Biomedical Engineering Reference
In-Depth Information
200
14
180
160
12
CMX
(Tokuyama co.)
140
10
120
8
100
80
6
60
CMX
(Tokuyama co.)
4
40
2
20
0
0
0
5
10
15
20
25
UV-irradiation time [min.]
Figure9.11
MechanicalpropertiesofBC/acrylicacidmembranescomparedtoacommercial
(CMX) membrane (24). (Preparation and characterization of acrylic acid-treated bacterial
cellulose cation-exchange membrane, Y.J. Choi, Y.H. Ahn, M.S. Kang, H.K. Jun, I.S. Kim
and S.H. Moon, Journal of Chemical Technology and Biotechnology, 2004, 79(1), 79-84,
Copyright2004, JohnWiley&SonsLtd.Reproducedwithpermission.)
cellulose membrane was impregnated with various acrylate and methacrylate monomers
and crosslinker solutions and irradiated with UV light for photopolymerization
(wavelength between 320-520 nm). A good balance of strength and flexibility was
obtained when using a 30-60 wt% acrylate/crosslinker concentration (25). By photo-
polymerizing the acrylates and methacrylates into the porous structure of never dried
BC, flexible and stable materials were obtained that retained the original BC shape
without discharging monomers. As expected, the morphology and properties of the
nanocomposites varied with the choice and content of the acrylate monomers and
crosslinker. With 60% monomers the pores of BC were completely filled; with 30%
monomers the surface of the fibers were coated as demonstrated in the SEM pictures.
The resulting composites could then be washed to remove any residual monomers to
be suitable as a biomaterial. Note that the procedure is different from that of Nogi's
group where BC sheets are dried before impregnation and cure of the acrylic resins.
In addition, in situ polymerized BC/acrylate were used as hydrogels (25) although
their water adsorption capacity appeared to decrease significantly with the in situ
polymerization of acrylics. Young modulus measured at room temperature within a
frequency range from 1 to 50 Hz revealed that with enough irradiation cycles, the
modulus of the composites can fall in the range of that of hyaline cartilage (25).
9.4
BC Nanocomposites by Polymer Impregnation and Solution Casting
Mixing of a polymer solution and a BC suspension followed by solvent casting is another
common method to prepare BC nanocomposites. Due to the synthesis and nature of
thermoplastic polymers, this approach has been more common for preparing BC/thermo-
plastic nanocomposites and has involved both natural and synthetic polymers (26-29).
Due to the lower modulus of thermoplastics compared to thermosets one might expect
Search WWH ::
Custom Search