Does magnesium compromise the high temperature processability of novel biodegradable and bioresorbables PLLA/Mg composites?

Abstract

This paper addresses the influence of magnesium on melting behaviour and thermal stability of novel bioresorbable PLLA/Mg composites as a way to investigate their processability by conventional techniques, which likely will require a melt process at high temperature to mould the material by using a compression, extrusion or injection stage. For this purpose, and to avoid any high temperature step before analysis, films of PLLA loaded with magnesium particles of different sizes and volume fraction were prepared by solvent casting. DSC, modulated DSC and thermogravimetry analysis demonstrate that although thermal stability of PLLA is reduced, the temperature window for processing the PLLA/Mg composites by conventional thermoplastic routes is wide enough. Moreover, magnesium particles do not alter the crystallization behaviour of the polymer from the melt, which allows further annealing treatments to optimize the crystallinity in terms of the required combination of mechanical properties and degradation rate. RESUMEN: ¿Compromete el magnesio la procesabilidad a elevada temperatura de nuevos materiales compuestos biodegradables y biorreabsorbibles de PLLA/Mg?.Este trabajo aborda la influencia de magnesio en el comportamiento a fusión y en la estabilidad térmica de nuevos compuestos de PLLA / Mg biorreabsorbibles como una forma de investigar su procesabilidad mediante técnicas convencionales, lo que probablemente requerirá una etapa en estado fundido a alta temperatura para moldear el material mediante el uso de una etapa de compresión, extrusión o inyección. Para este fin, los materiales de PLLA cargados con partículas de magnesio, de diferentes tamaños y fracción de volumen, se prepararon por la técnica de disolución y colada, evitando así el procesado a alta temperatura antes del análisis. El análisis mediante DSC, DSC modulada y termogravimetría demuestra que, aunque la estabilidad térmica de PLLA se reduce, el intervalo de temperatura para su procesado por rutas convencionales es suficientemente amplio. Además, las partículas de magnesio no alteran la cristalización del polímero a partir del fundido, lo que permitirá optimizar el grado de cristalinidad mediante tratamientos posteriores de recocido y conseguir así una adecuada combinación de propiedades mecánicas y velocidad de degradación.

Advancements in the Additive Manufacturing of Magnesium and Aluminum Alloys through Laser-Based Approach

“…The additively manufactured Mg-RE alloy has received the greatest attention for use in biomedical implants especially WE43 alloy. Although WE43 alloy attains significant importance in biomedical applications, it also has good printability which accounts for a new doorway in order to achieve the reduced porosity [99,100], better than AZ91 as dis-…”

“…The additively manufactured Mg-RE alloy has received the greatest attention for use in biomedical implants especially WE43 alloy. Although WE43 alloy attains significant importance in biomedical applications, it also has good printability which accounts for a new doorway in order to achieve the reduced porosity [99,100], better than AZ91 as discussed in [93]. Being biocompatible, WE43 alloy does not cause any negative cell reactions such as cytotoxicity, whereas Aluminum in Mg-Al alloy accounted for cytotoxicity.…”

Antibacterial effect of novel biodegradable and bioresorbable PLDA/Mg composites

“…The temperature range over which the loss of mass occurs for the PLDA/Mg composites is lower and narrower than that for the neat polymer (270°C-320 °C). It is worth noting that although thermal decomposition of the polymer is accelerated by the presence of Mg [5,37], the processability of the composites was not compromised and suitable processing conditions were acquired for this study. Mg particles are well distributed within the PLDA/Mg composites as demonstrated by TGA (figure 2) and the optical microscopy analysis of cross-sections (figure 3).…”

“…However, their use in clinical practice has been limited due to their insufficient osseointegration and low mechanical properties [1][2][3][4]. We have recently demonstrated the feasibility of introducing magnesium (Mg) particles within a PLLA (poly-L-lactic acid) matrix [5,6] as a new strategy to improve the mechanical properties of poly-L-D-lactic acid (PLDA) [7] and simultaneously modulate the degradation rate of Mg [8]. In addition, Mg-containing polymers regulate mesenchymal stem cell (MSC) behavior at the biomaterial interface and inflammatory response mediated by macrophages [7].…”