The influence of carbon nanotubes on the combustion toxicity of PP/intumescent flame retardant composites

Release and toxicity assessment of carbon nanomaterial reinforced polymers during the use and end-of-life phases: A comparative review

The research on carbon-based nanomaterial (C-NM) composites has increased in the last two decades. This family of functional materials shows outstanding mechanical, thermal and electrical properties, and are being used in a variety of applications. An important challenge remains before C-NM can be fully integrated in our production industries and our lives: to assess the release of debris during production, use, and misuse of composites and the effect they may have on the environment and on human health. During their lifecycle, composites materials can be subjected to a variety of stresses which may release particles from the macroscopic range to the nanoscale. In this review, the release of debris due to abrasion, weathering and combustion as well as their toxicity is evaluated for the three most used C-NM: Carbon Black, Carbon Nanotubes and Graphene-related materials. The goal is to stimulate a Safe-By-Design approach by guiding the selection of carbon nano-fillers for specific applications based of safety and performance.

In vitro data for fire pollutants: contribution of studies using human cell models towards firefighters' occupational

Firefighters are the principal line of defense against fires, being at elevated risk of exposure to health-relevant pollutants released during fires and burning processes. Although many biomonitoring studies exist, only a limited number of human in vitro investigations in fire risk assessment are currently available. In vitro studies stand out as valuable tools to assess the toxicity mechanisms involved following exposure to fire pollutants at a cellular level. The aim of the present review was to contextualize existing in vitro studies using human cell models exposed to chemicals emitted from fire emissions and wood smoke and discuss the implications of the observed toxic outcomes on adverse health effects detected in firefighters. Most of the reported in vitro investigations focused on monocultures respiratory models and exposure to particulate matter (PM) extracts collected from fire effluents. Overall, (1) a decrease in cellular viability, (2) enhanced oxidative stress, (3) increased pro-inflammatory cytokines levels and (4) elevated cell death frequencies were noted. However, limited information remains regarding the toxicity mechanisms initiated by firefighting activities. Hence, more studies employing advanced in vitro models and exposure systems using human cell lines are urgently needed taking into consideration different routes of exposure and health-related pollutants released from fires. Data are needed to establish and define firefighters' occupational exposure limits and to propose mitigation strategies to promote beneficial human health.

Synthesis of 3D Hollow Layered Double Hydroxide-Molybdenum Disulfide Hybrid Materials and Their Application in Flame Retardant Thermoplastic Polyurethane

The development of high-performance thermoplastic polyurethane (TPU) with high flame retardancy and low toxicity has always been the focus of its research. In this paper, the novel 3D hollow layered double hydroxide/molybdenum disulfide (LDH/MoS₂) hybrid materials were synthesized by hydrothermal method using the MIL-88A as in situ sacrificial template and MoS₂ as synergistic flame retardant. Among all TPU composites, the peak heat release rate, total heat release rate, and total smoke release rate of TPU/NiFeTb-LDH/MoS₂ were reduced by 50.9%, 18.2%, and 35.8% compared with pure TPU, respectively. The results of the thermogravimetric infrared analysis demonstrated that the contents of combustible volatiles (hydrocarbons) and toxic volatiles (CO and HCN) emitted from TPU/LDH/MoS₂ were significantly reduced, indicating that LDH/MoS₂ hybrid materials can dramatically enhance the fire safety of TPU composites. Combined with the analysis of carbon residues and thermal stability of TPU composites, the enhanced flame retardancy and smoke suppression performances are primarily attributed to the catalytic carbonization of LDH and the physical barrier effect of MoS₂.

Properties of multifunctional composite materials based on nanomaterials: a review

Composite materials are being used for high-end applications such as aviation technology, space ships, and heavy equipment manufacturing. The use of composite materials has been observed in recent advancements in the field of multifunctional composite materials (MFCMs). There is continuous progress related to improvements, innovations, and replacement of metals inspite of rigorous destructive and non-destructive testing, proving the toughness and lifelong durability of such materials. The present study aims to review the topics relevant to modern multifunctional composite materials. The reviewed articles mostly cover the field of MFCMs based on nanomaterials. The structural functions emphasize on the mechanical properties such as fracture toughness, strength, thermal stability, damping, stiffness, and tensile strength. The non-structural properties include biodegradability, thermal conductivity, electrical conductivity, and electromagnetic interference (EMI) shielding. The study has concluded that the applications of multifunctional nanoparticle-based composite materials and structures include durable but light-weight aircraft wings, components and structures of electric self-driving vehicles, and biomedical composite materials for drug delivery.

Composite materials are being used for high-end applications such as aviation technology, space ships, and heavy equipment manufacturing.

Bi2Se3 decorated recyclable liquid-exfoliated MoS2 nanosheets: Towards suppress smoke emission and improve mechanical properties of epoxy resin

Bimetallic compounds have been proved superior suppression effect on smoke emission during combustion of polymers. In this work, MoS₂/Bi₂Se₃ (MB) hybrids were prepared by a facile wet chemical method and showed superior performance on smoke suppression of EP matrix during combustion. N-vinyl pyrrolidone (NVP) was employed to exfoliate molybdenum disulfide (MoS₂) nanosheets in a recyclable method, which showed high efficiency and was recyclable. Exfoliated MoS₂ exhibited large surface area and used as carriers to synthesize MB hybrids. Considering the catalytic effect of bismuth and molybdenum, the hybrids had a great influence on the smoke emission behaviors of EP composites. The smoke production was obviously suppressed during the flaming combustion (more than 22% and 23% decrease obtained from cone calorimeter and steady state tube furnace, respectively) or smolder processes (more than 23% decrease obtained from smoke chamber) at only 1 wt% content of MB hybrids. What's more, due to superior dispersion state, the addition of MB hybrids also enhanced the mechanical properties of EP matrix, including wear resistance and tensile property. This work provided a safe and green exfoliation method of MoS₂ to prepare polymers/MoS₂ composites and also constructed a novel binary hybrids for enhancing combination performances of polymers.

Effect of cuprous oxide with different sizes on thermal and combustion behaviors of unsaturated polyester resin

Cuprous oxide (Cu₂O) as an effective catalyst has been applied to enhance the fire safety of unsaturated polyester resin (UPR), but the particle size influence on combustion behaviors has not been previously reported. Herein, the UPR/Cu₂O composites (metal oxide particles with average particle-size of 10, 100, and 200nm) were successfully synthesized by thermosetting process. The effects of Cu₂O with different sizes on thermostability and combustion behaviors of UPR were characterized by TGA, MCC, TG-IR, FTIR, and SSTF. The results revel that the addition of Cu₂O contributes to sufficient decomposition of oxygen-containing compounds, which is beneficial to the release of nontoxic compounds. The smallest-sized Cu₂O performs the excellent catalytic decomposition effect and promotes the complete combustion of UPR, which benefits the enhancement of fire safety. While the other additives retard pyrolysis process and yield more char residue, and thus the flame retardancy of UPR composites was improved. Therefore, catalysis plays a major role for smaller-sized particles during thermal decomposition of matrix, while flame retarded effect became gradual distinctly for the larger-sized additives.

Space-Confined Growth of Defect-Rich Molybdenum Disulfide Nanosheets Within Graphene: Application in The Removal of Smoke Particles and Toxic Volatiles

In this work, molybdenum disulfide/reduced graphene oxide (MoS₂/RGO) hybrids are synthesized by a spatially confined reaction to insert the growth of defect-rich MoS₂ nanosheets within graphene to enable incorporation into the polymer matrix for the application in the removal of smoke particles and toxic volatiles. The steady-state tube furnace result demonstrates that MoS₂/RGO hybrid could considerably reduce the yield of CO and smoke particles. The TG-IR coupling technique was utilized to identify species of toxic volatiles including aromatic compounds, CO, and hydrocarbons and to investigate the removal effect of MoS₂/RGO hybrids on reducing toxic volatiles. The removal of smoke particles and toxic volatiles was attributed to the adsorption capacity derived from edges sites of MoS₂ and the honeycomb lattice of graphene, as well as the inhibition of nanobarrier resulting from two-dimensional structure. The work will offer a strategy for fabricating graphene-based hybrids by the space-confined synthesis and exploiting the application of space-confined graphene-based hybrid.

Integrated effect of supramolecular self-assembled sandwich-like melamine cyanurate/MoS2 hybrid sheets on reducing fire hazards of polyamide 6 composites

A novel strategy of using supramolecular self-assembly for preparing sandwich-like melamine cyanurate/MoS₂ sheets as the hybrid flame retardants for polyamide 6 (PA6) is reported for the first time. The introduction of MoS₂ sheets function not only as a template to induce the formation of two-dimensional melamine cyanurate capping layers but also as a synergist to generate integrated flame-retarding effect of hybrid sheets, as well as a high-performance smoke suppressor to reduce fire hazards of PA6 materials. Once incorporating this well-designed structures (4wt%) into PA6 matrix, there resulted in a remarkable drop (40%) in the peak heat release rate and a 25% reduction in total heat release. Moreover, the smoke production and pyrolysis gaseous products were efficiently suppressed by the addition of sandwich-like hybrid sheets. The integrated functions consisting of inherent flame retarding effect, physical barrier performance and catalytic activity are believed to the crucial guarantee for the reduced fire hazards of PA6 nanocomposites. Furthermore, this novel strategy with facile and scalable features may provide reference for developing various kinds of MoS₂ based hybrid sheets for diverse applications.

Enhanced fire-retardancy of poly(ethylene vinyl acetate) electrical cable coatings containing microencapsulated ammonium polyphosphate as intumescent flame retardant

There is a need to improve and maintain the protection function of ethylene-vinyl acetate copolymer (EVA) cable materials from ageing degradation to avoid fire hazards and extend their service lives.

Recent studies on the decomposition and strategies of smoke and toxicity suppression for polyurethane based materials

This review provides insight into recent studies related to thermal degradation, smoke and toxicity production and their reduction strategies for polyurethane-based materials.

Themoxidative stability and char formation mechanism for the introduction of CNTs and MoS2 into halogen-free flame retarding TPEE

In this study, we give an insight into the char formation mechanism for the addition of CNTs and MoS₂ into halogen-free flame retarding thermoplastic poly(ether ester) elastomers (TPEE).

Self-assembly fabrication of a graphene/multi-walled carbon nanotube hybrid material for suppressing potential heat radiation and toxic effluent

Negative graphene oxide was combined with positive chitosan-modified multi-walled carbon nanotubes in aqueous solution and then thermally reduced to fabricate a multi-walled carbon nanotube/graphene (MWCNT/G) hybrid material.