Application of ETFE film materials in buildings

The plastic consumption in worldwide building industry each year is about 10 milion tons which is a quarter of the total output of the world plastic and is in the first place of applied plastic consumption. Plastic, cement, steel and wood were classified together as four building materials. The cause of the rapid development of building plastic not only is its good properties but also a significant reduction of forest area, increased awareness of preserve the ecological environment and national forest resources, land resources and water resources protection policies. Obviously, energy consumption in production and use of building plastic is far lower than the one in other building materials

At present, PTFE(Polytetrafluoroethylene) film is often used for membrane structure in building. This film is fibrous material. Its advantages are light weight, high strength, good suppleness, low maintenance and service life long and its disadvantage is not transparent. However, ETFE(Ethyl Tetra Fluoro Ethylene) not only has the same advantages but also is transparent.

The thickness of ETFE film is usually less than 0.20mm. ETFE film is transparent and is best substitute material in transparent building structure. Its service life is about 25-35 years and it is used for permanent multilayer removable roof structure. This kind of film material is usually used for 4m-span two or three layer air support structure. Also it can increase the span according to special project geometry or climatic conditions. Film length is usually about 15-30m. Small span single layer structure can use small size film.

Studies has shown that ETFE film has corrosion resistance, high or low temperature resistance, durability, anti-aging and fire retardant properties which are make it has a broad application prospect.

1, basic mechanical property

ETFE is tough and tensile material. Its various mechanical properties achieve a better balance- high tear resistance, high tensile strength, medium hardness, good impact resistance ability, long fatigue Life(25-35 years). ETFE is a good electrolyte material and it has high insulating strength. Its permittivity is 2.6 so it has high resistivity and low dissipation factor which is 0.003. Its low permittivity is constant when frequency or temperature is changing. It has high tear resistance, the best low temperature impact properties of fluoroplastic from room temperature to﹣80℃, stable chemical properties, good electrical isolation and radiation-resistance performance.

What's more, ETFE has passed several strict test, for example, IEEE383 and achieve level UL94V-0. ETFE film is up to B1,DIN4102 fire protection level standard and it does not drip when burning. ETFE film is very light its mass is 0.15-0.35kg per m2.

This feature has a significant advantage when film is melt due to smoke and fire.

Roof and wall which are made of ETFE film have light weight that is 1% weight of glass in the same size. ETFE film has good toughness, high tensile strength and more than 400% ductility. It is not easy to be torn.

2，high or low temperature resistance and light transmission

ETFE has a wide usage temperature range which is from -65 to +150℃. At ultralow temperature it is very hard and its brittle temperature is low to -100℃. ETFE film is crystalline polymer and its melting point is 256℃~280℃,. It can self-extinguish when burning.

According to the position and the surface printing，the light transmittance of ETFE film is up to 95%. This material does not block UV and other light to keep nature light though building. After surface printing treatment, the Light transmittance of this material reduce to 50%. According to the geometry and the number of layer, its K is up to 2.0W/(m2•K). The energy consumption index of a three-layer printed film is up to 0.77.

3, corrosion resistance and weather resistance

Except alkali metal, ETFE cannot be corroded by any chemical reagent, for example, concentrated sulfuric acid, nitric acid and hydrochloric acid. Its weight and properties cannot change when boiling in aqua regia. It hardly dissolve in all solvent except alkane (0.1g／100g) above 300℃.

ETFE don't absorb moisture, don’t combust and is very stable to oxygen and UV so it have a good weather resistance.

4, high Antipollution and recyclable

Very small friction coefficient which is one in five of the one of PE is main characters of full fluorine carbon surface. Adhesive resistance surface make it be self-cleaning and rain water can clean main grime. Because of the excellent properties, ETFE film hardly need to be cleaning and its cleaning cycle is about 5 years. ETFE film is also featured by easy maintance. It can be repair in situ.

ETFE film is full recyclable material and can be produce into new film or be separated impurity for producing other ETFE product.

5, application example and prospect

ETFE membrane material is made innto air pillow which is applied to membrane structure.

1, British leicester national space science center(NSSC) (picture 1) with rocket launcher shape was built in 2001, 41-meter high, covered by 2000m2 ETFE film. Some membrane can be unfolded for transporting rocket and satellite into exhibition area.

2, One of Britain's new millennium celebrations, the Garden of Eden have ‘the Eighth Wonder of the World’ reputation. Consisting of 4 dome shape building, it is the biggest greenhouse in the world. It is covered by transparent plate which is made of ETFE membrane. Its weight just is 1% the one of glass in same area. The transparent membrane can be recyclable and have good heat retaining property.

3,Vista Alegre was built in 2001 in Madrid, Spain. It is the biggest membrane structure building in the worlld. It integrated bullring, theatre and stadium and the roof uses double membrane structure. It has 50m diameter, 5000m2 area. The distance between two membrane is 12m and outer membrane is PVC and inner membrane is ETFE. Its service life is 30 years and don’t need to maintain the first 20 years. Its weight is only 1% of the glass but its load capacity is 400 times. Moreover,  the roof can be unfolded in 2min.

4, In World Expo 1986 in Vancouver, Canada, Ontario pavilion is made of 3437m2 transparent membrane. Its structure is supported by 17 tensegrity arch which is according to the radius.

5. Villa Arena shopping center (picture 5) ,Amsterdam, Netherlands, uses 3890m2 ETFE membrane getting IFAI 2001 years outstanding achievement award.

6, Yacht club Resort center, Nansei, Japan, is made of 500m2 ETFE membrane. It consists of 14 double layer inflate ETFE membranes and is 17m long. It is able to withstand 200 km/h typhoon.

7.The 2006 World Cup in Germany one of main stadium, Munich Stadium also use ETFE air pillow. The surface of stadium is transparent rhombus structure which blinks in the sunshine giving a kind of magical visual effect. Its ceiling and outer surface are made of ETFE membrane which is featured by self-cleaning, fireproofing, heat insulation and antifreezing to keep 350Pa atmospheric pressure in stadium.

8, In the 2008 Olympic Games in architectural design, ETFE membrane structure application gets perfect embodiment. The 2008 Beijing Olympic Games national swimming center ‘water cube’ ,except ground, use ETFE material. The blue surface is unexpectedly soft and farctate. Inner and outer membrane structure is composed of 3065 air pillows (minimum one is about 1～2m2, maximum one is about 70m2) and cover 100,000 m2 area, 260,000m2 unfolded, which is the largest membrane structure project in the world and it is the only complete membrane structure and totally enclosed large-scale public buildings. ETFE membrane structure is featured by heat insulation, easy maintain, light weight, self-cleaning, dewetting and antifogging. Anti-condensation function is especially important to swimming.

9，The 2008 Beijing Olympic Games another national stadium-National Stadium has steel structure roof which is covered by double layer membrane structure. Upper membrane is transparent ETFE membrane and lower membrane is translucent PTFE acoustic ceiling. This strucure also takes ETFE’s advantage of heat insulation, easy maintain, light weight and self-cleaning.

Membrane structure is the most representative form of construction in the 21st century. So far, it is one of the main form of Long-span space building. Integrating architecture, structural mechanics, fine chemical, material science and computer technology, membrane structure can not only express structural strength but also full exhibits the idea of the architect to enjoy nature romantic space. With large stadium, tourist sites and waiting hall of airport developing, ETFE shows their own advantage. However, because of very complex fluorine plastic film processing and extremely difficult manufacturing the companies which produce fluorine plastic are rare. For many years, fluorine plastic film production technology is mastered in DuPont and Asahi Glass.

Cooperating with many domestic and foreign companies and research institutions, after six years of intensive research, our company conquer the problems of the fluorine plastic molding equipment and process to realize localization of the full set of fluorine plastic film production equipment and has many innovation with in proprietary intellectual property rights. At present, our company has an annual output of 100 tons of fluorine plastic film production capacity.