JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

2-05
Effect of Grafting Conditions on Radiation-induced
Graft Polymerization
Y. Ueki a) , N. C. Dafader b) , N. Seko a) and M. Tamada a)
a) Environment and Industrial Materials Research Division, QuBS, JAEA,
b) Nuclear and Radiation Chemistry Division, Institute of Nuclear Science and Technology,
Bangladesh Atomic Energy Commission
1. Introduction
Radiation-induced graft polymerization, one of the
surface modification techniques of polymer materials, has
recently been attracting attention as a refined artifice
because the adsorption rate of a grafted polymer is 10 - 100
times higher than that of a commercial granular resin.
However, the radiation-induced graft polymerization is not
very popular because this technique requires troublesome
procedure and some skill. The objective of this study is to
investigate the effect of grafting conditions, especially
oxygen, on radiation-induced graft polymerization for the
establishment of simplified grafting procedure.
2. Experimental
The nonwoven polyethylene fabric was irradiated with an
electron beam up to 100 kGy. The irradiated nonwoven
fabric was contacted with 5 wt% emulsion, which was
composed of glycidyl methacrylate, polysorbate 20 and
deionized water, in a deaerated glass ampoule at 40 °C.
The degree of grafting (Dg) was evaluated by the increased
weight after grafting.
3. Results and Discussion
Typically, to achieve higher Dg, the irradiation process
was carried out under ideal condition (oxygen-free
condition) allowing little or no deactivation of radicals that
were generated by irradiation of electron beam. In order to
protect the created radicals from deactivation caused by
oxygen in the air, the trunk polymer was packed into a
hermetically-sealed container such as a polyethylene bag,
and then the air in the sample bag was substituted with inert
gases such as nitrogen gas. Firstly, the effect of air in
sample bag on the Dg was investigated. In this experiment,
volume ratio of trunk polymer to inner volume of the
polyethylene bag was controlled within a range from 1 : 1
(polymer : bag) to 1 : 100, and the inside of sample bags was
filled with air. After grafting for 4 h, the Dg of 100 kGy
reached 501, 505, 496, 487, and 494% at polymer/bag
volume ratio of 1 : 1, 1 : 2, 1 : 5, 1: 10, 1 : 20, and 1 : 100,
respectively. These results showod that air in the sample
bag had little effect on the Dg, because irradiation time was
very short and the radical deactivation by oxygen didn't
happen very often during irradiation process.
It is also well-known that dissolved oxygen has a
significant influence on the Dg, and therefore the effect of
dissolved oxygen concentration in emulsion on the Dg was
investigated. The dissolved oxygen concentration was
JAEA-Review 2010-065
- 45 -
controlled by passing nitrogen gas in emulsion before
grafting and the Dg after grafting for 3 h relative to the
dissolved oxygen concentration is plotted as in Fig. 1. In
this experiment, the grafting reaction was tested under two
conditions; vacuum and air atmospheric condition. As
seen in Fig. 1, the Dg gradually increased with reduction of
initial dissolved oxygen concentration in emulsion as
expected and additionally the Dg of the vacuum condition
was higher than that of the air atmospheric condition.
The atmospheric effect results beam differences of oxygen
concentration in the emulsion that participated in the actual
graft polymerization. In other words, these were because,
under the vacuum condition, the enormous proportion of
dissolved oxygen in emulsion was spontaneously and
immediately released into vacuum vapor phase, and
consequently the deactivation of radicals was prevented.
Under the vacuum condition, the dissolved oxygen
concentration in emulsion was reduced from 8.3 to 1.5 mg/L
within only one minute. On the other hands, the converse
phenomena occurred under the air atmospheric condition.
Under the air atmospheric condition, when the initial
dissolved oxygen concentration became less than 1 mg/L,
the Dg of 50 kGy reached about 100% and that value was
enough to use as a metal adsorbent precursor. Based on the
above results, it was found that the graft polymerization
under air atmospheric condition could be achieved in the
following conditions; the dissolved oxygen concentration in
emulsion before grafting was 1.0 mg/L or less, and the
irradiation dose was more than 50 kGy.
Degree of grafting [%]
500
400
300
200
100
0
0 3 6 9
Dissolved oxygen concentration [mg/L]
Fig. 1 Effect of dissolved oxygen concentration in emulsion
before grafting on Dg. Polymerization condition:
○ dose of 100 kGy, grafting at vacuum atmosphere;
● dose of 100 kGy, grafting at air atmosphere;
△ dose of 50 kGy, grafting at vacuum atmosphere;
▲ dose of 50 kGy, grafting at air atmosphere;
□ dose of 20 kGy, grafting at vacuum atmosphere;
■ dose of 20 kGy, grafting at air atmosphere.