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Studies in effect of -radiation on synthetic fibres-I.

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Die Angewandte Makromolekulare Chemie 6 (1969) 127-135 (Nr. 64)
From the Department of Chemical Technology, University of Bombay, Bombay-19.
Studies in Effect of y-Radiation on Synthetic Fibres-I
By S. P. POTNIS,
S . M. SHETTY,
K. N. RAO*and JAIPRAKASH**
(Eingegangen am 14. Oktober 1968)
SUMMARY:
Polyester and polyamide yarns have been exposed to y-rayswith varying dosesof
irradiation, both in vacuum and in the presence of air. The changes in such properties of the polymers as melting point, relative viscosity, tensile strength, and dye
absorption have been investigated. The results of the present study indicate that,
though with higher doses there is degradation of the polymer, under controlled
conditions certain desirable properties of the fibre are greatly improved without
affecting the mechanical strength.
ZUSAMMENFASSUNG:
Es wurde die Einwirkung von y-Strahlen auf Polyester- und Polyamid-Garn in
verschiedenen Dosen in Gegenwart sowie unter AusschluD von Luft untersucht.
Die Veriinderung in den Fasereigenschaften wie Schmelzpunkt, relative Viscositiit,
Festigkeit und Farbstoffaufnahme wwde ermittelt. Die in dieser Arbeit gefundenen
Ergebnisse zeigen, da13 - obwohl mit hoheren Strahlungsdosen die Faserstoffe beschiidigt wurden - es mit kontrollierter Bestrahlung jedoch moglich ist, einige
Fasereigenschaften ohne wesentlichen Faserabbau zu verbessern.
Introduction
The effect of y-rays on synthetic polymers has been mainly studied from the
point of view of their destructive effect particularly in the packaging industryl.
It has been already shown that this degradation is accompanied by changes of
the physical, the mechanical, the electrical, and possibly the chemical properties of the polymers and is likely to be due t o certain constitutional changes in
the polymer structure during the irradiation. It appears therefore that if the
concentration of the irradiating dose could be controlled it may be possible that
some of the physical, mechanical and electrical properties of the polymers could
*
**
Present Address : Bhabha Atomic Research Centre, Chemistry Division,
Trombay, Bombay 74.
Present Address : Cotton Technological Research Laboratories, Bombay 19.
127
S. P. POTNIS,
S. M. SHETTY,
K. N. RAOand JAIYRAKASH
be improved without deteriorating of the desired physical properties. Further
the changes occuring may be more marked if irradiation is carried out in the
presence of certain additives or monomers.
The work on irradiation of synthetic fibres is of particular interest because
many of the physical characteristics of these fibres are such that the wet processing or application of these fibres is rather difficult. Though during the past
several years a certain amount of work on the effect of nuclear radiation on the
synthetic textile fibres has been reported 293, data from the point of view of the
conditions of irradiation for obtaining maximum benificial physical properties
are not available. In addition, literature survey on the effect of y-ray irradiation
on linear polymers, such as polyesters and polyamides reveals contradictory information. Thus the polyester gets crosslinked by irradiation as reported by
CHARLSBY4 whereas the work of LITTLE5 and T O D Dshowed
~
that it leads to
degradation. The subsequent work by TEZLERand RUT HER FORD^ suggested
that the elastic modulus of oriented polyester fibres increased with radiation
dosages in the initial stages, where the draw ratio was small. But as the draw
ratio was increased a decrease in the elastic modulus was observed. HARM ON^
in 1957 studied the effect of irradiation on the tensile strength of different synthetic fibres in some detail but the changes in other properties were not indicated. A large number of papers has been published by Japanese workers7 who
have studied the grafting in the presence of y-rays and, along with other materials, have used some synthetic polymers in fibre form for grafting. The present investigation has been undertaken with specific view to study the effect of
y-ray irradiation on various synthetic fibres in controlled doses so that the surface characteristic could be altered without leading to perceptible loss in the
mechanical strength of the fibre.
For the initial study typical polyester and polyamide yarns were used, the
irradiation in Werent doses being carried out both in the presence of air and
in vacuum. The properties such as melting point, viscosity, dye absorption as
well as the mechanical properties of the fibres such as breaking load and elongation at break have been studied before and after exposure to y-rays. The
details of the origin of the materials used, irradiation exposure, test procedure
and the results obtained are described on the following pages.
Experimental
Materials
The polyester yarn used waa 100 yo Terene, continuous filament yarn supplied
by I. C. I. having denier 50, filament number 24, twist per inch 20, having 'S' twist,
drawn and dull.
128
y-Radiation on Synthetic Fibres-1
The polyamide yarn was Nylon 6, supplied by Bayer having denier 20, filament
number 3, undrawn and dull.
The Terene yarn was scoured a t 60°C for half an hour in a 0.2 yo soap solution
containing 0.5 Yosodium carbonate. The Nylon 6 yarn was extracted with methanol
in a soxhlet extractor to remove the extraneous matter sticking to the surface. The
yarns were dried in air and conditioned a t 65 yo R. H. a t 25°C.
Radiation Exposure
All irradiations were done at Bhabha Atomic Research Centre, Trombay, using
y-220 cell. The dose rate estimated by the ceric sulphate method was found to be
1.1 * 106 rads/hr/gram. It was decided to use minimum dose of 1 * 105 rads, as most
of the polymers did not show any perceptible change in properties evaluated below
1 * 105 rads as indicated in the preliminary experiments. Varying doses of 1 * 105,
5 105, 1 * 1 0 q 5 * 106, 1 * 107 and 5 * 107 rads were given depending on the chemical
structure of the polymer.
The polyester and polyamide yarns were made into hanks weighing 2 grams and
placed in corning glass test tubes with B-24 joint stoppers and were kept in y-220
cell. The vacuum irradiations were carried out at a pressure of 1 mm. of mercury.
The temperature of the y-220 cell during the irradiation was between 32" to 4OOC.
Test Procedure
Melting Point: All melting points were determined with a Gallon-kampselectrical
melting point apparatus (Catalogue No. 7646). Three readings were taken for each
sample.
Relative Viscosity: A one per cent solution of Terene in o-chlorophenolwas used
for measuring the relative viscosity. I n the case of Nylon 6 one per cent solution in
formic acid was employed. An OSTWALDviscometer number 2 was used for the
viscosity measurements.
Tensile Strength : The breaking load and percentage elongation were determined
with the aid of an Instron Tensile tester using 25 centimeter long yarn for Terene
and locentimeter long yarn for Nylon 6. Twentyfive tests were taken for each
sample and the statistic mean was calculated.
Dyeing: Dyeing was carried out with disperse dyes. The dispersing agent was
0.2 yo soap solution. The temperature of the dyeing was 82 f 2 "C. 2 yo of dye on
the weight of the yarn was taken ; the yarn to liquor ratio was 1:40. The dyeing
was carried out for a time interval of 15, 30, 45 and 60 minutes and the dye absorption was estimated from the dye bath with a Spekker's spectro photometer.
The dyes used were Duranol red 2B, 300 pf. (I. C. I.) and Dispersol fast yellow Ga.
Results
Exposure of synthetic fibres to radiation is likely to cause changes in chemical, mechanical and physical properties of the fibres. The chemical changes have
been studied by the changes of melting point as also relative viscosity in sui-
129
S. P. POTNIS,
S. M. SHETTY,
K. N. RAOand JAIPRAKASH
(gldenier)
4.5
r
Fig. 1. Tenacity of irradiated Terene
in air
-0-
lo5
lo6
id
Dose (in rads)
loB
_ _ _ _ A - - - - in vacuum
Fig. 2. Elongationof irradiatedTerene
__ 0
____A
I
0
d
106
lo7
___-
in air
in vacuum
loe
Dose (in rads)
(gldenier)
Fig. 3. Tenacity of irradiated Nylon 6
1.4
l5
L
0
in air
_ _ _ _ A - - - - in vacuum
-0-
los
lo6
lo7
Dose (inrads)
Fig. 4. Elongation of irradiated Nylon 6
--0
_ _ _ _ A----
22'
lo6
Dose (in rads)
130
lo7
in air
invacuum
Melting
Point
"C
Relative
Viscosity
in Air
Relative
Viscosity
in Vacuum
Melting
Point
"C
Terene
Irradiated
Properties of irradiated polyester and polyamide yarns.
Dose in
Rads
Table 1.
;Relative
Viscosity
Melting
Point
"C
in Air
Point
"C
Viscosity
Relative
in Vacuum
Melting
Nylon 6
Irradiated
(r
GI
3
0
2
t
8g
7-
S. P. POTNIS,
S. M. SHETTY,K. N. RAOand JAI PRAKASH
table solvents. Changes in breaking load as well as percentage elongation at
breaking have been used as the means of indicating the changes in the mechanical properties. The rate of dye absorption and also the equilibrium dye uptake
have been employed to characterise the changes in the physical structure of
the fibre.
I. Changes i n Chemical Properties
a) Melting point : Table 1 summarises the effect of radiation in air and vacuum. The results show that the melting point of the irradiated polyester fibre
is increased in early doses up to 5 106 rads, both in air and vaccum and remains fairly constant. The increase in the melting point in the presence of air is
of higher order. In the case of polyamide fibre, however, though there is an initial increase it is followed by a continuous drop at 5 106 rads both in the presence of air and in vacuum.
Compared to polyester, irradiation of polyamide in vacuum gives a higher
increase in melting point. It is interesting to observe that even after the longeat
exposure employed in the present investigation the melting points of the irradiated fibres are higher than the control samples in both the cases.
-
b) Relative Viscosity : Results indicated in table 1 show that in both
cases the relative viscosity increases slightly in early doses though there is a
subsequent considerable decrease with higher doses. It is, however, noted that
the total decrease in the viscosity under the conditions studied is less in vacuum
as compared to that in the presence of air.
II. Mechanical Properties
The changes in the mechanical properties are given in figures 1 to 4 for the
polymers irradiated in air and in vacuum. It is seen that the strength of the
fibre increases during the exposure to very mild doses up to 5 106 rads and subsequently there is a considerable fall in both air and vacuum irradiated samples.
The elongation at break, however, goes on increaaing till 1 106 rads in both the
fibres and only a t the higher doses it shows a sudden fall. The deterioration in
the mechanical properties on exposure in air or vacuum is less marked in the
case of polyester fibre as compared to polyamide.
-
-
111. Physical Properties
Changes in the dye absorption characteristics of the fibre material on exposure a t different doses in air and in vacuum are shown in fig. 5 and table 2 indicates the typical nature of the curves obtained for polyamide fibre irradiated in
132
y - Radiation on Synthetic Fibres-I
vacuum. The curves for the irradiated Nylon in air as well as the polyester fibre
both in air and in vacuum are of the similar nature. From the nature of the
curve it can be seen that the irradiation causes an increase in both the rate of
dye absorption and also the total amount of dye absorbed.
5.106 rads
-a-
0 rads
c
0
m
Fig. 5. Dye absorption of Nylon 6
irradiated in vacuum.
Time (in minutes)
Terene (using Durmol Nylon 6 (using Dura- (Using Dispersol Fast
.Yellow Ga)
no1 Red 2 B , 300 pf.)
Red 2 B , 300 pf.)
Dose in
Rads
Air
Vacuum
Air
Vacuum
Air
vacuum
0
1 . 105
5 . 105
1 . 106
5 . 106
1 . 107
5 . 107
46.17
48.74
50.79
55.24
54.71
52.42
54.37
46.17
47.30
44.48
50.64
49.58
47.65
48.81
52.06
57.02
61.77
52.72
62.07
52.06
56.96
61.30
58.69
62.12
40.86
49.20
46.47
47.37
56.20
40.86
51.71
53.94
48.08
59.93
After 60 minutes of dyeing under the conditions used, it is found that the dye
absorption remains fairly constant for a period of 45 minutes. Therefore, the
values obtained at 60 minutes could be taken as equilibrium dye absorption
under the given conditions. These values for the other experiments are given in
table 2. In general it can be said that the irradiation causes continued increase
in the dye absorption.
133
S. P. POTNIS,
S.
M.SHEITY,K. N. RAOand JAIPRAKASH
Discussion
Increase in melting point and relative viscosity under the conditions of irradiation indicates the possibility of crosslinking of the chains. The subsequent
decrease in both the characteristics shows that the degradation of the polymers
leads to chain scission. The higher resistance to degradation ofthe polyester fibre
is likely to be due to the aromatic nucleus in the polymer which would absorb a
certain amount of energy before degradation. Increase in the breaking load
observed in the initial stages appears to be due to the presence of crosslinking,
the subsequent drop may be caused by the degradation of chains as shown by
viscosity measurements. The percentage elongation is, however, observed t o
increase up to 1 106 rads suggesting that the irradiation causes loosening of the
structure.
As disperse dyes were selected in the present investigation, the amount of
dye absorption will not be affected by the changes in the functional groups in
the fibres due to irradiation. The amount of dye absorbed by the irradiated
fibre increases continuously in all cases, possibly due to the increased loosening
ofthe structure as suggested above. Regarding the ease of dyeing, p r a y irradiation hence appears t o be advantageous as both the fibres are difficult to dye with
disperse dyes under the conditions of dyeing employed.
However, the dose of irradiation is limited by the deterioration in other valuable mechanical properties of the fibres as indicated in the earlier results.
The results obtained in the present investigation thus show that, though
indiscriminate exposure of polyester and polyamide fibres to y-rays has adverse effects, irradiation of these fibres under controlled conditions leads to improvement in dyeing properties while maintaining useful mechanical properties
of the fibres.
Though in the preliminary investigation irradiation of fibres has been studied
in absence of other chemicals, it is intended to extend the scope of work to
study the effect of such irradiation in the presence of different chemicals and
monomers. It is also planned that the changes in surface structure of the irradiated polymers will be investigated by means of electron microscope and
static charge measurements.
One of the authors (S. M. SHETTY)
is thankful to the Centre of Advanced
Studies in Applied Chemistry, University of Bombay for the award of a Senior
Research scholarship.
-
1
Radiation Technology in Food,
N.W. DEsRosIER and H. M. ROSENSTOCK,
Agriculture and Biology, 1st ed., The AVI Publishing Company Inc., West Port,
Connecticut 1960, p. 311-322, 355.
134
y- Radiation on Synthetic Fibres- I
2
3
5
7
0. TEZLER
and H. A. RUTHERFORD,
Textile Res. J. 26 (1956) 796.
D.J. HARMON,
Textile Res. J. 27 (1957) 318.
A. CHARLSBY, Nature [London] 171 (1953) 167.
K. LITTLE,Nature [London] 178 (1954) 680.
A. TODD,Nature [London] 174 (1954) 613.
A. E.C. reports Tr-6316-6565 Vol. 1 to 4 (1959 to 1962) published by U.S.
Atomic Energy Commission.
135
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