Polymers Flashcards
What are large molecules made of linked monomer units called?
Polymers
Examples of monomer units include vinyl chloride, styrene, and glucose.
What are the four types of polymers?
- Natural (biopolymers)
- Semi-synthetic polymers
- Synthetic Polymers
- Co-polymers
What is an example of a natural polymer?
Natural fibres, proteins, DNA
Examples include hemp and cotton.
What are Rayon fibres and cellophane classified as?
Semi-synthetic polymers
What are examples of synthetic polymers?
- PVC
- Polystyrene
- PTFE
- Nylon
What is a co-polymer?
A polymer made from different linker monomers
Example: Styrene (25%) and 1,3-butadiene.
What are the possible organisations of monomer units in co-polymers?
- Random co-polymers
- Alternating co-polymers
- Block co-polymers
- Graft co-polymers
What describes branched polymers?
Polymers with high or low branching
Example: Polyethylene (LDPE and HDPE).
What are cross-linked polymers?
Polymers where chains are interconnected
Examples: Poly (Isoprene) Rubber, Epoxy Resin.
What characterizes linear polymers?
Polymers with a straight chain structure
Examples: PVC, Polystyrene, Nylon.
What are dendrimers?
Specialised polymers engineered for specific uses
What is chain growth polymerisation?
A method of synthesizing most plastics
What are the three types of polymer classifications based on thermal properties?
- Thermoplastic
- Thermosetting
- Elastomer
What is a thermoplastic?
A polymer that is hard at room temperature and soft at higher temperatures
Examples: Polystyrene, polyethylene.
What happens to thermosetting polymers upon heating?
They become highly cross-linked and solidify
What is an elastomer?
A polymer that can stretch and return to its original shape
Example: Rubber.
What are fibres?
Thin threads
Why are fibres important in forensic analysis?
They represent the largest category of polymer evidence analysed
What are the classifications of fibres?
- Natural
- Semi-synthetic
- Synthetic
What are cellulose fibres primarily composed of?
Cellulose
Example: Cotton fibres are made up of 90% cellulose.
What are dicot fibres?
Fibres that come from a plant with two seed leaves
What are characteristics of Kapok fibres?
- Smooth
- Hollow
- Buoyant
- Non-allergenic
Which fibre is known for being stronger than cotton?
Flax (linen)
What are the primary and secondary types of hemp fibres?
- Primary Bast Fibres (70%)
- Secondary Bast Fibres (30%)
What characterizes ramie fibres?
Long, glossy, naturally white and silky appearance
What are the general characteristics of synthetic fibres?
No surface characteristics and regular uniform shape
What is Nylon made from?
6-aminohexanoic acid
What are Kevlar fibres used for?
Bulletproof vests and other protective gear
What are the properties of semi-synthetic fibres?
Regenerated forms of cellulose
How are rayon fibres produced?
Extraction from wood pulp or cotton and treated with a strong base
