Durable flame-retardant cotton fabrics with tannic acid complexed by various metal ions

Eco-friendly coating fabricated by quaternary chitosan/tannins assembly coupled with DOPO towards fabricating multifunctional PA66 fabrics

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.

Janus cotton with unidirectional-wicking, tri-mold cooling and antibacterial performance for personal thermal-moisture management

Single-mode personal thermal-moisture management fabrics cannot ensure the comfort and safety of the human body in high-temperature, high-humidity, and complex environments. Here, a tri-cooling cotton fabric (TCCF) that combines evaporation, convection, and heat storage with a converging pore array, Janus wetting structure and phase change microcapsule is demonstrated. Benefiting from its Janus wetting structure and converging pore array, the TCCF exhibits excellent unidirectional sweat-wicking performance (717 unidirectional transfer index) and rapid water vapor transmission (223.0 g/m2/h). The TCCF can lower the temperature by 4.5 °C through evaporation and convection compared with conventional cotton. Furthermore, the TCCF demonstrates excellent buffering capacity for sudden temperature changes. Evaporation, convection, and heat storage help cool the human body in complex environments.

A Robust, Biodegradable, and Fire-Retardant Cellulose Nanofibers-Based Structural Material Fabricated from Natural Sargassum

With increasing concern about the environmental pollution of petrochemical plastics, people are constantly exploring environmentally friendly and sustainable alternative materials. Compared with petrochemical materials, cellulose has overwhelming superiority in terms of mechanical properties, thermal properties, cost, and biodegradability. However, the flammability of cellulose hinders its practical application to a certain extent, so improving the fire-retardant properties of cellulose nanofiber-based materials has become a research focus. Here, cellulose nanofiber and alginate are extracted from abundant natural sargassum as high-strength nanoscale building blocks, and then a sargassum cellulose fire-retardant structural material is prepared through a bottom-up hydrogel layer-by-layer method. The structural materials obtained incorporate excellent mechanical properties (≈297 MPa), thermal stability (≈200 °C), low thermal expansion coefficient (≈7.17 × 10-6 K-1), and fire-retardant properties. This work largely improves the utilization of seaweed residue and natural polymers, providing a bio-based fire-retardant strategy, and has a wide range of development prospects in the field of fiber-based high-performance structural materials in the future.

Anti-ultraviolet and semi-durable flame-retardant viscose fabrics fabricated by modified tea polyphenols

Viscose fabrics are characterized as good moisture absorption and dyeability, but the disadvantage of being extremely flammable limits the application of viscose fabrics. In this paper, tea polyphenols (TPs), amino trimethylphosphonic acid (ATMP) and urea were used to synthesize a semi-durable and efficient flame retardant, TBP. The limiting oxygen index (LOI) of Viscose/TBP was 44.2 %, and peak heat release rate was decreased by 91.5 %, indicating the fire risk of viscose fabrics was reduced. Viscose/TBP200-20Ls can pass the vertical flame test after 20 laundering cycles (Ls), and LOI reached 27.0 %. TBP did not cause damage to the mechanical properties of treated viscose fabrics. The transmittance of Viscose/TBP showed a significant reduction compared with those of viscose fabrics in ultraviolet-A and ultraviolet-B region, and its ultraviolet protection factor value reached 86.1 which was better for anti-ultraviolet properties. In a word, Viscose/TBP with anti-ultraviolet properties and flame retardancy was successfully prepared. Meanwhile, flame-retardant viscose fabrics' tensile strength was not decreased.

Sustainable calcium gluconate-based coatings for lyocell fabrics with superior flame retardancy, antibacteria and wearing properties

Sustainability and high performance of flame retardants for lyocell fabrics were still difficult to balance. Here, the full bio-based coatings (PACG) for lyocell fabrics with superior efficient flame-retardant, antibacterial and wearing properties were prepared by phytic acid (PA) and calcium gluconate (CG) in the water solvent. The fire safety of PACG/Lyocell fabrics was remarkably enhanced with an increase in limiting oxygen index (LOI) to 28.7 % when the weight gain was only 4.8 wt%. Meanwhile, PACG/Lyocell fabrics do well work on the heat and smoke release inhibition deriving from the satisfactory synergistic effect of PACG between fast formation of dense residuals and a large release noncombustible gas. Additionally, the existence of calcium ion in the PACG endowed the Lyocell fabrics with excellent antibacterial activity, where the antibacterial properties of Staphylococcus aureus (S. aureus) reached to 99.99 %. Moreover, after 100 dry friction cycles, PACG/Lyocell fabrics still maintained superior flame retardancy and antibacterial properties. More interestingly, unlike other treatment, this efficient and mild treatment method did not deteriorate the whiteness, moisture regain, and wearing properties of lyocell fabrics, which offered a simple and eco-friendly way to obtain the flame-retardant and antibacterial lyocell fabrics with well wearing properties.

Multilevel structural polylactic acid fabrics for flame retardancy, durability, and electromagnetic interference shielding

The integration of polylactic acid (PLA) fabrics with bio-based flame retardants and conductive MXene addresses the requirements for safe sustainable development and electromagnetic interference (EMI) shielding. The dehydration and carbonization of phytic acid (PA) and polyethylenimine (PEI) were facilitated by employing 3-glycidyl oxy propyl trimethoxsilane (GPTMS) as an organic crosslinking agent, which was covalently bonded to both the flame retardants and the MXene conductive layer. The prepared multifunctional PLA fabric, designated as PA-PEI-MXene-60, exhibits a high Limiting Oxygen Index (LOI) of 35.6 %, a damage length of 3.2 cm, a peak heat release rate (pHRR) reduction of 81.38 %, and total heat release (THR) reduction of 27.03 %, indicating exceptional flame-retardant properties. Concurrently, the MXene conductive layer provides outstanding EMI shielding performance. A subsequent hydrophobic treatment was applied using polydimethylsiloxane (PDMS) coatings, resulting in a water contact angle of 148.8°. Additionally, while the PLA fabrics exhibited remarkable EMI shielding effectiveness at 54 dB. Importantly, despite undergoing repeated bending and abrasion tests, these multifunctional PLA fabrics maintain relatively high EMI shielding efficiency, demonstrating commendable durability. This work significantly contributes to the research and development of bio-based, safe, durable multifunctional flame-retardant materials with EMI shielding capabilities.

Developing flame retardant, smoke suppression and self-healing polyvinyl alcohol composites by dynamic reversible cross-linked chitosan-based macromolecule

With the increasing threat of white pollution to the public health and ecosystem, functional materials driven by green and sustainable biological macromolecule are attracting considerable attention. Inspired by the double-helix structure of DNA, a P-B-N ternary synergistic chitosan-based macromolecule (PBCS) was constructed to prepare flame retardant, smoke suppression and self-healing polyvinyl alcohol composite (PVA@PBCS) via dynamic reversible interactions. The limiting oxygen index value of PVA@PBCS increased from 19.6 % to 28.7 %, whereas the peak heat release rate and total heat release decreased by 47.04 % and 43.37 %, respectively. Besides, the peak smoke production rate and total smoke production of PVA@PBCS also decreased by 45.31 % and 54.98 %. With the presence of borate ester-based covalent and multiple hydrogen bonds, the tensile strength and elongation at break of PVA@PBCS increased by 19.50 % and 16.85 % compared to the control sample, and the healing efficiency for tensile strength and elongation at break was as high as 93.86 % and 90.57 %, respectively. This work developed an eco-friendly and effective scenario for fabricating flame retardant and smoke suppression PVA materials, stimulating the substantial potential of chitosan-based biomacromolecule and dynamic reversible cross-linked tactics in self-healing field.

Development of an UV-Resistant Multilayer Film with Enhanced Compatibility between Carboxymethyl Cellulose and Polylactic Acid via Incorporation of Tannin and Ferric Chloride

Carboxymethyl cellulose (CMC) and polylactic acid (PLA) are recognized for their environmental friendliness. By merging them into a composite film, packaging solutions can be designed with good performance. Nonetheless, the inherent interface disparity between CMC and PLA poses a challenge, and there may be layer separation issues. This study introduces a straightforward approach to mitigate this challenge by incorporating tannin acid and ferric chloride in the fabrication of the CMC-PLA. The interlayer compatibility was improved by the in situ formation of a cohesive interface. The resulting CMC/TA-PLA/Fe multilayer film, devoid of any layer separation, exhibits exceptional mechanical strength, with a tensile strength exceeding 70 MPa, a high contact angle of 105°, and superior thermal stability. Furthermore, the CMC/TA-PLA/Fe film demonstrates remarkable efficacy in blocking ultraviolet light, effectively minimizing the discoloration of various wood surfaces exposed to UV aging.

Preparation and application of halogen-free and efficient Si/P/N-containing flame retardants on cotton fabrics

Cotton fabric is extensively utilized due to its numerous applications, but the flammability associated with cotton fabric poses potential security risks to individuals. A halogen-free efficient flame retardant named poly [(tetramethylcyclosiloxyl spirocyclic pentaerythritol)-piperazin phosphate] (PCPNTSi) was developed to consolidate the fire retardance of cotton fabrics. After PCPNTSi treatment, the limiting oxygen index (LOI) of cotton fabric with 30 % weight gain (CP3) was raised to 32.8 %. In the vertical flammability test (VFT), CP3 has self-extinguished performance with a char length of 8.7 cm. The heat release rate (HRR) of cotton fabric with 20 % weight gain (CP2) is 78.8 % lower than that of pure cotton fabric (CP0). In addition, the total smoke release (TSP) of CP2 is 41.7 % lower than that of CP0, indicating PCPNTSi gives cotton fabric a good capability to inhibit smoke release. Finally, the possible flame retardant mechanism was discussed by the data of scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), Fourier Transform infrared spectroscopy (FT-IR) and thermogravimetric infrared spectroscopy (TG-IR). The results show that PCPNTSi is an intumescent flame retardant acting in both gas phase and solid phase.

Electrostatic self-assembly endows cellulose paper with durable efficient flame retardancy and mechanical performance improvement

Flameproof modification of paper can improve safety and application performance. However, traditional paper is prone to moisture absorption, resulting in significant reduction in flame retardant performance, even complete failure, greatly limiting the application environment. In order to achieve long-term flame retardant properties of paper, while avoiding the loss of physical properties caused by the introduction of flame retardants, in this work, a plant acid/phosphate and melamine formaldehyde coating (PyA/PA-MF) is prepared through electrostatic self-assembly for durable flame retardant performance of cellulose paper. Due to the electrostatic interaction, the paper surface become greatly rough with introduction of PyA/PA-MF, a uniform microsphere structure is formed on the surface of the paper cellulose, which effectively fix the phosphorus-containing groups. The oxygen index reaches 33 % and the carbon length was only 6.3 ± 0.2 cm, the pHRR and THR are decreased by 80 % and 73 %, respectively. After being immersed for 72 h, the oxygen index is still 31.4 % and carbon length is no more than 12 cm. mechanical property of modified paper is significant increased in the tensile strength (2.4 MPa) compared to the blank paper (1 MPa), as well as that the whiteness of the surface of the modified paper will not change. In summary, PyA/PA-MF endows paper long-term flame retardant performance while maintaining its basic performance.

Bioinspired phosphorus-free and halogen-free biomass coatings for durable flame retardant modification of regenerated cellulose fibers

Inspired by mussel adhesion and intrinsic flame retardant alginate fibers, a biomass flame retardant (PPCA) containing adhesive catechol and sodium carboxylate structure (-COO-Na+) based on biomass amino acids and protocatechualdehyde was designed to prepare flame retardant Lyocell fibers (Lyocell@PPCA@Na). Furthermore, through the substitution and chelation of metal ions by PPCA in the cellulose molecular chain, flame retardant Lyocell fibers chelating copper and iron ions (Lyocell@PPCA@Cu, Lyocell@PPCA@Fe) were prepared. Compared with the original sample, the peak heat release rate (PHRR) and total heat release (THR) for modified Lyocell fibers were significantly reduced. In addition, the modified sample exhibited a certain flame retardant durability. TG-FTIR analysis showed that the release of flammable gaseous substances was inhibited. The introduction of Schiff bases and aromatic structures in PPCA, as well as the decomposition of carboxylic metal salts were beneficial for the formation of char residue containing metal carbonates and metal oxides to play the condensed phase flame retardant effect. This work develops a new idea for the preparation of eco-friendly flame retardant Lyocell fibers without the traditional flame retardant elements such as P, Cl, and Br.

Bio-based alginate and Si-, P- and N-containing compounds cooperate toward flame-retardant modification of polyester fabrics

Imparting flame retardancy to polyester fabrics is still a pressing issue for the textile industry. To this end, a composite coating was developed by phosphite, pentamethyldisiloxane, urea and sodium alginate, and then applied together with calcium chloride to prepare flame-retardant polyester fabrics. The optimized polyester fabrics named PF-HUSC exhibited a rough surface with P, Si, N and Ca element distributions, as observed by scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDX). Flame retardancy evaluations showed that the damaged length of PF-HUSC with a limiting oxygen index (LOI) value of 35.3 ± 0.3 % was reduced from the contrastive 17.6 ± 0.4 cm to 4.6 ± 0.2 cm after vertical burning test. Thermogravimetric (TG) test confirmed that PF-HUSC retained a char residue as high as 35.1 % at 700 °C. Cone calorimetry test displayed that the total heat release (THR) and total smoke production (TSP) values of PF-HUSC were reduced to 3.1 MJ/m2 and 1.1 m2, respectively, as compared to those of pure polyester fabrics. More importantly, PF-HUSC still exhibited higher LOI value than that of pure polyester fabrics after 25 washing cycles. Hence, the coating scheme is considered as a new method to expand the preparation of flame-retardant polyester fabrics.

Aldehyde-free and bio-based durable coatings for cellulose fabrics with high flame retardancy, antibacteria and well wearing performance

The bio-based coatings of cellulose fabrics (cotton) had attracted increasing attention for multifunction and sustainability but suffered from poor durability and low efficiency. Here, the aldehyde-free and durable coatings for cotton fabrics (CPZ@CF) with satisfactory flame retardancy, antibacteria as well as wearing performance were prepared through the interfacial coordination effect where the well-organized zinc phytate complex were in situ grew on the pre-treated surface of cotton fabrics with chitosan (CS) and Zn2+. The CZP@CF exhibited excellent antibacterial activity for Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) with 99.99 % antibacterial rates benefiting from the synergistic effect between Zn2+ and CS. Meanwhile, even the CPZ coatings loading was only 1.5 wt%, the fire safety of CZP@CF remarkably enhanced owing to the excellent synergistic catalytic charring and free radical capture. More importantly, the antibacterial rates of CZP@CF for S. aureus and E. coli still reached 99.99 % and 91.67 % after 50 washing cycles. Additionally, this treatment method did not deteriorate the fabrics properties, including mechanical and breathability as well as wearing performance, which provided the approach to fabricate the flame retardant and antibacterial textiles with well durability and wearing performance.

Design of P-decorated POSS towards flame-retardant, mechanically-strong, tough and transparent epoxy resins

Epoxy resins (EPs) are known for their durability, strength, and adhesive properties, which make them a versatile and popular material for use in a variety of applications, including chemical anticorrosion, small electronic devices, etc. However, EP is highly flammable due to its chemical nature. In this study, phosphorus-containing organic-inorganic hybrid flame retardant (APOP) was synthesized by introducing 9, 10-dihydro-9-oxa-10‑phosphaphenathrene (DOPO) into cage-like octaminopropyl silsesquioxane (OA-POSS) via Schiff base reaction. The improved flame retardancy of EP was achieved by combining the physical barrier of inorganic Si-O-Si with the flame-retardant capability of phosphaphenanthrene. EP composites containing 3 wt% APOP passed the V-1 rating with a value of LOI of 30.1% and showed an apparent reduction in smoke release. Additionally, the combination of the inorganic structure and the flexible aliphatic segment in the hybrid flame retardant provides EP with molecular reinforcement, while the abundance of amino groups facilitates a good interface compatibility and outstanding transparency. Accordingly, EP containing 3 wt% APOP increased in tensile strength, impact strength, and flexural strength by 66.0 %, 78.6 %, and 32.3 %, respectively. The EP/APOP composites had a bending angle lower than 90°, and their successful transition to a tough material highlights the potential of this innovative combination of the inorganic structure and the flexible aliphatic segment. In addition, the relevant flame-retardant mechanism revealed that the APOP promoted the formation of a hybrid char layer containing P/N/Si for EP and produced phosphorus-containing fragments during combustion, showing flame-retardant effects in both condensed and vapor phases. This research offers innovative solutions for reconciling flame retardancy & mechanical performances and strength & toughness for polymers.

Interfacial engineering to construct P-loaded hollow nanohybrids for flame-retardant and high-performance epoxy resins

Nano flame retardants, as one of the key flame retardants in recent years, have been limited by poor efficiency and weak compatibility. In this study, we propose an interfacial hollow engineering strategy to tackle this problem by assembling P-phytic acid into the hollow cavity of mesoporous SiO₂ grafted with a polydopamine transition metal. In this design, the grafted polydopamine-metal coatings on the hybrids can greatly improve their interface compatibility with the polymer matrix, while the loaded phytic acid in the cavity contributes to enhance flame retardancy. Consequently, the resultant hierarchical P-loaded nanohybrids show both high flame retardancy and mechanical reinforcement for the polymer. Taking epoxy resin (EP, a typical thermosetting resin used in large quantities) as a representative, at only 1 wt% loading of the nanohybrids, the impact strength of the nanocomposites improved by 35.7% compared to pure EP. Remarkably, the hybrids can simultaneously endow EP with high flame retardancy (low heat release rate) and satisfactory smoke inhibition. Additionally, the flame-retardant mechanism analysis confirmed that the nanohybrid had a better catalytic carbonization effect on promoting the highly graphitized carbon layer, thereby suppressing the fire hazard of epoxy resins. This research offers a new interfacial hollow engineering method for the construct and design of high-performance EP with nanohybrids.