How is Memory Foam Made?
It’s comfortable and relaxing, but how is it actually made?
In the case of memory foam, the manufacturing process used is a batch process for making certain shapes by cutting or molding foam. There are two types of foam: flexible and rigid. Flexible foam, with its open cell structure and ability to form high and low densities, is what memory foam is made of. Rigid foam uses a closed cell structure that prevents gas movement between cells, and is used in applications such as building insulation, refrigerator & freezer insulation, etc.
Foam is typically made of either latex or polyurethane, the latter of which is much more commonly used. Polyurethane foam is usually made up of a mixture of polyol, polyisocyanates and water, among other chemicals. Combining water with polyol and polyisocyanates produces an exothermic reaction which forms polyurethane. The type of polyol used in this polymerization (the chemical reaction which forms a 3 dimensional network, or in this case, foam) determines whether the foam will be rigid or flexible.
Additives are used to assist in certain chemical reactions, such as speeding up the reaction of the polyisocyanates and polyols. Tin and amines (which are catalysts) are responsible for this. Other additives like blowing agents are necessary to form the gas bubbles in the foam. Adjusting the water levels modifies the amount of gas bubbles formed in the foam. The size of the bubbles is controlled by using surfactants, which are wetting agents that lower liquid surface tension. Interestingly enough, there are naturally occurring surfactants in the human lungs, made of lipoprotein, that maintain pulmonary tissue stability. They do this by reducing the surface tension of the fluids that coat the lung.
Some other additives used may include cross-linking agents, flame retardants, colouring materials, fillers, and chain-extending agents.
On average, polymerization can last from several seconds to around 5 minutes.
Liquid chemicals are delivered to the manufacturing facility and stored in large holding tanks. When it’s time to use them, the chemicals are pumped into smaller mixing tan
ks which are heated. Metered pumps measure certain amounts of each chemical which are fed into a mixing head – this is where the chemicals blend and react (see Step 1 of Fig. A).
The components are then poured onto a conveyor belt (Step 2), and the foam begins to rise and cure (Step 3).
Further down the conveyor belt, the foam is sliced by an automatic saw into pieces around 12 feet long (Step 4), then set to rest at room temperature for about 12 hours to allow proper curing (Step 5). The foam is not ready to be stacked, as it is too early to tolerate any weight. After curing is complete, the foam is cut into desired dimensions by a second saw.
What happens to the leftover foam?
There are many different ways to recycle polyurethane. Most recycling methods involve reusing foams for carpet back/cushioning. To do this, scrap is shredded into flakes and bonded together to form sheets. Another method involves fragmenting the excess foam, then dispersing the fragments into a polyol blend, using them in the same way as originally used.