A novel bio-based flame retardant for polypropylene from phytic acid

Bio-based P-N flame retardant with ZIF-67 in-situ growth on flexible polyurethane foam with excellent fire safety performance

The wide application of flexible polyurethane foam (FPUF) poses a giant challenge to human society in terms of fire prevention and environmental pollution. To solve this problem, the lignocellulose-based P-N flame retardant (LFPN) has been developed using mechanochemical methods. It was found that FPUF treated using LFPN exhibited good flame retardancy, but suffered from high smoke generation and toxicity. The hollow dodecahedral ZIF-67 has been used for smoke suppression catalysis, but the agglomeration phenomenon makes it inefficient. Hence, in this study, the adhesive properties of polydopamine (PDA) were utilized to assist the in-situ growth of ZIF-67. The results showed that the total smoke release rate of the treated FPUF was reduced by 40.5%. The toxic gases, such as carbon monoxide (CO), hydrogen cyanide, etc., also showed the same decreasing trend. What's more, the catalytic effect of ZIF-67 itself and the synergistic effect with LFPN gave FPUF great flame retardant and smoke inhibition properties. This novel FPUF provides a new reference for achieving smoke suppression and toxicity reduction.

Multi-functionalization of cotton fabrics with excellent flame retardant, antibacterial and superhydrophobic properties

Cotton fabric is widely used in many fields for its excellent comfortability, breathability and hygroscopicity. However, the development of multifunctional cotton fabrics to meet the requirements of different scenarios is a top priority. In this study, multifunctional coating was constructed through facile layer-by-layer assembly phytic acid and chitosan, and spraying divalent copper ion and polydimethylsiloxane (PDMS) on cotton fabrics, anticipating to endow them with flame retardancy, antibacterial and superhydrophobic properties simultaneously. The treated cotton fabric achieved a limiting oxygen index (LOI) value of 32 %, with the char length reducing to 10.7 cm revealing excellent flame retardancy. The water contact angle of multifunctional treated cotton fabric was above 150°, demonstrating it had superhydrophobicity. The antibacterial rates of multifunctional cotton fabrics against E. coli and S. aureus reached to higher than 99 %, indicating that the excellent antibacterial properties. Combined with the thermal stability of cotton fabrics and their char residues analysis, these results demonstrated that the multifunctional coating could act through intumescent flame retardant mechanism to flame retardant cotton fabrics. This research provides a facile way to prepare multifunctional cotton fabrics to broaden the application prospect.

Study on the Flame Retardancy of Rigid Polyurethane Foam with Phytic Acid-Functionalized Graphene Oxide

A rigid polyurethane foam (RPUF) composite was prepared by compounding phytic acid (PA)-functionalized Graphite oxide (PA-GO) with flame-retardant poly (Ammonium phosphate) (APP) and expandable graphite (EG). The effects of PA-GO on the thermal, flame-retardant, and mechanical properties of RPUF were studied using a thermogravimetric analyzer, a limiting oxygen index (LOI) tester, a UL-94 vertical combustion tester, a cone calorimeter, scanning electron microscopy, and a universal tensile testing machine. The results indicated that there was a significant synergistic flame-retardant effect between PA-GO and the intumescent flame retardants (IFR) in the RPUF matrix. Compared with RPUF-1, the addition of 0.3 wt% PA-GO could increase LOI from 25.7% to 26.5%, increase UL-94 rating from V-2 to V-0, and reduce the peak heat release rate (PHRR) and total heat release rate (THR) by 28.5% and 22.2%, respectively. Moreover, the amount of residual char increased from 22.2 wt% to 24.6 wt%, and the char layer was continuous and dense, with almost no holes. Meanwhile, the loss of mechanical properties was apparently lightened.

Rethinking the pathway to sustainable fire retardants

Flame retardants are currently used in a wide range of industry sectors for saving lives and property by mitigating fire hazards. The growing fire safety requirements for materials boost an escalating demand for consumption of fire retardants. This has significantly driven both the industry and scientific community to pursue sustainable fire retardants, but what makes a sustainable flame retardant? Here an overview of recent advances in sustainable flame retardants is offered, and their renewable raw materials, green synthesis and life cycle assessments are highlighted. A discussion on key challenges that hinder the innovation of fire retardants and design principles for creating truly sustainable yet cost-effective fire retardants are also presented. This short work is expected to help drive the development of sustainable, cost-effective fire retardants, and expedite the creation of a more sustainable and safer society.

Potential Use of Melamine Phytate as a Flame-Retardant Additive in Chicken Feather-Containing Thermoplastic Polyurethane Biocomposites

Using waste materials such as chicken feathers (CF) and biobased flame-retardant additives including melamine phytate (MPht) has become an effective approach for environmentally friendly and sustainable production in recent years. This study explores the flame retardant effectiveness of MPht in thermoplastic polyurethane (TPU)-based biocomposites containing CF. The characterizations of the composites are performed through thermal gravimetric analysis (TGA), limiting oxygen index (LOI), vertical UL-94 (UL-94 V), and mass loss calorimetry (MLC) tests. According to the test results, the highest UL-94 V rating of V0, a LOI value of 29.4%, and the lowest peak heat release rate (pHRR) (110 Kw/m²) and total heat evolved (THE) (39 MJ/m²) values are obtained with the use of 20 wt % MPht. It is demonstrated that MPht acts as an effective flame-retardant filler through the formation of intumescent char in the condensed phase and flame dilution in the gas phase.

Multi-functional bio-film based on sisal cellulose nanofibres and carboxymethyl chitosan with flame retardancy, water resistance, and self-cleaning for fire alarm sensors

Flexible and environmentally friendly bio-based films have attracted significant attention as next-generation fire-responsive sensors. However, the low structural stability, durability, and flame retardancy of pure bio-based films limit their application in outdoor and extreme environments. Here, we report the design of a sustainable bio-based composite film assembled from carboxymethyl-modified sisal fibre microcrystals (C-MSF), carboxymethyl chitosan (CMC), graphene nanosheets (GNs), phytic acid (PA), and trivalent iron ions (Fe³⁺). Cross-linking between Fe³⁺ and the C-MSF/CMC matrix and the formation of PA-Fe³⁺ complexes on the surface of the film imparted excellent mechanical properties, chemical stability, self-cleaning ability, and flame retardancy to the bio-film. Furthermore, the bio-film produced a reversible and sensitive response to temperature at 55.3-214.1 °C, and a fire alarm system made from the bio-film had a fire-response time of 4.6 s. In addition, the char layer of the bio-film retained a stable cyclic response to temperature, enabling it to serve as a fire resurgence sensor with a response time of 2.3 s and recovery time of 11.2 s. This work provides a simple pathway for the fabrication of self-cleaning, flame retardant, and water-resistant bio-films that can be assembled into fire alarm systems for the real-time monitoring of fire accidents and resurgence.

Flame-Retardant and Form-Stable Phase-Change Composites Based on Phytic Acid/ZnO-Decorated Surface-Carbonized Delignified Wood with Superior Solar-Thermal Conversion Efficiency and Improved Thermal Conductivity

In order to efficiently exploit solar-thermal energy, it is essential to develop form-stable phase-change material (PCM) composites simultaneously with superior solar-thermal storage efficiency, excellent flame retardancy, and improved thermal conductivity. Herein, phytic acid (PA)-modified, zinc oxide-deposited, and surface-carbonized delignified woods (PZCDWs) were constructed by alkaline boiling, PA modification, ZnO deposition, and surface carbonization. Then, novel form-stable PCMs (PZPCMs) with superior solar-thermal storage efficiency, excellent flame retardancy, and improved thermal conductivity were fabricated by impregnating n-docosane into PZCDWs under vacuum. The PZCDW aerogels can well support the n-docosane and overcome liquid leakage owing to their superior surface tension and strong capillary force. Differential scanning calorimetry results showed that PZPCMs possessed superior n-docosane encapsulation yield and high phase-change enthalpy (185.2-213.1 J/g). Decorating delignified wood by surface carbonization and ZnO deposition significantly improved the solar-thermal conversion efficiency (up to 86.2%) and thermal conductivity (193.3% increased) of PCM composites. Furthermore, with the introduction of PA into PZPCMs, the peak heat release rate and total heat release of the PCM composites decreased considerably, indicating the enhanced flame retardancy of PZPCMs. In conclusion, the novel renewable wood-based PCM composites demonstrate promising potential in solar energy harnessing and thermal modulation technologies.

Research and Application of Biomass-Based Wood Flame Retardants: A Review

Wood is widely used as a construction material due to its many advantages, such as good mechanical properties, low production costs, and renewability. However, its flammability limits its use in construction. To solve the problem of wood flammability, the most common method to improve the fire safety of wood is to modify the wood by deep impregnation or surface coating with flame retardants. Therefore, many researchers have found that environmentally friendly and low-cost biomass materials can be used as a source of green flame retardants. Two aspects of biomass-based intumescent flame retardants are summarized in this paper. On the one hand, biomass is used as one of the three sources or as a flame-retardant synergist in combination with other flame retardants, which are called composite biomass intumescent flame retardants. On the other hand, biomass is used alone as a feedstock to produce all-biomass intumescent flame retardants. In addition, the potential of biomass-based materials as an environmentally friendly and low-cost FR source to produce high-performance biomass-based flame retardants with improved technology was also discussed in detail. The development of biomass-based intumescent flame retardants represents a viable and promising approach for the efficient and environmentally friendly production of biomass-based flame retardants.

Preparation and Mechanism of Bio-Based Sodium Alginate Fibers with Flame Retardant and Antibacterial Properties

Flame retardant and antibacterial sodium alginate (SA) fiber were fabricated using the bio-based flame retardant of phytic acid and DL-arginine successively, and then the morphological structures, combustion behavior, thermal stability, and mechanical as well as antibacterial properties of SA fiber were investigated carefully. It is found that when the additional amount of PADL (reaction products of phytic acid and DL-arginine) in SA composite fiber is 20 wt%, its limiting oxygen index (LOI) is 40.0 ± 0.3%, and UL-94 is V-0 grade. The combustion behavior of composite fiber shows that PADL can effectively reduce combustion heat and promote carbon formation. Its peak of HRR (pkHRR) is 5.9% of pure SA fiber, and the residual carbon increases from 23.0 ± 0.1% to 44.2 ± 0.2%. At the same time, the density of the residual carbon increases gradually. PADL can promote SA to form expanded carbon with increasing density, and isolate the heat and volatilization of combustible gases. The guanidine group of DL-arginine can interact with the cell membrane to kill bacteria, and the antibacterial property of SA composite fiber is increased by 30%. This study provides a very ecological, safe, environmentally friendly and simple method to prepare flame retardant and antibacterial SA composite fiber with bio-based materials.

Pyrolysis of Precious Chinese Xuan Paper Containing Ammonium Phytate as a Flame Retardant

Xuan paper with outstanding cultural and artistic values is one of the most precious Chinese handmade papers and is widely used in traditional calligraphy and painting. However, the highly combustible cellulosic raw materials of Xuan paper present potential fire hazards. Ammonium phytate (AP) originating from biosourced phytic acid has been used for the flame-retardant treatment of Chinese Xuan paper by facile spray coating. The limiting oxygen index value of the treated Xuan paper increased to higher than 40%, demonstrating that the flammability of Xuan paper was greatly reduced by this treatment. The excellent flame retardancy afforded by this treatment was confirmed by cone calorimetry. TGA was used to demonstrate that the presence of AP changed the thermal decomposition process to promote char formation during the degradation of Xuan paper. The flame-retardant mode of action of phytate-coated Xuan paper was investigated using TG-FTIR, SEM, and XPS spectra. A P-N cooperative effect was proposed to account for both the condensed phase and gas-phase flame-retardant actions. The phosphorus component promotes char formation in the condensed phase, while the nitrogen component releases inert species to dilute the fuel load in the gas phase. The ink-wetting property of the coated Xuan paper was influenced negligibly by the coating process. The development of fire-resistant Xuan paper using ecofriendly flame retardants through simple and convenient spray coating has been demonstrated.

Low-dose exposure to PBDE disrupts genomic integrity and innate immunity in mammary tissue

The low-dose mixture hypothesis of carcinogenesis proposes that exposure to an environmental chemical that is not individually oncogenic may nonetheless be capable of enabling carcinogenesis when it acts in concert with other factors. A class of ubiquitous environmental chemicals that are hypothesized to potentially function in this low-dose capacity are synthesized polybrominated diphenyl ethers (PBDEs). PBDEs can affect correlates of carcinogenesis that include genomic instability and inflammation. However, the effect of low-dose PBDE exposure on such correlates in mammary tissue has not been examined. In the present study, low-dose long-term (16 weeks) administration of PBDE to mice modulated transcriptomic indicators of genomic integrity and innate immunity in normal mammary tissue. PBDE increased transcriptome signatures for the Nuclear Factor Erythroid 2 Like 2 (NFE2L2) response to oxidative stress and decreased signatures for non-homologous end joining DNA repair (NHEJ). PBDE also decreased transcriptome signatures for the cyclic GMP-AMP Synthase - Stimulator of Interferon Genes (cGAS-STING) response, decreased indication of Interferon Stimulated Gene Factor 3 (ISGF3) and Nuclear Factor Kappa B (NF-κB) transcription factor activity, and increased digital cytometry estimates of immature dendritic cells (DCs) in mammary tissue. Replication of the PBDE exposure protocol in mice susceptible to mammary carcinogenesis resulted in greater tumor development. The results support the notion that ongoing exposure to low levels of PBDE can disrupt facets of genomic integrity and innate immunity in mammary tissue. Such effects affirm that synthesized PBDEs are a class of environmental chemicals that reasonably fit the low-dose mixture hypothesis.

Improving the flame retardancy and accelerating the degradation of poly (lactic acid) in soil by introducing fully bio-based additives

In this study, a novel bio-based flame retardant LC-PA is prepared by the Mannich reaction between phytic acid (PA) and L-citrulline (LC). LC-PA is combined with tannic acid (TA) and introduced into PLA to improve fire performance and accelerate biodegradability. Compared with control PLA, the PLA composite containing 10% LC-PA/TA increases the LOI value to 26.9%, reaches a V-0 rating in the UL-94 test, and reduces the peak heat release rate and total heat release by 24.5% and 21.1%, respectively. More importantly, the introduction of LC-PA/TA accelerates the degradation rate of PLA in soil, which is of significance for biodegradable materials. The addition of LC-PA/TA can attract water and provide a suitable energy source for microbial proliferation, accelerating the hydrolysis and microbial degradation of PLA. This work provides a practical approach for high flame retardancy and rapid biodegradability in the soil to the bio-based polymer.

Eco-friendly flame retardant and dripping-resistant of polyester/cotton blend fabrics through layer-by-layer assembly fully bio-based chitosan/phytic acid coating

Polyester/cotton blend fabrics are widely used in clothing and household textiles which combine the comfort of cotton and excellent mechanical strength of polyester. However, their high flammability due to the special "wick effect" resulting from the different thermal decomposition process of cotton and polyester causes greatly potential fire hazards. In this study, fully bio-based intumescent flame retardant (IFR) coating of chitosan/phytic acid (CS/PA) was layer-by-layer (LBL) assembly constructed on polyester/cotton blend fabrics. The LOI value of polyester/cotton blend fabric which was LBL assembly coated by 20 bilayers CS/PA reached 29.2%. And the dripping of coated fabric was eliminated. The results of cone calorimetry test confirmed CS/PA coating greatly improved the flame retardancy of polyester/cotton blend fabrics. Thermogravimetric analysis (TGA) results showed CS/PA coating changed the thermal decomposition process to promote the char formation of polyester/cotton blend fabrics. CS/PA coating on fabric could form the IFR system which acts through both condensed phase action by the catalysis dehydration reaction to forming stable char and gas phase action by the blowing effect. This research provides a new strategy to eco-friendly flame retardant and dripping-resistant for polyester/cotton blend fabrics by bio-based IFR system through facile LBL assembly method.

Preferred zinc-modified melamine phytate for the flame retardant polylactide with limited smoke release

The higher flame retardancy and smoke suppression effects for PLA/MPAZn₂₀ were mainly ascribed to the condensed phase during combustion.

Highly efficient replacement of traditional intumescent flame retardants in polypropylene by manganese ions doped melamine phytate nanosheets

The intumescent flame retardant (IFR) with ammonium polyphosphate (APP) as the main component has many defects in practical applications, more than that, APP can be traced to non-renewable phosphate rock resources. For the foregoing reasons, the melamine phytate supramolecular nanosheet flame retardant incorporating manganese ion (PAMA-Mn) was successfully prepared with a facile and environmental friendly hydrothermal procedure based on renewable bio-based material phytic acid (PA). The flame retardant polypropylene composite (PPI) with 13.5 wt% APP and 4.5 wt% pentaerythritol (PER) failed to the UL-94 test, and its limiting oxygen index (LOI) value was only 26.5%. After 33 wt% of APP was replaced by PAMA-Mn, the PPMn33 incorporating only 18 wt% flame retardant additives passed the UL-94 V-0 rating, and its LOI value was increased to 31.9%. Compared with PP, pHRR and pSPR values of PPMn33 were reduced by 56% and 23%, respectively. The fire retardant mechanism of PPMn33 was thoroughly discussed via a variety of characterization methods. It was found that the peak of the Gram-Schmidt curve of PPMn33 was drastically reduced by 49% relative to that of PPI, indicating a remarkably decrease of combustible volatile products owing to the incorporation of PAMA-Mn, thereby rapidly reducing the fire hazard risk.

Synergistic lignin construction of a long-chain branched polypropylene and its properties

In light of current environmental pressures (referring to its destruction) and the consumption of petrochemical resources, the substitution of chemicals products with renewable natural substances has attracted extensive interest. In this paper, a synergistically constructed lignin polypropylene matrix composite with long-chain branched characteristics was prepared by a pre-irradiation and melt blending method. The effects of lignin on the crystallization, rheological behavior, foaming and aging properties of polypropylene were studied. Differential scanning calorimetry and polarized light microscopy results show that lignin undergoes heterophasic nucleation in a polypropylene matrix; rheological studies show that lignin promotes the formation of a heterogeneous polypropylene network, and thus polypropylene exhibits long-chain branching features; nucleation and a network structure endow the polypropylene-based composites with uniform cell size, thin cell walls, and a foaming ratio of 5–44 times; at the same time, a large number of hindered phenols in lignin can capture free radicals to improve the aging properties of the polypropylene. This research will help to convert industrial waste into functional composite materials.

Polypropylene with long chain branching behavior was constructed by lignin, which foaming property and polarity were improved.

Flame Retardant Polypropylenes: A Review

Polypropylene (PP) is a commodity plastic known for high rigidity and crystallinity, which is suitable for a wide range of applications. However, high flammability of PP has always been noticed by users as a constraint; therefore, a variety of additives has been examined to make PP flame-retardant. In this work, research papers on the flame retardancy of PP have been comprehensively reviewed, classified in terms of flame retardancy, and evaluated based on the universal dimensionless criterion of Flame Retardancy Index (FRI). The classification of additives of well-known families, i.e., phosphorus-based, nitrogen-based, mineral, carbon-based, bio-based, and hybrid flame retardants composed of two or more additives, was reflected in FRI mirror calculated from cone calorimetry data, whatever heat flux and sample thickness in a given series of samples. PP composites were categorized in terms of flame retardancy performance as Poor, Good, or Excellent cases. It also attempted to correlate other criteria like UL-94 and limiting oxygen index (LOI) with FRI values, giving a broad view of flame retardancy performance of PP composites. The collected data and the conclusions presented in this survey should help researchers working in the field to select the best additives among possibilities for making the PP sufficiently flame-retardant for advanced applications.

Biomolecules as Flame Retardant Additives for Polymers: A Review

Biological molecules can be obtained from natural sources or from commercial waste streams and can serve as effective feedstocks for a wide range of polymer products. From foams to epoxies and composites to bulk plastics, biomolecules show processability, thermal stability, and mechanical adaptations to fulfill current material requirements. This paper summarizes the known bio-sourced (or bio-derived), environmentally safe, thermo-oxidative, and flame retardant (BEST-FR) additives from animal tissues, plant fibers, food waste, and other natural resources. The flammability, flame retardance, and—where available—effects on polymer matrix’s mechanical properties of these materials will be presented. Their method of incorporation into the matrix, and the matrices for which the BEST-FR should be applicable will also be made known if reported. Lastly, a review on terminology and testing methodology is provided with comments on future developments in the field.

Novel sustainable biobased flame retardant from functionalized vegetable oil for enhanced flame retardancy of engineering plastic

The flame retardancy of an engineering plastic, poly(butylene terephthalate) (PBT), with a biobased flame retardant (FR) made from phosphorylated linseed oil (PLO) and phosphorylated downstream corn oil (PCO) was studied. Different phosphorus moieties were incorporated into the vegetable oil backbone through a ring-opening reaction. The chemical structure of the phosphorylated oil was confirmed by Fourier-transform infrared (FTIR) and nuclear resonance magnetic (NMR) spectroscopy. It was found that the incorporation of only 7.5 wt% of PLO was sufficient to change the UL-94 fire class of PBT from non-rating to V-0. The flame-retardancy mechanism of the PBT/PLO blends was evaluated from TGA-FTIR analysis. The combined effects of the gas phase mechanism and the dripping tendency of the blends aided to retard the flame propagation effectively. As the synthesized PLO and PCO contained high free fatty acids, the acid-ester exchange reaction occurred in the blends to form oligomers during the ignition. As a result, the blend dripped immediately and the drips carried all the heat to prevent fire. This work suggests that this sustainable biobased FR could be a desirable alternative to halogen-based FRs for PBT and other engineering polymers to develop more environmentally friendly FR products for various future applications.