Bio-based Polyurethane Composites from Macaúba Kernel Oil: Part 2, Wood Thermal Treatment and Composite Water...

Polymer composites are the result of reinforcing a polymeric matrix with other materials. For example, the reinforcement of polyurethanes (PU) with natural fibers is a popular combination because of the great chemical compatibility between the two materials. This work investigates the production of composites using a polyurethane matrix synthesized from macaúba kernel oil and glycerol, reinforced with beech, fir, and carvoeiro. A thermal treatment was applied to the wood reinforcements, and the impact of the thermal treatment on chemical, thermal, and water sorption properties was extensively investigated. The composites prepared exhibited negligible differences in Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA) when compared to the starting PU, showing that the addition of both thermally treated and untreated wood resulted in similar products, with comparable functional groups and thermal stabilities. However, the addition of 2 wt % of thermally treated wood drastically influences the water sorption properties and maximum water uptake under DVS, reaching values several times higher than the unreinforced samples.