Abstract. Current challenges highlight the need for polymer research using renewable natural sources as a substitute for petroleum-based polymers. The use of polyols obtained from renewable sources combined with the reuse of industrial residues such as lignin is an important agent in this process. Different compositions of polyurethane-type materials were prepared by combining technical Kraft lignin (TKL) with castor oil (CO) or modified castor oil (MCO1 and MCO2) to increase their reactivity towards diphenylmethane diisocyanate (MDI). The results indicate that lignin increases the glass transition temperature, the crosslinking density and improves the ultimate stress especially for those prepared from MCO2 and 30% lignin content from 8.2 MPa (lignin free) to 23.5 MPa. Scanning electron microscopy (SEM) micrographs of rupture surface after uniaxial tensile tests show ductile-to-brittle transition. The results show the possibility to develop polyurethane-type materials, varying technical grade Kraft lignin content, which cover a wide range of mechanical properties (from large elastic/low Young modulus to brittle/high Young modulus polyurethanes).

In this work we investigated the application of a novel high performance polymer, polybenzoxazine, as a polymeric matrix in Fiber Metal Laminates (FML). This polymer, when applied on the development of FMLs, generated higher mechanical properties in comparison to fiber metal laminates obtained with epoxy. To investigate the mechanical performance of the polybenzoxazine matrix in FMLs, a mechanical behavior comparison was carried out among epoxy matrix laminates - glass fiber reinforced aluminum laminate (GLARE) and carbon fiber reinforced aluminum laminate (CARALL) - and FML constructed with aluminum and carbon fiber reinforced polybenzoxazine. The mechanical properties were characterized by drop weight impact and flexural methods, and the polybenzoxazine curing behavior through differential scanning calorimetry (DSC). Polybenzoxazine FML generated increasing of: 18% of maximum load, 11% of maximum elongation under flexure and 7.5% of impact energy absorption compared to other fiber metal laminates.