Biomedical Engineering Reference
In-Depth Information
Figure 12.14
Schematic of the structure of a sol-gel silica-organic hybrid.
unique properties. Fine control of the degradation rate and mechanical
properties can be achieved when covalent bonds are formed between the
organic and inorganic chains (a class II hybrid, Figure 10.6).
Although the final processing temperature of the sol-gel hybrid process
is lower (40-90
◦
C) than that of the sol-gel glass process (
600
◦
C), the
foaming process can still be incorporated. However, there are complex
chemistry challenges associated with this procedure, including which
polymer to use and how to incorporate calcium.
Traditionally, calcium nitrate has been used as a precursor and dona-
tor of calcium into the inorganic network. However, temperatures of
at least 600
◦
C are needed to drive off the nitrate by-products that
are toxic to cells. The temperature must also reach 450
◦
C before cal-
cium nitrate dissociates and calcium is incorporated into the network.
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