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We reported the fabrication of an electrochemical sensor for uric acid (UA) monitoring using metal-free electrode based on heteroatoms (S, N, P, and O) doped carbon (HADC) nanoparticles, derived from polyphosphazene, synthesized via precipitation polymerization reaction between hexachlorocyclotriphosphazene (HCCP) and 1,4-dithiane-2,5-diol (DD) under sonication irradiations at 40 °C, following its modification with benzimidazolium-1-acetate ionic liquid (BIL). The developed HADC-BIL electrode showed a highly sensitive and selective response toward UA even in the presence of highly electroactive interferences such as ascorbic acid (AA), dopamine (DA), glucose (Glu), and hydrogen peroxide (H2O2). Our results demonstrated that the as-fabricated HADC-BIL electrode allows us to detect UA over a linear range of 2–1050 μM with a detection limit of 1.27 μM. Further, we were able to monitor the amount of UA level in the blood of a gout patient using the developed HADC-BIL electrode, which ensures the effectiveness of the developed sensor for the sensitive and selective detection of UA from real samples.

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Modification by intumescent flame retardants is an effective way to impart antiflame properties to fabric materials. Polyphosphazene elastomers contain all three elements required by intumescent flame retardants: an acid source, a gas source, and a carbon source, making them all-in-one integrated intumescent flame retardants. In this work, halogen-free poly­(dimethoxy)­phosphazene (PDMP) loaded with 29.0 wt % phosphorus and 13.1 wt % nitrogen is shown to be an ideal flame retardant for fabric materials. For the first time, transparent and elastic PDMP was applied as an intumescent flame retardant for cotton fabric. The PDMP-coated cotton shows remarkable high-efficiency flame-retardant properties: (1) a self-extinguishing property during the vertical flame test is obtained when the add-on level reaches 5.3 wt %, with a lower smoke release character; (2) the limiting oxygen index (LOI) values of coated cotton are improved with increasing add-on level, and the thickness of the coating is measured to be at the nanolevel, 2540 nm when 10.9 wt % PDMP is coated. The coated cotton shows enhanced carbonization ability at lower temperatures, which is the key to imparting flame-retardant properties to cotton, and the PDMP-coated cotton shows remarkably lower peak heat release rate and total heat release compared to the control cotton during combustion. The durability of modified cotton was tested after 50 laundering cycles, which showed that the coating maintains 80% of its initial mass, and the after-laundering sample preserves the characteristics of self-extinguishing and a high LOI. Thus, the PDMP nanocoating-modified flame-retardant cotton fabric is sufficiently durable for practical application.

The erosion resistances of ethylene propylene diene monomer (EPDM) insulations are often inadequate for advanced solid rocket motor (SRM) applications. EPDM modification by blending secondary matrixes is a feasible approach to improve the ablative properties of EPDM insulations. The addition of flexible inorganic hybrid rubbers as a secondary matrix, such as silicones and polyphosphazenes, may impart EPDM insulations with better ablative performance. The blends of EPDM/hybrid rubbers represent the state-of-the-art heat-shielding materials for SRM. In the present work, methyl-phenyl silicone/EPDM and poly(diaryloxyphosphazene)/EPDM insulation systems with various blending ratios of secondary matrixes have been prepared. The ablative properties of the insulations were examined by oxy-acetylene ablation tests, and the results showed that these properties could be enhanced accordingly by blending with hybrid rubbers under appropriate proportions. The unique charred layers resulting from the hybrid rubbers contributed to their excellent ablation properties. For example, the silicone/EPDM insulations exhibited a more significant improvement of ablation resistance properties. With a 1:1 blending ratio of silicone/EPDM, the linear ablation rate was 0.06 mm s−1 after 20 s of oxy-acetylene ablation. The enhancement in the ablative resistance was attributed to the charred layers with bunches of embedded compact microtubes with a length of 2–3 mm, which consisted of silicon carbide, silicon dioxide, and Si–O–C ceramics.

The ablative properties of elastomeric insulations are often inadequate for solid rocket motor (SRM) applications. These materials exhibit relatively high erosion rates during the operation of an SRM unless the charred insulation layers are reinforced with suitable fibre fillers. As alternatives to traditional synthetic rubber materials, flexible semi-inorganic rubbers such as polyphosphazene elastomers are now used as state-of-the-art heat-shielding materials. We have successfully managed to prepare a poly(diaryloxyphosphazene) elastomer (PDPP) as well as some insulation materials that are free of any fibrous fillers (with only the addition of inorganic oxides, such as fumed silica and zinc oxide). These polyphosphazene insulations exhibit excellent linear ablation rates (0.08 mm s−1 after a 20 s ablation test) as compared to synthetic organic rubbers. In addition, integrated and rigid charred layers without noticeable swells are formed on the surfaces of the matrices resulting in ‘coral fleece-like’ hollow microtubes, which show better ablative resistance performance than do traditional insulations. The pyrolysis products of PDPP have been characterized by pyrolysis gas chromatography mass spectrometry and the mechanism of its decomposition is also discussed.

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