Molding of Segmented Polyurethane Devices. Delamination Events and Stretching Behavior

ABRAHAM,G.A.; FRONTINI,P.M.; CUADRADO,T.R.

JOURNAL OF APPLIED POLYMER SCIENCE

John Wiley & Sons, Inc.

Lugar: New York, USA; Año: 1998 vol. 69 p. 2159 - 2167

0021-8995

Segmented Polyurethane devices for medical applications are generally processed by solution-casting technique. The processing parameters, in both molding and de-molding stages, strongly affect the physico-chemical properties of the finished articles. Thus, the solution concentration, immersion cycle and drying temperature, type of mold (material and geometry), additives and the drying time between casting of successive layers define the surface and bulk properties of the manufactured articles. In this work, new commercially available medical-grade segmented polyurethanes were processed by two techniques to obtain multilayer films. Processing parameters were chosen in order to ensure the generation of a coating with desired structural and surface characteristics. In the case of solution-casting technique, multiple dipping of the pre-shaped former into the polymer solution were used to obtain proper film thickness. Thin and uniform plaques were produced by spin-casting technique. The two materials selected have different chemical composition: one is an aromatic poly(ether urethane urea), Biospan™, and the other an aliphatic ether-free polyurethane, Chronoflex™. An analysis of the possibility of delamination events, considering both the influence of surface-modifying additives and drying times is presented. The freeze-fracture surface appearance is qualitatively described by SEM. In addition tensile properties were determined and their influence on de-molding and assembling procedures are also discussed.