Polyester, sometimes just called “poly,” is a long-chain polymer. According to the Federal Trade Commission, a polymer has to be at least 85% esters to be classified as polyester. There are several kinds of polyester, but the kind abbreviated PET is made into fabrics. PET is also the substance of plastic beverage bottles, which can be recycled into fabrics.
Polyester is made by reactions of alcohols and acids, usually derived from petroleum or coal. The initial reactions were discovered in the 1930s by W.H. Carothers, a DuPont chemist, who found that when carboxyl acid and alcohol were mixed they could produce fibers. Nylon was developed at the same time, so polyester was forgotten for a while. But in 1941, British chemists rediscovered the reactions and began producing polyester fibers. DuPont bought the rights in 1946 and began developing polyester for textiles.
Polyester (also called “poly”) began to be used in clothing in 1961 as Dacron. It was washable and wrinkle-free, needed no ironing, kept its color, and dried quickly. It could also be blended with natural fibers, such as cotton or wool, making them wrinkle-resistant and more durable. Poly-cotton is a commonly used fabric today. The ratio of polyester is usually between 15 and 65 percent.
Polyester and poly-cotton are frequently used in mattress covers. Of bedding manufacturers reviewed on Beds.Org, at least 33 use polyester or poly blends in their cover materials. At least one manufacturer, WJ Southard, refuses to use polyester.
Besides fabrics, filling and insulating material (also called “polyfill”) are made of polyester. Polyester fibers can be any shape the extrusion nozzle can be cut into, even hollow tubes. It can be heat set to any shape, such as crinkled. Tubular and crinkled fibers are highly insulating as well as filling. Several mattress manufacturers use polyfill, often in the quilting.
For now it appears that polyester is here to stay, blended with natural fibers or on its own. It offers desirable qualities at affordable cost. It is also easily recycled. It can be designed to have the characteristics of natural fibers, such as cotton, linen, wool or silk. It can also imitate the semi-synthetic fiber rayon (extracted wood cellulose). As to being a petroleum product, it may someday be made from plant-derived materials.
Box Spring (from US-Mattress)
A box spring is a sturdy frame–usually wood–on which springs are mounted. The frame and springs are covered in cloth, usually with padding on the top and a base pad on the bottom. According to the Merriam-Webster online dictionary, the first known use of the term “box spring” was in 1865. The term box spring is sometimes alternatively spelled box-spring. Making it one word, boxspring, is generally not acceptable.
Traditionally, the springs are metal. They may be coils or corrugated spring wires (repeated “S” curves). The purpose of a box spring is twofold: provide sturdy, resilient support for the mattress, and elevate the mattress to a convenient height. The box spring has some give, making it more resilient than the floor. This way it absorbs some of the shock when someone bounces into bed (or on the bed). This extends the life of the mattress. It also protects the floor.
There are a number of ways of attaching/inserting the springs in a box spring. For example, some companies, like Shifman, tie them eight ways. Some are just stapled to the frame and clipped to an upper grid. The amount of handwork going into making a box spring partially determines its cost. Also factoring into the cost are the gauge of the spring wire and the metal used, as well as materials for the cover and padding.
It is also easier for most people to get into bed when the sleeping surface is several inches off the floor. The standard height of a box spring is 8 to 9 inches. However, with higher mattresses now in the market, low profile box springs and foundations of 4 to 5½ inches are available.
Once the only foundation other than a bed frame, a box spring is now only one of the foundations available to mattress customers. Other foundations are platforms, wood slats, and adjustable beds. However, most retailers list foundations other than adjustable beds as box springs.
A European wood slat foundation can be legitimately considered a box spring. Instead of metal, the springs are slats of highly resilient wood. With the development of wooden coils, these may someday be found in box springs. Foundations filled with foam are called box springs by some firms.
Most manufacturers of mattresses make their own box springs. The box springs are designed to work with their mattresses. Therefore, the best box spring is the one that is sold with that mattress. Also, a box spring can wear out, just like a mattress (it can also be accidentally damaged in handling), so it is best to buy a new box spring for a new mattress.
 Ecyclopædia Britannica, Merriam-Webster, “box spring,” http://www.merriam-webster.com/dictionary/box%20spring, accessed 08/27/2014.
In Europe, the preferred foundations have several closely spaced slats made from a springy wood, such as beech. The resiliency of the wood makes the wood slat foundation absorb shock, much like a box spring. The springiness of wood can be felt walking over a wooden floor as opposed to a concrete surface.
Unlike the box spring, a wood slat foundation does not depend on metal, making it preferred by persons wary of the amplification of electromagnetic radiation (radio waves). This same motivation inspired the recent development of wood springs. Wood slat foundations are now being made and sold by mattress manufacturers in the United States, such as European Sleep Works (ESW). The “Flexible Slat System” made by ESW is adjustable so the users can make it customize the response.
There are bed frames using wood slats which do not qualify as European wood slat foundations because the slats are not close enough to each other. In other words, the gaps are too wide. With a slat foundation, if the slats are spaced closely enough they can be used for memory foam mattresses. They also provide better support for innerspring mattresses as well. No matter the kind of mattress you have, it needs adequate support to help support you, the user, and to extend the life of the mattress.
A wood bed frame with widely-spaced slats can very well elevate a foundation, but it cannot take the place of a well-designed, closely-spaced European wood slat foundation.
Consumers now occasionally see the terms “phase-change materials” or “PCM s” in descriptions of clothing or bedding. Each season, more manufacturers use PCMs in their products, some even making them a selling point. Even a casual reading tells us that phase-change materials have something to do with comfortable temperatures. More exactly, PCMs are used to keep temperatures within a desired range. But what are phase-change materials, and how do they work?
According to Wikipedia, “A phase-change material (PCM) is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy.” All materials absorb heat when they melt or vaporize and release heat when they condense or freeze, but not all materials qualify as PCMs. A phase-change material absorbs and/or releases large amount of energy in the process, remaining at the same temperature until the process is completed.
As a solid substance absorbs heat energy, it becomes warmer, eventually becoming hot enough to melt. Wax is a good example. We have all seen light wax becoming soft on a hot day. Only a little warmer and it reaches the melting point. As the wax melts, it absorbs heat from its surroundings. As it solidifies, it releases heat. When the air becomes cooler (or the source of heat is removed), the wax cools by releasing heat. Cool enough, it becomes solid again.
The most well known and longest used phase-change material is ice. A container of water will not fall below 32˚F (0˚C) until all the water is frozen, and that ice will not rise above 32˚F (0˚C) until completely melted. Ice is more efficient for keeping things cold than water is for keeping them from getting too cold; it takes 144 times more energy to melt 16 oz. of ice than to raise the temperature of 16 oz. of water by 1˚F. 
Large bodies of water have a moderating effect on nearby land, and ice is perfectly fine for keeping food and drinks cold, but it is too heavy, bulky and messy for controlling temperatures in mattresses and clothing. Lighter substances which are easier to handle are needed for this, as well as materials that can release enough heat at the lower end of the preferred temperature range.
In the 1970s and 1980s NASA wanted to protect instruments in spacecraft from extreme temperatures without using large amounts of energy to operate heating/cooling systems. The most feasible means was to use materials which would absorb or release large amounts of heat when needed, and phase-change materials were the ideal solution. PCMs were used on the SkyLab and space probes.
After this, NASA sought to apply this technology to spacesuits to protect astronauts on extravehicular excursions. Engineers at Triangle Research & Development in Triangle Research Park, NC, developed means of incorporating PCMs in textile fibers. Using this under license, Outlast Technologies is marketing fibers and fabrics to manufacturers and users of textiles, including bedding producers.
Phase-change materials used in textiles are generally in the form of microencapsulated gels or polymer chain links. Since many of these substances are irritants, the means of application depends on whether the user has body contact with the material with PCMs. With no skin contact, coating–which is the most efficient method–is used. Most of the phase-change materials used are polyolefins (waxes) whose melting points are in the desired ranges. Several PCMs are usually selected and balanced to narrow the effective temperature range to a comfort zone for sleeping.
Phase-change materials in mattresses and pillows are not restricted to the fabrics. For instance, a patent assigned to Sleep Innovations by inventor Walter Mackay is for a method of incorporating certain types of PCMs (“organic compounds of nonmetals other than C, H, O, and N”) into bedding foams.
The use of phase-change materials is one available choice when shopping for a mattress, pillows, or other bedding products. Whether you select a product with this feature depends on several considerations. Availability is no longer a major consideration since so many brands now incorporate PCMs into their mattresses
The first consideration is, “Will this really help me sleep better?” This depends on how temperature affects your sleep, which in turn depends on the ambient room temperature (how you use heating or air conditioning) and the composition of the mattress. Mattresses with foams, especially memory foam, tend to be warmer, sometimes too warm. If your bedroom tends to be too warm or too cool, or if the top layers of your mattress have memory foam, PCMs may be the solution to keeping cool.
The next consideration is cost. Phase-change materials are now so widely used that the cost is not as high. Some mattresses with PCMs, such as the Serenity Gel by Bed In A Box, are in the low-to medium price range.
The most important consideration–not to be forgotten–is, “Does this mattress meet my needs, regardless of whether or not it has PCMs?”
 “Phase-Change Materials,” Wikipedia, http://en.wikipedia.org/wiki/Phase-change_material.
 “Melting to Keep Cool,” PBS Nova, http://www.pbs.org/wgbh/nova/next/tech/melting-to-keep-cool/.
 Mansfield, Richard G., “Phase Change Materials,” Textile World, http://www.textileworld.com/Issues/2004/March/Features/Phase_Change_Materials.
 Patent Docs, http://www.faqs.org/patents/app/20120193572.
Many of us have heard of the Silk Road. The name conjures images of adventure, romance, luxury, wealth, conquest and intrigue. It was the route from China to India, Persia, Egypt and Europe by which silk was carried to market. In ancient times, China was known as the Land of Silk. That is where production of silk began some time before 3500 b.c. In fact, our word “silk” came from the Chinese word si. China is still the major producer of silk, producing about 3⅓ times as much as second place India.
Silk is a natural fiber, made by silkworms, the larvae of the Mulberry Moth (Bombyx mori) and a few other moths. The Mulberry Moth of China and the Ailanthus Moth (Samia Cynthia) of India are the only completely domesticated silk moths. The mature larvae spin cocoons to protect themselves in the pupa state (when they undergo metamorphosis, changing into adult moths). Silk is the thread that makes the cocoon. The cocoon is boiled to kill the pupa and loosen the thread, which is then unwound and reeled.
Silk is a smooth, shiny material. It is very strong, and exceptionally long fibers make it even stronger. It is also very fine. A single fiber is hard to see. Most silk threads are composed of several fibers. Silk textiles are strong and durable. They are used not only in clothing, but in parachutes, luggage, draperies and upholstery.
In bedding, silk has long been used in sheets and pillowcases. It is also used in cover fabrics for mattresses and foundations. Sometimes silk is the sole fiber in a mattress ticking or cover (as in the Natural Silk Elegance by BedInABox), but often it is blended with other fibers, such as wool (as in the World Luxury series by King Koil), bamboo (as in the Tempur-Contour Allura by Tempur-Pedic) or cashmere (as in Stearns & Foster’s Lux Estate and Lux Estate Hybrid collections).
Besides its strength, silk is a breathable fabric. It is also absorbent. The fibers wick moisture away to evaporate, keeping the surface of a mattress both dry and cool. Silk is also resistant to most acids, making it very durable. Silk has another benefit from a marketing standpoint. With the reputation of silk, just naming it among the component materials of a mattress lends a perception of luxury.
Bamboo is the only kind of grass listed in tree identification guides. It is the largest and tallest grass, growing to tree-size, and it is woody. Since ancient times in East Asia, bamboo has been an important building material. It has also been used for musical instruments, cooking and eating utensils, hats, mats, ship sails, and many other things, including fabrics. At least 27 manufacturers reviewed on Beds.Org use bamboo, mostly in cover fabrics.
Bamboo is touted as a “green” material, and the raw material itself qualifies. It requires no pesticides or fertilizers, grows quickly, does not need irrigation, and does not require replanting after being harvested. Bamboo’s root system actually stops soil erosion, and it filters ground water. It also takes a lot of CO2 out of the air.
Besides being “green,” bamboo is also naturally antimicrobial. Bamboo has a substance called kun, which inhibits the growth of bacteria and fungi.
While the bamboo plant is “green,” bamboo fabrics for clothing and mattresses is another thing. There are actually two kinds of fibers coming from bamboo. One is the natural fibers of the plant itself. The other is rayon.
Natural bamboo fibers are not easily obtained, as cotton is. The process of separating fibers from bamboo is similar to getting linen from flax. It involves crushing the bamboo, then rhetting (using enzymes or chemical agents to free the fibers), a process that is not cheap, especially for fine fibers. Bamboo fibers for textiles are also called “bamboo linen.”
A few mattress manufacturers use natural bamboo fibers. Most of these are in cover or ticking fabric. Some of these are blends with silk, cotton, polyester or rayon. Some fabrics are described as “bamboo-infused,” meaning that shorter bamboo fibers are spun with other fibers in the yarns used for the fabric.
Much of the bamboo used in fabrics is “reconstituted bamboo cellulose fiber,” better known as rayon, or “bamboo rayon.” The cellulose in the bamboo is dissolved into a viscose liquid, which is extruded through spinnerets then solidified into fibers, a process similar to making rayon from wood. The chemicals usually used are toxic, such as carbon disulfide and lye (caustic soda). Even though the bamboo itself is ecologically friendly, the manufacturing process for bamboo rayon is environmentally problematic.
The Federal Trade Commission in 2010 ruled on the eco-friendly claims for bamboo fabrics. Only fabrics made from bamboo pulp fibers can be called “bamboo” or “natural bamboo.” Since the only part of the bamboo plant that remains in rayon made from bamboo is the cellulose, it must be called “rayon.” This can be specified as “bamboo rayon” or “rayon from bamboo.” Also, “viscose” can be used for “rayon.” Therefore, the only ecological advantage of bamboo rayon over wood pulp rayon is the impact of the source plant.
Out of 27 manufacturers covered on Beds.Org who use bamboo, according to their own mattress descriptions, 15 use natural bamboo fibers, 4 use rayon, 2 use both, and with 6 the type of fiber is unspecified.
In conclusion, a mattress using fabrics made with natural bamboo fibers does have health and environmental benefits, such as being hypoallergenic, antimicrobial, breathable, and moisture wicking. Using the finer fibers adds the advantage of a soft, smooth cover. The primary advantage of bamboo rayon is the quality of the fabric itself: texture and durability.
Linen is one of the oldest plant fibers used by humans for clothing and bedding. Our word “linen” comes from linon, the Greek word for flax. It is made from fibers in the inner bark of flax stalks. These fibers are separated from the flax by a process called “retting.” In this process, micro-organisms or caustic agents eat away the softer parts. When the retted flax is crushed and washed, the fibers alone are left.
The cross-section of linen fibers is irregular. This makes the thickness of strands uneven, thicker in some places, thinner in others, creating “knots” in linen threads which show in woven fabric, what is called the “linen look.” In spite of this, the fabric is still smooth, strong and durable.
Linen is soft and breathable and wicks moisture away, keeping wearers cool in hot climates. In addition to being cool and smooth, linen is also lint-free. The more it is washed, the softer it becomes.
Flax was cultivated extensively in ancient times. Linen has been associated with purity, and was worn by priests of several religions, as well as by royalty and nobility, as we can see in Egyptian art. Because the production of linen is more detailed and longer, it is more expensive than most other fibers, such as cotton and wool. Therefore, even in recent times, linen cloth has been regarded as a higher-class fabric.
In the past 200 years, linen has been used for undergarments, nightclothes, fine shirts and blouses, etc. It has also been used for tablecloths, towels, sheets and pillowcases. Even today, with other fabrics being used, these items are still called “linens.”
Since mattresses were first made, those who could afford it preferred a linen ticking (or cover). This has been true since the development of modern mattresses in the 19th Century. Higher-class and more expensive mattresses are more likely to have linen coverings than the less expensive alternatives. Even with modern linen production methods, few models are linen-covered, such as Linen Experience by Magniflex, The Alameda and The Pittock by Parklane Mattresses, and Tempur-Choice Supreme and Tempur-Choice Luxe by Tempur-Pedic. And Stearns & Foster sells linen-covered foundations for their mattresses. Linen used to be mostly woven, but as a mattress cover fabric it is usually knit.
Sheets, pillowcases, blankets and quilts are collectively called linens. This does not mean that they all contain linen, but some do, especially higher-priced collections.
There are some advantages of linen as the cover fabric for a mattress. The first is its ability to quickly absorb water, then release it. This helps keep the sleeping surface of the mattress dry by absorbing perspiration. The moisture then evaporates, which cools the surface and the sleeper. Since linen is free of lint, it does not transfer lint to nightclothes.
Linen is more expensive than cotton and polyester, the two most common mattress cover fabrics. But if you can afford it, and you find a mattresses otherwise preferable which is linen-covered, it is worth considering.
The simplest definition of wool is hair grown by sheep. It now includes hair from several types of goats as well as llamas. Wool is one of the oldest fibers used by humans, and sheep are among the earliest domesticated animals. From the many breeds of sheep come many varieties of wool, offering many choices to mattress manufacturers and their customers.
Since the beginning of recorded history, wool has been used in clothing, blankets and tents. It was both woven and knitted. As far as we know, sleeping mats were first made with straw, but at some point, wool was used in these precursors of mattresses. Still, it was only one of the available choices.
Early mattresses were made using available materials for the ticking and for the fill: linen, straw, sawdust, moss, cotton, wool. Wool is still used today, not only as batting and as cover fabric, but also as the base pad on the bottom of the mattress and as a fire retardant in the quilting on the top and sides.
Wool has several benefits when used in mattresses. The most commonly known are temperature regulation and cushioning. As to temperature regulation, wool not only keeps us warm, it can also keep us cool. The texture of wool insulates the user. Wool clothing is able to keep a person warm even when it is wet. But wool can also cool. It is breathable, letting air circulate. It also wicks moisture, including perspiration, away from the body (or the sleeping surface). This not only dries the user, but evaporation has a cooling effect.
The structure of wool makes it a cushioning material. The strands are curly. In bulk, they act like organic springs, though not as strong as steel. One manufacturer, W. J. Southard, says they use a blend of wools from several sheep breeds. The wools are selected for “breed, color, strength and micron-width,” and are blended to maximize resiliency, the key to cushioning.
The lanolin in wool repels dust mites, a major carrier of allergens. Also, wool is a natural fire barrier, making chemical flame retardants unnecessary.
The kinds of wool used, as described by manufacturers, are Pashima, Joma, Mira, Merino, Angora, and lamb’s wool. Places this wool comes from are France, Germany, New Zealand, Australia, and the United States.
Some lines of mattresses, or individual models, are advertised as having “organic” wool. This is wool from sheep which have not been subjected to chemical baths (a.k.a. sheep dip), and which has not been treated with chemicals. Wool produced in the U.S. includes Eco-Wool. This wool meets the specifications for organic, but is from small ranches which cannot afford the cost of the certification process.
Wool is not used only for batting and pads. It is also used in the cover fabric of several mattresses. Usually this is in a blend, mostly with silk (another animal fiber). Often it is the quilting material.
At least 29 of the mattress manufacturers reviewed in our mattress reviews here on Beds.Org use wool in some of their models. However, there are other manufacturers, such as the Wool Bed Company, who make all-wool mattresses.
Infusion of bedding foams with gel was first used in Europe, and is now widely used in the United States. Gel infusion was first introduced to modify the support properties of the foam. Later it was promoted as making memory foam cooler.
Gel can be called a semi-solid. It is both solid and fluid. The International Union of Pure and Applied Chemistry defines it as this: “Gel: Nonfluid colloidal network or polymer network that is expanded throughout its whole volume by a fluid…A gel has a finite, usually rather small, yield stress.” A gel can be rigid or very soft. The fluid can be watery, oily or gaseous. The gels used in bedding foams are polyurethane/polyol gels (polyols are oily).
As said above, support modification was the first application of gel-infusion in memory foam. Gel increases support, especially under hips and shoulders. This does not degrade the conformity of the foam, so it still relieves pressure points. This way, gel enhances memory foam.
Gel has been promoted by mattress manufacturers for its cooling properties, but that has been questioned recently. According to some experts, the addition of gel, promotes open-cell formation, which allows air to circulate through the layer, and this is what cools the memory foam mattress. But open-cell foams can be made without gel. Gel does have an initial cooling effect. That lasts until the gel has reached its limit. But gel with open-cell structure is cooler than closed cell memory foams.
Not all gel in mattresses is infused into foam. A handful of models now have all-gel layers, usually the top one. A few manufacturers specialize in mattresses with gel top layers, for example Technogel Sleeping and Blue Chip Medical Products.
When shopping for a mattress, gel is one more feature you will see. Mattresses usually cost more with gel than without. Before you buy a model with gel, consider what you need and whether the gel foam or gel layer is worth it.
One of the common ingredients in mattresses and upholstered is polyurethane foam. In descriptions of mattresses, it is often called “poly foam.” With differing densities, resiliency and other characteristics, it can be a base pad, support core, comfort layer, or quilting foam. It was used before the invention of memory foam, which itself was developed from polyurethane.
Polyurethane (PU) foam is made by linking large molecules, usually isocyanates, to each other with modified oil molecules called polyols, usually petroleum-derived. Polyurethane can be solid or foam. The foam is very supportive, making it useful in cushions and mattresses.
Most of the issues with polyurethane foam are related to its manufacture. Isocyanates are toxic before becoming part of the PU foam. I used to work on a line making foam-filled panels for garage doors. Two liquids were injected between the sheet metal skins of the doors. They immediate blended and swelled into foam, which cured to become firm. One of the liquids was an isocyanate, and we had to be extremely cautious around it.
Another issue is outgassing. For some time after it is made, polyurethane releases gasses with an unpleasant odor. Careful selection of ingredients reduces the outgassing and the odor. Outgassing is also reduced if the foam is allowed to air out before being packaged for shipping.
Many mattress manufacturers use “plant-based” polyurethane foam. From 15% to 20% of the polyols in this foam are from plant-derived oils. At the current level of technology, no more plant oils can be used and still have a high quality polyurethane. With further research & development, this may change. The plant-based polyols used are most often from soy oil, but other hydrocarbons, such as coconut oil and palm oil, are sometimes used. Further technological development may see the use of many other plant oils.
One of the major manufacturers of polyurethane foam in the United States is FXI (formerly called Foamex). Foamex was the brand name of the first foam mattresses, made by Firestone. Those were foam rubber (latex), but polyurethane was later used for mattresses. However, much of the polyurethane used in mattresses is made in China.
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