The Alkaline Resistance of Waterborne Acrylic Polymer/SiO2 Nanocomposite Coatings.

This study presents a study on the influence of nano-SiO2 on the alkaline resistance of waterborne acrylic coating using some analysis methods such as FT-IR and UV-Vis spectroscopy, combined with FE-SEM analysis and monitoring weight and adhesion changes during exposure to the saturated Ca(OH)2 alkaline environment. The obtained results indicated that the alkaline resistance of acrylic coating enhanced appreciably when adding 2.5 wt% of nano-SiO2. Under the impact of the saturated Ca(OH)2 solution for 20 days of immersion, nanocomposite coating containing 2.5 wt.% of nano-SiO2 was only decreased by 3.6% of the weight and 15.4% of the adhesion, while the neat acrylic coating (without nano-SiO2) seriously reduced 25.4% of the weight and 39.1% of the adhesion.

Crystal structure of two N'-(1-phenyl-benzyl-idene)-2-(thio-phen-3-yl)acetohydrazides.

The synthesis, spectroscopic data, crystal and mol-ecular structures of two N'-(1-phenyl-benzyl-idene)-2-(thio-phen-3-yl)acetohydrazides, namely N'-[1-(4-hy-droxy-phen-yl)benzyl-idene]-2-(thio-phen-3-yl)acetohydrazide, C13H10N2O2S, (3a), and N'-[1-(4-meth-oxy-phen-yl)benzyl-idene]-2-(thio-phen-3-yl)acetohydrazide, C14H14N2O2S, (3b), are described. Both compounds differ in the substituent at the para position of the phenyl ring: -OH for (3a) and -OCH3 for (3b). In (3a), the thio-phene ring is disordered over two orientations with occupancies of 0.762 (3) and 0.238 (3). The configuration about the C=N bond is E. The thio-phene and phenyl rings are inclined by 84.0 (3) and 87.0 (9)° for the major- and minor-occupancy disorder components in (3a), and by 85.89 (12)° in (3b). Although these dihedral angles are similar, the conformation of the linker between the two rings is different [the C-C-C-N torsion angle is -ac for (3a) and -sc for (3b), while the C6-C7-N9-N10 torsion angle is +ap for (3a) and -sp for (3b)]. A common feature in the crystal packing of (3a) and (3b) is the presence of N-H⋯O hydrogen bonds, resulting in the formation of chains of mol-ecules running along the b-axis direction in the case of (3a), or inversion dimers for (3b). The most prominent contributions to the surface contacts are those in which H atoms are involved, as confirmed by an analysis of the Hirshfeld surface.