The effect of thermal treatment on the mechanical properties of PLLA tubular specimens

Abstract

Conventional permanent stent systems for vascular applications are associated with long-term risks, such as restenosis and thrombosis. To overcome these limitations, novel approaches using various biodegradable materials for stent construction have been investigated. In this context, thermal treatment of polymer materials is investigated to adjust the mechanical properties of biodegradable stents. In this work polymeric tubular specimens of biodegradable poly(L-lactide) (PLLA) were extruded and subjected to a molding process using different temperatures above glass transition temperature TG. Physicochemical properties of the molded samples were analyzed using DSC measurements and uniaxial tensile tests. The molding process resulted in a weakening of the PLLA tubular specimens with a simultaneous increase in the degree of crystallinity (χ).

The Influence of Low Shear Microbore Extrusion on the Properties of High Molecular Weight Poly(l-Lactic Acid) for Medical Tubing Applications

“…There was notable variation in the strain at break results, particularly for Batch A, however when comparing the means and standard deviations, there is no practical significance in the difference. The tensile properties presented in Table 5 are in line with those reported previously [14,18,49,52], however, a direct comparison cannot be made due to differences in process conditions, part geometry and test methods.…”

“…Therefore, the morphology of the extruded tubing will play a key role in the degradation profile of the finished device. Given the low degree of crystallinity imparted during conventional melt processing techniques such as extrusion or injection moulding, secondary processing techniques such as annealing [14,45,46,47] or biaxial expansion [48,49,50,51] are often required to increase the materials crystallinity and improve mechanical properties.…”

Influence of Annealing and Biaxial Expansion on the Properties of Poly(l-Lactic Acid) Medical Tubing

“…However, limited clinical data and questions, remaining over the bioresorbability and processability (dispersion) of many of these nanocomposites, has hindered their emergence into mainstream commercial applications. Therefore, to improve the mechanical properties of PLLA, secondary processing techniques, such as annealing [22,23,24,25,26] or biaxial expansion [27,28,29,30], have been the preferred method employed by commercial medical device manufacturers.…”

Reconstruction of biological functions: novel implant concepts for cardiovascular, ophthal-mologic and otolaryngologic applications

“…New structural scaffold designs, polymeric material formulations, magnesium alloys and process technologies are being investigated in order to overcome limitations of existing devices [2][3][4][5]. Furthermore, scaffold coatings with responsive drug release shall allow for an adaptive implant/tissue interaction in order to improve clinical outcome [6,7].…”