02 | 2008

Natural Fibres
Automotive door in-liner, instrument panel made from bio-fibre
reinforced composites (Photo: Dräxlmaier Group)
Natural Fibre/PP (LoPreFin, Fibroflax)
Natural fibre/PP is made of two different types of fibres. These
are natural fibres (flax, sisal or similar) on the one hand and thermoplastic
fibres (PP or similar) on the other hand. The two types
of fibre are mixed in a closed tank to a homogeneous mixture.
The non-woven mat obtained can be formed by placing in a heated
mould and forming under pressure. The synthetic fibres are melted
and given the shape of the finished part.
Fibropur
A needle-punched vegetable fibre mat is sprayed into a mould
together with a two component PU system. The sprayed mat is
then heated to 125°C and compression moulded to realize a light
structural carrier.
COIXIL
Fibre Resources
The principal fibres being used for automotive components
come from flax and hemp, grown in the temperate
climates of Western Europe, the sub-tropical fibres, jute
and kenaf, mainly imported from Bangladesh and India,
banana fibre from the Philippines, sisal from the USA
(Florida), South Africa and Brazil, and wood fibre from
all over the world. The table shows the commercially
important fibre sources of agricultural bio-fibres that
could be utilized for composites. The traditional source
of agro-based composites has been wood, and for many
countries this will continue to be the major source.
Commercially important fibre sources
[Suddell, Evans, 2005]
Fibre Species World
production [10 3 t]
Origin
Wood >10,000 species 1,750,000 Stem
Bamboo >1,250 species 10,000 Stem
Cotton lint Gossypium sp
18,450 Fruit
Jute Corchorus sp 2,300 Stem
Kenaf Hibiscus cannadbinus 970 Stem
Flax Linum usitatissimum 830 Stem
Sisal Agave sisilana 378 Leaf
Hemp Cannabis sativa 214 Stem
Coir Cocos nucifera 100 Fruit
Ramie Boehmeria nivea 100 Stem
Abaca Musa textiles 70 Leaf
COIXIL is a Johnson Controls Automotive co-injection technology
with sequential injection of two different materials in the melted
state from the same point - first a soft TPO skin (A) and then a
more rigid core material (B) which is a short bio-fibre reinforced
polyolefin to give shape and resistance to the component. The final
structure is a sandwich (A-B-A).
Exterior parts are on the way
The automotive industry requires composite materials that
meet performance criteria as determined in a wide range of
tests. A typical market specification includes criteria such as ultimate
breaking force and elongation, flexural properties, impact
strength, flammability and fogging characteristics, acoustic absorption,
processing characteristics, dimensional stability, water
absorption or crash behaviour. Most of the composites currently
used are designed with long-term durability in mind. Generally,
bio-fibres can be used as both filler and reinforcement for interior
components and are now generally accepted for those applications.
Furthermore they can be expected to increase steadily with
increased model penetration.
But today more and more bio-fibre composites are also used
in the exterior components of an automobile. DaimlerChrysler‘s
innovative application of abaca fibre (banana) in exterior underfloor
protection for passenger cars has been recently recognized.
Exterior parts such as front bumpers or under-floor trim for buses
made from flax fibre reinforced composites are other examples.
A full list of references for further reading can be obtained from
the publisher.
www.kutech-kassel.de
20 bioplastics MAGAZINE [02/08] Vol. 3