This is an editorial article. It has no abstract.
In this paper, master curves are reported for the crosslinking of a diene rubber with a sulphur based system in the presence of either nano- or nano-structured carbon allotropes, such as carbon nanotubes (CNT), a nanosized graphite with high surface area (HSAG) and carbon black (CB). Poly(1,4-cis-isoprene) from Hevea Brasiliensis was the diene rubber and crosslinking was performed in temperatures ranging from 151 to 180 °C, with carbon allotropes below and above their percolation threshold. Such carbon allotropes were characterized by different aspect ratio, surface area and pH. However, in the crosslinking reaction, they revealed common behaviour. In fact, the specific interfacial area could be used to correlate crosslinking parameters, such as induction time (ts1) and activation energy (Ea) calculated by applying the autocatalytic model. Monotonous decrease of ts1 and increase of Ea were observed, with points lying on master curves, regardless of the nature of the carbon allotropes. Remarkable differences were however observed in the structure of the crosslinking network: when the carbon allotrope was above the percolation threshold much larger crosslinking density was obtained in the presence of CNT whereas composites based on HSAG became soluble in hydrocarbon solvent, after the reaction with a thiol. Proposed explanation of these results is based on the reactivity of carbon allotropes with sulphur and sulphur based compounds, demonstrated through the reaction of 1-dodecanethiol and sulphur with CNT and HSAG and with a model substrate such as anthracene.
The present study describes the fabrication of Indium Tin Oxide /gold nanoparticles/nickel oxide/poly(Pyrrole-N-propionic acid) (ITO/GNPs/NiO/poly(PPA)) multilayered film, and its modification with Tyrosinase (Ty). The ITO/GNPs/NiO/poly(PPA) electrode was fabricated by sequential electrochemical assembly onto ITO substrate which electrochemical deposition provides a facile, inexpensive technique for synthesis of multilayered film within the adherent morphology with controllable film thickness. Cyclic voltammetry (CV), Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), scanning electron microcopy (SEM), and atomic force microcopy (AFM) were used to characterize the film assembly processes. The properties of a semiconductor/electrolyte interface were investigated based on the Mott–Schottky (M-S) approach for the modified electrodes, with the flat band potential (EFB) according to the potential intercept and the carrier density (ND) according to the linear slopes. The ND and EFB of ITO/GNPs/NiO/poly(PPA) were obtained as 2.48·1021 cm–3 and 0.26 V, respectively. Tyrosinase was immobilized using carbodiimide coupling reaction. The bioelectrode was characterized by FTIR-ATR, SEM, AFM, electrochemical impedance spectroscopy (EIS). A Randles equivalent circuit was introduced for modeling the performance of impedimetric biosensing for the detection of the dopamine (DP) and the interface of bioelectrode/electrolyte. The EIS of the ITO/GNPs/NiO/poly(PPA)-Ty exhibited significant changes in the charge transfer resistance (RCT) value toward the detection of dopamine over a linear range of 80 µM to 0.2 mM with a limit of detection (LOD) of 5.46 µM.
Urethane bismaleimides (BMIs) were used in order to obtain crosslinked structures by their reaction with an aromatic trifuran compound. The Diels-Alder (DA) reaction between the maleimide and furan moieties was investigated using proton nuclear magnetic resonance (1H-NMR) spectroscopy for a model compound (CTF), due to the fact that the networks are insoluble in usual NMR solvents. The structure of the networks was confirmed by infrared spectroscopy. Thermal properties were investigated (by means of differential scanning calorimetry (DSC) and thermogravimetrical analyses (TGA)) and compared with the ones of similar compounds, previously obtained from the same BMIs and a different trifuran compound (which contains tertiary nitrogen in its structure). Mechanical and rheological properties were also investigated. The influence of the nature of the polyol from the BMIs structure and/or the influence of using a trifurylic compound with or without tertiary nitrogen on the properties of the crosslinked networks were also discussed.
Thermoplastic polymer/layered silicate composites were prepared from the same organophilized montmorillonite (OMMT) and four different matrices, polypropylene (PP), the blend of PP and a maleated polymer (MAPP), poly(lactic acid) (PLA) and polyamide (PA) in order to study the effect of their chemical structure and interactions on composite structure and properties. The components were homogenized by extrusion and then specimens were injection molded, which were then characterized by a variety of methods. The results showed that competitive interactions among silicate layers and between the silicate and the polymer determine the extent of exfoliation, and structure. The morphology of the composites is complicated, exfoliation is never complete, besides individual silicate layers, the composite can contain a silicate network, stacks of silicate platelets and larger particles in various amounts. Several local deformation processes can take place around the structural entities as well as in the matrix. Fracture and debonding are the main particle related processes, while cavitation takes place in the polymer, at least in PA and PLA. The macroscopic properties of layered silicate composites are determined by the extent of exfoliation and interfacial adhesion that decreases upon organophilization. Increased reinforcement and improved composite properties can be achieved only by the proper control of all interactions prevailing in the composite.
Polycaprolactone based macrophotoinitiator was synthesized via enzymatic ring-opening polymerization by using commercially available Irgacure-2959 as the nucleophilic initiator and Novozyme-435 as the immobilized lipase catalyst. The macrophotoinitiator was further utilized to photopolymerize benzyl acrylate (BzA), tetrahydrofurfurly acrylate (THFA), 2-hydroxyethyl acrylate (HEA) and poly (ethylene glycol) methyl ether acrylate (Mn ~ 480 g/mole) (PEGMEA-480) under Ar atmosphere. The obtained polymers were characterized by 1H Nuclear Magnetic Resonance, Fourier Transform Infrared Spectroscopy, Differential Scanning Calorimetry and Size Exclusion Chromatography. The highest dry polymer conversions were achieved with BzA and THFA. However, due to the gel formation during the photopolymerization reactions of HEA and PEGMEA-480, the dry polymer conversions were comparably lower. The photopolymerization product of BzA demonstrated a single glass transition temperature at –6.5 °C. The enzymatically synthesized macrophotoinitiator was shown to be an efficient catalyst for light-induced polymerization of the abovementioned monomers.
Polymeric polyelectrolytes obtained from renewable sources for biodiesel wastewater treatment by dual-flocculation
E. A. M. Ribeiro, G. Rodrigues Filho, N. S. Rozeno, J. M. B. A. Nogueira, M. A. Resende, J. P. Thompson Junior, J. G. Vieira, S. C. Canobre, F. A. Amaral
Vol. 11., No.6., Pages 504-517, 2017
Vol. 11., No.6., Pages 504-517, 2017
Biodiesel wastewater generally contains high levels of oils, soaps and glycerol residues. This needs wastewater treatment. In this study, the biodiesel wastewater treatment was tested (industrial wastewater (EFID) and laboratory wastewater (EFLB) from biodiesel) by performing flocculation and dual-flocculation with renewable polymers. Tannin and cationic hemicellulose (CH) were used as cationic flocculant, and cellulose acetate sulfate (CAS) was used as an anionic flocculant. Polyacrylamide (PAM) was used as a reference anionic flocculant for result efficiencies analysis obtained with CAS (renewable source flocculant). The treatment efficacy in wastewater was evaluated by: turbidity removal, sludge volume formed, chemical oxygen demand (COD) and total suspended solids (TSS). The obtained sludge was studied using thermogravimetric analysis (TG). The dual-flocculation application condition of the 25% proportion of tannin (T) and 75% proportion of cationic hemicelluloses (i.e., T25/CH75) showed EFLB turbidity removal of 89.1% and 89.5% for CAS and PAM additions respectively, and for EFID of 67% and 41% for CAS and PAM additions respectively. The dual-flocculation performance suggested that the polyelectrolytes obtained from renewable sources can be used for treating biodiesel wastewater.
Roll-to-roll gravure printing is considered as potential leading manufacturing technology for flexible, low cost and large area optoelectronics. However, solution processed multilayer organic electronics are still challenging to be produced, especially in the case of electrodes. In this work, the gravure printing technique was successfully employed to realize the highly conductive poly(3,4ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) polymeric anode and tested for the first time in flexible ITO-free (Indium Thin Oxide) organic light emitting diodes (OLEDs). The device performances were found to be similar to those of a reference device containing a spin-coated polymeric anode. A gravure printed dimethyl sulfoxide (DMSO) post-treatment was successfully tried to improve the printed anode characteristics. The obtained results show the way for future development for processing flexible ITO-free devices using the most attractive printing technology for roll-to-roll large area manufacturing.