The Journal of Supercritical Fluids | VOL. 54
Foaming strategies for bioabsorbable polymers in supercritical fluid mixtures. Part II. Foaming of poly(ɛ-caprolactone-co-lactide) in carbon dioxide and carbon dioxide+acetone fluid mixtures and formation of tubular foams via solution extrusion
Publication Date Sep 1, 2010
Abstract This paper reports on the foaming of poly(ɛ-caprolactone-co-lactide) in carbon dioxide and carbon dioxide + acetone mixtures. Experiments were carried out in specially designed molds with porous metal surfaces and fluid circulation features to generate foams with uniform dimensions at 60, 70 and 80 °C at pressures in the range 7–28 MPa. Depending upon the conditions, foams with pores in the range from 5 to 200 μm were generated. Adding acetone to carbon dioxide improved the uniformity of the pores compared to foams formed by carbon dioxide alone. In addition, a unique high-pressure solution extrusion system was designed and used to form porous tubular constructs by piston-extrusion of a solution from a high-pressure dissolution chamber through an annular die into a second chamber maintained at controlled pressure/temperature and fluid conditions. Long uniform porous tubular constructs with 6 mm ID and 1 mm wall thickness were generated with glassy polymers like poly(methyl methacrylate) by extruding solutions composed of 50 wt% polymer + 50 wt% acetone, or 25 wt% polymer + 10% acetone + 65% carbon dioxide at 70 °C and 28 MPa. Pores were in the 50 μm range. The feasibility of forming similar tubular constructs were demonstrated with poly(ɛ-caprolactone-co-lactide) as well. Tubular foams of the copolymer with interconnected pores with pore sizes in the 50 μm range were generated by extrusion of the copolymer solution composed of 25 wt% polymer + 10 wt% acetone + 65 wt% carbon dioxide at 70 °C and 28 MPa. Reducing the ...
Carbon Dioxide Foaming Of Poly Porous Metal Surfaces Supercritical Fluid Mixtures Tubular Foams Solution Extrusion Porous Constructs Tubular Constructs Uniform Dimensions Acetone Mixtures
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