Over the last years, the trend associated with the incorporation of materials from renewable resources into polymer technology is getting significantly more vital. Researchers are trying to transfer the properties of natural raw materials into the polymer world. Therefore, different natural materials are more often investigated as potential additives for polymers. Such an effect is noted for the coffee industry byproducts, such as coffee silverskin. Because of the relatively high contents of compounds showing antioxidant activity, such as caffeine, polyphenols, tannins, or melanoidins, this byproduct could be considered not only as a filler, but also as a potential modifier for polymer materials. Its antioxidant activity is comparable to commercially available antioxidants applied in polymer technology. Therefore, in the presented paper, we examined the influence of the coffee silverskin (from 1 to 20 wt %) on the thermal and mechanical performance of polyethylene-based composites. Moreover, materials were subjected to accelerated aging tests in the UV chamber, which revealed that coffee silverskin could inhibit the photodegradation of the polymer matrix. Therefore, this byproduct should be considered as an exciting alternative for the conventional lignocellulosic fillers, which could provide additional features to polymer composites. Full article

Polymers are extensively used as advanced materials. The most commonly used polymers in industry are non-biodegradable and petroleum derived. The increasing demand for these types of polymers results in a problem of accumulation of plastic waste in the environment and depletion of fossil resources. Because of this point, the biodegradability of polymers gains great importance as well as for the bio-based polymers produced from renewable resources. In this study, bio-based polyamide 5.6 polymer (PA56) was incorporated with olive stone powder (OSP) in order to manufacture a biodegradable polyamide compound, and its degradability was investigated. The olive stone powder was incorporated into polyamide 5.6 at 10% (w/w) with a twin-screw extruder to manufacture the compound, PA56/OSP10. The characterization of the PA56/OSP10 compound was conducted using Fourier transform infrared (FTIR) spectroscopy. The biodegradability of the PA56/OSP10 compound was examined by a natural soil burial test of six months duration. The signs of degradation were assessed by both weight loss measurements and visual observations. At the end of six months, 5.24% weight loss and surface deformation were determined for the PA56/OSP10 compound. These results suggest that olive stone powder can be considered as a green alternative to conventional biodegradation additives for polymer compounding. Full article

Nowadays, polymers used in technical applications are still obtained from petrochemicals, despite the more critical reviews from society. In this work, novel nanodielectrics based on renewable resources were developed. For this purpose, poly(2-oxazoline)s (POx), which can be referred to as pseudo-polyamides, were synthesized from renewable resources and compared with commercially available Nylon 12, which is derived from petrochemicals. The monomers 2-nonyl-2-oxazoline and 2-dec-9′-enyl-2-oxazoline were synthesized from coconut oil and castor oil in solvent-free syntheses according to the Henkel Patent; the corresponding copoly(2-oxazoline)s were synthesized in an energy-efficient fashion in microwave reactors under autoclave conditions. Both types of polyamides (two variations: POx and Nylon 12) were filled with inorganic nanoparticles (four variations: no filler, submicro-scaled BN, nano- and micro-scaled AlN as well as a mixture of nano- and micro-scaled AlN and submicro-scaled BN) and/or expanding monomers, namely spiroorthoesters (three variations: 0, 15, and 30 wt.-%), yielding a 2 × 4 × 3 = 24-membered material library. All polymers were crosslinked according to a newly developed thermally-initiated dual/bi-stage curing system. Intense physicochemical and dielectric characterization revealed that the relative volume expansion was in the range of 0.46 to 2.48 vol.-% for the Nylon 12 samples and in the range of 1.39 to 7.69 vol.-% for the POx samples. Hence, the formation micro-cracks or micro-voids during curing is significantly reduced. The dielectric measurements show competitive dielectric behavior of the “green” POx samples in comparison with the fossil-based Nylon 12 samples at a frequency of 40 Hz. Full article

Problems associated with microbial resistance to antibiotics are growing due to their overuse. In this scenario, plant extracts such as the propolis extract (PE) have been considered as potential alternatives to antibiotics in the treatment of infected wounds, due to its antimicrobial properties and ability to induce tissue regeneration. To improve the long-term effectiveness of PE in wound healing, polymeric films composed of biodegradable and biocompatible polymers are being engineered as delivery vehicles. Here, sodium alginate/gelatin (SA/GN) films containing PE were prepared via a simple, green process of solvent casting/phase inversion technique, followed by crosslinking with calcium chloride (CaCl₂) solutions. The minimum inhibitory concentration (MIC) of PE was established as 0.338 mg/mL for Staphylococcus aureus and 1.353 mg/mL for Pseudomonas aeruginosa, the most prevalent bacteria in infected wounds. The PE was incorporated within the polymeric films before (blended with the polymeric solution) and after (immobilization via physisorption) their production. Flexible, highly hydrated SA/GN/PE films were obtained, and their antibacterial activity was assessed via agar diffusion and killing time kinetics examinations. Data confirmed the modified films effectiveness to fight bacterial infections caused by S. aureus and P. aeruginosa and their ability to be applied in the treatment of infected wounds. Full article

Bio-based plastics, i.e., non-synthetic polymers produced from renewable resources are gaining special attention as a feasible solution to the environmental issues caused by concerns regarding the impact of waste plastics. Furthermore, such materials can also represent an alternative to petroleum-derived polymers, due to the scarcity of this raw material in the near future. In the polyhydroxyalkanoates (PHA) family, polyhydroxybutyrate (PHB) was the first to be synthesized and characterized. PHB soon gained great attention from industrial and academic researchers since it can be synthesized from a wide variety of available carbon sources, such as agro-industrial and domestic wastes. The aim of this original research has been the identification of the presence of PHB synthetizing bacteria in some soils in a Moroccan region and the production of the bio-based PHB. In particular, the soils of the argan fields in Taroudant were considered. Taroudant is a southwestern region of Morocco where the argan oil tree Argania spinosa is an endemic and preserved species. Starting from rhizospheric soil samples of an argan crop area, we isolated heat-resistant bacteria and obtained pure cultures from it. These bacteria present intracellular endospores stained by the Schaeffer-Fulton method. The presence of intracellular endospores is a very important starting point to verify the effective production of PHB as a compartmentalized material. Further analyses are currently ongoing to try to extract and characterize PHB granules. Full article

Polylactic acid (PLA) belongs to the few thermoplastic polymers that are derived from renewable resources such as corn starch or sugar cane. PLA is often used in 3D printing by fused deposition modeling (FDM) since it is relatively easy to print, does not show warping, and can be printed without a closed building chamber. On the other hand, PLA has interesting mechanical properties which are influenced by the printing parameters and geometries. Here we present shape-memory properties of PLA cubes with different infill patterns and percentages. We investigate the material response under defined quasi-static load as well as the possibility to restore the original 3D printed shape. The quasi-static flexural properties are linked to the porosity and the infill structure of the samples under investigation, examined optically and by simulations. Our results underline the importance of designing the infill patterns carefully to develop samples with desired mechanical properties. Full article

Worn car tires are disruptive waste, and the issue of their management is crucial for the natural environment. In many countries, the primary method of end-of-life tire utilization is energy recovery. However, more effective and beneficial for the environment is material recycling. Using them for the production of polymer–rubber composites seems to be an auspicious direction of research. Incorporation of ground tire rubber into a polyurethane matrix should be considered as a method of waste rubber utilization. Moreover, it could significantly reduce the use of petroleum-based polyols and isocyanates, which are commonly considered toxic chemicals. Therefore, the total impact on the environment could be noticeably reduced, which should be considered a very beneficial step towards more “green” polymer composites. This work aims to summarize the literature reports related to foamed polyurethane/ground tire rubber composites. It particularly emphasizes the need for compatibilization of these materials by the enhancement of interfacial interactions between the polyurethane matrix and rubber filler phase, which significantly affects the performance properties of prepared materials. As an example, we present our research results. In addition, future trends and limitations related to this type of composite material are underlined. Full article

The objective of this work is the development of a methodology to determine the useful life based on the storage temperature of NBR O-rings using a reliability-based approach that allows one to predict the use suitability at different supposed storage scenarios (that involve different storage time and temperature) considering the further required in-service performance. Thus, experimental measurements of Shore A hardness have been correlated with storage variables. From the study, it has been verified that for any of the analysis scenarios, the limit established criterion is above the storage time premise considered in the usual nuclear industry practices. Full article

The recycling of waste tires is a significant environmental and economic issue. One of the leading recycling routes is the shredding of tires, resulting in the generation of ground tire rubber. This material can be easily introduced into various polymer matrices as a filler, reducing the use of conventionally applied petroleum-based materials. In such cases, it is essential to ensure sufficient interfacial compatibility, which can be achieved by the proper modification of the rubber surface. Different treatments of ground tire rubber aim to activate its surface and introduce functional groups, providing the possibility for interfacial interactions and the incorporation of significant amounts of recycled material. Therefore, in the presented paper, we examined the impact of thermo-mechanical treatment in a twin-screw extruder on the appearance and chemical structure of ground tire rubber. Moreover, for each set of process parameters, the specific mechanical energy required for processing was calculated, providing essential insights for the potential industrial application of the analyzed process. The energy demand should be considered as a very important issue during the development of “greener” processes and materials. Full article

Corn zein protein is a cheap, widely available biopolymer that is easily extracted from corn and processed into useful forms. In this study, zein was dissolved along with several model drugs or sodium citrate, which was then cast into thin films or air-spun into nanofibers. The molecular weight, solubility, and charge of the selected model drugs are different, and the weight percentage of citrate also varies (1%–30%). The integrity of the loaded biomaterials was characterized through FTIR, SEM, DSC, and TGA. Due to the high surface-area-to-volume ratio of nanofibers, FTIR analysis showed that the therapeutics strongly interacted with the protein structure of zein nanofibers, transforming their structure from a random coil network to a more ordered alpha helical structure. Zein films did not show this obvious shift. This structural change reflects the results of a drug release study where nanofibers showed a slower, sustained release of therapeutics compared with their film counterparts. Statistical analysis by t-test proved a significant difference in release from fibers vs. release from films (p < 0.01 for low wt%). The structural integration of zein with its therapeutics also improved the thermal properties of the biomaterial, where fibers did not degrade until temperatures reached 160 °C, but films degraded earlier at 130 °C. Finally, the biocompatibility of zein was confirmed by culturing HEK293 cells on different zein films and fibers for 72 h. An MTT assay confirmed good biocompatibility and an improved cell density on fibers and films compared with a blank control. These promising results, summarized in Figure 1, demonstrate that corn zein has a large potential in the field of drug delivery and biomaterials. Full article

The population growth and the limited reservoir of fossil resources have ignited the attention of scientific communities and entrepreneurs to produce alternative products with raw-materials from renewable sources. In this work, proteins derived from the recycling of waste textiles were studied as raw-material in the synthesis of thermosetting polymers of a phenolic type suitable for use as adhesives in the production of wood-based panels. The chemical bonds between raw-materials and phenol-formaldehyde (PF) resins were verified with Fourier Transform Infrared spectroscopy. The curing performance and thermal stability of the thermosetting PF resins were studied with Differential Scanning Calorimetry and Thermogravimetric Analysis, respectively. Wood-based panels were prepared and tested at a lab scale following simulation of the industrial practice. Optical Microscope and Scanning Electron Microscopy were applied for the study of the interaction between PF resins and woodchips at the lab scale. It was found that the resins were successfully prepared. The maximum curing temperature of the experimental resins was shifted to higher values than the control PF. The protein-based resins seem to lose mass at a lower rate, which denotes that they are more thermally stable than a typical PF resin. Full article

The European food sector generates about 250 million ton/year of by-products and waste, of which around 10% is from fruit and vegetable processing, with a heavy environmental burden. The agri-food residues (AFRs) contain a significant fraction of cellulose and bioactive compounds, which, if recovered, are high added-value material components. The reduction of cellulose down to nano-sized crystalline structures (nanocellulose, NC) provides versatile building blocks, which self-assemble into new materials with superior performances. The PANACEA project, within the frame of PRIN 2017 call supported by the Italian Ministry of University and Research, proposes an approach based on the recovery of cellulose and bioactive compounds from AFRs, with high yield, at various degrees of hierarchical organization, by cascading different physical and chemical processes of increasing complexity, including physical processes and microbial digestion to obtain micro-and nano-sized cellulose structures while preserving their bioactivity. Chemical and enzymatic processes are used to isolate, purify, and functionalize NC at different levels of hierarchical organization, and to design advanced functional materials such as food ingredients, edible coatings, functional colloids, biocides, and flame retardants. Full article

Chronic wounds (CW) have numerous entry ways for pathogen invasion and prosperity, damaging host tissue and hindering tissue remodeling. Essential oils exert quick and efficient antimicrobial (AM) action, unlikely to induce bacterial resistance. Cajeput oil (CJO) has strong AM properties, namely against Staphylococcus aureus and Pseudomonas aeruginosa. Chitosan (CS) is a natural and biodegradable cationic polysaccharide, also widely known for its AM features. CS and poly(vinyl alcohol) (PVA) films were prepared (ratio 30/70; 9 wt%) by solvent casting and phase inversion method. Films’ thermal stability and chemical composition data reinforce polymer blending. Films were supplemented with 1 and 10 wt% of CJO in relation to total polymeric mass. Loaded films were 23 and 57% thicker, respectively, than the unloaded films. Degree of swelling and porosity also increased, particularly with 10 wt% CJO. AM testing revealed that CS films alone were effective against both bacteria, eradicating all P. aeruginosa within the hour (*** p < 0.001). Still, loaded CS/PVA films showed improved AM traits, being significantly more efficient than unloaded films right after 2 h of contact. This study is the first proof of concept that CJO can be dispersed into CS/PVA films and show bactericidal effects, particularly against P. aeruginosa, this way opening new avenues for CW therapeutics. Full article

Polymers commonly have low thermal conductivity in the range of 0.1–0.2 W·m⁻¹·K⁻¹, which is a limiting factor for their usage in the course of continuously increasing miniaturization and heat generation in electronic applications. Two strategies can be applied to increase the transport of phonons in polymers: (i) the embedment of thermally conductive inorganic materials and (ii) the involvement of aromatic units enabling anisotropy by π–π stacking. In this study, the thermal conductivity of resins based on bisphenol A diglycidyl ether BADGE and 1,2,7,8-diepoxyoctane DEO was compared. DEO can be derived from pseudo-pelletierine, which is contained in the bark of the pomegranate tree. The epoxy compounds were cured with isophorone diamine IPDA, o-dianisidine DAN, or mixtures of the both diamines. Notably, isophorone diamine is derived from isophorone of which the latter naturally occurs in cranberries. The formulations were produced without filler or with 5 wt.-% of SiO₂ nanoparticles. Significantly enhanced thermal conductivity in the range of 0.4 W·m⁻¹·K⁻¹ occurs only in DEO-based polymer networks that were cured with DAN (and do not contain SiO₂ fillers). This observation is argued to originate from π–π stacking of the aromatic units of DAN enabled by the higher flexibility of the aliphatic carbon chain of DEO compared to that of BADGE. This assumption is further supported by the facts that significantly improved thermal conductivity occurs only above the glass-transition temperature and that nanoparticles appear to disrupt the π–π stacking of the aromatic groups. In summary, it can be argued that the bisphenol-free epoxy/amine resin with an epoxy compound derivable from natural resources shows favorably higher thermal conductivity in comparison to the petrol-based epoxy/amine resins. Full article

The importance of 3D printing is growing rapidly. A recent example of this increasing importance involves the fight against the Covid-19 pandemic, in which 3D printing has helped to overcome the shortage of critical supplies. However, 3D printing generates large amounts of plastic waste that could pose an environmental problem, thus making it necessary to find methods for the correct management of such wastes. The combination of additive manufacturing and distributed mechanical recycling can contribute to the development of a more circular economy. The main goals of this work were to characterize the poly(lactic acid) (PLA) wastes generated in 3D printing processes and evaluate the effect of their heterogeneity on the technical feasibility of mechanical recycling. Two PLA 3D printing wastes were used: waste coming from a well-known PLA grade, and a mixture of PLA 3D printing residues coming from an association of coronamakers in Madrid. Recycled material obtained from the waste of a well-known PLA grade shows good properties, similar to those for non-used material. However, the recycled material obtained from mixed PLA waste shows lower viscosity values, higher crystallization ability and less transparency. These results highlight that special attention should be paid to the sorting and characterization of the 3D wastes, to obtain recycled materials with good properties. Full article

Coffee silverskin is one of the byproducts generated by the coffee industry. Although it is not the most burdensome one, because it stands only for ~4.2 wt % of coffee, it seems like an auspicious raw material for industrial processes. Coffee silverskin is characterized by a relatively low moisture content of ~5–7%, so it often does not require quite energy-consuming drying processes. The chemical composition of coffee silverskin, as well as other renewable materials, may be significantly affected by its type and origin, in this case, plant Coffea. Nevertheless, due to high fiber content, it could be considered as exciting material for the manufacturing of wood polymer composites. At the same time, it contains noticeable amounts of proteins, which may provide additional features to polymer composites. However, what is most important is the high content of antioxidants, which could noticeably enhance their lifetime by inhibition of the oxidation reactions. In the presented paper, attempts of coffee silverskin incorporation into different polymer matrices were summarized and discussed. Moreover, potential future trends in this area of research were proposed. Full article

In this presentation, absorption (transient absorption) and emission (steady state and time-resolved fluorescence) spectroscopy were used to study, investigate and characterize the mechanisms of fluorescence quenching and obtain new sensors with which to detect toxic environments: heavy metals from water. For this purpose, new compounds were synthesized in order to have a good fluorescence (high quantum yield), stability and selective sensibility. The study of fluorescence quenching by different metal ions, such as Ni²⁺, Cu²⁺, Co²⁺, Zn²⁺, Fe³⁺, Mn²⁺, Ca²⁺, Pb²⁺, Cr³⁺, Cd²⁺, Sr²⁺, and Mg²⁺, will be conducted in solution and film at different temperatures and variations in time to demonstrate that these samples have good stability and can be used as fluorescence sensors for the selective detection of metal ions. For fundamental study, the theory of dynamic quenching, theory of static quenching and combined dynamic and static quenching were used, and the constants of the process, lifetime in excited state, quantum yield and non-radiative and radiative rate constants were estimated. The lifetime, around 0.0001 s for each of the metal complexes, was calculated by the analysis of the decay with and without oxygen. Emission from singlet oxygen was observed at 1275 nm in all samples, and the lifetime and quantum yield are dependent on the substitution on metal ions. In addition, a new application of the compounds investigated for detection of toxic environments (heavy metals—Fe) was found: a sensor to detect Fe from water. Full article

The increase in the world’s economic growth and global population requires a more efficient management of the Earth’s natural resources. The combined plastic and food sector forms an important part of the EU economy, accounting for 15 million jobs. Unlocking the innovation potential in the field of packaging and cosmetics will significantly contribute to job creation and competitiveness. Sustainable synthesis of polyhydroxyalkanaotes from agro-food by-products as well as synthesis of lactic acid co-polymers constitute a pathway to achieving sustainable polymeric matrices. Natural fibers, as well as polysaccharides (starch, cellulose, chitin, chitosan), cutin, and protein rich by-products, are abundantly available from the agro-food industry. Natural fibers may be modified chemically with enzymes or by treating their surface with natural waxes, with a significant improvement in adhesion and impact resistance. An overview on the availability, collection, treatment, and approach of valorization of largely available agro-food waste biomass for both polymer and biocomposite production is hereby reported, with examples of case studies and product developed in our research units, such as sustainable pots, rigid containers, active films, and non-woven tissue. Full article

Cat’s claw and aloe vera gel contain active compounds and could be used to enhance the properties of wound dressings. Cat’s claw is known for its anti-inflammatory, anti-arthritic and anti-asthmatic properties; and aloe vera is commonly used for wound healing and skin hydration. In this study, we elaborated microparticles from an emulsion made of alginate solutions with aloe vera gel or cat’s claw extract with ultrasound and tri-dimensional membranes obtained by solvent evaporation. The 27 to 33 µm-thick membranes showed a porous surface on scanning electron microscopy (SEM); the contact angle of water on the membranes increased in hydrophilicity due to the use of aloe vera gel. Furthermore, the presence of aloe vera also improved water absorption in an acetate buffer (pH 5.5) at 37.5 °C. Finally, the presence of cat’s claw extract in the microparticles significantly enhanced radical scavenging in the 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid), ABTS, decoloration assay, in comparison to tri-dimensional alginate membranes with no active compounds. Alginate films with cat’s claw extract or aloe vera gel could be used as wound dressings materials. Full article

Microbial contamination represents an undesirable event in various domains. Bioactive natural compounds possess plenty of health benefits, including antimicrobial, antifungal and antioxidative activity; however, they are chemically unstable and susceptible to oxidative degradation. In this context, encapsulation or immobilization methods play a key role in enhancing efficiency. Therefore, in this paper are presented some results regarding the development of antimicrobial polymeric materials using surface-modification and emulsion-stabilization approaches. Two polymeric substrates, one biodegradable, poly(lactic acid), and one non-biodegradable polyethylene, functionalized by γ-irradiation have been modified with different active compounds in order to obtain bioactive food packaging materials. The bioactive agents (clove essential oil and argan vegetal oil) were incorporated into a biopolymer matrix (chitosan) then immobilized on the surface of the functionalized substrates by a wet-treatment involving carbodiimide chemistry. The resulted materials were physico-chemically characterized in order to evaluate the molecular interactions between the natural bioactive compounds and polymeric matrix, the stability of the immobilized surface layer, and their barrier properties. Antimicrobial and antioxidant activities were also evaluated. Moreover, the surface biofunctionalized polymeric substrates were tested as potential packaging materials for cheese preservation. The obtained materials have demonstrated improved barrier properties, good antioxidant and antimicrobial properties, which lead to a delay of the tested food spoilage. Full article

This paper provides an overview of the recent progress in research and development dealing with polymers derived from plant oils. It highlights the widening interest in novel approaches to the synthesis, characterization and properties of these materials from renewable resources and emphasizes their growing impact in sustainable macromolecular science and technology. The monomers used include unmodified triglycerides, their fatty acids or the corresponding esters, and chemically modified triglycerides and fatty acid esters. Comonomers include styrene, divinylbenzene, acrylics, furan derivatives, epoxides, etc. The synthetic pathways adopted for the preparation of these materials are very varied, going from traditional free radical and cationic polymerizations to polycondensation reactions, as well as metatheses and Diels–Alder syntheses. In addition to this general appraisal, the specific topic of the use of tung oil as a source of original polymers, copolymers and nanocomposites is discussed in greater details in terms of mechanisms, structures, properties and possible applications. Full article

Plant polyphenols are becoming more and more popular due to their strong antiaging properties. The best researched and largest group of polyphenols are flavonoids. Flavonoids have high antioxidant and pharmacological activities and these properties are closely related to their structure. Certain structural elements of these compounds condition their properties and improve or degrade the activities. As a result of the polymerization of flavonoids, macromolecular compounds showing more favorable properties, such as, for example, bactericidal and antioxidant activity, can be obtained. The aim of this study is to polymerize selected flavonoids (quercetin and rutin) in reaction with a crosslinking compound. Glycerol diglycdyl ether (GDE) causes the crosslinking of quercetin or rutin monomers and the formation of polymeric structures. The study analyzed the thermal stability of monomeric and polymeric flavonoids and their antioxidant activity. Poly(flavonoids) showed greater resistance to oxidation than their monomeric forms. Moreover, poly(quercetin) and poly(rutin) have a greater ability to reduce transition metal ions. Polymeric forms of quercetin and rutin can potentially be effective stabilizers, e.g., for polymeric materials. Full article

This work is focused on the design and development of biocompatible self-assembling hydrogels, which behave as soft gels at room temperature and strong gels at the physiological temperature, suitable for potential bio-applications. A graft copolymer of sodium-alginate, bearing eight side chains of poly(N-isopropylacrylamide), enriched with the hydrophobic comonomer N-tertiary-butyl-acrylamide (NtBAM), (NaALG-g-P(NIPAM-co-NtBAM)) were used as gelator. In total, 5 wt% aqueous polymer solutions in the presence of Ca²⁺ cations were prepared and evaluated as thermo-responsive hydrogels. Rheological experiments revealed a twostep reversible gelation either upon heating or cooling. The divalent cations operated as a cross-linking agent through ionic interactions, inducing the formation of a network at low temperatures. Upon heating, an additional crosslinking develops through thermo-induced hydrophobic association of the thermo-responsive P(NIPAM-co-NtBAM) side chains above a critical temperature. The combination of thermo- and shear-responsiveness provides shelf-assembling systems as potential candidates for injectable strategies. For instance, the system under investigation could be used for cell transplantation, which requires a weak gel to protect the cells during injection and a gel strengthening after the injection at a physiological temperature to immobilize the created scaffold in the targeting position of the host tissue. Full article

The recently approved restriction on diisocyanates highlights the health and safety issues concerning polyurethane manufacturing and the relevance of developing sustainable insulating polymeric foams. This is particularly challenging for applications where the foam is subjected to high temperatures (>80 °C) and bear loads, such as insulating and bonding material for district heating pipes. As part of a PhD project concerning pre-insulated district heating pipes for the circular economy, polybutylene (PB-1) has been identified as a promising candidate for the application, due to its low thermal conductivity, high-temperature mechanical properties, retention, excellent environmental stress cracking resistance (ESCR) and outstanding creep resistance. It is a recyclable thermoplastic and of non-toxic nature, pre-requisites for circular product development. On the contrary to other polyolefins, PB-1 is reported to strain-harden and has high melt strength, required properties for foaming. The purpose of the study is to assess the foamability of PB-1 through extrusion foaming experiments. A twin-screw extruder was used with varying concentrations of a chemical blowing agent. The obtained samples have been characterised for density, expansion ratio and microstructure. Foams with a volume expansion ratio of 1.8 were achieved. The results confirm the foamability of this polymer. The increase of the die pressure and its contribution to strain hardening were identified as key parameters for successful foaming. Further research will include improving the expansion ratio with a physical blowing agent and mechanical characterization of the foam. Full article

In the last years, chronic wounds have become more prevalent, leading to a huge burden on the healthcare and social systems by requiring specialized protection. Indeed, wound dressings capable of assisting in the healing process are in urgent need. To that effect, nanofibrous dressings with a structure resembling the extracellular matrix have been engineered by electrospinning from combinations of poly(vinyl alcohol) (PVA) and cellulose acetate (CA) and optimized to endure physiological media contact and mechanical stress after crosslinking. Mats were prepared at different PVA/CA ratios, 100/0, 90/10 and 80/20 v/v%, at 10 w/v% concentration in acetic acid and water in a 75/25 v/v% proportion and processed via electrospinning. Processing conditions were optimized to obtain uniform, continuous, bead free mats, with a flexible structure. The instant solubilization of the PVA portion of the mat in aqueous media was surpassed via crosslinking. Even though there are many chemical agents available to accomplish such task, glutaraldehyde (GA) is by far the most common due to its efficiency, ease of access and processing, and low cost. Further, in its vapor form, GA has demonstrated reduced or no cytotoxic effects. The amount of GA, crosslinking time, temperature, and drying procedure were optimized to guarantee mechanically resilient mats by means of the greenest methodology possible. Indeed, it was determined that GA vapor at 25% in water could be applied for 7 h at 60 °C, using 6 mL of solution, in a 130 × 120 mm² mat with optimal results. All traces of GA were then eliminated from the mats in a controlled environment (41% relative-humidity and 19 °C). In the end, it was seen that the mechanical resilience and thermal stability of the mats were improved after the application of the modified, green GA-based crosslinking, revealing the engineered methodology potential for applications in biomedical devices. Full article

Electrospinning is a widely used technique to draw recalcitrant biopolymer solutions into micro to nanoscale materials in a simple and economical way. The first focus of this research involved using ionic liquids as a non-volatile solvent for natural insoluble biopolymers such as silk and cellulose (or cellulose derivatives). Compared to traditional organic solvents, ionic liquids can dissolve biopolymers without altering the molecular weight of the biopolymer. In this study, 1-ethyl-3-methylimidizolium acetate (EMIMAc) ionic liquid was used and the regenerated films were coagulated in baths of EtOH or water. The second focus of this research explored the dissolution of IL-regenerated composites into organic solvents and their electrospun composite nanomaterials. Various ratios of silk-cellulose bio-composite films regenerated from ionic liquids were used as the raw materials and sequentially dissolved/dispersed into a Formic Acid-CaCl₂ solution in order to initiate the electrospinning of silk-cellulose nanomaterials. Because of the variability of ionic liquids, the nanomaterials produced using this technique have unique and tunable properties such as large surface area to volume ratios and low structural defects. FTIR and SEM results suggest that the structure and morphology of the final nanosized samples becomes more globular when the biopolymer composition ratio has increased cellulose content. TGA results demonstrated that the electrospun materials have better thermal stability than the original films. This two-step electrospinning method, using ionic liquid as a non-volatile solvent to first dissolve and mix raw natural materials, may lead to extensive research into its biomedical and pharmaceutical applications in the future. Full article

The design of interfaces in green polymer composites is a crucial factor in ensuring mechanical strength in composite materials. While cellulose fibers have high intrinsic mechanical strength, their reinforcing effect in polymer composite materials relies greatly on the creation of a tight interface with the surrounding polymer matrix. In parallel, the hydrophilicity of the cellulose has to be compatibilized with often more hydrophobic polymer matrixes. In this study, the cellulose interface has been modified by the self-assembly of polymer-peptide nanoparticles regulating the adhesive strength in the interface. The incorporation of catecholic groups allows physical adsorption at the cellulose surface in parallel with the mimicking of mussel-inspired adhesion in the presence of dopamine groups. In this study, the cellulose surface modification was performed with different concentrations of the adhesive nanoparticles, and interesting trends in adhesive forces at macroscale length were observed. The macroscale adhesion was characterized by single-fiber pull out tests, indicating an optimum concentration of nanoparticles at the surface to provide high adhesive interface strength. In addition, the nanoparticles show colorimetric and fluorescent response to mechanical shear stresses, providing an evaluation tool to explore the interface phenomena upon failure. Full article

Considering the rising demand to diminish energy consumption and CO₂ emissions, the biobased segmented block copolymer, poly(butylene succinate-co-dilinoleic succinate) (PBS-DLS) with 70:30 (wt %) ratio of hard to soft segments was obtain using Candida antarctica lipase B (CAL-B) as a biocatalyst. Throughout two-step synthesis in diphenyl ether, biobased diethyl succinate was polymerized with renewable 1,4–butanediol and dimer linoleic diol to obtain “green” copolyester as a sustainable alternative to petroleum-based materials. Proton nuclear magnetic resonance (1H NMR) analysis confirmed that, using enzyme as a catalyst, we were able to produce multiblock copolymer and gel permeation chromatography (GPC) measurements revealed number-averaged molecular mass to be 25,000 g/mol. Additionally, differential scanning calorimetry (DSC) analysis revealed low-temperature glass transition (T_g) of soft segments and high melting point (T_m) of hard segments which indicate on two-phase morphology. Furthermore, cytotoxicity test using L929 murine fibroblasts was conducted on extracts of obtained PBS-DLS copolymer, indicating excellent biocompatibility in vitro. Full article

Health and safety issues should be addressed during the development and investigation of industrial processes. In order to develop a sustainable process and fully evaluate its benefits and drawbacks for its optimization, it is crucial to determine its impact on the surrounding environment. This study aimed to assess the emission of volatile organic compounds during the modification of lignocellulosic fillers with passive dosimetry. Two types of processes were investigated: diisocyanate treatment of commercial lignocellulosic fillers in a batch mixer and thermo-mechanical treatment of brewers’ spent grain using a twin-screw extruder. The presence of multiple terpenes and terpenoids was detected during the processing of fillers. The main compounds detected during modification were camphene, 3-carene, limonene, α-pinene, and cymenes. These compounds can cause irritation and allergic reactions, according to the Globally Harmonized System of Classification and Labelling of Chemicals, as well as NFPA 704: Standard System for the Identification of the Hazards of Materials for Emergency Response. Some of them are also characterized by relatively low values of flash points, even below 40 °C. Therefore, their emissions during the modification of cellulose materials should be carefully monitored, and proper precautions need to be taken. Full article

Worldwide, buildings consume over 40% of the total commercial energy, and 36% of this amount is dedicated to the heating and cooling of buildings. Therefore, building environment control systems require efficient thermal management. An ideal thermal management that could lower the energy load for cooling and heating respectively would combine passive strategies for thermal control, which are characterized by low cost, straightforward implementation, and energy efficiency, with the on-demand control of heating and cooling, specific for active thermal management strategies. The scientific challenge of building an efficient platform for thermal control was addressed by using block copolymer materials in the development of nanocomposites with dynamically tunable thermal infrared properties. The polymer nanocomposites manage 60–70% of the metabolic heat flux from sedentary individuals and can modulate changes in the individual body temperature within a set-point temperature range of 8 °C. This increase in the set-point temperature translates into use of air conditioning for cooling/heating with a significantly lowered load, which would further translate into a 4.3% decrease of global energy consumption. Full article

The increasing costs of virgin content, decreasing resources, and growing plastic waste have shifted the research momentum towards green and sustainable road pavements. Hence, in recent years, various researchers have worked on the utilization of different types of plastic wastes in asphalt concrete by replacing it with binder content. Under this premise, this study examines the effect of expanded polystyrene beads (EPS) as a replacement to the binder at seven different dosages ranging from 5% to 50%. The bitumen of 60/70 grade was utilized in this study. The fresh properties of polymer-modified bitumen were checked and compared to that of conventional specimens. The mechanical properties of all specimens were investigated in terms of Marshall Stability properties. The results indicated that the adding of PEB improves the stability of modified asphalt concrete. Furthermore, the addition of EPS by substituting bitumen content could be a promising way to reduce the environmental impact of bitumen, and will also help in economic infrastructure development. Full article

The properties of polymer-based nanocomposites strongly depend on the fillers added and their dispersion on the matrix. Proposing a simple method that can control these variables is essential to obtain nanocomposites with enhanced properties. In this study, cellulose triacetate based nanocomposites modified with sol-gel synthesised vanadium oxide nanoparticles (V₂O₅) and poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (PEO-b-PPO-b-PEO or EPE) triblock copolymer were obtained by two methods: solvent casting (SC, drying at ambient conditions) and solvent vapour annealing (SVA, drying under solvent vapour atmosphere). Nanocomposites were characterised by Fourier-transform infrared spectroscopy (FTIR) and UV-vis spectroscopy. Nanocomposites presented green colour and high transparency, improving the SVA method the surface finish of the films. Moreover, V₂O₅ nanoparticles provided switchable photochromic properties, changing the film colour from green to pale blue when exposed to UV radiation. Nanocomposites with EPE triblock copolymer presented a more noticeable colour change. As for the speed of the recovery process to the initial state, it increased with the addition of EPE and the sol-gel content. Thus, it was proved that the SVA preparation method was more appropriate that the SC, as well as corroborate that the EPE triblock copolymer and the sol-gel content affected the properties of developed CTA nanocomposites. Full article

This paper aims to investigate the effect of different chemical modifications of biocomposites based on poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) and aloe vera bio-fibers incorporated at 20 wt%. The fiber surface was modified with alkaline, organosilanes, and combined alkaline/organosilanes. Surface morphology, thermal stability, water absorption capacity, and rheological behavior of the modified biocomposite materials were studied, and the results compared to both unmodified biocomposites and neat PHBH. The study showed that the modified biocomposites with both alkaline and organosilanes exhibited an improved surface morphology, resulting in a good fiber/matrix interfacial adhesion. As a result, increases in complex viscosity, storage modulus, and loss modulus were observed, whereas water absorption was reduced. Thermal stability remained almost unchanged, with the exception of the biocomposite treated with alkaline, where this property decreased significantly. Finally, the coupling of alkaline and organosilane modification is an efficient route to enhance the properties of PHBH biocomposites. Full article

Pseudomonas aeruginosa is considered a public threat, with antibiotics increasing their resistance. Essential oils (EOs) have demonstrated significant effects against microorganisms. However, due to their volatile nature, they cannot be used in their free-state. Here, hydrogel-like films were produced from a combination of sodium alginate (SA) and gelatin (GN) to serve as delivery platforms for the controlled release of cinnamon leaf oil (CLO) entrapped within chitosan (CS) microcapsules. The minimum inhibitory concentration (MIC) of CLO was established at 39.3 mg/mL against P. aeruginosa. CS microcapsules were prepared via ionotropic gelation with tripolyphosphate (TPP), encapsulating CLO at MIC. Successful production was confirmed by fluorescent microscopy using Nile red as a detection agent. Microcapsules were embedded within a biodegradable SA/GN polymeric matrix processed by solvent casting/phase inversion with SA/GN used at 70/30 polymer ratio at 2 wt.% SA concentration. A concentration of 2 wt.% CaCl₂ was used as a coagulation bath. The CLO-containing CS microcapsules’ homogeneous distribution was guaranteed by successive vortex and blending processes applied prior to casting. CLO controlled release from the films was monitored in physiological pH for 24 h. Hydrated films were obtained, with the presence of loaded CS capsules being confirmed by FTIR. Qualitative/quantitative antimicrobial examinations validated the loaded film potential to fight P. aeruginosa. Full article

The fused deposition modeling (FDM) process, commonly known as three-dimensional (3D) printing, deals with the manufacturing of parts by the subsequent addition of layers of fused plastic filament. The parts obtained during this process can be used for domestic applications, rapid prototyping, or final applications. During the preparation of the printing model (slicing), different process parameters must be defined, such as extruder speed, extruder height in relation to the bed, and bed temperature. Parameters that, if incorrectly defined, can lead to a series of deficiencies in the parts, such as low dimensional accuracy, low surface quality, reduced mechanical resistance, and, eventually, the occurrence of several printing defects in the parts, impairing or even preventing its use. The 3D printing process has a critical period at its beginning during the manufacturing of the piece’s first layer. The present work aims to study some of the geometric anomalies observed in monolayer pieces when some of the printing parameters are improperly defined. Printing tests on monolayer parts were carried out with a polylactic acid (PLA) filament. Herein, a home grade 3D printer, model Graber i3, was used. The height of the extruder to the bed was altered in relation to the recommended value, and three pieces were printed for each height used. The printed parts were scanned with a 1200 × 1200 dpi resolution, using a DCP-L2540DW model scanner. The images obtained were then analyzed using the Matlab^® software and the geometric characteristics of the pieces were compared. The study is a first step towards a better understanding of the geometric defects obtained when an incorrect definition of basic parameters occurs when processing the three-dimensional model. Full article

Membranes were used in many aqueous applications, including in food processing, e.g., clarification of fruit juices. Typical drawbacks of membrane processes are membrane fouling, which promotes deterioration of processed products. During application of membranes for fruit juice clarification, biofouling occurred as the process deals with food substances. Biofouling is commonly dominated by bacterial attachment and growth on membrane surface, following the deposition of organic molecules from food substances. Natural antibiotics such as Olea europaea leaves extract might be used to improve the antibiofouling properties of membranes due to its phenolic contents. In this work, Olea europaea substances were obtained by extraction to get the green active solid nanoparticles. Phenolic green nanoparticles then filled into cellulose acetate as membrane matrix. The mixed matrix membrane, therefore, has a safe antibiofouling properties and is suitable for food application. The anti-biofoulant effect has been proven by decreasing bacterial attachment down to 23% from initial condition, especially for Gram-negative bacteria such as Eschericia coli. Full article