Project 2 - High Tech - Matt Black

Material Research List

Plastic Processes

There are many processes used for moulding/forming plastic parts in everyday products.

Heat Forming


The simplest way to form plastic is to bend hot sheet material around a form to bend it into shape.


Injection Moulding

Injection moulding is one of the most common plastic forming processes, tiny plastic pellets are fed into a hopper which feeds a corkscrew. Whilst in transit, these pellets are melted by the heaters and are turned into a runny, liquid form suitable for injecting into the mould. This is injected at high pressure into the two part negative mould and briefly left to cool, the mould then splits and the product can be removed.

This moulding technique is very efficient as little operator input is required to operate the machine as it is mostly automated, no waste is produced as only the exact amount is injected into the mould and the process is very quick.

Compression Moulding

Compression moulding is another technique used as the machinery required is fairly cost effective. Again, the mould consists of a two-part negative mould where one part is attached to a hydraulic press and the other is a fixed, heated mould.

The operator has to measure out a precise amount of the required material and place it into the mould, the mould is then pressed together and the heated material changes shape to fill the mould cavity. From here, the product can be removed and cleaned up. This method is less efficient as an operator has to precisely measure out the material beforehand and then feed the material to the machine which is both time consuming and wasteful.


Rotational Moulding

Rotational moulding is used to form hollow objects such as ping-pong balls. Material is precisely measured and put into the mould cavity which is then sealed. The cavity is heated and spun in 2 axis; X and Y. This spinning motion used centripetal force to form a 'shell' with walls of consistent thickness. This can then be removed from the mould and cleaned up. The thickness of the walls is determined by the amount of material placed in the mould at the start, this is why precise measurements are critical.

This is one of the only one-step ways to form a hollow object. Whilst it is fairly time consuming to measure out the exact amount of material and fill the moulds, it is a very reliable moulding technique and as such, is widely used in industry.

Plastics Theory

General summary of Plastics

Good Electrical and Thermal insulators
Good Strength to Weight ratio
Generally good resistance to atmospheric and chemical erosion
Low Melting point (Cost effective moulding)
Lightweight
Wide range of colours available including transparent colours
Plastics are often referred to as Polymers (Many Part)

Thermo Plastics vs. Thermosetting Plastics

Thermo Plastics -

Made from polymer chains (See right)
Can be re-formed / recycled
Low forming temerature

Thermosetting Plastics-

Made from Polymer chains linked together (crosslink), (See right)
Can not be re-formed after initial setting.





Thermo Plastics (Thermo Polymers)


ABS - Acrylonitrile Butadiene Styrene : Hard wearing, Shatter resistant
CA - Cellulose Acetate : Heat resistant, Hard wearing
Nylon - Polyamide : Good wear resistance, Low friction
PMMA - PolyMethylMethAcrylate : Opaque, Cost effective
PP - PolyPropylene
HIPS - High Impact PolyStyrene : Impact Resistant
PS - PolyStyrene : Heat resistant, Lightweight, Cost effective
LDPE - Low Density PolyEthylene
uPVC - PolyVynil Chloride
PVC - (unplasticised, flexible) PolyVynil Chloride : Flexible, Hard wearing, Lightweight
PET - PolyEthylene Terephthalate : Malleable, Lightweight, Cost effective


Thermoset Plastics (Thermoset Polymers)


Epoxy Resins - Surface coatings, Encapsulation of electrical components, Adhesives
Melamine Formaldehyde - Tableware, Decorative laminates
Polyester Resins - Castings, Used in GRP (Glass Reinforced Castings)

I should never have Purchased...

About a year ago, I purchased a pair of shoes. These shoes cost quite a lot of money and by a lot of money, I mean £90. When you spend that much on a product, you expect the function to be of at least a satisfactory level. The shoes in question are a pair of 'Supra Skytop II's. These shoes definitely have the aesthetics, their white, black and red design definitely stands out and on top of that, they were very comfortable. They definitely looked like £90 worth of shoes. In terms of form, the design was outstanding.

After about 6 months of use, I noticed that the rubber had started to wear down at the sides and back of the sole, I take good care of them and I don't walk in a way that could cause excessive wear. Considering that these shoes are designed for skateboarding and other hard-wearing activity you'd expect these shoes to last a little longer than 6 months. The rubber sole should have been made of a tougher compound that can withstand day-to-day use and should have been made a fair bit thicker. The soles were only a few millimetres thick and had considerable damage to them. Again, you would not expect this from a pair of shoes designed for skateboarding and at £90 you would definately expect better build quality.

After owning these, I have to say that I'm quite disapointed. At first they seemed to have been a good purchase and I was very happy with the form but after 6 months, my views have changed conciderably. The function has not been fulfilled and now I'm left with a pair of sad looking shoes.