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

Abstract

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 CApdms-fu derived from catechol is confirmed with 1 H 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.

Robust and Direct Route for the Development of Elastomeric Benzoxazine Resins by Copolymerization with Amines

“…They found that the rubber-modified polybenzoxazine was able to protect carbon steel from corrosion. In 2021, Ishida et al 28 have reported the development of high-char-yielding elastomers based on polydimethylsiloxane oligomers functionalized with benzoxazine groups for adhesive applications.…”

Development of an Atomic-Oxygen-Erosion-Resistant, Alumina-Fiber-Reinforced, Fluorinated Polybenzoxazine Composite for Low-Earth Orbital Applications

“…Both degradation temperatures are considered quite high. The char yield, on the other hand, is very low for benzoxazines, particularly for those containing a CF 3 group, which is typically in the range of 36–68% [ 7 , 11 , 12 , 17 , 19 , 23 , 23 , 27 , 34 ], or a furan group, which is typically between 30–74% due to high crosslinking capabilities [ 41 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. The char yield at 800 °C was approximately 24%, which is unexpectedly low for a benzoxazine such as BAF-oda-fu, which contains both above functionalities.…”

Highly Thermally Stable, Reversible, and Flexible Main Chain Type Benzoxazine Hybrid Incorporating Both Polydimethylsiloxane and Double‐Decker Shaped Polyhedral Silsesquioxane Units through Diels–Alder Reaction

“…[9] Attempts have been made to decrease chain mobility of BZ resin to improve its thermal and mechanical properties by incorporating unsaturated (such as allyl or alkynyl) groups, blending with high-performance polymers to form miscible blends, [10][11][12][13][14][15][16] and adding inorganic nanoparticles. [17][18][19][20][21][22] Many organic/inorganic polybenzoxazine (PBZ) hybrids (and other thermosetting resins) have been prepared by incorporating carbon-based materials (e.g., carbon nanotubes, [23][24][25] carbon black, [26] and graphene [27][28][29][30] ) and siliconbased materials [e.g., polydimethylsiloxane (PDMS), [5,[31][32][33] organic modified clay, [34,35] and polyhedral oligomeric silsesquioxane (POSS) [17][18][19][20][21][22][36][37][38][39][40] ]. For example, polymer/POSS hybrids have been obtained from mono-and multifunctionalized POSS derivatives through blending or copolymerization, initially forming organic/inorganic hybrids with only relatively lowmolecular-weight or insoluble cross-linked structures.…”