ACRYLIC COATINGS

Most people are familiar with at least one acrylic plastic, Plexiglas ® . Plexiglas is an all-acrylic material, usually associated with a polymeric, plastic material that is extremely durable, and has excellent weathering properties, and is very resistant to ultraviolet radiation from sunlight and the adverse effects of weathering. Plexiglas is an all-acrylic material, meaning that it is composed entirely of highly durable building blocks called monomers. While this is a clear sheet of the acrylic plastic, most acrylics are blended with other materials to create other easily recognized products such as paint, adhesive or caulk.

Acrylic polymers can be formulated to be tough and hard, and also very flexible. Plexiglas impact resistance is one example where it is used in banks to provide bulletproof shields. But acrylic polymers can also be manufactured to be flexible, to be tolerant of movement at low temperature, very elastic in their behavior.

THE RIGHT ACRYLIC FOR THE RIGHT JOB

In the mid-1950’s, acrylic technology developed to the point where these polymers could be incorporated into waterborne emulsion. This created the advent of the acrylic latex waterborne house paints. In the mid-1950’s, an excellent highly durable house paint was based on solvent-based alkyd chemistry. In the 90’s the most widely used, highly durable house paint material is a waterborne acrylic material. The key feature of acrylic materials is that they can be used for a wide range of applications, but you need to use the right acrylic for the job. Polymers that you would use to make adhesives would not necessarily make good floor polishes. The polymer chemistry that’s used to make elastomeric roof coatings would not necessarily do well as a leather tanning material. The acrylic used for house paint would not necessarily make an excellent caulk or sealant. But they’re all acrylics. So the key thing here is the right acrylic for the right job.

ACRYLIC ROOF COATINGS-FEATURES AND BENEFITS

Acrylic polymers have been engineered that are specifically designed for roof applications, and specifically for roof coatings. Coatings manufacturers have tried to use house paints on roofs but these were too brittle. Formulators also tried to use caulk and sealant technology to make elastomeric roof coatings, but they have not been totally successfully – resulting in failures. Today the technical requirements for a successful roof coating are fully understood. Acrylic elastomeric roof coatings refer to a liquid-applied monolithic (seamless), fully adhered, elastomeric membrane that’s formed in situ on the roof. These coatings are applied 5 to 10 times thicker than a house paint. Typically, the thickness of an exterior house paint is 3 mils, .003 inches. For elastomeric roofing applications, these would be 15 to 30 mils. So we’re talking about membrane-like materials. However, with these coatings the membrane comes out of a can. That’s why the term formed in-situ on the roof is used. It’s applied as a liquid. As it dries, it forms a tough membrane that has no seams. No field or factory seaming is necessary. Moreover it is also fully adhered. These coatings are not mechanically attached like other types of single-ply membranes.

NOT A PAINT

The roof coating looks like a paint in a can. It has the same viscosity as paint, which makes it brushable or sprayable, or, it can be applied with a roller, just like a house paint. But, it’s a very different material based on a different class of acrylic chemistry. Also, it’s a material that has a unique set of performance criteria. An acrylic elastomeric roof coating is not a paint. Typically, a paint does not require resistance to ponding water, reflectivity properties, flexibility at low temperature, ability to expand and contract or resistance to foot traffic. But an elastomeric roof coating does require these properties. The roof is going to sit on a relatively horizontal surface, tolerating many external stresses and water contact for extended time.

These acrylic roof coatings are usually white in color. This white color provides two unique features. First it reduces the temperature of the roof membrane to which it is applied. This reduced temperature coupled with the UV blocking properties of the coating reduces the degradation and deterioration of the roofing membrane enabling it to last longer. This white color also reflects as much as 85{9ebecd4f19c13f0adaee9f389a860bcb521bfb71002b56008f26cdaa1f7321a0} of the heat portion of the sunlight, reducing the heat transfer into the building and reduces air conditioning costs.

EXPANSION AND CONTRACTION

Roofs are dynamic environments, meaning they expand and contract. We look at a building, and we don’t think it moves. In a microscopic examination, roofs are dynamic. There’s thermal expansion, seismic expansion, the weight of snow and rain loads, wind uplift and “flutter” and vibrational effects that subject roofs to movement. The coating must be able to tolerate that kind of movement at roof temperature, and high temperature, in the summer, low temperature in the winter. Roofs must also tolerate foot traffic resistance. People are going to be walking on these roofs. They will be servicing HVAC units, cooling towers, satellite dish antennas; all kinds of equipment that’s placed on a roof. The roof must be able to withstand foot traffic and the abuse from maintenance and repair crews.

DURABILITY

The key property required of any roof coating material is durability. Acrylic technology is widely used in exterior applications for sealants, Plexiglas R , industrial coatings, house paints, because of its durability. Durability implies resistance to the effects of UV degradation from the sun. The sunlight strikes a polymer, such as asphalt, the asphalt absorbs some of the radiation, and the polymer begins to vibrate, and break up into smaller pieces. This is the degradation that is associated with the harmful effects of sunlight. This can be seen readily in aged asphalt roofing. When new, it looks OK. However, six months later, there’s a brown chalky residue. This is the result of ultraviolet degradation from the sun. Acrylic polymers are transparent to ultraviolet radiation which means they do not absorb the sun’s destructive radiation. The polymer is not absorbing any of the radiation; it’s reflecting the radiation back into the atmosphere. When that same acrylic polymer is formulated into a roof coating and the UV transmission is measured, there is no transmission. The coating contains UV blocking pigments that reflect this degrading UV radiation and so the roof substrate is protected.

EASE OF APPLICATION

Another advantage of acrylic roof coatings is that they are easy to apply. They are waterborne materials, they’re single component and don’t require two component mixing. Simply stated, they are very easy to work with. They can be applied just like a house paint, by spray, by roller, by brush, by squeegee. They can be cleaned up with water, airless spray units can be rinsed with the same ease that a painter would rinse out after painting with typical latex house paint. They don’t carry any volatile organic compound constraints, they’re not red label, and because they are waterborne there is little concern about shipping and handling. These coating have minimal toxicity, usually no more than a conventional house paint.

COST PERFORMANCE

From a cost performance standpoint, these acrylic roof coatings are extremely attractive. When compared to other types of coatings used to maintain roofs, acrylics, in terms of the initial cost, are sometimes higher an asphalt emulsion or an asphalt cutback. But when the expected service life of the coatings is considered and life cycle costs are computed, the acrylics come out with the most attractive (lower) life cycle costs.

SILICONE COATINGS

Silicone is quickly becoming the go to material in the flat roof coatings market. Its benefits range from leak-free protection to improved aesthetic appeal of the roof to improved sustainability. When a silicone roof coating is installed, it is there for performance. These roofs are also highly sustainable and could quite literally be the last roofing substrate you ever need with only a recoating every 10-15 years. Check out this video that illustrates the ease of application of silicone flat roof coatings: Roof Coating Restoration.

The Benefits of Silicone as a Flat Roof Coating

Let’s look at the benefits of silicone as a flat roof coating. What does it do that no other material can?

First, it withstands ponding water – indefinitely. Because silicone coatings are not water based like acrylic, they absorb no moisture. While some acrylic coatings can be reinforced with fabric to withstand a little ponding water, they are no match for silicone’s natural resistance to moisture. Another benefit to silicone is that it doesn’t chalk off as other flat roof coatings do. Silicone is “Non- sacrificial”, and as such it doesn’t slowly shed as time goes by. It will stay fully intact for the life of the roof. Thirdly, silicone doesn’t need to be reinforced with roof fabric, saving you time and money on installation. The last major benefit to silicone is that you need less of it than most other flat roof coatings. As little as 2 gallons can be used for 100 square feet, less than half that would be needed for acrylic.

Things to Watch Out For

Silicone can be very slippery when wet. Because it resists water, the surface becomes very slippery at the first sign of water. Be careful. Another warning is that the coating must be applied to a completely dry roof. If there is any moisture on the surface, it can compromise the adhesion of the silicone to the roof.

While silicone doesn’t normally require multiple coats or reinforcing tape, there are certain instances where you want to use each of these. If you have a dry cap sheet roof, you probably want to apply a silicone base coat, then another coat of silicone on top of that. Also, if you find any loose seams, you want to reinforce with tape or fabric prior to applying the coating.