SUPER FUN PLASTICS

Aims

•To gain an understanding of how plastics are manufactured.

•To better understand the properties of common plastics and their uses

Print slides 2-3 double sided (1 for each team)

How was each product made?

Plastics forming processes or methods

Typical uses Used for thermoset, or thermoplastic

Description of process

Hand building processes

Boat building, custom car bodies, fair ground or amusement park rides. Used for one off, or batch production. Not suitable for high volume production. It is more efficient to injection mould a product if it is fairly complex and you want a large number of them.

Polyester resin, (a thermoset) and fibre glass, or carbon fibre are used to produce a composite . Produces strong, rigid, lightweight structures especially carbon fibre .

An interface of fibre glass or carbon fibre is soaked in polyester resin and pasted into a mould by hand. A catalyst is added to the resin to begin the process of turning from a gel to a solid. Needs a lot of skill to build the moulds in addition to ‘laying up’ the GRP.

Rotational casting This unique polymer moulding process affords moulders the ability to produce items ranging from small toy doll components to agricultural tanks that will hold up to 22,500 gallons (85,167 litres) of liquid. A variety of polymer materials can be used to provide specific characteristics to the products.

Thermoplastics, Polyethylene (HDPE, LPDE and LLPDE), PVC, Fluorocarbons, Polypropylene, Nylon and Polycarbonate

A heated hollow mould is filled with a charge or shot weight of material, it is then slowly rotated (usually around two perpendicular axes) causing the softened material to disperse and stick to the walls of the mould. In order to maintain even thickness throughout the part.

Plastics forming processes or methods

Typical uses Used for thermoset, or thermoplastic

Description of process

Vacuum forming Yoghurt pots, Chocolates and biscuit package trays. Shaped food containers and packages. School projects. Commonly used for high volume and one off, or batch production or mass production.

Thermoplastics (Polystyrene, acrylic, polycarbonate).

A heated thermoplastic sheet is pulled down onto a mould or former by a vacuum action.

Blow moulding Soft drinks containers, bottles, containers for detergent, washing up liquid bottles. High’ tooling’ costs makes blow moulding unsuitable for small scale production.

Thermoplastics such as HDPE or LDPE, or PET

begins as a blank cylinder which is heated inside a mould. Hot air is pumped into the blank. Or parison causing it to expand into the mould cavity. Generally used for mostly symmetrical, two part moulds.

Injection moulding Used for high volume production of complex plastic casings, containers and enclosures for electrical goods. Very expensive, initial ‘tooling’ costs. Unit costs greatly reduced because of high volume production.

Thermoplastics reduced to a liquid state. ABS, HDPE, LDPE, polypropylene, nylon.

A thermoplastic is heated and injected into a cavity where it takes on the form of the cavity in the mould. It cools and is finally ejected from the mould by ejector pins as the mould is opened. Injection moulding allows complex objects such as whole chairs to be moulded in one process.

Extrusion Plastic drain pipes, roof guttering, Window frame sections, plastic channelling. Anything that is a prism, or uniform in section.

Thermoplastics Thermoplastics are heated and plasticised so they can be squeezed through a die or mould.

calendering Plastic bags, plastic material for garments. Making flat sheets of thermoplastics to be sold to industry. Can also be used to press a pattern or surface detail into plastics

Thermoplastic Making different thicknesses of thermoplastics by heating and squeezing it through decreasing sized gaps between powerful rollers.

Compression moulding

Electrical fittings such as plugs and sockets. Cooking pot handles

Thermosets such as urea, phenol, or melamine formaldehyde

A powdered thermoset is heated and compressed into a mould at the same time. Once it is ‘baked’ it is removed.

Bottles and containers

Seed tray

Plastic seat for large scale production

Lightweight, see through roofing or

green house

Drill casing components for

high volume production

High volume, one piece,

moulded shoe

Loo seat and lid

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2

3

4

5

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8

ROUND 1

11

Prisms or uniform sections

Retail display stand

Flowerpots

Gear and pulley wheels

Plugs and electrical casings

Small volume production amusement park constructions

Kitchen work top coverings

Plastic films

Custom car bodiesPan handles

Moulded casings and luggage

Palm pilot or phone casing

Sunglasses

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ROUND 2

2

6

Prisms or uniform sections

Shoe sole

Toothbrush and bristles

Biro casingRaincoat and

garments

Disposable food trays

Wheelie bins

Motorcycle helmet

Pipes and guttering22

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29

ROUND 3

Plastics

What they is made fromPlastics are manufactured polymers made from crude oil. Plastic polymers occur in nature in things such as animal horn and shell.

StructureFYI - Mono means one and Poly means lots.

Plastics are made by joining together monomers (single plastic molecules) into Polymers (long chain molecules)

Plastics

# There are two categories of plastics Thermoplastics and Thermosetting plastics.

Thermoplastics – When heated, thermoplastics will deform and eventually melt.

Thermosets – When heated, thermosetting plastics do not melt, they eventually burn or degrade.

Advantages of plastics:• Very useful, versatile and available. Much quicker to use industrial plastic forming

processes than traditional crafting methods. Plastics are amazing for large quantity production.

• Plastics are ‘self finishing’. (The colour is built in to the plastic, through addition of coloured pigment at its raw state saving the need for painting, finishing etc.)

• Good resistance to atmospheric corrosion (air / water etc)

• Good electrical insulators (don’t conduct electricity)

• Some have excellent insulation against, or resistance to heat. (mainly thermosetting)

• Most can be recycled and use less energy in their production than glass and metals.

Disadvantages of plastics:

• Waste plastic does not break down or biodegrade. Lot of litter in the form of plastic bags etc. Waste plastic is a biological hazard.

• Oil and energy are wasted using unnecessary plastics for packaging etc.

• Plastic manufacturing methods are so successful and efficient that plastic has replaced every other method of making containers, packaging and utensils. Cost is minimised by making huge quantities rather than smaller, more responsible, sustainable quantities.

• Recycled plastics loose quality and are often referred to as “downycled”

Polymers

Acrylic

Acrylic is usually cast into sheets but is also available in rods and tubes. It is self—finishing, so it does not need to be painted. Acrylic has a wide range of uses within graphic products, from making models to shop signage.

When making a model, acrylic is a versatile sheet material as it can be easily cut and bent using a strip heater. Thinner sheets of acrylic can also be vacuum-formed just like polystyrene or PVC. Acrylic is available in a Wide range of colours, and has an excellent surface finish, which adds a quality feel to any model.

Polymers

Acrylic

In shop signage, a higher quality acrylic is used which must satisfy several high performance requirements. it has to be able to:

•Withstand extreme weather conditions, such as heat in the summer and cold in Winter.•Be chemical—resistant to pollution and detergents•Be durable by resisting long—term stresses, such as being. Outdoors for prolonged periods•Be easy to fabricate and to make relatively complicated shapes out of•Have excellent aesthetic properties, to attract a customer’s attention and give a high-quality look for the business.

Polymers

Styrofoam

”Styrofoam" is a polystyrene foam manufactured for the construction industry for insulating buildings. It also makes an excellent modelling material. The process of making the foam results in a material with uniformly small, closed cells, which gives it all of the properties that a modelling material should have.

Great for...•Modelling products in 3D•Developing designs•Testing & developing ergonomic features

Polymers

Styrofoam - Properties

• Great rigidity and high compressive strength so it cannot be bent out of shape easily

• Easy to cut and shape with a range of hand tools

• Sheets can be glued together using PVA to form larger blocks

• A smooth surface finish when sanded

• Can be painted to give a good quality finish if desired.

Polymers

Expanded polystyreneExpanded polystyrene is used in fast—food packaging because it is:

• hygienic — disposable cups and plates mean germs and bacteria are simply thrown away with the rubbish instead of multiplying in a chipped coffee mug, for instance.

• strong, yet lightweight- protects against moisture and keeps its strength. Containers and lids close tightly and prevent any leakage of the contents. it can be moulded into a variety of structural packages which complement its excellent cushioning properties in protecting the contents of the package.

• efficient- provides excellent insulation. Therefore, hot food can be kept warm for longer periods. It also means that the package does not become so hot that it cannot be held in the hand.

Polymers

Expanded polystyrene

• economical- products are generally cheaper to buy than disposable paper products and much cheaper than reusable service ware (e.g. china). This is because only about five per cent of the foam package is actually plastic — the rest is simply air

• convenient- with today’s busy lifestyles people want food to be available instantly, and polystyrene is an economical way of serving people with their fast food.

•Expanded polystyrene is also used in the protective packaging of many delicate products, such as electrical products. It fits snugly around products which are placed inside corrugated board boxes.