This study presents the development of hybrid composites using waste krajood fibers and isocyanate adhesive for sustainable building applications. The influence of fiber size (short, long, and mixed) and fiber-to-adhesive ratios (90/10, 85/15, and 80/20 wt%) on mechanical, physical, thermal, surface morphology, water resistance, acoustic, and flame-retardant properties was investigated. The use of mixed fiber sizes improved fiber packing efficiency, resulting in better dimensional stability and a smoother surface profile. In particular, the M80I20 composite showed the minimum water absorption and thickness swelling, while maintaining adequate strength. All composites achieved LOI values above 27%, classifying them as flame-retardant, with the S90I10 sample reaching the highest LOI of 51.02%. Acoustic tests showed that the M90I10 composite had the highest noise reduction coefficient (NRC = 0.76), absorbing up to 76% of incident sound at 2000 Hz. These findings indicate that krajood fiber-based hybrid composites are suitable for use as eco-friendly building materials, especially for wall and ceiling panels requiring resistance to moisture, sound absorption, and flame retardancy. Incorporating agricultural residues with binders supports sustainable construction and the principles of a circular economy.
Sookyung et al. (2026) studied this question.