Improving the flame retardancy of Lyocell fibers without compromising their mechanical properties is the key to expanding their high-end applications. To achieve this goal, an innovative phosphorus-free flame-retardant modification strategy of "crosslinking protection first and then directional oxidation" was proposed. Melamine-crosslinked Lyocell fibers (MC@Lyocell) were constructed through the treatment of hydroxymethylated melamine, which were then directionally oxidized by a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) mediated NaClO oxidation system to in-situ generate sodium carboxylate (-COONa+) groups of cellulose fibers to obtain high flame-retardant oxidized MC@Lyocell fibers (OMC@Lyocell). The modified fibers exhibited significantly enhanced flame retardancy: Limiting oxygen index (LOI) increased from 17.0% to 30.5%, the peak heat release rate (PHRR) and total heat release (THR) decreased by 79.6% and 50%, respectively. Meanwhile, the structural integrity and mechanical properties were well maintained. Compared with the original fibers, the crystallinity only slightly decreased by 8%similar to 15%, with slower mass loss and a decline of polymerization degree. The melamine crosslinked network confines oxidation to cellulose crystal surfaces and amorphous regions, resolving the contradiction between carboxyl generation and mechanical property decrease. This environmentally friendly and efficient phosphorus-free strategy provides a new direction for preparing high-performance, structurally stable flame-retardant cellulose fibers.

Cellulose is an important natural carbohydrate polymer, and natural or regenerated cellulose fibers are widely used in many fields, but the flammability of cellulose fibers limits their further development. To address the issue, an in situ growth of P and N flame retardant chelates (IGPN) was employed in a LiCl/N, N-dimethylacetamide (DMAc) solvent system to produce flame retardant cellulose fibers (Cellulose-IGPN@Li). X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) proved the successful synthesis of Li-containing IGPN (IGPN@Li) as well as the effective introduction of IGPN@Li into the fibers. The limiting oxygen index (LOI) value of Cellulose-IGPN@Li achieved 29.6% and remained at 28.7% even after 30 laundering cycles (LCs). In addition, the peak heat release rate (PHRR) and total heat release (THR) were reduced by 65% and 41%, respectively. Thermogravimetric-infrared (TG-IR) and cone calorimetry (CC) tests confirmed that IGPN@Li played an important role in the gas and condensed phases. Moreover, Cellulose-IGPN@Li had good antibacterial properties and moisture-dependent conductivity. This work provides a novel production method of durable flame retardant cellulose fibers with integrated potential greenness and economy.

Developing high-performance epoxy resins (EP) that integrate outstanding flame retardancy, mechanical reinforcement and optical transparency is a persistent challenge, often hindered by the detrimental effects of conventional additives. Herein, a novel hyperbranched polymeric flame retardant (HPBAE) containing phosphorus and borate ester moieties was synthesized from boric acid, ethanolamine and phenylphosphonic dichloride. Remarkably, incorporation of merely 2 wt% HPBAE substantially boosted the flammability resistance of resin to the UL-94 V-0 rating with 32.9% limiting oxygen index (LOI) and a 23.4% suppression in the peak heat release rate (PHRR). The superior flame retardancy arises from dual-phase action: condensed-phase formation of a P/Brich thermal barrier char and gas-phase release of phosphorus radicals that quench H center dot/HO center dot combustion intermediates. Relative to pure EP, the EP/HPBAE-2 exhibited a 57.9% enhancement in tensile strength while retaining the optical transparency. The synergistic effects imparted by HPBAE not only provide a balanced property profile but also offer a viable design paradigm for developing high-performance, transparent and flameretardant epoxy composites.

To achieve the reuse of polymer material waste, polyacrylonitrile (PAN)-based flame-retardant aerogels (PAN@HA-aer, PAN@HA@PCA-aer) were prepared using waste PAN fiber as raw materials. The cyano groups of PAN were modified via amidoximation with hydroxylamine hydrochloride and functionalized by 3,4-dihydroxybenzaldehyde. The test results indicated that the self-crosslinking effect of amidoxime groups, the aromatic carbonization promotion of catechol, combined with the physical barrier effect of the porous skeleton, synergistically improved the flame retardancy and thermal insulation performance of PAN@HA-aer and PAN@HA@PCA-aer. Combustion tests showed that compared with PAN-aer, the total heat release (THR), peak heat release rate (PHRR), smoke production rate (SPR), and the generation of toxic gas HCN of PAN@HA-aer and PAN@HA@PCA-aer were all significantly reduced. Moreover, the limiting oxygen index (LOI) was increased to over 46%, demonstrating excellent flame-retardant and smoke-suppressant properties. This work not only developed eco-friendly flame-retardant porous materials, but also provided a promising strategy for high-value recycling and resource utilization of waste PAN fiber.

Triggered by heightened public safety concerns and the imperative of sustainable chemistry, an urgent demand has emerged for the development of eco-friendly and durable flame retardant Lyocell fibers. However, reconciling high flame retardancy, washing durability, mechanical strength, and formaldehyde-free processing within an environmentally benign and feasible approach remains a significant challenge. To address the issue, a novel co-coordination system of biomass tea polyphenols, L-lysine and Fe3+, cooperating with covalent linking of 3-epoxypropyl trimethoxysilane was constructed. Compared with Lyocell fabric, the treated Lyocell fabric exhibited substantial reductions of 70.35 % for total heat release (THR) and 61.82 % for peak heat release rate (PHRR), alongside a limiting oxygen index (LOI) value of 26.8 % even after 50 laundering cycles. Meanwhile, the modified fabric had excellent UV resistance, antibacterial and hydrophobic properties. Encouragingly, the proposed modification process basically retained the high mechanical properties of the Lyocell fabrics, providing a sustainable, green route toward multifunctional, durable Lyocell textiles for protective and technical apparel applications.

The inherent flammability and insufficient ultraviolet (UV) protection of regenerated cellulose fibers limit their functional applications. Inspired by the natural polyphenol-polysaccharide synergy in plants, a lignin-derived boron-containing phenolic network (Lig-BPF) was incorporated into a cellulose spinning system and then coordinated with Zn2+ to fabricate Cellulose/Lig-BPF@Zn fibers. Compared with pristine cellulose fibers, Cellulose/Lig-BPF@Zn increased the char residue at 800 °C from 13.72% to 30.35% under N2 atmosphere, and reduced the peak heat release rate by 43.03%. The limiting oxygen index increased from 17.2% to 31.5%, and still remained 29.1% after 20 laundering cycles. TG-FTIR analysis showed an 88.56% reduction in total volatile release intensity, while Raman analysis confirmed an increased degree of graphitization, as evidenced by a decreased ID/IG value from 3.59 to 2.55. Furthermore, the UV protection factor increased from 11.42 to 128.82, and remained 109.74 after durability testing. Mechanistic analyses demonstrate that lignin-derived aromatic domains, boron-containing structures and Zn-coordinated species regulate cellulose pyrolysis and promote the char formation. This work develops a sustainable strategy for converting natural lignin into a bio-based flame retardant that simultaneously improves the flame retardancy and UV protection performance of regenerated cellulose fibers, providing a phosphorus-free and eco-friendly approach for preparing multifunctional carbohydrate-based fibers.

To mitigate ecological pollution and fossil-resource depletion caused by traditional petroleum-based materials, biomass-derived functional materials have emerged as promising sustainable alternatives. Herein, a fully biomass-derived phenolic resin (TA-PPF) was developed from renewable feedstocks, which integrated intrinsic flame retardancy, robust adhesion, and value-added reuse capability. TA-PPF exhibited an exceptionally high limiting oxygen index (LOI) of 64.5% and maintained its structural integrity without macroscopic collapse after continuous exposure to a butane flame for 240 s, outperforming many previously reported bio-based and petrochemical flame-retardant materials. Additionally, TA-PPF exhibited robust adhesion to diverse substrates, achieving an adhesion strength of 3.65 MPa on wood and retaining favorable environmental stability in organic solvents, acidic and alkaline media, and under extreme temperatures. Benefiting from its intrinsic flame retardancy and adhesion capability, TA-PPF was further applied as an eco-friendly fire-safety coating for wood, increasing its LOI from 22.3% to 45.4%. Furthermore, inspired by the natural synergy between polyphenols and carbohydrates in plants, waste TA-PPF was repurposed as a functional additive for regenerated cellulose fibers, producing multifunctional composite fibers with excellent flame retardancy and ultraviolet protection, as evidenced by an LOI of 33.5% and an ultraviolet protection factor (UPF) of 136.63. This work provides a sustainable strategy for developing high-performance bio-based resins, fire-safety coatings, and multifunctional regenerated cellulose fibers.

Polyester/cotton (T/C) fabrics suffered the "scaffolding effect" while burning, thus, it is difficult to be flame-retardant with the coming issues of flame retardants overuse. In this work, we envisioned a fully encapsulated coating. The recyclable and flame-retardant PCS was prepared by modifying and dissolving chitosan (CS) with H3PO3, and flame-retardant samples were prepared through dip-coating methods. Scanning Electron Microscope (SEM) results demonstrated that PCS formed a fully-encapsulated film on the surface of T/C, and the coating became more distinct with increasing weight gain. T/C-PCS4 achieved self-extinguishing in the vertical burning test (VFT) along with the formation of a dense and complete char layer, with the limiting oxygen index (LOI) value increased to 27.3%. Compared with T/C, the peak heat release rate of T/C-PCS4 decreased by 20%, accompanied by an increase in char residue content. SEM images of the char residues from the cone calorimeter test showed that its fiber structure remained intact. Combining with the analysis of char residues and gaseous productions indicated that the flame-retardant coating could form a char layer on the T/C surface and simultaneously promote char formation of T/C. In addition, T/C-PCS4 exhibited an antibacterial rate of up to 99.99% against E. coli and S. aureus. Moreover, recyclable PCS improved the flammability of Lyocell and polyester fabrics.

Cellulose aerogels are widely regarded as an ideal thermal insulation material. However, the production equipment of aerogels, such as supercritical dryers or lyophilisers, requires extreme operating conditions. The present study has developed a novel method that combines thermally induced phase separation with heterogeneous ice nucleation to prepare cellulose aerogels via an ambient drying process. This methodology can be applied to a variety of manufacturing technologies in order to produce fibers (1D), films (2D) and complex structures (3D). The resulting cellulose aerogels fibers exhibit an excellent tensile strength of 25.63 MPa, a high porosity of 91.2%, and a strain value of 81.9%. This represents a substantial enhancement over conventional cellulose aerogel fibers (approximately 2%). It demonstrated that the thermal insulation performance remained stable even after the material was subjected to washing and dyeing processes. This preparation strategy offers a plethora of possibilities for the development of multifunctional cellulose aerogel fibers, cellulose aerogel films, and three-dimensional cellulose aerogel structures.

To improve the flame retardancy of lyocell fabrics, in this paper, an eco-friendly flame retardant and antibacterial lyocell fabric (FR@Si-lyocell) was fabricated by surface grafting modification. The surface morphology, combustion properties and antibacterial rate of FR@Si-lyocell were investigated. FR@Si-lyocell exhibited excellent char-forming ability with residual char of up to 40.24 wt% and 11.78 wt% at 800oC in N2 and air, respectively. Its limiting oxygen index (LOI) value increased from 17.6% to 32.3%, and the peak heat release rate (PHRR) and total heat release (THR) decreased significantly by 94.4% and 74.5% compared to the control sample. The synergistic flame retardant mechanism of gas and condensed phases was proposed by analyzing the volatile pyrolysis products and char residue generated during the combustion process. In addition, FR@Si-lyocell showed excellent antibacterial properties, with inhibition efficiencies as high as 99.9% and 99.7% against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). This work provided an efficient and eco-friendly method to prepare multifunctional lyocell fabrics with potential application fields.

Sustainability limitations, inherent flammability, and poor adhesion durability of conventional petroleum-derived resins have given rise to a great demand for renewable bio-based materials with integrated fire safety and interfacial robustness.

In recent years, mussel-inspired polydopamine (PDA) coatings have exhibited great potential for preparing multifunctional materials. However, dopamine (DA) and its derivatives are expensive and difficult to store, which restricts their wide application. Herein, we replaced DA with low-cost and widely sourced tannins (TA) and L-Cysteine to coat polyamide 66 (PA66) fabrics, which was then chleated with Fe3+ and reacted with 1dodecanethiol (DT) to obtain flame retardant, superhydrophobic and UV resistant PA66 fabrics (PA66@OTAA@Fe@DT). The results showed that the peak heat release rate (pHRR), total heat release (THR) and total smoke production (TSP) of PA66@OTAA@Fe@DT were reduced by 55.2 %, 63.3 % and 57.1 % compared to the control sample, respectively. The limiting oxygen index (LOI) increased from 20.5 % of the control sample to 29.5 % and received UL-94 V-0 rating. Furthermore, PA66@OTAA@Fe@DT also exhibited superhydrophobicity with a water contact angle (CA) of 151.9 degrees and excellent ultraviolet rays (UV) resistance with a UV protection factor (UPF) of 172.48. In this work, a green flame retardant and multifunctional PA66 fabric was constructed by tannin/amino acids co-deposition process under mild conditions, providing an eco-friendly and broad applicable strategy for multifunctional modification of polyamide fabrics.

Waterborne polyurethane (WPU) is a highly flammable polymer that is unsuitable for use in fire-prone environments. To address this limitation, an innovative biomass-derived intrinsic flame retardant containing phosphorus, nitrogen, and silicon (hereafter referred to as DETS) was synthesized via a one-pot reaction involving 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, protocatechualdehyde, and diethyl phosphite. Because its molecular structure includes four terminal hydroxyl groups, DETS enables covalent cross-linking with WPU during curing to construct an internally cross-linked network. The resulting WPU/DETS composites exhibited outstanding flame retardancy. Notably, the limiting oxygen index increased up to 27.7%, and vertical burning tests demonstrated self-extinguishing behavior. Cone calorimetry tests revealed reductions of 46.6% and 57.1% in peak heat release rate and smoke production rate, respectively. Furthermore, thermogravimetric analyses confirmed enhanced char yield, and TG-IR analyses showed suppressed emission of toxic volatiles. The tensile strength and elongation at break of WPU/DETS-5 were significantly improved relative to pristine WPU. The study provides a promising strategy for developing sustainable and intrinsically flame-retardant WPU materials based on renewable chemistry.

A facile in situ grafting strategy was elaborately designed to fabricate flame-retardant lyocell fabrics. Acrylamide first immobilized to the surface of lyocell fabrics via an additional reaction between carbon-carbon double bonds and oxygen-free radicals derived from the activated cellulose chain. Diphenylphosphinyl chloride was grafted through the intermediate bridge acrylamide. The combination of acrylamide and diphenylphosphinyl chloride significantly retarded the heat release rate and total heat release and efficiently promoted the formation of rigid and swollen carbonaceous structures. The obtained fire-resistant lyocell fabrics (C-g-AD) with an LOI value (30.6 %) were immediately extinguished after exposed flame for more than 30 s with only 48 mm char length. Besides, the thermal degradation rate of C-g-AD sharply decreased by 17.1 % and 14.7 % in nitrogen and air, respectively. Herein, C-g-AD fabricated by the present strategy exhibited outstanding flame retardancy.

With the depletion of petrochemical resources and the escalating severity of white pollution, replacing petrochemical resources with bio-based resources aligns with sustainable development strategy. In this work, a novel biomass flame retardant (PCDAC) derived from curcumin was intercalated into expandable graphite (EG) to construct an intrinsically intumescent flame retardant system (EG@PCDAC), which was then melt blended with polylactic acid (PLA) to fabricate flame retardant, anti-dripping and smoke suppressive PLA composite (PLA/ EG@PCDAC). The residual char of PLA/EG@PCDAC was 14.27 wt% under N2 atmosphere, while reaching UL-94 V-0 rating. Furthermore, the peak heat release rate and total heat release of PLA/EG@PCDAC were reduced by 46.95 % and 19.02 % compared with original PLA, and the total smoke production and peak smoke production rate also decreased by 20.74 % and 72.09 %, respectively. This work offered green and feasible inspiration for exploring biomass flame retardants and renewable PLA-based functional materials.

A biomass-based finishing agent (ArCP) rich in nitrogen and phosphorus was synthesized from glucose, arginine and phosphorous acid, which was then used for lyocell fabrics to prepare flame retardant, antibacterial and UV resistant properties lyocell fabrics (ArCP-lyocell). The elemental composition, surface morphology, combustion performance, antibacterial and UV resistant properties for the lyocell fabrics before and after modification were investigated. ArCP-lyocell fabrics showed excellent self-extinguishing properties with a limiting oxygen index (LOI) of 35.1 % and maintained an LOI of 30.7 % even after 30 laundering cycles (LCs). Antibacterial experiments confirmed the antibacterial effect of ArCP-lyocell against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), with 99.9 % and 92.8 % inhibition rates, respectively. In addition, the modified fabrics exhibited excellent UV resistant properties with a UV production factor (UPF) of up to 184.54, and lower transmittance both UVA and UVB rays under 2 %. This study provides a simple and efficient approach for developing ecofriendly multifunctional textiles.

Polyamide 66 (PA66) fabric has attracted significant attention due to its excellent overall performance. However, its flammability and melt droplet defects severely restricted its wide application. In this work, we successfully developed a bio-based multifunctional intumescent flame retardant (MIFR) coating for PA66 fabric via the interactions between quaternary chitosan (QC), tannins (TA), 9,10-Dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) and 4-Formylphenylboronic acid (4-FB). The results indicated that the coated polyamide 66 (PA66) fabric (P-PA66@TA@QC) achieved a limiting oxygen index (LOI) of 30.1 % and no molten droplets generated during the combustion. Additionally, the peak heat release rate (pHRR) and total heat release rate (THR) of P-PA66@TA@QC were reduced by 50.3 % and 55.7 %, while the total smoke production (TSP) was decreased by 80 % compared to the control sample, exhibiting a lower fire risk and excellent smoke suppression performances. Furthermore, P-PA66@TA@QC exhibited good hydrophilicity, high UV protection factor (UPF > 180), and high inhibition rate against E. coli (> 99.9 %) and S. aureus (> 99.9 %), indicating outstanding UV resistance and excellent antibacterial properties. This study successfully developed a bio-based multifunctional flame retardant coating, providing significant guidance for preparing eco-friendly and multifunctional PA66 fabrics.

Traditional epoxy resins are manufactured from non-renewable fossil resources and suffer from several drawbacks, including poor flame retardancy, non-reprocessability and recycling difficulties, greatly affecting their wider applications. To address these issues, an inherent flame-retardant epoxy resin (L-Trp@PA/TPEP) was synthesized from biomass tea polyphenols, L-tryptophan, phytic acid and epichlorohydrin. L-Trp@PA/TPEP achieved a limiting oxygen index (LOI) value of 36.4%, with excellent anti-dripping, self-healing and reprocessability. Additionally, due to the limited number of reprocessable cycles, a versatile durable Lyocell fabric (L-Trp@PA/TPEP/Lyocell) was fabricated by finishing with the recycling of non-reprocessable L-Trp@PA/TPEP. L-Trp@PA/TPEP/Lyocell showed an LOI value of 34.5% and ultraviolet protection factor of 137.29. The elongation at break and tensile strength of modified Lyocell fabric increased by 19.2% and 33.6%. In addition, the modified fabric had favorable chemical resistance without mechanical deterioration within the pH range of 1 to 13. Besides, L-Trp@PA/TPEP/Lyocell displayed remarkable anti-fouling and self-cleaning capabilities. This work proposed a comprehensive and eco-friendly approach in terms of raw materials, application and recycling, which was significant for the development of sustainable novel materials and multifunctional textiles.

Addressing the dual challenges of diminishing fossil reserves and proliferating plastic waste accumulation, harnessing renewable cellulose resources offers a promising solution. Guided by the principles of intumescent flame retardant system, the eco-friendly hyperbranched phosphonitrile networks integrating acid, carbon and gas sources was prepared and covalently anchored onto Lyocell fabrics. Further, the hyperbranched phosphonitrile networks induced the interfacial assembly of zirconium phosphate (ZrP) to construct flame retardant Lyocell fabrics (Lyocell-TCHNs@ZrP) with low-temperature multiphase catalytic carbonization and hightemperature physical shielding effects. The char residue of Lyocell-TCHNs@ZrP under N2 atmosphere was increased from 13.63 % of original sample to 39.12 % at 800 degrees C, while the thermo-oxidative behavior was also suppressed in air conditions. Meanwhile, the peak heat release rate (PHRR) and total heat release (THR) of Lyocell-TCHNs@ZrP were reduced by 66.10 % and 80.90 %, which showed great self-extinguishing ability in combustion test. In addition, the tensile strength of Lyocell-TCHNs@ZrP was slightly improved, while the hand feel and whiteness were well remained. This work provided fundamental insights into the molecular design of hyperbranched intumescent flame retardants and the synergistic interaction between solid catalysts, along with an effective strategy for the fire safety performance of cellulose derived textiles.

Epoxy resins (EP) with excellent mechanical properties, adhesive properties and heat resistance are favored in high-end fields. In this study, a silicone-containing phosphoramidite (DPATS) was synthesized through the nucleophilic substitution between diphenylphosphine chloride (DPPC) and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (PATS). DPATS markedly improved the flame retardancy of EP due to the synergy of phosphorous, nitrogen and silicon elements. The results demonstrated that, with only 2 wt% of DPATS, the EP/DDM/ DPATS-2 sample achieved a UL-94 V-0 classification along with a limiting oxygen index (LOI) of 31.4 %. Meanwhile, the peak heat release rate (PHRR) and total heat release (THR) of EP/DDM/DPATS-2 sample reduced by 16.4 % and 8.7 % when compared to virgin EP. The possible flame-retardant mechanism of DPATS on EP during combustion was studied. It was determined that the primary mechanism responsible for the flameretardant behavior of DPATS may be achieved by the promoting char-formation effect from P and Si elements in the condensed phase, and quenching effect from P-containing radicals as well as the dilution effect of Ncontaining gases in the gas phase. Additionally, the flexible silicon-oxygen (Si-O) chain segments from DPATS contributed to the toughness of EP. Compared with neat EP, those containing 2 wt% DPATS showed an increment in tensile strength by 23.8 % and elongation at break by 21.9 %. Moreover, high transparency was maintained thanks to excellent compatibility between DPATS and EP. Hence, our work provides an effective approach for producing flame-retardant EP that is simultaneously tough and transparent.