Polymers

Thermoforming Polymer

A polymer without cross links, allowing it to melt when heated.

Thermosetting polymer

A polymer that has cross links, preventing it from melting. They are heat resistant, so used as insulators.

Example of thermoforming polymers

LDPE (low density polyethylene), HDPE (high density polyethylene), ABS, acrylic, nylon

Examples of thermosetting polymers

Epoxy resin, Bakelite, Urea Formaldehyde, Melamine formaldehyde

Product lifecycle of a polymer

Extracted crude oil is fractionally distilled to separate it into different oils - cracked and formed into the stock form - formed into product and mixed with additives - used as a product, - recycled or thrown into landfill

Fractional distillation

Crude oil is heated to evaporate it into its separate fractions with lighter molecules at the top and heavier molecules at the bottom.

Biopolymer

A plant based polymer that degrades when placed into the natural world

Examples of biopolymers

PLA, PBS, chitting, cellulose, starch based polymers (potatopak)

Disadvantages of biopolymers

Release microplastics, cannot be recycled, release methane when in landfill, wear down quickly, expensive to set up

Key features of an injection mould

2 parts to each mould, highly polished injection surface with strong surround

Mould flow analysis

Simulates how the plastic with flow around the mould, showing the total volume of plastic needed

Elastomer

A polymer that can be deformed and when released, will return to its original shape

Example of elastomers

Natural rubber, butadine rubber, neoprene and silicone

Plasticiser

Improve flexibility and softness - phthalates

Fillers

Improve properties and reduce costs - glass fibres

Stabilisers

Protect against degradation - UV stabilisers

Flame retardants

Reduce flammability - brominated compounds

Pigments

Change colours - titanium dioxide

Lubricants

Reduce friction during and after manufacture - waxes and silicone

Antistatics

Reduce static electricity build up - Carbon black

Biodegradable additive

Encourage natural degradation - cornstarch additive

1 - Vacuum forming

Precise mould is placed in the centre of the machine

2 - Vacuum forming

Sheet of polymer is placed above mould

3 - Vacuum forming

Heater warms up polymer sheet from above to make it pliable and flexible

4 - Vacuum forming

Shelf with mould is lifted up into polymer while air is pumped out from the area below the plastic mould, pulling the polymer onto it

1 - Thermoforming

Plastic sheet is held between positive and negative moulds

2 - Thermoforming

The sheet is heated from all sides to make it pliable and flexible

3 - Thermoforming

Positive mould is moved downwards into the negative mould as the vacuum is applied, trapping the softened polymer until it has cured and hardened

1 - Calendaring

Polymer is heated up to make it pliable and flexible

2 - Calendaring

Polymer is fed between two rotating main calendars to press it to a rough thickness

3 - Calendaring

Polymer is rolled through more rollers to final thickness, final rollers decide surface finish

1 - Line bending

Thin polymer is laid onto machine

2 - Line bending

Heated wire softens the polymer above

3 - Line bending

Polymer is bent to a specific angle at the softened area and left to cool