3. Polymer coatings on metal containers

Polymer films are often used as a barrier coating on beverage and food containers. Figure 35 shows an FTIR-PAS spectrum of a polymer coating on the interior of a beverage can. The spectrum was measured directly on a small specimen cut with scissors from the can. The surface morphology of such a specimen is of no consequence in an FTIR-PAS measurement whereas surface flatness is critical in a specular reflectance measurement that the reflected fraction must be focused on the detector.

Fig. 35. Infrared spectrum of a beverage can's internal coating measured by FTIR-PAS.