Roof coatings and liquid applied roofing materials are probably the fastest growing segment in the commercial, industrial and flat roofing market today. There's a reason for that, but what we want to do today is take a look at some of the primary liquid applied roof technologies that are out there, and the differences in some of the physical properties of those.
The four we're going to look at today are acrylic, silicone, asphalt emulsion, and synthetic rubber. Specifically we're going to take a look at the puncture resistance differences between those, which is going to be a combination of the elongation and the tensile strength. Let's have a look at some of these tests that we do and the difference between these products, and why they're gaining different traction in the market.
Let's start with the exciting, fun test first. We coated small watermelons with four commonly used roof restoration products. We let them cure for two weeks, and then drop them from 25 feet.
A bare watermelon, on impact, is obliterated.
The first product we tested is a commonly used asphalt emulsion for both roofing and waterproofing. It was applied to the melon at 60 mils or 1.5 millimetres. Unreinforced asphalt emulsion has no elongation or tensile strength, resulting in very poor impact resistance. The watermelon didn't fare much better than the first one.
Next up is an acrylic roof coating widely used in the industry. Applied to the 3rd melon at over 40 mils, or 1 millimetre. The forces created inside the melon on impact quickly split open the acrylic coating.
Silicone Roof Coating
Third is a very popular silicone roof coating. It was applied to the melon at 50 mils. While silicone has higher tensile strength or tightness than acrylic, the impact test shows how easily silicone tears once a split or tear begins. With both silicone and acrylic you can see that even 100 to 300 percent elongation does not allow for much movement when fully adhered.
Finally we have synthetic rubber manufactured by Triton, called Tritoflex, applied to the melon at 80 mils, or two millimetres. Not only does the rubber withstand the forces upon impact, it nearly retains its original shape after the melon has broken inside.
Considering the Tritoflex rubber was not damaged, we dropped it a second time this time next to a broken uncoated watermelon for comparison. The properties of over a thousand percent elongation and 600 psi tensile strength, were evident in this demonstration.
Let's take note of the value of these tests, because you may be thinking these are a little extreme... What kind of roof experiences these kinds of forces? And that's an appropriate thought. But if you think about, it roofs do experience a lot of extreme forces. They experience hail, foot traffic, dropped tools and equipment, high wind speeds and underlying structural movements.
Though those underlying structural movements may not be big in distance, they can be very big in force. And therefore that's why it's important when you're choosing a roof membrane in your design, that it performs more like a skin and not like a paint.
On to the second test, which is a simple yet effective puncture resistance test to demonstrate the forces required to puncture through a coating or a membrane.
First up asphalt emulsion.
The material has no elongation or strength, resulting in a quick break.
This first one is about 40 mils, or one millimetre in thickness, and cured for two weeks. There's minimal stretch in the force required to cause a puncture was minimal.
This next acrylic is thicker, about 60 mils or 1.5 millimetres in thickness, and cured for two weeks. With the increased thickness, there is minimal increased puncture resistance.
Now we have silicone.
This one is approximately 60 mils in thickness, 1.5 millimetres, and cured for two weeks. You can see the strength is higher than acrylic requiring more force to stretch it over the pipe, but once the silicone breaks it results in a very quick tear through the entire sheet. While the tensile strength is higher than acrylic, the actual tear resistance is poor.
Synthetic rubber membrane called Tritoflex
Last is a synthetic rubber membrane called Tritoflex. This sample is approximately 80 mils, or 2 millimetres in thickness, and cured for 2 weeks. The test shows both the high elongation properties of synthetic rubber combined with the high tensile strength. This requires a much higher force to puncture the membrane.
All right now that we've done the test let's summarize these four product technologies that we showed you, and where they're most used and some of the differences that are important to know between them.
First we'll look at cold process asphalt emulsion.
It's called cold process because it's applied at room temperature, or ambient temperature, unlike older asphalt technologies and roofing that are heated up in hot kettles and applied at very high temperatures. This is typically a water-based product that's used often for damp proofing. And in roofing it must be reinforced because you can see here the elongation at break properties and the tensile strength properties, are quite low. And so reinforcement is used in that in order to make it more like a membrane. And so asphalt emulsion is used often as a base layer for a lot of acrylic roof restoration systems. And I have a small sample of some commonly used asphalt emulsion roof coating here, and you can see that the strength, there's not a whole lot of strength here as our videos demonstrated, but if you reinforce it with a polyester fabric then it it has no elongation or flexibility but now all of a sudden it's it's a very tight, stronger membrane.
Now asphalt emulsion is not UV stable, so it needs to be top coated. And there's a certain window in which it needs to be covered otherwise the UV will damage it. And asphalt emulsion does not do well with freezing temperature. It has terrible freeze-thaw flexibility and a low temperature bend of flexibility in those tests. So it's commonly used in warmer year-round climates like southern California in the southwestern united states, as part of an acrylic restoration system used to extend the life of a roof. Obviously the cost of an asphalt emulsion product and system is very low, even though it's applied often at 40 to 100 mils total thickness, including the polyester reinforcement.
So then we moved to acrylic. And acrylic is a very commonly used roof restoration product, has been for decades as a topcoat on spray foam, as a top coat over asphalt emulsion. It's also used directly on existing roofs to extend the life of that roof. Because acrylic has good reflectivity, so it provides great UV protection to preserve the integrity of the underlying roof components such as the waterproofing membrane, and the insulation. And so acrylics are great for that purpose as sort of a sunscreen to protect the existing roof from UV damage, and to preserve the integrity longer, and protect it from that heat gain and the heat aging.
Acrylic is typically applied at 20 to 30 mils, or sometimes it may be higher. You have to be careful with acrylic going to thick because it is a very permeable product, it will absorb water doesn't do well under ponding water. It will wrinkle up and it will allow for vapor transmission. It is a breathable product, therefore it's not used as a waterproofing membrane. It's used as a uv protection coating. And it's also a very sustainable, because acrylic can be easily repaired and easily renewed with time. And so by using an acrylic roof coating you can create a sustainable system and continue to preserve the life of that roof, indefinitely, when used properly.
Obviously the properties of acrylic are like a high grade paint. There's not a lot of stretch, though some roofing acrylics have some good tensile strength, but they can be torn quite easily and there's not a whole lot of elongation at break there. So you have to think when something is fully adhered to a surface you're going from absolutely no distance to a far distance when you have that expansion and contraction. Here's a very thick acrylic which would absorb a lot of water and again not a whole lot of flexibility there. Again, it gets stronger the thicker that you put it on but again the tear resistance on that is is quite poor. But it is inexpensive, so it's a great way to extend the life of roof when you don't need a new roof membrane or a new waterproofing layer on the existing roof.
So next we move the silicone
Silicone is also a breathable product, it has a 5 perms rating, but it does hold up well to ponding water. That's why it's become popular as an alternative to acrylic, because it does better under ponding. But I put the asterisk there because it's still a permeable product. If water sits on silicone long enough, it will absorb through, and and can get beneath the silicone film, and so that's something important to know.
Silicone is also bright white, like acrylic, so it's good for reflectivity for UV protection, for energy efficiency, but I put an asterisk on there too because silicone is notorious for having a bad dirt pick up compared to acrylic. While acrylic has a good dirt pick up resistance, it stays a white for many years, silicone can tend to yellow and discolor because it has a high dirt pickup. It's stronger than acrylic, as you can see here, and has a little bit more kind of a stretchiness or rubberiness because silicone is a part of the rubber family, but like I showed in the video that once a tear does start, it peels apart almost like cheese. Almost no pressure at all will cause the silicone to tear. And that's because of the type of chemical matrix that silicone has. And so that's something to be leery of in areas where you may have hail, and if you have a split into the silicone, that split can easily tear and continue through the entire roof surface. So that's something you have to be a concerned with regarding silicone. It's also very difficult to repair. Silicone has a very low surface energy compared to acrylic, so acrylics will stick to other acrylics quite easily - emergency repair patches, asphalt mastic, rubber mastic, urethanes will stick to acrylic. None of those materials will adhere to silicone because of the low surface energy. Only silicone will adhere to silicone. So it makes it very difficult to repair, very difficult to re-coat, because the right silicone has to be matched up in order to do a re-coat.
Also, with that low surface energy makes it a very slippery product. So if there's any dew on the surface, any rain on the surface, it can be a big safety hazard. And it's also not a true waterproofing membrane. Typically it's only applied 20 to 36 mils dry, but it is an economical choice. The reason why this has become more more popular than acrylic, because of a little bit of that increased tensile strength, but mostly because it holds up better under ponding. But you do have to sacrifice some of that reflectivity with time when you go with the silicone.
And then the fourth liquid applied product that we tested was a synthetic rubber material produced by Triton called Tritoflex. It's typically applied at 60 to 80 mils dry, it has over a thousand percent elongation at break, with over 700 psi tensile strength. And it's 0.1 perms, so it's considered an impermeable or non breathable product. So it is considered a waterproofing membrane.
With the elongation and tensile properties that makes it very durable, and makes it resistant to hail, foot traffic, a lot of different things that a roof does experience including underlying structural movement, if you think of, for example, an existing metal or steel building. It withstands ponding water indefinitely, not just for a certain period of time, like silicone. It is also renewable, both on its own, exposed to UV, because synthetic rubber produced here is a UV resistant product, but when you use the acrylic topcoat you can continue to sustain the life of that roof indefinitely, which is a great savings in value for a building owner long term.
The non breathability can be a pro in a con. It's good because you know that it's completely watertight, it's not going to allow any moisture transmission or air or gas transmission to the underlying roof or structure. But it can be a con in some situations. If they're if you're just trying to extend the life of the roof short term, and acrylic may be better because if you have some residual moisture in the roof system and acrylic will allow that breathability. A synthetic rubber membrane will not; it'll trap any moisture in in an existing surface and will allow that to breathe out.
And it is synthetic rubber is black in color, so that's a downside. So these are already white, this is black. But again, this is used as a waterproofing membrane for durability, flexibility, to create a long-term 15, 20, 25 year roof system. When combined with an acrylic top coat, you can achieve that reflectivity, the sustainability and then with that sacrificial layer you can continue to renew the life of that roof indefinitely.
And here I have some examples of the synthetic rubber on its own, so you can see here the elongation and recovery, but combined with the tensile strength makes it very difficult to pull apart, but fully adhere to a roof it makes a lot of difference when you have the combination of good flexibility with the tensile strength.
And then of course combining it with a reflective topcoat, you're able to achieve the goals that you have here, while having a strong durable seamless membrane underneath. As you can see here this is acrylic on top of the rubber, that the acrylic splits apart with any of that stretch. So this would be similar to an acrylic directly on a surface that has some expansion and contraction and movement.
So essentially as you look forward to considering a roof restoration system for your building, you have to take a look at the technologies that are available. The technical data behind those and what's most appropriate for your roof system. Do you need something that's going to protect your roof long term? Are you looking for simply uv protection and a short-term extension of life? Or are you looking for a long-term new waterproofing membrane to protect your structure?