4D Numerical Analysis of Scaffolds: A New Approach

A large range of biodegradable polymers are used to produce scaffoldsfor tissue engineering, which temporarily replace the biomechanical functions ofa biologic tissue while it progressively regenerates its capacities. However, the mechanicalbehavior of biodegradable materials during its degradation, which is an importantaspect of the scaffold design, is still an unexplored subject. For a biodegradablescaffold, performance will decrease along its degradation, ideally in accordanceto the regeneration of the biologic tissue, avoiding the stress shielding effect or thepremature rupture. In this chapter, a new numerical approach to predict the mechanicalbehavior of complex 3D scaffolds during degradation time (the 4th dimension)is presented. The degradation of mechanical properties should ideally be compatibleto the tissue regeneration. With this new approach, an iterative process of optimizationis possible to achieve an ideal solution in terms of mechanical behavior anddegradation time. The scaffold can therefore be pre-validated in terms of functionalcompatibility. An example of application of this approach is demonstrated at the endof this chapter

Cork-like filaments for Additive Manufacturing

A cork-like filament fully biodegradable and filled with low granulometry cork powder residues was developed. Cork-polymer composites (CPC) were prepared using a Brabender type mixer incorporating 15% (w/w) of cork powder (corresponding to 55% (v/v)) and having polylactic acid (PLA) as matrix. In order to promote a chemical adhesion between cork particles and PLA, the effect of maleic anhydride grafted PLA (MAgPLA) was studied. Fourier Transform Infrared – Attenuated Total Reflection (FTIR-ATR) analysis was used to evaluate the func- tionalization of MAgPLA onto the polymeric chain. The addition of MAgPLA enhanced the mechanical behavior by increasing tensile properties while improving the dispersion of cork particles within PLA matrix. In addition, cork particles and MAgPLA acted as nucleating agents during PLA melting process. To evaluate the printability of the developed CPC filament, specimens were printed by Fused Filament Fabrication (FFF) and compared to those obtained by injection molding (IM). FFF allowed to preserve the cork alveolar structure in the specimens, benefiting CPC mechanical behavior. 3D parts could be printed with the CPC filament thereby demonstrating the usefulness of the fully biodegradable cork-based filament here developed. 3D printed parts exhibit unique characteristics, such as a nonplastic and warm touch, a natural colour and the release of a pleasant odour during the printing process.publishe

Non-isothermal cold crystallization kinetics of cork–polymer biocomposites based on polylactic acid for fused filament fabrication

Cork–polymer composites (CPC) based on polylactic acid (PLA) matrix were prepared for the development of flaments for fused flament fabrication. The non-isothermal cold crystallization behaviours of PLA and CPC were investigated by diferential scanning calorimetry. Cold crystallization kinetic behaviours of PLA and CPC with 15 mass/% of cork powder residues at diferent heating rates (1.25, 2.5, 5 and 7.5 K min−1) were studied. Results showed that cold crystallization temperature (Tcc) of PLA matrix decreased with the addition of cork. Crystallization kinetic behaviour was studied by Avrami and Tobin models. It was shown that cork powder surface acts as a nucleating agent during non-isothermal cold crystallization, by accelerating the crystallization rate and, therefore, by reducing the half-time crystallization (t1/2) values. Polarized optical microscopy and X-ray difraction were used to evaluate the crystalline structure of PLA and CPC. Kissinger and Friedman methods were employed to determine the crystallization activation energy (Ec).publishe