A guide to non-slip coatings

Ethylene propylene diene monomer (EPDM)

Most of the bright, vibrant, colourful rubber surfaces found on today’s new playgrounds have been created using another type of synthetic rubber called ethylene propylene diene monomer (EPDM). This material was created to satisfy the need for a synthetic rubber that can withstand the harsh conditions of the outdoors.

It is designed not to crack and has outstanding heat, ozone, and weather resistance. Thermal properties maintain its flexibility between -50 and 150 C (-58 and 302 F). It also has excellent electrical insulating properties and good resistance to many chemicals. Because of these properties, EPDM has been used for decades in seals, gaskets, hoses, waterproofing membranes, and many other applications—all which require extreme durability under the harshest conditions.

The use of high quality EPDM in rubber surfacing is a large factor to its success over the past 32 years. Unlike recycled SBR rubber, EPDM is coloured at the manufacturing stage where the pigment is effectively infused throughout the granule. This means there is no paint or tint to wear away.

The finished surface can be sanded or cut and it would be the same colour throughout. The use of EPDM has enabled rubber surfacing to offer virtually unlimited design potential. The long history of EPDM already used in rubber surfacing combined with decades of history in many other industries is why EPDM is still regarded as the premium choice material.

Thermoplastic vulcanizate (TPV)

Another type of synthetic rubber that has made its way to the rubber surfacing market is called thermoplastic vulcanizate (TPV). The attraction of TPV is its ability to maintain bright bold colours, especially useful in large-scale commercial applications. TPV is relatively new as a surfacing material and to date does not have a long history to fall back on like EPDM does. Time will tell as to whether it can prove itself as a long-term contender before being classified as a mainstream product in the rubber safety surfacing market.

In a bind

Having discussed the various synthetic rubbers used in a poured-in-place safety surface, it is also important to review the different resins used to bind the rubber granules together. First and foremost, it is essential that any resin used in a wet deck area, whether for a pool or splash pad, be formulated for underwater applications.

Methylene diphenyl diisocyanate (MDI)

The most commonly used binder is methylene diphenyl diisocyanate (MDI). It is an aromatic, one-part, moisture-cured urethane resin, which is not only strong, but also has the ability to keep the rubber granules flexible. It should be pointed out that MDI-bound rubbers will experience a chemical reaction known as ambering, which affects the top granules of the surface. This reaction is noticeable in some colours more than others and will eventually wear off after continued exposure to the elements. Depending on location, or how much sun or shade the surface is exposed to, colour selections should be chosen carefully.

Aliphatic

If an environment is likely to cause surface ambering where very light colours (e.g. white, light grey, or beige) are required in the mix, it may be favourable to avoid this possible reaction by using aliphatic resin, which is not affected by ultraviolet (UV) light. It is more expensive than MDI, but at times when price is not the important factor it can be worth the consideration.

Epoxy resin

Epoxy resin is usually a two-part mix system and careful attention has to be paid to the mixing ratio. Formulations containing powdered metal and rubber or plasticizers are very tough and shock-resistant, which results in a harder finished surface than when using MDI or aliphatic resins. Epoxy can also trigger long-term sensitivity (allergies) from overexposure, and is often expensive.