Mechanical property of lignin-modified phenolic foam enhanced by whisker silicon

Fibrous and functional structures based on silicon whiskers were modified with a silane coupling agent. They were further used with a phenolic resin (PR) and lignin to produce three types of phenolic foams (PF) upon stirring with foaming agents. The obtained solid foams (LWSPF) were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results indicated that the formation of Si-O bonds in the modified PR improved the characteristics of the foams. Moreover, the introduction of silicon whiskers and lignin made the foam cells smaller and more homogeneous.The char yield of lignin-based PF modified by the silicon whiskers (55.6%) increased by ca. 27% compared with PF. The mechanical properties were optimized at silicon whisker and lignin contents of 0.6% (based on PR weight) and 10% (based on phenol weight), respectively. Compared with PF, the LWSPF bending and compressive strengths increased by 80.5% and 81.1%, respectively.