Airbag coatings: the battle between silicones and organics
New organic materials for coating textiles have popped up on the market, thus putting into question the future of silicone coatings. However, rest assured because silicones are our present, and our future. Their properties are unrivaled by any other organic material. Plus, time tells all: there is a reason why silicones have been used in airbag coatings for more than 20 years.
In a previous article, we discussed some reasons why silicones replaced neoprene. Let’s take a look now at a few ways silicones outperform organic materials.
When the going gets tough, silicon gets going
Silicon, the main element in silicone polymers, is largely responsible for making silicone one tough cookie. Unlike the carbon based polymeric materials, the silicone polymer exploits the strength of inorganic materials – a tougher bond between atoms in the chain – together with the flexibility of organic chemistry to bring various chemical functions. All this leads to a very resistant material, as more energy would be required to break the silicone polymer Vs organic polymer, and to a very flexible material in a wide temperature range, as the silicone polymer is more free to rotate Vs organic polymer.
The strength and resistance of silicone rubbers both go over well in the rough world of airbags, which have to withstand some seriously harsh conditions such as extreme temperatures and humidity. These factors, in turn, accelerate airbag aging, making cushions hard and rigid. However, accelerated aging tests have shown that silicone coatings are more resistant to extreme conditions than organic materials. In the past with neoprene, manufacturers had to replace airbags regularly. Nowadays, with silicone coatings, there is no need to replace airbags because they will last the entire lifespan of the car.
The ability of the silicone polymeric chain to rotate enables to design silicone rubber coatings that will remain extremely flexible even at very negative temperatures, unlike organic coatings that will eventually become brittle. This is essential in cushion designs, when the goal is to reduce the size of airbag modules, while ensuring 100% efficient deployment.
Furthermore, the silicone polymer has thermal stability and is thermal resistant. Since in airbags pyrotechnic inflators are used to deploy the cushion, it is also a clear advantage of silicones! In case of airbag deployment, the pyrotechnic explosion inside the inflator will release extremely hot gases which silicones can protect against, unlike polyurethanes for example.
Silicones: smooth application
Other materials must be mixed with solvent or water that have to be removed after application and before curing the coating material, and this requires energy. Another option is calendering or laminating textiles by using two rollers to melt the film onto the textile. This works well but the production process is much slower than with standard coating processes. At Elkem Silicones, we offer liquid silicone solutions with an ideal viscosity that are easy to apply, clean and 100% solvent free. Just use a regular knife coating head to apply a silicone rubber onto textile— like spreading honey on a slice of bread!
In short, when compared to silicone, organic materials have less durability, less flexibility and a less effective thermal shield action. Time has told all and that’s silicones that have stood up to the test.