Limiting Oxygen Index Research Articles

Thiazole-based flame retardant for polyamide vs. a sulfur-free flame retardant with similar phosphorus and nitrogen content

Polyamides are a promising candidate for the research of sulfur-containing flame retardants (FR). A new material based on 2-aminothiazole and 2-methyl-1,2-oxaphospholane-5-on-2-oxide is prepared and introduced into polyamide 12. To understand the effect of sulfur incorporation in its molecular structure, the new flame retardant is compared to a sulfur-free counterpart, revealing distinct variations in their self-extinguishing characteristics. The higher concentration of heteroatoms results in more flame diluting volatiles in the gas phase during thermal decomposition. The addition of the novel flame retardant containing phosphorus, nitrogen and sulfur, named TP, with only 5 m% into polyamide results in a UL-94 V-0 rating. Simultaneously, the limiting oxygen index increased to 31 %, compared to neat polyamide 12 with 24 %. Remarkably, the moisture absorption remains the same with the thiazole-based FR and the mechanical properties are only slightly decreased. This research reveals the flame retardant capabilities and advantages of a thiazole-based phosphorus compounds in polyamide.

Intrinsically Flame‐Retardant Polyamide 6 by Anionic Ring‐Opening Copolymerization with a Phosphorous‐Containing Comonomer

AbstractA three‐step synthetic route is established for the synthesis of a phosphorus‐containing ε‐caprolactam derivative, starting from cyclohex‐2‐enone and diphenylphosphinous chloride, followed by a Beckmann rearrangement. 2D NMR spectroscopy reveals that the phosphorus moiety is selectively localized at the 4‐position of the caprolactam ring. Different amounts of the phosphorus‐containing comonomer are systematically incorporated into polyamide 6 by anionic ring‐opening copolymerization with ε‐caprolactam at elevated temperatures. Polymerization reactions are initiated by a latent, CO2 protected N‐heterocyclic carbene in the presence of N‐acetyl caprolactam and MgCl2. The phosphorus content is determined by inductively‐coupled plasma‐optical emission spectroscopy (ICP‐OES) analysis. Limiting oxygen indices up to 23.5 are found for polymers containing ≈1 wt.‐% of phosphorus. The thermal properties of the copolymers are determined and compared to those of polyamide 6.

CoFe Oxides-Coated 2D Black Phosphorus for Flame-Retardant Nanocoatings with Tunable Mechanical Strength and Efficient Elimination of Toxic Gases.

2D black phosphorus (BP) degrades irreversibly into phosphate compounds under ambient conditions, which limits its application in a variety of fields. In this study, by coating amorphous ferric-cobalt oxides (CoFeO)on BP nanosheets, a multifunctional CoFeO@2D BP is successfully developed that effectively inhibited combustion and catalyzed CO oxidation to eliminate toxic gases. Strong affinity between transition-metal cations and BP allowed the uniform growth of amorphous ferric‒cobalt oxides on the BP surface, which effectively prevented the spontaneous degradation of 2D BP. By combining CoFeO@2D BP with gelatin and kosmotropic salts, the as-obtained nanocoatings are used for surface treatment of flammable polyurethane foam (PU). Kosmotropic ions induced strong hydrophobic interactions and bundling within the gelatin chains which significantly enhanced the mechanical performance of the PU. BP accelerates the carbonization of gelatin to inhibit the combustion of PU, and CoFe oxides, which act as true active centers to accelerate the oxidation of CO, effectively inhibiting the production of harmful gas. The release rate of CO decreases by 73% and the limiting oxygen index (LOI) increases from 17% to ≈32% during PU combustion. The developed novel 2D material opens the way for multifunctional coatings with integrated durability, flame retardancy, and high smoke suppression efficiency.

Construction of a hydrophobicity, phosphorus‐ and nitrogen‐containing layered double hydroxides‐based synergistic effect flame retardant for poly (lactic acid)

AbstractIn this work, a synergistic effect strategy was explored for fabricating hydrophobicity, phosphorus‐ and nitrogen‐containing layered double hydroxides nanosheets (LDHs) based flame retardant (LDHs‐K@DM). This fabricating process was achieved by amination of the surface of LDHs and, subsequently, interfacial self‐assembly with high P content of diethylenetriaminpenta (methylene‐phosphonic acid) (DTPMP) and high N content of melamine (MEL). The chemical construction and thermal stabilization properties of LDHs‐K@DM were confirmed via different characterization approaches. The results revealed that LDHs‐K@DM was successfully prepared and the surface of LDHs‐K@DM was transformed into hydrophobicity with high water contact angle. Moreover, LDHs‐K@DM had better thermal stability. After that, LDHs‐K@DM was molten compounded with biobased polylactic acid (PLA). It was suggested that LDHs‐K@DM were uniformly dispersed in the PLA matrix and could accelerate the decomposition of PLA to form char residues. Most importantly, the addition of 20 wt% LDHs‐K@DM into PLA can endow the composite to achieve a desirable UL‐94 V‐0 rating and the limiting oxygen index value of 30.9%. Finally, the synergistic effect flame retardant mechanism of LDHs‐K@DM was comprehensively analyzed. This synergistic decorating strategy for preparing LDHs‐K@DM flame retardant is promising for industrial production.

A P/Si-containing flame retardant towards simultaneous improvement of the toughness, transparency and fire safety of polycarbonate

Polycarbonate (PC) is a commonly used engineering plastic, but its poor flame retardancy limits its use. In this study, a DOPO-based flame-retardant (DOPO-TMTA) containing P and Si elements was synthesized via a simple method involving 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 2, 4, 6-trivinyl-2, 4, 6-trimethylcyclotrisiloxane (TMTA). The PC/mDOPO-TMTA (m = 4, 6, 8) composites were prepared by melt blending PC with different loadings of DOPO-TMTA. The prepared PC/DOPO-TMTA composites had excellent flame retardancy while maintaining good transparency. The limiting oxygen index (LOI) of PC/8DOPO-TMTA reached 32.5 % and achieved a UL-94 V-0 rating. Moreover, cone calorimetry tests revealed that, compared with those of pure PC, the peak heat release rate (PHRR) and total heat release (THR) of PC/8DOPO-TMTA decreased by 39.0 % and 38.1 %, respectively. Compared with pure PC, PC/mDOPO-TMTA also maintained good mechanical properties, and the tensile and impact strengths were slightly improved. The synergistic flame retardancy of DOPO-TMTA on P/Si elements for the PC matrix was revealed by condensed phase and gas phase product analysis. This work provides a good reference for the preparation of PC composites with high transparency and excellent comprehensive properties.

Preparation of high transparency, thermal stability, flame retardant polymethyl methacrylate nanocomposite via gamma-radiation polymerization

Achieving flame retardancy and thermal stability in poly(methyl methacrylate) (PMMA) while maintaining its inherent high transparency presents a significant challenge. In this work, we successfully fabricated an exceptional composite (P-SiO2-PMMA) with high transparency, flame retardancy, and thermal stability using 60Co γ-ray irradiation-induced copolymerization of methyl methacrylate (MMA), 2-hydroxyethyl 2-methyl-2-propenoate phosphate (HEMAP), and nano-silica (SiO2). The impact of the HEMAP on the crystal, optical, thermal stability, and combustion behavior properties of P-SiO2-PMMA has been investigated. P-SiO2/PMMA forms a three-dimensional network cross-linked molecular chain structure, enhancing the thermal decomposition temperature (Tdi), maximum thermal decomposition temperature (Tmax), glass transition temperature (Tg), and reducing the coefficient of thermal expansion (CTE). HEMAP and SiO2 significantly enhance the flame retardancy of the material. The limiting oxygen index (LOI) value of transparent flame-retardant 20-P-SiO2/PMMA composite material increased from 17.5% for PMMA to 23.2%, with a 47.3% decrease in peak heat release rate (PHRR). The flame retardant mechanism was also investigated. This study offers a novel approach for the industrial application of high transparency, thermal stability, and halogen-free flame-retardant PMMA composite.

Bio-derived epoxy thermosets incorporating imine linkages: Towards sustainable and advanced polymer materials

In the search for sustainable and eco-friendly alternatives, Schiff-based epoxy thermosets are emerging as a promising strategy due to the inherent dynamic and reversible nature of their imine functional groups, which enables thermal reprocessability and chemical recyclability. This article explores the synthesis of Schiff-based epoxy thermosets using sustainable approaches. Starting from vanillin or syringaldehyde, the synthesis involves the incorporation of imine linkages into the epoxy network. A new strategy has been employed by self-polymerization without the use of additional curing agents. This approach conducts to novel thermosets with superior material properties that exceed those reported in previous studies. Thermo-mechanical investigations showed that the designed thermosets have high mechanical properties, with storage moduli at room temperature ranging between 1.5–2.2 GPa, and glass transition values between 138 and 249 °C. Thermal analyses allowed to evaluate the Limit Oxygen Index (LOI) which ranged from 33 % to 36 %, demonstrating excellent flame-retardant properties without the addition of supplementary additives. Their reduced density (0.74–1.09 g/cm3) makes them suitable for applications where weight considerations are critical. These results obtained results place the designed Schiff-based materials as promising candidates for a wide range of high-end applications, particularly in industries that prioritize eco-friendly processes and materials.

Functionalized LDH via intercalation of gluconate anion and surface assembly of ultrafine copper hydroxide for improving mechanical properties and the fire safety of epoxy resin

To impart epoxy resin (EP) with outstanding mechanical properties and fire safety, LDH was systematically functionalized through gluconate anion (GA) intercalation followed by surface assembly of ultrafine Cu(OH)2, resulting in the LDH-GA@Cu(OH)2 hybrid. Comprehensive characterizations confirmed the successful synthesis of the desired product, with a uniform distribution of ultrafine Cu(OH)2 nanoparticles on the GA-intercalated LDH surface. The findings revealed that LDH-GA@Cu(OH)2 improved the mechanical properties of EP due to the increased LDH layer spacing, facilitating EP chain insertion, and the hydrogen bonding between the –OH of GA and the EP matrix. Fire retardancy tests indicated that the EP composite containing 7.5 wt% LDH-GA@Cu(OH)2 achieved a limiting oxygen index (LOI) of 30.1%. Furthermore, compared to pure EP, the composite demonstrated significant reductions in the peak heat release rate (PHRR) and peak CO production rate (PCOP) by 47.4% and 60.5%, respectively, underscoring its superior flame-retardant and toxic smoke suppression capabilities. Mechanistic studies further indicated that ultrafine Cu(OH)2 enhanced char formation through catalytic charring at the interface, which promoted compact and cohesive char layers. Overall, this work proposes a promising functionalization strategy for LDH to endow EP with excellent comprehensive performance.

A multifunctional epoxy composites based on cellulose nanofiber/carbon nanotube aerogels: Simultaneously enhancing fire-safety, thermal conductive and photothermal performance

As 5G technology develops and electronic power density increases, preparing epoxy resin (EP) composites with excellent fire-safety, thermostability, and thermal conductivity remains challenging. Herein, hexaphenoxy cyclotriphosphazene and poly(piperazine methylphosphonic acid pentaerythritol ester) were used as synergistic flame retardants (FR) for EP. The cellulose nanofiber/carboxylated multiwalled carbon nanotubes aerogels (CCA80) were prepared and immersed into the EP and FR mixture to obtain EP/CCA80/FR composites. Compared with neat EP, the limiting oxygen index of EP/CCA80/6 wt% FR increased by 38.9 %, the total heat release and CO2 production rate decreased by 30.61 % and 39.47 %, respectively, achieving the UL-94 V-0 rating. Moreover, its thermal conductivity was 1.06 W · m−1·K−1, 457.9 % higher than neat EP, while maintaining excellent electrical insulation. Its surface temperature maintained at 94.5 °C under 1.0 kW·m−2 irradiation for 2 h, exhibiting good photothermal conversion capability and photobleaching resistance. A novel fabrication methodology of multifunctional EP composites for high-performance electronic component was proposed.

Multi‐component coupling synergistic effect of resourced gold tailings on intumescent flame‐retardant polypropylene

AbstractAddressing the challenge of resource utilization of gold tailings. A high performance flame‐retardant fillers (K‐GTF) were prepared from gold tailings (GTF) by coupling and condensation for application to intumescent flame‐retardant polypropylene (PP). K‐GTF enhances the flame‐retardant, thermal stability, smoke suppression and mechanical properties of flame‐retardant PP through synergistic approach. The results show that K‐GTF demonstrates good flame‐retardant synergism, with PP composites containing 3% additive (PP/G3) exhibiting substantial flame‐retardant and smoke suppression characteristics. Notably, PP/G3 boasts a limiting oxygen index (LOI) of 36.1%, which is substantially higher than the 33.6% LOI of the flame‐retardant PP without added K‐GTF (PP/G0). Furthermore, the peak heat release rate (PHRR), peak smoke production rate (PSPR), total heat release rate (THR), and total smoke production (TSP) of PP/G3 were decreased by 32.5%, 26.9%, 31.6%, and 21.5%, respectively, as compared to PP/G0. According to the synergistic mechanism analysis, K‐GTF exerts a multi‐component coupling synergistic effect, which promotes the production of phosphorus‐rich cross‐linking structures in flame‐retardant PP materials during the combustion, thereby promotes the formation of stable, dense and intumescent char to further enhances the flame‐retardant performance of the PP materials. In terms of mechanical effects, the introduction of K‐GTF alleviates the issue of a substantial decline in mechanical properties typically caused by flame retardants in PP materials. This indicates that K‐GTF improves the compatibility between the flame retardants and the PP matrix, thereby enhancing the mechanical properties of the flame‐retardant PP materials.Highlights Successfully synthesis a flame‐retardant synergist (K‐GTF). K‐GTF has good synergistic flame‐retardant effect. K‐GTF substantially enhances char formation and thermal stability of flame‐retardant PP. K‐GTF exerts a multi‐component coupling synergistic effect. K‐GTF enhances the compatibility between the PP matrix and the flame retardants.

Facile Construction of Flame-Resistant and Thermal-Insulating Sodium Alginate Aerogel Incorporating N- and P-Elements.

In this study, sodium alginate (SA) aerogel cross-linked with Ca2+ was selected as the basic skeleton to construct a lightweight, flame retardant, and thermal insulating composite aerogel via modification with melamine and phytic acid. The resulting aerogel, SA-1.0 MP, achieved a thermal conductivity as low as 0.0379 W/(m·K). Compared to pristine SA aerogel, SA-1.0 MP demonstrated improved fire resistance, evidenced by a substantial increase in the limiting oxygen index (LOI) from 21.5% to 48.8% and a V-0 rating in the UL-94 test. Furthermore, a synergistic mechanism was proposed to explain its remarkable flame-retardant capability.

Synchronously enhanced flame retardancy and mechanical properties of polylactic acid via in-situ assembly of polyphosphazene nanoparticles on ammonium polyphosphate

Polylactic acid (PLA) exhibits wide potential applications in many fields ranging from textile, packaging material to biomedical devices. However, the relatively low mechanical properties and inflammability are obstacles to the expansion of its application. Here, a kind of polyphosphazene nanoparticles with tannic acid (TA) as template, hexachlorocyclotriphosphazene (HCCP) and 4,4′-Sulfonyldiphenol (BPS) as comonomers were prepared (named as HTB), and then combined with ammonium polyphosphate (APP) to enhance the comprehensive properties of PLA composites. The introduction of HTB strengthened the interfacial adhesion of composites via constructing the hydrogen bond interaction between PLA and APP, promoting the homogenous dispersion of APP in the composite and the formation of APP network. The flame retardant measurements presented that incorporating 10 wt% APP and 5 wt% HTB in PLA increased the limit oxygen index (LOI) value to 31.0% and endowed the composite with the V-0 rating of UL-94 test and simultaneously, the peak of heat release rate (PHRR) and total heat release (THR) of the composite decreased by 14.2% and 13.2% compared with pure PLA. Specially, there was almost no melt drip appeared during the combustion process, which was distinctly different from the combustion behavior of the composite containing only 20 wt% APP with the V-2 rating of UL-94 test. The uniform dispersion of APP in the PLA matrix and the strong interfacial adhesion between APP and the PLA matrix contribute to the enhancement of the mechanical properties of composites, and the elongation at break, Young’s modulus and impact strength of the composite were increased by 52.9%, 7.6% and 24.2%, respectively. The present study offers novel insights for the trade-off between flame retardancy and mechanical properties with PLA composites.

Double cross-linked biomass aerogels with enhanced mechanical strength and flame retardancy for construction thermal insulation

Biomass aerogels are expected to be a popular material in construction field due to their sustainability, eco-friendliness and excellent thermal insulation properties. In this paper, high modulus biomass aerogels based on the principle of double cross-linking of physics and chemistry were synthesized by freeze-drying technique using gelatin, sodium carboxymethyl cellulose, glutaraldehyde, phytic acid and diatomite as raw materials. The presence of a double cross-linked network structure endowed the prepared aerogels with a low thermal conductivity (0.021–0.029 W·m−1·k−1). The density of only 0.0865 g·cm−3 biomass aerogel exhibited an extrastrong compression modulus of 31.5 MPa, which was superior to common biomass aerogels. Biomass intumescent flame retardant system composed of sodium carboxymethyl cellulose (carbon source), gelatin (gas source) and phytic acid (acid source) was used in combination with diatomite to enhance flame retardancy (limit oxygen index value up to 36.5 %, UL-94 V-0 rating and total smoke production reduced from 0.31 m2 to 0.18 m2) and thermal stability (the residue up to 48.91 %). Remarkably, the modified aerogel showed incredible hydrophobicity (hydrophobic angle of 137°). In summary, the results indicated this study proposed a novel green idea for the preparation of construction thermal insulation materials with a combination of high modulus, flame retardancy and hydrophobicity.

A New Approach for Improving Flame Retardancy of Automotive Interior Upholstery

This study presents the flame retardant (FR) performance of chemically treated automotive upholstery fabrics using two different impregnation methods of Resin Transfer Molding (RTM) and supercritical carbon dioxide (scCO2). Referring to the related standards, untreated seat fabric obtained from seat upholstery of a bus (neat fabric, NF) and treated fabric samples underwent burning rate (BR) and limiting oxygen index (LOI) tests to compare effect of treatment and impregnation methods on FR performance. Thermal analysis was also conducted on the samples considering onset degradation temperatures and char yields. The results showed that BR and LOI of all samples were in acceptable range and treatment provided enhancement in FR performance of NF. The treated sample using scCO2 method gave the highest LOI value of 32% and the lowest BR of 21 mm/min subtending to 18.5% increase in LOI and 30% reduction in BR compared to those of NF. The performance of treatment in RTM was worse than that of scCO2 and better than that of NF. The results confirm that both treatment and methods used in this study give promising results for safety against fire in transportation vehicles.

Constructing piperazine pyrophosphate@LDH@rGO with hierarchical core-shell structure for improving thermal conductivity, flame retardancy and smoke suppression of epoxy resin thermosets

The integration and miniaturization development of electronic devices placed the great demand for epoxy resin (EP) thermosets with excellent thermal management, flame retardancy and electrical insulation. Herein, a multifunctional additive piperazine pyrophosphate@layered double hydroxide@reduced graphene oxide (PPAP@LDH@rGO) with hierarchical core-shell structure was constructed by solvothermal and electrostatic self-assembly methods to meet the above requirements. Profiting from the distinct structure of PPAP@LDH@rGO, the thermal conductivity of EP/PPAP@LDH@rGO reached 0.951 W m−1 K−1 at 7 wt% addition (3 wt% rGO containing), which is 320.8 % increment compared to pristine EP. Meanwhile, when 4 wt% PPAP@LDH@rGO was added, the EP thermoset reached UL-94 V-0 rating during vertical burning tests with the limiting oxygen index of 29.8 % due to the synergistic effect of PPAP, LDH and rGO. The release of hazard products including smoke and carbon monoxide for EP/PPAP@LDH@rGO visibly declined during combustion. Besides, the EP thermosets also well-maintained the electrical insulation and mechanical properties. This work provided an alternative approach for preparing high performance EP thermosets which was suitable to be applied in electronics and electrical fields.

Synergistic effect of Co-MOF/epoxy modified tannic acid/ammonium polyphosphate on flame retardancy, anti-melt dripping and mechanical properties of polylactic acid

Achieving flame retardancy and anti-dripping properties in polylactic acid (PLA) while preserving its mechanical integrity remains a significant challenge. In this study, a novel organic ligand rich in phosphorus (P) and nitrogen (N) was synthesized and coordinated with Co2+ions to form a cobalt-based metal–organic framework (Co-MOF) with a multilayer mesoporous structure, acting as an effective carbonization agent. This Co-MOF was then compounded with epoxy-modified tannic acid (eTA) and ammonium polyphosphate (APP) to create a synergistic flame-retardant system for PLA (PLA/MAT). The Co-MOF provides numerous active sites for catalytic oxidation, promoting the formation of a uniform, hill-like expanded carbon layer. During pyrolysis, the Co-MOF and APP yield cobalt oxides and polyphosphates, which catalyze the dehydration of PLA and eTA, facilitating carbonization and forming a continuous, dense protective layer. Consequently, the PLA/MAT system exhibits both robust mechanical properties and excellent flame retardancy, as demonstrated by a limiting oxygen index (LOI) of 27.0 % and a UL-94 V-0 rating, with no melt dripping observed during combustion tests. This work offers a novel approach for enhancing the flame retardancy and anti-dripping performance of PLA, with potential applications in engineering, electronics, and the automotive industry.

Schiff base approach to introduce chitosan-phytic acid complex for flame-retardant cotton fabrics

In this study, chitosan was integrated onto cotton fabric fibers through a Schiff base reaction, followed by the in-situ generation of Chitosan-Phytic acid (CH-PA) complex to achieve green flame retardancy. The process began with oxidizing the fabric using sodium periodate (NaIO4) to create numerous aldehyde groups on the fiber surface. Subsequently, CH was grafted onto the fabric via a Schiff base reaction. The fabric was then immersed in a PA solution to form a CH-PA complex, resulting in a novel and highly efficient flame-retardant (FR) fabric. The structure of the treated fabric was analyzed by using Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS), confirming the successful formation of the desired structure. The thermal stability and flame retardancy of the fabric were systematically evaluated using thermogravimetric analysis (TGA), cone calorimetry (CONE), vertical combustion tests, and limiting oxygen index (LOI) measurements. The LOI increased from 17.6 % to 30.6 %, and vertical combustion tests demonstrated self-extinguishing capabilities when the fabric was treated by the NaIO4 solution at concentrations of 0.02 g/mL or higher. In the CONE test, the modified fabric showed significant improvements, with peak heat release rate (pHRR) and total heat release (THR) decreasing by approximately 80 % and 60 %, respectively. Comprehensive analysis indicated that the FR mechanism involved both gas phase and condensed phase actions. Further characterization of the material included tensile testing and wash resistance assessments. By comparing these findings with recent research on similar topics, the advantages and disadvantages of the materials were thoroughly evaluated. Notably, this work provides a robust experimental foundation and conceptual expansion for the green flame retardancy of cotton fabrics.

Improvement of the flame retardancy of polyamide 6 by the incorporation of UiO-66 and UiO-66/melamine

The flame retardancy of polyamide 6 (PA6) has been investigated through the incorporation of the metal–organic framework (MOF) UiO-66 and a composite of UiO-66/melamine during the extrusion process. The prepared materials have been characterised by various techniques: XRD, XPS, FTIR, TGA, DSC, SEM, EDX and mechanical properties. Moreover, to examine the efficiency of the flame retardants, the composites have been tested using the UL-94 vertical and, horizontal burning test, as well as the limiting oxygen index (LOI). The UL-94 V-2 standard has been achieved with only a 4 wt% load of either UiO-66 or UiO-66/melamine, compared to pure polyamide, which is not classified. The best results have been achieved with the UiO-66/melamine sample at 7 wt%, which prevents the agglomeration of UiO-66 alone. The highest LOI value was also obtained with this sample, achieving a value of 35.5 %, compared to pure PA6 and with UiO-66, which reached values of 22.4 % and 23.2 %, respectively. A flame suppression mechanism of the UiO-66/melamine composite is proposed, based on the formation of zirconium oxide, gas adsorption by the MOF and release of NH3.

Aminopropyltriethoxysilane-modified MXene for remarkably enhancing tracking resistance and flame retardancy of silicone rubber

The preparation of silicone rubber with excellent tracking resistance and flame retardancy is of great significance for application in high-voltage electrical insulation. Unfortunately, to date there lacks an effective strategy to simultaneously endow silicone rubber with satisfied tracking resistance and flame retardancy. In this work, aminopropyltriethoxysilane-modified MXene (APTES-MXene) was prepared by dehydrative condensation between the Si-OH in the hydrolyzed aminopropyltriethoxysilane (APTES) and the hydroxyl groups in MXene. The APTES-MXene was homogeneously dispersed in addition-cure liquid silicone rubber (ALSR). The effects of APTES-MXene on the tracking resistance and flame retardancy of ALSR were investigated. Incorporating 0.175 phr APTES-MXene and 15 ppm Pt catalyst enabled ALSR to pass 1A4.5 level, with a low erosion rate of only 0.29 %, indicating a significantly improved tracking resistance. Meanwhile, the 0.175 phr APTES-MXene also endowed ALSR a UL-94 V-0 rating and the limiting oxygen index (LOI) value reached 32.8 %. It was found that APTES-MXene and Pt catalyst synergistically promoted ALSR forming ceramic layer at elevated temperature. The mechanism for APTES-MXene improving the tracking resistance of ALSR was also proposed. This work provided new insights for high performance high-voltage insulation silicone rubber.

Double-crosslinked polyvinyl alcohol/starch bioplastic with superior water-resistance and flame retardancy

The high water solubility and flammability of polyvinyl alcohol (PVA) limits its further widespread use in areas such as bioplastic and green packaging. In this study, double-crosslinked polyvinyl alcohol/starch bioplastics (named PDA) were fabricated using PVA, dialdehyde starch (DAS), and phytic acid (PA), resulting in a material with superior water resistance, flame retardancy, and excellent degradability. PA not only plays the role of catalyst for the chemical crosslinking but also as the physical crosslinker to form the intermolecular hydrogen bonds with PVA and DAS. This chemically and physically double cross-linked network structure results in PDA bioplastics with excellent toughness and water resistance. Specifically, the optimal formulation with 15 % PA content, designated as PDA15, exhibited a high toughness of 35.5 MJ/m3 and demonstrated prolonged shape retention in the boiling water. Additionally, PA also serves as a flame-retardant and antibacterial agent; the PDA15 achieved a high limit oxygen index (LOI) value of 40.0 % and passed the UL-94 V-0 rating without melt dripping, along with better degradability compared to pure PVA film. These outstanding performances make the PDA bioplastics highly promising for various applications, particularly in disposable plastics and laminated flexible packaging materials.