A corn straw-based lightweight foam material with flame-retardant, antimicrobial, and waterproof properties

Corn straw as a widespread agricultural waste can be used as a raw material to prepare plant fiber-based foam materials, which, however, are susceptible to fire, water, and microbial colonization. In this study, corn straw fibers were surface-modified with Mg–Al-LDH, an inorganic flame retardant, via a simple hydrothermal reaction to become flame-retardant. Silver nanoparticles were attached to the surface of the modified corn straw fibers by the silver mirror reaction to impart antimicrobial properties. The modified corn straw fibers were then subjected to low surface energy treatment with hydrophobicity,1H,1H,2H,2H-PerfluorodecyltriMethoxysilane (TDFS) to impart hydrophobicity. Then, the foaming agent, adhesive (phosphorylated polyvinyl alcohol, PPVA), modified corn straw fibers, and water were mixed in proportion to generate a lightweight foam material. The material was characterized by heat of combustion (HoC) testing, thermogravimetric analysis (TGA), water contact angle (WCA) measurement, antimicrobial tests (inhibition zone method), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The corn straw-based foam material showed excellent flame-retardant and waterproof properties with a WCA of 107°. In addition, the foam material was found highly effective against Aspergillus niger and Botryodiplodia theobromae. This paper presented a novel route of synthesizing light weight plant fiber-based foam material with multi-function, which greatly broadens the application range of agricultural waste, such as the preparation of cushioning materials.