Very High-Char-Yielding Elastomers Based on the Copolymers of a Catechol/Furfurylamine Benzoxazine and Polydimethylsiloxane Oligomers

Main chain-type elastomeric polybenzoxazines (abbreviated as CA-pdms-fu) with very high char yield have been developed. Seven compositions of elastomeric benzoxazine adhesives are synthesized to find the optimum structure by changing the chain length of the siloxane component. The successful synthesis of CA-pdms-fu derived from catechol is confirmed with H-1 NMR and FT-IR spectroscopy. Polymerization characteristics, including polymerization temperature, enthalpy of polymerization, and extent of polymerization for all seven compounds, are analyzed from FT-IR and DSC data. The TGA results indicate remarkable superiority of CA-pdms-fu over traditional epoxy and polyurethane adhesives, with 93% higher char yield than polyurethane elastomer. The flammability of the elastomeric polymer was quantified by heat release capacity using microscale combustion calorimetry (MCC). The seven compositions of elastomeric polybenzoxazines exhibit heat release capacities between 48 and 63 J/g.K, which are within the noncombustible material range, without added flame retardants. Adhesive failure strengths are determined by lap shear strength, making a single lap shear joint on aluminum and copper rectangular bars. The lap shear strength for cross-linked poly(CA-pdms(2)-fu) is comparable to polyurethane adhesives, and the low flammability and very high char yield make this polymer suitable for developing fire-resistant elastomeric materials.

Automated summary

Main chain-type elastomeric polybenzoxazines with very high char yield have been developed by changing the chain length of the siloxane component. The synthesized CA-pdms-fu exhibits remarkable polymerization characteristics and low flammability, making it suitable for developing fire-resistant elastomeric materials.