175
6
adaptability to different processing technologies. Composites from
biodegradable matrices do not pose any problem from degradation
due to moisture or high temperature. However, some of the parameters that govern their processability are given here:
5 Brittleness of Biodegradable Polymers—PLA is quite brittle;
therefore, the processability of its thin section is difficult. Thin
composite sections tend to break at low shocks that are
encountered in an injection moulding process.
5 High Cost of Biodegradable Polymers—The cost of processing
biodegradable polymers is quite high in comparison to their
thermoplastic counterparts. This restricts their use in many
common applications, as mentioned in 7 Sect. 5.5.
5 Durability—The durability of natural fibre-reinforced biodegradable composites is limited by the durability of the biodegradable polymer in the operating environment, as mentioned
in 7 Sect. 5.5.
To Be Remembered
1. Thermoplastic matrices are always solid to start with.
2. Thermoplastic matrices are not processed at room temperature; they are only processed at high temperatures.
3. The melt viscosities of thermoplastic matrices are higher
when compared to thermosetting matrices.
4. Spectra fibres are not chemically treated and are transformed into composites with low-temperature matrices.
5. Moulding of thermoplastic composites does not involve any
curing methods. Rather, it involves the melting of the
matrix and its solidification as a function of heat.
6. Intimate contact takes place between the reinforcement
and the matrix, whereas autohesion is coalescence within
the matrix in thermoplastic composites.
7. Melt viscosity of thermoplastic matrices only ensures the
percolation of the matrix around the reinforcement.
8. High MFIs indicate a low viscosity of the matrix.
9. Short fibres, particles, and whiskers are used as reinforcement in an injection moulding process.
10. All of the forms of reinforcement (fibres, fabrics, particles,
whiskers, staples, etc.) could be used in compression
moulding processes.
11. The major processes for making thermoplastic composites
are injection, compression, and pressure bag moulding.
12. Thermoplastic prepreg rovings and tows are being used for
filament winding process.
13. Nylon has sharp melting point due to its high crystallinity.
14. PEEK and PEI are mostly used for high-temperature
thermoplastic matrices.
15. PEEK is a chemically resistant thermoplastic—except when
used with concentrated sulfuric acid.
16. PP is the least dense thermoplastic matrix used in thermoplastic composites.
6.9 · Processability of Thermoplastic Green Composites
6
adaptability to different processing technologies. Composites from
biodegradable matrices do not pose any problem from degradation
due to moisture or high temperature. However, some of the parameters that govern their processability are given here:
5 Brittleness of Biodegradable Polymers—PLA is quite brittle;
therefore, the processability of its thin section is difficult. Thin
composite sections tend to break at low shocks that are
encountered in an injection moulding process.
5 High Cost of Biodegradable Polymers—The cost of processing
biodegradable polymers is quite high in comparison to their
thermoplastic counterparts. This restricts their use in many
common applications, as mentioned in 7 Sect. 5.5.
5 Durability—The durability of natural fibre-reinforced biodegradable composites is limited by the durability of the biodegradable polymer in the operating environment, as mentioned
in 7 Sect. 5.5.
To Be Remembered
1. Thermoplastic matrices are always solid to start with.
2. Thermoplastic matrices are not processed at room temperature; they are only processed at high temperatures.
3. The melt viscosities of thermoplastic matrices are higher
when compared to thermosetting matrices.
4. Spectra fibres are not chemically treated and are transformed into composites with low-temperature matrices.
5. Moulding of thermoplastic composites does not involve any
curing methods. Rather, it involves the melting of the
matrix and its solidification as a function of heat.
6. Intimate contact takes place between the reinforcement
and the matrix, whereas autohesion is coalescence within
the matrix in thermoplastic composites.
7. Melt viscosity of thermoplastic matrices only ensures the
percolation of the matrix around the reinforcement.
8. High MFIs indicate a low viscosity of the matrix.
9. Short fibres, particles, and whiskers are used as reinforcement in an injection moulding process.
10. All of the forms of reinforcement (fibres, fabrics, particles,
whiskers, staples, etc.) could be used in compression
moulding processes.
11. The major processes for making thermoplastic composites
are injection, compression, and pressure bag moulding.
12. Thermoplastic prepreg rovings and tows are being used for
filament winding process.
13. Nylon has sharp melting point due to its high crystallinity.
14. PEEK and PEI are mostly used for high-temperature
thermoplastic matrices.
15. PEEK is a chemically resistant thermoplastic—except when
used with concentrated sulfuric acid.
16. PP is the least dense thermoplastic matrix used in thermoplastic composites.
6.9 · Processability of Thermoplastic Green Composites