12 Recent Developments in Grafting of Monomers to
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Wool Keratin Using U V and γ-Radiation JOHN L. GARNETT The University of New South Wales, Kensington, NSW, Australia 2033 JOHN D. LEEDER C.S.I.R.O. Division of Textile Industry, Belmont, Victoria, Australia 3216 The application of synthetic polymers to wool is potentially of great importance for modifying a large number of end-use properties of the fibre (1-6). For graft copolymerization of vinyl monomers, radiation-induced techniques utilizing ionizing radiation and, more recently, UV have attracted considerable research attention because of their potential to reduce effluent problems and lower costs of chemicals and energy. Ionizing radiation copolymerization has been studied by a number of workers (1, 6-10). However, radiation doses to achieve satisfactory grafting have generally been relatively high, thus reducing the possibility of a practical treatment. Recently the radiation-induced grafting of acrylonitrile to wool in the presence of vinyl sulfonyl dyes was reported (11). Photochemical initiation for copolymerization to wool has also been studied, both in the vapour phase (12) and in solution, essentially by the mutual irradiation method (10,13,14). In the ionizing radiation procedure it is advantageous to increase the degree of conversion of monomer to (grafted) polymer, and to reduce significantly the irradiation time, the total dose received by the trunk polymer, and the formation of homopolymer, if the mutual irradiation pro cedure (the most versatile method) is to be commercially viable. In addition it is important to consider grafting systems where the organic solvent has been replaced by an aqueous medium. It is the purpose of this paper to discuss recent advances in this field, with particular regard to practical development of UV and ionizing radiation processes for grafting vinyl monomers to wool. Experimental Grafting Procedures The ionizing and photochemical-radiation equipment and pro cedures used for the wool work were essentially similar to those described at this Conference for grafting to cellulose (15). The wool used was either a light-weight (150 gm m~) plain weave fabric made from 21μ diameter Merino wool fibres, or loose wool (in "top" form) from the same source. Small squares of fibre 2
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Arthur; Textile and Paper Chemistry and Technology ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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TEXTILE
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PAPER
CHEMISTRY
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TECHNOLOGY
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bundles o f 0.4-0.5 g were weighed a f t e r e q u i l i b r a t i o n at 23 C, 65% RH f o r at l e a s t 24 hours. For the emulsion experiments, emulsions o f e t h y l a e r y l a t e were prepared by v i g o r o u s l y shaking monomer, water and e m u l s i f y i n g agent u n t i l a s t a b l e emulsion was formed. For a 50% emulsion, t h i s r e q u i r e d about 30 seconds shaking. For lower concentrations o f monomer, i t was p r e f e r a b l e to d i l u t e the 50% emulsion. For the UV work, two sources were used, namely a P h i l i p s 90W high-pressure lamp (15) and a 6-inch (200W/inch) Hanovia h i g h pressure lamp. For the padding technique wool samples were squeezed with an equal weight o f l i q u o r i n a device designed t o simulate a pad mangle. A f t e r a l l treatments, samples were washed i n hot methanol to remove unreacted monomer, then e x h a u s t i v e l y e x t r a c t e d to remove homopolymer Q). A c i d Catalyzed G r a f t i n g Recent work has shown that mineral acids are capable o f c a t a l y z i n g g r a f t i n g o f monomers to wool (16). Further data on a c i d c a t a l y s i s are presented here as a prelude to r e s u l t s f o r radiation grafting. These r e s u l t s a c t u a l l y represent c o n t r o l experiments f o r the a c i d enhancement o f r a d i a t i o n g r a f t i n g to be discussed i n one o f the f o l l o w i n g s e c t i o n s . The r a t e o f a c i d - c a t a l y z e d copolymerization i n wool (Table 1) i s very much f a s t e r and more uniform than i n other common polymers TABLE 1.
G r a f t i n g o f Styrene to Wool i n A c i d i f i e d S o l u t i o n at 43°C α 50% Styrene
Time (hours)
% Graft
1.0 2.0 3.0 5.0 7.0 14.0 32.5 72 a
0.2N methanolic HN0 to wool r a t i o used.
4 8 12 26 46 44 58 68 3
Methanol
75% Styrene % Graft 6 12 20 35 45 242 4850
-
s o l u t i o n i n a i r and " i n f i n i t e "
liquor
such as c e l l u l o s e and the p o l y o l e f i n s (16,17). In Table 1, t y p i c a l r e s u l t s are shown f o r the g r a f t i n g o f styrene to wool i n the presence o f d i l u t e n i t r i c a c i d and a t y p i c a l s w e l l i n g solvent such as methanol. The g r a f t i n g r a t e i s i n c r e a s e d remarkably by i n c r e a s i n g the monomer c o n c e n t r a t i o n (1,16,17) or the temperature QiLiiZ)· No i n d u c t i o n p e r i o d i s observed but g r a f t i n g becomes
Arthur; Textile and Paper Chemistry and Technology ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on May 11, 2016 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0049.ch012
12.
GARNETT
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Radiation
LEEDER
Grafting
of Monomers
to Wool
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extremely r a p i d a f t e r a c e r t a i n l e v e l o f copolymerization has been a t t a i n e d . A i r exerts n e g l i g i b l e e f f e c t on the r e a c t i o n . The p h y s i c a l form o f the wool a f f e c t s the g r a f t i n g r a t e ; loose wool f i b r e s and wool powder g r a f t more r a p i d l y than wool f a b r i c . Very h i g h l y g r a f t e d f i b r e s i n c r e a s e t h e i r p h y s i c a l dimensions s e v e r a l times, and e v e n t u a l l y b u r s t at around 5000% g r a f t . Extremely slow g r a f t i n g i s observed over long p e r i o d s i n the absence o f a c i d . Homopolymer formation, as evidenced by an i n crease i n v i s c o s i t y , i s only s i g n i f i c a n t at 80% styrene concen trations; at lower monomer c o n c e n t r a t i o n s , even at 2500% g r a f t , the v i s c o s i t y o f the supernatant l i q u i d does not change s i g n i f i c a n t l y (17). Changing the a c i d used f o r c a t a l y s i s has a profound e f f e c t on the g r a f t i n g r e a c t i o n , n i t r i c a c i d being the most a c t i v e , followed by s u l f u r i c a c i d (Table I I ) . A maximum i n g r a f t i s reached at the highest styrene c o n c e n t r a t i o n . Increase i n temperature has a dramatic e f f e c t on the g r a f t i n g , as shown by the behaviour with s u l f u r i c a c i d at 50°C (Table I I ) . TABLE I I .
E f f e c t o f A c i d S t r u c t u r e i n Catalyzed G r a f t i n g o f Styrene to Wool a
%
% Styrene H2SO4
20 40 60 80 90
HC1
7 \Φ 8 57^ 15 150& 26 900& 32e 2210&
6 6 7 ηο 1
G
r
a
f
t
i
HNO3
28 121 1750 2630 3050
n
A
c
i
d
HC10i>
7 8 12 20^ 19
