AbstractThe utilization of kapok husk (KH) as a reinforcing filler can enhance the properties of soy protein isolate (SPI)/kapok husk (KH) films. The properties of soy protein isolate/kapok husk films with and without the cross-linking agent glutaraldehyde (GLA) were investigated. Films with different KH contents were prepared through a solvent casting method. The addition of KH to SPI films increased the tensile strength, modulus of elasticity, and thermal stability, but reduced the elongation at break. The presence of glutaraldehyde improved the tensile and thermal properties of SPI/KH films. The tensile strength of modified SPI/KH films at 40 wt% increased by 30% compared to unmodified films. The improvement of interfacial interaction between the KH and SPI was demonstrated using a morphology study. Fourier transmission infrared spectroscopy (FTIR) analysis indicated the presence of ethylenic (C=C) groups and imine (C=N) groups. An enzymatic degradation test of SPI/KH films was performed for 14 days in a diatase buffer solution at 37 °C. The enzymatic degradation weight loss of unmodified films decreased with increasing KH content. In contrast, the modified SPI/KH films with glutaraldehyde retained about 50% of their original weight.