CONICET | Buscador de Institutos y Recursos Humanos

This work was focused in the production and characterization of microfoamed polyurethane composites reinforced with pine wood flour (WF) that can be used in car interior panels construction and acoustic insulation. A crosslinked PU, formulated from a recycled polyol was used as matrix. The source of isocyanate groups utilized was a polymeric MDI, for easy handling of the reactants and reinforcements. Two series of composites were formulated: set A was prepared with an Index = 1.00 (NCO to OH groups from polyol component) for all WF concentrations, and for set B, the Index was varied linearly from 1.00 (unreinforced foam) up to 1.25 (20% reinforced foam). The mechanical performance of the reinforced foams was studied through three point bending and dynamic mechanical tests. Flexural ultimate strength and modulus increase with filler concentration, although foams corresponding to series B exhibit higher values than the composites of series A. Storage modulus also increases with WF content and the changes are more noticeable in the rubbery region, where the contribution of the matrix is small. The glass transition temperature (related to the position of the maximum in the tan δ peak) of the composites is slightly lower than that of the matrix, probably because the filler still contains some moisture. The storage modulus and glass transition temperature for the A series composites are lower than those of the B series. These results would signify that wood flour takes part in the chemical reaction, leading to a more rigid polyurethane. Flammability was studied by comparing the behavior of the composites with that of control samples prepared with 25% of Al(OH)3 as flame retardant. The addition of Al(OH)3 did not reduce the flammability of more diluted samples, although some differences were found for the case of composites prepared with 20% WF.