Preparation and Characterization of Tung Oil Toughened Modified Phenolic Foams with Enhanced Mechanical Properties and Smoke Suppression

In this study, we prepared a series of tung oil phenolic foams (TPF) by a one-pot method. The FT-IR and H-1 NMR spectra confirm the successful Friedel-Crafts grafting of phenol to the long-chain alkyl group in tung oil. Modified TPFs exhibit enhanced mechanical properties, including compressive and flexural strengths of up to 0.278 +/- 0.036 MPa and 0.450 +/- 0.017 MPa, respectively, which represent increases of 68.75% and 86.72% over those of pure phenolic foam (PF). SEM spectra reveal the TPF microstructure to have uniform hexagonal cell morphology, narrower cell size distribution, and smaller mean cell size, suggesting enhanced mechanical properties. The TPF total smoke release decreased by 74.23%, indicating that the long alkyl chain significantly improves smoke suppression of the combusting foam. However, due to the flammability of the alkyl chains, the TPF limiting oxygen index decreases with increasing tung oil content. Moreover, TPF exhibits reduced thermal stability and high-temperature charring rate, elevated peak and mean heat release rates, and higher total heat release compared with pure PF. Therefore, future research will focus on the use of tung oil modified flame retardant to provide more robust phenolic foams.