ABSTRACT
In recent years, wood fibres have often been applied as the reinforcement of thermoplastic materials, such as polypropylene, whereas their use in combination with thermosetting resin has been less widespread. This study concerns the production of PMMA-based composites by partly replacing alumina trihydrate (ATH) with wood waste fillers, namely rice husks and almond shells, which would otherwise be disposed by incineration. The amount of filler introduced was limited to 10% as regards rice husks and 10 or 15% almond shells, since indications provided by reactivity tests and viscosity measurements did not suggest the feasibility of total replacement of ATH. As a matter of fact, the introduction of these contents of wood waste filler in PMMA-based composite did not result in any significant deterioration of its mechanical properties (Charpy impact, Rockwell M hardness and flexural performance). Some reduction of these properties was only observed in the case of introduction of 15% almond shells. A further issue concerned the yellowing of the organic filler under exposure to UV light. On the other hand, a very limited amount of water was absorbed, never exceeding values around 0.6%, despite the significant porosity revealed by the filler's microscopic evaluation. These results are particularly interesting in view of the application envisaged for these composites, i.e., wood replacement boards.
ABSTRACT
New (E/Z)-2-(2-(1-cyano-2-methoxy-2-oxoethylidene)hydrazinyl)benzoic acid (H2L(4)) and known sodium 2-(2-(dicyanomethylene)hydrazinyl)benzenesulfonate (NaHL(1)), 2-(2-(dicyano-methylene)hydrazinyl)benzoic acid (H2L(2)), and sodium (E/Z)-2-(2-(1-cyano-2-methoxy-2-oxoethylidene)hydrazinyl)benzenesulfonate (NaHL(3)) were used in the template synthesis of a series of Cu(II) and Co(II) complexes [Cu(H2O)2L(1a)]·H2O (1), [Cu(H2O)(3-pyon)L(1b)]·H2O (2), [Cu(H2O)(4-pyon)L(1b)] (3), [Co(H2O)((CH3)2NCHO)(µ-L(2a))]2·(CH3)2NCHO (4), [Cu3(µ3-OH)(NO3)(CH3OH)(µ2-X)3(µ2-HL(3))] (5), [Cu(H2O)(py)L(3)]·H2O (6), [Cu(H2O)2(µ-L(4))]6·6H2O (7), [Cu(2-cnpy(b))2(L(1b))2]·2H2O (8), [Cu(2-cnpy(a))2(L(1a))2]·2H2O (9), and [Cu(H2O)(4-cnpy)(L(1a))2] (10), where 3-pyon = 1-(pyridin-3-yl)ethanone, 4-pyon = 1-(pyridin-4-yl)ethanone, py = pyridine, HX = syn-2-pyridinealdoxime, 4-cnpy = 4-cyanopyridine; 2-cnpy(a), 2-cnpy(b), L(1a), L(1b), L(2a) are the ligands derived from nucleophilic attack of methanol (a) or water (b) on a cyano group of 2-cyanopyridine (2-cnpy), L(1) or L(2), respectively, giving the corresponding iminoesters (2-cnpy(a), L(1a) or L(2a)) or carboxamides (2-cnpy(b) or L(1b)). An auxiliary ligand, namely syn-2-pyridinealdoxime or pyridine, acting cooperatively with the metal ion (Cu(II) in this case), induced an E/Z isomerization of the H2L(4) ligand; the E- and Z-isomers were isolated separately and fully characterized (compounds 9 and 10, respectively). A one-pot activation of nitrile groups in different molecules was achieved in the syntheses of 8 and 9. Complexes 1-10 are catalyst precursors for the solvent-free microwave (MW)-assisted selective oxidation of secondary alcohols to the corresponding ketones, with typical yields in the 29-99% range (TOFs up to 4.94 × 10(3) h(-1)) after 30 min of MW irradiation.
Subject(s)
Cobalt/chemistry , Coordination Complexes/chemistry , Copper/chemistry , Hydrazones/chemistry , Nitriles/chemistry , Isomerism , Ligands , Models, MolecularABSTRACT
The synthesis of bis(thioether)-functionalized imidazolium salts, the characterisation of the first S,C(NHC),S free carbene ligand and the corresponding Ag(i) and Pd(ii) functional carbene complexes are reported. The latter have been prepared from the isolated Ag(i) carbene complexes using the transmetallation procedure or by reaction of the imidazolium salts with [PdCl(2)(COD)], followed by deprotonation of the intermediate in which both thioether functions are coordinated to Pd(ii).
