Bio-Based Rigid Polyurethane Foam Composites Reinforced with Bleached Curauá Fiber

This study aims to evaluate the influence of using a bleached Curauá fiber (CF) as filler in a novel rigid polyurethane foam (RPUF) composite. The influence of 0.1, 0.5 and 1 wt.% of the reinforcements on the processing characteristics, cellular structure, mechanical, dynamic-mechanical, thermal, and flame behaviors were assessed and discussed for RPUF freely expanded. The results showed that the use of 0.5 wt.% of CF resulted in RPUF with smoother cell structure with low differences on the processing times and viscosity for the filled pre-polyol. These morphological features were responsible for the gains in mechanical properties, in both parallel and perpendicular rise directions, and better viscoelastic characteristics. Despite the gains, higher thermal conductivity and lower flammability were reported for the developed RPUF composites, related to the high content of cellulose and hemicellulose on the bleached CF chemical composition. This work shows the possibility of using a Brazilian vegetable fiber, with low exploration for the manufacturing of composite materials with improved properties. The developed RPUF presents high applicability as enhanced cores for the manufacturing of structural sandwich panels, mainly used in civil, aircraft, and marine industries.

Rigid bio-based wood/polyurethane foam composites expanded under confinement

Rigid polyurethane biofoams (RPUF) were produced by single shot-method using a bio-based polyol and 10 wt% of pinewood particles. Two different confinement degrees were investigated (70% and 50% of the free-rising volume), along with a control group produced under free-rising. RPUF were studied using SEM images (to estimate average foam cell size and anisotropy index), mechanical testing (under compression and tension), apparent density, and thermal conductivity analysis. The results were statistically evaluated using ANOVA tests prior to means tests. The RPUF produced under confinement showed more rounded and homogeneous cell structures compared to those freely expanded. The filled RPUF produced under a confinement degree of 50% yielded very high compressive and tensile strengths, whereas thermal conductivity decreased with confinement.