1,720,973 research outputs found
Sustainable Materials Containing Biochar Particles: A Review
Full text linkThe conversion of polymer waste, food waste, and biomasses through thermochemical decomposition to fuels, syngas, and solid phase, named char/biochar particles, gives a second life to these waste materials, and this process has been widely investigated in the last two decades. The main thermochemical decomposition processes that have been explored are slow, fast, and flash pyrolysis, torrefaction, gasification, and hydrothermal liquefaction, which produce char/biochar particles that differ in their chemical and physical properties, i.e., their carbon-content, CHNOS compositions, porosity, and adsorption ability. Currently, the main proposed applications of the char/biochar particles are in the agricultural sector as fertilizers for soil retirement and water treatment, as well as use as high adsorption particles. Therefore, according to recently published papers, char/biochar particles could be successfully considered for the formulation of sustainable polymer and biopolymer-based composites. Additionally, in the last decade, these particles have also been proposed as suitable fillers for asphalts. Based on these findings, the current review gives a critical overview that highlights the advantages in using these novel particles as suitable additives and fillers, and at the same time, it shows some drawbacks in their use. Adding char/biochar particles in polymers and biopolymers significantly increases their elastic modulus, tensile strength, and flame and oxygen resistance, although composite ductility is significantly penalized. Unfortunately, due to the dark color of the char/biochar particles, all composites show brown-black coloration, and this issue limits the applications
Ecofriendly Biopolymer-Based Nanocomposite Films with Improved Photo-Oxidative Resistance
Full text linkThe interest towards high performance biopolymer-based materials increases continuously and, to guarantee appropriately industrial applications, the photo-oxidative resistance and stability of these materials must be adequately addressed. In this study, innovative biopolymer-based nanocomposites, i.e., Polyamide 11 (PA11), containing ad-hoc modified Layered Double Hydroxides (LDH), were successfully formulated and characterized. Particularly, LDH were considered carriers for hindered amine light stabilizing molecules, so two different hindered amine moieties (HALS1 and HALS2) were anchored on LDH layered internal structures and/or outer surfaces. The presence of HALS1 and HALS2 in LDH were confirmed by X-ray diffraction, spectroscopy, and thermogravimetric analysis. Then, the novel LDH-HALS nanofillers (here named LDH-HALS1 and LDH-HALS2) were introduced into a PA11 matrix by melt mixing at 5 wt.%; the produced nanocomposites were characterized by differential scanning calorimetry, rheological, and morphological analysis. All obtained results suggest that the LDH-HALS1/HALS2 nanofillers were very well dispersed into the PA11 matrix. Additionally, the photo-oxidative resistance of the PA11-based nanocomposite films was evaluated by subjecting thin films to UVB exposure and the degradation process was monitored by spectroscopic analysis over time. The photo-oxidative resistance of the PA11/LDH-HALS1/HALS2 was compared to that of PA11-based nanocomposites containing unmodified LDH and the commercial hindered amine UV-stabilizer (Cyasorb((R)) UV-3853). It was established that by anchoring the hindered amine moieties to the LDH, the PA11 nanocomposites were successfully protected against UVB exposure. This was because the hindered amine light stabilizing molecules were available to act at the critical zone where the degradation phenomena occur, which is at the interface between the matrix and the inorganic particles
A review of bioplastics and their adoption in the circular economy
Full text linkThe European Union is working towards the 2050 net-zero emissions goal and tackling the ever-growing environmental and sustainability crisis by implementing the European Green Deal. The shift towards a more sustainable society is intertwined with the production, use, and disposal of plastic in the European economy. Emissions generated by plastic production, plastic waste, littering and leakage in nature, insufficient recycling, are some of the issues addressed by the European Commission. Adoption of bioplastics–plastics that are biodegradable, bio-based, or both–is under assessment as one way to decouple society from the use of fossil resources, and to mitigate specific environmental risks related to plastic waste. In this work, we aim at reviewing the field of bioplastics, including standards and life cycle assessment studies, and discuss some of the challenges that can be currently identified with the adoption of these materials
Effect of different processing techniques and presence of antioxidant on the chitosan film performance
Full text linkIn the last two decades, the naturally occurring polysaccharides have gained great attention because of their potential applications in different sectors, for example, from food to biomedical sectors. Chitosan is a cationic polysaccharide with good transparency, and currently, it has been considered also as suitable material for the formulation film and coating in cultural heritage protection. In this work, the chitosan films (Ch), with and without natural antioxidant such as citric acid (CA), are formulated considering two different processing techniques: (i) conventional solvent casting and (ii) compression molding, that is an unconventional method for this polysaccharide, giving the possibility to formulate films with extended surface and constant thickness. The effects of processing conditions and antioxidant presence on the properties and performance are evaluated by thermo-gravimetric analysis, FTIR and UV-visible spectroscopy, water contact angle measurements and tensile test. Besides, the durability of all investigated Ch and Ch/CA has been evaluated subjecting thin film to UVB exposure and monitoring their structural changes by FTIR analysis in time. All obtained results suggest that the chitosan films can be processed successfully by both solvent casting and compression molding techniques. Further, the CA presence in Ch films has a beneficial effect on the thermal resistance and durability and no negative effect on the transparency and optical properties
Production of High Energy-Dense Solid Biofuel and Biopolymer Filler via Hydrothermal Carbonization of Carob Fruit
Full text linkIn this study fresh carob tree fruits (CF), a very widespread botanical species in the Mediterranean basin, were hydrothermally carbonized (HTC) at 200, 230, 250, and 280 °C for a residence time of 0.5 h and a biomass-to-water mass ratio (B/W) of 0.1. CF hydrochars were characterized in terms of elemental and proximate analysis for their possible valorization as solid biofuels. Increased reaction severity showed a decrease in solid mass yield recovery but an increase in hydrochar fixed carbon content and energy density. Hydrochars showed a high heating value (HHV) up to about 27.7 MJ/kg with a corresponding energy densification ratio (EDR) higher than 150%. CF hydrochars were also investigated as potential carbon-dense material as fillers in bio-plastic. Therefore, the CF hydrochar particles, at different concentrations, have been introduced in biopolymer matrices, such as PolyButylene Adipate Terephthalate (PBAT), by melt mixing and the rheological and mechanical behaviour of the bio-composites have been evaluated considering their potential application in the packaging sector
Control of end-of-life oxygen-containing groups accumulation in biopolyesters through introduction of crosslinked polysaccharide particles
Full text linkThe formulation of bio-based materials with good performance in service and controlled end-of-life is imperative for an effective circular economy. In this work, an innovative approach to induce and control the end-of-life of biodegradable polyesters through introduction of crosslinked polysaccharide particles is proposed. Chitosan (Ch) has been subjected to ionotropically crosslinking and then added to polylactic acid (PLA) at different amounts (1.0–4.0%w) by melt mixing. All obtained results suggest that the addition of crosslinked Ch (cCh) particles does not modify significantly the investigated biopolyester properties. Specifically, the thermal analysis of the composites reveals that the addition of unmodified Ch alters the PLA thermal behavior, while the addition of cCh particles does not change the PLA glass transition, cold crystallization and fusion phenomena. The infrared and UV–visible spectroscopic analyses suggest no significant changes in PLA structure. PLA/cCh films show a good optical transparency, which is a desirable property for food packaging applications. In addition, thin PLA-based films have been subjected to UVB exposure and the accumulation of oxygen-containing groups has been monitored in time through spectroscopic analysis. Interestingly, at low exposure time, the presence of chitosan slows down the accumulation of these groups, while at long exposure time, chitosan induces accelerated oxygen-groups formation, supporting its beneficial effect as end-of-life accelerant
Slow pyrolysis as a method for biochar production from carob waste: Process investigation and products’ characterization
Full text linkThe zero-waste city challenge of the modern society is inevitably addressed to the development of model’s waste-to-energy. In this work, carob waste, largely used in the agro-industrial sector for sugar extraction or locust beangum (LBG) production, is considered as feedstock for the slow pyrolysis process. According to the Food and Agriculture Organization of the United Nations (FAO), in 2012, the world production of carobs was ca. 160,000 tons, mainly concentrated in the Mediterranean area (Spain, Italy, Morocco, Portugal, and Greece). To evaluate the biomass composition, at first, the carob waste was subjected to thermo-gravimetric analysis. The high content of fixed carbon suggests that carobs are a plausible candidate for pyrolysis conversion to biochar particles. The thermal degradation of the carob waste proceeds by four different steps related to the water and volatile substances’ removal, degradation of hemicellulose, lignin and cellulose degradation, and lignin decomposition. Considering this, the slow pyrolysis was carried out at three different temperatures, specifically, at 280, 340, and 400◦C, and the obtained products were characterized. Varying the processing temperature, the proportion of individual products’ changes with a reduction in the solid phase and an increase in liquid and gas phases, with an increase in the pyrolysis temperature. The obtained results suggest that carob waste can be considered a suitable feedstock for biochar production, rather than for fuels’ recovery
Durability and performance of sustainable composite films from aliphatic-aromatic polyester with biomass-derived carbon-based filler particles
Full text linkAdditives are known to improve the properties of biopolymers, but most additives have environmental or performance concerns that limit their use. In this context, the recovery and use of bio-waste and biomass for the formulation of sustainable bio-composites is a challenging issue for the transition from a linear to a more sustainable circular economy. Recently, the replacement of carbon-based fillers in polymers and biopolymers with biochar particles derived from thermochemical treatments of biomass waste has attracted increasing attention for its potentially critical role.In this work, sustainable bio-composites based on biodegradable poly(butylene adipate-co-terephthalate), PBAT, and biochar, produced by controlled thermochemical treatments of biomass waste, were prepared by melt blending and their durability and performance were investigated in detail. Firstly, carob waste, after syrup extraction, was subjected to dry and wet thermochemical processes, i.e. slow pyrolysis at 280, 340 and 400 degrees C and hydrothermal carbonisation at 220, 250 and 280 degrees C, to obtain slow pyrolyzed biochar (SP-BC) and hydrothermal carbonised biochar (HTC-BC) particles. The SP-BC and HTC-BC, i.e. the solid phases resulting from the thermochemical processes, were characterised by elemental analysis and spectroscopy to study their physicochemical properties and by microscopy to analyse their morphology. Pure PBAT, PBAT/SP-BC and PBAT/HTC-BC bio-composites containing 10 % by weight of SP-BC and HTC-BC respectively were characterised by thermal, morphological, rheological and mechanical analyses. The results indicate that both types of particles exerted a reinforcing effect on PBAT and the resulting bio-composites were more thermo-mechanically stable compared to pure PBAT. Considering the potential application of these bio-composites as sustainable packaging materials, particular attention was paid to the photo-oxidation behaviour of these materials under accelerated artificial weathering conditions. Interestingly, both SP-BC and HTC-BC exerted a protective effect against the photooxidative ageing of PBAT, and this effect was more pronounced when HTC-BC was used
Understanding the effects of crosslinking and reinforcement agents on the performance and durability of biopolymer films for cultural heritage protection
Full text linkIn the last two decades, the naturally occurring polysaccharides, such as chitosan and pectin, have gained great attention having potential applications in different sectors, from biomedical to new generation packaging. Currently, the chitosan and pectic have been proposed as suitable materials also for the formulation of films and coatings for cultural heritage protection, as well as packaging films. Therefore, the formulation of biopolymer films, considering only naturally occurring polymers and additives, is a current challenging trend. This work reports on the formulation of chitosan (CS), pectin (PC), and chitosan:pectin (CS:PC) films, also containing natural crosslinking and reinforcement agents, such as citric acid (CA) and halloysite nanotubes (HNT), through the solvent casting technique. The produced films are characterized through water contact angle measurements, infrared and UV–visible spectroscopy and tensile test, while the durability of the CS:PC films is evaluated subjecting the film to accelerated UVB exposure and monitoring the photo‐oxidation degradation in time though infrared spectroscopy. All obtained results suggest that both crosslinking and reinforcement agents have beneficial effects on the wettability, rigidity, and photo‐oxidation resistance of biopolymer films. Therefore, these biopolymer films, also containing naturally occurring additives, have good properties and performance and they are suitable as coverage films for cultural heritage protection
Bionanocomposite films containing halloysite nanotubes and natural antioxidants with enhanced performance and durability as promising materials for cultural heritage protection
Full text linkIn the last decade, the interest toward the formulation of polymer films for cultural heritage protection continuously grew, and these films must be imperatively transparent, removable, and should not react/interact with surface of the artworks. In this research, bionanocomposite films, based on chitosan (Ch) and pectin (P) and containing naturally occurring fillers and antioxidants, were formulated by solvent casting methods and were accurately characterized. The natural halloysite nanotubes (HNT) have a two-fold role, specifically, physical compatibilizer and antioxidant carrier. Therefore, the theoretical solubility between Ch and P was estimated considering Hoy's method for solubility of polymers, while the optimum ratio between biopolymer constituents was assessed by ζ-potential measurements. The transparency, wettability, and mechanical behavior of Ch:P films, also in presence of HNT without and with antioxidants, were investigated. The beneficial effects of natural antioxidants, such as vanillic acid (VA) and quercetin (Q), on Ch:P/HNT durability were found
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