i n the 1 9 5 0 s and e a r l y 6 0 s has s u b s e q u e n t l y d i r e c t e d t h e development o f an e n t i r e l y d i f f e r e n t type o f c a r p e t y a r n i n the l a b o r a t o r i e s o f a d i f f e r e n t company. I n t h i s l a t t e r i n s t a n c e t h e new c a r p e t y a r n i s f o u r - p l y and c o n s i s t s o f t h r e e d i f f e r e n t l e v e l s o f d y e a b i l i t y o f nylon yarns together w i t h a conducting monofilament o f nylon t o impart a n t i s t a t i c p r o p e r t i e s . N e e d l e s s t o s a y , the concept i s not a Canadian i n v e n t i o n , b u t the n o v e l t e c h n o l o g y w h i c h was d e v e l o p e d i n Canada was b o t h p a t e n t a b l e and saleable. As I l e a v e the i n d u s t r i a l s i d e o f t h i s R&D s u r v e y , I would l i k e t o n o t e t h a t b o t h examples I have d e s c r i b e d r e s u l t e d i n the p r e s e n t a t i o n o f the Canadian T e x t i l e S c i e n c e Award, t o E m i l i a n and Andrew Bobkowicz and t o Dr. W a l t e r Palmer i n 1971 and 1 9 7 3 , r e s p e c t i vely. Thus, w h i l e my s e l e c t i o n o f examples was a r b i t r a r y , i t was by no means done randomly. f

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Canadian Developments in Fiber Science

Ill

Fluorochemical

!

Fabric Finishes

T h i s example comes from a m i l i t a r y m a t e r i a l s l a b o r a t o r y i n w h i c h much o f the r e s e a r c h r e l a t e s t o improved methods f o r p r o v i d i n g p r o t e c t i o n f o r m i l i tary personnel. The i n v e s t i g a t i o n , under the d i r e c t i o n o f Dr. John M c A n d l e s s , i n v o l v e d a s t u d y o f l i q u i d r e p e l l e n t f i n i s h e s , on the f a b r i c m a t e r i a l s used i n m i l i t a r y c l o t h i n g , t o provide p r o t e c t i o n against w e t t i n g by r a i n and o t h e r l i q u i d s such as o i l s , f u e l s and c h e m i c a l a g e n t s . C e r t a i n f l u o r i n e - c o n t a i n i n g polymers are unique i n t h e i r a b i l i t y t o r e p e l b o t h w a t e r and o i l y f l u i d s , and common f l u o r o c h e m i c a l r e p e l l e n t s i n c l u d e p o l y m e r s o f f l u o r o a l k y l a c r y l a t e (and m e t h a c r y l a t e ) e s t e r s as shown i n F i g u r e 7. The a b i l i t y o f f l u o r o c h e m i c a l s t o p r o t e c t f a b r i c s from b e i n g w e t t e d by l o w s u r f a c e t e n s i o n o i l y l i q u i d s r e s u l t s from the i n h e r e n t low s u r f a c e energy o f p e r f l u o r o m e t h y l ( C F 3 ) groups w h i c h form the outermost l a y e r o f the f l u o r i n a t e d s u r f a c e . The s u r f a c e c o n d i t i o n s n e c e s s a r y f o r p r o d u c i n g e f f e c t i v e l i q u i d r e p e l l e n c y are shown i n F i g u r e 8 . The r e q u i r e d p a c k i n g o f C F groups i s u s u a l l y a c h i e ved by e m p l o y i n g p o l y m e r i c compounds c o n t a i n i n g s t r a i g h t chain, f u l l y f l u o r i n a t e d substituents having a minimum o f 8 carbon u n i t s i n l e n g t h , w i t h t h e s u b s t i t u e n t s o r i e n t e d p e r p e n d i c u l a r t o the f a b r i c 3

In Cellulose and Fiber Science Developments: A World View; Arthur, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

CELLULOSE AND FIBER SCIENCE

- Combination

of a l l the unit operations

i n t o one c o n t i n u o u s p r o c e s s spinning, and

including

drawing, crimping, c u t t i n g ,

baling.

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- Use o f p o l y p r o p y l e n e f i b e r s i n b l e n d s w i t h t r i a c e t a t e f i b e r s t o produce

a

low s t a t i c , dense, h a r d t w i s t c a r p e t o f good wear r e s i s t a n c e

and appearance

retention. Figure 6.

CF

CF

I

3

(CF ) 2

I ο I

H I Η

Celanese carpet yarns

6

C = 0 , c , ΗI I C Η I Η

CF

3

(CF )e 2

I

3

(CF )e

I

2

0

0

C = 0 C Η

I

Η I

C I

I

0

Η

Η

Figure 7. Fluorochemicals

FLUOROCHEMICAL EVENLY DISTRIBUTED OVER FIBERS PROPER ORIENTATION OF FLUORINATED GROUPS CLOSE PACKING OF FLUORINATED GROUPS Figure 8.

Surface conditions for producing effective liquid repellency

In Cellulose and Fiber Science Developments: A World View; Arthur, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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11.

WILES

Canadian Developments in Fiber Science

225

surface. T h i s i s i n d i c a t e d i n F i g u r e 9. Since f l u o r i n a t e d polymers are very e x p e n s i v e , however, they are o f t e n extended w i t h c o n v e n t i o n a l w a t e r r e p e l l e n t compounds a n d o t h e r a d j u n c t s i n finishing formulations. The p r o p e r t i e s a n d p r o b l e m s w i t h Q u a r p e l t r e a t m e n t s a r e shown i n F i g u r e 1 0 . This s i t u a t i o n i s t y p i c a l of a v a r i e t y of both commercial and e x p e r i m e n t a l f i n i s h e s . A s t u d y was u n d e r t a k e n a t t h e D e f e n c e R e s e a r c h E s t a b l i s h m e n t O t t a w a (DREO) i n o r d e r t o e s t a b l i s h a mechanism which c o u l d account f o r the l o s s o f o i l r e p e l l e n c y w h i c h o c c u r s when Q u a r p e l - t r e a t e d f a b r i c s and f a b r i c s t r e a t e d w i t h c e r t a i n f l u o r o c h e m i c a l / adjunct f i n i s h e s are s u b j e c t e d t o w e a r i n g . A second a i m o f t h e w o r k was t o d e t e r m i n e w h e t h e r r e p e l l e n t p r o p e r t i e s , o n c e l o s t , c o u l d be r e c o v e r e d by any p r a c t i c a l means. A s e r i e s o f f i n i s h e s was a p p l i e d t o c o t t o n / n y l o n f a b r i c s u s i n g c o n v e n t i o n a l pad/dry/cure t e c h n i q u e s . The f i n i s h e s i n c l u d e d Q u a r p e l a n d f l u o r o p o l y m e r s f r o m 3M, Dupont and C i b a - G e i g y c o m b i n e d w i t h p o l y (alkyl methacrylate) esters. The f l u o r o p o l y m e r s a l l possessed s t r a i g h t - c h a i n fluorinated substituents o f 8 c a r b o n atoms i n l e n g t h . The a l k y l s u b s t i t u e n t s on t h e a d j u n c t p o l y m e r m o l e c u l e s r a n g e d i n l e n g t h f r o m one t o e i g h t e e n c a r b o n a t o m s . F a b r i c s t r e a t e d w i t h t h e s e f i n i s h e s were s u b j e c t e d t o a c c e l e r a t e d w e a r u s i n g an e x p e r i m e n t a l w e a r i n g m a c h i n e d e v e l o p e d a t DREO. Of t h e many d a t a o b t a i n e d f o r d i f f e r e n t f i n i s h c o m b i n a t i o n s on f a b r i c s t e s t e d on t h e w e a r i n g m a c h i n e , F i g u r e 11 shows some t y p i c a l ones. It i s noteworthy that slower l o s s of o i l r e p e l l e n c y occurs i f the length of the a l k y l s u b s t i t u e n t s on t h e a d j u n c t i s a b o u t t h e same a s t h e l e n g t h of the f l u o r i n a t e d s u b s t i t u e n t of the f l u o r o chemical. I t i s a l s o s i g n i f i c a n t t h a t t o o much a d j u n c t c a u s e s a more r a p i d l o s s o f o i l r e p e l l e n c y on w e a r i n g . What i s e s p e c i a l l y i n t e r e s t i n g , h o w e v e r , i s t h e f a c t t h a t , a f t e r 20 h o u r s on t h e w e a r i n g m a c h i n e a n d subsequent h e a t i n g i n a f o r c e d a i r oven f o r 5 minutes a t 1 5 0 ° C , a l l f a b r i c s showed a s u b s t a n t i a l r e c o v e r y of o i l repellent properties. I n some c a s e s a r e c o v e r y very close to i n i t i a l values occurred. A p o s s i b l e explanation for a l l these observations i s as f o l l o w s . D i s o r i e n t a t i o n of s u b s t i t u e n t s at the s u r f a c e o f the f i n i s h ( d u r i n g wear) exposes n o n r e p e l l e n t a l k y l or methylene groups. This problem i s e x a c e r b a t e d when t h e a d j u n c t m o l e c u l e s u b s t i t u e n t s a r e much d i f f e r e n t i n l e n g t h (much s h o r t e r o r much

In Cellulose and Fiber Science Developments: A World View; Arthur, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

226

CELLULOSE

CF

CF

3

1

CF

CF

3

CF

3

SCIENCE

CF

3

POLYMER'BACKBONE* FIBER

Figure 9. Ideal fabric treatment

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3

A N DF I B E R

3

1

1.

CONTAIN A FLUOROCHEMICAL AND A DURABLE WATER R E P E L L E N T ADJUNCT.

2.

I N I T I A L L Y , QUARPEL TREATMENTS CONFER E X C E L L E N T WATER-AND Ο I L - R E P E L L E N C Y TO FABRICS.

3.

ON LAUNDERING AND WEARING, QUARPEL-TREATED F A B R I C S MAY R A P I D L Y LOSE O I L R E P E L L E N C Y UNDER CERTAIN CONDITIONS. Figure 10. Quarpel treatments

τ

Figure 11. Oil repellency (modified AATCC 118-1966) of worn fabrics with finishes containing as adjuncts (A) poly(methyl methacrylate), (C) poly(ethylexyl methacryhte), and (D) poly(octyl methacrylate). ( ) Flu­ orochemical/adjunct is 1/1; ( ) fluorochemical/adjunct is 1/5.

b

O

1

1

1

Δ

-Δ \

j

ι

.

Γ

Δ D' -

\

I

L

2 4 6 MACHINE WEARING TIME (hours)

In Cellulose and Fiber Science Developments: A World View; Arthur, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

11.

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227

Canadian Developments in Fiber Science

l o n g e r ) t h a n t h e f l u o r i n a t e d s u b s t i t u e n t s on t h e fluorochemical molecules. P a r t i a l (or considerable) r e c o v e r y o f r e p e l l e n t p r o p e r t i e s upon r e h e a t i n g t h e f a b r i c s i s a c c o u n t e d f o r by t h e t h e r m a l l y - i n d u c e d o r i e n t a t i o n o f f i n i s h components w i t h i n the f a b r i c s t r u c t u r e , at o r j u s t below the worn s u r f a c e .

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IV

A R a p i d Method f o r

Studying

Acoustic

Behavior

As my f o u r t h e x a m p l e , I h a v e s e l e c t e d some r e s e a r c h from the l a b o r a t o r i e s of P r o f . K e i t h S l a t e r at the U n i v e r s i t y of Guelph. He a n d h i s s t u d e n t s h a v e d e v i s e d a new s w e p t - f r e q u e n c y t e c h n i q u e f o r t h e r a p i d , inexpensive assessment of the approximate a c o u s t i c performance of a m a t e r i a l i n the l a b o r a t o r y or i n a f i e l d s i t u a t i o n . F i g u r e 12 shows a b l o c k d i a g r a m w h i c h i l l u s t r a t e s the method. The a d v a n t a g e s d e r i v e f r o m t h e u s e o f a s w e p t - f r e q u e n c y sound source ( i n s t e a d o f a f i x e d band o f n o i s e ) and a p o i n t t o p o i n t i n t e g r a t o r . By means o f t h e a c o u s t i c p r o f i l e o b t a i n e d i n t h i s w a y , one can r e a d i l y d e r i v e the measurement o f t h e sound t r a n s m i t t e d o r r e f l e c t e d by a g i v e n s t r u c t u r e . Of s p e c i a l relevance i n the t e x t i l e b u s i n e s s , i s the d e t e r m i n a t i o n of the r e d u c t i o n i n sound owing t o the i n t r o d u c t i o n of a t e x t i l e product, e . g . , a carpet. The r a p i d i t y a n d i n h e r e n t p o r t a b i l i t y o f t h e s w e p t frequency procedure allows f o r the f a c i l e a c o u s t i c " t u n i n g " o f a room, t h e a t r e , or o t h e r e n c l o s u r e . S i n c e numerous o p e r a t i o n s i n t h e t e x t i l e m a n u f a c t u r i n g areas are i n h e r e n t l y n o i s y , i t i s u s e f u l t o be a b l e t o t a k e S l a t e r ' s e q u i p m e n t i n t o v a r i o u s parts of a m i l l in order to: (a) measure t h e s e v e r i t y o f t h e n o i s e p r o b l e m s ; and (b) e v a l u a t e r a p i d l y t h e e f f i c i e n c y of various corrective procedures. Finally, t h i s p a r t i c u l a r a c o u s t i c - b e h a v i o u r method i s b e i n g e v a l u a t e d as a t e c h n i q u e f o r r a t i n g t h e c o m f o r t o f clothing. The c o m f o r t a n d / o r p r o t e c t i o n a f f o r d e d by w e a r i n g a p p a r e l i s v e r y d i f f i c u l t t o measure o b j e c t i v e l y b u t i s known t o d e p e n d i n a c o m p l e x way on a variety of f a b r i c parameters. Some o f t h e s e same parameters determine the a c o u s t i c behavior of f a b r i c s . I n i t i a l attempts to r e l a t e a c o u s t i c absorption to f a b r i c p a r a m e t e r s and t h e n c e t o c o m f o r t criteria seem p r o m i s i n g . V

Infrared Spectra of

Monofilaments

My f i n a l e x a m p l e r e f e r s t o a r e c e n t p r o j e c t from the T e x t i l e Chemistry group

research at the

In Cellulose and Fiber Science Developments: A World View; Arthur, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 5, 2015 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0050.ch011

228

CELLULOSE AND FIBER SCD3NCE

N a t i o n a l Research C o u n c i l i n Ottawa. A new method has been d e v e l o p e d f o r r e c o r d i n g the i n f r a r e d (IR) spectrum o f a s h o r t l e n g t h (< 2 cm) o f a s i n g l e monofilament . The use o f wide s l i t s e t t i n g s (on the s p e c t r o meter) f o r a sample mounted p r e c i s e l y i n the a c t i v e a r e a o f the IR beam a l l o w s the r e c o r d i n g o f the spectra of s i n g l e filaments. V i r t u a l l y any g r a t i n g IR machine can be used a l t h o u g h i t i s p r e f e r a b l e i f the a u t o m a t i c s l i t program can be o v e r r i d d e n . A very simple sample-mounting d e v i c e ( F i g u r e 13) employs s t e e l p l a t e s w i t h a c c u r a t e l y machined edges t o g r i p the f i b e r . The p l a t e s are themselves h e l d i n p o s i t i o n by a magnetic r u b b e r sheet and the f i b e r ends are t a p e d t o t h i s s h e e t . The f i b e r can be a c c u r a t e l y p o s i t i o n e d i n the IR beam by manipulating the magnetic r u b b e r sheet on the s t e e l mounting p l a t e . Two a p p l i c a t i o n s which cannot be a c h i e v e d by c o n v e n t i o n a l n o n - d e s t r u c t i v e IR s a m p l i n g t e c h n i q u e s can be used t o i l l u s t r a t e the s i n g l e f i b e r t e c h n i q u e . (I) F i g u r e 14 shows the d i f f e r e n c e i n IR a b s o r p t i o n by a p o l y p r o p y l e n e monofilament when i t i s a l i g n e d p a r a l l e l and p e r p e n d i c u l a r t o the d i r e c t i o n o f p r i o r UV i r r a d i a t i o n . Both s p e c t r a were r e c o r d e d on the same 1 cm zone o f the f i b e r . (II) F i g u r e 15 shows the v a r i a t i o n s i n o p t i c a l d e n s i t y a l o n g a 10 cm l e n g t h o f p o l y p r o p y l e n e monofilament which had been i r r a d i a t e d i n a Xe-arc Weather-Ometer f o r 200 h o u r s . The o p t i c a l d e n s i t y o f the OH and CO bands v a r i e s markedly a l o n g the p a r t i c u l a r f i l a m e n t length selected. T h i s v a r i a t i o n might r e s u l t from f l u c t u a t i o n s i n UV s e n s i t i v e i m p u r i t i e s a l o n g the fiber. While t h e r e are l i m i t a t i o n s t o the d i a m e t e r o f f i l a m e n t s t h a t may be used s i n g l y , the method has a wide p o t e n t i a l a p p l i c a b i l i t y i n t e x t i l e and f i b e r science. R e c e n t l y a r e f i n e m e n t has been d e v e l o p e d whereby the IR spectrum o f very much s m a l l e r d i a m e t e r ( e . g . ,