Disposing of Scrap Foam
by Duncan Geddes
Within the foam industry, the disposal of scrap foam is becoming an increasingly important subject for both the manufacturers and converters of polyurethane foam. Foam is inherently a volumetric, but light-weight material, so what methods are there to dispose of scrap foam?
A brief history of scrap foam
Flexible polyurethane foams were originally developed during World War II, for use as aircraft coatings. However, production was small, and it wasn’t until the 1950s that chemical giants such as DuPont, BASF and Dow Chemicals started developing toluene diisocyanate and polyurethane polyols, which were required to manufacture commercial scale volumes of polyurethane foam.
From the day that the first ever block of polyurethane foam was made and converted into cut parts, the question has been raised ‘what do we do with the remaining scrap’?
Production efficiency dictates that the foam convertor aims to produce as many components as possible from the block, therefore minimising the amount of scrap foam, but every single block of foam that has been converted since the 1950s, has created a small amount of scrap foam.
During the last 60 years, this must now total millions of tonnes of polyurethane foam, maybe more…where has that foam gone? The same question can be applied to polyethylene foam (closed cell material).
Methods to dispose of scrap foam
Flexible polyurethane foam can be burnt, but this process generates toxic fumes, so this is a hazardous process. Finding a new application is far better, and fits in with the modern day aspirations of recycling all our scrap materials, but to-date the only volumetric use for scrap polyurethane foam is re-constituted foam (aka chip-foam).
This is basically the process of granulating foam into small pieces of a few millimetres in size, and re-bonding them into large block form, which are then compressed to various densities. Applications for chip-foam include packaging, floor mats, sound absorption panels, but the main use is as a carpet underlay.
Manufacturers of carpet underlay are therefore driven by the need for their respective plants to obtain as much scrap foam as possible, meaning over the years they have established efficient methods of collecting scrap foam from foam convertors around the world, and shipping it back to their underlay factories.
However, although this process uses a large amount of scrap foam, it does generally require ‘virgin’ material. Effectively, if the foam has been laminated to fabric or adhesive tape, this renders it unusable for carpet underlay.
The same issues apply to closed cell polyethylene foam. Again, scrap ‘virgin’ foam is collected from foam convertors, taken back to a manufacturing plant where it is granulated, and then used to produce items such as floor-mats and playground mats. Scrap polyethylene foam that has been subjected to additional conversion processes can’t be re-processed.
So what happens to all the scrap foam that can’t be recycled? Also, what about the polyurethane dust, block skins etc, which are not suitable ‘virgin’ foam? Where does that go? We know that burning it is hazardous. In reality, landfill is still the only real option.
So, what’s next?
Two species of the Ecuadorian fungus Pestalotiopsis are capable of biodegrading polyurethane in aerobic and anaerobic conditions such as found at the bottom of landfills, but this takes hundreds of years. Studies to date have not determined how to speed up degradation methods.
This creates a huge challenge for the foam industry, and also for those consumers who care about their environment. Polyurethane foams are used in a vast range of applications – furnishings, cars, white goods, flooring and sponges among others. We see and encounter foam every day, on many occasions. There is a need to develop a new product for scrap foam. Re-constituted foam (chip-foam) as used in carpet underlay, has been a successful start, so what is the next step?