**8. Phloroglucinol based polybenzoxazine for flame retardant applications**

Phloroglucinol (P) is also a kind of bio-based renewable phenolic material widely occurred in greenery plants, and it contains three phenolic hydroxyl groups can form a three-arm benzoxazine monomer, which possibly increase the crosslinking density of cured PBz resin result in higher thermal stability, mechanical behaviour and other properties. Zuomin Zhan et al. reported [81] the development of fully bio-based low temperature cured polybenzoxazines. In order to achieve high thermal stability, bio-mass-derived phloroglucinol (P) as phenol source, furfurylamine (FA) or P-amino benzoic acid (PABA) as amine source and paraformaldehyde were used to synthesize two novel fully bio-based benzoxazines (**Figure 24**). The obtained fully bio-based polybenzoxazines possesses a high char yield of 53.0%, low HRC of 37 J/gK and a low THR of 8.3 kJ/g.

heat release values. Though, TPHRR1 of P(Ppaba) was about 300°C, signifying again that the degradation of benzoxazine diminished without Mannich structure formation. In comparison with P(P-paba), HRC value of 37 J/gK, THR value of 8.3 kJ/g and PHRRs value of 37.75 W/g and 21.84 W/g of P(P-fa) diminished considerably, and merely 20–35% of those of P(BA-a), specifying that the presence of furan group could enhance the additional cross-linking density and greatly decrease the heat release of fully bio-based sustainable benzoxazine resins. Thus, it may possibly be expected that P(P-paba) and P(P-fa) had possesses best flame

*Thermal and flame retardant properties of bio-based phloroglucinolbased tri-functional polybenzoxazines.*

In the present chapter, we have reviewed the synthesis of bio-based benzoxazine monomers with varying molecular design including mono, di, tri, tetra, hexa, and octa functional oxazine using renewable bio based raw materials such as cardanol, eugenol, guaiacol, vanillin, phloroglucinol, naringenin, apigenin, resveratrol, furfurylamine, stearylamine and etc. The present chapter also discusses the preparation of polybenzoxazine bio-composites using bio-silica, silica particle through sol–gel approach and boron complexes and their thermal and flame resistant properties using various characterization techniques including LOI, UL-94 vertical flame test, smoke density, SEM analysis, and MCC. Data obtained from the thermal and

flame resistant analysis, the newly developed resveratrol, phloroglucinol,

naringenin, apigenin based multi-functional benzoxazine has greatest prospective applications as anti-flammable and fire resistant matrix for advanced composites for several applications. Especially, the HRC and TRC value of poly(RES-ac) is ominously lower than that of the thermosets from ortho-amide and ortho-imide benzoxazines, which exhibited one of the lowest HRC values of all polymers. Thus, this newly developed resveratrol-based tri-benzoxazine monomer containing acetylene group has greatest prospective applications as anti-flammable and fire resistant matrix for advanced composites. Consequently, these developments might be very useful in fabricating new products for the next generation's high-performance and flame retardant uses by exploiting eco-friendly, sustainable and cost competitive bio-based polybenzoxazine matrices and composites for varying range of

resistant behaviour than that of P(BA-a).

industrial and engineering applications.

**59**

**9. Summary and conclusion**

**Sample Char**

*DOI: http://dx.doi.org/10.5772/intechopen.98470*

P(P-fa (9.5) + P-paba

(0.5))

**Table 6.**

**residue (%)**

**HRC (J/ gK)**

**THR (KJ/ g)**

*Development of Halogen Free Sustainable Polybenzoxazine Matrices and Composites for Flame…*

P(P-fa) 53 37 8.3 37.8 348 21.8 441 [81]

P(P-fa (9) + P-paba (1)) 53.3 38 9.2 34.0 312 22.3 454 [81] P(P-fa (8) + P-paba (2)) 50.3 45 9.8 39.7 305 23 465 [81] P(P-paba) 34.7 86 12.3 79.6 300 39.6 528 [81] P(BA-a) 30.6 169 23.6 166.6 448 94.0 519 [81]

**PHRR1 (W/g)** **TPHRR1 (°C)**

52 39 9.4 34.5 323 22.9 441 [81]

**PHRR2 (W/g)**

**TPHRR2 (°C)**

**Reference**

The key combustion parameters, including HRC, THR, PHRR and TPHRR, were obtained and summarized in **Table 6**. MCC curves of all system exhibited dissimilar two heat release peaks. HRC, THR and PHRRs of P(P-paba) were 86 J/gK, 12.3 kJ/g, 79.6 W/g and 39.6 W/g respectively and only about half of P(BA-a) (169.0 J/gK, 23.6 kJ/g, 166.6 W/g and 94.0 W/g). Its TPHRR2 (528°C) was 9°C higher than that of P(BA-a) (519°C). These consequences were ascertained that the formation of H-bonding in the molecular structure of P(P-paba) might effectively diminish the

**Figure 24.** *Synthesis phloroglucinol based benzoxazine monomers (P-fa and P-paba).*

*Development of Halogen Free Sustainable Polybenzoxazine Matrices and Composites for Flame… DOI: http://dx.doi.org/10.5772/intechopen.98470*


**Table 6.**

flame resistance properties attained upon polymerization of ortho-imide and ortho-amide functionalized benzoxazine monomers. These results show that poly (NAR-fa) can indeed be classified as non-ignitable given that its HRC is lower than

*Flame Retardant and Thermally Insulating Polymers*

**8. Phloroglucinol based polybenzoxazine for flame retardant**

Phloroglucinol (P) is also a kind of bio-based renewable phenolic material widely occurred in greenery plants, and it contains three phenolic hydroxyl groups can form a three-arm benzoxazine monomer, which possibly increase the crosslinking density of cured PBz resin result in higher thermal stability, mechanical behaviour and other properties. Zuomin Zhan et al. reported [81] the development of fully bio-based low temperature cured polybenzoxazines. In order to achieve high thermal stability, bio-mass-derived phloroglucinol (P) as phenol source, furfurylamine (FA) or P-amino benzoic acid (PABA) as amine source and

paraformaldehyde were used to synthesize two novel fully bio-based benzoxazines (**Figure 24**). The obtained fully bio-based polybenzoxazines possesses a high char

The key combustion parameters, including HRC, THR, PHRR and TPHRR, were obtained and summarized in **Table 6**. MCC curves of all system exhibited dissimilar two heat release peaks. HRC, THR and PHRRs of P(P-paba) were 86 J/gK, 12.3 kJ/g, 79.6 W/g and 39.6 W/g respectively and only about half of P(BA-a) (169.0 J/gK, 23.6 kJ/g, 166.6 W/g and 94.0 W/g). Its TPHRR2 (528°C) was 9°C higher than that of P(BA-a) (519°C). These consequences were ascertained that the formation of H-bonding in the molecular structure of P(P-paba) might effectively diminish the

yield of 53.0%, low HRC of 37 J/gK and a low THR of 8.3 kJ/g.

*Synthesis phloroglucinol based benzoxazine monomers (P-fa and P-paba).*

100 J/gK.

**Figure 24.**

**58**

**applications**

*Thermal and flame retardant properties of bio-based phloroglucinolbased tri-functional polybenzoxazines.*

heat release values. Though, TPHRR1 of P(Ppaba) was about 300°C, signifying again that the degradation of benzoxazine diminished without Mannich structure formation. In comparison with P(P-paba), HRC value of 37 J/gK, THR value of 8.3 kJ/g and PHRRs value of 37.75 W/g and 21.84 W/g of P(P-fa) diminished considerably, and merely 20–35% of those of P(BA-a), specifying that the presence of furan group could enhance the additional cross-linking density and greatly decrease the heat release of fully bio-based sustainable benzoxazine resins. Thus, it may possibly be expected that P(P-paba) and P(P-fa) had possesses best flame resistant behaviour than that of P(BA-a).
