A window gasket should be designed to prevent leaks for the long term, say, at least 30 years. And during those years, the gasket remains under compression, may be exposed to UV light, and must be pliable enough to allow for some shifting due to wind load. Window manufacturers have several choices of materials, when selecting a glazing gasket. Let’s review the most common options.
PVC is a plastic known for its low cost and versatility. It’s an excellent choice for many appliances and toys and, although it is used by some low-cost residential window manufacturers, we do not recommend it, because it does not hold up over time. Customers who come to us to help them re-glaze an old building, will commonly send us a sample of the original gasket. If that gasket was made from PVC, it is not unusual to find that the original gasket has shrunk by about 5%, has become quite hard, and has cracks in it. This is due to plasticizer migration over time, especially when exposed to UV. Such gaskets are almost certain to leak.
From the standpoint of performance, Silicone is perfectly acceptable for glazing gaskets and in some situations is the only option. It will hold up well over the years. However, it has a very low tear strength and is typically about 50% more expensive than all other options. We have saved many of our customers a lot of money by offering TPV.
EPDM is a synthetic rubber introduced into the market around 1960. Its low compression set and high resistance to UV light make it an excellent choice for window glazing gaskets. And, since it has been commercialized for over sixty years it is also a safe choice.
TPV (Thermoplastic Vulcanizate), introduced in the 1980s, is an elastomer with made from EPDM in a matrix of polypropylene plastic. This combination of these two very different materials gives it the performance of EPDM rubber (low compression set, UV resistance) with the processing advantages of plastic (recyclability, tight tolerances, design flexibility, and lower cost). Even better, while EPDM and TPV do have similar performance characteristics when new, TPV outperforms EPDM after only a few years.
In fact, when some windows in the United Overseas Bank, a 66-story tower in Singapore, were replaced after 22 years, the original TPV gaskets (Santoprene) were tested next to the new gaskets (also Santoprene) and were found to be nearly identical. You can read about it here. And that is one of the best arguments for using TPV in window glazing gaskets.
In sum, TPV is the best choice for window glazing gaskets because of its:
Head over to our Materials page to learn more!