Polymers and fibres Flashcards
What are fibres made up of?
Polymers
What are polymers?
-Large molecules
-Linked monomer units
What are example of polymers?
-Vinyl chloride
-Styrene
-Glucose
What is the process of joining polymers together?
Polymerisation
What is a natural polymer?
Natural fibres
e.g. hemp or cotton, proteins, DNA
What are semi-synthetic polymers
Part natural, part man-made
e.g. Rayon fibres and cellophane
What are synthetic polymers?
Man-made
e.g. plastics: PVC, polystyrene, PTFE and nylon
What are co-polymers?
-Very large molecules
-Different linker monomers
e.g. styrene and 1,3-butadiene
What is a random co-polymer?
Monomer units organise themselves in a random fashion
What are alternating co-polymers?
monomer units organise themselves in an alternating fashion
What are block co-polymers?
Monomer units organise themselves into blocks
What are graft co-polymers?
Long chain of a single monomer unit, with branches of other monomer units grafted on
What are branched polymer chains?
Main chain with branches/side chains attached
What is an example of a branched polymer chain?
Polyethylene, low density = high degree of branching
What does a high degree of branching produce in polymer chains?
High flexibility
What are flexible polymers used to produce?
Films
What are non-flexible polymers used to produce?
Stiffer plastics used in bottles
What is a cross linked polymer chain?
Linear chains which are joined together by small vertical chains at random positions along the main chain
What is an example of a cross linked polymer chain?
-Poly(isoprene) rubber
-Epoxy resin (glue)
What is a linear polymer chain?
Most common
Chains in a linear fashion
What is an example of a linear polymer chain?
-PVC
-Polystyrene
-Nylon
What is a dendrimer polymer chain?
Only used in specialised polymers, which have specific uses.
Every unit is branched
What does chain growth polymerisation produce?
Makes plastics
What does cationic polymerisation produce?
Bicycle tubes
What does anionic polymerisation produce?
Superglue fuming for fingerprints
What does step growth polymerisation produce?
Nylon
What is step growth polymerisation further classified into?
-Thermoplastic
-Thermosetting
-Elastomers
What is thermoplastic polymerisation?
-High glass temperature
-Hard at room temp
-Soft when heated
e.g. Lego
What is thermosetting polymerisation?
-Heated produces extensive 3D linkage
-Highly cross linked
-Solidifies and can’t be reshaped or remoulded
What does thermosetting polymerisation produce?
A hard, single, large molecule
Inflexible and can crack
e.g. Bakelite
What is elastomer polymerisation?
-Ability to stretch and return to the original shape due to weak van der whal forces
e.g. rubber, tires
What are fibres?
-Thin threads of molten polymer extruded through a spinneret
-Then cooled and drawn out along the axis of the fibre to give strength
What are the classifications of natural fibres?
-Animal
-Plant source
-Mineral
What is cellulose?
-A natural fibre
-Large polymer unit made from glucose monomer units
What are glucose units in cellulose held together by?
Hydrogen bonds
What is a dicot fibre?
Has 2 seed leaves
How does cellulose look under the microscope?
-Transparent
-Colourless
-Curved twisted fibres
-Surface striations
-Circular cross section
What is kapok?
A seed fibre
What do kapok fibres look like?
-Smooth
-Hollow
-Thin walled cylinders
-Twisting and sharp bending
-Silky like substance
What are kapok fibres used for?
A stuffing agent
Fibres are brittle and inelastic and can’t be spun into fabric
What are flax fibres?
-Dicot fibres
-Skin fibres
-High cellulose conc
-Stronger than cotton
What are hemp fibres?
-Dicot fibres
-Comes from cannabis plant
How do hemp fibres appear?
-Colourless
-Transparent cylinders
-Surface irregularities
-Polygonal cross section
What do synthetic fibres contain?
One polymer
What are bicomponent fibres?
Contains 2 different polymers
What are the general characteristics of bicomponent fibres?
-No surface characteristics
-Regular and uniform shape
-Can’t be identified under microscope when comparing 2 fibres
What is a nylon?
A step-growth polymer
What does nylon consist of?
It’s a molecule with an amine group on one end of the molecule and a carboxylic acid one another
What is nylon used in?
Carpets
Seatbelts
What is kevlar?
The strongest synthetic fibre
What does kevlar consist of?
monomer units are aramids, due to benzene ring
Linked by hydrogen bonds
What is kevlar used in?
Bulletproof vests
Army uniforms
What gives kevlar it’s strength?
Network of hydrogen bonds
What are semi-synthetic fibres?
Regenerated forms of cellulose
What are rayon fibres?
Semi-synthetic fibres extracted from wood or cotton
