Effect of the viscosity ratio on the PLA/PA10.10 bioblends morphology and mechanical properties

PLA bio-blends with a predominantly biosourced PA10.10 in the composition range 10-50wt.% were prepared by melt blending in order to overcome the advanced brittleness of PLA. Due to the inherent immiscibility of the blends, 30 wt.% of PA was needed to achieve a brittle-to-ductile transition and a co-continuous morphology was predicted at 58 wt.% of PA. The initial enhancement of the PLA rheological behaviour through the environmentally friendly reactive extrusion process yielded a finer and more homogeneous microstructure and hence enhanced the mechanical properties of the bio-blends at much lower PA contents. The brittle-to-ductile transition could be achieved with only 10 wt.% and co-continuity was observed already at 44 wt.% of PA. Results indicate the significant potential of modifying PLA flow behaviour as a promising green manufacturing method toward expanding PLA-based bio-blends applications.Peer ReviewedPostprint (published version

Multivariate identification of extruded PLA samples from the infrared spectrum

This is a post-peer-review, pre-copyedit version of an article published in Journal of materials science. The final authenticated version is available online at: http://dx.doi.org/10.1007/s10853-019-04091-6Polylactic acid (PLA) is a biodegradable thermoplastic polymer that is presented as a good alternative to petroleum-derived plastics. Some of the major drawbacks of this material are its lack of thermal stability and rapid degradation in large-scale production; thus, special care must be taken during processing. To improve their properties, a reactive extrusion with a multi-epoxy chain extender (SAmfE) has been performed at pilot plant scale. The induced topological modifications produce a mixture of several types of non-uniform structures. Conventional chromatographic (SEC—static light scattering) or spectroscopic (nuclear magnetic resonance) techniques usually fail in characterizing non-uniform structures. A method for the classification of modified PLA samples based on a multivariate treatment of the spectral data obtained by Fourier-transform infrared spectroscopy, jointly with the application of feature extraction and classification algorithms, was applied in this study. The results of this work show the potential of the methodology proposed to improve quality control during manufacturing.Peer ReviewedPostprint (author's final draft

PLA/PA bio-blends: induced morphology by extrusion

The effect of processing conditions on the final morphology of Poly(Lactic Acid) (PLA) with bio-based Polyamide 10.10 (PA) 70/30 blends is analyzed in this paper. Two types of PLA were used: Commercial (neat PLA) and a rheologically modified PLA (PLAREx), with higher melt elasticity produced by reactive extrusion. To evaluate the ability of in situ micro-fibrillation (µf) of PA phase during blend compounding by twin-screw extrusion, two processing parameters were varied: (i) Screw speed rotation (rpm); and (ii) take-up velocity, to induce a hot stretching with different Draw Ratios (DR). The potential ability of PA-µf in both bio-blends was evaluated by the viscosity (p) and elasticity (k’) ratios determined from the rheological tests of pristine polymers. When PLAREx was used, the requirements for PA-µf was fulfilled in the shear rate range observed at the extrusion die. Scanning electron microscopy (SEM) observations revealed that, unlike neat PLA, PLAREx promoted PA-µf without hot stretching and the aspect ratio increased as DR increased. For neat PLA-based blends, PA-µf was promoted during the hot stretching stage. DMTA analysis revealed that the use of PLAREx PLAREx resulted in a better mechanical performance in the rubbery region (T > Tg PLA-phase) due to the PA-µf morphology obtained.Peer ReviewedPostprint (published version

3D printed scaffolds with core-shell structure for bone tissue engineering

Biomaterials with core-shell structure have been used as carriers for drug delivery applications and cell encapsulation, allowing several improvements in the field of tissue engineering. Although the usefulness of biomaterials with this morphology has been already proved in several studies, the development of core-shell fibrous structures by 3D printing technologies could be the key to the advancement of their applications at a larger scale. The aim of this project is to generate tridimensional scaffolds with core-shell fibrous morphology and drug-delivery capability, using a direct ink writing method, for bone regeneration purposes. Self-supporting alginate-based hydrogel inks and self-setting alpha tricalcium phosphate-based cement inks were optimized, and 3D printed core-shell structure scaffolds were successfully generated by direct ink writing, with either a hydrogel-hydrogel or a cement-hydrogel core-shell composition. Afterwards, cement-hydrogel core-shell 3D printed scaffolds with dual drug-delivery capability were designed. Cobalt ions, which have pro-angiogenic effect, and Cytochrome C, a model protein simulating BMP-2 osteogenic factor, were loaded in the hydrogel shell and the cement core of the printed scaffolds, respectively. The evaluation of their delivery kinetics which showed a burst release of both factors, allowed to prove the dual drug delivery potential of the 3D printed cement-hydrogel core-shell scaffolds generated in this study

3D printed scaffolds with core-shell structure for bone tissue engineering

Biomaterials with core-shell structure have been used as carriers for drug delivery applications and cell encapsulation, allowing several improvements in the field of tissue engineering. Although the usefulness of biomaterials with this morphology has been already proved in several studies, the development of core-shell fibrous structures by 3D printing technologies could be the key to the advancement of their applications at a larger scale. The aim of this project is to generate tridimensional scaffolds with core-shell fibrous morphology and drug-delivery capability, using a direct ink writing method, for bone regeneration purposes. Self-supporting alginate-based hydrogel inks and self-setting alpha tricalcium phosphate-based cement inks were optimized, and 3D printed core-shell structure scaffolds were successfully generated by direct ink writing, with either a hydrogel-hydrogel or a cement-hydrogel core-shell composition. Afterwards, cement-hydrogel core-shell 3D printed scaffolds with dual drug-delivery capability were designed. Cobalt ions, which have pro-angiogenic effect, and Cytochrome C, a model protein simulating BMP-2 osteogenic factor, were loaded in the hydrogel shell and the cement core of the printed scaffolds, respectively. The evaluation of their delivery kinetics which showed a burst release of both factors, allowed to prove the dual drug delivery potential of the 3D printed cement-hydrogel core-shell scaffolds generated in this study

3D printed scaffolds with core-shell structure for bone tissue engineering

Biomaterials with core-shell structure have been used as carriers for drug delivery applications and cell encapsulation, allowing several improvements in the field of tissue engineering. Although the usefulness of biomaterials with this morphology has been already proved in several studies, the development of core-shell fibrous structures by 3D printing technologies could be the key to the advancement of their applications at a larger scale. The aim of this project is to generate tridimensional scaffolds with core-shell fibrous morphology and drug-delivery capability, using a direct ink writing method, for bone regeneration purposes. Self-supporting alginate-based hydrogel inks and self-setting alpha tricalcium phosphate-based cement inks were optimized, and 3D printed core-shell structure scaffolds were successfully generated by direct ink writing, with either a hydrogel-hydrogel or a cement-hydrogel core-shell composition. Afterwards, cement-hydrogel core-shell 3D printed scaffolds with dual drug-delivery capability were designed. Cobalt ions, which have pro-angiogenic effect, and Cytochrome C, a model protein simulating BMP-2 osteogenic factor, were loaded in the hydrogel shell and the cement core of the printed scaffolds, respectively. The evaluation of their delivery kinetics which showed a burst release of both factors, allowed to prove the dual drug delivery potential of the 3D printed cement-hydrogel core-shell scaffolds generated in this study

Multivariate identification of extruded PLA samples from the infrared spectrum

This is a post-peer-review, pre-copyedit version of an article published in Journal of materials science. The final authenticated version is available online at: http://dx.doi.org/10.1007/s10853-019-04091-6Polylactic acid (PLA) is a biodegradable thermoplastic polymer that is presented as a good alternative to petroleum-derived plastics. Some of the major drawbacks of this material are its lack of thermal stability and rapid degradation in large-scale production; thus, special care must be taken during processing. To improve their properties, a reactive extrusion with a multi-epoxy chain extender (SAmfE) has been performed at pilot plant scale. The induced topological modifications produce a mixture of several types of non-uniform structures. Conventional chromatographic (SEC—static light scattering) or spectroscopic (nuclear magnetic resonance) techniques usually fail in characterizing non-uniform structures. A method for the classification of modified PLA samples based on a multivariate treatment of the spectral data obtained by Fourier-transform infrared spectroscopy, jointly with the application of feature extraction and classification algorithms, was applied in this study. The results of this work show the potential of the methodology proposed to improve quality control during manufacturing.Peer Reviewe

PLA/BIOPA bioblends for FDM: Mechanica and fracture behavior

The fracture behaviour of PLA/PA bioblends has been investigated in order to extend its processing through fused deposition modeling printing by pellets supply (FDM-p). The viability of the processing technique in creating in situ microfibrillated composites (MFCs) through the microfibrillation of the PA dispersed phase has been evaluated as a way to strengthen and toughen PLA. The mechanical behaviour was assessed through uniaxial tensile tests performed at room temperature (22oC) using type 1BA dumbbell tensile test specimens (ISO527-2) featuring an unidirectional infill pattern fully oriented in the longitudinal direction of the samples. The fracture behaviour was assessed through the determination of the CTOD value just before the crack propagation onset in single-edge-notched tension (SENT) test geometry featuring a multi-axial multilayer infill pattern. For all the samples, a nominal filling density of 100 % was predefined. Morphological observations revealed that the 3D printing conditions used in this study allowed the manufacturing of in- situ MFCs with an average diameter of the PA microfibrils as low as 320 nm. The developed morphology led to a significant increase in the structural integrity of the parts manufactured through FDM-p, as clearly evidenced by the 206% increase in the CTOD values as compared to samples obtained through conventional compression-moulding using the same raw pellets.Postprint (published version

Effect of the viscosity ratio on the PLA/PA10.10 bioblends morphology and mechanical properties

PLA bio-blends with a predominantly biosourced PA10.10 in the composition range 10-50wt.% were prepared by melt blending in order to overcome the advanced brittleness of PLA. Due to the inherent immiscibility of the blends, 30 wt.% of PA was needed to achieve a brittle-to-ductile transition and a co-continuous morphology was predicted at 58 wt.% of PA. The initial enhancement of the PLA rheological behaviour through the environmentally friendly reactive extrusion process yielded a finer and more homogeneous microstructure and hence enhanced the mechanical properties of the bio-blends at much lower PA contents. The brittle-to-ductile transition could be achieved with only 10 wt.% and co-continuity was observed already at 44 wt.% of PA. Results indicate the significant potential of modifying PLA flow behaviour as a promising green manufacturing method toward expanding PLA-based bio-blends applications.Peer Reviewe

PLA/PA bio-blends: induced morphology by extrusion

The effect of processing conditions on the final morphology of Poly(Lactic Acid) (PLA) with bio-based Polyamide 10.10 (PA) 70/30 blends is analyzed in this paper. Two types of PLA were used: Commercial (neat PLA) and a rheologically modified PLA (PLAREx), with higher melt elasticity produced by reactive extrusion. To evaluate the ability of in situ micro-fibrillation (µf) of PA phase during blend compounding by twin-screw extrusion, two processing parameters were varied: (i) Screw speed rotation (rpm); and (ii) take-up velocity, to induce a hot stretching with different Draw Ratios (DR). The potential ability of PA-µf in both bio-blends was evaluated by the viscosity (p) and elasticity (k’) ratios determined from the rheological tests of pristine polymers. When PLAREx was used, the requirements for PA-µf was fulfilled in the shear rate range observed at the extrusion die. Scanning electron microscopy (SEM) observations revealed that, unlike neat PLA, PLAREx promoted PA-µf without hot stretching and the aspect ratio increased as DR increased. For neat PLA-based blends, PA-µf was promoted during the hot stretching stage. DMTA analysis revealed that the use of PLAREx PLAREx resulted in a better mechanical performance in the rubbery region (T > Tg PLA-phase) due to the PA-µf morphology obtained.Peer Reviewe