Bio-Composite Filaments Based on Poly(Lactic Acid) and Cocoa Bean Shell Waste for Fused Filament Fabrication (FFF): Production, Characterization and 3D Printing.

In this study, novel biocomposite filaments incorporating cocoa bean shell waste (CBSW) and poly(lactic acid) (PLA) were formulated for application in Fused Filament Fabrication (FFF) technology. CBSW, obtained from discarded chocolate processing remnants, was blended with PLA at concentrations of 5 and 10 wt.% to address the challenge of waste material disposal while offering eco-friendly composite biofilaments for FFF, thereby promoting resource conservation and supporting circular economy initiatives. A comprehensive analysis encompassing structural, morphological, thermal, and mechanical assessments of both raw materials and resultant products (filaments and 3D printed bars) was conducted. The findings reveal the presence of filler aggregates only in high concentrations of CBSW. However, no significant morphological or thermal changes were observed at either CBSW concentration (5 wt.% and 10 wt.%) and satisfactory printability was achieved. In addition, tensile tests on the 3D printed objects showed improved stiffness and load resistance in these samples at the highest CBSW concentrations. In addition, to demonstrate their practical application, several 3D prototypes (chocolate-shaped objects) were printed for presentation in the company's shop window as a chocolate alternative; while retaining the sensory properties of the original cocoa, the mechanical properties were improved compared to the base raw material. Future research will focus on evaluating indicators relevant to the preservation of the biocomposite's sensory properties and longevity.

Thermochromic Printable and Multicolor Polymeric Composite Based on Hybrid Organic-Inorganic Perovskite.

Hybrid organic-inorganic perovskites (PVKs) are among the most promising materials for optoelectronic applications thanks to their outstanding photophysical properties and easy synthesis. Herein, a new PVK-based thermochromic composite is demonstrated. It can reversibly switch from a transparent state (transmittance > 80%) at room temperature to a colored state (transmittance < 10%) at high temperature, with very fast kinetics, taking only a few seconds to go from the bleached to the colored state (and vice versa). X-ray diffraction, Fourier-transform infrared spectroscopy, differential scanning calometry, rheological, and optical measurements carried out during heating/cooling cycles reveal that thermochromism in the material is based on a reversible process of PVK disassembly/assembly mediated by intercalating polymeric chains, through the formation and breaking of hydrogen bonds between polymer and perovskite. Therefore, differently from other thermochromic perovskites, that generally work with the adsorption/desorption of volatile molecules, the system is able to perform several heating/cooling cycles regardless of environmental conditions. The color and transition temperature (from 70 to 120 °C) can be tuned depending on the type of perovskite. Moreover, this thermochromic material is printable and can be deposited by cheap techniques, paving the way for a new class of smart coatings with an unprecedented range of colors.

Fused Filament Fabrication and Computer Numerical Control Milling in Cultural Heritage Conservation.

This paper reports a comparison between the advantages and disadvantages of fused filament fabrication (FFF) and computer numerical control (CNC) milling, when applied to a specific case of conservation of cultural heritage: the reproduction of four missing columns of a 17th-century tabernacle. To make the replica prototypes, European pine wood (the original material) was used for CNC milling, while polyethylene terephthalate glycol (PETG) was used for FFF printing. Neat materials were chemically and structurally characterized (FTIR, XRD, DSC, contact angle measurement, colorimetry, and bending tests) before and after artificial aging, in order to study their durability. The comparison showed that although both materials are subject to a decrease in crystallinity (an increase in amorphous bands in XRD diffractograms) and mechanical performance with aging, these characteristics are less evident in PETG (E = 1.13 ± 0.01 GPa and σ = 60.20 ± 2.11 MPa after aging), which retains water repellent (ca = 95.96 ± 5.56°) and colorimetric (∆E = 2.6) properties. Furthermore, the increase in flexural strain (%) in pine wood, from 3.71 ± 0.03% to 4.11 ± 0.02%, makes it not suitable for purpose. Both techniques were then used to produce the same column, showing that for this specific application CNC milling is quicker than FFF, but, at the same time, it is also much more expensive and produces a huge amount of waste material compared to FFF printing. Based on these results, it was assessed that FFF is more suitable for the replication of the specific column. For this reason, only the 3D-printed PETG column was used for the subsequent conservative restoration.

Hydrophobic, Mechanical, and Physical Properties of Polyurethane Nanocomposite: Synergistic Impact of Mg(OH)2 and SiO2.

Polyurethane (PU) is one of the most well-known polymer coatings because of its favorable characteristics, which include its low density, nontoxicity, nonflammability, longevity, adhesion, simple manufacture, flexibility, and hardness. However, PU does come with several major drawbacks, among which are poor mechanical properties as well as low thermal and chemical stability, particularly in the high-temperature mode, where becomes gets flammable and loses adhesion ability. The limitations have inspired researchers to develop a PU composite to improve the weaknesses by adding different reinforcements. Magnesium hydroxide, having the ability to be produced with exceptional properties such as flammability, has consistently attracted the interest of researchers. Additionally, silica nanoparticles with high strength and hardness are one of the excellent reinforcements of polymers these days. The hydrophobic, physical, and mechanical properties of pure polyurethane and the composite type (nano, micro, and hybrid) fabricated with the drop casting method were examined in this study. 3-Aminopropyl triethoxysilane was applied as a functionalized agent. To confirm that hydrophilic particles turned into hydrophobic, FTIR analysis was carried out. The impact of size, percentage, and kind of fillers on different properties of PU/Mg(OH)2-SiO2 was then investigated using different analyses including spectroscopy and mechanical and hydrophobicity tests. The resultant observations demonstrated that different surface topographies can be obtained from the presence of particles of different sizes and percentages on the hybrid composite's surface. Surface roughness allowed for exceptionally high water contact angles, which confirmed the hybrid polymer coatings' superhydrophobic properties. According to the particle size and content, the distribution of fillers in the matrix also improved the mechanical properties.

From Virtual Reconstruction to Additive Manufacturing: Application of Advanced Technologies for the Integration of a 17th-Century Wooden Ciborium.

3D modelling and 3D printing techniques have become increasingly popular in different fields, including cultural heritage. In this field, there are still many challenges to overcome, such as the difficulty of faithfully reproducing complex geometries or finding materials suitable for restoration, due to the limited scientific studies. This work proposes an example of the application of advanced technologies for the reproduction of four missing columns of a 17th century polychrome wooden ciborium. The difficulties of an automatic scan due to its reflective surface (water gilding and estofado decorations) were overcome by creating a 2D manual survey and a subsequent manual 3D redrawing. The CAD model was used to print the missing elements with fused filament fabrication (FFF) in polyethylene terephthalate glycol (PETG), using the following printing parameters: nozzle 0.4 mm, infill 20%, extrusion temperature of PLA 200 °C and of PETG 220 °C, plate temperature 50 °C, printing speed 60 mm/s, layer height 0.2 mm. The conservation and restoration of the ciborium is nearing completion. This study highlights the importance of collaboration between different professionals for the correct design of a restoration, as well as the need to promote scientific research into the development of new high-performance 3D printing materials suitable for conservation.

Novel Synthesis of Nano Mg(OH)2 by Means of Hydrothermal Method with Different Surfactants.

Magnesium hydroxide (MOH) is a widely used inorganic chemical owing to its various properties. Hence, researchers have long studied its synthesis and its unique features. However, the morphological consequences have rarely been studied. Despite having several benefits for synthesizing nanoparticles, the hydrothermal method's main drawbacks are its lengthy processing time and the high cost of raw materials. This research aimed to use more easily obtainable raw materials in a reasonably short time to synthesize MOH in various morphologies. For this purpose, we prepared different samples using the same hydrothermal method to investigate the effects of the precursor and surfactant on the structure, morphology, and size of MOH particles. The results of XRD and FTIR analysis demonstrated that a temperature of 180 °C and a duration of 18 h is not sufficient for MgO as a precursor to obtaining MOH in the hydrothermal method. However, in the presence of different surfactants, MgCl2 resulted in nanoparticles with hexagonal structure and plate, flake, spherical, and disc morphologies.

The Role of 3D Printing in the Development of a Catalytic System for the Heterogeneous Fenton Process.

Recycling of catalysts is often performed. Additive manufacturing (AM) received increasing attention in recent years in various fields such as engineering and medicine, among others. More recently, the fabrication of three-dimensional objects used as scaffolds in heterogeneous catalysis has shown innumerable advantages, such as easier handling and waste reduction, both leading to a reduction in times and costs. In this work, the fabrication and use of 3D-printed recyclable polylactic acid (PLA) scaffolds coated with an iron oxide active catalyst for Fenton reactions applied to aromatic model molecules, is presented. These molecules are representative of a wider class of intractable organic compounds, often present in industrial wastewater. The 3D-printed PLA-coated scaffolds were also tested using an industrial wastewater, determining the chemical oxygen demand (COD). The catalyst is characterized using electron microscopy coupled to elemental analysis (SEM/EDX) and thermogravimetry, demonstrating that coating leach is very limited, and it can be easily recovered and reused many times.

An Overview on Wood Waste Valorization as Biopolymers and Biocomposites: Definition, Classification, Production, Properties and Applications.

Bio-based polymers, obtained from natural biomass, are nowadays considered good candidates for the replacement of traditional fossil-derived plastics. The need for substituting traditional synthetic plastics is mainly driven by many concerns about their detrimental effects on the environment and human health. The most innovative way to produce bioplastics involves the use of raw materials derived from wastes. Raw materials are of vital importance for human and animal health and due to their economic and environmental benefits. Among these, wood waste is gaining popularity as an innovative raw material for biopolymer manufacturing. On the other hand, the use of wastes as a source to produce biopolymers and biocomposites is still under development and the processing methods are currently being studied in order to reach a high reproducibility and thus increase the yield of production. This study therefore aimed to cover the current developments in the classification, manufacturing, performances and fields of application of bio-based polymers, especially focusing on wood waste sources. The work was carried out using both a descriptive and an analytical methodology: first, a description of the state of art as it exists at present was reported, then the available information was analyzed to make a critical evaluation of the results. A second way to employ wood scraps involves their use as bio-reinforcements for composites; therefore, the increase in the mechanical response obtained by the addition of wood waste in different bio-based matrices was explored in this work. Results showed an increase in Young's modulus up to 9 GPa for wood-reinforced PLA and up to 6 GPa for wood-reinforced PHA.

Sustainable Polymer Composites Manufacturing through 3D Printing Technologies by Using Recycled Polymer and Filler.

In the last years, the excessive use of plastic and other synthetic materials, that are generally difficult to dispose of, has caused growing ecological worries. These are contributing to redirecting the world's attention to sustainable materials and a circular economy (CE) approach using recycling routes. In this work, bio-filaments for the Fused Filament Fabrication (FFF) 3D printing technique were produced from recycled polylactic acid (PLA) and artisanal ceramic waste by an extrusion process and fully characterized from a physical, thermal, and mechanical point of view. The data showed different morphological, thermal, rheological, and mechanical properties of the two produced filaments. Furthermore, the 3D objects produced from the 100% recycled PLA filament showed lower mechanical performance. However, the results have demonstrated that all the produced filaments can be used in a low-cost FFF commercial printer that has been modified with simple hand-made operations in order to produce 3D-printed models. The main objective of this work is to propose an example of easy and low-cost application of 3D printing that involves operations such as the reprocessing and the recyclability of materials, that are also not perfectly mechanically performing but can still provide environmental and economic benefits.

Historically Accurate Reconstruction of the Materials and Conservation Technologies Used on the Facades of the Artistic Buildings in Lecce (Apulia, Italy).

The protection of the stone surfaces of the buildings of the city of Lecce (Apulia, Italy) represents an ancient practice, which has always allowed the conservation of the historical-artistic heritage of the city, which nowadays is an international touristic and cultural destination. The identification of ancient recipes, materials and methodologies for the protection of historical buildings plays an important role in establishing correct protocols in order to ensure the durability of stone surfaces over time. This work presents a historically accurate reconstruction of the materials and conservation technologies used on the facades of the artistic buildings in Lecce. Several historical buildings, both civil and religious, have been selected in order to investigate the treatments applied on their facades and to know the traditions spread in the past in the field of building conservation in the Salento territory. Thanks to non-invasive or micro-destructive techniques (optical microscopy, ATR-FTIR spectroscopy, pyrolysis-gas chromatography-mass spectrometry), the characteristic molecular markers of the materials and the products of degradation have been identified, deepening the knowledge of the mechanisms of deterioration and interaction between the stone material, the surface finish and the surrounding environment. The paper is a valuable tool for the knowledge of ancient traditions and the planning of proper restoration works.

A Review of Polymer-Based Materials for Fused Filament Fabrication (FFF): Focus on Sustainability and Recycled Materials.

Recently, Fused Filament Fabrication (FFF), one of the most encouraging additive manufacturing (AM) techniques, has fascinated great attention. Although FFF is growing into a manufacturing device with considerable technological and material innovations, there still is a challenge to convert FFF-printed prototypes into functional objects for industrial applications. Polymer components manufactured by FFF process possess, in fact, low and anisotropic mechanical properties, compared to the same parts, obtained by using traditional building methods. The poor mechanical properties of the FFF-printed objects could be attributed to the weak interlayer bond interface that develops during the layer deposition process and to the commercial thermoplastic materials used. In order to increase the final properties of the 3D printed models, several polymer-based composites and nanocomposites have been proposed for FFF process. However, even if the mechanical properties greatly increase, these materials are not all biodegradable. Consequently, their waste disposal represents an important issue that needs an urgent solution. Several scientific researchers have therefore moved towards the development of natural or recyclable materials for FFF techniques. This review details current progress on innovative green materials for FFF, referring to all kinds of possible industrial applications, and in particular to the field of Cultural Heritage.

Fully Recyclable Bio-Based Epoxy Formulations Using Epoxidized Precursors from Waste Flour: Thermal and Mechanical Characterization.

Organic wastes represent an increasing pollution problem due to the exponential growth of their presence in the waste stream. Among these, waste flour cannot be easily reused by transforming it into high-value-added products. Another major problem is represented by epoxy-based thermosets, which have wide use but also poor recyclability. The object of the present paper is, therefore, to analyze both of these problems and come up with innovative solutions. Indeed, we propose a completely new approach, aimed at reusing the organic waste flour, by converting it into high-value epoxy-based thermosets that could be fully recycled into a reusable plastic matrix when added to the waste epoxy-based thermosets. Throughout the research activity, the organic waste was transformed into an epoxidized prepolymer, which was then mixed with a bio-based monomer cured with a cleavable ammine. The latter reactant was based on Recyclamine™ by Connora Technologies, and in this paper, we demonstrate that this original approach could work with the synthetized epoxy prepolymers derived from the waste flour. The cured epoxies were fully characterized in terms of their thermal, rheological, and flexural properties. The results obtained showed optimal recyclability of the new resin developed.

Recent Applications of Biopolymers Derived from Fish Industry Waste in Food Packaging.

Fish waste is attracting growing interest as a new raw material for biopolymer production in different application fields, mainly in food packaging, with significant economic and environmental advantages. This review paper summarizes the recent advances in the valorization of fish waste for the preparation of biopolymers for food packaging applications. The issues related to fishery industry waste and fish by-catch and the potential for re-using these by-products in a circular economy approach have been presented in detail. Then, all the biopolymer typologies derived from fish waste with potential applications in food packaging, such as muscle proteins, collagen, gelatin, chitin/chitosan, have been described. For each of them, the recent applications in food packaging, in the last five years, have been overviewed with an emphasis on smart packaging applications. Despite the huge industrial potential of fish industry by-products, most of the reviewed applications are still at lab-scale. Therefore, the technological challenges for a reliable exploitation and recovery of several potentially valuable molecules and the strategies to improve the barrier, mechanical and thermal performance of each kind of biopolymer have been analyzed.

Implication of polymeric template agent on the formation process of hybrid halide perovskite films.

The use of polymeric additives supporting the growth of hybrid halide perovskites has proven to be a successful approach aiming at high quality active layers targeting optoelectronic exploitation. A detailed description of the complex process involving the self-assembly of the precursors into the perovskite crystallites in presence of the polymer is, however, still missing. Here we take starch:CH3NH3PbI3 (MAPbI3) as example of highly performing composite, both in solar cells and light emitting diodes, and study the film formation process through differential scanning calorimetry and in situ time-resolved grazing incidence wide-angle x-ray scattering, performed during spin coating. These measurements reveal that starch beneficially influences the nucleation and growth of the perovskite precursor phase, leading to improved structural properties of the resulting film which turns into higher stability towards environmental conditions.

Transport Properties of Natural and Artificial Smart Fabrics Impregnated by Graphite Nanomaterial Stacks.

In this work, we studied the transport properties (thermal and electrical conductivity) of smart fabric materials treated with graphite nanomaterial stacks-acetone suspensions. An innovative and easy method to produce graphite nanomaterial stacks-acetone-based formulations, starting from a low-cost expandable graphite, is proposed. An original, economical, fast, and easy method to increase the thermal and electrical conductivity of textile materials was also employed for the first time. The proposed method allows the impregnation of smart fabric materials, avoiding pre-coating of the fibers, thus reducing costs and processing time, while obtaining a great increase in the transport properties. Two kinds of textiles, cotton and Lycra®, were selected as they represent the most used natural and artificial fabrics, respectively. The impact of the dimensions of the produced graphite nanomaterial stacks-acetone-based suspensions on both the uniformity of the treatment and the transport properties of the selected textile materials was accurately evaluated using several experimental techniques. An empirical relationship between the two transport properties was also successfully identified. Finally, several theoretical models were applied to predict the transport properties of the developed smart fabric materials, evidencing a good agreement with the experimental data.

Development of an Innovative and Green Method to Obtain Nanoparticles in Aqueous Solution from Carbon-Based Waste Ashes.

In this study, an original and green procedure to produce water-based solutions containing nanometric recycled carbon particles is proposed. The nanometric particles are obtained starting from carbon waste ashes, produced by the wooden biomass pyro-gasification plant CMD (Costruzioni motori diesel) ECO20. The latter is an integrated system combining a downdraft gasifier, a spark-ignition internal combustion engine, an electric generator and syngas cleaning devices, and it can produce electric and thermal power up to 20 kWe and 40 kWth. The carbon-based ashes (CA) produced by the CMD ECO20 plant were, first, characterized by using differential scanning calorimetry (DSC) and microcomputed tomography (microCT). Afterward, they were reduced in powder by using a milling mortar and analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectrometry, thermogravimetric analysis (TGA), X-ray diffraction (WAXD) and Fourier-transform infrared (FTIR) spectroscopy. The optimization of an original procedure to reduce the dimensions of the ashes in an aqueous solution was then developed by using ball milling and sonication techniques, and the nanometric dimensions of the particles dispersed in water were estimated by dynamic light scattering (DLS) measurements in the order of 300 nm. Finally, possible industrial applications for the nanomaterials obtained from the waste ashes are suggested, including, for example, inks for Aerosol Jet® Printing (AJ® P).

Optimizing Flame Retardancy and Durability of Melamine-Formaldehyde/Solid-Urban-Waste Composite Panels.

In our previous study, an innovative method for sterilization, inertization, and valorization of the organic fraction of municipal solid waste (OFMSW), to be recycled in the production of composite panels, was developed. In this follow-up work, the effects of fire retardants on fire performance, durability, and the mechanical properties of the composite panels based on OFMSW and melamine-formaldehyde resin were investigated. The performance of panels without fire retardants (control panels) was compared to panels containing either mono-ammonium phosphate (PFR) or aluminium trihydrate (ATH) at a mass fraction of 1% and 10% (modified panels). As shown by cone calorimetry, the total heat released was already low (about 31 MJ/m2 at 50 kW/m2) in the control panels, further decreased in the modified panels with the addition of fire retardants, and reached the lowest value (about 1.4 MJ/m2) with 10% mass fraction of PFR. Hence, the addition of fire retardants had a beneficial effect on the response to fire of the panels; however, it also reduced the mechanical properties of the panels as measured by flexural tests. The deterioration of the mechanical properties was particularly obvious in panels containing 10% mass fraction of fire retardants, and they were further degraded by artificial accelerated weathering, carried out by boiling tests. Ultimately, the panels containing PFR at a mass fraction of 1% offered the best balance of fire resistance, durability, and mechanical performance within the formulations investigated in this study.

Robust, High-Performing Maize-Perovskite-Based Solar Cells with Improved Stability.

Herein, we focus on improving the long-term chemical and thermomechanical stability of perovskite solar cells (PSCs), two major challenges currently limiting their commercial deployment. Our strategy incorporates a long-chain starch polymer into the perovskite precursor. The starch polymer confers multiple beneficial effects by forming hydrogen bonds with the methylammonium iodide precursor, templating perovskite growth that results in a compact and homogeneous film deposited in a simple one-step coating (antisolvent-free). The inclusion of starch in the methylammonium lead iodide films strongly improves their thermomechanical and environmental stability while maintaining a high photovoltaic performance. The fracture energy (G c) of the film is increased to above 5 J/m2 by creating a nanocomposite that provides intrinsic reinforcement at grain boundaries. Additionally, improved optoelectronic properties achieved with the starch polymer enable good photostability of the active layer and enhanced resistance to thermal cycling.

3D Printing of Polymer Waste for Improving People's Awareness about Marine Litter.

This work is aimed at proposing demonstrative actions devoted to show reprocessing and recyclability of PET originating from bottles collected from the seaside, in order to increase the consumer awareness on the importance of recycling plastics. To this purpose, collected bottles were washed, cut, grinded, extruded in the form of a thin wire adopting different cooling rates, which leads to a modulation of the crystallinity content. Once having optimized the processing parameters, the extruded wire was used to produce 3D printed samples through the fused deposition modelling (FDM). The changes in the crystalline structure due to the different processing conditions were assessed by DSC and XRD analyses, while rheological tests were performed in order to evaluate any modification in the viscosity of PET after repeated processing cycles. The reduction in thermal stability was confirmed by TGA analysis, which showed a progressive decrease in the degradation temperature as processing cycles increased. Finally, tensile tests highlighted the difference in the mechanical response due to the predominance of the crystalline or amorphous phase in the tested sample. In particular, a good mechanical behavior was found for the 3D-printed samples.

An Innovative Method for the Recycling of Waste Carbohydrate-Based Flours.

This work represents an innovative study that, for the first time, explores the possibility to use waste flours to produce thermoplastic polymeric bio-films. To the best of our knowledge, this is the first time that waste flours, derived from bakeries, pizzerias or pasta factories, have been proposed for the production of bio-polymers, as a replacement of neat starch. To this aim, durum waste flour derived from a pasta factory, soft waste flour derived from pizzerias and neat maize starch used as control material were firstly analyzed from dimensional, morphological and chemical points of view. Afterwards, waste flour films were produced by the addition of a nature-based plasticizer, glycerol. Mechanical characterization of the plasticized thermoplastic films, produced by compression molding, evidenced low performances, even in the case of the neat maize starch. In order to improve the mechanical properties, the possibility to include polylactic acid and cardanol-based plasticizer was also investigated. Mass transport properties of all the produced bio-films were investigated by measuring their water vapor permeability and hygroscopic absorption. The durability properties of the bio-films were assessed by accelerated ageing tests, while the bio-degradability of the waste-based films was evaluated by measuring the solubility and the degradation in water. The physicochemical analyses of the novel bio-films evidenced good mechanical properties; specifically, the waste-based films showed a lower hygroscopic absorption and water solubility than those of the blends containing neat starch.