Abstract
A novel eco-friendly halogen-free cardanol-based flame retardant with P, Si, and N on the chain backbone (PSNCFR) was synthesized and incorporated into phenolic foams (PFs). PSNCFR was comprehensively investigated via Fourier transform infrared spectroscopy and nuclear magnetic resonance. PSNCFR endowed PFs with flame retardancy, contributed to generating a composite char defense against flames, and efficiently prevented smoking from PFs. PSNCFR introduction improved the flexural strength of the PFs to approximately 155% of that of pristine PF. PSNCFR-modified PFs displayed a high limiting oxygen index value of 41.9%. The results of cone calorimeter show that the mean heat release rate, mean effective heat of combustion, and total heat release of the PSNCFR-modified PFs reduced by 26.92%, 35.71%, and 31.25%, respectively. In particular, the total smoke production of the PSNCFR-modified PFs decreased by 64.55%, indicating excellent smoke inhibition. As for the mechanism, the condensation and gas phases during pyrolysis were responsible for the synergistic flame retardancy in the modified PFs. The findings demonstrate that PSNCFR can be used in PF preparation to overcome their drawbacks of internal brittleness and flammability.
Highlights
Biorenewable resources have attracted significant attention owing to growing concern over environmental problems and energy crisis
To eliminate Phenolic foams (PFs)’s current drawbacks, i.e., the intrinsic brittleness and high flammability, this study examines cardanol as a renewable feedstock to replace phenol in PF s ynthesis[18]
The peaks at 1,217 and 788 cm−1 were assigned to the P=N and P–N stretching v ibration[21,22], and the peak at 957 cm−1 was assigned to PSNCFR-modified PFs shows absorption at cm−1 (P–O–Ph)
Summary
Biorenewable resources have attracted significant attention owing to growing concern over environmental problems and energy crisis. A previous recent study examined cardanol-based[11], in particular, the effect of cardanol on the mechanical characteristics of phenol–formaldehyde formulations and the role of cardanol’s flexible alkyl side chains as plasticizers to enhance the mechanical properties of PFs. the presence of flexible chains of cardanol compromises the flame retardancy of PFs, thereby limiting their use in fields requiring fire resistance. To impart functional properties in cardanol-based PFs, we have incorporated synergistic flame retardant elements into cardanol structures, which can improve the corresponding functional properties of PFs. In this study, a novel cardanol-based flame retardant containing P, Si, and N (PSNCFR) on the chain backbone was synthesized and incorporated into PFs. Owing to its unique chemical structure, PSNCFR imparted. The corresponding toughening and flame-retardant mechanisms are presented
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