Mechanisms of Degradation of Cotton and Effects of Merceri

8/12/2019 Mechanisms of Degradation of Cotton and Effects of Merceri

1/16

Die Angewandte Makromolekulare Chemie 111 1983) 69- 84 Nr.

1707)

National Research Centre, Dokki, Cairo, Egypt,

Textile Research Division, * Physics Division

Mechanisms of Degradation of Cotton and Effects

of Mercerization-Stretching upon the Course

of these Mechanisms,

VI

Structural Differences between Scoured Cotton and Slack

Mercerized-Stretched Cottons**

A. Hebeish, M. H. El-Rafie, N. Y. Abou-Zeid, M. M. Kamel, A. Waly,

A. T. El-Aref, and I. S. Fraag*

(Received 14 December 1981)

SUMMARY:

Scoured ply cotton yarn (substrate I) was slack mercerized (substrate 11) and slack

mercerized followed by stretching to 94% (substrate 111) and 103%

of

original length

(substrate IV). These substrates were given an acid pretreatment (0.5 N HC1, 6OoC,

15 min). The four substrates and their corresponding HC1-treated substrates

(substrates I-H, II-H, III-H and IV-H) were reacted under similar conditions with

N,N-diethylaziridinium chloride to yield diethylaminoethyl (DEAE)-cottons. In

addition, DEAE-cottons of substrates I, I-H, I1 and II-H were hydrolyzed with 0.5

N

HCl at 80C for 0.5, 1, 2, 3, 5 and 7 h and the ratio of substituents in the D-gluco-

pyranosyl units of these DEAE-cottons as well as in those of DEAE-hydrocelluloses

were determined. It was found that there is a considerable difference between the

reactivitiy

of

scoured cotton and slack mercerized-restretched cottons. This was inter-

preted in terms of differences in the microstructure between the substrates ik

question, which in turn, are reflected on availability, accessibility and state of order

of the cellulose hydroxyls in the scoured and mercerized cottons. Nitrogen-, chemical,

microscopical and X-ray analyses were used to assess the structural differences among

the substrates.

ZUSAMMENFASSUNG:

Gebeiztes Baumwollgarn (Substrat I) wurde spannungslos mercerisiert (Substrat 11)

und spannungslos mercerisiert, dann verstreckt um 94% (Substrat 111) und 103% der

** This research has been financed in part by a grant made by the U. S. Department

of Agriculture, Agricultural Research Service, authorized by Public Law 480.

1983 Hiithig Wepf Verlag, Basel 0003-3146/83/11 0069-16/$03.00/0 69


2/16

A. Hebeish et al.

urspriinglichen Lange (Substrat IV). Diese Substrate wurden einer Saurevorbehand-

lung unterworfen

(0,5

N HCl, 6OoC, 15 min). Die vier Substrate und ihre ent-

sprechenden HC1-behandelten Substrate (I-H, 11-H, 111-H und IV-H) wurden unter

ahnlichen Bedingungen mit N,N-Diethylaziridinchlorid umgesetzt, um D iethylamino-

ethyl (DEB)-Baumwolle zu erhalten. Zusatzlich wurden DEAE-Baumwollproben

der Sub strate I, I-H , I1 und 11-H mit

0,5 N

HCl bei 80C

0,5, 1 , 2 , 3 , 5

und

7

hydro-

lysiert und das Verhaltnis der Substituenten in den D-Glucopyranosyl-Einheiten die-

ser DEAE-Baumwollproben sowie in denen der DEAE-Hydrocellulosen wurde be-

stimm t. Es wurde gefunden, d& ein beachtlicher Unterschied zwischen der Reaktivi-

tat gebeizter und spannungslos mercerisierter nachverstreckter Baumwolle besteht.

Dies wurde im Sinne von Unterschieden in der Mikrostruktur der verschiedenen Sub-

strate interpretiert, die umgekehrt Verfugbarkeit, Zuganglichkeit und Ordnungs-

zustand der Cellulose-Hydroxylgruppenin gebeizter und mercerisierter Baumwolle

widerspiegeln. Stickstoff-, chemische, mikroskopische und Rontgenanalysen wurden

benutzt, um die strukturellen Unterschiede zwischen den Substraten festzustellen.

Introduction

Crystallinity, orientation of crystallites as well as tensile and mechanical

properties of cotton fibres can be considerably modified by subjecting the

fibres to swelling and stretching treatments with caustic soda of mercerizing

strength

5 .

Furthermore previous reports from this division6- o have

disclosed that mercerization alters the molecular structure of cotton in such a

way that mercerized cottons undergo higher degradation yet retain higher

strength than the corresponding unmercerized cottons when degraded under

identical conditions. The susceptibility to chemical degradation decreases by

increasing the tension applied for stretching the slack mercerized yarns

beyond their original length.

The reaction of N,N-diethylaziridinium chloride (DAC) with cellulose has

been served as a chemical microscope to clarify the availability of 0(2)H,

O(3)H

and

O(6)H

for the reaction. Rowland et al.

l 2

have shown that certain

hydroxyl groups (i.e. those of C-2 in cotton cellulose) are more readily

available for reactions than others (at

C-6

and C-3). This was interpreted to

be a reflection of an ordered presentation of hydroxyl groups on the surfaces

of crystalline microstructural units. In further investigations 13-23, reactions

of DAC with cotton fibre to introduce diethylaminoethyl (DEAE) sub-

stituents have been proved to be valuable

for

assessing the degree of order

which characterizes reactive crystalline surfaces of the elementary fibril.

The present work was undertaken with a view to clarify structural differ-

ences among scoured and slack mercerized-restretched cottons. To achieve

7


3/16

Degradation of Cotton

this, chemical, microscopical as well as X-ray analyses

of

scoured cotton,

slack mercerized cotton, and slack mercerized-restretched cottons were

carried out.

Experimental

Co tton Fibres

Egyptian cotton fibres, Giza 75,were combed and spun over conventional ring

spinning t o produ ce singles yarn count Ne

60

(twist factor 4). These singles yarn were

plied t o produce N e 60/2.Th e twist (twist factor

2.4)

in plying the yarns was made

opposite t o th e twist in the singles yarn. The physicomechan ical properties

of

the fibres

an d yarns were reported elsewhere6.

Scouring

Scouring

of

the ply yarn was carried out under pressure (4

5

kg/cm2) and

at

a

temp. of 120C or 2 in

a

solution containing caustic soda

6

/l), sodium carbonate

1

g/l) and a wetting agent (0.5 g/l) using a material to liquor rat io of

1 :

s described

in details in a previous publication6.

Mercerization

Skeins of the scoured yarns were slack mercerized in an aq ueous solution of caustic

soda (298 /l) at21 C nd slack mercerized followed by restretching to various lengths

viz. 94% and 103% of original length, w hile the yarn was still wet w ith the m ercerizing

solution. D etailed conditions were reported earlier

6.

For convenience, the yarn before

and afte r mercerization will be referred t o as:

Substrate I: scoured yarn,

Substrate 11: slack m ercerized yarn,

Substrate

111:

mercerization

as

nearly slack as possible on the machine (ca.

15%

shrinkage), followed by partial restretching to 94% of the original

length while the yarn was still wet with the m ercerizing solution ,

Substrate IV: mercerization as nearly slack as possible on the machine (ca. 15%

shrinkage), followed by partial restretching to

103%

of the original

length while the yarn was still wet with the mercerizing solution.

Preparation of Hydrocellulose

Heterogeneous acid hydrolyses of th e scoured yarn (substrate

I),

slack mercerized

yarn (substrate 11 an d the two slack mercerized-restretched yarns (substrates 111and

71


4/16

A. Hebeish et al.

IV were carried out in steeping the samples in 0.5 N HC1 at 60 C for 15 min, keeping a

material to liquor ratio of 1 10. After acid hydrolysis the samples were washed

repeatedly with distilled water until they were free from acid, dried in air at room temp.

and designated as I-H, 11-H, 111-H, and IV-H.

Preparation of DEAE-Cotton

Reaction of N,N-diethylaziridinium Chloride (DAC) with Substrates I-IV

and I-H V-H

The N,N-diethylaziridinium chloride was prepared by neutralizing an aqueous

solution of crystallized 2-chloroethyldiethylamine hydrochloride, separating the

2-chloroethyldiethylamine and shaking it with water as described by Roberts et al.

24.

Air dried samples (10 g) were impregnated in 0.55 M N,N-diethylaziridinium

chloride for 45 min and subsequently filtered on a sintered glass funnel

G3)

o remove

the excess solution till a wet pick up of ca. 200%. The wet sample was impregnated in

0.5

N aqueous NaOH solution, M/L ratio of 1

:

0, and the reaction was allowed to

proceed for 45 min. The detailed procedure has been described elsewherei3.

Preparation of DEAE-Hydrocellulose yarn from DEAE-Cotton (Substrates

I-V and I-H V-H)

Approximately 7 g of DEAE-Cotton skeins were treated with 0.5 N HCl solution

(using an M/L ratio of 1 10) at 80C for 0.5, 1 2, 3, 5 and 7 h. At the end of each

treatment, the insoluble fraction was removed by filtration on a sintered glass filter

and was washed with 50 ml

0.5

N HCl. The filtrate was collected and the solid was

washed on the filter with distilled water till it was acid-free. The water was discarded

and the solid fraction (DEAE-hydrocellulose) was air dried at 25 C.

Hydrolysis of DEAE-Hydrocellulose

1 g

of

each

of

the chemically modified celluloses (the DEAE-cotton

of

substrates

I-IV and I-H V-H as well as the insoluble portion derived thereof after HCl treat-

ment) was dissolved in 72% sulphuric acid and hydrolyzed during stepwise dilution of

the acid. The method is described in detail by Rowland et al. j 3 . The mixtures

of

glucose

and substituted glucoses was isolated as anhydrous freeze-dried solids or directly

subjected to fermentation to remove unsubstituted glucose23.

72


5/16

Degradation of

Cotton

Analysis f o r 2-0-, 3 0 and 6 0 DEAE)-SubstitutedD-glucopyranoses

The distribution of DEAE groups among the 2-0-, 3-0- and 6-0- positions

of

D-glucopy ranoses in each of the freeze-dried products f or each sample was determined

by gas-liquid chromatography (GLC) on

an

instrument Varian 1440 with flame

ionization detector. The column was a 1/8 in. nickel tube 10 f t long. It was packed with

3% OV-1 on Chrom osorb W (80 100 mesh). The column was operated isothermally

at 195 C. All samples to be analyzed were trimethylsilylated by the method of Sweeley

et a1.z5.

Nitrogen Content

DEAE-cellulosic materials were analyzed for nitrogen content. The latter was

monitored according to t he Kjeldahl method.

X-R ay Analysis

X-Ray diffractograms were obtained with a D-500 X-ray diffractometer (Siemens

corporation) having a measuring range (29) fro m 100 to 168 . Th e reproducibility

of 29 is 0.001 an d the diameter of the measuring circle is 401 mm . Th e detector is

a

scintillation coun ter, w ith a dead time of less than s. Th e operation of the X-ray

unit and the preparation of the pellet samples were similar t o those of Segal et a1.26.

Th e samples were ground t o 20 m esh in a Wiley mill and pressed into pellets weighing

100 mg. A pressure of 25000 psi was applied.

Th e sample was mo unted in the reflection position of the goniometer, an d a pattern

made over the range for 2 8 from 6 to 30 . Native cot ton has the reflection of the

l i

plane at 16.3 an d of the 002 plane at 22.5 . F or mercerized cotton cellulose, the l i

plane occurs a t a value for 29 of 20.5 and th e 002 plane is at 22.5 . Th e crystallinity

index (Cr

I)

for native co tton z6 s computed by measuring the intensity of diffraction

fro m the 002 plane minus the intensity at 18 . The angle tha t represents amorphous

cellulose, divided by the intensity f ro m th e 002 plane, is

I092 18- 100

C r I =

1092

Results and Discussion

Reaction

of

N,N-DiethylaziridiniumChloride With Scoured and Mercerized

Cottons

Four cotton substrates (yarns), viz., scoured (I), slack mercerized (11),

slack mercerized-restretched to 94%

(111)

and slack mercerized-restretched to

73


6/16

A. Hebeish et al.

103

(IV) were subjected to acid treatment

(0.5

N HC1

at

60C

for

15

min).

The original four substrates and their corresponding HC1-treated substrates

(substrates I-H, II-H, III-H and IV-H) were treated under similar conditions

with N,N-diethylaziridinium chloride (DAC). The eight chemically modified

celluloses were analyzed for nitrogen and the results obtained are shown in

Tab. 1

Tab. 1. Nitrogen contents resulting from the reaction of different substrates with

DAC.

Substrate N (Yo)

Scoured cotton (substrate I) 0.107

0.076

Slack mercerized cotton (substrate 11)

0.151

0.110

0.112

0.092

0.097

0.085

* Scoured cotton treated with HCl (substrate I-H)

* Slack mercerized cotton treated with HC1 (substrate II-H)

Slack mercerized cotton restretched to 94 (substrate 111)

*

Slack mercerized cotton restretched to 94

and treated with HCl (substrate III-H)

Slack mercerized cotton restretched to 103 (substrate IV)

and treated with HCl (substrate IV-H)

*

Slack mercerized cotton restretched to 103

* 0.5 N HCl at 6OoC for 15 min.

It is seen (Tab. 1) that slack mercerization of scoured cotton prior to

reaction with DAC enhances considerably the susceptibility

of

cotton to the

reaction since the nitrogen content obtained with slack mercerized cotton

(substrate 11) is higher than that of scoured cotton (substrate I). The same

holds good for slack mercerization followed by stretching to 94 of original

length, but stretching reduces the enhanced reactivity brought about by slack

mercerization. Increasing the magnitude

of

stretching to

103

produces a

substrate (substrate IV) the reactivity of which is even lower than that of

scoured cotton.

When cotton fibres are subjected to swelling treatment with caustic soda

solution of mercerizing strength, decrystallization of cotton takes place4.

Slight improvement of crystallites in cotton may occur when the fibres are

allowed to shrink freely in the swelling solutions. On the other hand, substan-

74


7/16

Degradation of

Cotton

tial improvements occur when stretch is applied to cotton fibres after slack

swelling27.Furthermore, X-ray analysis of the substrates in question showed

that although the samples (except scoured cotton) were slack mercerized

under the same conditions, the samples with the most restretching had a

higher cellulose I content 28. This suggests that the stretching has an effect on

the crystal structure. With this in mind, the availability and accessibility of

cellulose hydroxyls (sites for reaction with DAC) would be much greater in

slack mercerized cotton (substrate 11) than in scoured cotton (substrate I).

The relative accessibilities of the three different hydroxyls

of

cellulose in slack

mercerized cotton (substrate

11

would be much greater than scoured cotton

(substrate I). Stated in other words, involvement of the three hydroxyl groups

at C-2, C-3 and C16

of

the D-glucopyranosyl units of slack mercerized cotton

cellulose in hydrogen bonding is less than that of scoured cotton. The same

holds, to some extent, good for mercerized cotton restretched to 94 of

original length (substrate 111). As

a

result there is a relatively good

opportunity for the hydroxyl groups to react. That is why substrates I1and

I11

showed higher nitrogen content than substrate I .

Intreasing the magnitude of stretching is accompanied by increasing

~ r i e n t a t i o n ~ ~nd crystallinity28.Consequently, the hydroxyl groups become

relatively highly ordered, selective and difficult to react. This would account

for the lower nitrogen content observed with slack mercerized cotton re-

stretched to

103

of original length (substrate

IV).

Treatment of the four substrates in question with hydrochloric acid (0.5

N

at 60C for

15

min) prior to reaction with DAC decreases considerably the

response of these substrates to the reaction. As is evident from Tab.

1 ,

the

nitrogen content is lower with the previously acid treated samples than with

the original substrates.

A previous report6 showed that acid hydrolysis, under the conditions used,

causes degradation of scoured cotton (substrate

I)

via creation of aldehydic

groups along the cellulose chain molecules, as evidenced by the increase in

copper number, as well as chain scission, as evidenced by the fall in the degree

of polymerization. However, this degradation does not seem to affect the

removal of the accessible surfaces of the cellulose elementary fibrils nor does

it alter the susceptibility of these surfaces to iodine sorption. Mercerization of

the scoured cotton increases not only the accessible surfaces but it seems also

to create in the cellulose structure very accessible surfaces which have very

little or no resistance to the acid attack and are removed almost completely

during washing. Recrystallization is also very likely to occur during the acid

treatment. Hence the most onset of acid degradation together with recrys-

75


8/16

A. Hebeish et

al.

tallization are responsible for the decreased susceptibility of the acid treated

samples (substrates I-H V-H) to react with DAC (Tab. 1).

Four of the above chemically modified substrates, namely scoured cotton

(substrate I), HC1-treated scoured cotton (substrate I-H), slack mercerized

cotton (substrate 11) and HC1-treated slack mercerized cotton (11-H) were

hydrolyzed with HCl(O.5

N)

at 80C for varying lengths of time (0.5, 1,2,3,

5 and 7 h) and the nitrogen contents (expressed as Yo N) of the DEAE-hydro-

cellulose (insoluble fractions)

so

obtained are given in Tab.

2.

Tab. 2. Effect of duration of acid hydrolysis (0.5N HCl, 8OoC) on the nitrogen

content of DEAE-cellulose.

Substrate Acid treatment (h) Loss in

N

in DEAE-

0

0.5

1

2 3

5

7

cotton

hydrolyzed

for 5 h

Nitrogen content Olo) (VO)

I

0.107

0.101 0.108 0.105 0.102

0.099 0.089

8.08

I-H

0.076 0.074 0.074 0.063 0.073 0.073 0.073 4.10

I1 0.151 0.146 0.146

0.145

0.121

24.80

11-H 0.110

0.110

0.110 0.108

0.099 0.106 0.109 3.80

It is clear (Tab.

2)

that there is

a

decrease in the nitrogen content of DEAE-

cellulose after HC1 treatment. This is observed irrespective of the substrate

used. However, this decrease is neither striking nor significantly affected by

the duration of the acid treatment. The only exception is found with slack

mercerized cotton (substrate 11) where the decrement in nitrogen content is

quite substantial particularly after 5 h. The data of Tab. 2 further signify (a)

that with the exception of slack mercerized cotton (substrate 11) the accessible

surfaces of the elementary fibril of the modified cotton is slightly affected

(removed) under the acid conditions examined, (b) that the acid conditions

used are too mild to have a strong action on these accessible surfaces, (c) that

the accessible surface of the elementary fibrils of previously acid treated

cottons (substrates I-H and 11-H) are more resistant to acid hydrolysis than

the corresponding original samples and (d) that the elementary fibrils in slack

mercerized cotton (substrate 11) seem to acquire the most and the relatively

high accessible surfaces which are susceptible to acid attack.

76


9/16


Distribution of Substituents

n

0- 2-Diethylaminoethyl)-D-Glucose

The DEAE-cottons derived from substrates I, I-H, I1 and 11-H before and

after being subjected to hydrolysis with HC1 at 80 C for 0.5 ,1,2,3 ,5 and 7 h

were dissolved in

72

sulphuric acid and hydrolyzed during stepwise dilution

of the acid. This was followed by neutralization with barium hydroxide and

concentration of the filtrates under vacuum to yield residues. The latter were

extracted with distilled water and filtered to get rid of any traces of barium

sulphate. The filtrates containing glucose and substituted glucoses were

subjected to fermentation followed by filtration. The filtrates were freeze

dried, silylated and analyzed by gas-liquid chromatography. At the end, the

distribution of 2-(diethylamino)ethyl substituents in the 2-0- and 3-0-posi-

tions relative to the 6-0- position of the D-glucopyranosyl units of the

insoluble fraction (i. e. DEAE-hydrocelluloses) of substrates I, 11, I-H and

11-H were calculated and set out in Tab. 3.

Tab. 3 shows that with scoured cotton (substrate I) the 2-046-0- ratio

remains almost constant during the first hour of hydrolysis and then slightly

decreases. On the other hand, the 3-046-0- ratio remains practically un-

altered during the entire course of hydrolysis. The insignificant and indistin-

guishable differences between the ratios of substituents before and after

hydrolysis for different durations are rather a consequence of the relatively

mild acid conditions used. As already indicated cellulose surfaces in scoured

cotton of even low order have not been substantially removed during the for-

mation of DEAE-hydrocelluloses. Moreover, data of X-ray analyses to be

presented later substantiate this (Tab.

5).

Tab. 3 shows the ratios of substituents resulting from the reaction of slack

mercerized cotton (substrate 11) with DAC before and after hydrolysis in

0.5

N

HCl at 80C for varying lengths of time. Apparently, there is no

change in neither the 2-046-0-ratio nor in the 3-046-0-ratio with increasing

duration of hydrolysis. These ratios remain almost constant during the entire

course of hydrolysis. This suggests that the DEAE substituents in this sub-

strate are present in D-glucopyranosylunits in relatively ordered arrangement

in surfaces of cotton elementary fibrils which are resistant to acid hydrolysis

under the conditions used. This state of affairs arises perhaps during the acid

treatment via recrystallization. The fact that the cellulose I content of DEAE-

slack mercerized cotton increases by increasing the duration of acid treatment

as will be shown later (Tab. 6) supports this.

It is as well to emphasize that the 2-046-0-ratio of DEAE substituents in

the D-glucopyranosyl units of slack mercerized cotton (substrate 11) are

77


10/16

T

3

D

i

s

b

o

0

s

u

u

s

r

e

u

n

f

o

m

r

e

o

o

s

e

c

o

u

a

e

I

p

e

o

y

H

C

e

e

s

e

c

o

u

a

e

I

H

)

s

a

m

e

c

z

c

o

u

a

e

1

a

p

e

o

y

H

C

e

e

s

a

m

e

c

z

c

o

u

a

e

1

b

o

e

a

a

e

h

o

y

s

0

5

N

H

C

a

8

C

)

H

y

o

l

y

s

h

)

0

0

5

1

2 3

5

S

a

e

I

S

a

e

I

H

S

a

e

I

2

0

6

0

2

3

2

3

2

3

2

3

2

3

2

3

2

3

3

0

6

0

0

3

0

3

0

3

0

3

0

3

0

3

0

3

2

0

6

0

2

4

2

4

2

4

2

1

2

0

2

0

2

5

2

0

6

0

3

0

6

0

0

3

0

3

0

3

0

2

0

2

0

3

0

2

2

4

0

3

2

4

0

3

2

4

0

3

2

4

0

3

2

3

0

3

2

3

0

3

2

3

0

3

S

a

e

1

H

2

0

6

0

3

0

6

0

1

8

0

3

g

1

8

0

3

1

8

0

3

1

8

0

3

1

8

0

3

1

8

0

3

1

8

0

3

P

T

2

0

a

3

0

s

u

u

o

s

r

e

a

v

o

1

f

o

h

6

0

p

o

S

a

e

I

H

a

1

H

w

e

e

p

e

e

b

e

m

e

o

s

u

a

e

I

a

I

w

i

h

0

5

N

H

a

6

C

f

o

1

m

i

n

p

o

o

r

e

o

w

i

h

D

A

C


11/16

Degradation

of

Cotton

comparable with their corresponding ratios in the D-glucopyranosyl units of

scoured cotton (substrate I) before and after hydrolysis of these two sub-

strates for different times (Tab. 3). Since slack mercerized cotton is expected

to exhibit much greater susceptibility to acid hydrolysis than scoured cotton,

data of current work would suggest that slack mercerized cotton is more

amenable to recrystallization during acid treatment than scoured cotton.

Tab. 3 shows also the changes in the 2-046-0- and 3-046-0-ratios before

and during hydrolysis of previously hydrochloric acid treated scoured cotton

bearing DEAE groups (substrate I-H). Obviously, acid hydrolysis for up to

1 h has practically no effect on these ratios. Prolonging further the duration

of hydrolysis up to

7

h is accompanied by a noticeable decrement in the

2-046-0-ratio and a marginal decrement in the 3-046-0-ratio.

That no significant changes in the 2-046-0- and 3-0-/6-0-ratios occur

during the first hour of hydrolysis is an indicative of the fact that D-gluco-

pyranosyl units in relatively ordered arrangement on surfaces of highly crys-

talline regions are involved in the reaction with DAC, whereas the decrease in

these ratios upon increasing the duration

of

hydrolysis reflects the changes in

the microstructure of substrate I-H during the later stages of hydrolysis. It

seems that the accessibility of this substrate increases as a result

of

disruption

of perfect crystalline order, which in turn, is caused by

a

bending strain under

the influence of progressive acid attack as the duration increases. Indeed,

X-ray analysis has shown that this substrate (substrate I-H) exhibits lower

cellulose I content and lower crystallinity particularly in the very late stages of

hydrolysis (Tab.

7 .

Tab. 3 contains the 2-046-0- and 3-0-/6-0-ratios obtained with the reaction

product of previously hydrochloric acid treated slack mercerized cotton (sub-

strate 11-H) and

DAC

before and after hydrolysis in

0.5

N

HC1 at

8 0 C

for

different periods of time. It is evident that there is no significant change in the

2-046-0-ratio even after hydrolysis for 7 h. The same holds true for the

3-046-0- ratio. This is rather in contrast with the corresponding ratios found

with previously hydrochloric acid treated scoured cotton, a point which again

reflects the greater ability of slack mercerized cotton bearing DEAE groups

to undergo recrystallization during the course of acid hydrolysis. As it will be

shown later, X-ray analysis indicated that the cellulose I content of substrate

11-H increases after acid hydrolysis.

It may be further noted that the 2-046-0-ratio before and after hydrolysis

of previously acid treated slack mercerized cotton (substrate 11-H) is substan-

tially lower than its mate in previously acid treated scoured cotton (substrate

I-H). This again suggests that the tendency of slack mercerized cotton to

79


12/16

A.

Hebeish

et al.

undergo recrystallization during the acid pretreatment is greater than that of

scoured cotton.

X Ray Analysis

When cotton cellulose is treated with sodium hydroxide solution of

mercerizing strength, cellulose I is converted t o cellulose 11. The 1Oi plane

increases in intensity as the cellulose I is converted to cellulose 11, and the 002

plane decreases in intensity29. It has been determined that the ratio of 101

plane intensity to 002 plane intensity givesa measure of the penetration of the

swelling agent into the crystalline regions

of

the cellulose30. In other words,

the indication of the amount of conversion from cellulose I to cellulose I1 can

I (101)

be obtained by computing the ratio

(oo2) *

The changes in the microstructure of scoured cotton yarn (substrate I)

brought about by slack mercerization (substrate 11) and slack mercerization

followed by restretching to

94

and 103 of original length of the yarn

(substrate I11 and substrate IV) were assessed by X-ray analysis. The latter

was also used to determine further changes in the microstructure

of

scoured

and mercerized cotton after being reacted with DAC as well as after acid

hydrolysis of DEAE-cottons. The results obtained are given in Tab. 4 7.

The results of Tab.

4

show that, although all samples (except scoured

cotton) have been slack mercerized under the same conditions, the sample

with the most restretching (substrate IV) has a higher cellulose

I

content.

Stated in other words, the largest changes in the microstructure of these

cottons (substrates I V) observed has been the increase in cellulose I

content with increased restretching of the yarns. This suggests that the

stretching has an effect on the crystal structure of the yarns, in accordance

with the previous studiesz8. An analogue has also been proposed for

Pachyman triacetate

Tab.

4

shows ratios of peak intensities I (101)/1(002) for scoured and

mercerized cottons after treatment with DAC. It is seen that the latter treat-

ment decreases slightly the cellulose I content irrespective of the substrate

used. However, the differences in cellulose I content between scoured and

mercerized cottons still persists. That is, the samples with the most restretch-

ing have a higher cellulose I content even after DAC treatment.

Tab.

5

shows the ratio of peak intensities I (lOi)/I

(002)

for scoured and

mercerized cottons (substrates I V) treated with

0.5 N

HC1 at 60C for 15

min followed by treatment with DAC. Obviously, treatment of these sub-

80


13/16

Degradation

of

Cotton

Tab. 4. Ratio of peak intensities I(IOi)/I(002) for scoured and mercerized cotton

before and after reaction with DAC.

Substrate

I(Ioi)/1(002)

before DAC

after DAC

treatment treatment

~~ ~~

I

(scoured cotton)

0.22

0.238

I1

(slack m ercerized cotton ) 0.67 0.710

I11 (94 restretched) 0.49 0.554

IV (103

restretched)

0.41 0.452

Tab.

5.

Ratio of peak intensities

I(IOi)/I(002)

for scoured and mercerized cotton

treated with

0.5 N

HC1

at

60C for

15

min followed by treatment with

DAC.

Substrate 1(10i)/1(002)

I-H (scoured cotton) 0.238

11-H (slack m ercerized cotton) 0.663

111-H (94 restretched) 0.543

IV-H (103

restretched)

0.428

strates with HC1 under these conditions prior to treatment with DAC has

practically no effect on the cellulose

I

content.

Tab.

6

shows the crystallinity index as well as ratio of peak intensities

I (IOi)/I (002) for scoured cotton bearing DEAE groups after being subjected

to 0.5

N

HC1 at

80

C for varying lengths of time. The results indicate that the

changes in the crystallinity index of this modified cotton are within the experi-

mental errorz6during the course of hydrolysis. There is also no change in the

cellulose

I

content. The implication of this is that the conditions of the acid

hydrolyses used are too mild to have

a

significant effect on the microstructure

of scoured cotton bearing

DEAE

groups.

Tab.

6

shows also changes in peak intensities I (IOi)/I (002) and crystallin-

ity index for previously HCl treated scoured cotton bearing DEAE groups

(substrate I-H treated with DAC) with duration of hydrolysis with

0.5

N

HC1

81


14/16

A. Hebeish

et al.

Tab.

6 .

Effect

of duration

of

acid hydrolysis (0.5

N HCl at 80C) on the ratio of the

peak

intensities I(lOi)/1(002)

and crystallinity

index (Cr. I.)

of DAC treated

substrate

I

and DAC treated substrate

I-H.

Hydrolysis

Substrate I treated with DAC Substrate I-H

treated with DAC

(h)

1(10i)/1(002) Cr. I. 1(10i)/1(002) Cr.

I.

0.0 0.238 0.238

0.5 0.211 89.5 0.29 80

1

.o

0.211 88.0 0.28 81

2.0 0.189 90.0 0.30 82

3.0 0.204 89.4 0.30 80

5.0 0.227 88.8

7.0 0.195 89.8 0.25

at 80C. It is seen that the cellulose I content decreases by increasing the

duration of hydrolysis. The same holds good for the crystallinity index. This

suggests that pretreatment of scoured cotton with HCl and reacting the HCl

treated cotton with DAC brings about a modified cotton cellulose (substrate

I-H bearing DEAE groups) the crystalline elementary fibrils

of

which are

more susceptible to disruption by the acid attack than its mate derived from

scoured cotton (substrate I bearing DEAE groups). The microstructure of the

latter substrate, as pointed out above, remained apparently intact during the

course of HCl hydrolysis.

Tab. 7 shows changes in the peak intensities I(lOi)/I(002) for slack

mercerized cotton containing

DEAE

substituents before and after treatment

with

0.5 N

HC1 at 80C for varying lengths of time. The results indicate that

there is an increase, though very little, in the cellulose I content by increasing

the duration of acid hydrolysis. Increasing the cellulose I content in slack

mercerized cotton (substrate I1 treated with DAC) by prolonging the duration

of acid treatment indicates that mercerized cotton is more amenable to recrys-

tallization than scoured cotton since the latter, as shown above, does not

reveal any significant change in its microstructure after being subjected to

similar acid treatment.

Tab.

7

shows also the ratio of peak intensities I (lOC)/I (002) for previously

HC1 treated slack mercerized cotton bearing DEAE groups (substrate 11-H

treated with DAC) before and after subjecting it to

0.5 N

HCl at 80C for

different periods of time. It is apparent that there is

a

substantial increment in

82


15/16


Tab.

7.

Effect

of

duration

of

acid hydrolysis (0.5 N HCl, 80C) on the ratio of peak

intensities

1(101)/1(002)

of DAC-treated substrate I1 and DAC treated

substrate 11-H.

Hydrolysis (h) 1(1oi)/r(oo2)

Substrate I1 Substrate 11-H

treated with DAC

treated with DAC

0

0.670 0.663

0.5

0.704

0.800

1

o 0.686 0.820

2.0 0.721 0.750

3.0 0.650 0.750

5.0 0.636 0.740

7.0 0.810

the conversion ratio of cellulose I to cellulose I1 after acid hydrolysis, though

no clear cut between duration of acid hydrolysis and this increment is

observed. That is, acid treatment brings about

a

decrement in cellulose

I

content irrespective of the time of acid hydrolysis within the range studied.

A

similar observation was found with the corresponding substrate derived from

scoured cotton (substrate I-H treated with DAC) as indicated above.

It should be emphasized that the acid conditions used in this investigation

(0.5

N

HC1, 8 0 T , 0.5 7 h) are too mild to be adequate for characterizing

structural differences among scoured and slack mercerized stretched cottons.

Severe acid hydrolyses (2.5 N HC1 under reflux for different periods of time)

are now being performed. This will be published in a forthcoming paper.

The authors wish to express their sincere thank appreciation and gratitude

to

Dr.

S . P. Rowland, Research Leader, Natural Polymer Structure Research,

Natural Polymer Laboratory, SRRC, New Orleans, Louisiana,

U.S.A,

for his

invaluable guidance and critical evaluation of this work.

'

M . A. Rouselle, M. L. Nelson, C. B. Hassenboehler, Jr., D. C. Legendre, Text.

Res. J.

46

(1976) 304

N. B. Patill, N.

E.

Dweltz, T. Radhakrishnan, Text. Res. J.

35

(1965) 517

83


16/16

A. Hebeish et al.

V. S. Joshi, B. R. Shelat, T. Radhakrishnan, Text. Res. J.

37

1976) 989

B. R. Shelat, T. Radhakrishnan, B.

V.

Iyer, Text. Res. J. 30

1960) 836

L. Repenfeld, Text. Res. J. 28

(1958) 462

A. Hebeish, A. Waly, M. Tawfik, N. Y. Abou-Zeid,

S.

Shalaby, M. H . El-Rafie,

Cellul. Chem. Technol. 13 (1979) 543

A. Hebeish, M. Tawfik, M. H. El-Rafie, I. Abdel-Thalouth, A. T. El-Aref,

E. Allam, A. Waly, Cellul. Chem. Technol.

13

(1979) 717

A. Hebeish, N. Y. Abou-Zeid,

S.

E. Shalaby, A. T. El-Aref, A. Waly, I. Abdel-

Thalouth, M. Tawfik, Angew. Makromol. Chem.

99

(1981) 93

A. Hebeish, N. Y. Abou-Zeid, E. A. El-Kharadly, A. T. El-Aref, E. Allam,

S. Shalaby, E. A. El-Alfy, J. Appl. Polym. Sci. 26

(1981) 2713

lo

A. Hebeish, E. Allam, A. Bendak, N. Y. Abou-Zeid, M. Taw fik, M . H . El-Rafie,

S.

H. Abdel-Fattah, Cellul. Chem. Technol.

15

(1981) 535

l 1 S. P. Rowland, in Encyclopedia of Polymer Science an d Technology, Supplement

No. 1 , Wiley Sons, New York, London, Sydney, Toronto

1976

l 2 S. P.

Rowland,

V.

0

Cirino, A. L. Bullock, Can. J. Chem.

44 (1966) 1051

l 3

S .

P.

Rowland, E.

J.

Roberts, C.

P.

Wade, Text. Res.

J.

39

(1969) 530

l4 S . P.

Rowland, E. J. Roberts,

J. L.

Bose, C. P. Wade, J. Polym. Sci. 9

1971)

1623

l 5

S. P. Rowland, E. J. Roberts, J. L. Bose, J. Polym. Sci., Part A-1 9

1971) 1431

l 6

J.

L.

Bose, E.

J.

Roberts,

S. P.

Rowland, J. Appl. Polym. Sci. 15

(1971) 2999

l7

E. J. Roberts, J.

L.

Bose,

S.

P. Rowland, Text. Res. J. 42

(1972) 217

l 8 E. J. Roberts, S. P. Rowland, Carbohydr. Res. 4

1967) 507

l 9 E. J. Roberts, S. P. Rowland, Carbohydr. Res. 5

1967)

1

C. P. Wade, E. J. Roberts, S. P. Rowland, J. Polym. Sci., Part B 6

1968) 673

E. J. Roberts, C. P. Wade, S. P. Rowland, Carbohydr. Res. 21 (1972) 357

22 J. A. Randleman, Adv. Carbohydr. Chem.

21

(1966) 209

23

E. J. Roberts, S. P. Rowland, Can. J. Chem.

47

1969) 1571

24 E. J. Roberts, C. P. Wade, S. P. Rowland, Carbohydr. Res.

17

(1971) 393

25

C. C . Sweeley, R. B entley, M. M akita, M. W . Wells, J. Am. Chem. so c. 85

1963)

2497

26

L.

Segal, Text. Res.

J.

29

(1959) 786

27

V.

S.

Joshi, Ph. D, Dissertation, Gujarat Univ.,

1968

A. Hebeish, Annual Report on Project

FG-EG-181,

Sponsored by U. S.

Department of Agriculture, October

1978

September

1979

29

J. T. March, Ed., Mercerizing, Chapman and Hall, London 1941, p 432

30

R. H . G illespie, M . Mueller, H: Swenson,

K.

Ward, Jr., Tappi 44

(1961)

662

31

T.

L.

Bluhn, A. Sarko, Biopolymers 16

(1977) 2067

84

Documents

Mechanisms of Degradation of Cotton and Effects of Merceri