LOI Value Research Articles

Investigation of MXene@APP/FDS/AgNPs@EG system for preparing multifunctional thermoplastic polyurethane composites with flame retardancy and electromagnetic shielding performance

In order to comply with the requirement of flame retardancy and electromagnetic interference (EMI) shielding for encapsulant applied to electronic devices, multifunctional thermoplastic polyurethane (TPU) composites are prepared with the construction of an intumescent flame retardant (IFR) system comprising internal conductive network. In this work, ammonium polyphosphate wrapped with MXene (MXene@APP) is attained by microencapsulation, and expandible graphite decorated with Ag nanoparticles (AgNPs@EG) is prepared by the reducibility of silk sericin. The IFR system with conductivity is established by the introduction of MXene@APP, AgNPs@EG and furfural-derived Schiff base (FDS). The as-prepared TPU/MXene@APP/FDS/AgNPs@EG composites are able to attain significant elevation in flame retardancy, exhibiting V-0 rating and a LOI value of 33.1 %. Furthermore, TPU composites are integrated with warp-knitted metal mesh (WMM) to fabricate TPU@WMM coated fabric, displaying strengthened electromagnetic interference (EMI) shielding effectiveness (SE) of 37.53 dB within X band. This work provides a potential method for application in encapsulant with flame retardancy and electromagnetic protection.

Alkoxysilyl derivative of carbamoylphosphonate as a flame retardant modifier of cotton fabrics

This research describes the synthesis of a silane derivative containing phosphorus and nitrogen atoms, leveraging their synergistic flame retardant effect through the incorporation of a PH bond to the isocyanate moiety. The synthesized silane featured alkoxysilyl groups, facilitating permanent bonds with the cotton fabric surface via hydrolysis. Cotton fabrics were modified using silane solutions of varying concentrations (2.5 %, 5 %, and 10 %) through a dip-coating process to determine the effect of the modifier amount on fabric properties. The modified fabrics were subjected to FT-IR, TGA, SEM, and EDS analyses, as well as microcalorimetric and LOI tests, to assess changes in flammability. FT-IR, SEM/EDS, and add-on analyses confirmed effective coverage of the cotton fabric with the flame retardant. Thermogravimetric tests indicated a significant reduction in the mass loss rate during thermal degradation. LOI analyses demonstrated a decrease in flammability (increase in LOI value), while microcalorimetric tests showed a substantial decrease in the heat release rate, correlating with increased modifier concentration on the fabric surface. Post-washing analyses revealed that, although some of the modifier was washed out, the samples still retained reduced flammability.

Designing of carbon nanohorn‐based heterostructure for improved mechanical properties, flame retardancy, and hydrophobicity of composite aerogels

AbstractDeveloping flame‐resistant thermal insulation aerogels with strong mechanical properties is crucial for addressing the fire hazards in high‐rise buildings. Carbon nanomaterials have garnered significant attention for enhancing the flame retardancy and mechanical properties of polymers due to their safety, nontoxicity, and low additions. In this work, the effect of single‐walled carbon nanohorns (SWCNHs) on the mechanical properties, thermal insulation properties, thermal stability, flame retardancy, and hydrophobicity of polyvinyl alcohol/KH560/phytic acid composite aerogel (PKASx) was investigated. By adjusting the concentration of SWCNHs, the mechanical properties of the aerogel were significantly improved, owing to robust interactions between SWCNHs and the matrix. However, a declining trend was observed in both the compressive modulus and specific modulus when the quantity of SWCNHs exceeded 0.3%. Simultaneously, the PKAS0.3 aerogel exhibited remarkable flame retardancy and self‐extinguishing characteristics. It possessed a high LOI value of 34.2 ± 0.2%, with a 25.2% reduction in pHRR and an 18.6% reduction in THR. Moreover, the analysis of TSP and SPR curves affirmed that the inclusion of SWCNHs effectively minimized the production of gaseous by‐products during combustion. In addition, the introduction of SWCNHs introduced a trade‐off in the roughness of the aerogel. The maximum contact angle occurred at the optimal concentration of SWCNHs.

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.

Preparation of core-shell melamine cyanuric based flame retardant for improving comprehensive performance of polyamide 56

The preparation of flame retardant PA56 material with superior thermal stability, melt-drop resistance, and mechanical properties has been challenging in industry. Herein, we prepared a core-shell MCA-based flame retardant (BP-MCA) for PA56 via the hydrogen bond self-assembly and solvent exchange strategies. The hydrogen bond self-assembly strategy modulates the morphology of MCA-based flame retardant. The solvent exchange strategy further improves the dispersion, and char-forming properties of flame retardant. Compared with PA56, PA56/BP-MCA achieves the UL-94 V-0 rating, LOI value of 32.5 % and THR value of 55.2 MJ/m2. Besides, PA56/BP-MCA exhibits superior mechanical properties due to the larger aspect ratio and better dispersion of BP-MCA.

Biomimetic aerogel coatings for flexible polyurethane foams with superior flame retardancy, mechanical flexibility and antibacterial properties

Flexible polyurethane foams (FPUFs) are widely used in various industries due to its high rebound characteristics, but its inherent flammability significantly affects its application. In this study, inspired by the structure of shell nacre, an aerogel coating with gelatin, boric acid and tetrakis hydroxymethyl phosphonium sulfate (THPS) as raw materials was designed. Owing to the hydrogen bonding interactions among the above molecules, the aerogel coating exhibits strong interfacial adhesion to the FPUF substrate, and the peel strength even surpasses the intrinsic strength of the FPUF matrix. Moreover, the coated FPUFs exhibit exceptional flame retardant and thermal insulation properties. The LOI value reaches as high as over 80 % and easily achieves a UL-94 V0 rating. During combustion, the coated FPUFs illustrate extremely low heat and smoke release. Meanwhile, the coated FPUFs still maintain excellent resilience. In addition, the THPS endows coated FPUFs with excellent antibacterial properties and exhibits a highly inhibition against Escherichia coli and Staphylococcus aureus.

Construction of multifunctional coating for polyester/cotton fabrics using layer-by-layer assembly of biomaterials and spraying of fluorine-free polydimethylsiloxane

Polyester/cotton (T/C) fabric has the excellent properties of both cotton and polyester, and is widely used in the textile field. However, the fabric is highly flammable. Further, the facile growth of bacteria on the fabric surface may lead to contamination that precludes application in some areas. Multifunctional T/C fabrics with flame retardancy, superhydrophobicity and antibacterial property have been prepared by construction a surface coating of phytic acid, chitosan, ferric ion and polydimethylsiloxane via a finishing method. The coated T/C fabric exhibits excellent flame retardancy with a LOI value of 30.2 % and a char length of 10.0 cm for combustion. The coated T/C fabrics also display superhydrophobicity with a water contact angle (WCA) greater than 150°. The multifunctional coated T/C fabrics exhibit good antibacterial properties with inhibition of bacterial growth for E. coli and S. aureus of over 98 %. Thermogravimetry and scanning electron microscopy suggest that the multifunctional coating on T/C fabrics produces an intumescent flame retardant effect involving both the promotion of char formation in the condensed phase and the evolution inert species to the gas phase to dilute the fuel load in the combustion zone. A new strategy for the preparation of textile fabrics with good flame retardancy, superhydrophobicity and antimicrobial properties by application of a multifunctional surface coating has been developed.

Synergetic improvement of flame retardancy and heat resistance of cationic waterborne polyurethanes by introducing a DOPO-containing flame retardant

The cationic waterborne polyurethanes (CWPU) exhibit excellent affinity towards various materials possessing negative surface charges owing to its positive charge. However, its limited heat resistance and flame retardancy greatly restrict its practical application. In this work, we synthesized a flame retardant, 2-(6-oxido-6H-dibenz〈c,e〉〈1,2〉oxaphosphorin-6-yl)-1,4-hydroxyethoxyphenylene (DOPO-HQ-HE), and incorporated it into the skeleton of cationic waterborne polyurethanes to prepare flame-retardant cationic waterborne polyurethanes (CWPU-DHHxs). The obtained CWPU-DHHxs showed excellent flame retardancy, in which the LOI value of CWPU-DHH12 reached over 26.9 vol% and passed UL-94 V-0 rating. The findings showed that CWPU-DHHxs exhibited remarkable efficacy in both the vapor and condensed phase during combustion. Moreover, the incorporation of DOPO-HQ-HE led to a significant improvement in heat resistance performance by facilitating enhanced microphase separation. Meanwhile, the major comprehensive performance of CWPU-DHHxs, including emulsion storage stability, thermal stability, mechanical performance, and transparency were effectively preserved.

A biomass phosphonamide enables biodegradable polylactide with favorable flame retardancy and rapid crystallization

PLA is widely known as biodegradable plastics whose further application in fields such as automotive and architectural is still constrained by its flammability and unsatisfactory crystallization properties. To address the aforementioned concerns, a novel biomass phosphonamide PDPA was synthesized with chemical structure confirmed by FTIR, NMR and elemental analysis tests. Immediately thereafter, PLA/PDPA composites were prepared by melting blending, with a focus on flame retardancy, crystallization properties and flame-retardant mechanism. As expected, PDPA efficiently enhanced both the flame retardancy and crystallization properties of PLA. Specifically, the PLA/4.0PDPA obtained UL-94 V-0 grade and the LOI value increased to 28.6 % with only 4 wt% PDPA added, which comes down to the superior free radical capture and dilution effect of PDPA in the vapor phase and the melting droplet effect. More appealingly, the crystallinity of PLA/4.0PDPA was significantly enhanced to 43.4 % from 2.5 % of PLA, and the shortest t1/2 was 4 mins in the isothermal crystallization process due to the excellent heterogeneous nucleation of PDPA. Moreover, PLA/PDPA composites maintain almost the same mechanical performance as pure PLA. In brief, this work provides a green strategy for the preparation of PLA composites with excellent comprehensive performance and shows great potential in engineering materials.

Functionalized Zr‐MOFs for Enhancing Flame Retardancy and Smoke Suppression Performance on TPU

AbstractMetal‐Organic Framework (MOF) materials can be used as flame‐retardants and smoke suppressants for polymers. As a MOF material, UIO‐66(Zr) possesses higher thermal stability and controllable pore size. In this paper, UIO‐66(Zr), NH2‐UIO‐66(Zr), and SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr) was fabricated to improve the flame retardant and smoke suppression performance of thermoplastic polyurethanes (TPU). The experimental results show that compared with neat TPU (LOI value 19.1 %), 2 % usage of UIO‐66(Zr) and NH2‐UIO‐66(Zr) can endow TPU with 26 % LOI value and vertical combustion rating of V‐1. Moreover, SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr) provide TPU with above 27.8 % LOI value and vertical combustion rating of V‐0. Meanwhile, the CCT results showed that the peak heat release rate and total heat release of TPU‐U5 (added 2 % GO‐modified NH2‐UIO‐66(Zr)) are 299.52 Kw ⋅ m−2 and 68.21 MJ m−2, much lower than that of neat TPU, which are 1180.05 Kw ⋅ m−2and 104.87 MJ m−2, respectively. The TGA, char residue EDS and XRD analysis show that SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr) could generate zirconium metal oxide during the combustion process, which acts as a physical barrier to prevent the TPU matrix by promoting the generation of carbonization layer. The zirconium metal oxide and carbonization layer also can confine flammable gases, which can delay the ignition time and hinder the overflow of gas. In addition, NH2‐UIO‐66(Zr) could generate non‐flammable N2 diluting the concentration of flammable gases. The mechanical properties of TPU composites can maintain more than 87 % of the neat TPU after the addition of 2 % SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr). These results indicate that functionalized Zr‐MOFs composites could act as excellent flame‐retardants in TPU.

Asymmetric ionic bond shielding encountering with carboxylate capturing metal ions for enhancing the flame retardant durability of regenerated cellulose fibers

Enhancing the flame retardancy and durability of cellulose fibers, particularly environmentally friendly regenerated cellulose fibers types like Lyocell fibers, is essential for advancing their broader application. This study introduced a novel approach to address this challenge. Cationic-modified Lyocell fibers (Lyocell@CAT) were prepared by introducing quaternary ammonium structures into the molecular chain of Lyocell fibers. Simultaneously, a flame retardant, APA, containing -COO−NH4+ and -P=O(O−NH4+)2 groups was synthesized. APA was then covalently bonded to Lyocell@CAT to prepare Lyocell@CAT@APA. Even after undergoing 30 laundering cycles (LCs), Lyocell@CAT@APA maintained a LOI value of 37.2 %, exhibiting outstanding flame retardant durability. The quaternary ammonium structure within Lyocell@CAT@APA formed asymmetric ionic bonds with the phosphate and carboxylate groups in APA, effectively shielding the binding of Na+ ions with phosphate groups during laundering, thereby enhancing the durability. Additionally, the consumption of Na+ ions by carboxylate groups further prevented their binding to phosphate groups, which contributed to enhance the durability properties. Flame retardant mechanism analysis revealed that both gas and condensed phase synergistically endowed excellent flame retardancy to Lyocell fibers. Overall, this innovative strategy presented a promising prospect for developing bio-safe, durable, and flame retardant cellulose textiles.

Efficient fabrication of paper nanocomposites for superior flame retardancy and strengthening properties

Innovative and cost-effective paper sheets with superior fire safety and reinforcement properties have been developed. The paper sheets were fabricated via valorization of agricultural waste to paper and then coated with nanoparticles. Paper attained from rice straw was used to create the sheets. Afterward, bentonite sheets were incorporated in these sheets, and finally, PbO nanoparticles were coated on prepared paper nanocomposites. The mass ratio of bentonite sheets was altered. The flammability and mechanical properties of the developed paper nanocomposites were studied. The flame retardancy of developed paper nanocomposite was significantly improved achieving LOI value of 24% compared to 20% for bentonite and PbO nanoparticle-free sample. Additionally, the tensile strength was improved recording 44% enhancement compared to unmodified sample. Furthermore, the flame retardancy mechanism was proposed and studied.

Eco-friendly, efficient and durable flame retardant lyocell fabrics prepared via a feasible grafting of taurine

Inspired by alkaline oxidative degradation of cellulose, a novel eco-friendly scenario for preparation of flame retardant lyocell fabrics was developed by the chemical grafting of biomass taurine. FTIR and XPS results verified the establishment of a covalent bond between taurine and lyocell fabric. Thermogravimetric analysis and vertical combustion test proved the improved char-forming ability and flame resistance of the grafted fabric. The THR and pHRR of the finished fabric were successfully reduced by 67.3 % and 89.9 % respectively after modification. In addition, after 50 wash cycles, the LOI value of the grafted fabric was maintained at 29.5 %. The gas-phase and condensed-phase flame retardant mechanisms were proposed from the analyses of pyrolysis gaseous products and char residue of the modified fabrics. The modification process is simple to operate and provides a feasible green flame retardant strategy for flammable lyocell fabrics.

Flame retardancy, photostability, and thermal properties of vanillin-epoxidized soybean oil composites reinforced with walnut shell

Vanillin produced from lignin is an environmentally friendly compound having various active structures that can be crosslinked with hexanediamine and epoxidized soybean oil (ESO) to form water resistant composite. Inclusion of ammonium dihydrogen phosphate (ADP) could render the composite flame retardant, but its mechanical properties could be influenced. Therefore, walnut shell powder (WSP), as a common biomass waste, can be incorporated to improve its hardness and compressive strength. A matrix named VHEA was prepared by the condensation of vanillin, hexanediamine, ESO, and ADP. WSP was used as the skeleton for blending with VHEA to create VHEAW composite. Mechanical properties, dimensional stability, UV-resistance, thermal conductivity and flame retardancy of the composites were evaluated. The inclusion of WSP at a ratio of 1:1 to VHEA improved the compressive strength, Brinell hardness and flexural strength of the composite. Meanwhile, its water contact angle reaches 131.48 °, indicates its superior hydrophobicity. It also has high UV resistance and good flame retardancy as the LOI value is as high as 35.1 %, and its peak heat release rate is as low as 123.19 kW/m2. Its outstanding thermal insulation and flame retardancy, combined with excellent UV-resistance, render it suitable for various building components, including roofing, exterior siding, windows, and doors.

Ultrahigh Heat/Fire-Resistant, Mechanically Robust, and Closed-Loop Chemical Recyclable Polycarbonate Enabled by Facile Bond Dissociation Energy Modulation.

Plastics serve as an essential foundation in contemporary society. Nevertheless, meeting the rigorous performance demands in advanced applications and addressing their end-of-life disposal are two critical challenges that persist. Here, an innovative and facile method is introduced for the design and scalable production of polycarbonate, a key engineering plastic, simultaneously achieving high performance and closed-loop chemical recyclability. The bisphenol framework of polycarbonate is strategically adjusted from the low-bond-dissociation-energy bisphenol A to high-bond-dissociation-energy 4,4'-dihydroxydiphenyl, in combination with the incorporation of polysiloxane segments. As expected, the enhanced bond dissociation energy endows the polycarbonate with an extremely high glow-wire flammability index surpassing 1025°C, a 0.8mm UL-94V-0 rating, a high LOI value of 39.2%, and more than 50% reduction of heat and smoke release. Furthermore, the π-π stacking interactions within biphenyl structures resulted in a significant enhancement of mechanical strength by as more as 37.7%, and also played a positive role in achieving a lower dielectric constant. Significantly, the copolymer exhibited outstanding closed-loop chemical recyclability, allowing for facile depolymerization into bisphenol monomers and the repolymerized copolymer retains its high heat and fire resistance. This work provides a novel insight in the design of high-performance and closed-loop chemical recyclable polymeric materials.

Cyclodextrin-based host-guest hierarchical fire retardants: Synthesis and novel strategy to endow polylactic acid fire retardancy and UV resistance

β-Cyclodextrin (β-CD) with a cage-like supramolecular structure possesses the hydrophobic internal ring and external hydroxyl groups, which are beneficial for intramolecular interactions known as “host-guest” chemistry. This study presents a β-CD-based three-functions-in-one and host-guest fire retardant (βCD-MOF@Schiff base), which incorporates self-crosslinking Schiff base into its cavity and modification of its surface by metal-organic framework (MOF). With the presence of 5 wt% of βCD-MOF@Schiff base, the LOI value of PLA composites increased to 29 % and showed 15 %, 17 % and 62 % reductions in peak heat release rate (pHRR), total heat release (THR), and the yield of hazard gas carbon monoxide, respectively. The mode action of FR on fire retardation of PLA showed that the FR promoted the char formation with higher thermal stability and graphitization, and modified the decomposition path of PLA. Additionally, the PLA composites exhibited enhanced UV resistance in the UVA and UVB areas with improved UV absorbance and the UPF values improving and doubling. This work develops a new approach to preparing biodegradable FR, which simultaneously endows fire safety and anti-UV properties for PLA.

Construction of efficient and environmentally friendly bio-based flame retardant cotton fabric through layer by layer self-assembly of alkylammonium functional silsesquioxane/phosphorylated sodium alginate

As an important source of green cleaning flame retardants, bio-based materials have been widely studied by researchers. However, the development of efficient biobased flame retardants and convenient finishing methods was of great significance for the functional finishing of materials. Herein, a convenient and efficient flame retardant cotton fabric was prepared via layer by layer self-assembly (LbL) by alternating precipitation of a novel bio-based flame retardant phosphorylated sodium alginate (PSA) and alkylammonium functionalized siloxane (A-POSS). The effect of coating number on flame retardancy and thermal properties of coated cotton fabric was systematically studied. Thermogravimetric analysis (TGA) results showed that residual char contents of AP/PS-15BL under air and N2 atmospheres increased by 252.0% and 225.2%, respectively, compared with control cotton. In vertical flammability tests, both the AP/PS-10BL and AP/PS-15BL showed self-extinguishing behavior and successfully passed the UL-94 V-0 rating. More importantly, the LOI value of AP/PS-15BL was significantly increased to 35.0% from 20.0% of pure cotton fabric. Additionally, coated samples showed good mechanical properties and washable resistance. In CONE test, the peak heat release rate (PHRR) and total heat release rate (THR) of AP/PS-15BL decreased by 89.3% and 49.3% respectively, compared with control cotton. Therefore, this green and convenient flame-retardant finishing method has great application potential in the multi-functional finishing of cotton fabrics.

A nimble strategy for enabling bioderived flame retardants with strikingly enhanced interfacial compatibility in poly (lactic acid) composites

The utilization of bioderived flame retardants in biodegradable poly (lactic acid) (PLA) has profound practical implications for extending the widespread application of PLA composites and protecting the environment. Nevertheless, there are still certain challenges that require prompt attention, especially the ineffectiveness of bio-based flame retardants and their deterioration of the mechanical properties of PLA. This work introduced triglycidyl isocyanurate (TGIC), which has multiple epoxy functions, into the self-assembly process of phytic acid (PA) and chitosan (CS). The epoxy-modified bioderived flame retardant PA@CS-TGIC (PCT) was well dispersed in the PLA matrix and had a strong interfacial adhesion, while also TGIC had a synergistic char-forming effect. By compounding epoxy-modified ammonium polyphosphate (MAPP), 3%PCT/MAPP-PLA composites may reach a LOI value of 28.8 % and UL-94 V-0 rating. Simultaneously, the melting droplets had been considerably reduced. Tensile strength of the 3%PCT/MAPP-PLA composites was 67.0 MPa, 10.8 % higher than that of pure PLA. This work paves a new avenue for the development of PLA composites with robust mechanical and flame retardant properties.

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.

Fully bio-based intumescent flame retardant hybrid: A green strategy towards reducing fire hazard and improving degradation of polylactic acid

Polylactic acid (PLA) is a promising renewable polymer material with excellent biodegradability and good mechanical properties. However, the easy flammability and slow natural degradation limited its further applications, especially in high-security fields. In this work, a fully bio-based intumescent flame-retardant system was designed to reduce the fire hazard of PLA. Firstly, arginine (Arg) and phytic acid (PA) were combined through electrostatic ionic interaction, followed by the introduction of starch as a carbon source, namely APS. The UL-94 grade of PLA/APS composites reached V-0 grade by adding 3 wt% of APS and exhibited excellent anti-dripping performance. With APS addition increasing to 7 wt%, LOI value increased to 26 % and total heat release decreased from 58.4 (neat PLA) to 51.1 MJ/m2. Moreover, the addition of APS increased its crystallinity up to 83.5 % and maintained the mechanical strength of pristine PLA. Noteworthy, APS accelerated the degradation rate of PLA under submerged conditions. Compared with pristine PLA, PLA/APS showed more apparent destructive network morphology and higher mass and Mn loss, suggesting effective degradation promotion. This work provides a full biomass modification strategy to construct renewable plastic with both good flame retardancy and high degradation efficiency.