Looking at an unknown sample of plastic material is like looking at a completed puzzle. Although there are a variety of pieces to the puzzle, all you can see is the final product.
By using a variety of different testing methods, it is possible for a lab to break down a final product into the various “pieces” that are used to make the plastic. The composition of the plastic, just like a puzzle, can either be easy to figure out or very complex, making it more of a challenge—unless you use the right testing method.
One effective way to find trace amounts of additives, copolymers, and even contaminants is to do Fourier Transform Infra-Red, or FTIR testing.
A Quick Explanation
FT-Ir spectroscopy involves “probing” a small sample of material with infrared light. The material will either absorb the light or allow it to pass through, depending on its unique composition. The testing equipment will then record the differences in the infrared light coming from the source as compared to what is read by the detector.
Even slight differences in the amount of infrared light help the equipment create a unique profile for the material. Through a mathematical formulation known as the ‘Fourier transform,’ this unique profile can then be broken down into the individual chemicals (based on the profile developed).
This method is proven to work because certain molecules act consistently when exposed to the infrared light used in FTIR testing. As such, the patterns literally create a chemical fingerprint that is unique to that particular molecule.
The high level of sensitivity with FTIR testing makes it extremely effective at quickly breaking down the big picture into the individual pieces. In addition, it can be used in conjunction with other types of testing that also uses the infrared spectrum to verify the composition of an unknown plastic or to test for contaminants within a very small test sample.