Surface Protection of Wood with Metal Acetylacetonates

Metal acetylacetonates are coordination complexes of metal ions and the acetylacetonate anion with diverse uses including catalysts, cross-linking agents and adhesion promotors. Some metal acetylacetonates can photostabilize polymers whereas others are photocatalysts. We hypothesize that the ability of metal acetylacetonates to photostabilize wood will vary depending on the metal in the coordination complex. We test this hypothesis by treating yellow cedar veneers with different acetylacetonates (Co, Cr, Fe, Mn, Ni, and Ti), exposing veneers to natural weathering in Australia, and measuring changes in properties of treated veneers. The most effective treatments were also tested on yellow cedar panels exposed to the weather in Vancouver, Canada. Nickel, manganese, and titanium acetylacetonates were able to restrict weight and tensile strength losses and delignification of wood veneers during natural weathering. Titanium acetylacetonate was as effective as a reactive UV absorber at reducing the greying of panels exposed to 6 months of natural weathering, and both titanium and manganese acetylacetonates reduced the photo-discoloration of panels finished with a polyurethane coating. We conclude that the effectiveness of metal acetylacetonates at photostabilizing wood varies depending on the metal in the coordination complex, and titanium and manganese acetylacetonate show promise as photoprotective primers for wood.

Syntheses and crystal structures of three [M(acac)2(TMEDA)] complexes (M = Mn, Fe and Zn)

The complexes bis(acetylacetonato-κ2 O,O′)(N,N,N′,N′-tetramethylethylenediamine-κ2 N,N′)manganese(II), [Mn(C5H7O2)2(C6H16N2)], bis(acetylacetonato-κ2 O,O′)(N,N,N′,N′-tetramethylethylenediamine-κ2 N,N′)iron(II), [Fe(C5H7O2)2(C6H16N2)], and bis(acetylacetonato-κ2 O,O′)(N,N,N′,N′-tetramethylethylenediamine-κ2 N,N′)zinc(II), [Zn(C5H7O2)2(C6H16N2)], were synthesized from the reaction of the corresponding metal acetylacetonates [M(acac)2(H2O)2] with N,N,N′,N′-tetramethylethylenediamine (TMEDA) in toluene. Each of the complexes displays a central metal atom which is nearly octahedrally surrounded by two chelating acac and one chelating TMEDA ligand, resulting in an N2O4 coordination set. Despite the chemical similarity of the complex units, the packing patterns for compounds 1–3 are different and thus the crystal structures are not isotypic.

Thermal analysis of halogenated rubber cured with a new cross-linking system

The aim of this work was to examine the influence of new curing agents proposed for brominated butyl rubber (BIIR) on the cross-linking process of rubber compounds and the thermal behavior of the vulcanizates. Rubber blends that were filled with carbon black and contained acetylacetonates of different transition metals in the presence of triethanolamine (TEOA) as new cross-linking agents were prepared. The performed studies showed that metal acetylacetonates (Me(acac)) are effective cross-linking agents for BIIR, which was confirmed by high values of the torque increment (∆M) and significant cross-linking degree of the vulcanizates (α(T)). The most active curing agent seems to be iron acetylacetonate (Fe(acac)). Its application results in a shorter optimal vulcanization time, lower onset vulcanization temperature and similar vulcanization enthalpy compared to the BIIR cured with a sulfur curing system. The BIIR vulcanizates cured with Me(acac) reveal good mechanical properties with tensile strengths in the range of 9–14 MPa and better damping properties comparing to the sulfur-cured rubber. The proposed curing agents do not significantly affect the thermal stability of the BIIR vulcanizates.