Secrets Of Rubber Mats

Where would we be without rubber? Make all the jokes you want; rubber's indispensable stuff, especially in the barn. The tire on your wheelbarrow, the handle grip on your longe whip, your two-year-old's first snaffle bit, that flexible curry comb, the feed tubs and buckets in your stalls--chances are, they're made of rubber. But one of the most popular uses of rubber in the barn is underfoot. Rubber floor and stall mats reduce the chances of a horse slipping on a hard concrete or asphalt floor, or on a wet surface such as a wash rack. They help cushion his limbs when he has to stand for hours in a stall or a horse trailer. They make it more comfortable for him to lie down and rest. And they make cleaning stalls less of a chore, and ammonia fumes less of a problem.

Choosing to use rubber mats in your barn isn't the tough part. The tough part is choosing which ones are best for your purposes! Although at first glance they all seem to be basically the same--big, heavy slabs of black rubber--on closer inspection there are dozens of brands of rubber mats available, each with its own selection of features. Do you want a pebbled surface, or a smooth one? Flat bottoms, or grooved ones? Pure virgin rubber, 100% recycled, or mats with nylon fiber centers? Do you want mats with smooth edges, or ones that lock together like a jigsaw puzzle? Which of several different thicknesses is best? Which is softest, which is the most durable, which best handles extremes in temperature, which provides the best traction, and which is likely to fall apart with heavy use?

Who knew plain old rubber could be so complicated?

Let's have a look at rubber mats, with a focus on what's safest for your horse, and safest for the environment.

Manufacturing Secrets

Most of us think rubber comes from the rubber tree (Hevea brasiliensis, a native of South America)--and sometimes it does. But there are a vast array of synthetic rubbers that are widely used in industry. Of these, styrene-butadiene rubber, or SBR, is by far the most common, and makes up most of the rubber products we encounter every day, including the majority of car and truck tires.

Natural rubber is a renewable, sustainable resource, and as such, it's quite environmentally friendly--it even will degrade in the environment (through oxidation and/or microbiological attack) if given enough time. But the manufacture of synthetic rubbers also has a minimal impact on the environment, according to Johnny Singleton, sales and quality manager of Summit Rubber in Summerville, S.C. (manufacturers of E-Z Rider Equine Stall Mats). "SBR is cheaper than natural rubber," he explains, "and it's quite abrasion-resistant, which is a plus. And it has no detrimental environmental impact that I know of." Many rubber items, he notes, are made of a combination of natural rubber and SBR, each of which contributes some qualities to the finished product.

In its natural form, both natural and synthetic rubbers form a plastic-like mass. In order to be converted to the familiar solid, but resilient form we recognize, it needs to be "vulcanized," which is a chemical process that encourages cross-links in the complex rubber molecules so that they can stretch and give without breaking. There are a number of different "vulcanizing agents," but the most common is elemental sulfur, which is usually combined with an "accelerator" chemical to speed the process along, and an "activator" made up of zinc oxide and stearic acid. The exact ratio of sulfur to accelerator will determine the final product's number of cross-links, and thus its flexibility, its durability, and its thermal stability.

Each company has its own special recipe. The sulfur and other chemicals generally are added to the raw rubber, then activated by applying heat. (New stall mats will sometimes have a "rotten egg" smell, which is a by-product of the sulfur bonding system; the odor usually fades in a few days.)

Vulcanization, Singleton points out, is an irreversible process, despite the fact that many companies that make recycled mats describe their products as "revulcanized."

Kelly Arnold, agri-business division manager of RB Rubber Products (manufacturers of Tenderfoot Stall Mats), agrees. "(Revulcanization) would be like crumbling a cookie, mixing the crumbs with milk, and trying to restore it to its original state," she says. "You can't really go back to the 'dough' stage."

When rubber is recycled, as it often is for stall mats, the rubber is broken down into crumbs and persuaded to bond by one of two methods. What's called "revulcanization" is really the application of heat and extreme pressure to the rubber crumbs, which activates its remaining "cure factor" (the qualities in the rubber that allow it to form cross-links) and helps press it into a new shape. More sulfur usually is added during this process, and some companies use the term "sulfur-cured" rather than "revulcanized."

The other method is to bond the rubber crumbs together with a urethane compound (essentially, glue). These "bound" mats also are heated and pressed into shapes, but don't require the extreme pressure that revulcanized mats do. RB Rubber, which produces its Tenderfoot mats by this method, switched to the process from revulcanizing (which it used up until 1995) because the company thought that it produced a softer, more elastic mat that maintained its integrity better under hard use.

"The revulcanization process is superficial," notes Arnold. "It only penetrates to a certain depth; really, it acts as a top-dressing for the rubber, bonding the top layer (of crumbs), but not necessarily going all the way through the mat. The thicker the mat is, the more this is a problem. Once you get under the 'skin,' you may find the interior is brittle and won't stand up.

"Another problem is that unless the rubber crumbs are heat-dried before they're revulcanized--and not every company does this--moisture may get into the mixture and you'll end up with air pockets in the center of the mat, like a piece of pita bread. So you're not really getting the thickness or the durability you've been promised."

In contrast, she says, mixing the rubber crumbs with urethane allows each particle to be thoroughly coated with the bonding agent, producing a more solid seal that goes all the way through the mat. Using another baking analogy, Arnold notes, "The urethane is like the egg in a cake mix. It's the liquid element that binds it all together. What cure factor is left in the rubber will help, too, but we don't rely on that (for bonding). The result is a chemical bond which has elasticity and maintains its integrity."

Singleton mentioned another disadvantage of revulcanized mats is that they might absorb a small amount of moisture, in contrast to virgin rubber mats, which basically are impermeable to liquid. "It's only about 2% to 3% of the weight of the mat, but in a 100-pound mat it can be significant. In a stall, for instance, that mat may absorb two to three pounds of urine and other unspeakable stuff."

On the other hand, revulcanized mats are quite cost-effective (especially in comparison with virgin rubber mats), and might have the edge over urethane-bound mats when it comes to heat and cold resistance.

"Some urethane mats," says Singleton, "can get soft and may even tear when the temperature goes above 80°F. They can also crack in extremely cold weather."

Because revulcanized mats tend to have a harder texture than urethane-bound ones, they also might have slightly superior abrasion resistance (something to keep in mind if you're placing one under a stall door or a gate).

Key to a quality urethane-bound mat, says Arnold, is the size of the rubber crumbs. The smaller the crumbs, the more thoroughly they will be coated with the urethane, and the more strongly they will bond. "Consumers should look at the particle size," she says. "Smaller is definitely better."

Looking at the edge of the mat, and gently scraping it with a key or your fingernail, should give you an idea of the size of the crumbs; it's normal for a little of the excess to break away when the mat is new, Arnold notes, and not an indication that the mat is going to disintegrate.

New Or Used?

Although the idea of recycling old tires, gaskets, fan belts, and other products to make stall mats sounds like environmentally sound thinking, it's not without its difficulties. Singleton confirms, "The rubber business hasn't caught up with the plastics trade in terms of recycling. Plastics can be 100% recycled now, but at the moment, we can't get the same quality of rubber in a recycled product as in a new one."

The biggest problem with recycled rubber is that it often contains foreign materials, particularly metals. Steel-belted tires are a primary source of recycled rubber, and the metal impregnated in each one can be extremely difficult to remove. Copper and aluminum also turn up in recycled rubber crumb, and won't be picked up by magnets. Scrupulous companies go to great pains to make sure that metal fragments are removed before they rebind the rubber, but that triple- or quadruple-cleaning adds considerably to the expense of the process. Not only is a rubber mat contaminated with metal fragments a safety hazard (the sharp pieces can work their way to the surface where they could injure a horse), it can also make the mat conductive to electricity--something people don't expect when they're standing on a sheet of rubber! An owner standing on a damp rubber mat, wielding a pair of electric clippers, might assume she's protected, when in fact she could be setting herself (and her horse) up for a shock. It's for this reason that Singleton feels mats made of 100% virgin, not recycled, rubber, are a safer choice. "Our product is more expensive, but the virgin rubber is worth every penny, in my opinion," he says.

There's also the issue of contamination to consider. It's possible for recycled rubber to be sourced from landfills and disposal sites, where it might have been soaking in toxic chemicals. How many of these poisons survive the revulcanization or urethane-binding process is hard to say. Reputable companies will source their rubber only from "clean" tires--trade-ins or those which didn't pass the final inspection at the plant--and from scrap left over in the process of making gaskets, fan belts, innertubes, or whatever. But at the consumer level, there's really no way to detect where that recycled rubber came from.

If you live in a manufacturing center, you might find it relatively easy to get your hands on old conveyor belts, which can be used for stall and aisle mats. Often the stuff is given away for free. But before you install conveyor belting in your barn, consider the factory it came from--it could be contaminated by chemicals to which you'd rather not expose your horse. Rubber belting is also reinforced by tough nylon or rayon fibers, as a rule, and these fibers tend not to expand and contract with fluctuating temperatures as well as the rubber they inhabit. The end result is a mat that curls up at the edges and causes a tripping hazard, or allows liquids to seep underneath.

Other Considerations

Rubber mats installed on stall floors can save mucking time and bedding, and cushion a hard, unyielding concrete or asphalt floor. If your floors are dirt or clay, stall mats can help reduce the ammonia fumes and bacteria and mold growth caused by urine and manure soaking into the floor. In either case, the idea is to keep liquids on top of the mats, where the bedding can absorb them. When you muck the stall daily, you're then able to remove virtually 100% of the urine and keep the stall fresher and more hygienic.

But installing stall mats isn't an easy chore. First, the floor must be level--which might take hours of labor and many wheelbarrows of gravel and stonedust if you're dealing with old stalls full of holes. Even if you have a pristine concrete surface, you're going to need help: rubber mats are heavy. Although at first glance it might sound like a good idea to eliminate seams and gaps by blanketing a stall with a large, one-piece mat, such a chunk of rubber might take six strong men and a Clydesdale just to budge! If you're short on help, choosing mats that are smaller is a good idea (an average three foot by four foot mat weighs approximately 100 pounds, and a six foot by 12 foot mat weighs more than 250 pounds, as a guideline). Attaching "C" clamps to the edges can help you drag and maneuver the mats a little more easily.

Arnold points out that it's not necessary to have the mats line up exactly next to each other; a quarter- to a half-inch of space between each section will allow for expansion and contraction with the weather, and bedding will tend to pack down into the cracks and form an effective "caulk" so liquid can't seep through. It's a good idea, though, not to have any seams near the door, where your horse might paw up the edges. (Some stall mat manufacturers supply detailed instructions on how to prepare a stall floor, carry and maneuver the mats, and cut them to size--so if you're haven't done this before, ask for manufacturers' instructions.)

Grooves on the bottom surface of the mat are supposed to help let any liquid that sneaks underneath evaporate without a buildup of mold or bacteria. But Arnold points out that unless all of the grooves are perfectly lined up across the length of the stall, they'll do little good. And if they are placed on a dirt or stone-dust floor, the grooves simply will fill with the flooring material.

"The whole benefit of mats," she says, "is supposed to be 100% water-proofing, so to me (grooves) are an oxymoron!"

Grooves tend to cut down on the weight and the manufacturing costs (they save on the amount of rubber used), and some companies claim they increase the overall resilience of the mat, thus reducing shrinkage and curling. However, Singleton points out that a mat is only as durable as its weakest (thinnest) point, and there's little evidence that grooves keep mats from sliding around; that's usually accomplished by the natural "tacky" quality of the rubber.

Also, textured surfaces might not really contribute anything useful to the surface of a rubber mat. "Textures look really nice, but they shouldn't be necessary if the rubber is of the right consistency," says Singleton.

Arnold points out that a textured surface can make the mat difficult to sweep if you're using it in an aisleway or wash rack. She agrees textures don't add to the traction a mat provides. "A mat won't be slippery unless it's hard and brittle," she says. Keep in mind, however, that very soft mats might not be very durable, especially if your horses wear big caulks on their shoes. It's best to find a happy medium.

With any luck, laying down mats will be a one-time chore in your barn--although a back-breaking and sweaty chore it certainly can be! The long-term benefits of rubber mats, however, are well worth the effort. They can make almost any surface in your barn safer and more comfortable for your horse, whether he's resting in his stall, holding up a foot for the farrier, or getting a bath before a show.

As with anything else, it comes down to this: buy the very best you can afford, install it properly, then reap the benefits.

About the Author

Karen Briggs

Karen Briggs is the author of six books, including the recently updated Understanding Equine Nutrition as well as Understanding The Pony, both published by Eclipse Press. She's written a few thousand articles on subjects ranging from guttural pouch infections to how to compost your manure. She is also a Canadian certified riding coach, an equine nutritionist, and works in media relations for the harness racing industry. She lives with her band of off-the-track Thoroughbreds on a farm near Guelph, Ontario, and dabbles in eventing.

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