Ablation properties of zinc borate and aluminum hypophosphite filled silicone rubber composites

Abstract

The ablative properties of epoxy modified silicone rubber composites filled with zinc borate (ZB) and aluminum hypophosphite (AHP) were studied. The decomposition of the added fillers and covering connection of residual on the substrate contribute to the improvement of heat insulation. The ablation test shows that the formation of a dense char layer with certain strength is key to improving the ablative properties. The optimal ablative performance is achieved when the concentration of ZB and AHP is 10 and 5 phr, respectively. Under such circumstances, the linear ablation rate is as low as 0.032 mm/s, which is about 61% lower than the pure silicone rubber. Furthermore, the structure and composition of the formed char layer were analyzed using X‐ray diffraction analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy.

Effects of Fluorinated Side Groups on the Insulation Performances of Polyphosphazenes with Organic Fiber Reinforcement

“…20−22 Unfortunately, most flame retardants could not promote the promotion of the interaction between the charred layer and the nether virgin insulation materials, implying the flaming gas scouring could make the charred layer peel out from the substrate easily which may lead to further erosion of the substrate and thermal protection failure in severe cases. 23,24 Therefore, structural modification of elastomers is a more ideal method to obtain the expected flame-retardant properties. Benefiting from the adjustability of substituents and controllability of combination properties in the structural design and preparation of polyphosphazene, it is significant to consider that utilizing PBPP's structural modification balances the lowtemperature resistance and ablation properties of PDAP.…”

“…Drawing on the improving ablation resistance techniques of traditional organic rubber insulation materials, the ablation performance of the traditional EHSM can be effectively improved by the flame-retardant modification of the structure and addition of flame retardants . Like ammonium polyphosphate, boron compounds, and polyhedral oligomeric siloxanes, these flame-retardant fillers could promote the carbonization of organic cracking fragments by retarding oxidation and enhance the strength and density of the charred layer via ceramic reactions, which would help to improve the ablation performance of insulating materials. − Unfortunately, most flame retardants could not promote the promotion of the interaction between the charred layer and the nether virgin insulation materials, implying the flaming gas scouring could make the charred layer peel out from the substrate easily which may lead to further erosion of the substrate and thermal protection failure in severe cases. , Therefore, structural modification of elastomers is a more ideal method to obtain the expected flame-retardant properties. Benefiting from the adjustability of substituents and controllability of combination properties in the structural design and preparation of polyphosphazene, it is significant to consider that utilizing PBPP’s structural modification balances the low-temperature resistance and ablation properties of PDAP.…”

Flexible Thermal Protection Polymeric Materials with Self-Sensing and Self-Adaptation Deformation Abilities

“…Among the various polymers, silicone rubber (SR) has been evidenced as a promising flexible TPS material because SR retains the inherent properties of the polymer at room temperature, and its remarkable flexibility offers the possibility of large deformation while providing excellent ablation resistance by ceramization at high temperatures. − In addition, it tends to exhibit a higher oxidation resistance and superior heat resistance than the other rubbers due to its unique structure with −Si–O– bonds in the backbone, which makes it a reliable choice for external thermal protection applications. − However, pure SR has difficulty in forming a stable char layer and requires improved possibilities for survival in representative heat flux environments. , Although high elongation at break and flexibility make large deformation possible, they also lack the ability to deform adaptively in response to the environment. Exploring the way of self-adaptive deformation and ablation resistance strengthening and the synergistic enhancement mechanism can provide novel strategies and material systems for dynamic thermal protection of high-speed morphing aircraft.…”