Evaluation of water absorption in sugarcane fiber composites with and without nanoparticles by passive thermography

The use of natural fibers in the manufacture of composites has gained prominence due to their sustainability, low cost, and application in several areas of engineering. However, the high moisture absorption of lignocellulosic fibers still represents a significant limitation, compromising their mechanical performance and durability. This study aims to investigate the hygroscopic behavior of sugarcane bagasse composites, with and without applying a nanoparticle-based spray, using the non-destructive technique of passive infrared thermography. For this purpose, samples produced with polyurethane resin based on castor oil were tested by applying droplets of distilled water on their top surfaces. Water absorption was monitored over time using an infrared camera. A precision balance was used to measure water absorption of both samples. The results showed that the sample treated with nanoparticles presented a 28.74 \% lower average water absorption rate compared with the untreated sample. However, both samples absorbed approximately the same amount of water, indicating that the nanoparticles only delayed the absorption process. The treated sample presented an absorption time of 13 h 48 min, while the untreated sample presented an absorption time of 19 h 21 min, with the cold region remaining on the surface for longer. The thermal analysis was associated with sample morphology and the thermal behavior of monitored regions. The proposed approach is promising because it combines sustainable materials with advanced and non-destructive characterization techniques. This study contributes by demonstrating the applicability of infrared thermography in evaluating the effectiveness of hydrophobic treatments in natural composites.