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In this work, we studied the degradability of PLA-based biocomposites containing Posidonia Oceanica flour at different loading levels and aspect ratios. Hydrolytic tests were carried out in neutral (pH = 7.4) and alkaline (pH = 10) environment. Time-dependent evolution of some key features, including residual mass and solution uptake, was monitored, and correlated with the changes observed in both morphology and chemical structure of the matrix. The results pointed out that biocomposites degraded much faster than neat PLA in both conditions, up to lose 70% of their initial weight after 1000 h immersion. A complex mechanism was unveiled, evidencing the crucial role of the fillers, capable of both imparting degradation to PLA during processing with enhancement of hydrophilicity and offering preferential gateways for solution penetration through filler-matrix interface by capillarity and swelling-aided polymer cracking. Based on data collected, we propose a new model allowing to predict the triggering and final extent of degradation pathways by considering starting morphological and chemical features of composites via the use of a novel yet simple indicator of chemical stability, which we called morphochemical parameter.

Ionic tactile sensors (ITS) are an emerging subfield of wearable electronics, capable of mimicking the human skin, including not only the typical anisotropic structure, mechanical behaviour, and tactile functions but even the mechanosensitive ionic channels that are crucial for the human sense of touch. With the rapid development of intelligent technology, such bioinspired materials constitute the core foundation of intelligent systems and are a candidate to be the next generation e-skins, offering a more accurate and evolved biointerface. In the latest years, a wealth of novel ultra-stretchable ITS was proposed, progressively refining the choice of soft materials, including ion gels, ionic liquids and hydrogels, and fabrication techniques. Regardless of materials and methods adopted, all these tactile sensors can feel mechanical solicitations and external stimuli, thus behaving as – or even better than – human skin. In this review, an overview of the very latest advances in high-performance ITS applied in intelligent systems is reported. First, generality of ITS will be summarized. After, ion gel, ionic liquid, hydrogel, and elastomer ITS will be discussed focusing first on composition, fabrication, type and mode of sensing and then on their characteristics and application. In this perspective, the advantages that biomimetic approaches brought in terms of sensitivity, speed of response and multimodality of sensing will be highlighted, with a particular focus on the development of electrochromic, thermochromic, self-powered and self-healing devices. In conclusion, the prospects of tactile sensors for intelligent systems in biomedicine and robotics will be discussed, along with the possible strategies to overcome the current shortcomings, in terms of biocompatibility, durability, mechanical performance, adhesion to biological substrates, which represent the future challenges.

Different processing conditions to achieve polyamide 6 (PA6)-graphene oxide (GO) nanocomposites were investigated. GO was pre-dispersed in PA6 by three different solvent-based methods and, further, melt processed to prepare nanocomposites at two different loading levels, namely 2 and 5 wt.%. The evolution of rheological and mechanical properties was analyzed by investigating eventual changes in the microstructure and polymer crystallinity, aiming at providing a detailed processing-structure-properties relationship for these systems.

Porous membranes and thin films containing poly-lactic acid (PLA), carvacrol (CRV) and graphene nanoplatelets (GNP) were fabricated by electrospinning and solvent casting at different formulations. The systems were characterized from a mechanical, morphological, calorimetric and spectroscopic point of view. CRV release as a function of time was studied and a mathematical model was used to fit and interpret the data in order to investigate the release mechanism. The results indicate that the incorporation of GNP generally determined a simultaneous strengthening, stiffening and toughening effect, while preserving a good ductility. Furthermore, integrating GNP allowed tuning the amount and kinetics of CRV release, and proved to reduce the initial burst release effect.

Biocomposites can valorize some natural products related to natural processes or crop and waste industries. In this work, leaves of Posidonia oceanica (PO), dominant sea grass in the Mediterranean Sea, were used to prepare PLA based biocomposites. Materials were prepared by melt mixing PLA with PO as filler. The morphology as well as the mechanical and thermal properties of PLA/PO composites were evaluated and related with the influence of the content and size of PO. Moreover, the experimental elastic moduli of the biocomposites was modelled employing the Halpin–Tsai (HT) model. Furthermore, in order to take into consideration the high porosity of PO leaves, the HT parameters related to the density of PO were evaluated by estimating the % of PO filled by PLA. The results highlighted that the use of PO leaves as filler influenced all the investigated properties. In particular, by increasing the PO content, both tensile and flexural moduli increased. While, on the contrary, both tensile and flexural strengths of the biocomposites decreased if compared with neat PLA. Finally, the method to determine the parameters for the HT model was found to be able to give a good evaluation of tensile modulus of the composites, for all the filler content and size.

This work focuses on the preparation of a piezoresistive sensor device, by exploiting an amphiphilic sample of graphene oxide (GO) as a compatibilizer for poly (lactic acid) (PLA)-Poly (ethylene-glycol) (PEG) blends. The presence of GO determined a high stiffening and strengthening effect, without affecting toughness, and allowed a good stability of mechanical properties up to 40 days. Moreover, GO endowed the materials with electrical properties highly sensitive to pressure and strain variations: the biodegradable pressure sensor showed a responsivity of 35 μA/MPa from 0.6 to 8.5 MPa, a responsivity around 19 μA/MPa from 8.5 to 25 MPa. For lower pressure values (around 0.16–0.45 MPa), instead, the responsivity increases up to 220 μA/MPa in terms of ΔI/ΔP (i.e. (ΔI/ΔI0)/P close to 1 kPa−1). Furthermore, this novel sensor is able to monitor submicrometric displacements with an impressive sensitivity (up to 25 μA/μm in terms of ΔI/ΔL, or 70 in terms of (ΔI/I0)/ε). We implemented a model able to predict pressure changes up to 25 MPa, by monitoring and measuring variations in electrical conductivity, thus paving the road to use these biodegradable, ecofriendly materials as low-cost sensors for a large pressure range.

In this work, polylactic acid (PLA) membranes at two different carvacrol (CRV) nominal concentration (i.e. 14 wt% and 28 wt%) were prepared via electrospinning technology. The membranes were characterized by scanning electron microscopy, ATR-FTIR and calorimetric measurements as well as tensile tests. Moreover, the release kinetics of CRV in phosphate buffered solution at 37 °C was monitored through UV–Vis measurements and the data were fitted with a power law model. Results indicated that the successful incorporation of CRV in the polymer matrix damaged the fibers morphology but increased all the mechanical parameters investigated (i.e. elastic modulus, tensile strength and elongation). The power law model highlighted that the mechanism of CRV release changed with time from an anomalous release in the first 6 h to a Fickian diffusion mechanism for both the PLA/CRV systems.

PLA/PCL co-mingled nanofibrous mats were prepared via multi-jet electrospinning. The concentration of PLA and PCL in the co-mingled mats were controlled by changing the flow rate of the two polymer solutions. The amount of PLA and PCL in the co-mingled nanofibrous mats was monitored by UV–Vis measurements through a colored dye added to PLA and by FTIR-ATR analysis. Morphology and mechanical properties of the nanofibrous mats were respectively examined by scanning electron microscopy (SEM) and tensile tests. Water contact angles measurements were also carried out in order to investigate the wettability of the materials. Finally, the hydrolytic degradation of the mats in buffer solution at pH 4, pH 7 and pH 10 were studied up to 50 days.

The investigation of the thermal stability up to 400 °C of Graphene Oxide (GO) and GO-silica nanoparticles (n-SiO2) composites prepared by direct mixture of GO and n-SiO2 is reported. Using Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy, Energy Dispersive X-ray analysis, Atomic Force Microscopy, Raman and Infrared absorption measurements a thorough characterization of the prepared materials is carried out. By deepening the changes induced in the 2D Raman spectral region of GO at about 2900 cm−1 the comprehension of an interplay, driven by the thermally induced changes of the material, between inter-valley and intra-valley vibrational transitions is elucidated. This result enables to find out that the major thermally induced changes are related to the GO counterpart of the nanocomposite and shows that the deposited silica nanoparticles are not interfering with the GO principal features exploiting the potentiality of nanocomposites preparation. Furthermore, silica nanoparticles are found to act as solid exfoliant agents, thus inhibiting GO lamellae re-aggregation even at high temperatures.

The present work deals with the experimental study of high performance biocomposites reinforced with optimized agave fibers, as well as the successive implementation of reliable micromechanical models that can be used at the design stage. In detail, systematical experimental analyses performed on biocomposites with epoxy or PLA matrix, have permitted to highlight that for short fibers biocomposites the reinforcing leads to a significant improvement of the matrix stiffness, whereas the particular damage mechanism based essentially on the matrix failure with consequent tensile failure of the fibers aligned with the applied load, does not allow to obtain an actual reinforcing of the matrix. Such a result is strictly related to the limited fiber stiffness, that lead to a low reinforcing of the matrixes. Consequently, as confirmed by the experimental evidence, the mechanical performance of such biocomposites is not affected significantly by the improvement of the matrix-fiber adhesion provided by the mercerization. Also, the best results are obtained by using the stiffer agave marginata fibers, extracted by simple mechanical pressing of the leafs, without any successive treatment. For long fiber biocomposites, instead, the experimental analysis has shown that for a given fiber treatment, the use of the more deformable PLA allows a better exploiting of the fiber properties, i.e. it leads always to more eco-friendly biocomposites with higher mechanical strength. Moreover, the use of the agave marginata permits to obtain biocomposites with strength higher than the biocomposites reinforced with the common agave sisalana (sisal), with improvements until to about 50%; also, the use of fibers extracted by simple leafs pressing, allows the user to obtain high performance renewable biocomposites, characterized by high stiffness and strength comparable with that obtained by using mercerized fibers. Finally, the detailed analysis of the damage mechanisms, performed also by proper 2D and 3D micrographs, has permitted to implement accurate theoretical models that allows the user accurate predictions of the mechanical performance of biocomposites reinforced with short fibers or long fibers.

Biopolymeric porous devices exhibiting graded properties can play a crucial role in several fields, such as tissue engineering or controlled drugs release. In this context, the gradient of a specific property can be achieved by developing porous laminates composed by different types of materials. This work presents for the first time a multi-phasic porous laminate based on polycaprolactone (PCL) and polylactic acid (PLA) prepared by combining melt mixing, compression molding and particle leaching. All the materials were characterized from a morphological and a mechanical point of view. The results put into evidence the possibility to tune and to predict the mechanical properties by controlling the process parameters together with geometrical features.

Nanocomposites are a new class of polymer composites that exhibit an interesting combination of chemical, physical, thermal and mechanical properties. Only small amounts of nanofiller are sufficient to generate great variations of many properties. This work focuses on the rheological behaviour of the intercalated polymer nanocomposites in shear flow. The increase of the viscosity and the more pronounced non-Newtonian behaviour is interpreted simply considering the increase of volume of the inert phase caused by the intercalation of the macromolecules. Indeed, the volume of the intercalated tactoids increases with increasing the interlayer distance. On the other hand, the interlayer distance can be correlated with the increase of the viscosity or with the more pronounced non-Newtonian behaviour. This simple method cannot be applied to exfoliated nanocomposites or when interactions between the matrix and the nanoclay occur, thus leading to a modification of the polymer chains, e.g., degradation of the matrix due to the interaction with the organo-modifier of the clay.

Polymer nanocomposites have continually attracted increasing interest over the last decade, due to significant improvements they can offer compared to neat polymer matrices. However, the final morphology of a nanocomposite, determined by several variables, can significantly influence the macroscopic properties of the final product. Therefore, it is important to study the interactions between processing, morphology, structure and rheological properties, and the suitability of existing models in order to predict the system's behaviour with change of the main processing variables. In this work, the applicability of a predictive theory based on the Wu model was formulated and proposed in order to predict the morphology of nanocomposite systems. This theory allows description of a polymer matrix - lamellar filler system, provided that the interactions between the two components and the processing are known. In particular, a lamellar filler has been considered as a deformable second component of a blend, with its behaviour depending on the processing and on the interactions with the polymer matrix. This allowed analyzing different behaviour for the systems, due to the different polarity of the matrix, which may lead to a classification of polymer nanocomposites in two or more families, according to their different matrix polarities.