Volume Changes During Water Binding to Hair Fibers - American

18 Volume Changes During Water Binding to Hair Fibers M. BREUER, EDMUND M. BURAS, JR., and A. FOOKSON

Downloaded by UNIV LAVAL on October 6, 2015 | http://pubs.acs.org Publication Date: August 19, 1980 | doi: 10.1021/bk-1980-0127.ch018

Gillette Research Institute, 1413 Research Boulevard, Rockville, MD 20850

Unraveling the molecular mechanism of water binding by keratins ( e . g . , wool, h a i r , n a i l s , e t c . ) has interested chemists for h a l f a century (1). E s s e n t i a l l y , two types of models have been suggested for explaining water absorption isotherms of keratins: one that postulates the binding of water molecules on well-defined discrete s i t e s ( e . g . , polar side chains, peptide bonds) (2), and the other that maintains that swelling of the polypeptide network is the primary mechanism responsible for the absorpt i o n of water (3). The v a l i d i t y of neither of these models has been established beyond doubt, owing mainly to the lack of r e l i a b l e data on the magnitudes of the changes in the thermodynamic quantities that accompany the binding of water molecules to k e r a t i n fibers. In p a r t i c u l a r , none of the treatments have given adequate considerations to the swelling of the k e r a t i n structure and to the contribution that this process makes to the o v e r a l l free energy changes accompanying the water absorption. No doubt, this omission has been due to the lack of precise data on the volume changes occuring in hair fibers during the binding of water molecules. Recently, we have developed an o p t i c a l method capable of measuring h a i r f i b e r diameters as a funct i o n of ambient humidities with high r e p r o d u c i b i l i t y (4). Therefore, we f e e l that we are now in a p o s i t i o n to carry out a rigorous thermodynamic analysis of the water-keratin i n t e r a c t i o n process, and to examine critically the various water binding theor i e s by comparing the experimentally determined thermodynamic changes at constant volume with those predicted by the various theories. 0-8412-0559-0/ 80/47-127-309$05.00/ 0 © 1980 American Chemical Society In Water in Polymers; Rowland, S.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

310

WATER

IN

POLYMERS


The Method f o r Measuring F i b e r Diameters a t Ambient Humidities The arrangement o f a p p a r a t u s i s shown s c h e m a t i c a l l y i n F i g u r e 1. A helium-neon l a s e r ( S p e c t r a P h y s i c s , I n c . , Mountain View, C a l i f o r n i a , Model 14501) e m i t t i n g 2mW a t 632.8 nm c o n t i n u o u s l y , was mounted on an o p t i c a l bench so as to impinge upon h a i r specimens and c a s t d i f f r a c t i o n p a t t e r n s upon a s c r e e n a p p r o x i m a t e l y one meter from the specimens. The h a i r s , mounted h o r i z o n t a l l y i n an e n c l o s u r e made of a c r y l i c sheet w i t h two "windows" o f 0.15 mm t h i c k g l a s s c o v e r s l i p s f o r t r a n s m i s s i o n of the beam, i s t r a n s l a t a b l e i n two d i r e c t i o n s p e r p e n d i c u l a r t o the beam, and r o t a t a b l e w i t h i n the chamber (a f e a t u r e not used i n t h i s s t u d y ) . Air is circulated through the e n c l o s u r e a t about 120 ml/min by a p e r i s t a l t i c pump ( M a s t e r f l e x Cole-Palmer Instrument Co., C h i c a g o , I l l i n o i s ) . The r e l a t i v e h u m i d i t y (RH) o f the c i r c u l a t e d a i r i s c o n t r o l l e d by passage through D r i e r i t e (W.A. Hammond D r i e r i t e Co., Xenia, Ohio) f o r complete d r y n e s s , o r through one of the s a t u r a t e d s a l t s o l u t i o n s i n e q u i l i b r i u m with excess s o l i d t o g i v e the r e q u i r e d h u m i d i t y . Hair-atmosp h e r e e q u i l i b r i a were v e r i f i e d i n 24 t o 36 h o u r s , b e i n g i n d i c a t e d by no f u r t h e r change i n diameter o v e r an a d d i t i o n a l 5 t o 6 h o u r s , u s i n g S t u d e n t ' s " t " t e s t and r e q u i r i n g a p - n u l l o f 0.05 or l e s s . A l l a p p a r a t u s and m a t e r i a l s are m a i n t a i n e d i n a room c l o s e l y r e g u l a t e d a t 21 ± 1°C. S u c c e s s i v e measurements were made on each type o f h a i r a t i n c r e a s i n g humidities. The p a t t e r n , o r i e n t e d v e r t i c a l l y on the t a r g e t p l a n e , was s h a r p and b r i g h t so t h a t a t l e a s t 10 o r d e r s o f d i f f r a c t i o n c o u l d be seen w i t h minimal d a r k e n i n g o f the room. The s i z e of the p a t t e r n was such t h a t v i s u a l e x a m i n a t i o n p e r m i t t e d 4 t o 6 o r d e r s o f minima t o be p r i c k e d i n t o i n d e x - c a r d s t o c k h e l d a g a i n s t the t a r g e t p l a n e and c o n v e n i e n t l y measured w i t h 10 cm d i a l c a l i p e r s r e a d a b l e t o 0.001 cm. H a i r d i a m e t e r s were c a l c u l a t e d u s i n g the equation:

In Water in Polymers; Rowland, S.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

18.

BREUER E T A L .

Water Binding lo Hair

Fibers

311

0


Ό .0 ο

20

40 60 80 Relative humidity, %

Figure 1. Geometry of apparatus for precise measurements of hair diameter by optical diffraction: H, hair fiber; L, laser; B, laser beam; T, plane target with diffrac tion pattern; C, central beam

Figure 2. Increase of hair diameter as a function of relative humidity: (φ) intact hair; (A) bleached hair; Ο descaled hair


W A T E R IN P O L Y M E R S

312

d = (η λ / 4D2

2

+ 1 )/1

(1)

where d i s the h a i r d i a m e t e r , η i s the d i f f r a c t i o n o r d e r , λ i s the l a s e r l i g h t wavelength, D i s the d i s t a n c e h a i r t o t a r g e t , and 1 i s the d i s t a n c e between the η-order d i f f r a c t i o n minima on e i t h e r s i d e o f the c e n t r a l beam.


Experimental Determination of Hair F i b e r Changes a t V a r i o u s H u m i d i t i e s

Diameter

F i r s t , we checked the r e p r o d u c i b i l i t y of the method under c o n s t a n t e x p e r i m e n t a l c o n d i t i o n s ; i . e . , c a r r y i n g out the measurement a t a g i v e n , f i x e d p o i n t of the f i b e r a t c o n s t a n t h u m i d i t y and temperature. The r e p r o d u c i b i l i t y o f the method i n t h i s mode o f o p e r a t i o n proved e x t r e m e l y good, i . e . , the measure ments f e l l w i t h i n ±0,1% s t a n d a r d e r r o r ( 4 J . When we proceeded, however, t o measure the changes o f the h a i r diameter as a f u n c t i o n of r e l a t i v e h u m i d i t y , i t became o b v i o u s t h a t our f i r s t hope, i . e . , t o measure the change o f the f i b e r diam e t e r a t the same p o i n t a l o n g the f i b e r a x i s , was unrealistic. A l t e r a t i o n o f h u m i d i t y a f f e c t e d the l e n g t h o f f i b e r , making the measurements o f the d i a m e t e r a t the same p o i n t a l o n g the f i b e r a x i s a t d i f f e r e n t humidities a v i r t u a l impossibility. The problem was compounded by the f a c t t h a t h a i r f i b e r s n e i t h e r had u n i f o r m d i a m e t e r s a l o n g the f i b e r axes, nor d i d they p o s s e s s c i r c u l a r c r o s s s e c t i o n s . Since changes o f h u m i d i t y caused both a x i a l e l o n g a t i o n s and r a d i a l t w i s t s of the f i b e r s , our attempts t o determine the changes i n the f i b e r d i a m e t e r s a t the same p o i n t s were f r u s t r a t e d . Our methods e s s e n t i a l l y gauge the diameter of the f i b e r p e r p e n d i c u l a r to the d i r e c t i o n of the l i g h t beam. Consequently, i n s t e a d o f a t t e m p t i n g t o determine changes o f the f i b e r d i a m e t e r a t g i v e n p o i n t s , we d e c i d e d t o mea s u r e f i b e r s a t v a r i o u s , randomly chosen p o i n t s a l o n g t h e i r lengths. F i g u r e 2 shows the r e s u l t s o b t a i n e d w i t h d i f f e r e n t h a i r types i n terms o f t h e i r mean i n c r e a s e s i n d i a m e t e r s as a f u n c t i o n o f the r e l a t i v e h u m i d i t y (RH). I t can be seen t h a t a l l t h r e e h a i r types i n c r e a s e d i n diameter by about 8-9% as the r e l a t i v e h u m i d i t y was i n c r e a s e d from 0 t o 93%. These d a t a may be compared t o those o f M e r e d i t h who r e p o r t e d a


18.

Water Binding

BREUER E T A L .

to Hair

Fibers

313

diameter i n c r e a s e o f 16% f o r wet wool (JS). The c u r v e s , which a r e s i g m o i d i n shape, resemble those of the m o i s t u r e r e g a i n (_1 ) · Using the a v a i l a b l e d a t a from the l i t e r a t u r e on t h e a x i a l e l o n g a t i o n (_5) and our own d a t a on the r a d i a l s w e l l i n g o f h a i r as a f u n c t i o n o f water uptake, we c a l c u l a t e d V p t h e spe c i f i c volume o f the h a i r f i b e r s as a f u n c t i o n o f t h e i r water c o n t e n t s . (We assumed t h a t the r a d i a l s w e l l i n g s o f the h a i r f i b e r s a r e i s o t r o p i c ) . The v a l u e s o f V p f o r the v a r i o u s type o f h a i r f i b e r s c o u l d be e x p r e s s e d by p o l y n o m i a l s S

S


v

sp

= V

0

+ Bn + Cn2

(2)

where η i s the water c o n t e n t o f h a i r i n moles g ~ l u n i t s and the v a l u e s o f the c o e f f i c i e n t s f o r the v a r i o u s h a i r types a r e g i v e n i n T a b l e T.

TABLE I C o e f f i c i e n t s o f E q u a t i o n (2) v

0

Β

C

10.00

-85.68

Intact Hair

0.757

Descaled

Hair

0.758

3.84

932.4

Bleached

Hair

0.757

5.17

156.0

D i f f e r e n t i a t i o n o f E q u a t i o n 2 y i e l d s V , the p a r t i a l m o l a l volume o f water i n h a i r as a f u n c t i o n o f n, the water c o n t e n t o f h a i r . w

V

w

= Β + 2Cn

(3)

The v a l u e s o f V f o r the v a r i o u s h a i r types a r e p l o t t e d i n F i g u r e 3. A number o f i n t e r e s t i n g p o i n t s emerge from these daita: F i r s t , i n a l l cases the a b s o l u t e v a l u e s o f V a r e lower than the m o l a l volume o f l i q u i d water ( i . e . , 18 cm^ m o l e ~ l ) ; _ second, t h e l i m i t i n g v a l u e s ( i . e . , when η + 0) o f V f o r b l e a c h e d and d e s c a l e d h a i r a r e s m a l l e r than t h a t o f v i r g i n h a i r ; and t h i r d , whereas the V f o r i n t a c t and d e s c a l e d i n t a c t h a i r s a r e o n l y s l i g h t l y ^ dependent on n, i n the case o f b l e a c h e d h a i r V i n c r e a s e s f a s t w i t h n. w

w

w

w

w



314

WATER

Figure 3.

V, w

IN P O L Y M E R S

partial molal volume of water in hair as a function of n, the water content of hair


Water Binding

BREUER ET AL.

18.

to Hair

315

Fibers

A p l a u s i b l e e x p l a n a t i o n f o r these r e s u l t s i s t h a t i n s i d e the k e r a t i n s t r u c t u r e water i s m o l e c u l a r l y d i s p e r s e d and forms monomolecular l a y e r s around the v a r i o u s p r o t e i n s t r u c t u r a l u n i t s , i . e . , the m i c r o - o r p r o t o f i b r i l s of the k e r a t i n . The low v a l u e s o b t a i n e d for V can be e x p l a i n e d by assuming t h a t when water m o l e c u l e s p e n e t r a t e the h a i r s t r u c t u r e , they f i l l , a t l e a s t in part, pre-existing voids. The r e s u l t s a l s o s u g g e s t t h a t the c o r t e x of the h a i r s t r u c t u r e i s more porous than the c u t i c l e , s i n c e removal of the c u t i c l e J _ i . e . , d e s c a l i n g of the h a i r ) reduces the v a l u e of V . B l e a c h i n g seems to have an even l a r g e r e f f e c t - i n a d d i t i o n t o r e d u c i n g the v a l u e o f V , i t a l s o a f f e c t s s t r o n g l y i t s r a t e of change w i t h i n c r e a s i n g water uptake, p r o b a b l y by a l t e r i n g the d i s t r i b u t i o n o f the pore s i z e s i n h a i r . Whereas the pore s i z e d i s t r i b u t i o n ^ i n i n t a c t h a i r appears to be f a i r l y u n i form, i . e . , V i s o n l y weakly dependent on n, b l e a c h e d h a i r appears t o have a wider pore d i s t r i b u t i o n w i t h pore s i z e s r a p i d l y s u r p a s s i n g the magnitudes of those o f i n t a c t h a i r as n, the water uptake, reaches higher values. w


w

w

w

F r e e Energy Changes Accompanying The Water t o H a i r

Binding

of

When h a i r absorbs water, two p r o c e s s e s o c c u r simultaneously: a, water m o l e c u l e s i n t e r a c t w i t h the p o l y p e p t i d e backbones o r t h e i r s i d e c h a i n s , and b, the h a i r f i b e r s expand due t o the i n c o r p o r a t i o n of water m o l e c u l e s i n t o t h e i r s t r u c t u r e s . Thus, the t o t a l f r e e energy change can be e x p r e s s e d as: AG

T

= AG

B

+ AG

E

(4)

where AGs and AG are the f r e e e n e r g i e s of b i n d i n g and of e x p a n s i o n of the h a i r s t r u c t u r e , r e s p e c tively. S i n c e s t a t i s t i c a l m e c h a n i c a l models f o r water b i n d i n g are g e n e r a l l y d e r i v e d f o r c o n s t a n t volume c o n d i t i o n , a comparison of e x p e r i m e n t a l d a t a w i t h the c a l c u l a t e d models i s o n l y p o s s i b l e p r o v i d e d the v a l u e of A G E can be c a l c u l a t e d o r e s t i m a t e d . So f a r , t h i s has not been the case f o r the w a t e r - k e r a t i n i n t e r action. E


WATER

316

IN POLYMERS

To o b t a i n A G we undertook the f o l l o w i n g s t e p s : The v a l u e o f A G » P was o b t a i n e d by i n t e g r a t i n g the water a d s o r p t i o n i s o t h e r m from η = 0 t o η = η, thus e

AG«r = RT /

In

dn

(5)

ο

where ρ and p a r e the vapor p r e s s u r e s o f the absorbed water a t a g i v e n v a l u e o f η and o f l i q u i d water, r e s p e c t i v e l y . To o b t a i n A G we made use o f the thermodynamic r e l a t i o n s h i p : G


e

(6] N

Τ,η

T,n

where 3 denotes the i s o t h e r m i c volume compress i b i l i t y and V denotes the volume o f the f i b e r . Assuming t h a t a t a s e l e c t e d p / p the c o m p r e s s i b i l i t y i s independent o f the f i b e r compression, i . e . , 0

= constant Equation

(7)

6 can be i n t e g r a t e d t o g i v e

AG

AG

E

=

E

= /

G

(

n

=

1/3

m

)

-

G

(

n

-

dV = 1/3

Q

)

(8)

(V - Vo) (9)

where V and V denote the s p e c i f i c volumes o f the d r y h a i r f i b e r and o f a f i b e r c o n t a i n i n g η moles p e r gram o f water, r e s p e c t i v e l y . Thus, p r o v i d e d the water a b s o r p t i o n i s o t h e r m and the c o m p r e s s i b i l i t y o f k e r a t i n a r e known, the v a l u e o f A G g can be computed from E q u a t i o n 4. Q

n

Computation o f A G Q From E x p e r i m e n t a l

Data

To o b t a i n A G g , we f i r s t computed the v a l u e o f from Watt and D'Arcy's d a t a (_1) by means o f g r a p h i c a l i n t e g r a t i o n o f E q u a t i o n 5. The r e s u l t s a r e p l o t t e d i n F i g u r e 4. AGrp


Water Binding

to Hair

Fibers


BREUER ET AL.


3

318

WATER

IN P O L Y M E R S

To compute A G ^ we c a l c u l a t e d the v a l u e of 3 from the v a l u e s o f εχ, t h e a x i a l , and e2r the r a d i a l , compression moduli o b t a i n e d by B e n d i t and K e l l y (j>) , by means o f the a p p r o x i m a t i o n :

=

(10)

εχ + 2ε2

The r e s p e c t i v e v a l u e s o f the bulk modulus ( i . e . 1 / 3 ) as a f u n c t i o n o f η a r e g i v e n i n F i g u r e 5. The value of A G c o u l d then be computed by means o f E q u a t i o n 4. The r e s u l t s are g i v e n i n F i g u r e 4. Downloaded by UNIV LAVAL on October 6, 2015 | http://pubs.acs.org Publication Date: August 19, 1980 | doi: 10.1021/bk-1980-0127.ch018

b

Comparison o f Measured Values o f A G R With Those C a l c u l a t e d From V a r i o u s Models As mentioned b e f o r e , e s s e n t i a l l y two m o l e c u l a r models have been put forward f o r e x p l a i n i n g the water b i n d i n g p r o c e s s e s i n h a i r : a, water m o l e c u l e s b i n d t o d i s c r e t e , independent s i t e s a t t a c h e d t o the p o l y p e p t i d e c h a i n s o r b, water i s absorbed by a s w e l l i n g p r o c e s s o f the p o l y m e r i c network as d e s c r i b e d by F l o r y ' s polymer t h e o r i e s (_8 ). F o r the s i t e b i n d i n g model the f r e e energy change i s g i v e n by S t e i n h a r d t ( 2 ) :

a n/m

f A G

B

(ID

= nRT < In Κ + In ll

whereas f o r the p o l y m e r - s w e l l i n g

A G

B

- n/m,

process

= RT(n In ν + n ' l n ν' + Xnv')

(12)

where η = water bound t o h a i r , mole g ~ l m = water b i n d i n g s i t e s h a i r , mole g ~ l a = p/p

0

= water

activity

Κ = b i n d i n g c o n s t a n t o f water t o a b i n d i n g site ν = volume f r a c t i o n o f water i n h a i r v'=

1 - v, volume f r a c t i o n o f p e p t i d e in hair

residues


BREUER ET A L .

Water Binding

to Hair

Fibers


18.

Figure 5.

Bulk modulus as a function of relative humidity


319

WATER IN POLYMERS


320

Figure 6. Comparison of experimental A G / n , integral free energy changes per mole of water absorbed in hair, with theoretical values: (φ) from Equation 12; (Ώ) 1 n Equation 11;(0) experimental B

ror


BREUER ET AL.

18.

Water Binding

X = Flory-Huggins n'=

to Hair

321

Fibers

i n t e r a c t i o n parameter

p e p t i d e r e s i d u e s i n h a i r , mole g " l

To compare the e x p e r i m e n t a l r e s u l t s w i t h the t h e o r e t i c a l models, we p o s t u l a t e d i n e q u a t i o n (11) t h a t a t a = 1 and a l l the a v a i l a b l e b i n d i n g s i t e s a r e o c c u p i e d , i . e . m = 2.00 χ 10~*2 mole g""*, and t h a t the t h e o r e t i c a l and e x p e r i m e n t a l A G v a l u e s are e q u a l when n/m = 0.5, i . e . , when a = 0.75. In t h i s way the c a l c u l a t e d and the e x p e r i m e n t a l l y measured AG V S η curves i n t e r s e c t at t h i s p o i n t . In c a l c u l a t i n g A G by e q u a t i o n ( 1 2 ) , we assumed that n = 8.92 χ 1 0 ~ mole g " and X = 1.00 (3). The i n t e g r a l f r e e energy changes, c a l c u l a t e d on the b a s i s of e q u a t i o n s (11) and (12) t o g e t h e r w i t h the e x p e r i m e n t a l v a l u e s , per mole o f bound water, a r e g i v e n i n F i g u r e 6. b


B

b

1

D i s c u s s i o n and

2

1

Conclusions

The r e s u l t s of t h i s i n v e s t i g a t i o n suggest t h a t n e g l e c t i n g the f r e e energy changes o c c u r i n g conse quent t o the e x p a n s i o n o f h a i r f i b e r d u r i n g water a b s o r p t i o n i n t r o d u c e s a c o n s i d e r a b l e e r r o r i n the assessment of the t o t a l f r e e energy change o f water binding. Rosenbaum's c o n c l u s i o n s (3), t h a t the F l o r y ' s polymer s w e l l i n g t h e o r y accounts b e t t e r f o r the water b i n d i n g d a t a than does a model based on the assumption t h a t water b i n d s t o d i s c r e t e s i t e s , does not seem t o be borne out when the thermodynamic w o r k - r e q u i r e d f o r expanding the h a i r f i b e r i s a l s o taken i n account. The v e r y low v a l u e s of the p a r t i a l m o l a l volume of water i n h a i r , which we found, a l s o suggest t h a t the mechanism i s e s s e n t i a l l y d i f f e r e n t from the one t h a t was p o s t u l a t e d by F l o r y f o r the s w e l l i n g of p o l y m e r i c g e l s ( ) · Wheras the apparent agreement o b t a i n e d between the e x p e r i m e n t a l l y measured i n t e g r a l f r e e energy changes and those c a l c u l a t e d on the b a s i s o f E q u a t i o n 11 i s most i n t e r e s t i n g , i t s h o u l d not be taken as a p r o o f f o r the v a l i d i t y of the S i t e B i n d i n g Model. The need f o r t h i s c a u t i o n a r y s t a t e ment becomes e v i d e n t a f t e r a c l o s e r e x a m i n a t i o n o f the d a t a p r e s e n t e d i n F i g u r e 4. The curve A G VS. η has a minimum s u g g e s t i n g t h a t the d i f f e r e n t i a l b i n d i n g f r e e energy, i . e . (9AG /3n) becomes p o s i t i v e a t v a l u e s η > 0.008 mole g"-^; E q u a t i o n 11 cannot p r e d i c t t h i s type o f b e h a v i o r . We f e e l t h a t the mecha nism which e x p l a i n s B

B


WATER IN POLYMERS


322

the volume change d a t a most s a t i s f a c t o r i l y i s t h e following: d r y h a i r i s a f a i r l y r i g i d semic r y s t a l l i n e porous s o l i d . Water p e n e t r a t e s i n t o t h e p o r e s between v a r i o u s f i b r i l s o f t h e h a i r s t r u c t u r e and p r i e s them a p a r t , thus b r i n g i n g about a g r a d u a l i n c r e a s e o f t h e h a i r volume. The thermodynamic d r i v i n g f o r c e f o r t h e water a b s o r p t i o n i s a combin a t i o n of three processes: i n t e r a c t i o n with d i s c r e t e p o l a r s i d e c h a i n s ( a c i d i c and b a s i c groups) and pep t i d e bonds, c a p i l l a r y c o n d e n s a t i o n , and e n t r o p i e g a i n s owing t o t h e m i x i n g o f water w i t h t h e p o l y p e p t i d e c h a i n s , w i t h t h e s i t e b i n d i n g b e i n g the domi nant p r o c e s s . It i s i n t e r e s t i n g that descaling of hair brings about an i n c r e a s e i n t h e v a l u e o f V^. This r e s u l t s u g g e s t s t h a t t h e c u t i c l e i s p r o b a b l y l e s s porous than t h e c o r t e x and t h a t the v a l u e o f the p a r t i a l m o l a l volume o f water i n the c u t i c l e i s near t o t h e m o l a l volume o f l i q u i d water. F i n a l l y i t seems t h a t c h e m i c a l treatment o f h a i r ( i . e . , b l e a c h i n g ) changes t h e pore s i z e d i s t r i b u t i o n of h a i r , b r i n g i n g about a wider d i s t r i b u t i o n o f pore sizes.

Literature

Cited

1.

Watt, I.C.; D'Arcy, R.L. Polymer Sci. Symposium 1976, 55, 155.

2.

Watt, I.C.; Leeder, J.D. J. Text. Inst. 1968, 59, 353. Rosenbaum, S., J. Polymer Sci.: Part C 1970, 31, 45. Buras, E.; Fookson, Α.; Breuer, M.M. Proceedings the First International Congress on Human Hair, Hamburg, 1979, in press. Meredith, R., In "Fiber Science", Preston, J.M., Ed.; The Textile Institute: Manchester, 1958. Bendit, E.G.; Kelly, M. Textile Res. J. 1978, 48, 674. Steinhardt, J.; Reynolds, J.A. "Multiple Equilibria in Proteins"; Academic Press: New York, 1969. Flory, P. "Principles of Polymer Chemistry"; Cornell University Press: Ithaca, N.Y., 1953.

3. 4. 5. 6. 7. 8.

RECEIVED January 4, 1980.


Volume Changes During Water Binding to Hair Fibers - American

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