Dynamic mechanical study on multilayer core-shell latex for damping applications

Multilayer core-shell poly (styrene-butyl acrylate) latex particles were synthesized via semi-continuous emulsion polymerization, and the process was monitored by a dynamic laser scattering (DLS). The layers of the latex particles were designed to have progressively decreasing glass transition temperatures (T-g) from the core (layer 1) to the outmost shell (layer 4), which was achieved by varying the mass ratio of butyl acrylate (BA) to styrene (St) in the synthesis of each layer. Divinylbenzene (DVB) was added as the crosslinking agent in each layer except for the outmost layer in order to ensure that a continuous film can be formed at room temperature. The damping properties of the formed films as well as the influences of synthesis variables, including the content of DVB added in the internal layers (i.e., layers 1, 2, and 3), the total mass ratio and sequence between layers 3 and 4, and the T-g of each layer were studied by dynamic mechanical analysis (DMA). The results showed that four-layer core-shell latex particles with proper DVB content in each layer exhibited the best damping properties, with a broad effective damping range (tan delta > 0.3) ranging from -12.0 degrees C to 97.2 degrees C. The widening of the clamping peak can be explained by the formation of a gradient IPN structure in latex particles. Furthermore, the morphology of the formed films was studied by AFM in tapping mode. (C) 2012 Elsevier B.V. All rights reserved.