144
5
posites. For high-temperature applications, polyimides (PI) have
a distinct place. A range of polyimides (such as bismaleimide,
polymeric monomer reactant–polyimide (PMR–PI), polyetherimide, polyamide imide, etc.) are being used commercially.
Nevertheless, the future of composite technology will greatly
depend upon the development of new technologies and the
improvement of reinforcements, matrices, and interphases.
Future technologies need research and development efforts for
their commercialization, especially the crystallization and
growth of polymeric matrices over a reinforcing fibre, selective
irradiation methods for creating a fibre structure in a neat matrix
in situ, automatic swelling of the matrix to minimize the air
pockets and gaps in the composites, etc. Chemically active reinforcements are responsible for the strong interphase in present
composites. If the surface is inert or less active, it needs to be
made chemically active, as described in the previous section.
However, the chemical activity needs further development and
characterization for inducing suitable and compatible linkages
(such as dipole interactions, hydrogen bonds, van der Waals
forces, ionic interactions, etc.) in order to optimize the bond
strengths along with its lability in the interphase [26].
Processing technologies (such as autoclaving, RTM, filament
winding, etc.) provide composites almost free of defects. Similarly,
filament winding technology, tape winding technology, etc. are
used for a high orientation of reinforcement.
5.5 Processability of Thermosetting
‘Green Composites’
Green composites are those which do not cause any harm to the
environment during both their processing and the product disposal
after the useful life is over. Given this classification, major composites are those that use natural fibres as reinforcements and/or
biodegradable matrices. Green composites have created interest
worldwide due to their environment friendliness. These composites
are not new. In fact, mankind’s knowledge of green composites has
existed from time immemorial. In ancient times, straw- or bambooreinforced mud houses were built (as mentioned in 7 Chap. 1).
More recently, natural fibres (such as sunn, coir, jute, etc.) have
been used as reinforcement in the construction of buildings. The
densities of these fibres are in the range of 1.15–1.55 g/cm 3 , which
supports their processability using common processes and the
development of matrices that are processable within the limit of
thermal degradation of natural fibres. Rubberized cotton, which
historically has been used in bicycle tyres, is an apt example of a
natural fibre-reinforced polymeric composite.
? Example 5.3 Cast some light on green composites with their
specific applications
Point to Ponder…
Bulk density is the mass of
aggregate of material (in the form
of bunch, bundle, powder, etc.)
per unit volume. It is not intrinsic
property of a material.
Chapter 5 · Processability of Thermosetting Composites
5
posites. For high-temperature applications, polyimides (PI) have
a distinct place. A range of polyimides (such as bismaleimide,
polymeric monomer reactant–polyimide (PMR–PI), polyetherimide, polyamide imide, etc.) are being used commercially.
Nevertheless, the future of composite technology will greatly
depend upon the development of new technologies and the
improvement of reinforcements, matrices, and interphases.
Future technologies need research and development efforts for
their commercialization, especially the crystallization and
growth of polymeric matrices over a reinforcing fibre, selective
irradiation methods for creating a fibre structure in a neat matrix
in situ, automatic swelling of the matrix to minimize the air
pockets and gaps in the composites, etc. Chemically active reinforcements are responsible for the strong interphase in present
composites. If the surface is inert or less active, it needs to be
made chemically active, as described in the previous section.
However, the chemical activity needs further development and
characterization for inducing suitable and compatible linkages
(such as dipole interactions, hydrogen bonds, van der Waals
forces, ionic interactions, etc.) in order to optimize the bond
strengths along with its lability in the interphase [26].
Processing technologies (such as autoclaving, RTM, filament
winding, etc.) provide composites almost free of defects. Similarly,
filament winding technology, tape winding technology, etc. are
used for a high orientation of reinforcement.
5.5 Processability of Thermosetting
‘Green Composites’
Green composites are those which do not cause any harm to the
environment during both their processing and the product disposal
after the useful life is over. Given this classification, major composites are those that use natural fibres as reinforcements and/or
biodegradable matrices. Green composites have created interest
worldwide due to their environment friendliness. These composites
are not new. In fact, mankind’s knowledge of green composites has
existed from time immemorial. In ancient times, straw- or bambooreinforced mud houses were built (as mentioned in 7 Chap. 1).
More recently, natural fibres (such as sunn, coir, jute, etc.) have
been used as reinforcement in the construction of buildings. The
densities of these fibres are in the range of 1.15–1.55 g/cm 3 , which
supports their processability using common processes and the
development of matrices that are processable within the limit of
thermal degradation of natural fibres. Rubberized cotton, which
historically has been used in bicycle tyres, is an apt example of a
natural fibre-reinforced polymeric composite.
? Example 5.3 Cast some light on green composites with their
specific applications
Point to Ponder…
Bulk density is the mass of
aggregate of material (in the form
of bunch, bundle, powder, etc.)
per unit volume. It is not intrinsic
property of a material.
Chapter 5 · Processability of Thermosetting Composites