Combustion of ethylene-vinyl acetate copolymer filled with aluminium and magnesium hydroxides

Enhanced Flame Retardancy in Ethylene-Vinyl Acetate Copolymer/Magnesium Hydroxide/Polycarbosilane Blends

A polymer ceramic precursor material—polycarbosilane (PCS)—was used as a synergistic additive with magnesium hydroxide (MH) in flame-retardant ethylene–vinyl acetate copolymer (EVA) composites via the melt-blending method. The flame-retardant properties of EVA/MH/PCS were evaluated by the limiting oxygen index (LOI) and a cone calorimeter (CONE). The results revealed a dramatic synergistic effect between PCS and MH, showing a 114% increase in the LOI value and a 46% decrease in the peak heat release rate (pHRR) with the addition of 2 wt.% PCS to the EVA/MH composite. Further study of the residual char by scanning electron microscopy (SEM) proved that a cohesive and compact char formed due to the ceramization of PCS and close packing of spherical magnesium oxide particles. Thermogravimetric analysis coupled with Fourier-transform infrared spectrometry (TG–FTIR) and pyrolysis–gas chromatography coupled with mass spectrometry (Py–GC/MS) were applied to investigate the flame-retardant mechanism of EVA/MH/PCS. The synergistic effect between PCS and MH exerted an impact on the thermal degradation products of EVA/MH/PCS, and acetic products were inhibited in the gas phase.

Investigation of Different Types of Biochar on the Thermal Stability and Fire Retardance of Ethylene-Vinyl Acetate Copolymers

In this work, three biochars, deriving from soft wood, oil seed rape, and rice husk and differing as far as the ash content is considered (2.3, 23.4, and 47.8 wt.%, respectively), were compounded in an ethylene vinyl acetate copolymer (vinyl acetate content: 19 wt.%), using a co-rotating twin-screw extruder; three loadings for each biochar were selected, namely 15, 20, and 40 wt.%. The thermal and mechanical properties were thoroughly investigated, as well as the flame retardance of the resulting compounds. In particular, biochar, irrespective of the type, slowed down the crystallization of the copolymer: this effect increased with increasing the filler loading. Besides, despite a very limited effect in flammability tests, the incorporation of biochar at increasing loadings turned out to enhance the forced-combustion behavior of the compounds, as revealed by the remarkable decrease of peak of heat release rate and of total heat release, notwithstanding a significant increase of the residues at the end of the tests. Finally, increasing the biochar loadings promoted an increase of the stiffness of the resulting compounds, as well as a decrease of their ductility with respect to unfilled ethylene vinyl acetate (EVA), without impacting too much on the overall mechanical behavior of the copolymer. The obtained results seem to indicate that biochar may represent a possible low environmental impact alternative to the already used flame retardants for EVA, providing a good compromise between enhanced fire resistance and acceptable mechanical properties.

Development of metal hydroxide nanoparticles from eggshell waste and seawater and their application as flame retardants for ethylene-vinyl acetate copolymer (EVA)

Recently, calcium hydroxide and magnesium hydroxide nanoparticles have attracted a lot of research interest in different sectors: food, packaging, health, automotive construction and food application. In the present study, we report development of bio-material calcium hydroxide nanoparticles (Ceg-Ca(OH)₂), obtained from chicken eggshell collected from the food industries as well as magnesium hydroxide nanoparticles obtained from seawater (Seaw-Mg(OH)₂). The flame-retardant behavior of Ethylene-Vinyl Acetate copolymer (EVA) containing different blends of Ceg-Ca(OH)₂ and Seaw-Mg(OH)₂ nanoparticles has been evaluated using cone calorimeter. Our results showed the interest of combining both nanoparticles. In fact, the partial substitution of small Seaw-Mg(OH)₂ content (10 wt%) by Ceg-Ca(OH)₂ enables further reduction of pHRR from 251 to 206 kW/m² without any reduction of the composite time to ignition (52 s). Furthermore, the partial substitution of 40 wt% Seaw-Mg(OH)₂ nanoparticles by Ceg-Ca(OH)₂ enables high flame retardant effect as well as the generation of cohesive residue.

End-of-life of silicon PV panels: A sustainable materials recovery process

In this paper, the management of end-of-life PV modules based on an advanced eco-sustainable process has been presented and discussed. The thermal removal of the polymeric compounds contained in c-Si PV modules has been investigated to separate and recover Si, Ag, Cu, Al and glass. A two-step thermal process has been employed. In the first step, the rear polymeric layer has been removed without emissions of dangerous fluorinated substances. In the second step, the remaining polymers have been completely removed with low volatile organic compounds (VOCs) emissions. The polymers degradation has been studied at combustion equivalent ratios Φ varying from 0.5 to 2 and at 500 °C. The materials recovery has been evaluated from an environmental point of view and optimized by considering the energy cost, through the identification of the best operating conditions, in terms of temperature, time, atmosphere and gas flow. One hour of heat treatment and a slightly oxidizing atmosphere have been enabled to separate and recover the different materials of the module. The elemental compositions of the PV sample and the residue condensed organic products have been determined. The gaseous degradation products have been characterized by gas chromatographic analysis (GC).

Enhanced flame retardancy of polyethylene/magnesium hydroxide with polycarbosilane

Polycarbosilane (PCS) was used for surface modification of magnesium hydroxide (MNH) to enhance the flame retardant effectiveness by forming cohesive binding between MgO particles with ceramic adhesive. Chemical interaction and ceramic reaction were revealed between PCS and MNH, which made for a compact, thermal stable and ceramic-like barrier during the combustion of polyethylene (PE). The flame retardancy of PE/MNH/PCS composites was greatly enhanced and a limiting oxygen index (LOI) of 35.0 was achieved at the PCS/MNH ratio of 4/26 in the composite with 30 wt.% PCS modified MNH. Such results were superior in terms of high LOI value at low global content of MNH. Thanks to the better shielding effect of the integrated and self-supporting ceramic char, the peak heat release rate (p-HRR) and the total heat release (THR) of PE/MNH/PCS composites with 50 wt.% PCS modified MNH were remarkably decreased by 36% and 25% in comparison with PE/MNH with 50 wt.% MNH, respectively. The ceramic reaction between PCS and MNH, the superior thermal stability due to crosslinked PCS and the good barrier function of cohesive ceramic layer play important roles in the effective flame retardant mechanism.

PGS@B–N: an efficient flame retardant to improve simultaneously the interfacial interaction and the flame retardancy of EVA

EVA/PGS@B–N composites with suitable loadings of PGS@B–N particles have significantly improved flame retardancy.

Flammability and Thermal Characterization of Aluminum Hydroxide Filled with LDPE

Aluminum hydroxide (ATH), a non-toxic and environmentally friendly flame retardant, was characterized using thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The effect of ATH content on flammability properties of LDPE was also determined using limiting oxygen index (LOI) and smoke density test. The thermal characterization studies showed that the effective temperature range for ATH as a flame retardant is 200 to 350°C. In water release test, it was determined that the release of the water by ATH degradation in ATH increased with increasing temperature. The LOI test showed that the flame retardancy of LDPE increased with increasing ATH content and decreasing ATH particle size. The smoke density test proved that addition of ATH reduced effectively the smoke density of a burning LDPE. It was studied in this paper the effect of ATH particle size on thermal, flammability and viscosity of ATH filled with LDPE.