Industrial plastics are ubiquitous in the world around us, and in many applications, plastics are coated to provide protection from scratches or UV and/or to improve aesthetics. The layer can be applied through painting, coextrusion, lamination, or other processes, but in each case the function is the same: to provide an attractive and long lasting part. When properly formulated and applied, the protective layer can last for years or even decades, but when mistakes occur the parts can fail over very short periods. When that happens, there is always someone eager to point the finger of blame. Unfortunately, it’s not always easy to know why the part failed and who should shoulder the blame. The following three examples illustrate that point.
- High-end thermoformed all-terrain vehicle parts turned yellow after a short period of use and with longer times, the topcoat peeled completely from the part. Investigation showed that the topcoat was not formulated properly to protect the underlying plastic so the plastic beneath the topcoat degraded and eventually turned to powder. It would be very easy to blame the supplier of the topcoat for not formulating the coating properly, but in this case, it was actually the processor who chose to use a lower cost coating rather than the more expensive, properly formulated product offered by the material supplier.
- A fiberglass reinforced spa had a beautiful high-gloss coating applied to it that cracked and crazed after a short period of use. Investigation showed that the failure was due to a combination of chemical attack from plasticizers used in the part combined with a mismatch of thermal expansion coefficient between the layers. The problem was resolved by removing the plasticizers from the products used in the application.
- A thermoformed automotive part had a high-gloss, scratch-resistant topcoat. Over time, the topcoat delaminated completely from the part leaving it worthless. Analysis showed that even though the materials appeared to adhere well when first produced, the combination of a poor match of both the modulus and the expansion coefficient of the materials was able to overpower the adhesion of the primer, which led to complete failure of the interface. The problem was solved by reformulating the primer layer to improve adhesion and to bridge the properties of the layers.
As these examples illustrate, parts may fail for many possible reasons. Identifying the actual cause(s) of the failure is a first step toward understanding who is responsible for the failure and how to correct it. The investigation requires a strong technical understanding of the materials and processes used to produce the parts, and will likely include a number of powerful analytical tests such as microscopy, Fourier transform infra-red spectroscopy (FTIR), depth-profiling, and others. The experts at Innov8 Chem have decades of experience in diagnosing these types of failures. Call us to discuss how we can bring that experience to bear on your product failures.
