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How Is Polyethylene Foam So Flame Retardant?

March 24, 2020
Polyethylene foam offers several, well recognized, benefits upon usage as a material when manufacturing certain products. 

Some of the properties of this foam include, but are not limited to, low moisture permeation, insulating and damping characteristics, and rebound resilience. 

On top of this, these foams demonstrate an innate resistance against fire which can be further enhanced by way of additives and other ingredients, which will be the focus of today’s piece. To set things off, it’s best we understand how increasing resilience in this foam necessitates flame retardation. 

The science behind resilience

Polyethylene foam resilience is enhanced through the addition of polyethylene-octylene elastomers, which plays a substantial role in improving the flexibility of the cell walls. This trait can be further advanced depending on the volume of polyethylene-octylene elastomer used. Corollary to all this is that the foam becomes increasingly combustible, limiting its practical applications. 

How fireproofing works

Aforementioned issues are addressed through various anti-flaming methods which come as a consequence of a synergistic system of halogens and oxides. A natural consequence of this is that the process can produce smoke and toxic gases from the halogens. That being said, flame retardants containing almost zero to no halogens are being developed as a more viable alternative. 
The formulation of polyethylene foam that contains no halogens is made possible by using magnesium hydroxide as the flame retardant chemical. Moreover, additional processes such as chemical cross-linking, high-temperature melting, and mold pressing are implemented to come up with modified low-density foam and ethylene-vinyl acetate or EVA. With processes like these in place, the resulting foam showcases a significant advance in fire resistance. 
So what of their use? Fire resistant foam like this is unmatched in their use as panels and sandwich structures to protect oil wellheads. To an even greater degree, when combined with polypropylene foam, they make for fantastic multilayer composites for damping purposes, e.g. a helmet comprised of alternating layers of polyethylene and polypropylene foam at the core.