Optimal Processing of Polypropylene Films with CO₂ Lasers

  Polypropylene, commonly abbreviated as PP, is one of the most common and important plastics used today. It is a thermoplastic that has practical applications in many different industries. Its strength, flexibility, and resistance to damage means polypropylene film is an excellent material for various types of storage and labeling applications. In addition, polypropylene has an ability to withstand heat. This, combined with chemical resistance to organic compounds, makes it a good choice in particular for food and beverage packaging.   In recent years, the digital revolution has changed the landscape of the flex-packaging and labeling industries. This challenges manufacturers to meet demands for high design flexibility and shorter time to market. Digital laser converting provides the solution with on-the-fly customization, zero contact processing, and repeatable results. Synrad high performance CO2 lasers are ideally suited for many of these applications. This is due to our long wavelength’s superior absorption in many common film materials. In the specific case of polypropylene films, you can change the CO2 wavelength slightly from the standard 10.6 µm to more optimally absorb into that particular material. This can result in significant speed and process quality improvements.  

Chemical Properties and Absorption Characteristics of PP

  To efficiently use the laser energy in the process, the photons of the laser beam must be absorbed into the material rather than transmitted or reflected back. This leads to efficient vaporization of the material with little energy lost due to passing through the material, melting, or chemical degradation processes. When absorbing Infrared Radiation (IR), a polymer molecule’s chemical bonds will vibrate. These vibrations will stretch and bend the bonds within the polymer chain. However, for that absorption to occur, the energy level of the IR photons at a specific frequency must match the distinct vibrational energy differences within the molecule.