Investigation of curing and thermal behavior of benzoxazine and lignin mixtures

Abstract

This article describes the synthesis and characterization of two types of benzoxazine monomers based on phenol or bisphenol, aniline, and formaldehyde. Their characterization was achieved by Fourier transform infrared, 1H‐nuclear magnetic resonance, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Lignin polymer was characterized by infrared, DSC, and TGA. The curing behavior of mixtures of benzoxazine monomers and lignin was investigated by DSC. The mass ratios of benzoxazine monomers/lignin of a series of samples were 100 : 0, 95 : 05, 90 : 10, 85 : 15, 80 : 20, 75 : 25, and 70 : 30. The results indicate that the maximum curing temperatures of the mixtures were lower than that of the pure benzoxazine monomers, and that they decreased with increasing contents of lignin in the mixture. The heat of polymerization (ΔH) of the benzoxazine monomers and lignin mixtures as a function of the mass ratio and the structure of the benzoxazine monomers shows no definite trend. The samples were cured according to the following conditions: 170°C/2h + 200°C/2h and analyzed by DSC and TGA. In all the samples, the glass transition temperature of the benzoxazines increased upon mixing with increasing amounts of lignin. The changes may be due to the formation of a more compact network structure in the mixtures. The thermal stability of the isothermally cured resins is found to be dependent on the mass ratio of benzoxazine/lignin and structure of the benzoxazine monomers. The more lignin in the mixture, the higher is the char yield in the mixture. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Naturally occurring phenolic sources: monomers and polymers

“…Renewable benzoxazine monomers based on reaction of formaldehyde with phenolic -OH from renewable sources such as cardanol, syringol, lignin 427 and ammonia 13 or amine (aniline 428 or diamines 429 and further higher functionality amines 430 ) led to a new class of renewable monomers which undergoes ring opening polymerisation (ROP) to form sustainable polymers.…”

Bisphenol-A benzoxazine and cycloaliphatic epoxy copolymer for composite processing by resin infusion

“…The process and properties of BZ resin can be modified by blending it with different thermoset resins 15 including polyimides, 16 epoxy resins, 17–21 bismaleimides, 22 cyanate esters, 23,24 poly(ε-caprolactone), 25 polydimethylsiloxane, 26,27 dianhydride, 28 and lignin. 29 In particular, blending epoxy with BZ exhibits a great compatibility as the binary system undergoes a hybrid network formation. 30,31 For instance, the copolymerization of BZ with various epoxies resulted in a noticeable change in thermal properties of the copolymer compared to BZ homopolymer.…”

Novel Fully Biobased Benzoxazines from Rosin: Synthesis and Properties

“…Eugenol can be extracted from clove and the fabricated polybenzoxazines with allyl, − and it can participate in ring-opening polymerization to enhance the cross-linking density of the system . Guaiacol is a lignin derivative that is abundant in nature, − and furfurylamine and stearylamine can be derived from furfural and vegetable oil, respectively. Guaiacol condensed with paraformaldehyde and furfurylamine or stearylamine can make two monomers with the copolymer showing better thermal stability than those of the pure polymers .…”