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Effect of -radiation on synthetic fibres-II irradiation in the presence of chemicals.

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Die Angewandte Makromolekulare Chemie 7 (1969) 85-100 (Nr. 7Y)
From the Department of Chemical Technology,
University of Bombay, Bombay 19
-
Effect of y-Radiation on Synthetic Fibres I1
Irradiation in the Presence of Chemicals
By S. P. POTNIS,
S. M. SHETTY
and
JAI
PRAKASH*
(Eingegangen am 20. Februar 1969)
SUMMARY :
Polyester and polyamide yarns have been irradiated under controlled doses of
y-rays in presence of chemicals like gaseous ammonia and chlorine as also methyl
methacrylate, vinyl acetate, and acrylonitrile monomers. The irradiated monomers
have been tested for some of the more important physico-chemical and mechanical
properties. The results indicate that the improvements obtained in various desirable properties are of much higher order when irradiation is carried out in presence
of the chernicals employed.
ZUSAMMENFASSUNG :
Polyester- und Polyamid-Gsrn wurden in Gegenwart von Chemikalien wie Ammoniak, Chlor, Methylmethacrylat, Vinylacetat und Acrylnitril mit kontrollierten Dosen von y-Strahlen bestrahlt. Die physikochemischen sowie mechanischen
Eigenschaften der bestrahlten Garne wurden untersucht. Die Ergebnisse zeigen, da13
durch Bestrahlung in Gegenwart dieser Chemikalien merkliche Verbesserungen einiger wiinschenswerter Fasereigenschaften moglich sind.
Introduction
Observations on the effect of high energy radiation on synthetic fibres1
indicated that though there was improvement in certain desirable properties
at low levels of doses, at higher doses degradation of the polymer chain was
predominant. Hence it was considered of interest to explore t h e possibilities
of improving the useful properties of the polymers by irradiating them in the
*
Present address : Director, Central Testing Laboratory Textiles Committee, 79,
Dr. Annie Besant Road, Bombay 18.
85
S. P. POTNIS,
8. M. SRETTYand J. PRAKASH
presence of selected chemicals. Scattered work on the irradiation of polymers
in the presence of certain chemicals has been reported by Japanese workers?.
Reaction of chromyl chloride with nylon in the presence of x-rays has been
studied by AFANAS’EV
and PAVLOV3. Grafting of polymers with various monomers by irradiation has attracted wide spread attention during the last decade.
Several papers on different methods of radiation grafting have been reported4-9.
However, from the available literature it appears that only the mechanical
properties of the grafted fibres have been studied in a few cases.
The present investigation was undertaken with a specific view to investigate
the role of y-rays in initiating the reaction of the various chemicals with the
polymer backbone and the effect of reacted chemicals on the physico-chemical
properties of the fibres. The typical polyester and polyamide yarns were
irradiated in the presence of ammonia and chlorine gas, 20% aqueous lead
acetate solution, methylmethacrylate, vinyl acetate and acrylonitrile monomers up to an integrated dosage of 5 megarads. According to published literature the introduction of chlorine and ammonia in the polymer is likely to
impart nonflammable properties10911to the same. It is also observed that the
chlorine gas plays an important part in changing the mechanical properties
as shown in the case of polyethylenelz. If by any chance, it could be possible t o
introduce the lead from lead acetate solution into the polymer matrix to a
desired extent, such fibres could possibly be employed for radiation protective
clothings. The grafting of the monomers if achieved to appreciable extent
could create additional chemical groups on the fibre and produce corresponding
changes in their various physico-chemical properties.
Experimental
Material
The polyester and polyamide yarns are the same a,s used in the previous investigationl.
Radiation Exposure
All irradiations were carried out in y-220 cell1 with co-60 source.
I r r a d i a t i o n i n t h e P r e s e n c e of A m m o n i a
Ammonia gas was generated by adding liqour ammonia on sodium hydroxide pellets. The hanks weighing 2 g were placed in a B-24 joint corning glass test tube with
vacuum adaptor. Each test tube was connected t o a two-way stopcock, whose one
end was joined to a vacuum pump and the other to the ammonia generating flask.
Initially test tube containing sample was kept under vacuum at 1 mm of mercury.
The vacuum line was cut off by the stopcock and ammonia was allowed to enter the
86
y- Radiation. of Synthetic Fibres-I?
test tube. I n this manner ammonia was flushed 3 t,o 4 times so as t o get air free ammonia in the test tube, the ratio of yarn to ammonia was 1 :15 by weight. The sample
wm irradiated after standing in contact with ammonia for 24 hrs.
I r r a d i a t i o n i n t h e P r e s e n c e o f C h l o r i n e Gas
Dried chlorine gas was filled in the test tube containing the hanks as in the case of
ammonia. The ratio of yarn to gas was 1 :15 by weight. The irradiation of the sample
was done after 24 hrs. in contact with chlorine.
I r r a d i a t i o n i n t h e P r e s e n c e of L e a d A c e t a t e S o l u t i o n
The hanks were dipped in 20 yo aqueous lead acetate solution in a corning glass
test tube. The yarn t o liquour ratio was 1 :5 by weight and the sample was allowed
to stand 24 hrs. prior to irradiation.
I r r a d i a t i o n i n t h e P r e s e n c e of d i f f e r e n t M o n o m e r s
The hanks were dipped in the monomer in a corning glass tcst tube with yarn to
liquour ratio of 1 :5 by weight. The irradiation was done after a contact period of
24 hrs. I n the case of polyester yarn, the effect of varying percentage of water in 20%
solution of monomer in ethylalcohol on the percentage of grafting was also studied.
A control sample was prepared in each case by dipping the yarn in the respective
chemicals without any irradiation.
Test Procedure
The purification of irradiated samples was done before carrying out further
tests. The samples irradiated were allowed to stand for 5 days prior to the purification. The yarns irradiated in the presence of gas were subjected to a vacuum of
10 mm of mercury for 1 hr. and conditioned t o 65 yo relative humidity at 25 "C for
2 days in normal manner.
The yarns irradiated in the presence of lead acetate were washed with distilled
water to remove the lead acetate adhering t o the outer surface of the yarn.
The yarns irradiated in the presence of monomers were washed free from homopolymer. The homopolymer of vinyl acetate and methylmethacrylate were removed
from the yarn by extracting with acetone in a soxhlet extractor, till yarns attained
constant weights. The acrylonitrile homopolymer was extracted with dimethyl
formamide. It was observed that in some cases removal of acrylonitrile homopolymer was not possible. The washed, dried and conditioned samples were weighed before and after the irradiation to find the percentage increase in weight and also
tested for melting point, relative viscosity in solution, dye absorption and tensile
strength. The details of these tests have been already given in the earlier communicationl.
The reacted chlorine and ammonia on the yarn were detected by the elemental
analysis and lead by usual qualitative analysis. I n the case of treatments with
different monomers, the extent of ,grafting on the fibre was indicated by (a) increase in weight of the fibre and (b) comparison of the I R spectra of the grafted
and original fibres.
S. P. POTNIS,
S. M. SHETTYand J. PRAKASH
Results
The changes in the physico-chemical properties of the fibres as a result of
their irradiation in the presence of various chemicals have been evaluated in a
similar manner as reported earlier1 and the results obtained for the polyester
and polyamide fibres are summarised in tables I and 11.
1. Changes in the Chemical and Physical Properties
a) P e r c e n t a g e of I n c r e a s e i n W e i g h t
Increase in weight of the yarns after irradiation in the presence of chemicals
shows the reaction of chemicals with the polymer chain. The percentage
increase in weight of polyester or polyamide irradiated in the presence of
ammonia or chlorine gas has been found to be lower than that with monomers.
Highest values have been observed in case of grafting of methylmethacrylate
onto polyamide. It was extremely difficult t o remove the homopolymer of
acrylonitrile from the polyester yarn above 0.1 megarad, and hence the
evaluation of percentage increase in weight was not possible.
b) M e l t i n g P o i n t
The melting point of the polyester yarn shows highest values when irradiated
in the presence of ammonia gas as well as in 20 yoaqueous lead acetate solution.
However, the point of interest is, that the polyester irradiated in the presence
of acrylonitrile chars instead of melting. Also the yarn turns brown in colour
about 10°C below its charing point. The polyester yarn when irradiated in
presence of different chemicals shows a higher melting point than the unirradiated
or control sample except in the presence of chlorine, where the melting point
was lower than that of the control sample.
The polyamide shows very high values of melting point when irradiated in
the presence of methylmethacrylate or acrylonitrile whereas there is hardly
any appreciable change when irradiated in the presence of vinyl acetate. A
slight increase in melting point has been observed when irradiated in the
presence of ammonia but the melting points of the polyamide irradiated in
presence of chlorine gas have been found to be lower than the unirradiated or
control sample. It is also observed that the melting points of polyester are
higher for the control samples prepared in ammonia, chlorine, methyl methacrylate and vinyl acetate as compared to unirradiated sample. Polyamide
shows a gradual increase in melting point with dose when irradiated in presence
of ammonia gas, methylmethacrylate and acrylonitrile monomers.
88
*
7
6
5
4
Homopolymer could not be removed,
unirradiated
control (in ammonia)
ammonia gas
ammonia gas
ammonia gas
ammonia gas
control (in chlorine)
chlorine gas
chlorine gas
chlorine gas
control (in lead acetate solution)
20 yo aqueous lead acetate solution
20 yo aqueous lead acetate solution
20 yo aqueous lead acetate solution
control (in methylmethacrylate)
methylmethacrylate monomer
methylmethacrylate monomer
methylmethacrylate monomer
control (in vinyl acetate)
vinyl acetate monomer
vinyl acetate monomer
vinyl acetate monomer
control (in acrylonitrile)
acrylonitrile monomer
acrylonitrile monomer
acrylonitrile monomer
1
2
3
Irradiation conditions
No.
x
x
x
x
x
x
x
1x
5
1x
1x
5
1 x
1x
5
1x
1x
5 x
1x
1x
5 x
1x
1
5
1
5
**
0
0
105
105
106
106
0
105
105
106
0
105
105
106
0
105
105
106
0
105
105
106
0
105
105
106
Dose
(rads)
1.664
1.669
1.655
1.746
1.560
1.356
1.603
1.300
1.341
1.433
1.665
1.690
1.690
1.681
1.667
1.674
1.660
1.670
1.613
1.606
1.609
1.626
1.670
1.628
-
-
46.18
48.62
51.22
60.17
68.61
71.83
50.54
67.64
70.68
71.24
47.21
48.84
52.5
56.8
50.2
55.85
55.98
56.41
48.39
51.21
64.16
71.57
50.73
60.82
Dye * *
Relative absorption
viscosity after 1 hr.
dyeing
at 30°C
(mmole/kg)
24 1
247
248
255
254
250
246
242
243
244
241
253
254
252
246
247
245
246
246
247
247
247
24 1
240
241 (chars)
260 (chars)
Melting
point
("C)
Duranol red 2 B, 300 pf.
*
*
0
0.02
0.2
0.6
0.7
0.6
1.85
2.0
2.2
0
0.14
0.2
0.35
0.4
0.55
0.9
3.9
0.8
1.3
2.5
6.9
0.2
0.3
-
(Oh)
Increase
in weight
Table 1. The results of the polyester yarn irradiated in the presence of various chemicals.
207.8
226.7
203.9
216.0
181.8
74.6
222.4
108.6
115.6
148.4
216.1
226.4
224.4
215.7
221.1
225.2
221.2
222.6
225.2
218.1
217.7
225.9
232.6
226.0
-
33.4
35.6
35.9
37.6
30.4
11.4
34.2
14.4
14.6
18.6
26.2
35.4
37.0
38.2
35.6
39.2
39.6
38.8
35.7
37.5
34.6
35.5
32.9
31.4
-
Tensile strength
*
7
6
5
4
Dispersol yellow
G3
unirradiated
control (in ammonia)
ammonia gas
ammonia gas
ammonia gas
ammonia gas
control (in chlorine)
chlorine gas
chlorine gas
chlorine gas
control (in lead acetate)
20 yo aqueous lead acetate solution
20 yo aqueous lead acetate solution
20 yo aqueous lead acetate solution
control (in methylmethacrylate)
methylmethacrylate monomer
methylmethacrylate monomer
methylmethacrylate monomer
control (vinyl acetate)
vinyl acetate monomer
vinyl acetate monomer
vinyl acetate monomer
control (acrylonitrile)
acrylonitrile monomer
acrylonitrile monomer
acrylonitrile monomer
1
2
3
Irradiation conditions
Dose
0
x
1x
5 x
1x
1x
5 x
1x
106
0
105
105
106
0
105
105
106
0
105
105
106
x 105
1x
5 x
1x
5
1
1 x 105
1x
5 x
1x
1x
5 x
1x
5 x
0
105
105
106
105
0
105
105
106
0
(rads)
("C)
213
213
215
217
217
218
212
211
209
209
213
215
217
214
213
215
284 to 286
298 to>302
213
213
212
211
213
214 (chars)
220 (chars)
230 (chars)
(%)
0.4
0.53
0.71
1.38
2.2
0.2
0.3
0.6
1.0
0.1
0.6
1.1
2.5
0.3
9.7
65.9
134.6
0.2
0.6
5.08
7.68
0.4
6.3
7.5
9.1
Melting
point
increase
in weight
2.286
2.288
2.212
2.228
2.242
2.028
1.998
1.925
1.934
1.942
2.296
2.228
2.184
2.104
2.273
1.640
1.682
1.744
2.086
1.612
1.650
1.470
2.115
1.677
1.690
1.704
40.86
42.32
50.69
52.14
46.99
36.14
42.64
49.15
52.89
56.98
40.9
42.87
59.61
62.15
41.32
44.25
53.27
60.10
50.40
56.28
58.86
62.03
43.51
58.62
64.42
65.46
32.1
35.7
26.0
24.5
30.2
25.6
28.1
20.2
22.9
23.1
33.8
20.7
21.8
19.6
34.3
29.3
22.7
24.5
33.9
27.9
28.5
9.3
32.4
29.6
20.0
16.2
26.4
27.5
16.9
15.5
24.8
17.2
17.2
12.4
13.9
14.4
35.0
14.1
14.5
13.2
28.1
30.3
17.6
29.6
36.7
19.7
18.7
7.7
36.0
24.8
21.8
92.4
Dye *
Tensile Strength
Relative absorption
I
viscosity after 1hr , Breaking
Elongation
a t 30°C
dyeing
load
(%I
(mmole/kg)
(g)
The results of the polyamide yarn irradiated in the presence of various chemicals.
No.
Table 2.
y-Radiation of Synthetic Fibres-11
c) R e l a t i v e V i s c o s i t y
The relative viscosities of polyester solutions either remain unaltered or
are higher than the unirradiated sample, when irradiated in the presence of
ammonia gas, 20 yo aqueous lead acetate solution and methylmethacrylate
monomer, whereas they are below the unirradiated or control sample when
irradiated in presence of chlorine gas and vinyl acetate monomer. However
these values go on increasing with the doses unlike in other cases.
I n case of polyamide, the relative viscosity values are more or less constant
when irradiated in the presence of ammonia gas. I n all other cases viscosities
are lower than unirradiated sample. It is interesting to note that the relative
viscosity increases with the dose in the case of polyamide irradiated in the
presence of chlorine gas, methylmethacrylate and acrylonitrile monomers.
I
0
1.10~
I
I
5.105 1,106
I
5.106
Dose (rads)
Fig. 1. Polyester yarn irradiated in the presence of various chemicals. Tenacity
(gldenier)plotted against dose (rads).
Line No. 1 - 0- in ammonia,
Line No. 2 -X- in chlorine,
Line No. 3 -.-O-.- in lead acetate solution,
Line No. 4 --- A --- in methylmethacrylate,
Line No. 5 - x - in vinyl acetate.
fi un-irradiated
91
S. P. POTNIS,
S. M. SHETTYand J. PRAKASH
d) D y e A b s o r p t i o n
All the samples were dyed with disperse dye for one hour, since the equilibrium
condition was shown to have been attained within this periodl. All conditions
of irradiation show improvement in dye uptake for both yarns. The dye
absorption is also increased with increasing dose followed by increase in weight
of the yarn, except in the case of polyamide irradiated in the presence of NH3
a t dosage of 1 x 106 or higher, where the dye absorption is less.
1.8
1.6:
1.4
-ti
1.2
.-
s
z
Q
1.0
.-3
2
0.8
S
F
0.6
0.4
0.2
I
0
0
I
I
1.105
5.105 V106
Oose (rads)
I
5.106
Fig. 2. Polyamide yarn irradiated in the presence of various chemicals. Tenacity
(gkdenier)plotted against dose (rads).
Line No. 1 - - in ammonia,
Line No. 2 -x - in chlorine,
Line No. 3
in lead acetate solution,
Line No. 4 -Ain methylmethacrylate,
Line No. 5 - x - in vinyl acetate,
Line.No. 6 -.-O---in acrylonitrile.
un-irradiated
-.-.-.-
92
y-Radiation. of Synthetic Fibres-11
2. Mechanical Properties
The breaking load of the polyester yarn has improved under all conditions
of irradiation as compared to un-irradiated sample, except in the case of
chlorine and ammonia gas. However whereas in the case of ammonia gas the
breaking load shows a fall with increasing dose in the case of chlorine it
increases with increasing dose, followed by corresponding changes in the
percentage elongation as expected. For control sample of polyester, treated
with ammonia, chlorine or acrylonitrile the breaking load is much higher than
the irradiated sample.
The breaking load of polyamide shows lower values than un-irradiated
samples under all conditions of irradiation. However, the control samples of
polyamide in ammonia lead acetate, methylmethacrylate and vinyl acetate
give higher values of breaking load as compared t o the un-irradiated sample.
A very interesting observation which needs special mention is that the poly-
-3
P
\
'\
i.,
lot
01
0
I
1.10~
I
5.10'
Dose (rads)
I
1.106
I
5.106
Fig. 3. Polyester yarn irradiated in the presence of various chemicals. Elongation
(yo)against dose (rads)
Line No. 1 -0- in ammonia,
Line No. 2 -x- in chlorine,
Line No. 3 -.-O-.-in lead acetate solution,
Line No. 4 -Ain methylmethacrylate,
Line No. 5 - x - in vinyl acetate.
93
S. P. P O ~ J IS.
S ,M. SHETTYand J. PRAKASH
amide irradiated in the presence of acrylonitrile at 1 megarad has 92 yo elongation at break comparable to that of elastomers.
The fig. 1 and 2 show the nature of the curves obtained by plotting the
tenacity (g per denier) against dose for polyester and polyamide yarns, respectively. The denier was recalculated on the basis of increase in weight of
the yarn after irradiation in the presence of appropriate chemical. It is evident
from fig. 1, that the polyester yarn is affected markedly when irradiated in
presence of ammonia and chlorine gas as compared to the’ other chemicals.
The appreciable changes resulting in the polyamide yarn by irradiation in the
presence of chemicals employed in the present work are shown in fig. 2. The
fig. 3 and 4 show the behaviour of percentage elongation with respect to dose
I
0’
0
I
I
I
5.105 1.106
Dose (rads)
1.105
5*106
Fig. 4. Polyamide yarn irradiated in the presence of various chemicals. Elongation
(yo)against dose (rads).
Line No. 1 - - in ammonia,
Line No. 2 x --- in ehlorine,
Line No. 3 -.-a in lead acetate,
Line No. 4 -Ain methylmethacrylate,
Line No. 5 - x - in vinyl acetate,
Line No. 6 -.-0
in acrylonitrile.
---’
-.-.-
94
1'- Radiation of Synthetic Fibres-II
for polyester and polyamide yarns. The nature of these curves is, more or less,
similar to that .of tenacity against dose.
It has been further noted that the polyester or polyamide yarns when
irradiated in presence of methylmethacrylate, vinyl acetate and acrylonitrile
monomers have shown some decrease in their solubilities in the solvents used
for their viscosity measurements.
With a view to increase the percentage grafting of vinyl acetate and acrylonitrile onto polyester yarn as also t o avoid the difficulty of removal of
cm-'
5000
100. I
3000
,
2000
I
I
1500
I
lOOO
1200
l
l
1
I
I
900
l
l
800
I
I
I
Wavelength(p)
Fig. 5 . Infrared Spectrum of polyester yarn.
unirradiated sample,
_ _ - irradiated in the presence of vinyl acetate.
5000 3000
I
100 '
2000
,
I
1500
I
1000 900
1200
I
I
I
I
I
l
l
800
I
I
I
Wavelength (p)
Fig. 6. Infrared Spectrum of polyamide yarn.
unirradiated sample,
_ _ _ irradiated in the presence of methylmethacrylate.
95
S. P. POTNIS,S. M. SHETTY
and J. PRAKASH
20 -
-
homopolymer from the yarn, the irradiations were done with 20 yoof monomer
solution in ethyl alcohol with varying percentage of water as suggested by
DASCUPTA
e t aP. and the results are summarised in tables 3 and 4.The dose
selected was one megarad, as highest values of grafting were obtained a t this
dose under the present experimental conditions.
As seen from the results, though the percentage grafting improves with
increasing percentage of water in the case of vinyl acetate, the overall extent
of grafting is much less than that obtained in the case of pure monomer.
Experiments with percentage of water beyond 40 yo could not be carried out
due t o the difficulty of the separation of the monomer. In the case of acrylo-
No.
96
Dose
(reds)
Water
(%)
Alcohol
(%)
Vinyl acetate
(%)
Grafting
(YO)
y-Radiation of Synthetic Fibres-I1
Table 4. Polyester yarn irradiated in the presence of acrylonitrile monomer (20 yo
in alcohol)with varying percentage of water, to study the effect of water
on the percentage of grafting.
No.
1
2
Dose
Water
Alcohol
(rads)
(%)
(YO)
x 106
1 x 106
1 x 106
1 x 106
1 x 106
1 x 106
0
10
15
1
3
4
5
6
80
70
65
60
50
40
20
30
40
Acrylonitrile
(%)
20
20
20
20
20
20
Grafting
(YO)
7.25
7.5
6.65
5.5
3.5
1.6
nitrile, the percentage of grafting decreases with increase in percentage of
water. The results indicate that this method does not have any advantage over
the treatment with pure monomer.
Discussion
Increase in weight of the yarns shows that the reaction is taking place
between the polymer backbone and the chemical used, under the influence of
y-rays. The higher increase a t higher doses is likely due to the large number of
free radicals formed under these conditions, which ultimately leads t o capture
of more monomer molecules. The possible reaction mechanism for a typical
polyester with ammonia on the basis of free radicals formed13 may be indicated
as follows :
7
f-O C - c ) - C O O C H - C H ~ O O C f OL(
\
n
403;;
97
S . P. POTNIS,
S . M. SHETTY
and J. PRAKASH
Similar reactions may be presumed with other chemicals.
The higher amount of ammonia picked up by polyamide as compared to
polyester under similar experimental conditions is likely to be due t o the lower
resistivity of polyamide to y-rays, whereby more free radicals can be formed,
as compared to the polyester having aromatic rings. The higher percentage of
reacted chlorine in the case of polyester yarns may have been due to the
presence of aromatic unsaturation which is more amenable to chlorine attack.
The extent of reaction with lead acetate solution, methylmethacrylate,
vinyl acetate and acrylonitrile monomer was less in case of polyester. This
could be again due t o its aromaticity, which might be absorbing some of the
y-ray energy and reducing the rate of grafting.
I n the case of investigations concerning the irradiation in the presence of
monomers, in addition t o the percentage increase in weight which indicates
the reaction, the infrared spectra of the original and grafted yarns a t one
megarad were also compared. For polyester yarn, to which vinyl acetate was
grafted (fig. 5), no separate peaks are seen as both the polymers have similar
chemical groups. However, the increase in the intensity of carboxylic groups
does indicate the possibility of grafting. Fig. 6 gives the I R spectra of the
original polyamide yarn, and that grafted with methylmethacrylate shows a
definite peak a t 5.75 ,U which is characteristic of the C=O group from methylmethacrylate. It shows that the monomer has not undergone any chemical
changes during the irradiation. I n a similar manner absorption peak a t 4 . 4 6 , ~
characteristic ofC=N group from the acrylonitrile is seen in the case of acrylonitrile grafted to polyamide yarn (fig. 7).
Irradiation of both the polymers in the presence of ammonia gas has resulted
in increase in their melting points. This may be either due to the stronger
hydrogen bonding of the amino groups introduced or the improved noninflammable property imparted to the polymer which are characteristic of the
compounds containing nitrogen. The higher melting points of polyester in the
case of irradiation in the presence of chlorine as compared t o un-irradiated
sample is likely to be due to the saturation of benzene rings by chlorine.
However, compared t o the control sample of polyester in chlorine, the irradiated
samples have lower melting points, which may be due t o the chain scission
initiated by chlorine in the presence of y-rays. This has been also confirmed by
fall in relative viscosity and mechanical strength. Similar phenomenon has
been also observed in the case of polyamide irradiated in the presence of
chlorine.
The melting point of polyamide has been increased considerably in the
presence of methylmethacrylate and acrylonitrile monomers, which is likely
98
y-Radiation of Synthetic Fibres-I1
t o be due t o increase in the secondary bonds of the polar groups of the
grafted monomer as well as increase in molecular weight.
The improved mechanical strengths observed a t lower doses up to 0.5 megarad
for polyester in ammonia as compared to un-irradiated sample could probably
be assigned due t o crosslinking. Subsequent loss of strength shows degradation
of the polymer in spite of the increase in percentage grafting. Both polymers
show poor strength when irradiated in the presence of chlorine, in spite of
increase in percentage chlorine and may be due t o the chain degradation
followed by addition of chlorine to the broken ends of the polymer chain. It
may be also possible that with the introduction of chlorine, weaker ionic
bonds are formed and this results in decrease in strength. In case of polyester
yarn treated with monomers, however, there is in general an improvement in
the strength of the yarn, which is likely t o be due to the formation of
stronger hydrogen bonding.
The polyamide yarn shows much lower strength when irradiated in the
presence of chemicals chosen in the present study. This is further supported by
corresponding decrease in relative viscosity. The observed trend is more likely
t o be due t o the blocking of the secondary bonds of type -NH---O=C
between the polyamide chains by the grafting of chemicals on the polymer.
The present investigation has shown that the dye uptake of both polyamide
and polyester yarns goes up considerably when irradiation is carried out in the
presence of chemicals, particularly the monomers. The extent of increase is
much more here than when the irradiations were carried out in the absence of
these chemicalsl. This may be due to the fact that from only loosening of the
structure as in the previous case, more sites for absorption are created either
by grafting or increase in the total surface area. The evidence with regard to
the increase in the total surface area as indicated from the electron micrographs
will be included in part I11 of this series.
Reaction of monomers with polyester in the presence of water and alcohol has
shown lesser percentage grafting than with pure monomer. This is likely to be
due t o the effect of solvent (ethanol) which ‘dilutes’ the monomer reducing the
rate of propagation and kinetic chain lengthl4. It is also possible that the
water can inhibit the percentage grafting by producing peroxide and hydroxy
ions due to its radiolysis. These results are contradictory to some of the
published literature where increase in percentage grafting was reported9 in the
presence of water and alcohol as compared to pure monomer. This couId be,
however, also due to the individual character of the monomer and the mutual
solubilities of these with water and ethanol because the monomer used in the
present investigation is different from the work reported in the literatureg.
99
S. P. POTNIS,
S. M. SHETTYand J. PRAKASH
It may be interesting t o note that, somewhat surprisingly, the mere dipping
of the yarns in the various chemicals has affected the physico-chemical properties significantly. I n the case of polyester, the melting point and the tensile
strength for the control sample is increased while in case of polyamide yarn
such increase is found only in case of tensile strength. Detailed study is necessary for explaining this phenomenon and as it was beyond the scope of the
present work, no attempt was made t o investigate the causes for such behaviour
a t least a t present.
The results of the present investigation show that the desirable properties
of the synthetic fibres such as melting point, dye absorption, tensile strength
and moisture regain under controlled conditions in the presence of certain
chemicals are improved.
Authors are thankful t o Dr. K. N. RAOand authorities of Chemistry Division,
Bhabha Atomic Research Centre, Trombay for providing the irradiation
facilities. Thanks are also due to the Director, Cotton Technological Research
Laboratory, Bombay 19, for permitting the use of Instron tensile tester.
S. P. POTNIS,
S. M. SHETTY,
K. N. RAOand JAIPRAKASH,
Angew. Makromolekulare Chem. 6 (1969) 127.
2 Atomic Energy Commission Reports Tr 6316 to 6565, Vol. 1 to 4 (1959-1962),
published by U. S. Atomic Energy Commission.
3 A. M. AFANAS’EV
and S. V. PAVLOV,
Izv. Vysshikh. Uehebn. Zavedenii, Khim.
i Khim. T e l h o l 9 (3) (1966) 480 (Russia); cf. C. A. 66 (1967) 294612, p. 2837.
4 W. J. BARLAUT
and D. H. GREEN,J. Polymer Sci. 28 (1958) 252.
5 0. ODIN,M. SOBEL,
A. ROSSI,R. KLEINand T. AUKER,J.Polymer Sci. A 1 (1963)
639; c. f. h e r . Chem. Soc., Div. Poly. Chem. Papers 1/2 (1960), 327.
6 A. A. ARMSTRONG
and H. A. RUTHERFORD;
N. C. S. C. Reports 2477-11, (1962),
published by U. S. Atomic Energy Commission.
7 M. R. HOUTTON
and J. K. THOMAS,
Int. J. appl. Radiat. and Isotopes, 11 1
(1961) 45.
8 R. ROLENTS
and J. K. THOMAS,
J. SOC.Dyers Colourists 76 (1960) 342.
9 S. D. GUPTA, J. T. SLOBODIAN
and D. L. ROWAT,
h e r . Dyestuff Reporter 51
7 (1962) 42.
10 Ger. Pat. 1.061.074 (1959), Dow Chemical Co., by F. DONALD
HOERUER
and
H. W. SMEAL.
11 Ger. Pat. 909.063 (1954), Gebriider LOHMANN
G. m. b. H., by E. NETJHANS
Jr.
1 2 P. J. CANTERINOand G. R. KAHLE,J. appl. Polymer Sci. 6 (1962) 20.
13 D. CHAMPBELL,K. ARUI and T. D. TURNER,
J. Polymer Sci. A 1/4 (1966) 2597.
14 A. CHAPIRO “Radiation Chemistry of Polymeric Systems” Interscience Publication, John Wiley and Sons, New York, 1961, p. 619.
100
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