Further improvement of flame retardancy of polyaniline-deposited paper composite through using phytic acid as dopant or co-dopant

Joint Exfoliation of MXene by Dimensional Mismatched SiC/ZIF-67 Toward Multifunctional Flame Retardant Thermoplastic Polyurethane

The single-layer MXene fully demonstrates the advantages of 2D materials, especially catalytic, conductive, and mechanical properties. However, the high energy consumption and low efficiency faced by MXene in the divestiture process are still challenges that need to be solved urgently. In this article, dimension mismatch and collaborative stripping strategies are skillfully combined to easily realize the transformation from multi-layer MXene to single layer. In addition, the functionalized MXene@SiC@polyaniline (MXene@SiC@PANI) nano-hybrid materials are used as fillers to improve the thermal conductivity, flame retardant, and antibacterial properties of thermoplastic polyurethane (TPU). The surface temperature of TPU/MXene@SiC@PANI composites increased from 33.4 °C to 59.8 °C within 10 s. In addition, the antibacterial efficiency of TPU composites against Escherichia coli and Staphylococcus aureus is 69.6% and 88.9%, respectively. Compared with pure TPU, the peak heat release rate and total heat release are reduced by 71.4% and 34.6%, respectively. The flame-retardant mechanism of MXene hybrid materials is systematically discussed. It is worth noting that the introduction of PANI enhances the compatibility between the filler and the polymer, effectively maintaining the mechanical properties of the TPU itself. This work provides a convenient method for the multi-functional practical application of TPU.

Synergistic effect of phytic acid and eggshell bio-fillers on the dual-phase fire-retardancy of intumescent coatings applied on cellulosic substrates

Cellulosic substrates, including wood and thatch, have become icons for sustainable architecture and construction, however, they suffer from high flammability because of their inherent cellulosic composition. Current control measures for such hazards include applying intumescent fire-retardant (IFR) coatings that swell and form a char layer upon ignition, protecting the underlying substrate from burning. Typically, conventional IFR coatings are opaque and are made of halogenated compounds that release toxic fumes when ignited, compromising the roofing's aesthetic value and sustainability. In this work, phytic acid, a naturally occurring phosphorus source extracted from rice bran, was used to synthesize phytic acid-based fire-retardants (PFR) via esterification under reflux, along with powdered chicken eggshells (CES) as calcium carbonate (CaCO3) bio-filler. These components were incorporated into melamine formaldehyde resin to produce the transparent IFR coating. It was revealed that the developed IFR coatings achieved the highest fire protection rating based on UL94 flammability standards compared to the control. The coatings also yielded increased LOI values, indicative of self-extinguishing properties. A 17 °C elevation of the IFR coating's melting temperature and a significant ∼172% increase in enthalpy change from the control were observed, indicating enhanced fire-retardancy. The thermal stability of the coatings was improved, denoted by reduced mass losses, and increased residual masses after thermal degradation. As validated by microscopy and spectroscopy, the abundance of phosphorus and carbon groups in the coatings' condensed phase after combustion indicates enhanced char formation. In the gas phase, TG-FTIR showed the evolution of non-flammable CO2, and fire-retardant PO and P-O-C. Mechanical property testing confirmed no reduction in the adhesion strength of the IFR coating. With these results, the developed IFR coating exhibited enhanced fire-retardancy whilst remaining optically transparent, suggestive of a dual-phase IFR protective mechanism involving the release of gaseous combustion diluents and the formation of a thermally insulating char layer.

Preparation and properties of flame retardant and hydrophobic cotton fabrics based on poly-(dimethylsiloxane-co-diphenylsiloxane, dihydroxy terminated)/ammonia phytate

Applications for cotton fabrics with multifunctional qualities, such as flame retardancy, hydrophobicity, and anti-ultraviolet properties, are increasingly common and growing daily. The primary objective of this study is to investigate the preparation of flame retardant, hydrophobic, and ultraviolet (UV) protection cotton fabrics through the utilization of Poly-dimethylsiloxane-co-diphenylsiloxane, dihydroxy terminated (HTDMS) and ammonia phytate (AP). The flame retardancy, thermal stability, mechanical properties, anti-UV properties, air permeability and the hydrophobicity properties of coated cotton fabrics were evaluated. The results indicated that the HTDMS/AP coating was successfully deposited on the surface of cotton fabrics. The damaged length of Cotton/HTDMS/AP was 4.7 cm, and the limiting oxygen index reached 31.5 %. The thermogravimetric analysis revealed that the char residues in the high-temperature range were increased. Furthermore, cone calorimetry results indicated that after the HTDMS/AP coating, the peak heat release rate, total heat release, and total smoke production values decreased by 88.7 %, 51.2 %, and 98.4 %, respectively. Moreover, the deposition of HTDMS/AP provided cotton fabrics with hydrophobicity with a water contact angle of over 130°, while Cotton/HTDMS/AP maintained their air permeability, and enhanced the breaking force compared with those of Cotton/AP. Such desirable qualities make HTDMS/AP a meaningful coating for producing multifunctional cotton fabrics.

Hollow Superstructure In Situ Assembled by Single-Layer Janus Nanospheres toward Electromagnetic Shielding Flame-Retardant Polyurea Composites

A dodecahedral superstructure consisting of a single layer of Janus spheres containing ZIF-67 nanodots is prepared by in situ polymerization, with ZIF-67 and bio-based phytic acid (PA) as templates and dopants. It is used to improve the flame retardant, electromagnetic (EMI) shielding, and thermal conductivity properties of polyurea (PUA). By adding 5 wt% polyaniline@cobalt phytate-2.0 (PANI@Co-PA-2.0), the peak of heat release rate and the peak of smoke production rate are reduced by 54.9 and 59.9%, respectively. The peak of CO and CO2 production also decreased by 46.2 and 53.1%, respectively. A decrease in the absorption intensity of aliphatic and aromatic volatiles is also observed. The fire safety of PUA is greatly improved. In addition, PUA/PANI@Co-PA-2.0 exhibits an EMI shielding capability of 22.4 dB with the help of reduced graphene oxide, which confirms the possibility of PUA material application in the field of electromagnetic shielding. The 5 wt% filler increases the tensile strength of the PUA matrix to 6.3 MPa, and the composite material obtains good thermal conductivity. This work provides a viable method for the preparation of a flame-retardant, conductive, and electromagnetic refractory PUA substrate.

A novel green phosphorus-containing flame retardant finishing on polysaccharide-modified polyamide 66 fabric for improving hydrophilicity and durability

Rising concerns about the toxic effects and environmental issues associated with various fireproof treatments on textiles have led to a demand for "green" materials. Chitosan (CS) is an amino polysaccharide green, recyclable, and non-toxic highly biocompatible biopolymer that consists of multiple hydroxyl groups and has a wide range of applications, including as a flame retardant additive. In this study, an eco-friendly bio-based formaldehyde-free flame retardant containing a higher level of phosphorus and nitrogen in phytic acid ammonia (PAA) was synthesized to amplify the most plentiful green chitosan (CS)-modified polyamide 66 (PA66) fabric surface through a simple pad-dry-cure technique for the improvement of durable flame retardancy with hydrophilicity. The findings revealed that each UV-grafted CS fabric could entirely stop the melt-dripping tendency during the vertical burning (UL-94) test and reached a V-1 rating. Meanwhile, limiting oxygen index (LOI) testing showed a rapid increase from 18.5 % to 24 % for the PA66 control and the PAA-treated (i.e., PA66-g-5CS-PAA) fabric samples, respectively. Moreover, compared to the PA66 control sample, a dramatic decrease in the peak heat release rate (PHRR), fire growth rate (FGR), and total heat release (THR) by approximately over 52 %, 0.63 %, and 19.7 %, respectively, was observed for the PA66-g-5CS-PAA fabric sample. Additionally, this arrangement of PAA catalyzed the charring of grafted CS and acted as a condensed phase flame retardant, resulting in a significant improvement in char yield% in both air and N₂ atmospheres for the PA66-g-5CS-PAA fabric sample in TGA. In addition, only the lower grafting ratio of CS with PAA-treated fabric sample (i.e., PA66-g-2CS-PAA) could encourage it to gain its lowest water contact angle of 0⁰, as well as impersonating a positive effect in improving the flame retardant coating durability in washing and sustaining even after 10 home laundering cycles. This phenomenon suggests that an actual hydrophilic and durable flame retardant finishing procedure for polyamide 66 fabrics might be applied with the novel, plentiful, sustainable, and environmentally friendly bio-based green PAA ingredient.

Phytic Acid Doped Polyaniline as a Binding Coating Promoting Growth of Prussian Blue on Cotton Fibers for Adsorption of Copper Ions

In recent years, the elimination of heavy metals from wastewater has become an important topic due to rapid industrialization, and it is of considerable interest to develop renewable and degradable materials for this purpose. In this work, a novel Prussian blue/polyaniline@cotton fibers (PB/PANI@CFs) composite was fabricated by a two-step process. Phytic acid doped PANI as a binding coating greatly promoted both the growth of PB and the adsorption of Cu2+. The deposition ratio of PB was as high as 24.68%. Scanning electron microscopy (SEM) displayed that PB nanoparticles were grown more uniformly in the composite and formed a perfect nanocube structure compared with PB@CFs. The successful deposition of both PB and PANI on CFs was demonstrated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FITR), and X-ray photoelectron spectroscopy (XPS). The effect of adsorption time, adsorbent dose, initial pH value, and initial copper sulphate concentration on the adsorption of PB/PANI@CFs composite for Cu2+ was studied by static adsorption and was compared with those of PANI@CFs and PB@CFs. The results showed that the maximum removal efficiency of Cu2+ by PB/PANI@CFs can reach 93.4% within 5 h, and the maximum adsorption capacity of Cu2+ can reach 31.93 mg·g−1. The adsorption of Cu2+ on PB/PANI@CFs followed the pseudo-second order kinetic model and conformed to the Freundlich adsorption isothermal model. The PB-functionalized CFs provided new insights into the design of efficient and low-cost absorbents for heavy metal remediation. The proposed process solves two problems simultaneously, i.e., the utilization of environmentally friendly and biodegradable biomass resources and the adsorption of heavy metal ions, and is a good approach to achieve high-quality and sustainable development.

Flame Retardant Functionalization of Microcrystalline Cellulose by Phosphorylation Reaction with Phytic Acid

The functionalization of microcrystalline cellulose (MCC) is an important strategy for broadening its application fields. In the present work, MCC was functionalized by phosphorylation reaction with phytic acid (PA) for enhanced flame retardancy. The conditions of phosphorylation reaction including PA concentration, MCC/PA weight ratio and temperature were discussed, and the thermal degradation, heat release and char-forming properties of the resulting PA modified MCC were studied by thermogravimetric analysis and pyrolysis combustion flow calorimetry. The PA modified MCC, which was prepared at 90 °C, 50%PA and 1:3 weight ratio of MCC to PA, exhibited early thermal dehydration with rapid char formation as well as low heat release capability. This work suggests a novel strategy for the phosphorylation of cellulose using PA and reveals that the PA phosphorylated MCC can act as a promising flame retardant material.

Innovative Polyelectrolyte Treatment to Flame-Retard Wood

Fire protection has been a major challenge in wood construction for many years, mainly due to the high flame spread risk associated with wood flooring. Wood fire-retardancy is framed by two main axes: coating and bulk impregnation. There is a growing need for economically and environmentally friendly alternatives. The study of polyelectrolyte complexes (PECs) for wood substrates is in its infancy, but PECs’ versatility and eco-friendly character are already recognized for fabric fire-retardancy fabrics. In this study, a new approach to PEC characterization is proposed. First, PECs, which consist of polyethyleneimine and sodium phytate, were chemically and thermally characterized to select the most promising systems. Then, yellow birch (Betula alleghaniensis Britt.) was surface-impregnated under reduced pressure with the two PECs identified as the best options. Overall, wood fire-retardancy was improved with a low weight gain of 2 wt.% without increasing water uptake.

High mass loading polyaniline layer anchored cellulose fibers: Enhanced interface junction for high conductivity and flame retardancy

Novel cellulose fibers-based composite consisted of zirconium oxyhydroxide and phytic acid doped polyaniline was prepared via a two-step method of simple chemical precipitation and followed by in situ polymerization process. Cellulose fibers were firstly modified with zirconium oxyhydroxide to enhance the binding of phytic acid doped polyaniline to the surface. A compact coating of phytic doped polyaniline was developed on zirconium oxyhydroxide modified cellulose fibers through the chelating of zirconium ions to phytic acid. The resulting composite possessed a controllable mass loading of polyaniline, which could significantly improve the conductivity, flame retardancy and electrochemical stability. Therefore, the expected chelating between zirconium ions on cellulose fibers and phytic acid doped in polyaniline supported the excellent properties of the composite paper. Notably, the developed strategy is efficient, low-cost and environmental friendly, and the work opens up new doors to the development of other cellulose fibers-related interface enhancement applications.

In situ polymerization of polyaniline on cotton fabrics with phytic acid as a novel efficient dopant for flame retardancy and conductivity switching

A flame-retardant conductive cotton fabric switch was successfully prepared by the in situ polymerization of polyaniline doped with novel phytic acid (PA) by impregnation in an ice water bath for 24 h.

Mechanical and Fire Properties of Multicomponent Flame Retardant EPDM Rubbers Using Aluminum Trihydroxide, Ammonium Polyphosphate, and Polyaniline

In this study, multicomponent flame retardant systems, consisting of ammonium polyphosphate (APP), aluminum trihydroxide (ATH), and polyaniline (PANI), were used in ethylene propylene diene monomer (EPDM) rubber. The multicomponent system was designed to improve flame retardancy and the mechanical properties of the rubber compounds, while simultaneously reducing the amount of filler. PANI was applied at low loadings (7 phr) and combined with the phosphorous APP (21 phr) and the mineral flame retardant ATH (50 phr). A comprehensive study of six EPDM rubbers was carried out by systematically varying the fillers to explain the impact of multicomponent flame retardant systems on mechanical properties. The six EPDM materials were investigated via the UL 94, limiting oxygen index (LOI), FMVSS 302, glow wire tests, and the cone calorimeter, showing that multicomponent flame retardant systems led to improved fire performance. In cone calorimeter tests the EPDM/APP/ATH/PANI composite reduced the maximum average rate of heat emission (MARHE) to 142 kW·m-2, a value 50% lower than that for the unfilled EPDM rubber. Furthermore, the amount of phosphorus in the residues was quantified and the mode of action of the phosphorous flame retardant APP was explained. The data from the cone calorimeter were used to determine the protective layer effect of the multicomponent flame retardant systems in the EPDM compounds.

Construction of multifunctional boron nitride nanosheet towards reducing toxic volatiles (CO and HCN) generation and fire hazard of thermoplastic polyurethane

Considerable toxic volatiles (CO and HCN) generation and high fire hazard has definitely compromised the application of thermoplastic polyurethane (TPU). Here, a novel functionalization strategy for bulky h-BN is adopted to obtain the multifunctional CPBN, aiming at the flame retardancy reinforcement of TPU. The multifunctional CPBN is successfully prepared via the wrapping of phytic acid doped polypyrrole shell, following with the adsorption of copper ions. The obviously decreased peak heat release rate, peak smoke production rate and total smoke production values, obtained from cone test, confirms the reduced fire hazard of TPU composite with CPBN. The dramatic suppressions on CO and HCN releases can also be observed from TG-IR test. Tensile test demonstrates that adding CPBN favors the reinforcement in mechanical property of TPU. Thus, the concurrent improvements in flame retardancy and mechanical performance are achieved by incorporating CPBN. This work opens up new avenues for the functionalization of h-BN, and thus facilitates its promising applications in polymer-matrix composite.

A scalable ultrasonic-assisted and foaming combination method preparation polyvinyl alcohol/phytic acid polymer sponge with thermal stability and conductive capability

In this article, polyvinyl alcohol/phytic acid polymer (PVA/PA polymer) is synthesized from PVA and PA via the esterification reaction of PVA and PA in the case of acidity and ultrasound irradiation, and PVA/PA polymer sponge is prepared via foaming PVA/PA polymer in the presence of n-pentane and ammonium bicarbonate, and the structure of PVA/PA polymer and the structure, morphology and crystallinity of PVA/PA polymer sponge are characterized, and the thermal stability and surface resistivity of PVA/PA polymer sponge are investigated. Based on these, it has been attested that PVA/PA polymer synthesized under the acidity and ultrasound irradiation and PVA/PA polymer sponge are structured by the chain of PVA and the cricoid PA connected in the form of ether bonds and phosphonate bonds, and the thermal stability of PVA/PA polymer sponge attains 416.5 °C, and the surface resistivity of PVA/PA polymer sponge reaches 5.76 × 10⁴ ohms/sq.

Ultrasonic-assisted synthesis of polyvinyl alcohol/phytic acid polymer film and its thermal stability, mechanical properties and surface resistivity

In this paper, polyvinyl alcohol/phytic acid polymer (PVA/PA polymer) was synthesized through esterification reaction of PVA and PA in the case of acidity and ultrasound irradiation and characterized, and PVA/PA polymer film was prepared by PVA/PA polymer and characterized, and the influence of dosage of PA on the thermal stability, mechanical properties and surface resistivity of PVA/PA polymer film were researched, and the influence of sonication time on the mechanical properties of PVA/PA polymer film was investigated. Based on those, it was concluded that the hydroxyl group on the chain of PVA and the phosphonic group on PA were connected together in the form of phosphonate bond, and the hydroxyl group on the chain of PVA were connected together in the form of ether bond after the intermolecular dehydration; in the meantime, it was also confirmed that PVA/PA polymer film prepared from 1.20mL of PA not only had the high thermal stability and favorable ductility but also the low surface resistivity in comparison with PVA/PA polymer film with 0.00mL of PA, and the ductility of PVA/PA polymer film was very sensitive to the sonication time.

Adsorption and Flame Retardant Properties of Bio-Based Phytic Acid on Wool Fabric

Bio-based phytic acid (PA) as a nontoxic naturally occurring compound is a promising prospect for flame-retardant (FR) modifications to polymers. In this work, PA was applied to wool fabric using an exhaustion technique, and the adsorption and FR properties of PA on wool fabric were studied. The flame retardancy of the treated wool fabrics depended greatly on the adsorption quantity of PA, which was related to the pH of treatment solution, immersing temperature and initial PA concentration. The Langmuir adsorption of PA took place due to electrostatic interactions between PA and wool fiber. The limiting oxygen index, vertical burning and pyrolysis combustion flow calorimetry tests revealed that the treated wool fabrics exhibited good flame retardancy. The measurements of the phosphorus content of the burned fabric residues and thermogravimetric analyses suggested that a significant condensed-phase FR action was applicable to the PA treated fabrics. PA treatment was found to have little adverse effect on the whiteness and mechanical performance of wool. Additionally, the washing resistance of the FR fabrics should be further improved.

A Controlled Design of Aligned and Random Nanofibers for 3D Bi-functionalized Nerve Conduits Fabricated via a Novel Electrospinning Set-up

Scaffolds made of aligned nanofibers are favorable for nerve regeneration due to their superior nerve cell attachment and proliferation. However, it is challenging not only to produce a neat mat or a conduit form with aligned nanofibers but also to use these for surgical applications as a nerve guide conduit due to their insufficient mechanical strength. Furthermore, no studies have been reported on the fabrication of aligned nanofibers and randomly-oriented nanofibers on the same mat. In this study, we have successfully produced a mat with both aligned and randomly-oriented nanofibers by using a novel electrospinning set up. A new conduit with a highly-aligned electrospun mat is produced with this modified electrospinning method, and this proposed conduit with favorable features, such as selective permeability, hydrophilicity and nerve growth directional steering, were fabricated as nerve guide conduits (NGCs). The inner surface of the nerve conduit is covered with highly aligned electrospun nanofibers and is able to enhance the proliferation of neural cells. The central part of the tube is double-coated with randomly-oriented nanofibers over the aligned nanofibers, strengthening the weak mechanical strength of the aligned nanofibers.