Keeping Up with Polyurethane

Over the course of the semester, I have mentioned a bunch of different things about polyurethane and the shift of the blog has really moved from memory foam to polyurethane as a whole, which I think is actually a better topic to have since it provides a much broader picture of the material than just the one industrial use I was initially focusing on.

Anyway, overall, it basically seems to me that polyurethane is definitely here to stay and unless we find another revolutionary material, there just isn’t anything quite good enough to replace PU just yet. In my second post, I focused on just how much we use this material and the extensive demand there is for polyurethane since it can be applied to so many different industries. This demand is really supported by the fact that PU is really useful for energy considerations. It lowers the energy requirement of the houses by a significant amount and, with the new synthesis methods using CO2 as a feed source, the energy requirements for making PU and the environmental impact of the synthesis process can be reduced enough that this material is a very sustainable material for a myriad of applications.

The changes that are currently underway, such as using the CO2 feed source for manufacturing PU and recycling the material by turning it back into raw chemicals, are going to greatly improve sustainability. These changes are essential to reduce the synthetic demands since polyurethane requires oils to create. Being able to recycle CO2 and reuse the material would be great for reducing the oil demand.

As I’ve said before, heating and cooling houses use up a large amount of fossil fuels and being able to reduce this using polyurethane insulation almost makes up for the amount of oil needed for PU production but still, if this is reducible, then we should do everything in our power to make it happen. This is the kind of research many companies in Europe are working on and it’s essential to keep this up to find a way to make PU even more attractive, especially because its applications are endless in construction, automobiles, adhesives etc.

Based on all the research I’ve conducted for this blog, I’ve learned 2 main things about polyurethane. 1: The entire production and consumption is very regional and localized making the transportation costs virtually zero. and 2: The global energy implications are almost negligent. This basically shows just how useful and how popular polyurethane can be and using the previously suggested new methods of manufacture, we really can keep using polyurethane for many years to come.

 

References

EuroPur. “Recycling and Recovering Polyurethanes Options in Practise.” European Isocyanate Producers Association Journal (November 2005). Web.

One Voice, EUROPUR, and BING. “Polyurethanes: Sustainable Materials.”European Isocyanate Producers Association Journal – 11-98-ENV-0039-Fact Sheet (n.d.). Web.

Assen, Niklas Von Der, and André Bardow. “Life Cycle Assessment of Polyols for Polyurethane Production Using CO2 as Feedstock: Insights from an Industrial Case Study.” Green Chemistry Green Chem. 16.6 (2014): 3272.

 

 

 

 

 

 

 

 

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Need or Convenience?

 

Humans need polyurethane.

We have come to the point where the material is used in so many applications, that without polyurethane, a myriad of alternatives would have to be found to keep up the same level of work in the furniture, electronics, and construction industries. Especially in terms of construction, as I have shown in the past few posts, the foam insulation in housing is essential in keeping the energy emissions low.

As we try and move away from steel and other high energy intensity materials, PU is becoming more and more appealing throughout the world and it’s rarely considered a convenience anymore. This is even more true since research is continuously finding ways to produce the material with lower emissions [1]. There is consisted work going into reducing the impact of PU on a global scale and one of the biggest reasons this material is good for the world is because of how domestic it is.

The biggest contributions to polyurethane usage would definitely be coming from the T of PAT since as technology improves, there is a shift towards using PU over other, less sustainable materials. The population increase (P) in the world will also mean that more polyurethane is needed for insulating additional houses and demand will rise to 24mil. tonnes [2].

Memory Foam is a Convenience

No one actually needs memory foam, it is obviously a convenience. To be perfectly honest, we could all sleep on the floor and it wouldn’t be the end of the world. But as it does exist in the world, we should be doing what we can to reduce its global impact. And I think in that sense, what really makes a difference is the production process. This is the same as polyurethane, so similar approaches can be taken such as using CO2 capture in the production process, as suggested by German researchers [4].

In terms of memory foam, the biggest contributor to impact would probably technology and affluence. Memory foam mattresses are still more expensive than box springs so only the wealthier people are able to get them. As I mentioned once before, as more people move from rural to urban areas, consumers are trying more expensive goods clearly pointing to Affluence being the biggest contributor to memory foam impact [3]. Additionally, as technology improves, there are more variations on memory foams causing more people to want to try them out.

 

References

[1] MYRIANT CORPORATION. POLYURETHANES: THE CASE FOR RENEWABLE SUCCINIC ACID BASED POLYESTER POLYOLS. MYRIANT MEDIA. MYRIANT CORPORATION, 30 MAY 2013. WEB. 29 FEB. 2016.

[2] GOPAL, MADAN. GLOBAL POLYURETHANES MARKET SEGMENTED BY APPLICATION, INDUSTRY AND GEOGRAPHY TRENDS AND FORECASTS (2015 – 2020). REP. NO. 3311742. HYDERABAD: MORDOR INTELLIGENCE LLP, 2015. JAN 2016. REPORT BUYER. WEB. 29 FEB. 2016.

[3] GLOBAL MATTRESS MARKET SIZE, SHARE, DEVELOPMENT, GROWTH AND DEMAND FORECAST TO 2020. REP. NEW YORK: P&S MARKET RESEARCH, 2015. PRINT.

[4] ASSEN, NIKLAS VON DER, ANDRÉ STERNBERG, ARNE KÄTELHÖN, AND ANDRÉ BARDOW. “ENVIRONMENTAL POTENTIAL OF CARBON DIOXIDE UTILIZATION IN THE POLYURETHANE SUPPLY CHAIN.” FARADAY DISCUSS. 183 (2015): 291-307. ROYAL SOCIETY OF CHEMISTRY. WEB. 29 FEB. 2016

Impacts of Polyurethane

As I’ve mentioned before, polyurethane is actually one of the most sustainable materials out there. There are numerous ways that this material can be used in order to reduce the emissions from buildings, which is a major contributor to greenhouse gases and energy consumption throughout the world. [There is very little information available on memory foam energy impact, so this post will focus on polyurethanes as a whole]

Bringing PU to the Market

The regional production base for PU is one of the biggest factors helping its sustainability. This reduces the amount of energy required in transportation and disposal and what remains is the amount of energy needed for the actual production from raw materials. In looking at a normal production route for the material, there is about 0.36kW*h of electricity required to produce approximately 1kg of polyols (the primary component of PU) [1].

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Figure 1: Product system for making polyols

The global energies for this material are almost negligent and the manufacturing and extraction process, locally, are under consideration. Just because global energies are low, however, does not mean that the global warming impacts are low. The impact on the environment from the current production of polyols is estimated to be around 3.57kg CO2-equivalents.

Energy Impact

I showed a couple of posts back, that by using PU, house insulation is improved drastically, leading to a decrease in primary energy consumption. This can also be extended to industries like refrigeration and transportation of food etc. The amount of energy required to make polyurethane foams can be required in as little as 2 years from the energy saved by insulation [2]. This also extends to greenhouse gases with the amount of climate change avoided in just Minneapolis from insulation being as high as 3400 kg of CO2-equivalents from last year [2].

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Figure 2: Amount of energy saved by using PU insulation

Future Directions

While the energy considerations are low, the greenhouse gas impact still exists for PU and does create a problem in terms of usefulness and sustainability. Over the past few years, there has been significant work going into reducing this gas emission by using CO2 capture and recycling as a feed-source for making polyols.

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Figure 3: Global warming impacts of alternative polyol production

From the research that’s currently available, it seems that any of these alternative methods could be used in producing polyurethanes in a much more sustainable manner leading to this material really making an impact in the environment and the world.

References

[1] Assen, Niklas Von Der, and André Bardow. “Life Cycle Assessment of Polyols for Polyurethane Production Using CO2 as Feedstock: Insights from an Industrial Case Study.” Green Chemistry Green Chem. 16.6 (2014): 3272. Web.

[2] Spray Polyurethane Foam Alliance. Life Cycle Assessment of Spray Polyurethane Foam Insulation. Rep. Fairfax: SPFA, 2012. Print.

 

Rigid foams and foam-ier sleep

Everybody wants polyurethane. Sleepers want Memory Foam.

The global market for polyurethane (PU) is on the rise. According to recent reports, by 2020, the global market is expected to reach USD 37.5 billion (including all types of PU) [1].

I discussed the history of polyurethane and its discovery in my previous post, but the true potential for polyurethane wasn’t realized until quite recently. Over the past few years, the cost-effective production method and the adaptability of the material for a vast array of uses in major industrial applications has increased the demand and use of PU throughout the world. The global market includes a range of applications for PU, which is really segmented first by application then by industry and finally by geography [1].

PU occurs in two main forms – foams and non foams and there is a clear demand for both types of PU through the world in industries such as packaging, furniture, and cushioning (for foams), and insulation and construction (for non foams) [1]. Due to environmental regulations from other industrial sectors, there is a rise in PU demand, since PU materials are recyclable and we have not yet exhausted all ways of reducing its energy/environmental impact (which is often the case for materials that have been continuously studied and analyzed such as steel).

In a similar manner, the demand for memory foam (in the USA) is also on the rise with an annual growth rate of 7.6% in terms of the number of units created/shipped [2] with memory foam growing to be 20% of the mattress market, a sharp rise from 2008’s 14%. Due to the high number of people suffering from insomnia – nearly 60% of the American population – has led to a substantial increase in sleep aids and memory foam companies has jumped on this bandwagon like nobody else [3].

Another aspect driving the demand for memory foam is the move of people from rural to urban areas in regions like the Asia Pacific (APAC). Consumers are becoming more selective with what they sleep on and are choosing customized mattresses for more comfortable sleep leading to a shift towards memory foam. A certain rise in income leads to more people choosing to spend more on health enhancing products. This rise is more prevalent in North America and Europe but has made an emergence in Japan and India, leading to demand for memory foam in the APAC region, which was previously non-existent. Memory foam is also appealing to those looking for more eco-friendly mattresses since PU memory foam is being advertised as an environmentally sustainable material whereas inner-spring or coir mattresses are seen as materials resulting in more emissions [4].

Where is all the Polyurethane going – Demand and Disposal?

Turns out, the biggest consumers of PU is the APAC  regionwith approximately 47% of the world’s polyurethane being consumed and used by the industries based in the APAC region. Figure 1 [5] shows the consumers in 2012, but there has been an increase in the APAC region since this report.

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Figure 1: Global PU Market Share by Volume

The largest market for PU has consistently been the construction (37%), furniture, electronics, and automotive industries, together making up 73% of the world’s use with PU demand rising at an annual growth rate of 7.2% [6]. These industries and their demands have shown a prediction for global demand of approximately 24 million tons in 2020 as shown in figure 2 below [7]. In all these industries, the biggest competitors for PU are fiber glass and polystyrene [1]. In terms of my blog, focusing on memory foam, however, these aren’t really considered since they don’t offer the same kind of flexibility in terms of the foam structural element.

 

bio-based-polyurethane-industry
Figure 2: Global PU Market Volume by Product (Tons)

The market for polyurethane also reflects where it’s being made. There is a similar ratio in the world with respect to the countries/regions producing PU (fig. 3) with the maximum amount of production in Asia and high amounts in both Europe and North America.

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Figure 3: Production of PU in Global Regions

 

In terms of disposal, since PU is quite recyclable, each country has its own disposal and reuse methods and guidelines, some of these have been addressed in my previous posts. There really isn’t a transfer of material to other parts of the world for disposal since PU poses a minimal threat to the environment, and is being considered by a lot of people as a replacement for materials like polystyrene, which have a harsher impact on the environment [1].

Keeping It in the Region

From everything I have read about polyurethane, it seems that each region’s PU market is quite isolated, which there being no real global market flow. Since the material is a building block to other things, PU that’s made in the US stays within the country and is used by other industries in the country. Similarly, for China or India… any polyurethane made in these places is kept in these countries and used by these countries’ industries.

Some of the biggest components of polyurethanes are polyols and diisocyanates, and looking into these materials, it is clear that the production of these is also the highest in regions with most PU production, such as the Asia-Pacific region, confirming the lack of movement and transportation of this industry.

Memory foam is a little different since there is a much smaller market of these outside of the US where the technology has either not spread significantly or has been rejected, such as the case in India, where hard mattresses are still preferred. In any case, the memory foam industry doesn’t spill over to any other country. According to a study by Menon, “companies collect raw materials from small processing units or through dealers” and combine them to make mattress [8].

Use Polyurethane, Save the Planet

According to research and several studies, polyurethane is actually the best bet for the environment. Reports on manufacturing emissions has showed that the air, water, blood samples, etc. around areas with PU manufacturing plans have shown a less than 1 part per trillion concentration of harmful toxins such as toluene diisocyanate (a large component of PU).

Lately, instead of dumping polyurethane, many companies are taking it further and using PU scrap + other recovered material to create things like carpet cushions [9]. This has reduced the amount of waste produced and increased the lifespan of carpets such that PU is now considered a highly sustainable material for use in any industry.

Future plans for this material, which can be extended to memory foam, include things like reducing emissions in terms of the manufacturing process by using renewable resources as building blocks. Succinic acid is a component of polyurethane (that makes the polyols), which has typically been made with petrochemicals, however, there is a new bio-succinic acid available that will reduce the greenhouse gas emissions of this material by 94% [10] as suggested by Myriant (fig. 4).

Capture
Figure 4: Carbon Emissions of PU Precursors

In Germany, there has been significant advances in producing PU by using captured CO2 resulting in lower emissions and and lower use of fossil fuels (fig. 5). While the team has figured out a way to include a maximum amount of CO2 into the production process of PU, this maximum is far from reachable due to a need for hydrogen for CO2 capture [11]. This hydrogen making process needs to be optimized such that the emission levels can be successfully reduced for polyurethanes, and in turn, memory foam.

Capture
Figure 5: Production of PU through new CO2 Method

While it is quite clear that the production of polyurethane and its uses in memory foam, and minimally problematic, there is room for improvement and as the world demand for both of these rise, the focus on PU research is important in order to keep the material safe for both people and the environment.

Citations

[1] Gopal, Madan. Global Polyurethanes Market Segmented by Application, Industry and Geography Trends and Forecasts (2015 – 2020). Rep. no. 3311742. Hyderabad: Mordor Intelligence LLP, 2015. Jan 2016. Report Buyer. Web. 29 Feb. 2016.
[2] Smith, Sarah, ed. Memory Foam Mattress Market in the US 2015-2019. Rep. no. 1622381. London: Infiniti Research Limited, 2015. Print.
[3] Gottfried, Miriam. “Sex or Sleep?” Barron’s Cover. Barron’s, 14 May 2012. Web. 29 Feb. 2016.
[4] Global Mattress Market Size, Share, Development, Growth and Demand Forecast to 2020. Rep. New York: P&S Market Research, 2015. Print.
[5] Dige, Pramod. Spray Polyurethane Foam (Open Cell, Closed Cell and Others) Market for Residential Walls, Residential Roofing, Commercial Walls, Commercial Roofing and Other Applications – Global Industry Analysis, Size, Share, Growth, Trends and Forecast, 2013 – 2019. Rep. no. MRS-37622. Transparency, May 2015. Web. 29 Feb. 2016.
[6] “Asia-Pacific Demand to Drive Polyurethanes Industry Growth.”Markets and Markets News Update. MarketsandMarkets, 2 Aug. 2011. Web. 29 Feb. 2016.
[7] Bio-Based Polyurethane (PU) Market Analysis By Product (Rigid Foams, Flexible Foams, CASE), By End-Use (Furniture & Interiors, Construction, Automotive, Footwear) And Segment Forecasts To 2020. Rep. no. 978-1-68038-306-5. San Francisco: Grand View Research, 2015. Print.
[8] Menon, Hima C. “Trends And Out Look For Sleep Mattress Industry In India.”Indian Journal of Applied Research November 5.11 (2015): 349-51. Indian Journal of Applied Research. World Wide Journals, Nov. 2015. Web. 29 Feb. 2016.
[9] “Flexible Polyurethane Foam Industry Is Proactive on Sustainablity.” In TouchFebruary 14.1 (2011). Print.
[10] Myriant Corporation. Polyurethanes: The Case for Renewable Succinic Acid Based Polyester Polyols. Myriant Media. Myriant Corporation, 30 May 2013. Web. 29 Feb. 2016.
[11] Assen, Niklas Von Der, André Sternberg, Arne Kätelhön, and André Bardow. “Environmental Potential of Carbon Dioxide Utilization in the Polyurethane Supply Chain.” Faraday Discuss. 183 (2015): 291-307. Royal Society of Chemistry. Web. 29 Feb. 2016

Take away my mattress, not my polyurethane!

Running out of Rubber

Polyurethanes (PU) first came about during the second World War and was rapidly adopted by masses due to their wide-scale applications. Dr. Otto Bayer invented the diisocyanate polyaddition process in 1937 in order to create a replacement for rubber, which was at the time a scarce resource due to all its applications in war products such as gas masks, weaponry, and wheels for tanks/airplanes (fig. 1).

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Figure 1: Rubber rationing in WWII

By the end of the war, the uses of PU had become more widespread with industrial scale manufacturing of PU reinforced coatings, adhesives, and foams. The polyurethane that we know today really came to be in the late 50s when its uses as flexible foams was realized. By mixing this material with other chemicals and polymers, it was observed that PU’s thermal stability and rigidity were the two things that people have been looking for to create high performance insulation. As the properties of the material were improved, PU became increasingly customizable and the applications of the material spread over several industries from coatings to insulation to the entire automotive industry.

One Giant Leap for Polyurethane

Thus far, I have addressed the history of polyurethane as a whole, but this blog is really about memory foam and the powerhouse behind this particular use of PU is NASA. In the 1960s, during the golden age of manned spacecrafts, the comfort of astronauts was a big concern. The chemists at the Ames Research Center were tasked with creating a material for space shuttle chairs that would provide support but also be adequately cushioned so that astronauts would not feel the pressure generated by the gravitational forces during lift-off. This led to the creation of memory foam – a polyurethane foam that softened as it absorbed additional body heat and pressure and redistributed this weight. The material was then able to return to its original shape when the pressure was removed.

Though NASA never ended up using this technology, a foam company in Sweden took over the concept and the first pressure-relieving mattress was born in the 1990s. Due to the success of this product, many other foam manufacturers started producing visco-elastic PU mattresses and is now a major challenger to the more traditional spring mattress.

Can We Resist Polyurethane?

Over the years, it has become clear that polyurethane is a material that’s here to stay and we have definitely become dependent on it. This dependence was a result of the plethora of uses for the material due to its wide array of useful properties including corrosion resistance, durability, light weight, strength, and insulating ability.

One of the main contributors to this dependence is the positive effects of PU on the environment. With its enhanced structural and insulating properties, the durability and  energy efficiency of buildings can be highly improved leading to lower use of raw materials and overall energy consumption. About 45% of fossil fuel usage comes from heating and cooling buildings and with PU insulation, this number can be significantly reduced (fig. 2).

PU-pic1
Figure 2: Energy Considerations from using Polyurethane in Buildings

The issues surrounding this dependence arise from the problems I addressed in my previous post. Manufacturing PU can be a dangerous process since it involves chemicals like diisocyanates, fluorocarbons, and polyols. These chemicals are not good for health with fluorocarbons being carcinogens and greenhouse gases. The disposal of these products at the end of their lifetime also remains a concern since PU takes a long time to decompose if simply thrown into a landfill and produces poisonous gases when incinerated. Additionally, it is important to remember that polyurethane is an oil based product, which is a finite resource and this reliance on PU material could have drastic effects when this oil stops being readily available. As it stands, however, removing PU from the human sphere is an impossibility since the reliance is so high on this material for use in buildings, coatings, etc. The best we can hope for is sustainable production and use such that polyurethanes are available to us for many years to come, by which time we can hope to have found an alternative with as much flexibility in terms of material properties.

The dependence on PU is further observed in the amount of resources that are used to try and find alternatives to the manufacturing process, such that the harmful effects of fluorocarbons can be reduced while the polymer continues to be produced.

To address these issues, the American Chemical Society has been tasked with finding ways of recycling the material and has reported some progress in this domain with the emergence of both physical and chemical recycling plants for the material in question. However, due to the high cost and labor requirements for both of these types of recycling, the most common method of “disposing” this material has become energy recovery. European companies such as EUROPUR is looking further into recycling the material (fig. 3) through gasification and turning the material back into raw chemical materials for reuse.

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Figure 3: Recycling and Recovery of Polyurethane

 

Sleep Luxurious Sleep

While polyurethanes are definitely a necessity in the world today, memory foam mattresses are still considered a luxury. Many people would consider the product to be unnecessary since spring mattresses are still readily available and apart from the comfort factor, there isn’t much separating the two types.

Since their emergence in the market, they have become more and more popular as the world moves into the technology age causing an increase in back pains and back problems. As such, sleep is really the only time when we are completely free of tech and thus it is the only time people have to recover and let their bodies rest. This has caused the requirement that sleep become more comfortable and memory foam seems to the what people are turning to. As the amount people are willing to spend on mattresses rises (mostly due to the aging of baby boomers who have money), more people are investing in this luxury but as a society, we are far from becoming dependent on memory foam mattresses and if this was removed from the human sphere, I doubt there would be dire consequences.

Another thing that’s important to note is that as people complain more about the visco-elastic foam (a.k.a polyurethane), there is a focus on creating such mattresses from things like latex or introducing gel beads into the mix in order to further alleviate pressure from people’s bodies during sleep. Soon, we may move away from the typical polyurethane based memory foam altogether as new materials come to light, but PU will continue to serve other industries since it’s not just the foam aspect that’s important about this material.

Additional Information

chem2
Polyurethane Polymerization

 

Citations

Colby, Anne. “Memory Foam Mattress? That’s so Last Night.” Los Angeles Times. Los Angeles Times, 03 May 2007. Web. 09 Feb. 2016.

“Environmental Responsibility.” Polyurethanes in. European Isocyanate Producers Association Journal, n.d. Web. 09 Feb. 2016.

EuroPur. “Recycling and Recovering Polyurethanes Options in Practise.” European Isocyanate Producers Association Journal (November 2005). Web.

“History of Polyurethanes.” Polyurethanes. American Chemistry Council, 2016. Web. 9 Feb. 2016.

“History of Memory Foam.” BedInABox Mattresses. BedInABox, 2016. Web. 09 Feb. 2016.

One Voice, EUROPUR, and BING. “Polyurethanes: Sustainable Materials.”European Isocyanate Producers Association Journal – 11-98-ENV-0039-Fact Sheet (n.d.). Web.

Yang, Wenqing, Qingyin Dong, Shili Liu, Henghua Xie, Lili Liu, and Jinhui Li. “Recycling and Disposal Methods for Polyurethane Foam Wastes.” Procedia Environmental Sciences 16 (2012): 167-75. Web.

Problem Identification

Over the past few decades, memory foam mattresses have increased in popularity throughout the United States. These mattresses are made of polyurethane with some added chemicals that can change the density or viscosity of the material. There has also been developments into gel-based memory foam mattresses, but this blog will stick to the regular polyurethane mattresses that claim to improve sleep for the world over.

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Pain Database Memory Foam

Polyurethane is a thermoset polymer that doesn’t melt upon heating. This material is densified in order to make memory foam mattresses denser than normal foam, increasing their firmness, providing additional support during sleep. The claims are that memory foam mattresses distribute body weight better and reduce a person’s restlessness.

Production of this material has an effect on the commons, since there are Hazardous Air Pollutants (HAPs) emitted during the manufacturing of polyurethane foams. Toxins such as methyl chloroform and toluene diisocyanate are among these HAPs creating the need for a limit on production by the United States Environmental Protection Agency (EPA).

A lot of materials used during production has to be disposed of in special containers following strict guidelines. Disposal is therefore extremely important when considering these materials. Waste from polyurethane production falls into the categories of flammable, corrosive, reactive, and toxic; as such, all of these materials have to be separated and put into their individual disposal units, which can be an arduous task that the manufacturers have to take responsibility for.

Alongside the problems for the environment or the commons, there have been many reported problems that consumers of memory foam mattresses have faced. The first of these would have to be how flammable the material is, which poses a health risk. Polyurethane is a petroleum based product so there could be toxic implications in terms of how it affects your respiratory or skin-contact systems. Other issues are related to temperature since the cold reduces the ability of foams to compress and adjust to the weight of a person – cold temperatures also reduce the ability of the foam to return to original shape making recovery slow. Finally, a lot of the times, it has been noted that the foam keeps heat in, making sleepers hot and uncomfortable. This is something that newer mattresses are addressing but it is still an issue for the market to deal with.

Overall, however, even with these problems, the market for memory foam mattresses is definitely growing with people accepting the claims of better sleep more and more as the years go by and technology gets better. This increase in the market could have implications for the commons, which I’ll try to address in future posts.

 

Citations

“Guidelines for the Responsible Disposal of Wastes and Containers from Polyurethane Processing.”Center for Polyurethanes Industry AX151 (2014): 1-10.

“Memory Foam.” Wikipedia. Wikimedia Foundation, n.d. Web. 19 Jan. 2016

“Polyurethane.” Wikipedia. Wikimedia Foundation, n.d. Web. 19 Jan. 2016

“Top Ten Problems with Memory Foam.” STL Beds. 28 Jan. 2008. Web. 19 Jan. 2016