Simple model to estimate adhesion of structural bonding during humid ageing

International audienceA structural epoxy adhesive has been studied under humid ageing conditions, both as a bulk polymer and as an adhesive, in torsional and cleavage (wedge) tests. Diffusion of water within the polymer, as measured by gravimetry, was found to be in good agreement with the Carter and Kibler model. Physical properties decreased with increasing water content. A correlation was found between the decrease of bulk and adhesive joint properties. Fracture surfaces have also been explained using the Carter and Kibler model. Given the various types of failure, the extent of each depending on time of immersion, a simple model is proposed to estimate overall energy of adhesion, G* (an effective average linked to three distinct types of failure), as a function of ageing time

A new pigment type: Colored diblock copolymer-mica composites

cited By 26International audienceNew mica-polymer composite pigments have been prepared and characterized. The pigments are prepared from mica surfaces by block copolymerization of butyl acrylate (BA) and a mixture of styrene (S) and a modified alizarin (A; dye). This is performed after physical adsorption of a radical initiator with a cationic group. Some of the copolymer was desorbed from the surface and characterized by 1H NMR, size exclusion chromatography, and UV-visible spectroscopy. This desorbed copolymer fraction had a number-average molecular weight of 140 000 g·mol-1 with chemical compositions of 16% and 84% M, respectively, of poly(butyl acrylate) (PBA) and poly(styrene-alizarin) [P(S-A)]. In addition, it had a yellow coloration when in the bulk form. The remaining mica composites were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. It was found that 0.07 molecules of block copolymer per nm 2 of mica remained adsorbed on the mica surface. This leads to a surprising pink color, which may be explained by the basicity of the mica surface due to the pH-color-sensitive character of the alizarin dye. © 2005 American Chemical Society