polymers and fibres
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what are polymers
large molecules with linked monomer units
what are 4 types of polymers
natural (biopolymers) semi-synthetic (cellophane) synthetic (polystyrene) co-polymers
what are 3 possible organisation of monomer units in co-polymers
random alternating graft co-polymers
what are some examples of linear co-polymers
PVC, polystyrene and nylon
what are some examples of cross linked co polymers
rubber. epxoy resin
what are some examples of branched polymer chains
LDPE, HDPE
What is a dendrimer
specialised polymers with branching points, core and termini
what are some characteristics of thermoplastics as synthetic polymers
hard at room temp, soft and viscous at higher temp which means they can be shaped and moulded
what is an example of thermoplastics
Polystyrene
what ae some characteristics of thermosetting polymers
on heating become highly cross-linked and cant be reshaped
what are 2 examples of thermosetting polymers
car top coats and bakelite
what is the classification of elastomers
• ability to stretch and return to original shape
what is an example of elastomers
rubber, tyres
what are fibres
thin threads
why are fibres important
for transfer and trace evidence used in homicide, assault cases etc.
what is a cellulose fibre
natural fibre
what are 3 characteristics of cellulose fibres
dicot fibre- - transparent - colourless -curve twisted fibres
what shape is the cross section of cellulose fibres
circular cross section with surface striations
what is an example of cellulose fibres
cotton (found in some clothing)
what are 3 characteristics of the natural fibre Kapok
seed fibre - smooth hollow thin walled cylinders - 2-3cm -surface irregularities and twisting and sharp bends
can natural fibres be synthetic or semi-synthetic
yes- can be both, can also be from minerals, animal and plant sources
what are kapok seed fibres used for
boyancy aids- they are brittle and inelastic
what is a flax (Linen) natural fibre, and what is its shape
Dicot fibre - transverse nodes shaped I, X, V and Y
What are some examples of flax fibres
• skin • vegetable