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6
thermal degradation of natural fibres. Rubberized cotton, which
was earlier used in bicycle tyres, is an apt example of a natural fibrereinforced polymeric ‘green’ composite.
? Example 6.6 Discuss specific applications of thermoplastic
green composites.
v Answer
Bamboo or coir fibre-reinforced polyethylenes and
polypropylenes are being used as door panels in civil
construction industries. Bamboo fibre-reinforced PLA is being
used for various applications for complete biodegradability.
However, the use of biodegradable fillers (such as starch or wood
flour) in conventional thermoplastic or thermosetting matrices
increases the scope of biodegradable matrices. It is to be noted that
the bulk density of natural fibres is quite high, and this makes their
weight percentage in the composite quite low.
True green composites are manufactured by reinforcing natural
fibres in biodegradable polymeric matrices, such as PLA, PCL, or
PGA. These fibres are thermoplastic in nature and can be processed
using various methods, as applicable to other thermoplastics. The
processability of biodegradable composites is carried out in a closed
mould processing. The processability parameters for biodegradable
composites are as follows.
6.9.1 Processability of Natural Fibre-Reinforced
Thermoplastic Matrix Composite
The processability of these composites is governed by the following
factors:
5 Interphase in the Composite—The hydrophilic nature of natural
fibres restricts their wetting by hydrophobic polymeric matrices, which has been discussed in 7 Chap. 5. However, reactive
thermoplastic matrices (Nylon, PMMA, ABS, etc.) make a
reactive bond with natural fibres, yielding a good composite.
5 Hygroscopic Nature of Natural Fibres—Natural fibres require
adequate drying before processing with thermoplastic matrices. The moulding of thermoplastic composites is carried out
in closed moulds. (This has been discussed in more detail in
7 Chap. 7.) Therefore, there are remote possibilities for
moisture or entrapped gases to escape. The ingress of moisture
in the composite reduces its properties as well as its aesthetic
appearance.
5 Low Strength—The low strength of natural fibres restricts their
processability using filament winding, tape lay-up, or pultrusion methods.
5 Use of High-Temperature Matrices—Due to the low thermal
stability of natural fibres, their processability as reinforcement
in high-temperature matrices (PEI, PEEK, polyimides, etc.) is
not feasible.
6.9 · Processability of Thermoplastic Green Composites
6
thermal degradation of natural fibres. Rubberized cotton, which
was earlier used in bicycle tyres, is an apt example of a natural fibrereinforced polymeric ‘green’ composite.
? Example 6.6 Discuss specific applications of thermoplastic
green composites.
v Answer
Bamboo or coir fibre-reinforced polyethylenes and
polypropylenes are being used as door panels in civil
construction industries. Bamboo fibre-reinforced PLA is being
used for various applications for complete biodegradability.
However, the use of biodegradable fillers (such as starch or wood
flour) in conventional thermoplastic or thermosetting matrices
increases the scope of biodegradable matrices. It is to be noted that
the bulk density of natural fibres is quite high, and this makes their
weight percentage in the composite quite low.
True green composites are manufactured by reinforcing natural
fibres in biodegradable polymeric matrices, such as PLA, PCL, or
PGA. These fibres are thermoplastic in nature and can be processed
using various methods, as applicable to other thermoplastics. The
processability of biodegradable composites is carried out in a closed
mould processing. The processability parameters for biodegradable
composites are as follows.
6.9.1 Processability of Natural Fibre-Reinforced
Thermoplastic Matrix Composite
The processability of these composites is governed by the following
factors:
5 Interphase in the Composite—The hydrophilic nature of natural
fibres restricts their wetting by hydrophobic polymeric matrices, which has been discussed in 7 Chap. 5. However, reactive
thermoplastic matrices (Nylon, PMMA, ABS, etc.) make a
reactive bond with natural fibres, yielding a good composite.
5 Hygroscopic Nature of Natural Fibres—Natural fibres require
adequate drying before processing with thermoplastic matrices. The moulding of thermoplastic composites is carried out
in closed moulds. (This has been discussed in more detail in
7 Chap. 7.) Therefore, there are remote possibilities for
moisture or entrapped gases to escape. The ingress of moisture
in the composite reduces its properties as well as its aesthetic
appearance.
5 Low Strength—The low strength of natural fibres restricts their
processability using filament winding, tape lay-up, or pultrusion methods.
5 Use of High-Temperature Matrices—Due to the low thermal
stability of natural fibres, their processability as reinforcement
in high-temperature matrices (PEI, PEEK, polyimides, etc.) is
not feasible.
6.9 · Processability of Thermoplastic Green Composites