Plastics Flashcards
What is the fundamental building block of plastics?
Carbon
What are synthetic plastics made from?
Crude oil
What is the single repeated unit that make up a plastic?
a monomer
What process happens to monomers to transform them to polymers?
Polymerisation
How are plastic properties altered?
Additives added to the polymers
name some manufacturing processed used in the manufacture of plastics
extrusion
injection moulding
compression moulding
What was the first synthetic plastic and when was it produced?
Bakelite in 1907
What type of chemical bonding is prevalent in plastics?
covalent
What must an organic molecule contain?
carbon
What are the main types of hydrocarbons in crude oil?
Alkanes, Aromatics, cycloalkanes, alkenes, alkynes
Give an example of an alkane
methane, ethane, propane, butane, isobutane, pentane, hexane
Give an example of an aromatic
benzene, napthalene
Give an example of a cycloalkane
Cyclohexane, methyl cyclopentane
Give an example of alkene
ethylene, butene, isobutene
Give an example of an alkyne
actylene, butadienes
How are hydrocarbons refined?
fractional distillation
What are the monomers for PTFE, PVC and PP?
PTFE : 2 flourine per carbon
PVC: 2 hydrogen on one carbon and a hydrogen and a cholrine on the other
PP: 2 hydrogen on one carbon and a hydrogen and a methyl group on the other
What is the microstructure of a polymer like?
Can be chrystalline or amorphous
Have chrystalline and amorphous regions (semi chrystalline)
amount of chrystal phase changes properties
What are the 2 different classes of polymers
Thermoplastics
Thermosetting plastics
What are the properties of a thermoplastic?
Become soft and melt when heated
Can be moulded into a new shape that is retained on cooling
Can be reheated and remouled many times
Have plastic memory
What are the properties of a thermosetting plastic?
- Set when first cooled down
- will not soften when reheated
- plastic will be destroyed before melted
What allows the thermoplastics to be remoulded when heated?
They can be straight chain or branched chain, but they are held together by weak intermolecular bonding
What are the effect of side chains on the properties of thermoplastics?
Side chains increase the distance between the main CC chain, this reduces the intermolecular attraction and results in different properties
Give an example of how branches affect the properties of hydrocarbons
Low density polyethylene
High density poly ethylene (shorter branches)
What makes a thermosetting plastic so strong?
They have networked covalent bonding and are cross linked with covalent bonding between chains
Give an example of a thermosetting plastic
Bakelite, Phenolics, various epoxy resins and polyesters
What is a polymer that is made form one or more polymer called?
A copolymer
What are the different types of polymers?
Random
Alternating
Block
Graft
All of these give you different properties
What are the general properties of polymers?
- Combustible
- Low melting point
- Low solubility in water
- High molecular
- Variable molecule size
- Low compressive strength
- Low stiffness
- High toughness
- Low density
- Durable
- Softens at low temperatures
- Low thermal conductivity
- Electrical insulators
- Low permeability
- Flexible
- Available in many forms
How much plastic is produced per year worldwide?
~300 million tonnes
How much is plastic consumption growing by in europe?
4% per year
How much of the plastic produced per year is used in construction, and how much in packaging?
1/3 in packaging, 1/4 in construction
What are some examples of high volume plastics?
Polyethylene (PE): containers , pipes, bags…
Polyvinylchloride (PVC): windowframes, pipes, flooring
Polypropylene (pp): film, chairs, fibres, car bumpers
Polystyrene (PS): packaging, thermal insulation, cups
Polyethylene tetrephthalate (PET): bottles, film, food packaging
Polyurethane (PU): adhesives, trainer soles, furniture foam
Acrylonitrile butadiene styrene (ABS): transparent all-weather sheet, electrical insulators
What % of plastics are used in the construction sector?
23%
Describe the process behind injection moulding?
Ram pushes plastic into a screw in a barrallel, where plastic granules are fed across heaters through a nozzle.
Molten plastic is fed into a mold, where it is then ejected and the part is formed
What are the signature features of injection moulding?
An injection and ejection points
What is the process behng compression molding?
Thermoset or thermoplastic charge is placed in mold
The mold has a plunger at the bottom which ejects it after molding
How is plastic used in construction?
Plastics in construction are used for pipes and ducts. Nearly 30% are for insulation products, and the rest are for windows and floor coverings
What plastic is used in landfills?
HDPE, it is used as a landfill liner
LDPE is used as a landfill cover
What is the main plastic used in construction?
PVC
What is bitumen produced from?
Crude oil during fractional distillation
It is the heaviest fraction with the highest boiling point >370C
Can also be found in natural deposits
What kind of plastic is bitumen?
Thermoplastic
What benefitial properties does bitumen have?
Waterproofing and adhesive
What are the main chemical groups in bitumen
Asphaltenes and maltenes
exact composition depends on the crude oil and distiallation process
What are the three different types of maltenes?
resins, aromatics and saturates
Why is bitumen such a good binder for asphalt?
Bitumen can either actaas a straight forward binder, or its properties can be used depending on the ratio of aggregates to bitumen
