Biodegradable Polylactide‐Based Composites

The aim of this chapter is to introduce to the use and possible applications of polylactide‐based composites. Polylactides are biodegradable aliphatic polyesters, which are widely used in medical and ecological‐friendly fields. First of all, a deep description of main characteristics of polylactides is shown. This chapter summarizes many concepts, which comprehend a general view of polylactide biopolymers such as synthesis and structures, physical‐chemical and mechanical characterization and possible applications of final products. Then, an overview of composites based on polylactides and their benefits compared with bare polylactides are described

A review on recent developments in binder jetting metal additive manufacturing: materials and process characteristics

Binder Jetting Metal Additive Manufacturing (BJ-MAM), known also as metal 3D-printing, is a powder bed-based additive manufacturing technology. It consists of the deposition of liquid binder droplets to selectively join powder particles to enable the creation of near-net shaped parts, which subsequently are consolidated via sintering process. This technology is known for its capability to process a wide range of different materials and for its orientation towards large volume production series. Binder Jetting has recently been drawing the attention of both the research sphere as well as several industrial sectors. The present review study encompasses the various and most remarkable aspects of BJ-MAM part fabrication. The review covers the material selection and characterisation considerations, followed by the manufacturing process features and the parameter effect on different part properties. It concludes with an overview concerning the most recent case studies with regards to diverse metal alloy developments.This work has been done within the ADDISEND project supported by the ELKARTEK program of the Basque Government [KK-2018/00115]

Role of Inorganic Fillers on the Physical Aging and Toughness Loss of PLLA/BaSO4 Composites

The addition of inorganic fillers has been reported to increase the toughness of poly(l-lactide) (PLLA), but the effect of physical aging in such composites has been neglected. The present work discusses the effect of the still ongoing segmental relaxation in PLLA-based composites filled with BaSO4 inorganic particles in regard of the filler quantity. By means of differential scanning calorimetry, X-ray diffraction, and tensile testing of progressively aged PLLA filled with particles ranging from 0.5–10 wt %, we observed an increase in the mechanical energy required to activate the plastic flow of the primary structure in the PLLA matrix, which resulted in the embrittlement of the majority of composites upon enough aging. Results further clarify the role of debonding in the activation process of PLLA, and the behavior of the composite is described at the segmental level. Only an addition of 10% of particles has effectively preserved a ductile behavior of the samples beyond 150 aging days; therefore, we strongly remark the significance of studying the effect of physical aging in such composites.The authors thank funding from the Basque Government (GV/EJ)-Department of Education, University and Research (consolidated research groups IT-1766-22 GIC21/131) and grant PID2019-106236 GB-I00 funded by MCIN/AEI/10.13039/501100011033 and PID2022-139821OB-I00 funded by MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe”. The Basque Government (GV/EJ) predoctoral grant for X.L. and SGIker technical services (UPV/EHU) for XRD and SEM support is also acknowledged

Lactide and Ethylene Brassylate-Based Thermoplastic Elastomers and Their Nanocomposites with Carbon Nanotubes: Synthesis, Mechanical Properties and Interaction with Astrocytes

Polylactide (PLA) is among the most commonly used polymers for biomedical applications thanks to its biodegradability and cytocompatibility. However, its inherent stiffness and brittleness are clearly inappropriate for the regeneration of soft tissues (e.g., neural tissue), which demands biomaterials with soft and elastomeric behavior capable of resembling the mechanical properties of the native tissue. In this work, both L- and D,L-lactide were copolymerized with ethylene brassylate, a macrolactone that represents a promising alternative to previously studied comonomers (e.g., caprolactone) due to its natural origin. The resulting copolymers showed an elastomeric behavior characterized by relatively low Young’s modulus, high elongation at break and high strain recovery capacity. The thermoplastic nature of the resulting copolymers allows the incorporation of nanofillers (i.e., carbon nanotubes) that further enable the modulation of their mechanical properties. Additionally, nanostructured scaffolds were easily fabricated through a thermo-pressing process with the aid of a commercially available silicon stamp, providing geometrical cues for the adhesion and elongation of cells representative of the nervous system (i.e., astrocytes). Accordingly, the lactide and ethylene brassylate-based copolymers synthesized herein represent an interesting formulation for the development of polymeric scaffolds intended to be used in the regeneration of soft tissues, thanks to their adjustable mechanical properties, thermoplastic nature and observed cytocompatibility.Grant PID2019-106236GB-I00 funded by MCIN/AEI/10.13039/501100011033. The authors are also thankful for funds from the Basque Government, Department of Education (IT-1766-22). C.B.-Á.: acknowledges the predoctoral grant funded by the UPV/EHU. Polimerbio and Y.P. have a Bikaintek Ph.D. grant (20-AF-W2-2018-00001)

Benefits of Polydopamine as Particle/Matrix Interface in Polylactide/PD-BaSO4 Scaffolds

This work reports the versatility of polydopamine (PD) when applied as a particle coating in a composite of polylactide (PLA). Polydopamine was observed to increase the particle–matrix interface strength and facilitate the adsorption of drugs to the material surface. Here, barium sulfate radiopaque particles were functionalized with polydopamine and integrated into a polylactide matrix, leading to the formulation of a biodegradable and X-ray opaque material with enhanced mechanical properties. Polydopamine functionalized barium sulfate particles also facilitated the adsorption and release of the antibiotic levofloxacin. Analysis of the antibacterial capacity of these composites and the metabolic activity and proliferation of human dermal fibroblasts in vitro demonstrated that these materials are non-cytotoxic and can be 3D printed to formulate complex biocompatible materials for bone fixation devices.The authors express thanks for technical and human support provided by SGIker of UPV/EHU and European funding: European Regional Development Fund (ERDF) and European Social Fund (ESF)

Miscibility and phase behavior of reactively compatibilized poly(lactic acid)/poly(butylene succinate) bio-blends using various rheological analyses

This study focuses on the compatibilization of PLA/poly(butylene succinate) (PBS) blends using mono- and multi-epoxide POSS (MoEpPOSS and MuEpPOSS) nanoparticles, from a rheological point of view for the first time in the literature. The addition of PBS to PLA decreased the complex viscosity, storage modulus, and loss modulus, indicating weak interactions between polymers. However, the incorporation of MoEpPOSS and MuEpPOSS increased the complex viscosity and storage modulus due to the formation of long polymeric chains or complex polymeric structures through interactions between the epoxide groups of POSS and the end groups of the polymers. The effect was more significant with MuEpPOSS because MuEpPOSS has multiple epoxide groups in its cage structure, leading to stronger interactions with the polymers. POSS incorporation resulted in semicircular and arc-shaped curves in the Cole-Cole plots, indicating better dispersion, phase homogeneity, and compatibility. The introduction of POSS also influenced the dynamic loss tangent (tan δ) versus frequency (ω) plot. When POSS was introduced, the tan δ peak decreased and shifted to a higher frequency, indicating improved compatibility, and enhanced interfacial adhesion. These findings indicated that the addition of epoxy-POSS nanoparticles can effectively compatibilize PLA/PBS blends and enhance their rheological properties, potentially improving their overall performance for various applications

Predicting miscibility in polymer blends using the Bagley plot: Blends with poly(ethylene oxide)

This paper explores the different methods currently available to obtain the partial solubility parameters of polymers in order to apply them for the prediction of miscibility in polymer/polymer blends. Blends based on poly(ethylene oxide) (PEO) have been chosen because its miscibility has been reported with a large number of polymeric counterparts (miscible or not), allowing the representation of its miscibility map with the required detail. The solubility parameters of PEO and 55 blending partners have been obtained using the most widely used group contribution (GC) methods, namely the ones proposed by Hoy, Hoftyzer-Van Krevelen, Stefanis-Panayiotou and Yamamoto (Y-MB), and have been used to build a Bagley plot. In addition, the miscibility map based on experimental data obtained from solubility tests has been also obtained and compared with the calculated ones. The clouds of points obtained around the point corresponding to PEO show different shapes, that can be used to obtain conclusions about the coherence and the accuracy of each of the different methods used to obtain the solubility parameters of polymers.The authors are thankful for funds from the Spanish Ministry of Innovation and Competitiveness MINECO (MAT2013-45559-P), the Basque Government, Department of Education, Universities and Research (GIC12/161-IT-632-13) and the European COST Action TD1305 - iPROMEDAI.Peer reviewe

Radiopaque Material for 3D Printing Scaffolds

The so called “Additive manufacturing” is a new manufacturing process which consists in translating virtual solid model data into physical models in a quick and easy process. The most known example is 3D printing. In the present work, this novel technology will be used to print scaffolds with biomaterials. Due to the problems that arise when controlling the clinical course of an implant, graft or polymer inside the human body, an innovative idea has emerged: it consists in incorporating particles of barium sulfate in order to increase the radiopacity of the polylactide (PLLA) and thus making these materials visible to X-rays. Accordingly, BaSO4 loaded PLLA composites were prepared via melt-blending and then injected for further characterization by thermal transitions, mechanical properties, morphology and radiopacity. X-ray analyses confirmed the enhanced radiopacity of the BaSO4 filled composites in comparison to their unfilled counterparts. It is demonstrated that the loads not only contribute to the material's radiopacity, but also dramatically improve its ductility. As an illustration, the incorporation of 10 wt.% of BaSO4 particles resulted in an outstanding 1647% and 3338% increase in toughness and elongation of PLLA matrix, respectively. In view of the good properties of these materials, they will be used for 3D printing. Through this technique it can be molded with any shape in a matter of minutes, making the use of this technology appealing for further innovations.Authors are thankful for funds of Basque Government (GV/EJ) Department of Education (IT-927-16) and from MINECO (MAT 2016-78527-P). N. Sadaba is thankful for the predoctoral fellowship to POLYMAT Fundazioa- Basque Center for Macromolecular Design and Engineering