Inside DURAFLEX – the five layers engineered for stone

Protection film is not a single material. It is a system. Each layer has a specific job, and the performance of the whole depends on every layer doing that job correctly. Understanding the structure explains why not all films behave the same way on stone, and why the engineering behind DURAFLEX is not interchangeable with anything else on the market.

The five layers of DURAFLEX SPF Ultra

Starting from the top and working down to the stone surface, DURAFLEX SPF Ultra is built from five distinct layers, each engineered for a specific purpose.

Cap sheet

The cap sheet is a temporary protective layer that sits on top of the film during installation. It protects the surface of the film while it is being handled, positioned, and trimmed. Once the installation is complete and the film is heat sealed, the cap sheet is removed. It plays no role in the long-term performance of the film, its job is to get the film onto the stone in perfect condition.

Top coat

The top coat is the self-healing layer. It is the surface that absorbs minor contact marks, fine scratches from cutlery, surface abrasion from daily use, and recovers through a process enabled by the polyurethane chemistry beneath it. The self-healing property is not a coating applied to the film. It is a function of the material itself. DURAFLEX holds the patent on this application for stone surfaces.

The top coat also provides the optical clarity that makes the film effectively invisible on the stone. It absorbs approximately five percent of visible light. The finish of the stone, gloss, honed, satin, remains unchanged beneath it.

TPU layer

TPU stands for thermoplastic polyurethane. This is the structural core of the film. It provides the dimensional stability that keeps the film flat and consistent across large surface areas. It carries the heat resistance that allows DURAFLEX to withstand 230 degrees of direct contact heat without distorting. It contributes to the UV resistance that prevents the film from yellowing over time.

Polyurethane is the polymer of choice for this application because of its specific combination of properties, flexibility without brittleness, resistance to chemical degradation, and the molecular structure that enables self-healing in the top coat above it. Films that use alternative polymer bases do not share these properties.

Adhesive

The adhesive is the layer that bonds DURAFLEX to the stone surface. It is engineered specifically for natural stone, a formulation developed through testing on marble, quartzite, travertine, and other stone types to ensure it bonds correctly without damaging the material beneath.

The critical design decision in the adhesive is that it bonds to the chemical sealer on the stone, not directly to the raw stone itself. This means that if the film is ever removed, the adhesive releases from the sealer layer rather than from the stone. The stone underneath is untouched.

The adhesive chemistry also has to be neutral to the stone over time. Early attempts at stone film products used adhesives that, after extended contact with calcium carbonate, began to etch into the surface. DURAFLEX’s adhesive is formulated to remain stable indefinitely against marble and natural stone chemistry.

Release liner

The release liner is the backing that protects the adhesive before installation. It is removed immediately before the film is applied to the stone. Like the cap sheet, it serves no function once the installation is complete.

Why the system matters

Each layer is engineered in relation to the others. The TPU layer has to have the right modulus to support the self-healing top coat above it. The adhesive has to bond the TPU to the stone without introducing stress that affects the optical clarity of the film. The cap sheet has to protect the top coat without leaving any residue that could interfere with the heat sealing process.

This is not a product that was designed by selecting the best available film off a shelf. It was built from the chemistry up, with stone surfaces as the specific application. That is what the patent protects, not just the final product, but the engineering decisions that make it work.