EcoBlends'up:

En ciertas mezclas de polímeros una morfología microfibrilar de la fase dispersa debidamente orientada durante la etapa de procesamiento, puede generar un efecto reforzante aumentando la tenacidad a la fractura, sobre todo en la etapa de propagación de grieta. Este tipo de materiales se denominan “compuestos microfibrilados in situ” (MFCs). Su obtención viene condicionada por las propiedades reológicos de la mezcla y los parámetros del proceso de conformado. En este contexto, cobra interés la fabricación aditiva, especialmente la fabricación por filamento en fundido (FFF) con aporte de granza en vez de filamento. En este trabajo, se propone el estudio de la viabilidad de fabricación MFCs induciendo la microfibrilación de una BioPA en las “ecoblends” PLA/BioPA. Se evalúan las condiciones óptimas de procesamiento del proceso FFF para su generación, el comportamiento a tracción uniaxial y el comportamiento a fractura (mediante técnicas de impacto instrumentado en probetas SENB) de las probetas resultantes. Las evidencias obtenidas muestran que el uso de una matriz de PLA modificada reológicamente mediante extrusión reactiva (PLAREx) promueve la obtención de MFCs con un mejor balance de propiedades mecánicas en términos de módulo elasticidad (E) y ductilidad, y una mejora en la tenacidad aparente de la estructura fabricada.Postprint (published version

In vitro degradation of 3D-printed polycaprolactone\biomimetic hydroxyapatite scaffolds: Impact of the sterilization method

In the transition from the laboratory to the clinic, the sterilization of medical devices becomes a fundamental and mandatory step to ensure patient safety. This work evaluates the impact of three different sterilization methods - autoclave, ethylene oxide and gamma irradiation - on the physicochemical properties and degradation kinetics of 3D-printed polycaprolactone\calcium deficient hydroxyapatite (PCL\CDHA) scaffolds for bone regeneration. The in vitro degradation test was performed in phosphate buffer saline solution at 47 °C for 18 weeks by recording the evolution of pH, scaffold morphology, swelling degree, mass loss as well as polymer content, molecular weight and crystallinity. The results showed that under thermally accelerated degradation, the scaffolds underwent hydrolytic bulk degradation without altering the pH of the soaking medium nor compromising the morphology and integrity of the constructs. Although the structural integrity of the scaffolds was maintained, autoclaving severely deteriorated the properties of the polymer, resulting in a faster degradation pattern, confirming that it is not an appropriate sterilization method for PCL\CDHA scaffolds. While ethylene oxide had no significant effect on degradation, gamma irradiation slightly accelerated hydrolysis by chain scission. However, due to the porous nature of the scaffolds, the use of ethylene oxide is inadvisable due to the risk of gas trapping in the pores. Therefore, gamma irradiation, a non-toxic, effective, predictable and reproducible sterilization method, is considered the most appropriate.Peer ReviewedPostprint (published version

EcoBlends'up: compuestos de PLA/BioPA, microfibrilados

In certain polymer blends, a properly oriented microfibrillar morphology of the dispersed phase during the processing stage can generate a reinforcing effect by increasing the fracture toughness, especially in the crack propagation stage. These types of materials are called “in situ” microfibrillated composites (MFCs). Its obtention is conditioned by the rheological properties of the blend and the parameters of the forming process. In this context, additive manufacturing is of interest, specially fused filament fabrication (FFF) by pellets supply instead of extruded filaments. In this work, the study of the feasibility of manufacturing MFCs is proposed by inducing the microfibrillation of a BioPA in the PLA/BioPA “ecoblends”. The optimal processing conditions of the FFF process for the generation of MFCs are evaluated, as well as the uniaxial tensile behavior and the fracture behavior of the manufactured SENB test specimens, employing instrumented impact technique. The evidence obtained shows that the use of a rheologically modified PLA matrix by reactive extrusion (PLAREX) promotes the obtention of MFCs with a better balance of mechanical properties in terms of elastic modulus (E) and ductility and an improvement in apparent toughness and resistance to crack propagation of the fabricated part.Peer ReviewedPostprint (author's final draft