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Rheology and extrusion of medical‐grade thermoplastic polyurethane
Author(s) -
Lu Guangyu,
Kalyon Dilhan M.,
Yilgör Iskender,
Yilgör Emel
Publication year - 2003
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.10158
Subject(s) - thermoplastic polyurethane , materials science , rheology , extrusion , composite material , thermoplastic , lubricant , polyurethane , viscosity , shear rate , elastomer
The selection of operating conditions and geometry for the processing of thermoplastic polyurethane, TPU, is a complicated task. This complication arises from the relatively high melting temperature of the crystalline hard blocks and the oxidative and thermal degradation and crosslinking that occur at temperatures that are relatively close to the melting temperature of the TPU. This article documents the rheology, extrusion, and structure development of a medical‐grade TPU. The medical application requires that the additives commonly utilized in the development of polymeric resins, i.e., stabilizers, antioxidants, and lubricant, should be minimized; the TPU of this study contains no additives. At temperatures 10–20°C lower than the melting temperature of the TPU, the morphology of the hard blocks continues to evolve to generate a reversible increase in elasticity and shear viscosity of the TPU with increasing time. At temperatures greater than the melting temperature, the TPU undergoes degradation and crosslinking reactions, which give rise to a permanent increase in the elasticity and the shear viscosity of the TPU. The ramifications of the degradation and crosslinking at temperatures greater than 200°C and morphology modification upon the continuing evolution of the hard blocks at temperatures less than 200°C on the rheology and processing were investigated.