The Constructor

Applications and Properties of ETFE as a Building Material in Construction

Neenu S K

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ETFE is a manmade fluoropolymer which stands for ethylene tetrafluoroethylene, which has attained its position as an efficient architectural material. The appearance of ETFE is like a transparent sheeting material type, which can be employed instead of glass and plastic that are hard in nature. ETFE is widely used in modern buildings which possess greater architectural features. Its composition has a major ingredient of fluorite, which is a mineral that is commonly found. The fluorite is combined with other two compounds namely trichloromethane and the hydrogen sulfate. The above mixture, by the process of pyrolysis, produces chlorofluoroethylene, which is later combined with ethylene to make ethylene tetrafluoroethylene or the so called ETFE. ETFE is regarded as one of the exciting material in building construction industries. It has favored the construction world with the potential it offers.

Properties of ETFE as a Building Material

The properties of ETFE materials reflects the advantages it provides. ETFE possess a non-sticky surface, which gives them a self-cleaning as well as recycling capacity. The combustion of material would result in the emission of hydrofluoric acid (HF) which is highly toxic and corrosive in nature. This force us to undergo a proper disposal for this material. Sharp edges create punctures in these materials, hence it is commonly used as roofing or as a cladding material. It is stretchable, hence a variation in size can be compromised. This advantage is more effective when ETFE are used as a roof material. The tensile strength of ETFE is 42N/mm2 with 89 K to 423 K as its working temperature. It is found highly ultraviolet light resistant when subjected to a weathering test done under high acceleration. The test showed no kind of deterioration in the material.

Architectural History of ETFE

ETFE is an invention of DuPont during a research program which was intended to determine an insulating material for machinery in the industry. The properties meant to develop where high temperature resistant (in both low and high temperature), friction and abrasion resistant as well as higher immunity towards radiation. The application of ETFE started as ETFE wire and cable in nuclear, aerospace and automobile industries. It is one of the stable chemical compounds,that made them applicable for linings as well as in filters. The ETFE as an architectural material took its place during the year 1973 to 1974, where it was a period of the oil crisis. The authorities found it essential to harvest solar energy to replace fossil fuels to fight against the crisis. ETFE film was developed by the researchers (an extruded form of ETFE) as a replacement for glass in thermal solar collectors, greenhouses etc. This application made ETFE more famous than glass material, which further leads its way to broader architectural applications.

Sustainability Aspects of ETFE

The ETFE material helps in life costing by assuring lower maintenance costs when compared to other materials of fabric used. As mentioned in the properties of ETFE, they clean out dirt coming over it, because of the smooth surface it possesses. During rain, the dirt is washed out easily, unlike other fabric material used, which instead have uneven surfaces that hold and attracts dirt.

Fig. ETFE Cushion View from Below

The interior surface of the ETFE cushions may be cleaned at 5 to 10 years’ interval with water. But mostly it is found unnecessary. The ETFE material constitutes chlorodifluoromethane which is not a petrochemical derivative and is found safe for the ozone layer.

Use of ETFE in Construction Technology

The ETFE can be installed over the structure based on the requirement of insulation, lighting, and building aesthetics. It can be

Single Layer

Here a single film of ETFE film is installed which are connected to the primary structure and reinforced by means of wire cable or aluminum or lightweight steel.

Double Layer

For both double and triple layers of ETFE, inflated cushions are created. These cushions are filled with low-pressure air. This is the criteria which provide thermal resistance and stability in structure.

Fig. Double Layer Installation

Triple Layer

Fig. Triple Layer Installation

Advantages ETFE as a Building Material in Construction

The ETFE material gains certain advantages as mentioned below, which dominates glass or all other similar material which were used conventionally:

ETFE possess high light transmission property. The light transmission can be controlled my choosing a specific film, from the variety of films they provide. Adequate lighting through ETFE would help in reducing the cost that is invested for additional lighting activities.

Fig. The efficiency of light transmission is high compared to other materials for ETFE and remains almost same with time

It is highly resistant towards damage due to chemical actions as well as higher wear and tear due to any range of weather. A data showing tensile stress variation with time for different materials including ETFE is shown below.

Fig.: Variation of Tensile Stress of ETFE with Time

It is seen from the above-depicted graph that with time, the tensile strength of ETFE is less decreased compared to other material i.e. polyolefin and PVC.

ETFE retains its transparency by its self-cleaning properties.

It is when installed in multiple layer, shows higher insulation, as shown in the figure below.

Fig.: Double Layer ETFE film layer as an insulation

The ETFE material after use can be recycled and converted into useful industrial products. Their lightweight nature makes the use of lesser fabrication thus reducing the emission of carbon dioxide into the atmosphere.

The ETFE films are transparent, which when installed would provide adequate ventilation to the building indoor, reducing the cost and energy of additional lighting requirements.

It has been proved that the ETFE film material has efficiently undergone the International tests for fire resistance and proved extremely fire resistant. It's combined property of light weight and fire resistance make them use prominently in insulation areas in aerospace.

The material is less inflammable due to the presence of higher fluorine content, compared to other plastic and fabric construction material available. The presence of low oxygen index gives itself extinguishing property.

As mentioned in properties that ETFE emits HF under combustion. This happens only when the temperature is above 800 degree Celsius.

Fig.: ETFE under Fire

ETFE gains the advantage of self-venting. This would prevent heat that is built within the structures, which further causes an explosion or building collapse. The ability of self-venting would make the interior into an open space, thus reducing the accumulation of heat and further destruction.

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