Flame Retardant Polyacrylonitrile Research Articles

Flame retardant and mechanically enhanced polyacrylonitrile fibers prepared by amination and phosphorylation

To improve the flame retardancy of polyacrylonitrile (PAN) fibers, PAN fibers were firstly modified through amination with diethylenetriamine (DETA) to obtain ammoniated PAN fibers (A-PAN). Then, A-PAN underwent phosphorylation modification via phosphorus-containing flame retardant, i.e., tetrakis (hydroxymethyl) phosphonium sulfate (THPS) to fabricate flame retardant PAN fibers (THPS-A-PAN). XPS and FTIR confirmed the covalent bonding of DETA and THPS with PAN fibers. TGA showed improved thermal stability, particularly in increased char residue at high temperatures. The modified PAN fibers exhibited enhanced flame retardancy in vertical burning tests and MCC analysis, with LOI values increasing from 17% to 32.5% and maintaining at 26.5% after 30 laundering cycles (LCs). Fire safety parameters such as heat release capacity (HRC), total heat release (THR), and the fire growth index (FGI) decreased by 51.5%, 46.9%, and 41.9%, respectively. In addition, the tensile strength and elongation at break of THPS-A-PAN increased from 2.69 cN/dtex and 28.6% to 3.08 cN/dtex and 30.1% respectively, indicating enhanced mechanical properties. This work develops a feasible strategy to improve the flame retardancy of PAN fibers while endowing them with reinforced mechanical properties, which provides a possible research direction for the practical application of flame retardant PAN fibers.

A novel phosphorus/nitrogen-containing polyacrylonitrile fiber with excellent flame retardancy and mechanical properties

To improve the flame retardancy, smoke suppression and mechanical properties of polyacrylonitrile (PAN) fiber, it was first modified with diethylenetriamine to prepare the aminated PAN fiber (A-PAN). Second, diethyl phosphite (DEP) was grafted onto the A-PAN to fabricate flame retardant PAN fiber (DEP-A-PAN). XPS and FTIR analysis confirmed that phosphorus and nitrogen elements were covalently bonded to the surface of PAN fiber. TGA revealed that the incorporation of DEP promoted char formation of PAN matrix and suppressed the thermal degradation. DEP-A-PAN exhibited a significantly reduced peak heat release rate (pHRR) compared to the control sample. Moreover, the limiting oxygen index (LOI) of DEP-A-PAN was up to 34.3 %, and remained at 26.6 % even after 50 laundering cycles (LCs), demonstrating excellent durable flame retardancy. Interestingly, DEP-A-PAN exhibited improved tensile strength of 2.97 cN/dtex. This work developed a simple and feasible method for preparing mechanical-enhanced flame retardant and smoke suppressive PAN fiber, which could be large-scale preparation.

Biomass intumescent flame retardant polyacrylonitrile composite: flame retardancy, smoke suppression and recycling

A fully biomass intumescent flame retardant (IFR) system was fabricated by combining the reaction product ([email protected]) of phytic acid (PA) and hydrolyzed silk (HS) with potato starch (PS), which was then blended with polyacrylonitrile (PAN) to obtain flame retardant PAN (FR-PAN). The tensile strength and elongation at break for PAN-10%[email protected]/5%PS sample increased by 18.8% and 86.3%. The peak heat release rate (PHRR) and peak smoke production rate (PSPR) decreased by 54.8% and 79.3% respectively, exhibiting excellent flame retardant and smoke suppression performance. Furthermore, the PAN-10%[email protected]/5%PS sample was carbonized to prepare FR-PAN Char (FRPC), which was then used for cellulose and polyvinyl alcohol (PVA) modification. The maximum thermal decomposition rate and PHRR of modified cellulose and PVA were significantly reduced, showing the improved fire safety. This work not only prepared an eco-friendly fully biomass flame retardant PAN composite, but also realized the successful recycling of waste flame retardant PAN materials.

Synthesis and properties of difficult combustion material based on modified polyacrylonitrile

Abstract: Many ion exchange materials have been obtained on the basis of polyacrylonitrile (PAN) fiber. It is also known from the literature that PAN is also used in the creation of hard-to-burn materials. This is achieved by introducing functional active groups into PAN. Therefore, polyacrylonitrile was modified with triethanolamine (TEA) in order to synthesize an ion exchange material in this work. The reaction mechanism of the synthesized ion exchange substances, their structure, physico-chemical properties, stability in different environments and sorption properties were studied. A flame retardant material containing nitrogen and phosphorus was obtained by attaching phosphoric acid to the resulting ion exchange material. The resulting ion exchange PAN fabric was treated with phosphoric acid to produce flame retardant PAN fabrics (FR-PAN). The incorporation of triethanolamine and phosphorus into PAN fabric was investigated using Fourier transform infrared spectroscopy (FTIR). In order to evaluate the thermal stability and fire resistance of the obtained FR-PAN, limiting oxygen index (LOI) and thermo gravimetric analyzes (TGA) were performed.

Fabrication of durable flame retardant PAN fibers through bio-based ammonium phytate surface modification and highly efficient thermal oxidation

To address the flammable shortcoming of polyacrylonitrile (PAN) fibers, an ammonium phytate (AP) flame retardant was fabricated by using biomass phytic acid (PA) and urea as raw materials. PAN fibers were firstly treated with AP aqueous solution, which were then thermally oxidized to gain durable flame retardant PAN fibers (O-AP-PAN). The structure of fibers was characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The results indicated that AP promoted the formation of a thermally stable cyclic conjugated structure, and the P element was incorporated into the PAN fibers through covalent bond. The limiting oxygen index (LOI) value of O-AP-PAN fibers improved from 17.0% of PAN fibers to 36.6%. Even after 50 laundering cycles, the LOI value of O-AP-PAN maintained as high as 30.5%, indicating exceptional washing durability. Additionally, the total heat release and heat release capacity of O-AP-PAN were reduced by 46.8% and 52.7%, respectively. Besides, the mechanical strength of O-AP-PAN was well maintained without affecting practical use. In this work, a simple and feasible durable flame retardant strategy for PAN fibers was established, which was convenient for large-scale preparation of flame retardant PAN fibers.

Fabrication of halogen-free and phosphorus-free flame retardant and antistatic PAN fibers based on tea polyphenol phenolic resin chelated with iron (Ⅲ) ions

Polyacrylonitrile (PAN) fibers are one of the three major synthetic fibers in the world, but the drawbacks of flammable and static charge accumulation limit their application. To address the issue, tea polyphenol phenolic resin (TPPR) was firstly prepared from biomass tea polyphenol in this paper. Next, TPPR was blended with PAN spinning solution and wet-spun with Fe3+ solution as coagulation bath to construct phosphorus-free and halogen-free flame retardant PAN fibers (TPPR@Fe/PAN). The results indicated that the limiting oxygen index (LOI) value increased from (17.3 ± 0.51)% of PAN fibers to (31.6 ± 0.51)% of TPPR@Fe/PAN. Even after 30 laundering cycles (LCs), the LOI value of TPPR@Fe/PAN was still up to (27.7 ± 0.51)%, indicating good washing durability. Additionally, the heat release capacity (HRC) and total heat release (THR) of TPPR@Fe/PAN had 35.0% and 48.6% reduction, respectively. Furthermore, TPPR@Fe/PAN obtained excellent antistatic ability. Besides, the TG-IR results demonstrated that both the release of flammable and toxic gases were significantly suppressed. In the work, a simple and feasible flame retardant and antistatic strategy was established which was convenient for fabrication of functional PAN fibers on a large scale.

Construction of a fully bio-based intumescent flame retardant for improving the flame retardancy of polyacrylonitrile

Lignin (L), casein (C), and phytic acid (PA) were chosen to construct a fully bio-based intumescent flame retardant (IFR) for endowing polyacrylonitrile (PAN) with good flame retardancy. L/C/PAN was fabricated by solution blending of L and C with PAN, and the flame retardant PAN composite (FR-PAN) was prepared by the reaction of PA with L and C in L/C/PAN. FTIR and XPS confirmed the successful construction of fully bio-based IFR. FR-PAN achieved UL94 V-0 rating during a vertical burning test. Moreover, the char residue of FR-PAN at 800 °C in N2 and air reached 59 and 8 wt%, respectively, showing good char-forming ability. Furthermore, SEM-EDS revealed that phosphorus-rich and intumescent char residues were formed after the combustion of FR-PAN. The peak of heat release rate (PHRR) and smoke production rate (PSPR) of FR-PAN were reduced by 71.4% and 64.8%, respectively, and the pyrolysis products of FR-PAN were significantly reduced. Besides, the flame-retardant mechanism of the fully bio-based IFR on FR-PAN was proposed.

Polyacrylonitrile-based ion-exchange material synthesis and combustion properties investigation

Many ion exchange materials have been obtained on the basis of polyacrylonitrile (PAN) fiber. It is also known from the literature that PAN is also used in the creation of hard-to-burn materials. This is achieved by introducing functional active groups into PAN. Therefore, polyacrylonitrile was modified with triethanolamine (TEA) in order to synthesize an ion exchange material in this work. The reaction mechanism of the synthesized ion exchange substances, their structure, physicochemical properties, stability in different environments and sorption properties were studied. A flame retardant material containing nitrogen and phosphorus was obtained by attaching phosphoric acid to the resulting ion exchange material. The resulting ion exchange PAN fabric was treated with phosphoric acid to produce flame retardant PAN fabrics (FR-PAN). The incorporation of triethanolamine and phosphorus into PAN fabric was investigated using Fourier transform infrared spectroscopy (FTIR). In order to evaluate the thermal stability and fire resistance of the obtained FR-PAN, limiting oxygen index (LOI) and thermo gravimetric analyzes (TGA) were performed. Thermal analysis showed that the newly obtained FR-PAN had higher thermal stability than the original PAN fabric, produced 21 wt.% more char, and increased the limited oxygen index from 18% to 31.5%.

Surface properties and flame retardancy of polyacrylonitrile fabric modified with nitrilase and vinyl phosphate

Flame-retardant finishing is essential for polyacrylonitrile fabric because of the restriction in application caused by poor flammability. Flame-retardant polyacrylonitrile fabric treated with nitrilase and vinyl phosphate was successfully prepared in this study. X-ray photoelectron spectroscopy, thermogravimetric analysis, limiting oxygen index, KES fabric style instrument, air permeability, moisture permeability, thermal resistance, and moisture resistance tests were conducted to characterize the treated polyacrylonitrile fabrics. The results showed that carboxyl groups were introduced after nitrilase treatment, which efficiently improved the adsorption and combination of vinyl phosphate on polyacrylonitrile fibers. The sample prepared with nitrilase/vinyl phosphate treatment exhibited a high limiting oxygen index value of 27.5%. The air permeability and moisture permeability of the treated fabric decreased while moisture resistance increased.

A facile strategy to fabricate phosphorus-free and halogen-free flame retardant polyacrylonitrile fiber based on amidoximation and Fe (III) ion chelation

In this work, we proposed a novel phosphorus-free and halogen-free strategy to prepare flame retardant polyacrylonitrile fibers (FR-PAN). First, PAN fibers were modified with hydroxylamine hydrochloride (HA) to introduce amidoxime groups in PAN fibers (A-PAN), then the A-PAN samples were immersed in ferric chloride solution to chelate Fe3+ to obtain FR-PAN. The micro calorimeter (MCC) test showed that the peak heat release rate (PHRR) and total heat release (THR) of FR-PAN were reduced by 72.9%, and 86.9% respectively. Meanwhile, the limiting oxygen index (LOI) value of FR-PAN increased from 17.0% to 36.7%. TG results demonstrated that amidoxime groups promoted the cyclization and dehydrogenation of PAN in advance. Meanwhile, the released nonflammable NH3 effectively diluted the emission of combustible gases, which acted as a flame retardant role in gas-phase. Fe3+ had synergistic catalytic char formation effect, resulting in a highly dense char layer containing Fe2O3, which isolated oxygen, significantly reduced the emission of toxic gases. This work endowed PAN fibers with good flame retardancy and great potential application in the field of functional fibers.

Flame retardant polyacrylonitrile fiber modified with hydrazine hydrate and copper ions

The limiting oxygen index (LOI) of polyacrylonitrile (PAN) fiber is only around 18%, making it urgently needed to enhance flame retardancy. Treatment with hydrazine hydrate as cross-linking agents followed by adsorption of metal ions endows PAN fibers with excellent flame retardancy. The Fourier-transform infrared spectroscopy (FT-IR) was employed to investigate the evolution of the chemical structure of the fibers. The atomic adsorption spectrometer (AAS) was carried out to study the adsorption capacity for copper ions. The wide-angle X-ray diffraction (WAXD) and scanning electron microscope (SEM) were used to study the aggregate structure and morphology of the fibers. In addition, LOI, thermogravimetric analysis/infrared spectrometry (TG-FTIR), and thermogravimetric analysis (TGA) were employed to clarify the flame-retardancy and the mechanisms. The mechanical property was studied via a single fiber tensile tester. The results showed that more chelating groups arose in macromolecular chains of PAN fibers after the reaction with hydrazine hydrate, with increased adsorption capacity for Cu2+. The LOI reached 24.0% after the treatment of hydrazine hydrate and the fiber was still flammable in the air. After the treatment with metal ions, the LOI of the fibers dramatically rose to 45.2%. The thermal decomposition process differed after the treatment of hydrazine hydrate, resulting in a more violent release of ammonia and a sharp reduction of flammable gases. The introduction of copper ions made fibers form dense carbon residue during thermal decomposition, which was beneficial for the improvement of flame retardancy.

Biomaterial arginine encountering with UV grafting technology to prepare flame retardant coating for polyacrylonitrile fabric

In order to endow polyacrylonitrile (PAN) fabric with excellent thermal and flame retardant properties, glycidyl methacrylate (GMA) was grafted on the surface of PAN fabric by UV-induced grafting technology to obtain GMA grafted PAN fabric (PAN-g-GMA). Next, L-Arginine was introduced to PAN-g-GMA (PAN-g-GMA/Arg) through the reaction of the amino groups in L-Arginine and the epoxy groups in GMA units. Then the flame retardant PAN fabric (FR-PAN) was prepared via the phosphorylation of PAN-g-GMA/Arg. When the grafting percentage was up to 13.5 wt%, the residual char of FR-PAN at 800 °C reached 51.6 wt%, indicating improved thermal stability. In addition, compared to PAN sample, the peak of heat release rate (PHHR) and total heat release (THR) of FR-PAN were remarkably decreased by 36.3% and 8.1% respectively, demonstrating excellent flame retardancy. Moreover, the elongation at break of FR-PAN fabric was increased by 53.6%. The cyclization of PAN induced by phosphoric acid reduced the chain breakage and inhibited the degradation of PAN. Moreover, the introduced amino acids delayed the release of HCN and other pyrolysis volatiles, meanwhile, the released NO and other non-combustible gases prevented oxygen from entering the combustion zone. This work presents a facile strategy for the application of amino acid materials in flame retardant PAN materials.

Highly effective flame retardant lignin/polyacrylonitrile composite prepared via solution blending and phosphorylation

Aiming at improving the thermal stability and flame retardancy of polyacrylonitrile (PAN), a novel flame retardant PAN composite was prepared via a facile approach. First, lignin (LIG) and PAN were dissolved in dimethyl sulfoxide (DMSO) to form a uniform blend solution of LIG and PAN, then the solution was poured into the mould to scrape the LIG/PAN composite film. Subsequently, the flame retardant LIG/PAN composite (FR-LIG/PAN) was fabricated via phosphorylation. The structure of pure PAN, LIG, LIG/PAN and FR-LIG/PAN composite was characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The thermal and combustion properties of the samples were evaluated by using thermogravimetric analysis (TGA) and cone calorimeter test (CCT). In addition, the cross section and char residue of FR-LIG/PAN composite after combustion were observed by scanning electron microscopy (SEM). Furthermore, the elemental compositions and contents of the cross section and char residue of FR-LIG/PAN composite after combustion were tested by energy-dispersive X-ray spectroscopy (EDS). The results indicated that hydroxyl group and benzene skeleton were present in LIG/PAN and the phosphorus element was successfully introduced into FR-LIG/PAN composite via phosphorylation. The amount of char residue for FR-LIG/PAN at 800 °C is more than those of pure PAN and LIG/PAN. SEM photos indicate the expansion characteristics of the char residue, and EDS results prove that the uniform distribution of elements in the cross-section of FR-LIG/PAN composite. Moreover, FR-LIG/PAN exhibits the lowest peak heat release rate (pHRR) and smoke production rate (SPR). These results demonstrated that FR-LIG/PAN had excellent flame retardancy and char forming ability. In addition, the composition of the gases evolved from pyrolysis process of FR-LIG/PAN was analyzed by thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR). The main pyrolysis products in gas phase are H2O, CO2 and PO•. This work proposes one facile method for preparation of practical flame retardant PAN composite.

Highly efficient thermal oxidation and cross-linking reaction of catechol functionalized polyacrylonitrile copolymer composites for halogen-free flame retardant

There have been major efforts to make polyacrylonitrile (PAN) flame retardant using halogens, heavy metals, transition metals, and phosphorus-organic compounds. These retardants may reduce the risk of fire, but they also involve high cost, toxicity, and related ecological issues. In an effort to mitigate some of these negative factors, we herein report the development of a green flame-retardant PAN based on bio-inspired dopamine methacrylamide (DMA) co-monomer. This polymer was synthesized through free radical polymerization of AN and acetonide-protected dopamine methacrylamide (ADMA), followed by deprotection of ADMA. Systematic investigation of the structural evolution of P(AN-co-DMA) confirmed that DMA provides a kinetic advantage for initiating the cyclization of PAN at significantly lower temperatures (209 °C) as well as for controlling effectively the amount of heat generated. Moreover, the effective radical scavenging capability of DMA, and the formation of a carbonaceous layer on the polymer surface, greatly improved the flame-retardant performance of PAN, without the use of conventional additives. This resulted in low heat-release capacity (HRC) and high limiting oxygen index (LOI) values of 58 Jg–1 K−1 and 37% (superior to those values of Nomex®), respectively. The thermal oxidative stabilization (TOS) process and flame retarding properties of PAN/GO composites were further investigated. TOS process and flame retarding mechanism were found to be influenced by ionic interaction and hydrogen bonding between polymer and nanomaterial. This work opens up a facile and sustainable methodology for the design of environmentally friendly and high-performance flame retardants and composites.

Fabrication of Chitosan-Based Intumescent Flame Retardant Coating for Improving Flame Retardancy of Polyacrylonitrile Fabric.

In order to improve the flame retardancy of polyacrylonitrile (PAN) fabrics, glycidyl methacrylate (GMA) was first grafted onto the surface of PAN fabric (PAN-g-GMA) by means of UV-induced photo grafting polymerization process. Then, PAN-g-GMA was chemically grafted with chitosan to obtain a bigrafted PAN fabric (PAN-g-GMA-g-CS). Finally, the flame-retardant PAN fabric (FR-PAN) was prepared by phosphorylation. The structure and elemental analysis of the samples were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The thermal degradation properties and combustion characteristics of the fabrics were accessed by thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and cone calorimeter (CC). The results show that the onset thermal decomposition temperature of FR-PAN fabric is lower than that of the control sample due to the degradation of the grafting groups. The combustion test indicates that the FR-PAN fabric has an excellent flame-retardant property and the combustion rate is significantly reduced. In addition, the char residue of the burned FR-PAN fabric is over 97%, indicating excellent char-forming ability.

Preparation of halogen-free flame retardant polyacrylonitrile via hydrolyzing and grafting with diphenylphosphinyl chloride

Halogen-free flame retardant polyacrylonitrile (PAN) was prepared via hydrolyzing the nitrile groups of PAN using aqueous sodium carbonate solution/hydrogen peroxide followed by grafting with diphenylphosphinyl chloride. The structure of original PAN, hydrolyzed PAN (HPAN), and flame retardant PAN (FR-PAN) samples were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and 1H NMR spectroscopy. The thermal properties of the materials were assessed using thermogravimetric analysis. The FTIR spectroscopy indicates that a carbonyl group is present in hydrolyzed HPAN and some characteristic PAN absorption peaks decreased slightly upon hydrolysis. The XPS results show that FR-PAN contained phosphorus, indicating that diphenylphosphinyl chloride has been grafted onto HPAN, which is in accordance with the phenomenon of the self-extinguishing phenomena of FR-PAN during burning experiments. The TG curves indicate the presence of a char residue for FR-PAN of 45% at 800 °C, a higher char residue than that of original PAN (39%). Therefore, FR-PAN displays better thermal stability and char forming capability than does the untreated polymer.

Polyvinyl Alcohol Reinforced Flame-Retardant Polyacrylonitrile Composite Fiber Prepared by Boric Acid Cross-Linking and Phosphorylation.

To improve the strength and maintain the inherent properties of flame-retardant polyacrylonitrile (FR-PAN) fiber, a commercialized hydrocarbon polymer, i.e., poly (vinyl alcohol) (PVA), used as an enhancement component, was blended with polyacrylonitrile (PAN) spinning dope to fabricate a PVA/PAN composite fiber through wet-spun technology. Then, cross-linked PVA/PAN composite fiber (C-PVA/PAN) was acquired via boric acid cross-linking. Finally, flame-retardant C-PVA/PAN fiber (FR-PVA/PAN) was prepared by phosphorylation. The structures of the samples were characterized by Fourier transform infrared analysis (FTIR) and X-ray photoelectron spectroscopy (XPS). The thermogravimetric analysis (TGA) results reveal that the thermal stability of the composite fiber is lower than that of the pristine PAN fiber. However, the char residue of the composite fiber is higher than that of the control sample, wherein, FR-PVA/PAN has the highest char residue of 62.5 wt% at 800 °C. The results regarding the combustion properties of FR-PVA/PAN show that the fire hazard of FR-PVA/PAN is restrained greatly, indicating excellent flame-retardant performance. The corresponding flame-retardant mechanism of FR-PAV/PAN is investigated by Pyrolysis gas chromatography and mass spectrometry (Py-GC/MS) and thermogravimetric analysis coupled with Fourier transform infrared analysis (TG-FTIR). The results indicate the gas-phase and condensed-phase flame-retardant mechanisms.

Preparation of phosphorus‐containing and nitrogen‐containing durable flame retardant polyacrylonitrile fabric via surface chemical modification

SummaryUltraviolet‐induced photografting polymerization combined with surface modification was developed to prepare durable flame retardant polyacrylonitrile (PAN) fabric. First, acrylic acid (AA) was grafted onto PAN fabric (PAN‐g‐PAA) through ultraviolet‐induced photograft polymerization. Then, PAN‐g‐PAA was modified sequentially by acylation, ammonization, and phosphorylation to obtain acylated PAN‐g‐PAA, ammoniated Cl‐PAN‐g‐PAA, and fire retardant PAN fabric, respectively. The influence of grafting time, concentration of acrylic acid, and initiator on the grafting percentage was studied in detail. Fourier transform infrared spectrometer, X‐ray diffraction, and scanning electron microscopy confirm the successful grafting of AA. The thermal properties of the fabrics were investigated by thermogravimetric analysis and differential scanning calorimetry. Thermal analysis indicates that FR‐PAN has good thermal stability at higher temperature and the char residue is about 41 wt% at 800°C. The limiting oxygen index value of the fire retardant fabrics can achieve 28.1 vol% and is still 27.3 vol% after 20 cycles washing, showing good durability.

Preparation of Flame Retardant Polyacrylonitrile Fabric Based on Sol-Gel and Layer-by-Layer Assembly.

This paper aims to develop a novel method, i.e., sol-gel combined with layer-by-layer assembly technology, to impart flame retardancy on polyacrylonitrile (PAN) fabrics. Silica-sol was synthesized via the sol-gel process and acted as cationic solution, and phytic acid (PA) was used as the anionic medium. Flame-retardant-treated PAN fabric (FR-PAN) could achieve excellent flame retardancy with 10 bilayer (10BL) coating through layer-by-layer assembly. The structure of the fabrics was characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The thermal stability and flame retardancy were evaluated by thermogravimetric (TG) analysis, cone calorimetry (CC) and limiting oxygen index (LOI). The LOI value of the coated fabric was up to 33.2 vol % and the char residue at 800 °C also increased to 57 wt %. Cone calorimetry tests revealed that, compared to the control fabric, the peak of heat release rate (PHRR) and total heat release (THR) of FR-PAN decreased by 66% and 73%, respectively. These results indicated that sol-gel combined with layer-by-layer assembly technique could impart PAN fabric with satisfactory flame-retardant properties, showing an efficient flame retardant strategy for PAN fabric.

Durable flame retardant polyacrylonitrile fabric via UV-induced grafting polymerization and surface chemical modification.

To improve the flame retardancy of polyacrylonitrile (PAN) fabric, glycidyl methacrylate (GMA) was firstly grafted onto the surface of PAN fabric. Then, the GMA grafted PAN fabric (PAN-g-GMA) was chemically modified with hydrazine hydrate and phosphorus acid in sequence to obtain ammoniated PAN-g-GMA fabric (Am-PAN-g-GMA) and flame retardant PAN fabric (FR-PAN), respectively. The structures, thermal properties and combustion characteristics of the samples were researched in detail. The results indicate that the fire retardant PAN fabric has good char-forming ability. Cone calorimeter tests show that the total heat release (THR) of FR-PAN declines by 38.4%, while the peak heat release rate (PHRR) of FR-PAN decreases by 60.2%. Moreover, the total smoke production (TSP) and the peak smoke production rate (PSPR) of FR-PAN dropped from 1.5 m2 and 0.06 m2 s−1 for the control sample to 0.4 m2 and 0.01 m2 s−1, respectively, indicating excellent smoke repression performance. The LOI value of FR-PAN fabric was 29.3% after 30 washing cycles showing good washing resistance and excellent flame retardant durability.