Good Flame Retardancy Research Articles

Fluorine chemistry in lithium-ion and sodium-ion batteries

As the peculiar element in the Periodic Table of Elements, fluorine gas owns the highest standard electrode potential of 2.87 V vs. F-, and a fluorine atom has the maximum electronegativity. Benefiting from the prominent property, fluorine plays an important role in the development of lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) in terms of cathode materials (transition metal fluorides, fluorinated polyanionic compounds), electrolytes, and interfaces. In cathode materials, the highly electronegative renders enhanced ionic character of transition metal fluorine bonds and correspondingly high working potential in electrolytes; fluorinated electrolytes possess good antioxidant ability and flame retardance, which can significantly improve the thermal safety of a battery. On an electrode-electrolyte interface, the fluorine-rich inorganic component (such as LiF and NaF) is essential for the formation of a robust and stable solid electrolyte interface on anodes. Despite the remarkable advances achieved in fluorinated cathodes, electrolytes, and interfaces, there is still a lack of comprehensive understanding of the function of fluorides in LIBs and SIBs. Accordingly, this review briefly summarized the recent progress of fluorine-based electrodes, electrolytes, and interfaces and highlighted the correlation between the composition, property, and function to reveal the fluorine chemistry in LIBs and SIBs. This review will provide guidance for the rational design and targeted regulation of fluorine-dominated high-performance electrode materials, functionalized electrolytes, and consolidated interfaces.

Thermal Stability, Flame Retardancy and Flame Retardant Mechanisms of Hollow Glass Microspheres/Montmorillonite/Epoxy Sheet Molding Compound Composites

Epoxy sheet molding compound (ESMC) composites have excellent mechanical properties, dimensional stability and electrical insulation, and are widely used in the automotive industry. In our previous work silane coupling agent modified, hollow glass microspheres (SiHGM) and montmorillonite (MMT) were incorporated to enhance the mechanical properties of the ESMC composites. It was found that the ESMC composites containing MMT (EP/SiHGM/MMT-1) exhibited excellent mechanical strength. However, the flammability of the epoxy resin (EP) limits the use of ESMC composites for applications that require good flame retardancy. In this paper we describe our research in which MMT was used to increase the flame retardancy of ESMC composites. The results showed that the addition of MMT made the ESMC composites have excellent flame retardancy. The limiting oxygen index (LOI) of the ESMC composites containing 1 phr MMT (EP/SiHGM/MMT-1) was 26.8%, which was 8.94% higher than that of the ESMC composites without MMT (EP/SiHGM/MMT-0). In addition, the peak heat release rate (PHRR), average heat release rate (AHRR) and total heat release (THR) of the EP/SiHGM/MMT-1 were 322.8 kW/m2, 95.3 kW/m2 and 38.6 MJ/m2, respectively, which were 22.6%, 8.2% and 8.0% lower than those of EP/SiHGM/MMT-0. The carbon monoxide production (COP) and carbon dioxide production (CO2P) of EP/SiHGM/MMT-1 were 0.0092 g/s and 0.2071 g/s, respectively, which were 34.3% and 22.8% lower than those of EP/SiHGM/MMT-0. The fire growth index (FGI) of EP/SiHGM/MMT-1 was 2.4, which was a decrease by 29.4% compared to EP/SiHGM/MMT-0. In addition, the flame retardant mechanisms were revealed. We suggest that MMT promoted dehydration and charring of the epoxy resin and helped construct an intact physical barrier, which had good blocking effects. The prepared composite has great application prospects for those occasions that require high flame retardancy. Thus, this work provides an innovative strategy for preparing low density epoxy composites with excellent flame retardancy and high mechanical properties.

A graphene@Cu-MOF hybrid synthesized by mechanical ball milling method and its flame retardancy and smoke suppression effect on EP

The traditional method of preparing graphene will cause serious environmental pollution, and the combustion of polymer materials will seriously harm people's health. In this paper, a Cu-MOF-coated graphene composite flame retardant (G@Cu-MOF) rich in flame retardant elements such as B and N was synthesized through green mechanical ball milling method. Flame retardants reduce the threat to the environment and people's lives and property. After adding 6 wt% G@Cu-MOF, the peak heat release rate, total heat release rate, CO production and CO2 production of epoxy resin (EP) composite samples decreased by 55, 14, 59, and 55%, respectively. This type of Cu-MOF releases incombustible gases such as boron trifluoride (BF3) and ammonia (NH3) during combustion, diluting the concentration of combustible gases and producing copper borate in the condensed phase. Cu2+ is reduced to Cu, and boron compounds are converted into boron oxides. The thermal conductivity of graphene can reduce the temperature of the matrix, and has good flame retardancy. It synergistically acts with Cu-MOF to promote the formation of high-quality residual char, and can significantly inhibit the heat and smoke release of EP. It plays a role in flame retardancy and protecting the substrate from fire. This study provides a new approach for preparing graphene hybrid flame retardants through mechanical ball milling, in order to improve the flame retardancy of EP and suppress the release of smoke and toxic gases.

Electrically conductive bamboo charcoal@cellulose nanofibrils based composite membranes designed for electromagnetic interference shielding and flame retardant

Recently, developing multifunctional biochar based materials has been concerned by experts and scholars, but the weak electrical conductivity of biochar itself will limit its application. Targeting this issue, electrically conductive bamboo charcoal (EBC) was constructed for catalytic carbonization by mixing ferric chloride with bamboo charcoal, followed by mixing cellulose nanofibrils (CNF) as the skeleton and a small amount of multi-walled carbon nanotubes (MWCNT) as the conductive enhancer to constract a conductive EBC@CNF@MWCNT composite aerogel by freeze drying. Subsequently, the aerogel was soaked with polydimethylsiloxane (PDMS) and hot pressed into a membrane. In the system, EBC and MWCNT were distributed uniformly in the CNF skeleton to form three-dimensional conducting network, the obtained conductive E @ CNF@M@PDMS composite membrane displayed excellent conductivity (47 S/m) and remarkable EMI shielding performance (39.5 dB, absorption loss of about 75%), as well as good flame retardant ability (LOI of 27.6%) and hydrophobicity (115.4°). Based on its outstanding properties and simple preparation, it is considered to provide a new strategy for developement of environmentally friendly multifunctional biochar based materials.

Enhancing flame retardancy of poly(lactic acid) with a novel fully biobased flame retardant synthesized from phytic acid and cytosine

AbstractIn order to reduce environmental pollution and improve material safety, biobased flame‐retardant polymers are gradually becoming a new trend. We synthesized a fully biobased flame retardant called PACY by reacting phytic acid (PA) and cytosine (CY) in water, and then mixed the flame retardant with biodegradable poly(lactic acid) (PLA) to obtain composites, characterizing the performance of the composites by microscopic morphology, thermal properties, flame‐retardant performance and so on. The test results showed that the PLA composite with 2 wt% PACY (PLA/2PACY) achieved UL‐94V‐1 and the PLA composite with 4 wt% PACY (PLA/4PACY) had a limiting oxygen index of 23.6%. Compared to pure PLA, PLA/4PACY had good flame retardancy with 12% less peak heat release and 19% less total heat release. Analysis of the flame‐retardant mechanism showed that PACY could promote the formation of a graphitized carbon layer after burning PLA, therefore enhancing the flame‐retardant properties of PLA. Through a thermal stability study, it was found that the temperature required for PACY mass loss of 5% was 275 °C and the residual weight reached 38% at 750 °C, which indicated high thermal stability and residual carbon rate. The addition of PACY also improved the thermal conductivity of PLA, with that of PLA/4PACY being 3.84 times higher than that of pure PLA. In addition, the tensile strength, flexural modulus, maximum force during impact and maximum energy received during fracture of PLA/4PACY increased by 3.3%, 8.1%, 29.2% and 17.5% respectively over pure PLA, effectively improving the mechanical properties of PLA. Overall, a fully biobased flame retardant was synthesized for improving the fire resistance of PLA degradable polymers. © 2023 Society of Industrial Chemistry.

Synthesis and application of silicone modified flame retardant for polyester fabric

The flame-retardant treatment of polyester fabrics has been widely reported, but most of these treatments cause a significant decrease in the fabric’s handle, such as fluffiness and softness. This study designed and synthesised a new phosphorus-nitrogen-containing silicone oil (PNSO). Then, PNSO as a flame-retardant was treated on polyester fabric through a pad-dry-cure procedure. The limiting oxygen index (LOI), afterflame time and damaged length of the finished polyester fabric (PNSO-F) were enhanced from 20.5%, 73.1 s and 26.8 cm to 28.3%, 4.5 s and 12.3 cm, respectively. After 12 washes, PNSO-F retained its good flame-retardancy and anti-dripping properties. Furthermore, the flame-retardant mechanism of PNSO on fabric was investigated using different spectral methods, which revealed that nitrogen acting in the gas phase, and phosphorus and silicone in the condensed phase worked together to produce a synergistic flame-retardant effect. In addition, KES tests indicated that the fluffiness and softness of PNSO-F were significantly improved.

Synthesis of Zinc Oxide Doped Magnesium Hydrate and Its Effect on the Flame Retardant and Mechanical Properties of Polypropylene.

In this work, an effective flame retardant consisting of nanoscale zinc oxide doped on the surface of hexagonal lamellar magnesium hydrate (ZO@MH) has been successfully synthesized via a hydrothermal process. Approximately 3-methacryloxypropyltrimethoxysilane (KH-570) is chosen as a modifier of ZO@MH for the purpose of enhancing the interfacial interaction between ZO@MH and the polypropylene (PP) matrix and reducing the agglomeration of ZO@MH. Afterwards, ZO@MH and KH-570 modified ZO@MH (KZO@MH) filled PP (PP/ZO@MH and PP/KZO@MH) composites are respectively prepared via the melt blending method. The flame retardant and smoke suppression properties of PP/ZO@MH and PP/KZO@MH composites are estimated by a cone calorimetry test (CCT). The peak value of the heat release rate of the PP/40KZO@MH composite is 327.0 kW/m2, which is 6.1% and 31.2% lower than that of the PP/40ZO@MH and PP/40MH composites, respectively. The lowest peak values of CO and CO2 production, 0.008 and 0.62 g/s, also appeared in the PP/40KZO@MH composite, which are 11.1% and 10.1% lower than those of the PP/40ZO@MH composite. Analysis of char residues indicates that nanoscale ZO and modification of KH-570 improve the amount and quality of char residues, which should be the main reason for the good flame retardant and smoke suppression properties of KZO@MH. Impact strength and nominal strain at break results show that the PP matrix is toughened by ZO@MH rather than KZO@MH. Tensile properties and the quantitative interfacial interaction calculated by the Turcsányi equation both prove the reinforcement of KZO@MH on the PP matrix.

A P/N additive to optimise the flame retardancy, low dielectricity and mechanical properties of EP composites

For expanding the application of epoxy resin (EP) in semiconductor packaging, the P/N flame retardant containing azole ring, designated as BT, was designed, synthesized, incorporated into EP, and flame retardant EP (FREP) was prepared. These resins were tested in terms of their thermal stability, flame retardant properties, mechanical properties, and dielectric properties. Owing to the excellent biphasic flame retardancy of BT, the samples reached the V-0 class of UL-94 flammability standards at 5 wt% BT with a 35.3% Limited Oxygen Index (LOI), which is 31.7% higher than that of EP . At the addition of 15 wt% BT (i.e., EP/BT15), the cone calorimetry test indicated that the sample's total exotherm and peak exotherm rates were reduced by 34% and 42%, in comparison to pure EP, respectively. The mechanical properties of FREP improved, and the tensile and flexural strengths increased by 9% and 10%, respectively, at 10 wt% BT addition. Moreover, the dielectric constant and dielectric loss of FREP decreased with increasing BT content. In this work, a simple strategy for the preparation of EP with good transparency, mechanical properties, flame retardancy and low dielectric constant is provided.

Water Hyacinth Fiber as a Bio-Based Carbon Source for Intumescent Flame-Retardant Poly (Butylene Succinate) Composites.

In this study, flame-retardant poly (butylene succinate) (PBS) composites were developed utilizing a bio-based intumescent flame retardant (IFR) system. Water hyacinth fiber (WHF) was used as a bio-based carbon source, while ammonium polyphosphate (APP) served as both an acid source and a blowing agent. Effects of WHF:APP weight ratio and total IFR content on the thermal stability and flammability of WHF/APP/PBS composites were investigated. The results demonstrated that the 15WHF/30APP/PBS composite with a WHF to APP ratio of 1:2 and a total IFR content of 45 wt% had a maximum limiting oxygen index (LOI) value of 28.8% and acquired good flame retardancy, with a UL-94 V-0 rating without polymer-melt dripping. Additionally, its peak heat release rate (pHRR) and total heat release (THR) were, respectively, 53% and 42% lower than those of the neat PBS. Char residue analysis revealed that the optimal WHF:APP ratio and total IFR content promoted the formation of a high graphitized intumescent char with a continuous and dense structure. In comparison to the neat PBS, the tensile modulus of the 15WHF/30APP/PBS composite increased by 163%. Findings suggested the possibility of employing WHF, a natural fiber, as an alternative carbon source for intumescent flame-retardant PBS composites.

The Flame Retardancy and Smoke Suppression Performance of Polyvinyl Chloride Composites with an Efficient Flame Retardant System

Polyvinyl chloride (PVC) is the most widely used general flame-retardant plastic worldwide; however, the large number of plasticizers added during processing significantly reduces its flame-retardant property. To prepare a new type of PVC material with highly efficient flame retardancy and smoke suppression, antimony trioxide (Sb2O3), talc powder, hydromagnesite, and zinc borate were added in different proportions to PVC to explore the flame-retardant properties, thermal weight, smoke density (Ds), and mechanical properties of the composite materials. Results showed that the limiting oxygen index value of each group was higher than 27% after adding talc powder, magnesite, and zinc borate to replace part of the Sb2O3. This value was within the refractory-grade level and indicated a good flame retardancy performance. The replacement effect was in line with the experimental expectation. The lowest Ds peak value was 656.4 when the flame retardants were added with 10 wt% Sb2O3, 50 wt% hydromagnesite, 20 wt% talc, and 20 wt% Zn3BO6. Compared with pure Sb2O3 as a flame retardant, the Ds peak value decreased by 46.7%. The thermogravimetric decomposition temperature of the composites in each group was generally higher than that of the group with pure Sb2O3 as a flame retardant, increasing by 45.3 °C. The thermal stability of the composites was improved, and the elongation at the break and tensile strength were 234.9% and 25.8 MPa, respectively, indicating good mechanical properties. The results showed that using compound flame retardants to replace most of the Sb2O3 is an effective technique for obtaining good flame retardancy and mechanical properties of PVC. This study, not only reduced the manufacturing cost of flame-retardant PVC, but also effectively reduced its smoke density and the time to reach the highest smoke density, which provided a research reference for the application and promotion of flame-retardant PVC.

Synchronous preparation and modification of LDH hollow polyhedra by polydopamine: Synthesis and application

Layered double hydroxides (LDH) have irreplaceable advantages in the field of polymer flame retardancy, but their thermal stability and compatibility with matrix still need to be improved. In this paper, the bottom-up method is adopted, and the phosphorus series flame retardant triphenyl phosphate (TPP) was first encapsulated inside ZIF-67. On this basis, ZIF-67 was etched to produce LDH while modified by polydopamine (PDA) concomitantly. An organic coated polydopamine hollow cage lamellar LDH microstructure loaded with TPP was constructed, and its structure-performance relationship was verified. When 2 wt% TPP@LDH@Co-PDA was added to the epoxy resin, the LOI value of the composite was increased to 29.4 %, the peak heat release was reduced by 43.1 %, and the smoke release was significantly reduced. The unique microstructure endows epoxy composites with good flame retardancy, improves mechanical properties, and provides a new solution to the migration problem of phosphorous based flame retardants.

Bio-inspired and green fabrication of superhydrophobic materials with good robustness, stability and flame retardancy for oil-water separation based on waste cotton

Recently, more and more attention has been paid to bionic superhydrophobic materials for treating the intricate oil-water mixture system for the sake of resource recovery and environmental protection. With the in-depth development of research, scientists have been committed to pursuing the superhydrophobic materials via the economical, clean, and environmentally friendly methods. The current bio-inspired innovation of this paper concentrates on constructing superhydrophobic porous materials based on green, low-cost, and renewable waste cotton via in situ hydrothermal growth and solution immersion strategy. As anticipated, the water contact angle (WCA) of the prepared superhydrophobic cotton materials reaches 158°, exhibiting good self-cleaning ability and oil/water separation efficiency (99% ± 1%). Compared with pure cotton, superhydrophobic cotton materials also possesses elevated flame retardancy. In addition, after 300 cm abrasive paper friction tests, 10 times oil-water separation tests, 7 days of acid and alkali immersion tests (pH=1, 13), salt water immersion tests, and UV irradiation tests, as-prepared cotton materials can still maintain excellent superhydrophobic properties. On the basis of this work, an effective, facile and environmentally-benign avenue for fabricating the super-hydrophobic materials has been exploited that displays the promising applications in fields of waste cotton recycling, oil spill treatment and oil/water separation.

Flame retardancy, dielectric performance, pyrolysis behavior of epoxy resin and cyanate ester composites containing a multifunctional flame retardant

AbstractIn this research, a novel multifunctional flame retardant (DSF) was prepared through a reaction involving 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO), 4‐amino‐trifluorotoluene, and salicylaldehyde, was characterized by FTIR and 1H NMR, and was employed to prepare a multifunctional epoxy resin and cyanate ester resin copolymer (EPCE). A comprehensive investigation was conducted to assess the mechanical performance, dielectric properties, thermal behavior, and flame retardancy of EPCE composites. The results indicate that the EPCE composite with 8 wt% DSF (EPCE/8DSF) attained a LOI value of 28.1 vol% and a V‐0 rating. The EPCE/8DSF demonstrated a reduction of 25.8% in the peak heat release rate and a decrease of 25.6% in the total heat release in comparison with EPCE. In addition, the EPCE/8DSF composite demonstrated a decrease in both the dielectric constant and dielectric loss at 10 MHz, representing values of 3.58 and 0.00744, respectively. Furthermore, the incorporation of higher DSF content into the EPCE led to a decrease in mechanical properties.Highlights A multifunctional flame retardant (DSF) was prepared by Kabachnik‐Fields reaction, and was used to fabricate multifunctional EPCE composites. EPCE/DSF composites have good flame retardancy. The prepared composites also have low dielectric constant and low dielectric loss.

Super-strong biomimetic bulk bamboo-based composites by a neural network interfacial design strategy

As a sustainable ecological material, bamboo has become a popular modern green building material because of its rich yield, lightweight, high strength and rich cultural heritage. However, due to the limitation of bamboo tube thickness, multiple thickness-direction laminations are usually required to achieve large-sized materials, which leads to a significant decrease in strength. Therefore, it is urgent to find a way produce high-strength bamboo engineering composites on a large scale. Herein, a neural network interface design strategy was proposed, and a mechanical dissociation and partial matrix removal pretreatment method was used to open the weak intercellular layer and bamboo cell wall layer to increase the resin permeation channels. This allowed the resin to form a multi-scale bonding interface between multiple dense bamboo layers, achieving the preparation of bulk bamboo-based composite with adjustable dimensions and properties. The neural network-like bonding interface could firmly fix the compressed bamboo cells and enhance the mechanical properties of the bamboo cell wall and intercellular layer of bamboo, resulting in a tensile strength of 853 MPa for the composite, which was nearly three times that of natural bamboo and significantly superior to many structural materials such as alloys and other bamboo-based composites. In addition, this material showed good mildew resistance, flame retardancy and dimensional stability. This large-size bamboo composites are easy to scale production, which can be used in fields such as wind turbine blades, building structures, and outdoor walkways in the future.

Preparation and Performance of Silicone Rubber Composites Modified by Polyurethane.

Silicone rubber composites with good comprehensive properties modified with polyurethane were obtained through mixing and vulcanizing methods. Firstly, the polyurethane prepolymer with double bonds was prepared by polytetrahydrofuran glycol (PTMG, Mn = 1000), isophorone diisocyanate (IPDI), and 2-hydroxyethyl methacrylate (HEMA). The prepolymer was then added to the silicone rubber compounds to prepare silicone rubber composites, combining the excellent properties of polyurethane with the silicone rubber materials. The effects of polyurethane content on the mechanical properties, insulation, hydrophobicity, thermal stability, and flame retardancy of composites were studied in detail. The results showed that the silicone rubber composites not only have good hydrophobicity, thermal stability and flame retardant properties, but the addition of polyurethane significantly improves the tensile strength at room and low temperatures and the volume resistivity of the materials. The tensile strength increased by 32.5%, and the volume resistivity nearly doubled. The excellent electrical insulation, high hydrophobicity and good mechanical properties make the silicone rubber composites appropriate for use in the field of polymeric house arresters.

Fabrication of inorganic coatings incorporated with phosphorus-nitrogen-functionalized graphene oxide nanosheets to improve waterborne polyurethanes fire retardancy

A new inorganic flame retardant P/N-GO was prepared by chemically modifying graphene oxide (GO) with phosphorus trichloride (POCl3) and 4,4-diamino-diphenylmethane (DDM). The P/N-GO was covalently grafted into a phosphorus-containing aqueous polyurethane (PWPU) system to prepare a flame-retardant nanocomposite (P/N-GO/PWPU). Due to the uniform distribution of P/N-GO in the polymer matrix, a strong interfacial adhesion can be formed and the mechanical properties of the WPU can be significantly improved. The mechanical strength of the composites increased from 4.56 MPa to 9.16 MPa. The LOI value of WPU increased from 25.5% to 30.5%, indicating that its flame-retardant properties were improved and met the standards for flame-retardant materials. At the same time, the peak heat release rate (PHRR) was reduced from 184.374 kW/m2 to 116.730 kW/m2, which showed good flame retardant properties of P/N-GO/PWPU and was favourable for expanding the application scope and safe use of WPU.

Molecular design and properties of a P‐N synergistic flame retardant epoxy resin curing agent

AbstractThe utilization of epoxy resin (EP) is widespread across various industries. Nevertheless, its combustibility restricts its broader utilization. Additive flame retardants have proven effective in enhancing EP flame retardancy in recent decades. However, poor weather and aging resistance have always been the defects of added flame retardants. A reactive flame retardant (VPD) was synthesized from 3, 5‐diamino‐1, 2, 4‐triazole and phenylphosphonic dichloride, and was used to prepare VPD/EP flame retardant epoxy thermosets. The mechanical properties of the VPD/EP flame retardant epoxy thermosets are lower than those of pure epoxy, because the distance between molecules of VPD is increased compared with that of DDM, the cross‐linking density of the polymer after curing is decreased, and the intermolecular force is reduced. The VPD/EP flame retardant epoxy thermosets have a 40% reduction in total heat release compared to pure EP, an increase in limiting oxygen index value from 24.7% (pure EP) to 29.4%, and a V‐1 rating in UL‐94 testing. The obtained EP has not only good flame retardancy but also better weather resistance and aging resistance than additive flame retardants.Highlights An intrinsic flame‐retardant P and N coacting EP was designed and synthesized. The intrinsic flame‐retardant EP has excellent weather and aging resistance. The presence of the P, the residual char generated by combustion is denser.

Formaldehyde-free durable flame-retardant finishing for polyester/cotton blended fabrics through chemical grafting and cross-linking

A neotype high molecule reactive flame retardant, phosphoramide ammonium salt of polyethyleneimine derivatives for polyester/cotton (TC) blended fabrics was synthesized, and its structure and thermostability was characterized by 1H, 31P- nuclear magnetism resonance (1H NMR, 31P NMR), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric (TG) analysis. Results of FTIR, X-ray photoelectric spectrometer, surface morphology and energy dispersive X-ray and durability testing for the treated TC samples indicated that the flame retardants uniformly grafted onto the surface of fabrics especially on cellulose fibers. Vertical flame test, limiting oxygen index (LOI) values, conical calorimetric measurements showed a good flame retardancy of the treated fabrics. LOI of the treated fabric increased to 28.8 % at 14.8 % loading rate of flame retardants, and the loading rate remained above 93 % after 50 laundering cycles under AATCC 61–2013 3A standard. TG and TG-FTIR results suggested that the synthesized high molecular compounds mainly performed a condensed phase mechanism of flame retardancy. The finished fabrics tremendously sustained the original tensile strength. These results revealed that this high molecule reactive phosphoramide ammonium phosphate compounds can effectively endow a stable flame retardancy to the composite polyester/cotton blended textiles.

Synthesis of aluminum bis(hydroxy‐phenyl‐methyl)phosphinate and its synergistic flame retardant mechanism in PLA

AbstractIn this paper, we report on the synthesis of a new aluminum bis(hydroxy‐phenyl‐methyl)phosphinate, AlBPi, under mild reaction conditions. The product structure was confirmed via characterization, and its thermal stability and flame retardant properties were assessed. To improve the flame retardant properties, we employed ammonium polyphosphate (APP) as a synergist with AlBPi. The PLA composite material containing 10% AlBPi and 5% APP achieved an LOI of 28.1% and a UL‐94 rating of V‐1. Cone calorimetry tests showed a significant reduction in PHRR, THR, PSPR, and TSP for the PLA/AlBPi/APP composite compared to the pure and PLA/AlBPi materials. SEM analysis revealed a continuous and dense char layer on the residual surface of the synergistic flame retardant sample. AlBPi and APP exhibited excellent synergistic flame retardant effects, with both releasing a large amount of PO·free radicals. APP was also able to release inert gas, exhibiting excellent flame retardant effects in the gas phase. Additionally, APP improved the charring performance of AlBPi and formed a compact char layer on the material surface, achieving good flame retardant effects in the condensed phase. Therefore, the AlBPi and APP synergistic flame retardant system can be considered a viable flame retardant additive for PLA.Highlights A novel flame retardant AlBPi was synthesized. AlBPi and APP demonstrate good synergistic flame retardant performance in PLA. AlBPi and APP play a flame retardant role in both gas and condensed phases.

Effects of hexa (ethyl lactate)-cyclotriphosphazene on flame retardancy and mechanical properties of polylactic acid

Using biobased additives to improve the performance of polylactide (PLA) is important for maintaining its sustainability. In this work, an eco-benign flame retardant HELCP was synthesized by reacting ethyl lactate with cyclotriphosphazene. The HELCP was used to modify the flame retardancy of PLA. A small amount of 5.0 wt% HELCP endows PLA with a UL-94 V0 rating and a limiting oxygen index of 25.3 vol%. The mechanical properties and transparency of PLA/HELCP blends is almost the same as neat PLA. Moreover, the molecular weight of PLA blends does not decrease but increase instead. The phosphazene group of HELCP plays an important role in gas phase and the plasticization of HELCP shows a certain melting-away effect which is the flame-retardant mode of action in this system. The ethyl lactate part of HELCP undergoes ester exchange reactions with PLA and improves the compatibility between PLA and HELCP. This work provides a novel method for preparing PLA blends with good flame retardancy and mechanical properties.