Eco-Friendly Halogen-Free Flame Retardant Cardanol Polyphosphazene Polybenzoxazine Networks

Abstract

We report on the preparation of hexa-functional cardanol (renewable phenolic compound) benzoxazine with a phosphazene core (C PN ) for use as a greener eco-friendly halogen-free flame retardant reactive additive for the formation of sustainable polyphosphazene polybenzoxazine networks for flame resistant applications. The structure and purity of the monomer was confirmed by Fourier transform infrared (FTIR), nuclear magnetic resonance ( 1 H-, 13 C-, 31 P NMR) and gel permeation chromatography studies. The C PN monomer showed good compatibility with benzoxazine monomer (C PN 0) as suggested by the cocuring studies. The thermal properties of the copolymer can be directly tuned by altering the composition of the monomer blend. The occurrence of phosphazene−phosphazane thermal rearrangement is also suggested for the thermal behavior (thermogravimetry analysis) at higher loading of C PN in the monomer feed ratio. An improvement in mechanical properties of the copolymer with increase in glass transition temperature was confirmed by enhancement in cross-link density as compared to neat polybenzoxazine. The reactive nature and presence of phosphazene core improved both the smoke density rating, vertical burning rating and led to higher limiting oxygen index. The FTIR and scanning electron microscopy studies of residual char supported the formation of functionalities and morphologies favorable to support the flame resistance behavior of polymer by incorporation of reactive benzoxazine with phosphazene core. Finally, we demonstrate that incorporation of cardanol phosphazene network has good compatibility with the polybenzoxazine phenolic thermosets with improvement in flame retardancy. The higher cardanol (65.7%) and phosphorus content (3.4%) and reactive nature of synthesized compound is attractive as a sustainable additive with the scope of their utilization with other polymeric resins.

Cardanol Benzoxazines: A Versatile Monomer with Advancing Applications

“…Incorporation of 10 wt% C‐PN in C‐trisapm showed an increase in T g value from 100 to 120 °C which is attributed to the higher oxazine functionality of C‐PN assisting in the extension of cross‐link network formation during copolymerization. The copolymer composite revealed an improved thermal stability, LOI value, V‐0 rating with a simultaneous lowering in smoke density ratings supporting higher flame resistance characteristics …”

“…The copolymer composite revealed an improved thermal stability, LOI value, V0 rating with a simul taneous lowering in smoke density ratings supporting higher flame resistance characteristics. [45] A sustainable onestep strategy toward lowtemperature cur able superparamagnetic composite based on smartly designed iron nanoparticles (IONPs) and Ctrisapm showed a pivotal role of capping agent in allowing their uniform dispersion in polymer (as supported by atomic force microscopy, Figure 9), with profound lowering of cure temperature (≈143 °C) of neat Ctrisapm. The studies also revealed the existence of oxidative polymerization along with conventional modes of ROP of the monomer.…”

“…The degree of oxazine functionality in the monomer revealed a significant effect on the thermo‐mechanical properties of the so‐formed PBz. A modification of synthetic strategy allowed the formation of hexa‐benzoxazine, where six cardanol units condensed with a phosphazene core to form the C‐PN monomer to advance cardanol PBz networks in flame retardant applications …”

“…A modification of synthetic strategy allowed the formation of hexabenzoxazine, where six cardanol units condensed with a phosphazene core to form the CPN mon omer to advance cardanol PBz networks in flame retardant applications. [45] In all the above approaches, the phenol component is the same, that is, cardanol. Interestingly, an approach of introduc tion of cardanol on one end of benzoxazine and vanillin on the other end is also reported, type monomer (C,Ceda).…”

Polypropylene/phosphazene nanotube nanocomposites: Thermal, mechanical, and flame retardation studies

“…[35] Recently, phosphazene nanotubes (PZS) filled epoxy and polybenzoxazine nanocomposites have been reported with significant improvements in flame retardation and mechanical properties as compared to the pristine polymers. [36][37][38][39] However, PZS has not been explored as a reinforcement for polyolefins, such as PP and polyethylene, to modify their properties.…”