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

Modification of Hydroxypropyl Cellulose Hydrogels
by Blending Poly(vinyl alcohol)
A. Hiroki a) , T. Sato b) , N. Nagasawa a) and M. Tamada a)
a) Environmental and Industrial Materials Research Division, QuBS, JAEA,
b) NIPPON CONTACT LENS INC
Hydrogels of polysaccharide derivatives such as
carboxymethyl starch and hydroxypropyl cellulose (HPC)
are prepared by gamma or electron beam irradiation with
1, 2)
their high concentrated aqueous solution . We have
promoted the use of the obtained biodegradable hydrogels in
various fields such as medicine and agriculture. However,
their application range is limited because the hydrogels are
hard to expand and are splintery generally. Polymer
blending is most widely used technique to modify the
original properties of polymer. Poly(vinyl alcohol) (PVA)
exhibits not only excellent physical properties but also
biodegradability, which has been applied in a tough wound
dressing. In this work, the modification of mechanical
properties of HPC hydrogels by blending PVA was
investigated.
HPC, which is the grade of 1000-4000 cP, was purchased
from Wako Pure Chemical Industries, Ltd., Japan.
PVA-117 was supplied by Kuraray Co. Ltd, Japan.
HPC/PVA aqueous solutions as a paste state were prepared
to 20 wt% of HPC, and the PVA content was adjusted in the
range of 0.4 to 4.0 wt%. The HPC/PVA blend samples
with 0.5 mm thickness formed by cold pressing were
irradiated with electron beam to obtain gel membranes.
The irradiations were carried out using Cockcroft Walton
electron accelerator at the Takasaki Advanced Radiation
Research Institute, JAEA. Gel fraction of the obtained gel
membranes was determined gravimetrically by measuring
insoluble part after water extraction of sol. The swelling of
the blend hydrogels was calculated from weight ratio
between the swollen and dried hydrogels. The tensile
strength and the elongation at break were measured by
expanding HPC/PVA hydrogels cut into strip specimen.
Figure 1 shows the gel fraction of HPC/PVA blend
Gel fraction (%)
2-04
100
80
60
40
20
PVA (%)
0
0.4
1.0
2.0
4.0
0
0 20 40
Dose (kGy)
60 80
Fig. 1 The gel fraction of HPC/PVA blend hydrogels
as a function of dose.
JAEA-Review 2010-065
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hydrogels as a function of dose. The gel fraction of the
blend hydrogels increased sharply up to 10 kGy and reached
a constant value at 50 kGy. Increase in the PVA content
especially decreased the gel fraction in the dose range up to
50 kGy. Meanwhile, the swelling of the HPC/PVA blend
hydrogels decreased with increasing the dose, but increased
slightly when the PVA content increased. This is due to the
inhibition of the crosslinking reaction occurred by radical
quenching of PVA.
The effect of the PVA content on the elongation at break
of the HPC/PVA blend hydrogels obtained at 50 kGy is
shown in Fig. 2. The elongation at break of the blend
hydrogel showed a minimum (45%) at 0.4 wt% of PVA
content, and then, it gradually increased with increasing the
PVA content beyond 0.4 wt%. Consequently, the
elongation at break of the blend hydrogel with 4 wt% PVA
reached 125%, which exhibited about 1.8 times larger than
that of the pure HPC hydrogel. This would be due to the
formation of network structure crosslinked between HPC
and PVA.
From the above mentioned results, it was found that the
HPC hydrogels with desired mechanical properties were
obtained by the combination of PVA blending with the
radiation crosslinking technique. Therefore, the HPC/PVA
blend hydrogels could be used as a material to touch directly
by hand.
References
1) F. Yoshii et al., Nucl. Instrum Meth. B 208 (2003)
320-324.
2) R. A. Wach et al., Macromol. Mater. Eng. 287 (2002)
285-295.
Elongation at break (%)
140
120
100
80
60
40
20
0
0 1 2
PVA content (%)
3 4
Fig. 2 The Effect of the PVA content on the elongation
at break of the HPC/PVA blend hydrogels obtained
at 50 kGy.