_ETFE

_Ethylene Tetrafluoroethylene

Introduction

ETFE (ethyl tetrafluoroethylene) is a transparent and lightweight membrane used particularly in applications where natural light is required and combined with a lightweight structure creates an ecological and economical solution.

Beyond the performance of glass ETFE is fast becoming the most exciting material

Introductiono Type of plastico Durable , adaptableo Transparento High corrosion resistanceo Wide temperature rangeo Technically a polymero Founded around 1970’s

Brief look at the history of ETFEo First patented in the 1940’s by US manufacturer

DuPonto Went commercial in the 1970’so Vector Foiltec, a sail making firm set up in 1982

pioneered the Architectural use of ETFEo Technical breakthrough came when co-founder of

Vector Foiltec, Stefan Lehnert used his expertise in engineering and ocean racing in developing a fixing system.

Brief look at the history of ETFEo For twenty-five years Ben Morris and Stefan

Lehnart of Vector-Foiltec have been filling the world’s roof line with ETFE

o Vector Foiltec Located in Germany lead the way of in the fabrication.

o IASO, Hightex and Covertex (Europe) are providing competition

ETFE life cycle o Ethylene is produced by steam cracking

Gas or light liquids are heated and ethylene is extractedo TFE is manufactured from chloroformo Both then are polymerizedo Follows thermoplastic injection sequence

Material is fed in to heat barrel Goes to cavity Cools and dries

o ETFE resin is produced either in powder form or compressed in to pellets.

Productiono ETFE Film is either blown or extruded

In both processes, ETFE resin is heated to a temperature in excess of 380 degrees Celsius to reach a molten state

o Extruded film cost more but the has a higher quality the molten resin is passed between rollers, which

extrudes a film up to 2200 millimetres wide filmo The extruded film are cooled by passing over a

series of rollers Wound, stored and transported

Fabricationo Fabricators specify foils in terms of

Colour Transparency translucency opacity either matt or shiny services and thickness, which varies from 0,015 up to 0,250 mm.

o The fabrication of ETFE cushion envelopes, like sail making combines digital technology with handcraft

o EFTE cushions can be made in any size and shape

Fabricationo A typical assembly comprises two to five layers

of foil of varying thicknesses.

o The foil is cut into length that are welded together to create the large surface areas of the cushions.

o The cushions are assembled manually: this is so that all the layers can be trimmed and welded

to form the cushions keder edge at the same time. The most common cushion edge is the keder detail

formed by a rope welded into the foil.

Fabricationo Finally the moulded ETFE air valve are installed

into the cushions surface and sealed.

o The ETFE cushions are then folded carefully to avoid wrinkling the films and wrapped in protective case for shipping.

Installation o These cushions are fitted into aluminium

extrusions fixed to the primary frame and linked through valves to the inflation system. The extrusions incorporate thermal breaks, insulation and internal channels to provide a secondary backup system of drainage. Site installation is to be carried out by specially trained crews.

Cushion sizes o Cushions can be manufactured to any size and

shape the only limit being the wind and loadingo rectangular cushions the cushions will span 3.5m

in one direction and as long as one requires in the other.

o Although other manufactures specifications differ. IASO 4.5m for rectangular cushions

o For triangular cushions where the foil is two ways spanning, the size can be increased Watercube Project some of the bubbles in the design

spanned 9 meters

Two Types of Applications

o Single-layers applications

A single layer is used with double curvature geometry

o ETFE Single-layer application: Radclyffe School use of ETFE has been particularly popular in the

construction of new schools The atrium area at Radclyffe School has been covered

to provide an open but dry space for students and staff to congregate

A cable net accommodates the larger ETFE spans

Two Types of Applications

o Multi-sheet applications These are built with two or more ETFE sheets, closed on their

perimeter and attached to the perimeter anchorage system. They need an inflation system using dry air at low pressure, which is produced by means of a unit made up of fans and a distribution network. It is controlled by means of an intelligent system.

o ETFE multi-layer application: The Eden project

The Eden project was the first of a new generation of buildings design expressively for ETFE cushion systems.

The dome makes use of a two layer hex-tri-hex geometry Cushion sizes range from 5-11 meters in diameter to suit the each

dome There are no expansions joints in the biome, any structural

deflections are readily absorbed by the pliable ETFE envelope

ETFE Material Qualitieso Surface

ETFE is unaffected by UV light, atmospheric pollution and other forms of environmental weathering

and does not discolour or become brittle over time 50 years life expectancy

o Light Weight single ply ETFE membranes and ETFE cushions are both

extremely lightweight 1% weight of glass

o Transparency ETFE Foil is very transparent across the visible light

region (380-780 nm) with a transparency of approximately 94-97% of total light

ETFE Material Qualitieso Foil Treatments

While the base material is very transparent, ETFE foil can be treated in a number of different ways to manipulate its transparency and radiation transmission characteristics.

o Surface Varying the surface characteristics of the foil

o Printing Printing graphics on the foil with ink of varying colour

o Embodiment Embodying pigments into the foil to change both its

colour and colour rendering qualitieso Radiation

Printing the foil with selective radiation treatments

ETFE Material Qualitieso Surface

during the manufacturing process to render it transparent or matt in appearance.

Same light transmission as clear foils But direct light is scattered Matt foils are excellent for projecting light on to.

ETFE Material Qualitieso Colour - Pleasure

ETFE multilayered construction and the ability to print graphics, embody colour, manipulate the surface qualities, and laminate LED’s and light tapes to each individual foil layer allows the creation of envelopes of almost infinite visual variety and interest.

ETFE Material Qualitieso Printing

printed with a wide range of graphic patterns to change its visible appearance and affect the amount of light and solar energy passing through it

The graphics are applied by rollers In the three layer cushions, the printed graphics controls

light and manipulate perception, by using variable air pressure to move the middle foil in the cushion

ETFE Material Qualitieso Radiation

ETFE foil can be treated with selective radiation applications to reduce the amount of UV and IR light passing through the building envelope

ETFE Material Qualitieso Solar technology in ETFE

Integrating photo voltaic cells with ETFE cushions allows the harvesting of the solar energy

o Thermal Comfort the thermal comfort under a ETFE roof is much better

than under an equivalent glazed systemo Durability – cleaning

surfaces of the foils are absolutely smooth and actively deter dirt

external surface self-cleanses under the action of rain has outstanding anti-adhesive - internal soiling is

minimized

ETFE Material Qualitieso Maintenance and repairs

Exceptional tear resistance If an ETFE Foil cushion becomes damaged, the

individual cushion can be easily removed and replaced with minimal disruption

Minor repairs to the foil, such as a puncture hole, can be done in situ

ETFE Compared to Glasso Transmits more light than glasso Better insulatoro Cost less to install

Depending on the size of the application installed.o 1% the weight of glasso ETFE is also resilient, able to bear 400 times its

own weighto Size Cushions can be manufactured to any size and shape the

only limit being the wind and loading.

ETFE on the other hand it is prone to punctures by sharp edges; therefore it is mostly used for roof

construction.

ETFE Sustainably Greeno University in Middlesex and Buro Happold Consulting

Engineers in London did a study of the environmental effects of ETFE manufacture and use for building cladding

o The Study found Using ETFE gives architects and engineers the opportunities for day lighting a structure, reduction of steel for support structures, and it can save on transport costs because of its light weight.

o ETFE Film is recyclableo ETFE can shrink the overall carbon footprint while the

materials own tread on this planet is relatively light

ETFE Sustainably Greeno The Art Centre College of Design in Pasadena recently

received a LEED certification and is the first structure in Pasadena to do so, due in large parts to the use of ETFE in the design of the building

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Conclusiono The main aim of the study was to describe the state-of-

the-art regarding the understanding of ETFE material characteristics and increase confidence in its implementation during the design process by architects and builders, pushing the limits of design and sustainability

o As ETFE cushion structures are being designed more frequently, the principles of ETFE are becoming more widely understood. Having an in-depth knowledge of the materials characteristics and structural integrations will allow us to evaluate and develop systems that meet and balance the design intent for both aesthetics and performance with pragmatic, cost-effective solutions.

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