ETFE adhesive tapes for solar applications

CMC Klebetechnik GmbH

The material ETFE, known as Hostaflon®, Fluon® or Tefzel®, is today used worldwide as a transparent building shell in the form of films (Watercube Beijing, Allianzarena Munich). The special advantages of films made of ETFE include its low weight, the extremely high weather resistance (>30 years) and transparency.

In many cases, solar technology applications require very good weather resistance. In this environment, flexible solar modules with ETFE as front protection films have been in use for more than a decade. The high transmission of the material into the UV range enables good performance values in terms of electrical efficiency. ETFE forms a very good bond with the encapsulation material (e.g. EVA), so that the flexible solar modules remain tight over the long term. The CMC 77701 adhesive tape adheres very well to ETFE surfaces.

But ETFE films are also used in other areas of solar technology. The chemically resistant, high temperature stable and flame retardant film can be used in different ways.

Trough power plants are usually made of shaped (glass/metal) mirrors that concentrate the solar energy onto a glass tube in which thermal oil circulates. A highly efficient, but expensive and failure-prone technology. In a service environment with few technical possibilities, maintenance-intensive systems are hardly applicable. But there are solutions for decentralised supply of e.g. villages without connection to the electrical infrastructure: Film-based trough power plants (e.g. patent EP2304334 B1)

The ETFE film assumes several functions: It creates the pressure-stable shell of the trough power plant. Similar to the self-supporting structure of air domes, the shell protects the thermal tube and the mirror surfaces from the weather (e.g. dust, rainwater). ETFE adhesive tapes from CMC provide long-term UV-resistant adhesive bonds between ETFE and ETFE or other materials. The silicone adhesive used is extremely resistant to aging. Sealing, reinforcing and, if necessary, repairs (holes, areas subject to bending) can be carried out quickly and easily with the CMC 77700 ETFE adhesive tape.

In order to be able to generate electricity at night, latent heat storage systems based on molten salts are often used. This means that the steam turbines of the power generators can still be operated during periods without solar radiation. Some of these salts are quite aggressive and corrosive. ETFE adhesive tapes from CMC are resistant to a very high number of chemicals due to the raw materials used. They can even be laminated on as surface protection and thus prevent corrosion damage. The polysiloxane adhesive is resistant to infiltration of the film.

Adhesive tapes for the production of solar modules

ETFE adhesive tapes from CMC 

CMC 77700, single-sided ETFE adhesive tape, wound on itself

CMC 77701, single-sided ETFE adhesive tape with protective cover on the adhesive, easy to cut with scissors/knives

CMC 77703, double-sided ETFE adhesive tape with protective cover, easy to cut to size

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Sooner or later, many solar electric systems have the problem that hail can damage individual modules. If the module does not need to be replaced immediately, the glass damage can be "repaired" by gluing on ETFE films. Without the progressive degeneration due to direct air contact through the defective front panel, the modules will function considerably longer. Immediate exchange is not necessary, the "repair" only takes a few minutes.

ETFE adhesive films are used wherever it is extremely important to achieve good long-term adhesion even when fully weathered. CMC Klebetechnik uses films from Nowofol®, Siegsdorf and coats a high-end polysiloxane adhesive on one or both sides of the films. Standard versions are CMC 77700 and CMC 77701, but other film thicknesses or designs are possible - CMC is itself a coater and adapts to customer specifications. In the past, coloured ETFE films or printed ETFE films were coated. Other film thicknesses (standard: 100µm) have also been coated (e.g. 300µm as a massive abrasion protection against suspension rope movements).

Another alternative to ETFE is ECTFE (Ethylene ChloroTriFluoroEthylene), which also has very good chemical resistance, is stable to ageing and can be used up to +150°C. It is considerably more transparent than ETFE and therefore allows even more light to pass through unhindered. Like ETFE, the film can also be bonded thermoplastically (high frequency welding, friction welding, infrared welding, ultrasonic welding).

Electrical insulation for outdoor connection cabinets

Special safety requirements apply to inverter control cabinets on larger solar fields. Among others, VDE-AR-N 4102 and DI EN 62109-1 (safety of inverters for photovoltaic energy systems) regulate requirements for such equipment. The easily punchable polypropylene material Formex® has excellent insulation properties and an exceptionally good CTI value of >600V (CTI = 0). As a housing liner or galvanic isolation within the electronics, Formex® also contributes as a flame barrier (UL 94 V0).

Hostaflon® former trademark of Hoechst AG
Tefzel™ ETFE trademark of Chemours (formerly DuPont)
Nowoflon® Trademark of Nowofol GmbH
Tefka® DX Trademark of Denka
Formex® Trademark of ITW Formex
Fluon® Trademark of AGC
F-Clean® Trademark of Asahi Glass

Head of Application Management

Gerald Friederici

If you have any questions, please contact:

Gerald Friederici

Tel.: +49 6233 872 356

E-Mail: friederici (at) cmc.de