New memory foam mattress companies are popping up everywhere – But are these chemical mattresses safe? Find out as we break down the chemical building blocks used to make them.
What Is Memory Foam?
Memory foam mattresses are made from a modified version of polyurethane foam – The technical name for memory foam is visco-elastic polyurethane. Exact chemical recepies vary between manufacturers, but the basic chemical building blocks remain the same.
The Two Main Ingredients In Memory Foam
Memory foam (visco-elastic polyurethane) is formed by a chemical reaction between two main ingredients; polyols and isocyanates. The raw material in polyols and isocyanates are crude oil and natural gas – although a portion of polyol content may come from plant based sources.
Polyols are petrochemical alcohols which react with isocyanates. The majority of polyurethane foams use polyols called polyethers.
Some manufactures combine petrochemical polyols with plant based polyols to make bio-foams. The amount of plant based polyols in a bio-foam mattresses is typically within somewhere in the range of 20-50% of total polyol content. NO polyurethane based foams (such as memory foam) can be wholly derived from plant based polyols.
Isocyanates are petrochemicals which react with polyols to form the ‘urethane linkages’ which make up polyurethanes linked structure.
One of two isocyanates are commonly used in memory foam production; MDI – diphenylmethane diisocyanate, and TDI – toluene diisocyanate. 95% of memory foam mattresses are produced using either MDI or TDI according to EssentialChemicalIndustry.org.
- TDI reacts toluene with acids like sulphuric and nitric acid. This mix produces TDA (diaminotoluenes) which in addition is reacted with phosgene. This mix is further refined to produce TDI, a volatile and known toxic chemical. Because of this strict precautionary measures must be taken to avoid exposure to harmful vapours released during the manufacturing process.
- MDI is made by reacting formaldehyde with aniline using a hydrochloric acid catalyst. This creates MDA (methylenedianiline) which is then reacted with phosgene, and further refined to produce MDI. (Flexible Polyurethane (PU) FoamEUROPUR August 2015)
According to the Swedish Chemicals Agency, isocyanates can cause allergies and respiratory damage when vapours are inhaled. In addition some are known to be cancerous, classified as environmentally harmful, and particularly toxic to marine life.
“…Buying natural alternatives free of polyurethane foams are the only surefire ways to keep the toxins out…”
– Ali Emerson from GreenFuture.io/sustainable-living
Chemical additives are mixed in with polyols to give polyurethane foam additional properties;
Cross Linkers and Chain Extenders
Cross linking and chain extending chemicals are added to increase flexibility, as polyols with longer molecular chains and low cross linking (the amount of bonds between polyol molecules) make for a stretchier elastic polyurethane – Aka memory foam.
Conventional polyurethane foams are highly flammable because of their high petrochemical content, and therefore they need to be treated with chemical flame retardants.
The worst known retardants contained PBDEs, and were banned in 2003 after they were found to be carcinogenic. However, PBDEs were simply replaced with new chemicals, which do not have to be disclosed by manufactures.
The trouble with new chemicals is that they are considered safe until proven otherwise. It takes time and research to prove a chemical is dangerous, which may not be acted upon unless organisations like the EPA are pressured to do so.
Lastly, additives including surfactants, blowing agents, pigments, fillers, stabilisers and catalysts may also be added to the polyol mix to give the finished foam different properties like increased elasticity or density.
Polyurethane may be considered inert once “cured”, although I prefer to avoid polyurethane and chemical based mattresses all together, and go for natural alternatives. Natural mattresses reduce exposure to harmful off-gassing chemicals and because they are based on sustainable and renewable materials, they also much less intensive on the environment.
See The Natural Mattress List
Click the green button below to see the list which compares and reviews all the best natural non-toxic mattresses.