Abstract
Biodegradable coronary stents have been under development for several years and a trend in biodegradable stent material development has emerged: reinforcement to enhance mechanical properties and creep resistance to improve vessel support. The aim of this work is to investigate the mechanical and viscoelastic characteristics of poly(L-lactic acid)/poly (glycolic acid) (PLLA/PGA) microfibrillar polymer-polymer composites (MFCs) at 37°C to determine the suitability of PGA fibrils as a reinforcement for polymeric, biodegradable stents. PLLA/PGA MFCs were produced via cold-drawing and subsequent compression moulding of extruded PLLA/PGA blend wires. Scanning electron microscopy revealed excellent fibril formation in the case of a 70/30 wt% PLLA/PGA MFC- the mean fibril diameter being 400 nm and aspect ratios exceeding 250. Tensile tests demonstrate Young's modulus and strength increases of 35 and 84% over neat PLLA in the case of a 70/30 wt% PLLA/PGA MFC. Creep resistance of the PLLA/PGA MFCs is lower than that of neat PLLA, as shown via relaxation. Dynamic mechanical thermal analysis demonstrates that it is the onset of glass transition of PGA that is the underlying cause for low creep resistance of the PLLA/PGA MFCs at 37°C.
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