Polymers Flashcards
What are synthetic plastics manufactured from
Crude oil
How are plastics made from carbon polymers
Adding various additives
What are some ways to form plastic into different shapes
injection moulding, compression moulding and extrusion
What was and when was the first plastic made and what type of plastic was it
Bakelite 1907, thermosetting plastic
What is the percentages of different groups of hydrocarbons in crude oil
aliphatics (25%), aromatics (17%) and naphthenes/
cycloalkanes (50%)
What non hydrocarbon groups does crude oil contain
sulphur, nitrogen, oxygen and metallics
Why do isoalkanes have a lower boiling point than normal alkanes
isoalkanes ,which are branched, increase the distance between two neighbouring alkane groups and decreases the surface area in which the two groups can interact so the intermolecular forces are weaker, meaning less energy is required to separate these molecules
What percentage of crude oil is used for plastic manufacture
2.7%
What are thermoplastics and describe its bonding + structure
Plastics that soften when heated and will set when cooled. This can be repeated, in a process of reheating and remoulding. Formed from polymers held together by weak IMFs.
What are thermosetting plastics
Plastics that set when first cooled down but will not soften when reheated. Therefore cannot be remoulded and will burn when too much heat is applied. Formed from polymers with covalent bonds between them
What gives plastics their plasticity
The fact that the polymers can move over each other when a load is applied. (no dislocations like in metals)
What are copolymers and what are the four types
Polymers made from more than one monomer - random, alternating, block (consists of sections containing one type of monomer), graft (contains monomer sections that are attached to a chain of a different monomer)
General properties of polymers
Combustible, low melting point, low solubility in water, high molecular weight, variable molecule size, low compressive strength, low stiffness, high toughness, low density, durable, low thermal conductivity, electrical insulators, low permeability, flexible
How much plastic by percentage is used for building and construction
23%, second largest sector behind packaging
give examples of additives
plasticisers (adds flexibility), antioxidants, pigments, fillers
How does extrusion form plastic into certain shapes
Plastic granules are fed into a hopper which leads to a screw. The screw heats and squeezes the plastic, melting it. The melt is then passed into a die to form the desired shape
How does injection form plastic into certain shapes
Plastic granules are fed into a hopper which leads to a screw. The screw heats and squeezes the plastic, melting it, which is then injected into a mould
How does compression moulding form plastic into certain shapes
The plastic sheet or block is squished by compression into the desired shape
What is the main plastic in construction
PVC
How is HDPE used in landfills
It is used as a flexible, protective liner from leachate
What type of plastic is polyethylene and what is it made from
thermoplastic, contains hydrogen and carbon and no oxygen because it is formed from ethene monomers
What is the main use of bitumen is civil engineering
The binder of asphalt
Properties of bitumen
softens when heated, is a viscous liquid , formed from the heaviest oil fraction in crude oil, black, excellent waterproofing and adhesive properties
what happens to the viscosity of bitumen with temperature
Increases when cooled down
What happens when the bitumen content in asphalt filling is too high or too low
Too high and the properties of bitumen dominate over the aggregate, too little and the aggregates dont bind (this can be used to make porous asphalt, for drainage)
