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This study aims to provide further understanding on the depolymerization of polyurethanes (PU) via acidolysis. Therefore, polyurethane foams scraps are chemical recycled using different dicarboxylic acids, namely succinic and phthalic dicarboxylic acids, being the reaction products identified using Fourier‐transform infrared spectroscopy, nuclear magnetic resonance and gel permeation chromatography. The results obtained show that succinic acid has higher efficiency as cleavage agent, as a result, the succinic acid ensuing recovered polyol (RP) presents higher hydroxyl value and lower viscosity. Additionally, from the oxidative‐induction time measurements, it is observed that the RP is considerably more thermally stable, than the petroleum‐based polyol, due to the higher content of aromatic moieties. Afterwards, the RP is used as substitute of petroleum‐based polyol in the production of polyurethane adhesives (PUA) and compared with conventional polyol based PUA. Due to the higher content of aromatic moieties, higher bonding strength is achieved using the RP. Overall, further understanding on the acidolysis is obtained, proving the suitability of this method for the recycling of PU. A method for the recycling of polyurethane (PU) wastes, acidolysis, is presented. The recycled polyol (RP) was used in the production of PU adhesives. The presence of aromatic moieties yields stiffer adhesives.

Aiming to produce high-quality bio-based 3D printed products, in this work, coconut fibers were chemical modified using caprolactone. Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic reasonance (NMR) confirmed the grafting of the hydroxyl groups present on the surface of the fibers with caprolactone units. Furthermore, from contact angle (CA) analyses, the higher hydrophobicity of fibers after chemical treatment was confirmed, which improved its affinity with PP. The enhanced filler/matrix compatibility was reflected on the mechanical performance and processability of the ensuing composites. The modified fibers derived composites showed higher stiffness and higher melting flow index (MFI), when compared to the untreated counterparts. The composites were used to produce 3D printed specimens. Smother filaments were obtained using modified fibers, which confirms the better compatibility of fibers/PP. The surface of the 3D printed composite specimen produced using treated fibers, presented smooth surface, similar to the PP. This observation highlights the enhancement of the 3D printing quality due to the chemical modification of fibers.

Additive manufacturing enables the creation of lighter, stronger parts and systems. To improve the 3-dimensional (3D) printed quality of bio-based composites, in this study, bamboo fibers were chemically modified via a two-step reaction. In the first step, NCO groups (of a diisocyanate) were grafted onto the surface of fibers, which were subsequently reacted with a polyol. The chemical modification was confirmed by spectroscopic analysis; the hydrophobicity, density, and thermal degradation of the fibers were also evaluated. Afterward, 3D-printed objects were produced using these fibers. First, the printability of these composites was assessed by analyzing their melting flow index (MFI) and glass transition temperature (Tg) values. Next, the enhancement of the 3D printing quality was confirmed by analyzing the morphology of the 3D-printed specimens. The advantage of using treated fibers was reflected in the improved mechanical performance of the obtained 3D specimens.

The primary objective of this research is to advance our understanding of the recycling of polyurethane foams (PUF) through the process of acidolysis, with the specific focus on evaluating the potential of recovering rigid PUF waste. Drawing from the prior investigations on acidolysis of flexible PUF waste, we extended our research to the depolymerization of rigid PUF using succinic acid. The resulting recycled polyol (RP) exhibited comparable characteristics to the RP derived from flexible PUF. This similarity was confirmed by Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analyses, as well as by examining the hydroxyl number (OHnumber) and acid value (AV) of the ensuing RP. Subsequently, rigid foams were produced using the RP as a partial replacement of the conventional polyol. The assessments of the PUF obtained revealed that this substitution did not compromise the morphology nor the physical properties of the foams. This was verified by scanning electron microscope (SEM) analyses, mechanical tests, and thermogravimetric analyses (TGA). In summary, our findings indicate that acidolysis is a viable method for recycling both flexible and rigid PUF, underscoring the growing significance of this recycling technique for the development of more sustainable materials.

In this work, two synthesis procedures for the preparation of urea-formaldehyde (UF) resins, based on the alkaline–acid process, are studied in order to better understand the chemical reactions involved. For that purpose, the number of urea loads and the methyolation temperature were varied. The molecular weight distribution of the resins was monitored by gel permeation chromatography/size exclusion chromatography and the unreacted oligomers by high-performance liquid chromatography, during the synthesis processes. Chemical modifications were investigated using quantitative analysis by carbon-13 nuclear magnetic resonance of samples taken during the synthesis. The largest difference identified between the procedures regards the methylene linkages and methylol groups determined by 13C NMR. With the results of this study, it is possible to optimize the process and the properties of particleboards produced.

The development of analytical platforms incorporating Au nanoparticles (NPs) for optical biosensing requires approaches to produce optically responsive and target selective materials. In the present work, fluorescence emission and bioselectivity of Au NPs have been combined by a one-step surface functionalization using fluorescein isothiocyanate (FITC) and biotin. First, colloidal Au NPs (d?=?17.7?±?2.7 nm) exhibiting an absorption maximum (?max) at 524.5 nm have been surface-modified with the polyelectrolytes (PE) poly(allylamine hydrochloride) (PAH) and poly(sodium styrene sulfonate) (PSS). Two strategies were then assessed for the functionalization of Au NPs: (i) functionalization of PAH with biotin and subsequent coating of the NPs and (ii) surface modification of the NPs with the PE followed by post-functionalization with biotin. The effect of the surface functionalization on the colloidal NPs was monitored by optical absorption and fluorescence emission spectroscopies, dynamic light scattering (DLS), zeta potential measurements and transmission electron microscopy (TEM). Finally, the optical response and specificity of the functionalized NPs towards avidin was evaluated by optical measurements. The results have shown that these hybrid nanostructures have potential to be used in biosensing. In particular, the aggregation of biotinylated Au assemblies associated with the biorecognition of avidin could be assessed by fluorescence emission spectroscopy.

The present study reports the development of a new generation of bio-based nanocomposite proton exchange membranes based on bacterial cellulose (BC) and poly(4-styrene sulfonic acid) (PSSA), produced by in situfree radical polymerization of sodium 4-styrenesulfonate using poly(ethylene glycol) diacrylate (PEGDA) as cross-linker, followed by conversion of the ensuing polymer into the acidic form. The BC nanofibrilar network endows the composite membranes with excellent mechanical properties at least up to 140 °C, a temperature where either pure PSSA or Nafion are soft, as shown by dynamic mechanical analysis. The large concentration of sulfonic acid groups in PSSA is responsible for the high ionic exchange capacity of the composite membranes, reaching 2.25 mmol g–1for a composite with 83 wt % PSSA/PEGDA. The through-plane protonic conductivity of the best membrane is in excess of 0.1 S cm–1at 94 °C and 98% relative humidity (RH), decreasing to 0.042 S cm–1at 60% RH. These values are comparable or even higher than those of ionomers such as Nafion or polyelectrolytes such as PSSA. This combination of electric and viscoelastic properties with low cost underlines the potential of these nanocomposites as a bio-based alternative to other polymer membranes for application in fuel cells, redox flow batteries, or other devices requiring functional proton conducting elements, such as sensors and actuators.

Recent studies involving chitosan interacting with phospholipid monolayers that mimic cell membranes have brought molecular-level evidence for some of the physiological actions of chitosan, as in removing a protein from the membrane. This interaction has been proven to be primarily of electrostatic origin because of the positive charge of chitosan in low pH solutions, but indirect evidence has also appeared of the presence of hydrophobic interactions. In this study, we provide definitive proof that model membranes are not affected merely by the charges in the amine groups of chitosan. Such a proof was obtained by comparing surface pressure and surface potential isotherms of dipalmitoyl phosphatidyl choline (DPPC) and dipalmitoyl phosphatidyl glycerol (DPPG) monolayers incorporating either chitosan or poly(allylamine hydrochloride) (PAH). As the latter is also positively charged and with the same charged functional group as chitosan, similar effects should be observed in case the electrical charge was the only relevant parameter. Instead, we observed a large expansion in the surface pressure isotherms upon interaction with chitosan, whereas PAH had much smaller effects. Of particular relevance for biological implications, chitosan considerably reduced the monolayer elasticity, whereas PAH had almost no effect. It is clear therefore that chitosan action depends strongly either on its functional uncharged groups and/or on its specific conformation in solution.

SiO2/polystyrene nanocomposite particles were synthesized via miniemulsion polymerization using sodium dodecyl sulfate (SDS) as surfactant and hexadecane as hydrophobe in the presence of silica particles coated with methacryloxy(propyl)trimethoxysilane (MPS) surface coupling agent. The silica particles were individually coated with polymer yielding a very homogenous nanocomposite latex which was very stable in a wide range of ionic strengths. Monomer conversion was reasonably high and fast.

The need for developing more sustainable electrochemical energy storage and conversion devices prompted us to develop novel bio-based membranes based on poly(lactic acid) (PLA) and imidazolium ionic liquids (ILs) to act as an electrolyte in energy conversion devices, such as fuel cells. PLA membranes based on [C4C1im][PF6] and [C4C1im][BF4] present different morphologies according to the anion nature and high thermal stability (>300 °C). Scanning electron microscopy and energy-dispersive spectroscopy analyses show that [C4C1im][BF4] tends to be isolated inside small pore cavities, which prevents the IL from leaching out of the membranes. Owing to this improved retention capacity of [C4C1im][BF4] and to the hydrophilic character of the IL anion, the PLA–[C4C1im][BF4] blends present conductivity values higher than 0.01 S cm–1at 98% RH and 94 °C. The work further demonstrates the operation of a PLA–[C4C1im][BF4]-based oxygen/hydrogen fuel cell with an open-circuit voltage above 0.9 V.