Microfoamed polyurethanes reinforced with natural fibers

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

Buenos Aires, Argentina

Conferencia; Internacional Conference on Composite Materials, COMAT 2005; 2005

Internacional Conference on Composite Materials, COMAT 2005, Buenos Aires, Argentina, 11 al 14 de diciembre de 2005. 2 páginas Polyurethanes (PU) can be synthesized from an ample variety of reactants, the possibilities for their formulation are almost unlimited. Different materials can be prepared with properties ranging 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. Plant fibers present large aspect ratios, relatively high tensile strength and flexural modulus, low density and low cost, which contribute to increase the interest of the manufacturers to produce light and low cost composites. It is important that matrix and reinforcement are compatible or that they co-react in order to ensure a strong interface [1] and PUs are compatible with lignocellulosic reinforcements (high ?OH concentration). However, vegetable reinforced PUs have not been systematically studied and there exist a few references to this respect [2-4]. In this work, reinforced foamed PUs that can be used in car interior panels, construction and acoustic insulation were prepared and characterized. Two different polyols were used for the PU synthesis: a recycled one with OH value of 270 mgKOH/g provided from (PEMÜ Co, Hungary) and another derived from castor oil (Parafarm®, Argentina) through alcoholysis, OH value = 449 mgKOH/g. The isocyanate crosslinker was a 4,4?-diphenylmethane diisocyanate (MDI) prepolymer (Rubinate 5005, Huntsman Polyurethanes, USA) with an equivalent weight of 131 g/eq. Humidity content coming from polyol and vegetable reinforcements was enough to generate foaming. In some samples, extra water (foaming agent) was purposely added to the formulation. Wood fibers and wood flour from pine, and hemp fibers, were selected as reinforcements / reactive fillers. Before being incorporated, the reinforcements were dried at 110°C overnight.