Highly popular in many areas of life, packaging films are hard-wearing and powerful, particularly when made of plastic. Whether used in newspaper film, confectionery, packaging for dairy products, ice bags, construction films or baked goods packaging, everyone has several versions at home.
Figure 1. Layer thickness of a transparent foil
Film Extrusion - That’s How It Works
Plastic packagings are manufactured by film extrusion. Viscous to solid curable plastics are continuously pressed out of a die or die under pressure. Bodies with the cross-section of the opening, known as extrudate, are manufactured in any length theoretically.
Thickness, Topography and Roughness of the Foils
It is highly important to select materials and process them based on efficient quality assurance. In regards to quality assurance in film production, the first quality to check is film thickness.
According to the purpose of the layers, thicknesses varying from a few nanometers to several hundred micrometers must be measured. Where films have functional surfaces, it is also important to measure and assess the topography of the film surfaces in addition to the thickness.
A non-contact sensor is required in the measurement of soft film surfaces. This measures topography and layer thickness, along with calculating the roughness of the surface. This method of measurement can handle complicated tasks such as:
- Fast line measurements throughout the film strip, along with;
- High-resolution 3D measurements to analyze the fine structures of the film.
Figure 2. Plastic bag surface, analysis of roughness
Technology of FRT
The FRT MicroProf® with optical sensors bridges the gap between practicable measurement methods and information requirements. The MicroProf® measuring tools are supplied with a confocal, chromatic distance sensor for applications with film thicknesses higher than 40 µm.
The sensor records the distance to the film interfaces with high resolution and specifies the film thickness from the difference. The TTV system provides an optimal solution for assessing the film thickness of non-transparent films.
The sample is measured from each side simultaneously, enabling the determination of the total thickness variation (TTV), sample thickness, roughness of the top and bottom sides and 3D topography.
Efficient, non-contact topography and profile measurements are enabled on highly mirroring and reflective surfaces, along with highly rough and absorbent, jagged targets.
For Particularly Thin Foils
As an option, a sensor can be utilized for the measurement of thin foils from 2 µm thickness, which assesses the interference of the light reflecting on the upper and lower foil surfaces. An enhanced method provides topography measurements for the characterization of foil surfaces.
Both sensors can be used in combination with the MicroProf®. Additionally, a reflectometer is utilized for the measurement of thin-film systems. Using the FTR sensor, layer thicknesses from 10 nm with a resolution of 1 nm can be identified.
This information has been sourced, reviewed and adapted from materials provided by FRT Metrology.
For more information on this source, please visit FRT Metrology.