Testing, testing… 1,2,3. Is this thing on? Can everyone hear me? (clearing of throat).
For every property of silicone there is a silicone-based product. That translates into a whole lot of products, and therefore a whole lot of testing. Before releasing products on the market, Elkem Silicones performs a plethora of tests on its solutions to ensure all their properties make the grade in terms of quality and safety. Read on to find out how silicones are put to the test to ensure the performance of your paints, airbags and engines.
Paints: silicone and the test of surface protection
To avoid mishaps later on down the line (and thus painting the roses red!), silicone is tested before being added to paints to ensure its resistance to high temperatures, wetting performance and slip. Some of the processes it goes through are described below:
- High temperature resistance test: Silicones are placed in an oven heated up to 300°C to see if any cracking occurs.
- Wetting performance test: This test measures surface tension by placing a drop of liquid on the surface of silicone and measuring how fast the drop spreads.
- Friction coefficient test: We use this test to determine how easily silicones slide onto surfaces where they are applied. It is also helpful in preventing craters from forming on the surface.
Once silicone is added to paint as a wetting and spreading agent, we then perform additional tests to check how silicone behaves in the paint formula. For example, we paint a surface with our silicone-based paints and let the paint dry. We then use a reflectometer to measure the amount of light that is reflected by the surface. If the surface is uneven, the light will appear disrupted, unlike a smooth surface which will produce a mirror-like effect, similar to the shiny side of aluminum foil.
Lastly, we look at how paint stands up to the test of heat. For this, we paint a piece of metal and bake it at a set temperature and duration of time to see how the paint reacts. Similarly, we can also connect the painted piece of metal to an electrical circuit to observe the effects.
Airbags: silicone and the test of time
Airbags are life saving devices whose performance is enhanced by the unique properties of silicone. However, since airbags undergo powerful mechanical and thermal forces, we have to carry out a series of age tests to ensure that, even after ten years, silicone will preserve its unique properties and airbags will continue to operate like new. There is no room for surprises; therefore, silicone must meet a certain number of conditions:
- A flexible, thin coat of silicone is required as space and weight considerations are important to prevent airbag blocking.
- Silicone has to be able to resist a wide range of temperatures, thus passing low-temp and high-temp deployment tests.
- Over time, silicone must be able to preserve its properties, thus passing life-cycle deployment tests and tests on heat-aged parts.
- Silicone must provide a barrier of protection against liquids and gases.
To ensure these conditions are met, we run the following tests:
- Adhesion scrub test: This test checks for proper chemical adhesion when we coat a fabric in silicone. The silicone-coated surface is rubbed together, and if the silicone coating remains intact, then silicone has retained all of its properties.
- Blocking test: To prevent the silicone coated fabric of airbags from becoming stuck or glued together, we perform a blocking test which consists of pressing the fabric together with heat to determine how much force is needed to pull them apart again. If too much force is needed, then the silicone coating fails the test.
- Thermal resistance tests: In this type of test, metal parts are heated and placed on the silicone-coated fabric of an airbag to measure the time it takes for the metal to melt through the fabric.
- Edgecomb resistance test: We use this test to check if silicone-coated fabric has lost its properties over time. A comb with needles is used to perforate the fabric. The fabric is then pulled to measure how well it resists.
- Permeability tests: To determine how well silicone-coated fabrics resist air pressure, a cap is placed on the airbag which is then exposed to high pressure.
In addition to the tests above, we also perform a range of aging tests under varying temperatures and humidity levels and viscosity tests to check the liquid state of silicone.
Engines: silicone and the test of resistance
Defects in the engine block can lead to serious mechanical malfunctions and destruction. Since we don’t want to take any chances, here are the tests that silicone has to stand up to in the engine:
- Degradation tests: This test is used to determine the oil resistance of silicone. By heating rubbers in oil at a range of different temperatures we can measure the mechanical performance of silicone before, during and after the process.
- Blowout tests: Blowout tests allow manufacturers to test how well gaskets stand up to high pressure. Once the engine has been assembled, different levels of pressure are applied to check the integrity of seals. If leaks or blowouts occur, then the engine is not ready for use.
- Static test: This test simulates what occurs in an engine in terms of forces. Since an engine is designed to go fast, it will have to resist many different types of forces. During this test, gaskets are tested under tension to see if they move and how they react to static and dynamic stress. Fatigue tests are also carried out.
- Adhesion test: Adhesion tests are performed to test how well silicone adheres to both clean and unclean surfaces. During manufacturing, engine parts are cleaned with soap; however, remnants of oil may still be present and this can alter adhesion. Therefore, this test involves placing parts in a box with oil and then heating them. After, we assess whether the adhesion properties have been affected.
Since the market requires processes for mass production, we cannot afford to overlook all the small details that determine the quality of silicone and of its properties. When it comes to testing silicone, we follow the golden rule: prevention is better than the cure.
Every test mentioned in that article are used by our Technical Service laboratories but are generally not used for the quality control of our productions.