Viscoelastic Foam Mattresses: Marketing Hype Or Molecular Miracle?
Total Page：16
File Type：pdf, Size：1020Kb
viscoelastic foam Urethanes Technology: vol. 18, no. 6: December 2001/January 2002: page 22 · © Crain Communications 2001 Viscoelastic foam mattresses: marketing hype or molecular miracle? By Liz White, UT Contributing Editor the foam’s temperature sensitivity, “this is tics and conforms to body shape.” Most the key active property of viscoelastic flexible foams are “more lively, highly re- n the last decade, a new type of flexible foam,” Hackett added. silient and bouncy,” explained Stan foam—commonly called ‘viscoelastic’ Slow recovery is an obvious feature, Hager, research fellow in Bayer Corp.’s Ior ‘slow’ foam—has achieved a high used in marketing the material. If you sink polyurethane division. Hager has been profile in the mattress market. your hand into viscoelastic foam, it leaves working on viscoelastic foams for some Its marketing might lead you to believe an indentation which disappears only years now, with Union Carbide, Arco that this is a magic material with quite gradually (see pic). Chemical and Bayer. amazing properties (see Tempur World “Conventional HR [high Viscoelastic foams, “become more box, below). resilience] foams are two- lively as you heat them up—they all have But for once, the dimensional (density and this to some degree or other,” Hager said. claims for the materials hardness can be varied); vis- Jacob Boelskifte, quality and develop- are not just marketing coelastic foams are four di- ment manager at Dan-Foam A/S, de- hype: as Paul Bergad, mensional, with hardness, scribed viscoelastic foam as a slow recov- managing director of density, temperature and ery, rather soft, but supportive foam, US mattress maker time effects,” said Denis which is also temperature sensitive in its Bergad Inc. explained, Hicks, slabstock technology indentation hardness. “What excited us most manager with Huntsman The low indentation hardness (IFD) of [about viscoelastic Polyurethanes, based at these foams allows the body to sink foam] was that it had bene- Slow to recover—and Everberg in Belgium. “rather deeply” into the foam, while still fits as well as a story.” heat sensitive. Most foam experts listed maintaining the firm feel of a good quali- Anybody can promote a product well, similar key properties: “The novelty is ty resilient foam, Boelskifte said. Bergad said, but it is different when the that it has very slow recovery characteris- Viscoelastic foam is formulated to give product has major advantages over com- peting materials—as viscoelastic foams Medical benefits very rapidly, he said. have in health features (see box right). Hackett made similar points about design “Within five years, every hospital mattress of wheelchair pads. Sophisticated pressure- High damping will be made out of visco foam,” Hackett mapping techniques are used to assess the said. It has great benefit in stopping develop- “A key feature of ‘visco’ foam is that it is problem, with the same aim—of keeping the ment of bedsores, saving nurses and carers maximum pressure below a critical point. lazy or slow, with high damping. One of its a lot of hard work and time, he said. The principle for wheelchairs is the same main characteristics is very low resilience, Conventional HR foam mattresses cause as for beds—“to spread the load, to lower there is no spring in it,” said Padraig Hack- pressure on specific parts of the body— pressure at any given point,” Hackett said. ett, technical director at Irish foamer Kay- shoulder blades, buttocks, heels. Viscoelas- Hicks added that viscoelastic foams are foam Woolfson, based in Dublin. tic foam acts more like a viscous material at breathable, so they allow moisture to dissi- But by far the more important quality is these points, under the influence of heat pate, which is good for arthritic conditions from the body. So it softens and flows and for reducing skin irritation. They are also around these pressure points, Boelskifte usually medicated so that they have antibac- Foam-tastic! said. This spreads the load over a much terial properties. wider area, avoiding the pressure spikes that Other solutions to bed sores are generally “Visco-Elastic Memory Foam is a revolution- can cause decubitus ulcers, commonly more expensive, said Hackett, listing “ac- ary open cell space-age foam ... developed known as bed sores, he explained. tive” mechanised beds, complex air beds, for NASA in the early 60s. So unique are its Kayfoam data confirms this: compared and highly sophisticated water beds, used in properties that it continually adjusts and with regular pressure reducing mattresses, burns units. moulds to the weight and shape of your body viscoelastic foams give a far greater area of Viscoelastic foam mattresses can also be …itdramatically minimises pressure points, surface contact for a supine patient, with a used for burns units, to minimise pressure, thus reducing tossing and turning, signifi- contact area for the head, back, buttocks and Hicks said. cantly improving circulation, noticeably re- feet of 1872cm2 as opposed to 902cm2, ac- Sufferers from back and joint pain and ducing pain and discomfort associated with cording to Kayfoam literature. This reduces restless sleepers may also gain relief using disruptive sleep.“—US internet supplier Oh average pressure to around 15 mmHg from viscoelastic mattresses, the literature My Ach’n Back. (www.swedishfoam.com) nearly 30 mmHg with the regular product, claims. The foam supports the whole body, the firm says. while keeping the spine aligned (below). UT “The Future Is Here— … new space age Viscoelastic pads are technology … an extremely high density Tempur World also a bonus during visco-elastic foam which moulds to every surgery, because blood curve of the body… completely eliminates flow problems can occur localised pressure … at the hips, arms, and when patients are immo- shoulders [which] results in impaired circu- bilised, said Paul Bergad, lation and numbness, stiffness or pain. you managing director of US will experience tension-free sleep which is mattress maker Bergad vital to good health.”—Sleepyzzz, a US sup- Inc. Breakdown of tissue plier of foam products made by Knoxville- leading to ulcers can occur Tennessee based Knox Foam Corp. UT 22 URETHANES TECHNOLOGY DECEMBER 2001 / JANUARY 2002 viscoelastic foam Urethanes Technology: vol. 18, no. 6: December 2001/January 2002: page 24 · © Crain Communications 2001 a certain low resilience and hardness at Materials for VE foam gives “taller blocks, good shape and very 20°C. If the temperature drops, the foam commercial properties,” Hicks commented, gets very hard, “like a piece of wood,” British Vita’s viscoelastic foams “use a blend adding that the fast cure of MDI systems is Hackett said. “If you want to see if a piece of polyols, one a high hydroxyl value polyol, also of benefit this is kind of typical for most suppliers,” of foam is genuinely viscoelastic, put it in The Huntsman specialist added that, “con- said Ken Hillier, chief technologist with Mid- trol of foaming needs to be very precise, we the freezer, to see if it hardens,” he com- dleton, Manchester-headquartered foam mented. “Above about 30°C, the foam stick it on the line and optimise it for them.” maker British Vita plc. Dan-Foam uses a specially developed poly- gets softer and this temperature depen- One approach is to “try to have two phases ether polyol and TDI, and fine-tuned the in the polyol, each with a different tempera- dence is the reason the foam is used in ap- recipes with silicone stabilisers to optimise ture response; depending on how well the plications like hospital beds,” he said. processing in the early days, Boelskifte said. phases are mixed and the nature of the transi- With a standard flexible furniture foam, Foam index is normally below 100, he added. tion, you can get fast or slow change and tem- a hardness (IFD) of 20 at room tempera- Polymer systems for Dan-Foam’s Tempur ture will be the same if the temperature is perature response,” said Hicks of Huntsman. There are various routes to such polyols, materials are basically the “same raw mate- raised to 30°C or if it is dropped to 0°C, “a lot of know-how, but, because there are rials produced at different indexes,” which is Hackett said. For normal flexible PU many ways of doing this and there are a lot how the glass transition temperature is al- foam, across the ambient temperature of patents, it takes a lot of care to avoid in- tered, Boelskifte said. range, IFD values are not temperature-de- fringements,” Hicks explained. Dan-Foam uses very similar materials for pendent, he stressed. Foamers can use MDI (methylene moulded viscoelastic foam, with minor varia- “Typical furniture foam has, say, 65 diphenyl diisocyanate or TDI (toluene diiso- tions to cover higher moulding temperatures percent resilience: you drop a steel ball cyanate) Hicks added. MDI seems better and to handle high pressure mixing, Boel- bearing on it from a metre and it rebounds than TDI on the production line, he said. It skifte said. UT 65 cm,” he commented stressed, but “will always be a niche.” Both Kayfoam and Dan-Foam feel the “On a piece of slow foam it will only A lot of foam manufacturers are using next major growth area for viscoelastic rebound 2 cm,” Hackett said, since, viscoelastic foam in some shape or form, foam is domestic bedding. “visco foam is very low resilience, it is observed Alvaro Vaselli, vice president of On the domestic side, there are a lot of dead, with no bounce.” A typical metal marketing and sales with Foamex Interna- mattresses now available “with a top 2 or sprung bed base will give perhaps 95 cm tional. It is a unique way to differentiate 3 inches of visco foam, giving a very rebound, he added.