Materia Nova

The high flammability of bio-based insulation materials derived from plant fibers is a major barrier to their widespread use, necessitating the development of effective flame-retardant treatments. This study aims to optimize the treatment of raw hemp fibers by comparing two environmentally-friendly application methods: immersion and spraying. The fibers are treated with a solution containing phytic acid and urea, as biobased sources of phosphorus and nitrogen. The efficiency of the treatments is assessed by characterizing the quantity of phosphorus grafted, the thermal degradation of the fibers by thermogravimetric analysis and their flammability using a mass loss calorimeter. Both application methods are effective, but the spraying method demonstrated superior performance, resulting in a higher level of phosphorus grafted to the fibers and a reduced heat release rate. Additionally, the formation of a protective char layer on the fiber surface helps to limit flame propagation. Notably, this method requires ten times less treatment product than immersion, making it a highly scalable and efficient solution for the industrial production of flame-retardant insulating materials. • Two flame-retardant treatment methods are tested on bulk hemp fibers. • Both treatment methods significantly reduce the flammability of the hemp fibers. • The spraying method results in a higher phosphorus content, and a lower flammability. • The quantity of treatment for the spraying method is lower than for immersion. • The pulverization method can be used to treat fibers on a large scale.

Covalent Adaptable Networks (CAN) and CO2-derived polyhydroxyurethanes (PHU) are often deemed as sustainable alternatives to conventional thermosets, particularly for composites used with epoxy (EP) matrices. However, the sustainability of CAN-based composites has never been assessed, nor has that of thermoset PHUs. Herein, we perform a life cycle assessment of PHU, synergetic hybrid EP-PHU CANs, and epoxy in composite applications with either carbon or natural fibers (NF) in order to address their syntheses, processes, and recycling. We demonstrate that producing cyclic carbonate monomers from epoxy and supercritical CO2 could be advantageous. PHU provides potential environmental benefits to epoxy but is significantly limited by the energy inputs required for curing. Inversely, synergetic EP-PHU demonstrates noticeable environmental gain compared to EP and PHU-based composites and offers ideal recycling pathways. The chemical recovery of carbon fibers by oxidative depolymerization shows substantial benefits compared to virgin material production. When using natural fibers, mechanical recycling of CAN-based matrices is more suited due to the impacts of chemical recycling compared to virgin NF production, highlighting that the viability of a strategy strongly depends on raw material and cannot be generalized easily. Strategies to further enhance the sustainability of composites are also proposed and discussed.

Cobalt aluminate (CoAl2O4) pigment, synthesized from recycled aluminum obtained from can seals and transformed into the boehmite phase, was combined with ammonium polyphosphate (APP422) to produce an efficient flame-retardant material for polylactide (PLA) while simultaneously imparting coloration to the polymer matrix. The chemical structure of the pigment was investigated using X-ray photoelectron spectroscopy and X-ray diffraction prior to its integration into PLA in combination with ammonium polyphosphate (APP422). Thermal gravimetric analysis highlights the superior effect of the APP422/CoAl2O4 combination that enables obtaining a greater amount of char, presenting improved thermal stability and an enhanced protective effect, as clearly evidenced by Mass Loss Cone test results. A reduction of 70% in peak heat release was observed when APP422 was combined with CoAl2O4, in contrast to a reduction of 31% when only APP422 was used at a similar incorporation level. The enhanced flame-retardant properties of the combined APP422 and CoAl2O4 additives can be attributed to a rapid formation of a homogeneous char layer at the surface of the burning material when both additives are used together. This results from the interaction between Co3+ and APP422, which leads to the formation of the thermally stable Co3(PO4)2 phase.

João Leal foi meu professor na licenciatura em antropologia, no mestrado e, finalmente, no doutoramento. Em conjunto com Catarina Alves Costa, foi também o meu coorientador de tese. Ela própria fora uma antiga doutoranda de João Leal. Poder-se-ia olhar para estas continuidades e encadeamentos do ensino e da transmissão do conhecimento como uma dimensão particular da economia da dádiva proposta por Marcel Mauss. Este ensaio fundar-se-ia, pois, numa ideia de reciprocid

Here, we present the study of the intricate dynamics between the physicochemical properties of liquid propanethiol plasma polymer films (PPFs) and the formation of wrinkles in PPF/Al bilayers. The study investigates the effect of liquid PPF aging in the air before top Al layer deposition by magnetron sputtering on the wrinkling phenomenon for 4 days. Thanks to atomic force microscopy, the wrinkle dimensions were found to decrease by approximately 55% in amplitude and 66% in wavelength, correlated with an increase in the viscosity of the PPF over the aging duration (i.e., from less than 107 to 1010 Pa·s). This behavior is not linked to alterations in cross-linking degree as evidenced by time-of-flight secondary ion mass spectrometry experiments but rather to network densification driven by the inherent molecular chain mobility due to the viscous state of the PPF. X-ray photoelectron spectroscopy measurements emphasizing the absence of oxidation of the PPF over the aging duration support this, revealing a unique aging mechanism distinct from other plasma polymer families. Overall, this study offers valuable insights into the design and application of mechanically responsive PPFs involved in bilayer systems, paving the way for advancements in nanotechnology and related fields.

A 30-month pilot study was conducted to evaluate the potential of in-situ metal(loid) removal through biostimulation of sulfate-reducing processes. The study took place at an industrial site in Flanders, Belgium, known for metal(loid) contamination in soil and groundwater. Biostimulation involved two incorporations of an organic substrate (emulsified vegetable oil) as electron donor and potassium bicarbonate to raise the pH of the groundwater by 1–1.5 units. The study focused on the most impacted permeable fine sand aquifer (8–9 m below groundwater level) confined by layers of non-permeable clay. The fine sands exhibited initially oxic conditions (50–200 mV), an acidic pH of 4.5 and sulfate concentrations ranging from 600 to 800 mg/L. At the central monitoring well, anoxic conditions (−200 to −400 mV) and a pH of 5.9 established shortly after the second substrate and reagent injection. Over the course of 12 months, there was a significant decrease in the concentration of arsenic (from 2500 to 12 μg/L), nickel (from 360 to <2 μg/L), zinc (from 78,000 to <2 μg/L), and sulfate (from 930 to 450 mg/L). Low levels of metal(loid)s were still present after 34 months (end of study). Mineralogical analysis indicated that the precipitates formed were amorphous in nature. Evidence for biologically driven metal(loid) precipitation was provided by compound specific stable isotope analysis of sulfate. In addition, changes in microbial populations were assessed using next-generation sequencing, revealing stimulation of native sulfate-reducing bacteria. These results highlight the potential of biostimulation for long-term in situ metal(loid) plume treatment/containment.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

In the spirit of circular economy and sustainable chemistry, the use of environmentally friendly chemical products in pharmacy has become a hot topic. In recent years, organic solvents have been the subject of a great range of restriction policies due to their harmful effects on the environment and toxicity to human health. In parallel, deep eutectic solvents (DESs) have emerged as suitable greener solvents with beneficial environmental impacts and a rich palette of physicochemical advantages related to their low cost and biocompatibility. Additionally, DESs can enable remarkable solubilizing effect for several active pharmaceutical ingredients (APIs), thus forming therapeutic DESs (TheDESs). In this work, special attention is paid to DESs, presenting a precise definition, classification, methods of preparation, and characterization. A description of natural DESs (NaDESs), i. e., eutectic solvents present in natural sources, is also reported. Moreover, the present review article is the first one to detail the different approaches for judiciously selecting the constituents of DESs in order to minimize the number of experiments. The role of DESs in the biomedical and pharmaceutical sectors and their impact on the development of successful therapies are also discussed.

Flexible piezoresistive pressure sensors are key components in wearable technologies for health monitoring, digital healthcare, human–machine interfaces, and robotics. Among active materials for pressure sensing, graphene-based materials are extremely promising because of their outstanding physical characteristics. Currently, a key challenge in pressure sensing is the sensitivity enhancement through the fine tuning of the active material’s electro-mechanical properties. Here, we describe a novel versatile approach to modulating the sensitivity of graphene-based piezoresistive pressure sensors by combining chemically reduced graphene oxide (rGO) with a thermally responsive material, namely, a novel trifunctional polybenzoxazine thermoset precursor based on tris(3-aminopropyl)amine and phenol reagents (PtPA). The integration of rGO in a polybenzoxazine thermoresist matrix results in an electrically conductive nanocomposite where the thermally triggered resist’s polymerization modulates the active material rigidity and consequently the piezoresistive response to pressure. Pressure sensors comprising the rGO-PtPA blend exhibit sensitivities ranging from 10–2 to 1 kPa–1, which can be modulated by controlling the rGO:PtPA ratio or the curing temperature. Our rGO-PtPA blend represents a proof-of-concept graphene-based nanocomposite with on-demand piezoresistive behavior. Combined with solution processability and a thermal curing process compatible with large-area coatings technologies on flexible supports, this method holds great potential for applications in pressure sensing for health monitoring.