A persistent black-eye and challenge for polymers used in durable settings is their lack of fire resistance. Being made of mostly carbon and hydrogen (although other elements are used too), they tend to catch fire. That fire then spreads to the rest of the plastics and often to surrounding surfaces as the burning plastic melts and falls away. Foams are particularly prone to this behavior as they are already pre-filled with oxygen inside the foam and are structurally weak.
Flame retardants can be added to polymers to increase their flame resistance. While they can work quite nicely, they bring plenty of baggage with them. The most effective (on a weight basis) are based on brominated compounds, but there are plenty of health and environmental concerns about their usage, especially in regions of the world that seem to be worried about chemicals in general (Europe, California...). If you are trying to sell your products widely, you can't overlook those concerns. Inorganic materials such as aluminum trihydride can be used, but in that case, you are filling up your polymer with small rocks. This not only makes it heavier, but it also hurts many of the mechanical properties. These are fillers after all. Functional fillers, but fillers nonetheless.
The biggest disadvantage of these flame retardants is that they are added throughout the polymer even thought they are really only needed at the surface. That's why I'm excited about a new paper in Macro Letters (open access for just a few days) which describes a process for creating an electrodeposited coating that is flame retardant. Being a coating, it's only appears where it is needed, but what is more exciting yet is that it's based on sulfur, and that's a first as far as I know. It's a short report, but in it, the researchers showed that when applied to polyurethane foam, the foam not only did not propagate the flame, but it also did not slough off molten material.
As with any academic research, lots of effort will be needed to turn this into a viable option, as apply 10 layers of the coating (as was done in this case) is not going to be a viable option for most applications, but as is so often the case, once the initial prototype is shown, the floodgates will open and this (or something similar) will become part of our lives.
Everything flows, but only the macromolecules are worth the time.
3 comments:
Did you investigate the background of the lead author? He's a Mat. Sci. & Eng. PhD grad from your undergrad department. He could be considered a large "C" Mat. Sci. grad. (his undergrad. degree was Chemistry from NDSU). Viz. a previous blog topic of yours, the quantum mechanics aspect of his work isn't apparent.
No, I was not aware of the common background. Thanks for pointing it out.
I do think you mean the PI (Grunlan), not the lead author.
I meant the PI, Grunlan. It's been many years since I was conversant with such open literature conventions. I don't even remember how to format a citation. As an industrial technologist, it's been displaced by quality, credit, and shipping conventions.
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