2. Gas foaming
During the gas foaming process, molded biodegradable polymers are
pressurized at high pressures with gas-foaming agents, such as CO2 and nitrogen,
water, or fluoroform , until the polymers are saturated. This results in nucleation
and growth of gas bubbles with sizes ranging between 100 and 500 μm in the
polymer. This technique has the advantage of being an organic solvent-free process;
the major drawback is that the process may yield a structure with largely
unconnected pores and a non-porous external surface.