| dc.description.abstract | Composites are normally composed of two distinct phases: reinforcement and matrix. In
recent years, a new class of “self-reinforced” polymer composites or “all-polymer”
composites, which are based on similar or identical materials for both reinforcement and
matrix have generated increasing interests in both academia and industries due to their
advantages in terms of processing, interfacial properties and recyclability. Current research
trend in this field is to investigate the potential possibilities of all-polymer composites
based on high-performance polymer fibres. In this thesis, all-poly(ethylene terephthalate)
composites (Part 1) and all-aramid composites (Part 2) were prepared. In Part 1, Chapter 3
describes the melt spinning and drawing of poly(ethylene terephthalate) (PET) into highly
oriented fibres, with moduli of 20GPa and tensile strengths of 925MPa. The effects of
spinning and drawing conditions on the mechanical properties of PET fibres were studied.
In the following Chapters 4 and 5, all-PET composites were prepared from 1) hot
compaction of bi-component multifilament PET yarns; and 2) a film stacking technique, i.e.
combining PET tapes unidirectionally with copolyester adhesive films in an alternating
“brick-wall” layer-by-layer structure. The effects of processing conditions on mechanical
properties were investigated. In Part 2 Chapter 7, all-aramid composites were prepared by
a selective surface dissolution method where aramid fibres were partially dissolved to form
a matrix phase to bond remaining fibres together into composites. The structure,
morphology and mechanical properties were characterized by X-ray diffraction, scanning
electronic microscopy, dynamic mechanical analysis and tensile testing. Compared to
traditional aramid/epoxy composites, these all-aramid composites show significantly high
mechanical properties, even at elevated temperatures. In Chapter 8, the effects of
processing conditions on various properties of all-aramid composites were studied and an
optimum condition was found. By replacing high concentration sulphuric acid as a solvent,
a mild mixed solvent was used to dissolve aramid fibre surfaces in Chapter 9. In this way,
all-aramid composites with prolonged immersion times were prepared and characterized.
Potential future work including all-PET composites from post-consumer PET waste,
microstructural characterization of all-aramid composites and woven all-aramid
composites are discussed in Chapter 10. | en_US |
