Industrial Laser Proves Effective at Removing Nonstick Coatings

The Manufacturing Processes Engineering research group at the University of Cordoba has validated a new method for the removal of anti-adherent fluoropolymer coatings using a continuous-wave (CW) Nd:YAG laser.

The research focused on the factors involved in the removal process of coatings made of fluorinated ethylene propylene (FEP) and polytetrafluoroethylene (PTFE). The researchers compared stripping processes for FEP and PTFE nonstick fluoropolymer coatings, analyzed the qualities of each coating and the coating’s degree of influence on the energy efficiency and rate of stripping, and how the stripping process affected the mechanical and superficial properties of the aluminum substrate.

The research group characterized different parameters such as toughness, roughness, and mechanical properties of the material after being exposed to the laser. They demonstrated that the stripping process by CW Nd:YAG laser was more efficient for PTFE than for FEP coatings, after evaluating the process fluence (J/cm²) and the stripping rate (cm²/min). They did not find any relationship between the microhardness of the fluoropolymer coating and the efficiency of the laser stripping, but found that greater efficiency of laser stripping was related to lower reflectance of the fluoropolymer and lower thickness value of the coating.

The processing cycle: priming + polymerization; final coating layers + polymerization; laser stripping and final cleaning by blasting; fluorinated ethylene propylene (FEP) (green) and polytetrafluoroethylene (PTFE) (dark). Courtesy of G.G. Vaca et al./Polymers.

The Nd:YAG laser stripping of PTFE coatings appeared to produce a smaller increase in Ra and Rz roughness on substrates than that produced in the case of FEP coatings. The mechanical properties, tensile strength, and Vickers hardness of the aluminum alloy showed few variations after successive cycles of CW Nd:YAG laser coating removal, both for PTFE and FEP coatings.

Professor Guillermo Guerrero Vaca said the results show that the technique behaves effectively, especially for PTFE, so “we can conclude that it could be an alternative for these kinds of coatings instead of other kinds of methods.”

Although the Nd:YAG industrial laser has several applications, for example in the field of welding and in ophthalmological treatments, never before has it been used for stripping these specific kinds of materials, the researchers said.

Despite their resistance, fluoropolymers wear away with use like any other kind of material. The alternative to replacing an entire piece, often an expensive solution, is removing the coating, taking out any impurities, taking off any parts that are attached, and recoating the material. Since fluoropolymers are extremely resistant and chemically inert materials, they adhere to a surface and do not come off easily. This has spurred interest in finding an efficient means of removing worn-out fluoropolymers.

The research was published in Polymers (http://dx.doi.org/10.3390/polym11010123).