In-Depth Primer~Latex and Visco Foam
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by Joe Tatulli
LATEX AND VISCO ELASTIC Memory Foams Are Hot Sellers;
Futon Mattresses Are Competing At The Top
When we presented our last report on state-of-the-art futon mattresses and futon mattress materials (Spring of 2001), we focused on comfort and the premium materials that were finding their way into our category. Latex foams and visco-elastic foams were available for bedding, but the marketing thrust and mainstream advent of these products was still in the future. Today, visco and latex products are at the vanguard of the market. Tempur-pedic, being the leading consumer brand, holds the number six slot in the Top 12 U.S. bedding producers as reported in Furniture Today (May 18, 2004) with $188 million in sales in 2003. Most mattress producers now have some latex and visco- elastic products in their lines.
We have attempted to visually present the properties of the two different foam products. The Visco cells (top) react to both weight and heat by slowly collapsing upon themselves. Visco’s cell’s low resilience (LR) properties minimize any tendency to push back into their former expanded state. The Latex and HR cells react to weight only and continue to push back with their high resilience (HR) properties. In layman’s terms, we would categorize Latex as firm and Visco as conforming.
The purpose of this article is to examine these new materials and how they are being used in today’s futon mattresses and give you some data that you can turn into sales tools for everyday use. Like many of today’s products in the sit and sleep industry, quality and what constitutes comfort are subjective. Our goal is to lay out the facts and leave the issues of quality and comfort for you to decide. That being said, these new materials, with their technological advantages, comfort levels and long life, are driving every mattress manufacturer, including the four “S”s, into the alternative or specialty sleep category.
What is latex foam?
Latex foam has been around in one form or another since the 1930s. Natural latex foam is a highly elastic and durable foam made from the sap or milk of rubber trees. The trees (there are several different types) are tapped, and the liquid latex is collected for use by many industries. Synthetic latex is a chemically formulated product made to imitate the properties of natural latex. To create cushions, pillows and mattresses, most manufacturers blend natural and synthetic latex to create the optimal mix, producing a product that is durable, comfortable and resilient.
In the first stage of production, natural and synthetic latex and other chemicals and conditioners are added together to form a liquid compound. Each manufacturer uses its own proprietary blending formula. After the compound is prepared, the mixture is poured into molds. Two very different processes are used to create the blocks or slabs used to make mattresses and pillows.
The Dunlop Process
The dunlop process starts by filling the mold to the very brim. As the mold is heated, the solid latex particles begin to cure, and the heavier particles fall to the bottom, making the bottom of the foam block more dense than the top.
The Talalay Process
The talalay process begins by pouring a measured amount of liquid latex into the mold and then sealing the lid of the mold. A vacuum is created inside the mold causing the latex to fill the entire inside of the mold with a consistent cell structure. The compound is then frozen to below 20° F, locking the cell structure of the foam. The mold is then heated to cure the foam, causing the latex particles to bond into a solid state. Upon completion of the curing process, the latex material is removed and cut to size. The talalay process is more precise and produces a more consistent product. Talalay latex is therefore considered the premium product on the market. Dunlop process foam is typically used as a base and talalay is typically used as the top or comfort layer.
Latex futon mattresses come in several different configurations ranging from 100% latex to combinations of latex toppers with polyurethane foam, cotton batting, polyester batting, and other natural and synthetic products. Because latex is essentially a natural product, its properties are fairly consistent. It is highly resilient, giving it a firm feel, and its texture is such that it feels soft and comfortable while offering great support.
The ideal foam for mattresses and seating will provide a soft-to-the-touch surface feel and deep-down firmness that does not bottom out.
Density is measured as the weight of a cubic foot of foam. Density is the single most important property for consideration by the foam buyer.
Indentation Load Deflection:
ILD or IFD is the foam industry’s unit of measurement to express a degree of firmness. Based upon a calculation that determines how much a 50-square-inch indenter must weigh to compress a four-inch thick piece of foam to three inches (known as the 25 percent ILD reading) and how much a 50-square-inch indenter must weigh to compress a four-inch thick piece of foam to 1.4 inches (known as the 65 percent ILD reading), the ideal ILD reading would be 25 to 40 pounds at 25 percent, and 45 to 100 pounds at 65 percent.
The comfort factor, or “support ratio,” is the ratio of the 25 percent to 65 percent ILD readings. A good comfort factor is between 1.8 and 3.5.
Resilience for foam is the measure of its springiness. It is measured by determining the percent rebound of a steel ball dropped from a height of three feet. Mattress foams should range from 40 percent to 70 percent resilience.
Other factors, like Compression Set, the permanent deformation of foam due to usage; Static Fatigue, the relative degree of softening over the product’s life; and Tensile Strength, the greatest stress in pounds per square inch that foam can bear without rupturing; are also considerations when purchasing foam for mattresses.
Editor’s note—This information was compiled by Bedding Magazine (now Bed Times) using materials supplied by several foam industry sources and the Society of the Plastics Industry (SPI). They give special thanks to North Carolina Foam Industries - Chuck Wittenaur, Dr. Bradley and NCFI’s Bulletin 201. FL
What is Visco-elastic or Memory foam?
Visco-elastic memory foam was originally developed in the early 1970s at NASA’s Ames Research Center. It was developed to relieve astronauts of the effects of the incredible G-forces experienced during liftoff. Tempur World began experiments in Sweden to perfect the NASA formula for consumer use in the early 1980s. After nearly a decade and millions of research dollars, the company introduced their perfected version: TEMPUR® pressure-relieving material. The revolutionary TEMPUR material has a higher density, is much more durable and is more responsive to temperature and weight than typical synthetic foams.
Like many words we use every day, visco-elastic contains elements of two different words. Visco comes from the word “vicous,” which means adhesive or sticky and having a ropy or glutinous consistency. Think “viscosity” in motor oil. This property explains the dense, flow-resistant consistency of this synthetic foam. “Elastic,” on the other hand, means returning to or capable of returning to an initial form or state after deformation. All visco-elastic foams claim to have the property of being able to conform to body shape in such a way that the foam becomes softer in warmer areas, where the body makes the most contact with the cushion surface, while remaining firmer in cooler areas, where less body contact is being made. Essentially, body heat and pressure are employed by the foam’s technology to give a high level of comfort and support.
The formula and process that makes the foam visco-elastic is a closely held trade secret, but, in essence, what makes this product so different from all other foam compounds is how it reacts to body weight and heat. Latex and HR (high resilience) polyurethane foam cells compress under weight and then push back, always trying to revert to their original shapes. Visco-elastic LR (low resilience) foam cells, on the other hand, react to body heat and weight by conforming, not just compressing, and by softening where body weight and pressure points require. In other words, where the hips press down on the foam, their weight pushes down the cells and they lose their memory, forgetting to push back and thereby relieving pressure (at that point). The heat of the body (at that point) softens or opens the cell structure, providing comfort in the same way. At the waist (just a few inches away), where there is much less weight and heat, the cells remain firmer, offering support that conforms to every body type in every situation. This molding property takes time to develop (two to three minutes). Be sure you explain this delay to your customers when they lie down on the visco products in your stores.
Life of the product
How long do these products last? “Last,” meaning how long will they continue to provide the comfort and support necessary for normal, everyday use? This issue is tough to resolve because marketing numbers from manufacturers come with disclaimers regarding brand names and other technical specifications that need to be part of the discussion. From what we have been able to gather, the highest quality blended latex foam can maintain its usefulness for 20 years or more. High density (3.5#pcf to 5#pcf) visco-elastic foams can last 10 years or more. The only issue with these numbers is that the products themselves have only been on the market for about 10 years. Product testing answers some of the questions but not all. Upholstery grade polyurethane foams (2.6#pcf and higher) can also last the industry best 10 years. Some configurations allow the best of both worlds (cost vs. product life) by strategically stacking different foams and fibers and encasing softer materials in firmer ones for optimal comfort and product life, but we’ll leave that discussion to the marketers, who I am sure will be calling to tell me I am all wet. Be sure to get the manufacturers spec when you order.
As consumers refinance and buy new homes, they are spending more time shopping and more money for their furniture and bedding. Aging baby boomers want comfort, and many have the cash to get what they want. This phenomenon has driven the prices of the typical innerspring mattress and other alternatives, including the futon mattress, to the highest they have ever been. After consulting with two of the industry’s key editors, I came up with these numbers for average price points for good, better, best and ultra premium in the traditional mattress trade:
||$499 to $599
||$599 to $799
||$799 to $999
||$1999 and up
Today’s high-end premium futon mattresses can run anywhere from $399 for a “good” model to $1500 and up for an “ultra” unit. Some companies produce organic or all-natural products that run even higher, upwards of $2400.
(Information contained in this article was compiled from several web sites and several other industry sources—Editor.)