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Long‐term in vitro hydrolytic stability of thermoplastic polyurethanes
Author(s) -
Mishra Abhinay,
Seethamraju Kasyap,
Delaney Joseph,
Willoughby Patrick,
Faust Rudolf
Publication year - 2015
Publication title -
journal of biomedical materials research part a
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.849
H-Index - 150
eISSN - 1552-4965
pISSN - 1549-3296
DOI - 10.1002/jbm.a.35523
Subject(s) - materials science , in vivo , hydrolysis , thermal stability , thermoplastic , ultimate tensile strength , kinetics , nuclear chemistry , in vitro , arrhenius equation , composite material , activation energy , chemistry , organic chemistry , biochemistry , physics , microbiology and biotechnology , quantum mechanics , biology
Abstract Long‐term in vitro stability of thermoplastic polyurethanes (TPUs) was studied for up to 52 weeks in phosphate buffer solution at 37, 55, and 80°C. Water uptake, molecular weights, and tensile properties were measured at regular intervals of 4, 8, 16, 32, and 52 weeks. The rate of molecular weight reduction increased with increasing temperature, and after 52 weeks at 80°C, all commercial polycarbonate (Bionate‐55D, Quadrathane‐80A, and Chronoflex‐80A), poly(dimethylsiloxane) (ElastEon‐2A) and polyether (Elasthane‐55D) TPUs showed significant (43–51%) molecular weight ( M n ) reduction. The polyisobutylene (PIB)‐based TPU exhibited a significantly lower decrease in M n (26%) after 52 weeks at 80°C. For Bionate‐55D and ElastEon‐2A, at 80°C in dry nitrogen atmosphere substantial thermal degradation was observed, while for the other TPUs the effect of thermal degradation is small. The temperature dependent reduction of molecular weight was interpreted by simple second order kinetics. From the approximately linear Arrhenius plots the activation energies were calculated, which were highest for PIB‐PU‐020 and lowest for ElastEon‐2A. For Elasthane‐55D the in vitro molecular weight reduction was compared with that of explanted leads. The molecular weight reduction in vivo was much smaller than that predicted from in vitro data, which may suggest that the in vitro model does not adequately describe the hydrolysis in vivo . In the absence of validation for the other TPUs that in vitro methods closely reproduce in vivo degradation, it is unknown how these results correlate with in vivo performance. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 3798–3806, 2015.