252 Introduction to Renewable Biomaterials
These results pushed researchers into deep and innovative studies, proposing new
thermoplastic materials, useful in many different applications. Much work has already
been done in order to reduce plastic solid waste, but still much work has to be done: the
important results obtained until now symbolize a step forward in facing environmental
impact problems of plastic industries, hoping for a better future.
8.3 Thermoplastic Composites with Natural Fillers
During recent years, many researchers have focused their attention on natural fibres as
fillers for thermoplastic composites. These kinds of fibres, in fact, are characterized by
many advantages with respect to traditional glass and carbon fibres such as low cost,
low density, comparable specific tensile properties, non-abrasive to the equipment,
non-irritating the skin, reduced energy consumption, renewability, recyclability and
biodegradability [33, 34]. Table 8.10 shows the main feature of natural fibres, in
comparison to traditional glass fibres.
Some of the widespread applications for composites with natural fillers are aerospace,
leisure, construction, sport, packaging and automotive. In fact, these industrial sectors
have shown enormous interest in the development of new composite materials [35]. One
of the first examples of using natural fibres instead of fuel-based ones is Trabant.
Trabant (Figure 8.9) is the first-known application of natural fibres in automotive
industries, produced in 1958 in the German Democratic Republic. The main parts,
manufactured with phenolic resin reinforced with cotton fibres, were roof, boot lid,
bonnet, wings and doors [36].
Table 8.11 reports the mechanical properties of some natural fibres as compared to
conventional fibres and polymers [37].
Natural fibres are a large family of fibres, including wood, cellulose, hemp, flax, jute,
sisal, kenaf and many others [38]. In particular, wood–plastic composites (WPCs)
Table 8.10Comparison between natural and glass fibres [can natural
fibres replace glass?].
Natural fibres Glass fibres
Density Low Twice that of natural
fibres
Cost Low Low, but higher than
natural fibres
Renewability Yes No
Recyclability Yes No
Energy consumption Low High
Distribution Wide Wide
CO 2 neutral Yes No
Abrasion to machines No Yes
Health risk when inhaled No Yes
Disposal Biodegradable Non-biodegradable
Wambuaet al. 2003 [34]. Reproduced with permission of Elsevier.
