Bit

ECOBRAKE

ECOBRAKE is a 30 month project funded by the Technology Strategy Board (TSB) and forms part of the UK high value manufacturing initiative.For further information, please contact the project researcher Will Newby: w.newby@ex.ac.uk

Currently, the production of rail friction materials (brake linings) depends on an unsustainable supply of synthetic aramid fibres (e.g. Kevlar) and an extremely energy intensive manufacturing process; it is therefore costly in both environmental and financial terms. ECOBRAKE will develop a new technology to create brake pads for mass urban rail transit vehicles (e.g. Docklands Light Railway) from ENVIRONMENTALLY FRIENDLY, SUSTAINABLE materials. Compared with the current manufacturing process, this new technology is FASTER,

more ENERGY EFFICIENT, and uses CHEAPER MATERIALS.

FRICTION MATERIALS

Brake pads are composite materials, the 3 major components of which are:

• Resin (to bind everything together)

• Reinforcing fibres (to provide strength, toughness, and aid manufacture)

• Friction modifiers (to provide the desired frictional characteristics across a wide range of operating conditions)

The resin dominates the mechanical properties of the pad and must withstand cyclic loading of high temperatures and stresses whilst maintaining a stable coefficient of friction.

Currently, phenolic based resins synthesised from non-renewable resources are used to fulfil this requirement, but a naturally occurring alternative has been discovered in the husk of the cashew nut shell.

SUSTAINABLE MATERIALS

RESIN

Cashew Nut Shell Liquid (CNSL) is the viscous dark brown substance found in the husk of the cashew nut shell. It is a sustainable and naturally occurring source of phenolic compounds which can be used to produce thermally stable resins suitable for use in brake pads. At present this liquid is considered a waste product by the cashew nut industry.

FIBRES

Since the abolition of asbestos, aramid has fulfilled the role of a strong, tough, and thermally

resilient reinforcement fibre in brake pads. These fibres are expensive and in short

supply.

Natural fibres, such as hemp, are a high performance, environmentally

friendly alternative. The low thermal stability of hemp is especially suitable in

low temperature applications (such as mass urban rail transit).

Industrial Hemp is a fast growing, disease resistant plant which absorbs CO2 and

self-fertilises the land upon harvest. Fibres extracted from the stem of the plant (bast fibres) exhibit specific mechanical properties comparable to E – glass, and have been used

in the manufacture of automotive composites for some time.

CNSL resin and hemp fibres will form the bulk of the new “ECOBRAKE” pads. Friction and wear

characteristics will be tailored for specific applications by adding a small number of other compounds.

THE FUTURE...

In 2008, 1.5M brake pads were replaced on mass urban transit vehicles across Europe and North America; it is envisaged that 20% of these will be ECOBRAKE pads

by 2013.

Not only will ECOBRAKE pads be more kind to the environment, but they will enable UK manufacturers to remain competitive in a rapidly expanding global market worth £32M.

DESIGN AND MANUFACTURE OF FRICTION MATERIALS FOR MASS RAIL TRANSIT APPLICATIONS USING ENVIRONMENTALLY FRIENDLY MATERIALS AND PROCESSES