1.4 Polymers

What are the three main categories of polymers?

Thermoplastic

Thermosetting

Elastomers

What are polymers made up of?

long chain molecules containing carbon, hydrogen and oxygen atoms, along with other chemicals such as chlorine and fluorine.

Where can you find polymers naturally?

from plant and animal sources.

They include Casein (derived from milk) which is still used to make buttons, Horn, Resin (from trees) and Cellulose from plants. In the case of Cellulose it is mixed with acetic acid to make Cellulose acetate

What are the main source of synthetic polymers?

Fossil fuels:

oil, gas and coal

How do you get synthetic polymers?

gained through a process of thermal cracking. As they are derived from fossil fuels (particularly oil) they are carbon based and account for the majority of plastics used today.

In order for it to be useful to us, crude oil is broken down in oil refineries into its component parts, known as fractions, and these can then be used for many different purposes.

Fractions that are produced by the distillation of crude oil can go through a process called cracking. This chemical reaction produces smaller hydrocarbons, including alkanes and alkenes. Ethene and other alkenes are unsaturated hydrocarbons and can be used to make polymers. Ethene can be used to make ethanol.

What are thermoplastics

•A plastic that can be repeatedly reheated and remoulded. Therefore these types of plastics can be recycled

When heated, the long chain molecules become flexible allowing the material to be reshaped. When cooled they become rigid again giving a solid material.

No links between polymer chains, helps movement

Name the thermoplastics

Polyethylene terephthalate (PET)

Low density polyethylene (LDPE)

High density polyethylene (HDPE)

Polypropylene (PP)

High Impact Polystyrene (HIPS)

Polymethyl-methacrylate (PMMA) (Acrylic)

Polyamide (Nylon)

Acrylonitrile butadiene styrene (ABS)

Rigid polyvinyl chloride (uPVC)

Flexible polyvinyl chloride (PVC)

Properties and applications of polyethylene terephtalate (PET)

Clear, flexible, tough and lightweight

Single use plastic bottles, food packaging

Properties and applications of low density polyethylene (LDPE)

Very tough, good chemical resistance, weatherproof

Squeezy detergent bottles, carrier bags, food wrap film

Properties and applications of High density polyethylene (HDPE)

Weatherproof, tough, good chemical resistance

Chemical drums, buckets, bowls

Properties and applications of Polypropylene (PP)

Good chemical resistance, good fatigue resistance (hinge property)

Rope, folio cases, medical equipment, chair shells, hinged container lids

Properties and applications High Impact Polystyrene (HIPS)

Hard, rigid, tough

Yoghurt pots, fridge linings, drink cups, toilet seats

Properties and applications Polymethyl-methacrylate (PMMA) (Acrylic)

Tough, hard, available transparent or translucent

Car headlights, lighting units, baths

Properties and applications Polyamide (Nylon)

Low friction, tough, good chemical resistance

Bearings, gears, combs and brushes

Properties and applications Acrylonitrile butadiene styrene (ABS)

Extremely tough, hard, good heat resistance

Telephone handsets, computer casings, electrical item casings

Properties and applications Rigid polyvinyl chloride (uPVC

Extremely tough, hard, good heat resistance

Telephone handsets, computer casings, electrical item casings

Properties an applications Flexible polyvinyl chloride (PVC)

Tough, flexible, good chemical resistance

Hose pipes, cable insulation, fake leather

What are thermosetting polymers?

polymers that cannot be reheated and reshaped. When the plastic is formed cross linking takes place across the long chain molecules which cannot be broken down by heat. While this means these types of plastic are good for situations where they will be subjected to heat and electricity, these types of plastics cannot be recycled.

Links between polymer chains stops movement between them

Name the thermosetting polymers

polyester resin, epoxy resin, urea formaldehyde and melamine formaldehyde

Properties and applications of urea formaldehyde

Hard, heat resistant, good electrical insulator, brittle

Electrical fittings, adhesives

Properties and applications of Melamine Formaldehyde

Hard, opaque, heat resistant, food safe, chemical resistance

Decorative laminates, picnic ware, buttons

Properties and applications of polyester resin

Rigid, heat resistant, chemical resistance, brittle

Castings, used in GRP

Properties and applications of epoxy resin

Rigid, clear, hard, tough, chemical resistant

Adhesives, surface coatings, encapsulation of electrical components, used in CFRP

What are elastomers

These are polymers with good elasticity i.e. they can be distorted under pressure but will return to their original shape.