Abstract
With the aim of obtaining halogen-free polybenzoxazazines with reduced flammability, phosphazene-containing benzoxazines (PhBZ) were synthesized in a two-stage method. In the first stage of the reaction of hexachlorocycotriphosphazene with bisphenol A at molar ratios of 1:12, 1:16, and 1:24, respectively, mixtures of bisphenol and hydroxyaryloxycyclotriphosphazenes were obtained, which mainly contained P3N3[OC6H4C(CH3)3C6H4OH]6. In the second stage, when these mixtures interacted with aniline and an excess of paraformaldehyde in toluene at 80–90 °C, PhBZ containing 20–50% of the phosphazene component with Mw 1200–5800 were formed. According to 1H and 13C NMR spectroscopy, PhBZ contain a small amount of oligomeric compounds with Mannich aminomethylene bridges. With an increase of the content of the phosphazene component, the curing temperature of PhBZ decreases from 242 °C to 215 °C. Cured PhBZ samples with a phosphorus content of more than 1.5% have increased flammability resistance according to UL-94.
Highlights
Polybenzoxazines (PBZ) are a relatively new class of polymers obtained by thermal ring-opening polymerization of monomeric and oligomeric compounds with oxazine rings without the release of volatile byproducts, which is the main advantage of this class of compounds [1]
Over the past 20 years, great success has been achieved in the field of the molecular design of benzoxazines; in particular, functional groups such as allyl [5], maleimide [6], carboxyl [7], propargyl [8], and cyanate ester [9], nitrile [10] and others have been introduced into the structure of these monomers
Was necessary to develop a synthesis method that would ensure a high yield of oxazine compounds without a purification was necessary to develop a synthesis method that would a high of oxazine compounds necessary to develop a step
Summary
Polybenzoxazines (PBZ) are a relatively new class of polymers obtained by thermal ring-opening polymerization of monomeric and oligomeric compounds with oxazine rings without the release of volatile byproducts, which is the main advantage of this class of compounds [1]. Due to the formation of hydrogen bonds in the polymer [2], PBZs have good physicomechanical properties, low water absorption [3], and practically zero curing shrinkage [4]. One of the methods for the modification of PBZ is the introduction into the structure of the initial monomers of organoelement polyfunctional fragments [11], which increase thermal stability and fire resistance. The introduction of polyhedral oligosiloxanes into the structure of PBZs, along with an increase in thermal stability, contributes to the improvement of the their dielectric properties [12]
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