Commercial polyurethanes: The potential influence of auxiliary chemicals on the biodegradation process

This investigation elucidates some aspects of auxiliary chemicals on the bi odegradation of two commercial polyurethanes (Pellethane(R) and Corethane(R )). The materials were incubated for 28 days with cholesterol esterase and/ or with phosphatidylcholine. Extraction studies were carried out on the two materials, using different solvents, chosen on the basis of solvent polari ty, FT-IR spectra for the extracted materials indicated the presence of pol y(methylene)(n) oxide moities, silicone oil, bis-ethylene-stearamide, aroma tic moities, and alkyd-urea compounds in Pellethane(R). Corethane(R) materi als were shown to contain some fatty acids, hydrocarbon waxes, ester-based species, and chlorinated compounds. Analysis of incubation solutions by hig h performance liquid chromatography failed to isolate methylene dianiline ( MDA) or any of its derivatives from the various polymer incubation solution s. However, a methanol extract of Corethane(R) samples that were incubated for 28 days in cholesterol esterase did show the presence of MDA, The absen ce of MDA in the Pellethane methanol extracted samples may reflect the diff erences in surface additives found for this material versus the Corethane. FT-IR/ATR analysis of polymer surfaces exposed to cholesterol esterase/phos pholipids mixture showed that there was an increase in the uptake of phosph olipids over samples that were incubated in phospholipid dispersion alone. The results of this study show that some of the auxiliary chemicals found i n commercial polyurethanes may hinder the specific release of hydrolytic de gradation products and delay polymer degradation. However, it should be rec ognized that the surface layer containing these compounds is susceptible to change following the interaction between the polyurethane-based devices an d elements of the host environment (i.e. lipids, enzymes, etc.). Hence, rec ognition and identification of these changes will ultimately be important i n assessing a commercial polymer's blood compatibility characteristics.