Synthetic Fibre
Definition
Fibre manufactured from regenerated cellulose (rayon, acetate) or polymer chemistry (nylon, polyester, acrylic, polypropylene, spandex, kevlar). Identified by birefringence, FTIR and pyrolysis GC-MS.
- Regenerated cellulose types
- Rayon, acetate
- Polymer types
- Nylon, polyester, acrylic, polypropylene, spandex, kevlar
- Identification methods
- Birefringence, FTIR, pyrolysis GC-MS
- Evidence class
- Trace evidence (transfer and comparison)
Common questions
Why do examiners run both microscopic and chemical tests on a synthetic fibre rather than one method alone?+
Microscopy under polarised light gives birefringence and cross-sectional shape that narrow the fibre to a class quickly and non-destructively, while FTIR and pyrolysis GC-MS provide chemical composition that can distinguish polymer subtypes microscopy alone cannot separate, so the methods are complementary rather than redundant.
Can synthetic fibre analysis individualise a fibre to one specific garment?+
Rarely to a single garment; mass-produced synthetic fibres from the same production batch share physical and chemical properties, so the analysis usually supports class-level association, with strength depending on how uncommon the fibre type, colour, and cross-section combination is.
Why does polypropylene often need different handling from nylon or polyester during examination?+
Polypropylene has a lower melting point and different thermal degradation behaviour than nylon or polyester, so pyrolysis GC-MS parameters and comparison standards must be matched to the specific polymer class to get a reliable spectral comparison.
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