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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. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG. published

This study aimed to develop new rigid polyurethane foams (RPUFs) for thermal insulation based on kraft lignin, the main by-product of the pulp and paper industry. Crude lignin-based polyol (LBP) was obtained via the oxyalkylation of kraft lignin using propylene carbonate (PC). A design of experiments (DoE) was used to evaluate the effect of the isocyanate (NCO)-to-hydroxyl (OH)-group’s ratio, the content of crude LBP, the blowing agent (BA), and catalyst on the thermal conductivity and density of RPUFs. Statistical analysis revealed that the increase in crude LBP and BA content in the formulation decreases the thermal conductivity and density of the foams. In addition, the fact that LBP is a viscous polyol containing PC-oligomers appears to affect the cellular structure of RPUFs, and consequently reduces their mechanical and thermal properties. The main novelty of this study consisted in the careful optimization of the formulation, namely, with regard to the type of blowing agent and with the high content of crude LBP obtained from the oxyalkylation of LignoBoost kraft lignin without purification to obtain good quality RPUF that meets market requirements for insulation materials.

Aiming at minimizing the issues associated with the disposal of polymers, in this study, elastomeric materials derived from 100% recycled feedstocks were produced. Residues of polyurethane (PU) foams (from 0 to 100%) were blended with residues of ethylene–vinyl acetate (EVA) derived from the shoe-soles industry (from 0 to 100%) to produce films by hot compression. The experimental values obtained by the characterization of the blends were compared with the predicted values derived from the rule of mixtures. Despite of the two-phase morphology observed, the high correlation between the experimental and predicted values suggest that phase segregation did not have a significant effect on the properties of the blends. Voids were also observed on the PU derived materials, due to the source of PU (foams), which reduced their density and increased the water absorption. Yet, this did not jeopardize the mechanical performance of the ensuing materials. In addition, higher amounts of PU resulted in stiffer materials, while higher amounts of EVA induced higher thermal stability. From the results, it was demonstrated that the PU/EVA blends, produced from 100% recycled feedstock, presented suitable properties to be used in shoe-soles applications. published

Aiming the sustainability of 3D-printed objects, in this study, pine bark particles were used as filler reinforcement for polyamide 6 (PA). In order to enhance the performance of the produced composites, the biomass was chemically modified via a two-step procedure. In the first step, the OH groups present on the particles surface were reacted with ethylenediamine, which were subsequently reacted with a polyol. Fourier-transform infrared spectroscopy (FTIR), 13C solid-state cross polarization–magic angle spinning nuclear magnetic resonance (13C CPMAS NMR) and scanning electron microscopy coupled with energy-dispersive X-ray analysis confirmed the chemical modification of biomass. The masterbatch was prepared from modified pine bark particles and polymeric matrix (PA) being processed into test specimens. The ensuing composites revealed a significant increase in Young's modulus and maximum stress. Thus, the introduction of 10% modified biomass increases the Young's modulus by 87% and the maximum stress by 15%. Furthermore, analyzing the glass transition temperature (Tg), melting flow index and thermogravimetric analysis results, the modified biomass ensuing composites proved to be suitable for 3D printing. This was attributed to better compatibility between chemically modified biomass and matrix and, further, easier processing.

In this study polyurethane (PU) residues were mixed with residues of textile fibers (cotton, wool and synthetic fibers up to 70 wt/wt) to produce 100% recycled composites. In addition, the effect of the type of fiber on the performance of the ensuing composites was evaluated. The presence of fibers showed similar effect on the density, reducing the density in the 5.5-9.0% range. In a similar manner, the addition of fillers decreased their thermal conductivity. The 70 wt/wt wool composite presented 38.1% lower thermal conductivity when compared to the neat matrix, a reduction that was similar for the other type of fibers. Moreover, the presence of fillers yields stiffer materials, especially in the case of the Wool based composites, which with 70 wt/wt of filler content increased the tensile modulus of the ensuing material 3.4 times. This was attributed to the aspect ratio and stiffness of this type of fiber. Finally, the high-water absorption and lower thermal stability observed, especially in the case of the natural fibers, was associated with the hydrophilic nature of fibers and porosity of composites. Overall, the results suggest that these textile-based composites are suitable for construction and automotive applications, with the advantage of being produced from 100% recycled raw-materials, without compromised performance.

Lignocellulosic composites are biodegradable, have low cost, neutrality to CO2 emission, easily processed, easily available and pause no health risks, therefore these materials have been the subject of an increase of interest. In addition, there is a continuous demand of materials obtained from renewable resources and waste recycling. In that sense, in this study polyurethane (PU) residues were mixed with residues of cork and pine (up to 70 wt/wt) to produce 100% recycled composites. Cork is well known to be a light and a thermal insulator material, so the addition of cork granulates decreased both density (circa 51%) and thermal conductivity (circa 61%) of the composites. In turn, pine fibers are hydrophilic and have cylindrical shapes, thus their presence increased the water absorption and improved the mechanical properties of the composites. From the results, these composites proved to be suitable to be used as structure and thermal insulation materials with the advantage of being produced from 100% recycled raw-materials. published

Three dimensional (3D) printed elastomers is a challenge which can be overcome using fillers. With that in perspective, cork was chemically modified via a two-step reaction, aiming to achieve better compatibility with styrene-ethylene-butylene-styrene (SEBS). In the first step, the OH groups of cork surface were grafted with succinic acid, while in the second step the free acid groups were reacted with a polyol to produce ester moieties. Spectroscopy analysis confirmed the occurrence of the chemical reaction which was supported by contact angle (CA) measurements. The unmodified cork presents a CA of 117.7°, while the modified cork presents a CA of 92.4° which is closer to that of SEBS (102.8°), resulting in better compatibility between the modified filler with the matrix. In fact, the enhancement of compatibility between polymer and filler was observed by inspecting the layer-to-layer bonding and was confirmed by the mechanical properties of the 3D printed composites, since the modified cork-based composite presented higher Young modulus, maximum stress and elongation at break when compared to the untreated counterparts. Additionally, the advantage of the chemical treatment was evaluated by analyzing the processability of composites. The modified filler-based composite, presents lower glass transition temperature (Tg), higher melt flow index (MFI) and higher thermal stability. Overall, in this work, a simple chemical route to modify lignocellulosic biomass and its benefit on the properties of 3D printing objects is discussed. The improved performance and sustainability of the 3D printed objects produced to be used for example in shoe applications was presented published

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–1 at 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. published

Lignin obtained by Lignoboost® procedure from black liquor after kraft pulping of Eucalyptus globulus wood was characterized and converted into liquid polyols via an innovative and safe procedure using base catalyzed oxyalkylation with propylene carbonate (PC). The effect of four catalysts, Potassium carbonate (K2CO3), 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU), dicyanodiamide (DICY), and 1,4-diazabicyclo [2.2.2] octane (DABCO) was evaluated in terms of lignin polyol yield and weight gain. The ensuing polyols were also characterized by fourier transform infrared (FTIR), 1H NMR, 13C NMR, and size exclusion chromatography (SEC) to determine the degree of the substitution (DS), degree of polymerization (DP), and the molecular weight, respectively. Only a minor proportion of PC (ca. 3–15%) was converted to propylene glycol/homooligomers as revealed by high performance liquid chromatography (HPLC). All catalysts promoted preferential derivatization of lignin phenolic OH groups by oxypropyl moieties. The maximum average DP of propylene oxide chains in oxyalkylated Lignoboost® kraft lignin (oKL) was 1.85 per one phenylpropane unit (PPU) using DBU. Conversely, the DP of oKL using DICY was very low (0.27/PPU). DICY’s catalytic activity seems to be jeopardized due to the formation of unreactive adducts with lignin. The oKL obtained using DBU, DABCO, and K2CO3 have potential to be used as polyols in the production of polyurethanes as the corresponding hydroxyl number (IOH) is in the range of 198–410 mg KOH g−1.

This work intends to provide a preliminary approach concerning the preparation of 3D printed products derived from recycled raw-materials. In that sense, recycled polyurethane foam (PUF) particles were added (up to 10% wt/wt) to thermoplastic polyurethane (TPU) to prepare 3D printed products. From the results, it was observed that the presence of PUF particles reduces the density of filaments. Moreover, even though filler and matrix are polyurethane (PU) polymers, the fact that PUF scraps consists of crosslinked PU, it affects inter-layer adhesion, reducing the mechanical performance of the 3D printed specimens, especially when high PUF particles contents were used. Nonetheless, despite of the limitations identified, the addition of PUF particles did not affect the thermal stability of the composites, meaning that these composites can be processed at high temperatures. Therefore, PUF scraps were successfully reused which proved to be a low cost additive for the production 3D printed composites (when using low content), with the advantage of being an alternative to the disposal of PUF.

Lignosulfonates (LS) from acidic magnesium-based sulfite cooking of Eucalyptus globulus wood were modified via laccase-catalyzed oxidative treatment with the aim to improve their performance as plasticizing additives in concrete formulations. The target parameters were the increment of molecular weight (Mw) and the amount of oxidized groups. The laccase-assisted oxidation under optimized conditions (40°C, pH 4.5, enzyme loads of 83–500 U g−1 for 90 min) allowed Mw increment up to 11-fold and almost doubled the amount of carbonyl and carboxyl groups without using any mediators. Modified LS maintained their solubility in water and possessed a zeta- potential close to that of initial LS. The characterization of modified LS has been carried out by ultraviolet-visible (UV-Vis), Fourier transform infrared-attenuated total reflectance (FTIR-ATR) and quantitative 13C nuclear magnetic resonance (NMR) spectroscopy, and the sulfonic and phenolic groups were assessed by conductometric titration. It was concluded that LS polymerization occurred mostly via the formation of new aryl ether bonds (two thirds of the modification) and biphenyl bonds (the remaining third). However, part of the newly formed bonds of unknown origin are temperature labile and cleaved during the concentration of LS at pH 4 and 80°C under vacuum, which led to the reduction of the Mw of the modified lignin to almost one third.

Nowadays, wood-based panel producers intend to lower costs by decreasing the pressing time and reducing resin consumption. Therefore, the aim of this work is to understand the influence of the pressing operating conditions (pressing time and pressing program) on the performance of particleboards (PBs) bonded with a UF resin (alkaline–acid process). For this purpose, several trials were carried out using a computer-controlled laboratory scale hot-press with a press cycle simulating a continuous press and a fixed position laboratory scale hot-press, varying the venting, the total pressing time ( 90 s) and the gluing factor (resin content—4, 5 and 6 mg resin solids/g oven dry wood). Analysis of variance (ANOVA) was performed in order to evaluate the significance level of the effects of these parameters on PB’s physico-mechanical properties and formaldehyde content. The main results of the study were: to decrease formaldehyde content, resin content (RC) should be increased for pressing times higher or equal to 90 s or decreased for pressing times lower than 90 s; to increase internal bond, RC must be increased for pressing times equal or higher than 90 s, or decreased for pressing times lower than 90 s.

The feasibility of using lignosulfonate (LS) from acid sulphite pulping of eucalyptus wood as an unmodified polyol in the formulation of polyurethane (PU) adhesives was evaluated. Purified LS was dissolved in water to simulate its concentration in sulphite spent liquor and then reacted with 4,4′-diphenylmethane diisocyanate (pMDI) in the presence or absence of poly(ethylene glycol) with Mw 200 (PEG200) as soft crosslinking segment. The ensuing LS-based PU adhesives were characterized by infrared spectroscopy and thermal analysis techniques. The adhesion strength of new adhesives was assessed using Automated Bonding Evaluation System (ABES) employing wood strips as a testing material. The results showed that the addition of PEG200 contributed positively both to the homogenization of the reaction mixture and better crosslinking of the polymeric network, as well as to the interface interactions and adhesive strength. The latter was comparable to the adhesive strength recorded for a commercial white glue with shear stress values of almost 3 MPa. The optimized LS-based PU adhesive formulation was examined for the curing kinetics following the Kissinger and the Ozawa methods by non-isothermal differential scanning calorimetry, which revealed the curing activation energy of about 70 kJ·mol−1.

Hypothesis Reversible addition fragmentation chain transfer (RAFT) - assisted encapsulating emulsion polymerization (REEP) has received considerable attention as an efficient strategy to prepare colloidal stable shell@core nanoparticles. Generally, amphipathic macroRAFT agents are used but the effect of working above or below the critical micelle concentration (CMC) of macroRAFT agents needs to be addressed. Hence, it is necessary to understand if this parameter has an impact not only on the stability of the colloids but also on the molecular mass of the polymer shell. Methods Here, the CMC of three different macroRAFT agent was determined and the effect of macroRAFT agents concentration on the colloidal stability of gold nanoparticles coated with macroRAFT agents (macroRAFT@Au) assessed. The subsequent chain extension from macroRAFT@Au NPs, resulting in encapsulated Au nanoparticles (copolymer@Au), has also been systematically studied. Findings Using the REEP approach it was possible to obtain stable encapsulated Au NPs. Moreover, this strategy opens the possibility of adjusting the macroRAFT agents concentration to tune the length of the polymer chains grown around Au cores which is of major interest for the design of biosensors based on responsive polymer shells, such as pH, temperature and photoluminescence quenching.

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 C-13 NMR. With the results of this study, it is possible to optimize the process and the properties of particleboards produced.

Carbon dots (CDs) have become one of the most investigated nanomaterials in the last few years, since they offer excellent prospects to be used in a wide range of technological applications. Nonetheless, the understanding of the photoluminescence (PL) processes remains unclear and solely based on spectroscopic measurements at room temperature, which hampered a full discussion on the nature of recombination mechanisms. Insights into the CDs’ PL and corresponding recombination models can be achieved from temperature, excitation energy and excitation density dependency studies. Thus, in this paper, CDs with a mean diameter of ∼3.0 nm were embedded in poly(methyl methacrylate) (PMMA) and studied by such optical techniques. The recombination of CDs/PMMA composites was found to be due to an overlap of emitting centres, both in the blue and green regions, with intensity and peak position strongly dependent on the excitation density. Moreover, this emission was found to be preferentially populated by two overlapped excitation bands. Temperature-dependent PL measurements corroborate the hypothesis of overlapped emitting optical centres (e.g. small molecules at the CDs’ surface), as no shift on peak position and no changes in spectral shape were observed, which allow to exclude the hypothesis of a conventional free excitonic transition and quantum confinement effects, as observed in typical nanosized semiconductors with dimensions lower than the exciton Bohr radius.

This paper presents a study of two crucial synthesis parameters of the alkaline-acid process of UF resin synthesis: condensation formaldehyde/urea (F/U) molar ratio and U feed rate during the methylolation step. The differences in the polymeric structures and the performance of the ensuing resins on particleboards (PBs) properties were analyzed and compared with a standard resin. The molecular weight distribution of the resins was monitored by gel permeation chromatography/size exclusion chromatography (GPC/SEC) and the unreacted oligomers by high-performance liquid chromatography (HPLC). The PBs produced were analyzed following European standards for mechanical tests and formaldehyde emission. The data obtained were also submitted to a statistical analysis. The results obtained showed that the use of low molar ratios yield higher internal bond strength (IB) values and lower formaldehyde emissions (F). In turn, the effect of urea feed rate during the methylolation step on IB values depends on the F/UII molar ratio used: (i) a reduction for the higher final molar ratio used, and no effect for the lowest final molar ratio used. Moreover, the statistical analysis carried out showed that F/UII molar ratio has significance on almost all of the resins’ characteristics. The resin used as standard yielded the best results when the final F/U molar ratio was 1.10 and the resulting PBs presented values of internal bond (IB) of 0.51 N mm−2 and formaldehyde content (F) of 5.1 mg/100 g o.d.b., complying with the market requirements. Additionally, the effect of resin ageing was also studied and the PBs prepared using the best resin upon fifteen days of its production presented similar IB values and even lower F content in relation to those obtained using fresh resin.

The use of poly(vinyl chloride) (PVC) structural layers incorporating phase change materials (PCM) for latent heat thermal energy storage (LHTES) has become more attractive in the recent years compared to other supporting materials. In this study, PVC layers with different types of PCM were prepared using blending and compression moulding methods. Two types of synthesized PCM, one based on paraffin and calcium carbonate (PCM@CaCO3) and the other on paraffin, silica and graphene oxide (PCM@SiGO) have been developed to enhance the thermal conductivity of the PVC matrix and thus achieve a more effective charging and discharging process. PVC layers prepared using a commercial PCM (PCM@BASF) were also prepared for comparison. SEM images and DSC results reveal homogeneous distribution of the PCM in PVC layers and that most PCM particles are undamaged. The shell material (in the case of PCM@BASF) and the shape stability (in the case of synthesized PCM@CaCO3 and PCM@SiGO) prevent leakage of molten paraffin during the PVC layer production. The thermal conductivity profile of the PVC layer without PCM have a decreasing tendency with the temperature increase when determined using different measurement approaches, the transient plane heat source method (HotDisk Analyser, TPS 2500 S) and thermal flux meter method (steady-state method). However, for PVC layers with PCM the thermal conductivity profile shows a different behaviour when the mean surface temperature of the specimen is below the phase change transition temperature range (increasing tendency). During phase change transition (18–26 °C), the thermal conductivity presents two distinct tendencies. Firstly, the thermal conductivity reveals a decreasing tendency as the mean temperature of the specimen rises and afterwards an increasing tendency. Secondly, when the mean surface temperature is above the phase change transition temperature range, the thermal conductivity profile shows a decreasing tendency, independent of the PCM. The mechanical properties of PVC layers were also assessed and the results obtained revealed that the incorporation of PCM into the PVC matrix reduces the mechanical performance of the composites, however for LHETS applications not subjected to high tensile stress levels (over 1 kPa), this is not a significant drawback.

Ionic liquids (ILs), being related to the design of new environmentally friendly solvents, are widely considered for applications within the “green chemistry” concept. Due to their unique properties and wide diversity, ILs allow tailoring new separation procedures and producing new materials for advanced applications. However, despite the promising technical performance, environmental concerns highlighted in recent studies focused on the toxicity and biodegradability of ILs and their metabolites have revealed that ILs safety labels are not as benign as previously claimed. This review refers to the fundamentals about the properties and applications of ILs also in the context of their potential environmental effect. Toxicological issues and harmful effects related to the use of ILs are discussed, including the evaluation of their biodegradability and ecological impact on diverse organisms and ecosystems, also with respect to bacteria, fungi, and cell cultures. In addition, this review covers the tools used to assess the toxicity of ILs, including the predictive computational models and the results of studies involving cell membrane models and molecular simulations. Summing up the knowledge available so far, there are still no reliable criteria for unequivocal attribution of toxicity and environmental impact credentials for ILs, which is a challenging research task.

Cork is a unique material and its by-products are attracting an ever-growing interest for preparing new materials in an attempt to extend the outstanding properties of cork toward innovative and high value applications. Yet, the miscibility of cork particles with thermoplastic matrices is not easy due to its low density and surface properties. Here, cork is functionalized with poly(methyl methacrylate) (PMMA) via atom transfer radical polymerization (ATRP) to yield cork grafted with PMMA chains particles (cork-g-PMMA). Both the ATRP macroinitiator and the cork-g-PMMA obtained are fully characterized by Fourier-transform infrared spectroscopy (FT-IR), 13C cross-polarized magic-angle spinning solid-state nuclear magnetic resonance (13C CP/MAS solid state NMR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD) and thermogravimetric analyses (TGA). The functionalized cork particles are then blended with commercial PMMA to afford cork-g‑PMMA/PMMA. To compare, cork also is mixed with PMMA and the ensuing cork/PMMA sample and its morphology, thermal, and mechanical properties are compared with those of cork-g-PMMA/PMMA and commercial PMMA. The cork surface modification via ATRP of the methyl methacrylate (MMA) yields better dispersion in the matrix. Consequently, a blend with enhanced mechanical performance, higher thermal stability, and a higher melt flow index (MFI) is obtained when compared to the blend prepared using unmodified particles. The similarity of the MFI of cork-g-PMMA/PMMA to that of PMMA suggests good printability. Indeed, a three-dimensional (3D) printed specimen is obtained confirming that grafting using ATRP is a promising route for the preparation of high quality 3D printed products.

6 pags., 6 figs., 3 tabs., The full potential of poly(L-lactide) (PLLA) reinforced with graphene oxide, GO, nanocomposites tends to be hindered by aggregation of the nanofillers. In order to promote a good dispersion of GO in the PLLA matrix, polymer grafting techniques have been explored to anchor PLLA onto functionalized GO surface to produce GO-PLLA hybrids. For this purpose, PLLA with a terminal triple bond was synthesized by ring-opening polymerization. By controlling the concentration of monomer to initiator, PLLA samples with three different chain lengths have been prepared and later coupled to azide-functionalized GO using click chemistry. These hybrids were then mixed with commercial PLLA and cast films have been prepared. The ensuing nanocomposite films were studied using Depth Sensing Indentation and the results have shown that PLLA matrix-filler interaction can be modulated by controlling the chain length of PLLA graft. This is a critical point because the enhancement of these interactions provides a stronger matrix-filler interphase which improves the stress transfer between both phases and increases the contribution of the interphase to the stiffening of the nanocomposites. Therefore, it has been proven that judicious functionalization of GO is an effective procedure for improving the strength, the stiffness and the creep resistance of the PLLA composites., This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, FCT Ref. UID/CTM/50011/2019, financedby national funds through the FCT/MCTES and when appropriate cofi-nanced by FEDER under the PT2020 Partnership Agreement. Centro deQuímica Estrutural acknowledges the financial support of FCT Project,Portugal UIDB/00100/2020.

Research in cell adhesion has important implications in various areas, such as food processing, medicine, environmental engineering, biotechnological processes. Cell surface characterization and immobilization of microorganisms on solid surfaces can be performed by promoting cell adhesion, in a relatively simple, inexpensive, and quick manner. The adhesion of Yarrowia lipolytica IMUFRJ 50682 to different surfaces, especially potential residual plastics (polystyrene, poly(ethylene terephthalate), and poly(tetrafluoroethylene)), and its use as an immobilized biocatalyst were tested. Y. lipolytica IMUFRJ 50682 presented high adhesion to different surfaces such as poly(tetrafluoroethylene) (Teflon), polystyrene, and glass, independent of pH, and low adhesion to poly(ethylene terephthalate) (PET). The adhesion of the cells to polystyrene was probably due to hydrophobic interactions involving proteins or protein complexes. The adhesion of the cells to Teflon might be the result not only of hydrophobic interactions but also of acid-basic forces. Additionally, the present work shows that Y. lipolytica cell extracts previously treated by ultrasound waves (cell debris) maintained their enzymatic activity (lipase) and could be attached to polystyrene and PET and used successfully as immobilized biocatalysts in hydrolysis reactions., CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior)/GRICES (Gabinete de Relacoes Internacionais da Ciencia e do Ensino Superior)CAPES [102/03]; CNPqNational Council for Scientific and Technological Development (CNPq); national funds through the FCT/MCTES [UID/CTM/50011/2019]; Tomas Bata University in Zlin Internal Grant Agency [IGA/CPS/2020/001]

This work discusses the optimization of different synthesis parameters for a low emitting urea-formaldehyde (UF) resin. Industrially, this resin was synthesized using the alkaline-acid process (alkaline methylolation and acidic condensation) at different values of pH, temperature (T) and final viscosity and characterized according to different analytical methods. Particleboards (PBs) were produced using different pressing times and characterized according to the standard tests. A statistical analysis (ANOVA) was performed, and the main conclusion is that small changes on the synthesis of resins parameters do not affect the performance of PBs.

The high thermal conductivity of carbon based nanostructures (CNs) has been recognized appropriate to be integrated into phase change materials (PCMs) to enhance the overall thermal properties of the obtained nanocomposites. The equilibrium of the possibility to enhance the thermal conductivity of the PCMs and the latent heat capcity are the key for their ability to store or dissipate a large amount of energy in a short period of time. This paper gives an update overview summarizing the state-of-the-art concerning nanocomposites prepared using PCMs and CNs with emphasis on the improvement of the latent heat capacity and of the thermal conductivity. Focus is directed towards experimental research studies regarding the enhancement of the thermal properties (thermal conductivity and the latent heat capacity) of PCMs obtained by the addition of the CNs by means of the encapsulation method. The majority of the reported research studies focus mainly on the thermal characterization of PCMs nanocomposites, however there is scarce information about the mechanisms explaining why/how the thermal properties are enhanced. This review outlines the results of the thermal conductivity and the latent heat capacity of PCMs/CNs nanocomposites, trying to identify the features that lead to the improvement of their thermal properties.

The aim of this study is to evaluate the possibility of using unrefined crude glycerol (CG), a byproduct of the biodiesel industry, in the production of polyurethane foams. In order to assess the suitability of this raw material for the production of polyurethane foams, two samples of crude glycerol with different compositions in glycerol, fatty acids, and methyl esters were used directly, without any pretreatment or purification. Additionally, one of these samples was also submitted to a pre-treatment step in order to evaluate the advantage of purifying the raw material and, for comparison, pure glycerol was also used to prepare polyurethane foams. Both chemical and structural characterizations of the produced foams, as well as the thermomechanical properties determined, showed that unrefined crude glycerol is a suitable ecopolyol for the production of polyurethane foams. Although the presence of fatty acids and esters affects their mechanical performance, this issue can be explored to tune the properties of the ensuing polyurethane foams. Furthermore, the evaluation of the impact of using unrefined CG on the sustainability of polyurethane foams production yielded promising results.

The use of a macromolecular RAFT (macro-RAFT) agent to encapsulate anisotropic nano-objects via emulsion polymerization is an emerging route to prepare polymer/inorganic colloidal nanocomposites. However, a number of requirements have to be fulfilled. This work aims at highlighting the effects of the preparative procedure and dispersion method on the amount of macro-RAFT agent adsorbed onto SiO2-coated Gd2O3:Eu3+ nanorods. The adsorption of macro-RAFT agent was studied using the depletion method with UV–vis spectrophotometry. Measurements were performed at a fixed concentration of nanorods and varying concentrations of the macro-RAFT agent in aqueous dispersion at room temperature. The adsorption isotherms showed that for the same initial macro-RAFT agent concentration, the highest adsorption capacity of the macro-RAFT agent on nanorods was usually achieved for non-calcined thin SiO2-coated nanorods under mild bath sonication.

The main purpose of this work was to widen the range of applications of the polyurethane foams (PUFs) obtained from renewable resources as higher added value materials by increasing their electrical and thermal conductivities and get a better insight of the parameters governing these properties. The increase of these properties is frequently achieved by filling PUFs with carbon nanofibers (CNFs), carbon nanotubes (CNTs) or graphene layers, however their cost limits their widespread use. In this work, an inexpensive procedure has been developed to prepare electrical conductive PUFs using castor oil (CO) as polyol and expanded graphite (EG). The chemical and structural characteristics of the ensuing composite foams have been evaluated, as well as their morphology and their mechanical, thermal and electrical properties. The DC electrical conductivity results have been fitted to Taherian model. EG loadings between 0.5 and 1.5% (w/w) caused a systematic increase of the thermal and electrical conductivities Moreover, in this fillers' loading range the remaining physical properties namely the glass transition temperature and the Young's modulus are appropriate for standard applications.

International audience; The functionalization of Laponite RD platelets with different cationic, anionic, and nonionic homo-and copolymers synthesized by reversible addition−fragmentation chain transfer (RAFT) has been investigated. The effective interaction of the macromolecular RAFT agents (macro-RAFTs) with the inorganic particles is known to be of crucial importance for the successful coating of minerals with polymers via RAFT-mediated emulsion polymerization to produce polymer-encapsulated inorganic particles. The macroRAFT agents synthesized in the present work contain carefully selected reinitiating R groups, which bear either ionizable tertiary amine or quaternary ammonium moieties (from 2-(dimethylamino)ethyl methacrylate, DMAEMA), negatively charged acrylic acid (AA) repeat units, or neutral polyethylene glycol (PEG) side chains, and are capable of interacting with Laponite via different adsorption mechanisms. The equilibrium adsorption of these RAFT (co)polymers was investigated by the plotting of adsorption isotherms, and either L-type or H-type curves were obtained. The hydrophobicity of the macroRAFT was shown to promote adsorption, as did the pending configuration of the PEG block. Charge repulsion between AA and the negatively charged surface of Laponite at pH 7.5, on the other hand, was prejudicial for adsorption, while the strong electrostatic interaction between the cationic DMAEMA molecules and the Laponite surface led to high-affinity-type curves.

This paper presents the impact of different processes for producing urea-formaldehyde resins and their roles on the physico-mechanical properties and the formaldehyde emission of the resulting particleboards. Five resins were produced: four via the alkaline-acid process (Resin A to D) and one using the strongly acid process (Resin E). The differences between the syntheses are mainly related to different formaldehyde/urea molar ratios during the synthesis, temperatures, and the number of urea load addition. The molecular weight distribution of the resins was monitored by gel permeation chromatography/size exclusion chromatography and the unreacted oligomers were followed by high-performance liquid chromatography. The shear strength of adhesive joints was evaluated using automated bonding evaluation system. Particleboards produced with these resins were analyzed according to the usual standards for mechanical tests and formaldehyde emission. The resins differ in some characteristics, namely percentage of unreacted oligomers, chemical composition, viscosity, and reactivity. At a pressing time of 120 s, the internal bond of the particleboards was similar for all the resins produced using the alkaline-acid process (approximate to 0.60 N mm(-2)) but differed from that obtained using the strongly acid process (approximate to 0.40 N mm(-2)). However, formaldehyde emissions were apparently independent of the synthesis process.

Cell membrane models have been used to evaluate the interactions of various imidazolium-based ionic liquids (ILs) with Langmuir monolayers of two types of phospholipids and cholesterol. Data from surface pressure isotherms, Brewster angle microscopy (BAM) and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) pointed to significant effects on the monolayers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and cholesterol, used to mimic the membranes of eukaryotic cells, for ILs containing more than 6 carbon atoms in the alkyl chain (i.e. n > 6). For ILs with less hydrophobic tails (n ≤ 6) and low concentrations, the effects were almost negligible, therefore, such ILs should not be toxic to eukaryotic cells. The hydrophobicity of the anion was also proved to be relevant, with larger impact from ILs containing tetrafluoroborate ([BF4]-) than chloride (Cl-). Molecular dynamics simulations for DPPC monolayers at the surface of aqueous solutions of alkylimidazolium chloride ([Cnmim]Cl) confirm the penetration of the IL cations with longer alkyl chains into the phospholid monolayer and provide information on their location and orientation within the monolayer. For monolayers of dipalmitoylphosphatidyl glycerol (DPPG), which is negatively charged like bacteria cell membranes, the ILs induced much larger effects. Similarly to the results for DPPC and cholesterol, effects increased with the number of carbon atoms in the alkyl chain and with a more hydrophobic anion [BF4]-. Overall, the approach used can provide relevant information of molecular-level interactions behind the toxicity mechanisms and support the design of (quantitative) structure-activity relationship models, which may help design more efficient and environmentally friendly ILs. published