153
6
The basic principles of processability and the factors affecting it do
not change much from thermosetting composites to thermoplastic
composites. However, the processability factors, which have a profound effect on the processing of thermoplastic composites, are
mentioned here.
5 Thermoplastic matrices are generally solid to start with.
5 Thermoplastic composites are not processed at room temperature but only at high temperatures.
5 Thermoplastic composites have melt viscosities that are higher
than those compared to thermosetting matrices.
5 Thermoplastic composites are categorized as crystalline, such
as nylon; semi-crystalline, such as polyether ether ketone
(PEEK), polyethylene (PE), and polypropylene (PP); and
amorphous, such as polyether imide (PEI), polymethyl
methacrylate (PMMA), and polycarbonate (PC) in nature.
Thermoplastic composites are easily recycled; therefore, they are
finding many applications in composite industries [1, 2]. They are
easily blendable, and no additive or hardener (like in the case of
thermosetting matrices) is required to solidify or cure the thermoplastic composites. The ability of thermoplastic composites to repair
through welding is also an advantage. However, the downside is
that its mould designs are complex and heavy processing machines
are required.
This chapter delves in detail for better insight on the processability of thermoplastic composites.
6.1 Interface and Interphase in Thermoplastic
Composites
The concepts of interphase and interface are discussed in 7 Chap. 5
and remain same for thermoplastic composites. Olefinic matrices
are often inert. Polypropylene (PP), low-density polyethylene
(LDPE), high-density polyethylene (HDPE), etc. are chemically
inert, and they each can form a bond with the reinforcement with
great difficulty. Special treatments on fibres are carried out in order
to improve the bonding between the reinforcement and the thermoplastic matrix. Thermoplastic fibres (PEEK, nylon, polyester,
polyurethane (PU), etc.) are chemically active and make a good
interfacial bond with reinforcements. Their fibres are also chemically active—except for ultra-high molecular weight polyethylene
(UHMWPE) fibre. UHMWPE fibres are not treated with any chemical and are transformed into composites that have low-temperature
matrices that are compatible with polyethylene. The matrices used
for UHMWPE fibres are low-temperature elastomers and polyolefins (polyethylene and polypropylene). The interfacial bond made
by these fibres is a secondary bond, such as found in Van der Waals
interactions [3, 4].
6.1 · Interface and Interphase in Thermoplastic Composites
6
The basic principles of processability and the factors affecting it do
not change much from thermosetting composites to thermoplastic
composites. However, the processability factors, which have a profound effect on the processing of thermoplastic composites, are
mentioned here.
5 Thermoplastic matrices are generally solid to start with.
5 Thermoplastic composites are not processed at room temperature but only at high temperatures.
5 Thermoplastic composites have melt viscosities that are higher
than those compared to thermosetting matrices.
5 Thermoplastic composites are categorized as crystalline, such
as nylon; semi-crystalline, such as polyether ether ketone
(PEEK), polyethylene (PE), and polypropylene (PP); and
amorphous, such as polyether imide (PEI), polymethyl
methacrylate (PMMA), and polycarbonate (PC) in nature.
Thermoplastic composites are easily recycled; therefore, they are
finding many applications in composite industries [1, 2]. They are
easily blendable, and no additive or hardener (like in the case of
thermosetting matrices) is required to solidify or cure the thermoplastic composites. The ability of thermoplastic composites to repair
through welding is also an advantage. However, the downside is
that its mould designs are complex and heavy processing machines
are required.
This chapter delves in detail for better insight on the processability of thermoplastic composites.
6.1 Interface and Interphase in Thermoplastic
Composites
The concepts of interphase and interface are discussed in 7 Chap. 5
and remain same for thermoplastic composites. Olefinic matrices
are often inert. Polypropylene (PP), low-density polyethylene
(LDPE), high-density polyethylene (HDPE), etc. are chemically
inert, and they each can form a bond with the reinforcement with
great difficulty. Special treatments on fibres are carried out in order
to improve the bonding between the reinforcement and the thermoplastic matrix. Thermoplastic fibres (PEEK, nylon, polyester,
polyurethane (PU), etc.) are chemically active and make a good
interfacial bond with reinforcements. Their fibres are also chemically active—except for ultra-high molecular weight polyethylene
(UHMWPE) fibre. UHMWPE fibres are not treated with any chemical and are transformed into composites that have low-temperature
matrices that are compatible with polyethylene. The matrices used
for UHMWPE fibres are low-temperature elastomers and polyolefins (polyethylene and polypropylene). The interfacial bond made
by these fibres is a secondary bond, such as found in Van der Waals
interactions [3, 4].
6.1 · Interface and Interphase in Thermoplastic Composites