© Boardworks Ltd 2005 1 of 31 Project on thermoplastics and thermosetting plastics Submitted by- Shubham Saxena Sneha S

© Boardworks Ltd 20051 of 31

Project on thermoplastics and thermosetting plastics

Submitted by- Shubham Saxena Sneha S


Learning objectives


Lea

rnin

g o

bje

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es To understand the differences between thermoplastic and thermosetting plastics.

To become familiar with the properties of different types of plastic, and know what each is typically used for.

To be aware of the origins of plastics and with the range of industrial processes used to manufacture plastic products.


Plastics

Formed by heat

Thermoplastic plastics:

Soften when heated

Can be reheated and reshaped

Mostly recyclable

Made of long polymer chains

with few cross links

There are two main groups of plastics:thermosetting plasticsthermoplastic plastics. What does the

word ‘plastic’ mean?

The word ‘plastic’ means ‘easily shaped or moulded’.


Initially set by heat

Thermosetting plastics:

Cannot be reshaped once set

Strong and durable Common in powder or resin forms

Consist of polymer chains with strong

bonds between each chain

What items do you have in your possession that are made of plastic? Are they made from thermoplastic

or thermosetting plastics?

Plastics


individual monomer molecule individual monomer molecule

Thermoplastic plastics are made of long chains of polymers which don’t cross over very often. When heated, the molecules slip easily over one another.

Thermosetting plastics also have lots of long chain molecules, but there are links between them. These cross links prevent the molecules from moving over one another.

Plastics

Which of these diagrams depicts a thermoplastic and which depicts a thermosetting plastic?


The majority of common plastics are thermoplastics.

Thermoplastics can be heated and reshaped because of the ways in which the molecules are joined together.

This can be repeated many times (as long as no damage is caused by overheating).

Heat

Cool

Harden Soften

Thermoplastic plastics


Thermoplastic plastics


They are heated and moulded during manufacture.

Once cooled, they will not soften again when heated. This breaks the potentially unending cycle that thermoplastic plastics are capable of.

If heated too much, they burn.

Thermosetting plastics are those which are set with heat and have little elasticity. Once set, they cannot be reheated and reformed.

Heat

Cool

Harden Soften

Burn

Thermosetting plastics


Here are some common products made from thermoplastics. Can you say which type of thermoplastic each one is made of?

Acrylic

High densitypolythene

ABS

Low density polythenePolypropylene

What other uses do these thermoplastics have?

Uses of plastics (thermoplastics)

Why do thermoplastics make good materials for these products?

Polystyrene


Thermosets have different qualities to thermoplastics. Can you say which thermoset each of these products is made from?

Melamine formaldehyde Urea

formaldehyde

GRP

Phenol formaldehyde

Epoxyresin

What other uses do these thermosets have?

Uses of plastics (thermosets)

Why are thermosets good materials for these particular products?


We obtain crude oil from under ground, either on land or at sea.

After it has been pumped, it is heated in a fractioning tower and broken down into chemicals.

The chemicals consist of nitrogen, carbon, chlorine, sulfur and water.

PumpPipeline

Oil well

Layers of rock

Gas

Oil

Oil - the raw material for plastics


Acrylic is available in many different colours.

These properties make acrylic ideal

for shop signs.

It is also used to make many outer cases for toys.

It comes in sheets or as round rods.

It can be softened and bent, blown or twisted into many different shapes.

Acrylic is stronger than glass, but scratches easily.

Acrylic can resist the weather very well.

Acrylic


Polystyrene foam can be easily shaped and is very light. This makes it suitable for modelling three-dimensional objects.

Which other uses for polystyrene can you think of?

Polystyrene foam


Bakelite was one of the first artificial plastics and was created in 1909 by Leo Baekeland.

It is used for telephones, radios and electrical equipment.

Bakelite is a hard, brittle plastic that has a natural dark glossy colour.

It resists heat without softening.

It is a good thermal insulator and a good electrical insulator.

When overheated, it burns and smells.

Bakelite – a very early plastic


Melamine plastics have similar properties to Bakelite. However, they have the added advantage of being able to be coloured during processing.

Melamine formaldehyde and urea formaldehyde are two types of melamine plastics.

Melamine

Melamine formaldehyde

Ureaformaldehyde


Polyester resin is a chemical hardener.

It will set at room temperature.

When set, the plastic is stiff, hard and brittle.

When working with it in large projects, it is advised to use gloves and a chemical respirator to protect yourself from the fumes.

Polyester resin can be reinforced with glass fibre.

Glass-reinforced polyester resin or glass-reinforced plastic (GRP) is used for making motor cycle fairings and boats.

Polyester resin


When plastic is used to make a large number of identical products, industrial processes are used. Specialized machines are used to mass produce products. Press play to see a video of the vacuum forming process.

Vacuum forming


What similarities and differences can you identify between the vacuum forming and injection moulding processes?

Injection moulding


What similarities and differences can you identify between the blow moulding and vacuum forming processes?

Blow moulding


What products can you think of that have been manufactured using a strip heater?

Line bending


What is the difference between male and female moulds?

Compression moulding


Can you think of any other products that are manufactured using extrusion?

Extrusion


Plastics have excellent surface qualities. As they are self-finishing, plastics require little or no surface finish. However, when designers want a specific colour or texture, spray paints can be used.

Use wet and dry paper (wet) to smooth the surface down and create a ‘key’ for the primer to grip to.Primer is used to create an undercoat to protect the plastic and provide a good surface finish for the top coat. The primer should be rubbed down using wet and dry paper between coats.Top coat is applied once the primer has completely hardened. There are different surface textures; gloss, matt and metallic being the most common. Top coat is applied in several layers to build up a thick, tough surface layer on the top of the primer.

Finishing techniques


Refrences- i)www.wikipedia.com ii)www.palsticsforengg.com iii)www.boardworks.com iv) www.prestwich.bury.sch.uk v) www.engr.sjsu.edu


Thank you

Documents

© Boardworks Ltd 2005 1 of 31 Project on thermoplastics and thermosetting plastics Submitted by- Shubham Saxena Sneha S