Promoted ablation resistance of polydimethylsiloxane via crosslinking with multi-ethoxy POSS

In this article, ammonium polyphosphate (APP) and ammonium pentaborate (APB) were introduced to liquid silicone rubber with an aim of building richporous char structure in situ, thereby improving thermal insulation properties. Thermogravimetric analyses indicated that the incorporation of APP greatly increased the char residue of the composites. Oxy-acetylene torch tests showed that the addition of either APP or APB powders effectively enhanced the ablation resistance of the composites, whereas Shore A hardness tests revealed that the APP-containing composites exhibited a higher hardness than APB-filled counterparts. The linear ablation rates of composites with 40 phr APP or APB were reduced by 34.16% and 36.19%, respectively, when compared with the control sample. The maximum back-face temperatures of composites with 40 phr APP or APB was reduced to as low as 73 C. The APP-containing composites exhibited superior ablation resistance, considering both the linear ablation rate and the mechanical properties of char layer. In addition to SiO 2 , SiC, and C, B 2 O 3 was produced in the APB composites, as characterized by XRD and Raman analysis. Combined with SEM, it was proven that the formation of a firm, continuous, rich-porous and thermal insulation char layer was advantageous to improve the ablation and insulation properties.

Section: Introductionmentioning

confidence: 99%

Improving ablation properties of liquid silicone rubber composites by in situ construction of rich‐porous char layer

Yan

Zhang

Zhou

et al. 2020

“…They further suggested the mechanism that the carbon fiber acted as a shield at the surface and aramid fiber consolidated inside and form a skeleton. Other fillers like boron‐based fillers, wollastonite fillers, epoxy phenolic resin fillers, multi‐ethoxy POSS were also verified effective on the ablation performance 7,19–21 . However, most of the reported studies on improving the ablative property of EPDM are emphasized on inorganic fillers, such as carbon‐based fillers and silicon‐based fillers.…”

Section: Introductionmentioning

confidence: 99%

Effect of hybrid cross‐linked polyphosphazene microspheres on ablative and mechanical properties of ethylene propylene diene monomer

Chen

He²,

Liu

et al. 2021

Polymeric ablative materials (PAMs) are widely used in spacecraft currently for thermal insulation. However, it is challenging to find a single filler that can improve both ablative and mechanical properties of PAMs. In this study, a new type of hybrid cross‐linked polyphosphazene microspheres (PHC) is added to ethylene propylene diene monomer (EPDM) composites as a filler for the first time and its influence on the ablation, mechanical, and thermal properties of EPDM is investigated. The results show that the addition of 3 phr PHC increases the ablation performance by about 10% and enhances the mechanical properties by 20% approximately. In addition, the ablation mechanism is studied in accordance with SEM, FTIR, and Raman spectroscopy. On the one hand, PHC has the effect of catalyzing carbonization, thus increasing the rate of residual carbon; on the other hand, PHC changes the morphology of the char layer, forming a cross‐linked structure containing P─O─Si bonds on the surface. The findings regarding catalyzing carbonization and the special char layer structure could guide the design of ablative materials.

“…Thermogravimetric analysis (TGA) is a very important strategy for evaluating the heat resistance of materials. [14][15][16][17][18][19] Increasing the high temperature char yield of materials is of great significance for improving the ablation resistance of materials. [18] Martin et al [3] synthesized boron-containing novolac resins by chemically modifying a commercial novolac resin with bis(benzo-1,3,2-dioxaborolanyl)oxide (a) and bis(4,4,5,5tetramethyl-1,3,2-dioxaborolanyl)oxide (b) to obtain various boron-modified novolac resins.…”

Section: Introductionmentioning

confidence: 99%

“…[14][15][16][17][18][19] Increasing the high temperature char yield of materials is of great significance for improving the ablation resistance of materials. [18] Martin et al [3] synthesized boron-containing novolac resins by chemically modifying a commercial novolac resin with bis(benzo-1,3,2-dioxaborolanyl)oxide (a) and bis(4,4,5,5tetramethyl-1,3,2-dioxaborolanyl)oxide (b) to obtain various boron-modified novolac resins. When the phenol novolac resin was modified with (a) and (b) at a molar ratio of 1:1 of the hydroxyl group to the boron atom, the TGA results of the modified system had a char yield of 44.0% at 800 C. Compared with the unmodified resin, the initial degradation temperature and char yield of the modified resin decreased 84 C and increased 4.0% respectively.…”

Section: Introductionmentioning

confidence: 99%

“…[24,25] Therefore, POSS is a kind of nanomaterial with easy interface modification, good heat resistance, excellent thermal oxidation stability as well as mechanical properties, which make it can be wide applied in aerospace and many high-tech fields. [18,26,27] One of the most attractive applications of POSS is to improvement the heat resistance of polymers since their inorganic Si─O─Si core. [24,28,29] At present, the research on the modification of PF resin with POSS is relatively rare, because the PF resin itself is a kind of resin with good temperature resistance, and it is difficult to improve its heat resistance.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of3,13‐diglycidyloxypropyloctaphenyldouble‐decker polyhedral oligomeric silsesquioxane and the thermal reaction properties with thermosetting phenol‐formaldehyde resin

Niu

Tian

Yan

et al. 2020

Self Cite

3,13‐Diglycidyloxypropyloctaphenyl double‐decker silsesquioxane (EP‐DDSQ) was synthesized by process of alkaline hydrolysis condensation of phenyltrimethoxysilane and corner capping reaction of methyldichlorosilane, followed by hydrosilylation with allyl glycidyl ether, and the resultant structure was confirmed by fourier transform infrared spectrometer (FTIR) and nuclear magnetic resonance (NMR), respectively. The thermosetting phenol‐formaldehyde (PF) resin was then modified by EP‐DDSQ, and the reactivity of PF resin with EP‐DDSQ and thermal pyrolysis of modified cured resin were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The surface morphologies of modified resins at high temperature were characterized with field emission scanning electron microscope (FESEM), and chemical structure of modified resins was analyzed through X‐ray photoelectron spectrometer (XPS). The results showed that the appropriate addition of EP‐DDSQ did not affect the curing temperature of the PF resin itself, but could improve the heat resistance of the system. When the amount of EP‐DDSQ added was 10%, the initial degradation temperature of PF resin was increased by 49.31°C, and when the amount of EP‐DDSQ added was 16%, the char yield of which was reached up to 61.39%, compared with that of pure PF resin (TGA1,000°C of 57.62%) at Ar atmosphere. More importantly, the modified resin formed a regular and dense layer of SiC and SiOx ceramic on the surface after ablation in the muffle furnace at 800°C air atmosphere, which is very important for ablative resistant materials.