-
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-PARTIAL ACETYL4,.TJON,IN ~ITU OF CELLUtOSIC FABRIC AND ITS
RESISTANCE TO MICROBI)Hl AND ACTINIC DEGRADATION K.L.
MAHE3HWARI, U.S. GuPTA, S.S. Nm.it'd i...,u N.D'.
ffHA\.:rY&\tr'.i
Defence Research Laboratory (Stores), Kanpur: , ABSTRACT
Partial acetylation. in situ of cotton fabrics can be ,achieved
satisfactorily when it is carried out using O 03 per cent
perchloric acid as the catalyst at a temperature not exceeding 300.
Increase in concentration of perchloiic acid or 'temperature
adversely affects the tensile
- strength of the fabrics.
The acetylation of fabrics confers resistance -to leaching.
Scouring of the Ja bric prior to acetylation does not materially
influence the extent of substitutfon of hydroxyl groups by aoetyl
ones; The acetylating mixture can be repe!ttedly used but fresh
addition of the catalyst is necessary. With increase in the period
of acetylation or in the quantity of catalyst, there is a
progressive increase in acetic acid yield but the tensile strength
of the fabric shows a corresponding decrease. -
Partial acetylation affords protection against microbial attack
when the acetyl content of the acetylated fabric is 14-15 per cent.
The treatment does not however afford protection against
degradation by a_rtificial light, or sunlight or weathering.
!NTR8DUCTION
Cotton textiles a.re well known for their susceptibility to
degradation by microorga-nismsl Doree2 demonstrated that resistance
to microbial attack can be i:tnparted to cotton by altering the
chemical structure of the cellulose molecule. The presence of one
or more substituents in the anhydroglucose unit of the cellulose
chain imparts such resistance. A large number of cellulose
derivatives has been found to be resistant to fungal attack.
,3,4,5, Goldthwait et al6 showed that acetylated cotton with 300
per cent acetyl content or a degree of acetylation of l 4: per
anhydroglucose unit withstood soil burial for fifty weeks.
Investig3:tions were undertaken to study whether the acetylation
process can be used for conferring resistance to the treated fabric
against microbial, actinic as well as weathering degradation. It
was also desired to investigate the best method 'of acetylation
without tendering the fabric.
EXPERIMENTAL -A. Selection of a suiwble catalyst.-Preliminary
experiments were carried out to select
the most suitable method for acetylation of dosootie the cotton
fabric of Indian tentage-in the presence of catalysts (such as
pyridine, phosphoric acid and perchloric acid). Pro-cedures tried
for partial acetylation of the fabric wei'e as follows:-
(a) DSootie strips (10" X 2!''} weighing 80 gms were steeped in
4:N sodium hydro-xide solution (500 cc) for 1 hour. The strips were
washed free from alkali and steeped in pyridine for two days
(giving two to three changes). The strips were then transferred to
a mixture of acetic acid (4:00 c.c.) and pyridine (64:0 c.c.)
shaken for 24: hrs, dried in shade.and kept in an incubator at 370
for 4:8 hours.
233
-
284 :K . .L. MA1tESWARI, 'U.S. GUPTA, S.S. N'toAMand N. l:>.
liHANbiiii:
(b} Dosootie strips (10" X 2!") weighing 80 gms. were first
dipped in acetic acid glacial (560 c.c. ) for four hours at 37 80
and then cooled to 21 l 0 0. To this bath was added a mixture of
250 c.c. of _85% acetic anhydride and 8 5 c.c. of phosphoric acid
(cooled previously to 00). The fal>ricwas kept for 4 hours e.nd
then washed and dried in shade.
(c) Dosootie strips (10"x2!") weighing 185 gms were moistened so
as to have 30% moisture content. These were then dipped in a
solu:tion of acetic anhyd-ride (108 c.c.) in benzene (340 c.c.)'and
phosphoric acid (4;5 c.c.). The.strips were kept immersed for a
period of 17 hours at 37 20. These were then washed twice with
benzene and twice with rectified spirit and dried in shade.
(d) Dosootie strips (lO"X 2!'') weighing 80 gms were soaked in
glacial acetic acid (500 c.c.) for 4 hours and the extra acid was
removed. Strips were then dipped for 4 hrs in a mixture of acetic
anhydride (320 c.c.) benzene (480 c.c.) and traces of perchloric
acid. Acetylated strips were then remov:ed, washed and dried in
shade.
(e} Dosootie strips (IO"x 2!'') were immersed in glacial acetic
acid for 24 'hours (fabric to acid ratio being 1 : 20). After
draining off the extra acid the strips were transferred to t)le
acetylating mixture composed of one part . of acetic anhydride,
four parts of glacial acetic acid, and perchloric acid (6000%) 0 03
per cent of the total weight of the acetyJating mixture. The
mixture was main-tained at 3020 for 45 minut~. Strips were then
washed in tap water and dried in shade.
The breaking strength7 and the acetyl content8 of the above
aeetylated fabrics were determined. The results are summarised in
Table 1.
TABLE l BBEAK1NG S'rttENGTH AND ACE'rlO ACID YIELD OF VARIOUSLY
ACETYLA'rED DOSOOTtE
Treatment
As described in (a)
A.s described in (b)
-As described in (c)
A.s described in ( d)
As described in (e)
Untreated Dosootie
' ,.
Breaking. Acetic Acid Strength Yield. in lbs, Percentage
178 96
166 27
173 300
168. 090
159 169
161 Nil
-
Partiai Acetyiation in 8itu.'Oipeiluloirl,Q J!aln'ic anci its
Itesi~tanee to Miotbiai and. Actinic Degraciatioa .235
The data in Table 1 show that the desired substitution of acetyl
groups in the cellulose molecule can be best obtained by using
perchloric acid a:s catalyst by the procedure described at (e)
above:
B. Sekctioo .of the suitable quantity of percluaric acid as a
catalyst far use in partiall acetylation of the fabric---The effect
of the various quantities of the catalyst on partial acetylation of
the fabric was stud,ied by adding the catalyst in varying
proportions in the acetylating mixture (p;epared as given in para
A(e) earlier). The temperature of the mix-ture was maintained at
350 during the treatment (45 minutes). The fabrics were then washed
and dried. The resistance of tlw acetylated fabrics to soil,bnria.l
was studied. Acetyl content as well as breaking strength were also
determined. The results are given in Table 2.
TABLE 2 EFFECT OF DIFFERENT CONCENTRATIONS OF PERCHLORIC ACID ON
ACETIC ACID YIELD,
BREAKING STRENGTH OF THE TREATED FABRIC AND ITS RESISTANCE TO
SOIL BUBIAL
Perchloric Acid Initial Percentage. Acetic Breaking Percentage
(6000 per cent) Breaking Loss due to Acid Strength Loss in
Percentage on the Strength treatment Yield in lbs. Breaking
Total weight of the in lbs. in Breaking Percentage after Soil
Strength Acetylating mixture Strength Burial due to Soil
Burial Test
005 .. .. 129 32 282 . 126 25 -
! 003 .. .. 134 29 212 133 No less
001 .. .. 164 13 .03 80 .51
0005 .. .. 170 105 42 18 894
0003 .. .. 195 32 20 13 933 (Gain)
Control (untreated) . 189 Nil Ol Nil 10000
-
Acetic Acid Yield
Percentage after Soil Burial
272
186
87 18
Nil ,
Nil
The results in Table 2 show that the degree of acetylation based
on ~cetyl content increases with increase in the concentration of
the catalyst. There is however a progressive loss in breaking
strength of the fabric with increasing quantity of the
catalyst.
The resistance of the acetylated fabric to microbial
deterioration increases with the degree of acetylation. When the
concentration of the catalyst is O 03 per cent of the weight of:the
acetylating mixture or more, the fabric does not show any
appreciable loss in breaking strength under soil burial test.
0. Effect of (i) scouring prior to acetylation, (ii) temperature
during acetylation and (iii) leaching on acet'!flated
fabric-Investigations were carried out to examine the e:fiect of
(i) scouring ( ij) temperature during acetylation and ( iii)
leaching after acetylation on dosootie. The fabric was scoured by
two methods (a) boiling with l 00 per cent sodium hydroxide
solution.for 24 hours (8 hours daily for three consecutive days)
and (b) boiling with 2 00 per cent sodium hydroxide solution for
four hours only. Atletylation was investigated separately at 200
and 300 The quantity of the catalyst (perchloric acid 60 oo p~r
cent) and the period of treatment were O 03 per cent on the weight
of1 the acetylating mixture and 45 minutes respectively.in all
cases. Leachig was carried out as per det11,ils given in Appendix O
of the Indian Standards Specifi.cation9 Acetyl content was deter
mined before and after leaching. The results are summarised in
Table 3.
-
236
l TABLli! 3 EFHcT 0:t ScoURit'iG TEMP'ERATURE AND; LEACHING ON
ACETIC ACID YIELD.
Initial After Soil Burial Treatment Leached/Un-
leached Breaking Act:itic Breaking Percent- Acetic Strength Acid
Strength age Loss in Acid in Lbs. Yield in lbs, Breaking Yield
' Percent0 ge Strength Percentage
Acetylated After Scour- Leached .. Hl3 144 159 Nil 108 0 ing
with 200% NaOH Unleached 155 171 160 Nil 137 ~ Solution for 4
Hours. .. -:e Acetylated after Scour- Leached .. )57 109 84 465 713
"Cling with 100% NaOH
819 j Solution for 24 Hours; Unleached .. 157 85 98 375
t'Unscoured Fabrics Ace- Leached ... 168 153 163 Nil 97 f acetyl
group while scouring with 1 0% NaOH solution for 24 hours brings
about retardation.
It has been observed in Table 2 that when the quantity of
perchloric acid (6000%) was O 03 per cent and the temperature of
acetylating mixture was 350, there was a considerable loss in
breaking strength of the acetylated.fabric. The loss in breaking
strength is considerably reduced when acetylation is carried at -30
or 200'{Table 3). Acetyla-
. tion whether carried at 300 or 200 does not materially affect
the acetyl content or the breaking strength of the acetylated
fabric. .
D. Effect of the repeated use of the acetylating mixture with
and without the addition of fresh catalyst and inereasti in period
of treatment on the breaking strength and the acetic acid of the
acetyl,ated fabric.-,.lt was of interest to examine the possibility
of acetylation :with the used acetylating mixture. The effect of
the following factors was studied . (a) addition -0f fresh catalyst
(b) inorease in the period of treatments and (e) increase in the
quantity of the catalyst. Acetylation~ were carried out at 25-300,
The results are summarised in Table 4,
-
Partial Acetylation in situ of dellulosic Fabric and its
Resistance to Microbial ahd Actinic Degradation 23'7'
TABLE4
EFFEOT OF RIIIPEATE'1!'SE OJ' AOETYLATlNG 1\tlXTURE, INOREASE IN
PERIOD OF TltEATMENT, OONOENTRATION OF CATALYST ON THE AOETIO AOID
YIELD AND BREAKING STRENGTH OF THE
AOETYLATED FABRIOS
Acetylating Mixture
Percentage of the Period Catalyst of the Fresh Once Used Twice
used Thrice used.
treatment in Minu- %. % _% % % % % % tes Loss Acetic Loss Acetic
Loss Acetic LClsS Acetic,
in Acid in Acid in Acid in Acidl Breaking Yield, Breaking Yield
Breaking Yield Breaking YielcJ Strength S~rength Strength
Strength
--
003 .. .. 45 40 157 55 154 197 137 160 128
003 .. .. 90 100 222 117 223 327 190 330 141 003 .. .. 135 140
251 130 236 382 219 450 128 006 .. .. 45 100 203 197 20,:1 222 215
300 121 010 .. .. 45 130 282 203 236 438 223 550 144
Acetylation when: carried with once used mixture without fresh
additio:p. of the catalyst, the acetic acid yield of the acetylated
fabric was 2 35 per cent only. _
It will be observed from Table 4 that the acetyl ~ontent of the
acetyiated fabric is very low when the treatment is carried out
with once used acetylating 'mixture without the fresh addition of
the catalyst. However, with-fresh additions of the catalyst, acetyl
content increases. Acetyl content also increases with increase in
the period of acetyla-tion.
When the same acetylating mixture is used repea_tedly with the
&esh additions of catalyst, the fabric so acetylated shows
progressively increasing loss in the breaking strength with the
increase in the number of acetylations. Increase in the period of
acetylation (using the same mixture with fresh a,dditions of
catalyst) also has an adverse effect on the breaking strength of
the fabric. The acetyl content gradually goes on de- creasing with
the repeated use of tlie acetylating mixture even with fresh
additions of the catalyst.
E. Effect of ultraviolet light on acetylated Jooric-'-To examine
the effectiveness of acety-lation against actinic degradation, the
acetylated dosootie was expoaed to ultraviolet light from a mercury
arq lamp*kept ata distance of 300 ems for 48-0 hours both before
and after leaching. The results are summarised in Table 5. The
Jamp, emits a PQWerful spectrum from a 2,200A O in the ultraviolet
to 20;00{FA O in the infra red region, with light spectral lines at
2,536A0 and 4,538A0 The fabric was placed djrectly under the lamp
at a distance of 30 ems. Rise in temperature of the fabric' was
pr.evented by cooling with a continuous blast of cold air. The
temperature was maintained at 3110.
It is seen from T~ble 5 that scoured as well as unscoured
i:roetylated fabrics registered a. high loss (72-76 per cent) in
br~aking strength after exposur~ tQ mercury arc lamp while the
.untreated fabric showed only a loss of 38-43 per cent. Thus
partial acetylation apart Crom conferring protection appears to
accelerate degradation by ultraviolet light.
* This h,mp manufactured by Hanovia Ltd. Slough England.
-
TABLE 5 EFFECT OF ULTRA-VIOLET LIGHT FROM A. MERCURY ARC LAMP ON
AOETYLA.TED DOSOOTIE
-
'
Leached Unleached
Unexposed Exposed Unexposed Exposed -
Treatment B.S. Copper A.Y. Per- Cop- A.Y. B.S. Cop- A.Y. Per-
Cop- A.Y.
\ in Num- cent- pe:- in cent-per- per lbs. her age Num- lbs.
Num- age Num-
Loss her her Loss her in in
B.S. B.S. --------
--------------
Unscoured Dosootie 164 028 Nil 42 162 Nil 166 042 Nil 38 168 Nil
Not acetylated.
----------------------
Unscoured Dosootie 162 051 UIO 72 474 1020 165 058 113 72 483
108 Acetylated
----------------------
Unscoured Dosootie 155 007 Nil 43 219 Nil 153 007 Nil 40 168 Nil
Not acetylated.
--
-- -------------------
Scoured Dosootie 160 026 107 76 691 1000 163 021 108 72 738 104
Acetylated.
Legend: B.S.=Breaking Strength, A.Y.-Acetic Acid Yield
percentage. Copper Number .was Determined according to the method
of Clibbens and ~ake 10 F. Effect of weathering on partially
acetylated fabrics-For confirmation of the labora-
tory findings, randomised out door exposure trials of acetylated
do~ootie were carried out at Kanpur (Lat. 26 2B 'N, Long. 80 22' E,
altitudeA16 ft. m.s:V.} representing hot-dry climate for a period
of eight months. Wooden frames with fabrics mounted on them were
iixposed on steel racks at four feet above ground at an angle of 45
facing south in the D.R.L.(S) exposure yard. Samples were withdrawn
every two months and were tested for breaking strength, copper
number and acetyl content. The results are given in Table 6.
The results given m Table 6 show that. partial acetylation does
not confer any protection against outdoor weathering. Both treated
as well as untreated samples showed -
nearly the sa~e degree of loss in breaking strength afte11 eight
months of exposure to weathering. Acetic acid yield showed gradual
decline MTith the increase in :the period of exposure. Copper
number increased with increase in the period of exposure.
DISCUSSION
Selection of a suitable catalyst and process of acetylation-Out
of the various methods described in literature for the acetyiation
of cotton cellulose, those making use of pyridine 11 phosplioric
acid 11,12 and perchloric acid 13,14 as catalysts were primarily
selected for acetylating dosootie. The results presented in Table 1
show that the method followed by Cooper et al 14 with a little
modification in the quantity of perchloric acid (6000%) gives
satisfactory substitution (measured in terms of acetyl
content).
Effect of the quantity ofperchloric acid used as catalyst in
acetylating mixture on the acetyl content an~ breaking strength of'
the treated fabric -Cooper et al 14 have made use of O 10 per cent
perchloric acid ( 60 00 per cent) on the weight of the acetylatirig
mixture at 18C and obtained an acetyl content of 21-22 per cent.
The results presented in Table 2 indicate that higher the quantity
of catalyst, the higher is the acetyl content and loss in breaking
strength of the acetylated fabric at 35C. A concentration of 003
per cent of
l
/
-
TABLE 6 EFFECT OF WEATHERING ON ACETYLATED DOSOOTIE
Period of Weathering ,
Treatments '
Initial 2 Months I
4 Months 6 Months 8 Months'
% Copper I %Loss A.Y. %Loss Copper A.Y. B.S. Copper A.Y. Loss
A.Y. %Loss Copper Copper
Number In Number in Number in Number in Number ' B.S. B.S. B.S.
B.S.
Unscoured Dosootie 165 042 Nil 157 135 Nil 254 188 430 239 Nil
580 255 Nil (Not acetylated). Unscoured Dosootie I 163 058 ll3 153
141 ll05 184 200 399 251 226 550 287 161 Aootylated.
Scoured Dosootie 16.9 007 Nil 95 092 Nil 201 il7 390 1.89 Nil
560 278 Ni (Scouring Done with 1 % NaOH for 24 Hours.)
Scoured Dosootie 163 021 108 98 118 107 141 141 349 234 158 620
243 116 Acetylated. I
Legend=B.8.-Breaking Strength A.Y.-Acetic Acid Yield Percentage.
Ac!ltic Acid Yfold of Samples_ Drawn after 4 months was not
dete1mined..
perchloric acid on the weight of the acetylating mixture is
however found satisfactory in terms of acetyl content, breaking
strength and the resistance of the acetylated fabric to
micro~organisms in soil burial test.
.Effect of SC
- K. L. '.MAHESWARI, U. S. GUPTA, S. S. :?ll)
