Expanded PVC (Forex, Palight, Kapa)

Physical properties

Laser processing

Identical to rigid PVC: releases gaseous hydrochloric acid (HCl) that irreversibly corrodes laser optics and poisons the operator. The expanded structure does not reduce the chlorine concentration in the plastic — on the contrary, the larger foam surface area can lead to faster and more widespread combustion. The fact that it is light and soft does not make it less dangerous: it is still PVC.

CO₂: ABSOLUTELY FORBIDDEN. Despite its light weight and appearance similar to safe materials (foam, cardboard), expanded PVC contains the same percentage of chlorine as rigid PVC. Under CO2 laser it produces an identical amount of hydrochloric acid (HCl) that destroys the machine optics and poisons the operator.

Diode: ABSOLUTELY FORBIDDEN. Same degradation mechanism as rigid PVC: HCl production regardless of material density.

Fiber: ABSOLUTELY FORBIDDEN. No type of laser is usable on PVC, expanded or not.

CNC / milling processing

Excellent CNC and manual tool workability. The expanded material cuts, mills and planes easily due to its cellular structure. Fine, powdery chips. Does not require aggressive clamping. Ideal for model making, scenography and rapid prototyping of shapes.

Plotter and thermoforming

Cuttable with cutting plotter in thin formats (2–5mm). Deep cut blade or rotary blade. The cellular structure may cause slightly frayed edges on low-density foams.

Post-processing

Sanding: Dry-sandable with good results. The surface cellular structure requires filler or filler primer before painting to achieve a smooth finish. 120 grit for levelling, 240 for finishing.

Primer: mandatory. Filler primer necessary to seal the surface cellular structure before painting. Apply 2–3 coats and sand between coats for optimal results.

Gluing: Bondable with PVC cement, double-sided tapes, hot glue and contact adhesives (caution: some solvents may attack the foam). PVC cement creates very strong joints. Avoid MEK-based or concentrated cyclohexanone adhesives that dissolve the cellular structure.

Over time: Excellent dimensional stability. Does not absorb moisture. Good UV resistance with additives (grades for outdoor use). Does not rot or swell. Decade-long durability in outdoor signage applications.

Common defects

• Frequently confused with laser-safe materials (cardboard, EVA foam, polystyrene) due to light weight — one of the most dangerous materials to accidentally place in a laser cutter
• Cellular surface structure requires treatment before painting
• CNC-cut edges expose the cellular structure — require filling/puttying if aesthetics matter

Safety

Recommended PPE: mask_p2, safety_glasses

ABSOLUTE RULE: never laser, regardless of density. The lightness of the material makes it seem harmless but the chlorine content is identical to rigid PVC. During CNC machining and manual cutting, ventilate the area for PVC dust. The material is not food safe.

Availability and formats

Commercial formats: panels 1000×2000mm in thicknesses 1–19mm, panels 1220×2440mm, rolls (thin foam)

Related materials

Sources

• 3A Composites Forex — Technical data sheet
• Palram Palight — Material safety data sheet
• Health and Safety Executive UK — PVC thermal degradation