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.
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 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 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. EPDM is often 45 mils; HypalonR and PVC are 60 mils. 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, like EPDM and like HypalonR. But, unlike those materials, it 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.
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.
However, these Elastomerics are not caulks or sealants. While they must tolerate expansion and contraction, and the dynamics associated with the roof, just like a caulk or sealant. But, caulks and sealants don’t require resistance to standing water, impact resistance, or reflectivity properties.
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