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.
Although high-performance graphene-based micro/ nano flexible electronic devices have shown promising applications in numerous fields, there are still many problems in converting graphene into practical applications. Heteroatom-doped graphene materials are of huge importance because heteroatom doping can significantly change the electronic structure and introduce the active site, which benefits the integration with a promising substrate and achieves nondestructive transfer of carbon materials. Herein, we analyze in detail the pyrolysis gas composition of heteroatomenriched phosphazenes with different structures and prepare a series of high-quality in situ N, P-codoped carbon-based films from phosphazene solid sources on a low-cost glass substrate by a convenient one-step method. The N, P-codoped carbon film shows reflectivity, good conductivity, and transparency. In addition, with the help of in situ "molecular welding", we achieve nondestructive transfer of a conductive carbon-based film from a glass substrate to promising layer-polyimide (PI) and prepare a flexible freestanding carbon/PI hybrid film with an excellent binding interface. The flexible conductive hybrid film shows excellent durability under an extremely low temperature environment and superior bending stability after 800 bending cycles. The results suggest that a phosphazene precursor is an amazing choice for constructing high-quality heteroatom-doped conductive carbon films. Besides, this work provides a promising way for nondestructive transfer of the conductive carbon-based films and large-scale preparation of largearea patterned conductive thin films.
Applying multi-heteroatoms doping strategy to prepare porous carbon materials with high surface area has been demonstrated to be effective for enhancing electrochemical performance of supercapacitors. In this study, N, P, O, and Si tetra-atoms-doped hierarchically micro-/mesoporous carbon with ultrahigh surface area is fabricated from crosslinked-linear poly (diaryloxyphosphazene) precursor by using silica which serves as both template and dopant. The surface area and heteroatoms doping content of the synthesized carbons are tailored by tuning silica dosage and carbonization temperature. The tetra-atoms-doped mesoporous carbon exhibits an ultrahigh surface area of 3,132 m 2 /g with enriched heteroatoms content (22 at%), which contribute to the capacitive performance. The as-fabricated tetra-atoms-doped carbon symmetric cell displays outstanding specific capacitance of 288.8 F/g (0.5 A/g) (539.8 F/ g in three-electrode system) with high remaining capacitance of 226.1 F/g at 10 A/g and excellent cycling stability (97.7 % capacity retention after 5,000 cycles at 10 A/g). This study suggests an effective multi-heteroatoms-doping approach to synthesize mesoporous carbon materials for high performance electrochemical conversion and storage devices.
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