Nanosized fire retardants
With the advent of nanotechnology in the past few decades, the prospects of nano scale fillers in polymer-based composites in the flame retardancy applications have progressed rapidly. Although nanofillers do not show excellent fire retardance inherently, incorporation of low amount of them in polymer composites tend to provide drastic improvement in thermal stability, smoke release amount, peak heat release rate and the speed at which flames spread throughout the nanocomposites. The main mechanism of fire retardancy for nanocomposites, which happens in the condensed phase, depends on different factors including structure and chemical composition of the nanofiller. In general, the presence of nanofillers in polymer matrix can alter the overall response of nanocomposites during exposure to flame. A list of most commonly used nanofillers in nanocomposites with the aim of fire retardant is summarized in Table 2.
TABLE 2. List of common nano flame retardants in polymer composites
Nanofiller | Nanofiller loading | Polymer matrix | References | |
Metallic particles | ZnO2 nanowires | 10–40 wt% | Polypropylene | |
Aluminum tri-hydroxide (ATH) | 8–14 wt% | Polyurethane foam | ||
Zinc oxide | 1 wt% | Polypropylene-ethylene-propylene-diene monomer | ||
Nanoclay | 1–3 wt% | Polystyrene | ||
Bio based fillers | Lignin | 15–20 wt% | Polypropylene | |
Starch | 10 wt% | Polylactic acid | ||
Proteins | 20 wt% | Polyester | ||
Cellulose nanocrystals (treated) | 10 wt% | Polylactic acid | ||
Intumescent flame retardant | 20 wt% | Polylactic acid | ||
Carbon family | Carbon nanotube | 0.25 wt%1 vol% | Epoxy–polypropylene | |
Graphene | 2 wt% | Polyurethane, polypropylene | ||
Fullerene | 2 wt% | Polypropylene |
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