Smoldering and Flame Resistant Textiles via Conformal Barrier Formation

Dimethylcyclosiloxanes in Mobile Smart Terminal Devices: Concentrations, Distributions, Profiles, and Environmental Emissions

Dimethylcyclosiloxanes (DMCs) are utilized as vital monomers in the synthesis of organosilicon compounds, integral to the manufacture of mobile smart terminal devices. Toxicological studies have revealed potential endocrine-disrupting activity, reproductive toxicity, neurotoxicity, and other toxicities of the DMCs. This study investigated the concentrations and composition profiles of seven DMCs, including hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), and tetradecamethylcycloheptasiloxane (D7), hexadecamethylcyclooctasiloxane (D8), and octadecamethylcyclononasiloxane (D9) in three types of mobile smart terminal device components (silicone rubber, adhesive, and plastics). Environmental emissions of DMCs from silicone rubber materials were also estimated to improve the recognition of their potential fate within the environment. D5-D9 were widely present in silicone rubber and adhesives with detection rates ranging from 91-95.5% and 50-100%, respectively, while D3 and D4 were more frequently detected in plastics, both showing a detection rate of 61.1%. Silicone rubber had the highest total DMCs (∑7DMCs) and a concentration of 802.2 mg/kg, which were dominated by D7, D8, and D9. DMCs detected in adhesives were dominated by D4, D5, and D6. The estimated emission of ∑DMCs released into the environment in China from silicone rubber used in mobile smart terminal devices exceeds 5000 tons per year. Further studies are needed on the presence of DMCs in various commodities and environmental media to assess their ecological and human health impacts, as well as the toxicological effects of D7-D9 for the appropriate regulation of these chemicals.

Fire behavior of innovative alginate foams

A new biosourced composite foam (AF, associating foamed alginate matrix and orange peel filler) is successfully tested for fire-retardant properties. This material having similar thermal insulating properties and density than fire-retardant polyurethane foam (FR-PUF, a commercial product) shows promising enhanced properties for flame retardancy, as assessed by different methods such as thermogravimetric analysis (TGA), pyrolysis combustion flow calorimetry (PCFC) and a newly designed apparatus called RAPACES for investigating large-scale samples. All these methods confirm the promising properties of this alternative material in terms of fire protection (pHRR, THR, EHC, time-to-ignition, flame duration or production of residue), especially for heat flux not exceeding 50 kW m^-2. At higher heat flux (i.e., 75 kW m^-2), flame retardant properties tend to decrease but maintain at a higher level than FR-PUF. The investigation of the effect of AF thickness shows that the critical thickness (CT) is close to 1.5-1.7 cm: heat diffusion and material combustion are limited to the CT layer that protects the underlying layers from combustion. A multiplicity of factors can explain this behavior, such as: (a) negligible heat conduction, (b) low heat of combustion, (c) charring formation, and (d) water release. Water being released from underlying layers, dilutes the gases emitted during the combustion of superficial layers and promotes the flame extinction.

A novel application of silicone-based flame-retardant adhesive in plywood

A silicone-based elastomer filled with vinyl-silane treated aluminum hydroxide was used to replace conventional polyurethane-based adhesive to provide a flame-retardant adhesive for plywood. The shear strength and fire performance of such a silicone-based (SI) adhesive glued plywood (SI/plywood) were investigated and compared to those of the polyurethane-based (PU) adhesive glued plywood (PU/plywood). The shear strength of the SI/plywood [(0.92 ± 0.09) MPa] was about 63% lower than that of the PU/plywood at room temperature, but it was less sensitive to water (62% reduction for the PU/plywood and 30% reduction for the SI/plywood after hot-water immersion at 63 °C for 3 h). The fire performance of plywood was assessed by a simulated match-flame ignition test (Mydrin test), lateral ignition and flame spread test, cone calorimetry, and thermocouple measurements. With a higher burn-though resistance and thermal barrier efficiency, and lower flame spread and heat release rate, the SI/plywood exhibited a superior fire-resistance and reaction-to-fire performance and improved fire-resistance as compared to the PU/plywood. The SI adhesive generated an inorganic protective layer on the sample surface that visibly suppressed glowing and smoldering of the plywood during combustion. The SI adhesive was also combined and reinforced with cellulosic fabric (CF) or glass fabric (GF) to prepare composite plywood (SI/CF/plywood and SI/GF/plywood) with improved fire performance. The cone calorimetry and thermocouple measurements indicated that the use of CF or GF in SI/CF/plywood and SI/GF/plywood, respectively, suppressed the delamination and cracking of the composite plywood and promoted the formation of an effective thermal barrier during smoldering and flaming combustion. Particularly, the SI/GF/plywood exhibited the most effective fire barrier with no crack formation, and the lowest heat release rate among the plywood types investigated in this study.