Mirna Alejandra Mosiewicki

Polyurethane Foams Obtained from Castor Oil-based Polyol and Filled with Wood Flour:

A natural polyol was prepared from castor oil by alcoholysis with triethanolamine. The oil and the oil-based polyol were characterized by infrared spectroscopy and through the analytical determination of their functional groups, both techniques indicating that the hydroxyl content increased significantly after the alcoholysis reaction. The modified oil was subsequently used as the polyol component in the formulation of rigid polyurethane foams. Wood flour was chosen to be incorporated as filler in these materials. Physical, thermal, and mechanical properties of the neat and reinforced foams were measured, analyzed, and compared to a reference commercial system. The chemical reaction between wood flour and isocyanate strongly affected the composites’ response to thermo-gravimetric tests. Compression modulus and yield strength decreased as wood flour content increased. The effect of the foam density on the compression properties was also investigated.

Moisture dependence of the properties of composites made from tung oil based polyurethane and wood flour

Natural composites prepared from a polyurethane (PU) based on tung oil and different percentages of wood flour (WF) or microcellulose (MC) were exposed to humid environments and the resulting changes of their properties were evaluated. The equilibrium moisture content of the composites increased with the wood flour percentage. Dynamic mechanical tests performed during temperature scans revealed the changes resulting from moisture absorption on the main transition temperature of the matrix as well as on the storage modulus. The tensile mechanical properties of the materials were also strongly affected by moisture. The different degree of dispersion achieved during the incorporation of WF and MC into the matrix was considered the main reason for the different effect of each filler on the thermal and mechanical properties of the resulting composites.

Vegetable Oil Based-Polymers Reinforced with Wood Flour

Liquid polymer precursors were synthesized from vegetable oils to be utilized in the preparation of oil based-resins to be later reinforced with a filler also obtained from natural sources. In this work, an unsaturated oil, tung oil, produced in the region was selected as raw material. The vegetable oil was chemically functionalized to obtain a polyol to be further used in polyurethane formulations. Different analysis techniques were used to investigate the hydroxyl content in the modified oil. Oil based composites containing pine wood flour as filler were prepared and mechanically tested.

17 – Mechanical performance of polyurethane (PU)-based biocomposites

Abstract Polyurethanes (PUs) are versatile polymers that have found ample variety of applications in quite different fields, including foams (flexible cushions as well as rigid heat insulators), construction, adhesives, gaskets and coatings, as well as medical devices. The facility of handling the formulation is the main reason for complying with such a wide range of properties, in particular mechanical properties. As the natural fiber composites appeared in the world, PUs were also incorporated to the list of matrices that could be used and benefit from the addition of lignocellulosics. The chemical nature of these polymers is certainly an asset, since little (many times none) fiber modification is needed to obtain good interfacial adhesion. Enough to say that the highly hydroxylated vegetable material is capable of interacting with the polar groups of the PU or reacting with the isocyanate groups if the polymerization is carried out in situ. This chapter is presenting an overview on the mechanical properties of natural fiber (and particle) composites having synthetic and biobased PU matrices.