Mylar / Melinex (PET Film)

Physical properties

Laser processing

Melting PET releases acetaldehyde, acetic acid, and other volatile organic compounds with a characteristic odor. Fumes are not highly toxic but require extraction with an activated carbon filter for continuous use in enclosed spaces.

CO₂: Excellent for making stencils with CO2 laser. PET film reacts to the laser with clean cuts, perfectly defined edges, and no burrs. Low power (8–15W) at medium speed. The material does not burn but melts and shrinks slightly: air assist is important to maintain precise cutting. Typical thicknesses of 75–200 µm cut in a single pass.

Diode: Diode laser works on translucent PET film, but light reflection requires higher power compared to CO2. Best results on opaque or colored film.

Fiber: Not applicable.

CNC / milling processing

PET film is too thin and flexible for any CNC machining with rotating bits. It would deform immediately under tool pressure.

Plotter and thermoforming

Blade plotter cutting with standard sharp blades on medium-tack mat. PET film slips easily: ensure good adhesion to the mat before starting. Excellent for high-precision stencils.

Post-processing

Sanding: Not usefully sandable: the smooth, hard surface of PET film does not respond significantly to abrasive paper.

Gluing: Bondable with PET-specific adhesives or high-tack double-sided tapes. The smooth, non-porous surface of PET makes bonding with water-based adhesives difficult.

Over time: PET film is highly chemically stable. Resistant to moisture, dilute acids, and most solvents. Degrades very slowly with UV exposure: remains effective for years of use as a reusable stencil.

Common defects

• Slight shrinkage and thermal deformation of the laser-cut edge if heat accumulates from too-low speed
• High electrostatic charge that attracts dust and particles during and after processing
• Difficulty writing with conventional markers without a PET surface primer

Safety

PET burns with difficulty and self-extinguishes when removed from flame. During laser processing fumes are irritating but not acutely toxic. Keep extraction active.

Availability and formats

Commercial formats: rolls in thicknesses 75–250µm, pre-cut A4/A3 sheets, anti-reflection coated film

Related materials

Sources

• Schede tecniche Dupont Mylar e Dupont Melinex PET film
• Manuali operativi FabLab per stencil laser e serigrafia