Microfoamed polyurethanes reinforced with natural fibers

NORMA E. MARCOVICH; ILONA RÁCZ; MIRTA I. ARANGUREN

Buenos Aires, Argentina

Conferencia; Internacional Conference on Science and Technology, COMAT 2005; 2005

There is an ample variety of reactives that can be used in the synthesis of polyurethanes (PU), the possibilities for their formulation are almost unlimited and allow to obtain materials with properties from those of flexible elastomers to rigid crosslinked PU, that can be used as structural materials. Moreover, new materials and composites derived from natural sources rich in cellulose, and offering environmental and economic benefits, are being developed by the automotive, construction, household furniture and packaging industries. A large aspect ratio (fibres), relatively high tensile strength and flexural modulus, low density and low cost contribute to increase the interest of the manufacturers to produce light and low cost composites. It is important that the matrix and reinforcement are compatible or that they co-react in order to ensure a strong interface [1]. PU are compatible with lignocellulosic reinforcements (high -OH concentration), however, vegetable reinforced PU have not been systematically studied and there exist a few references to this respect [2-4]. The objective of this work is to prepare and characterize reinforced foamed PU, that can be used in car interior panels, construction and acustic insulation. A recycled PU and a PU synthesized from a polyalcohol derived from castor oil were used in different formulations, adjusted to obtain different foaming levels. Microfoamed composites with the fibers mostly aligned in one direction, crossed at 90º and at 45º were prepared from long hemp fibers. Also, samples with random arrangement of short wood fibers were prepared varying the average fiber size. The mechanical performance of the reinforced foams were studied through three point bending and dynamic mechanical tests. The morphology of the composites (cell type and diameter, fiber-PU interface) was analyzed by scanning electronic microscopy 1.- Hilijanen-Vainio, M.; Heino, M.; Seppälä, J. V; Polymer, 39: 865-872 (1998) 2.- Li-Chung Chang; Yu Xue; Fu-Hung Hsieh; J Appl Polym Sci 80: 10-19(2001). 3.- Teixeira; Fernandes; Saramago; Rosa; Bordado; Adhesion Sci. Technol., 10, 1111-1127 (1996). 4.- Li-Chung Chang; Yu Xue; Fu-Hung Hsieh; J Appl Polym Sci 81: 2027-2035(2001).