Polymers are created by the joining of monomers (polymerisation).
2 Types Thermosetting and thermoplastic
Thermosetting - are only molded once, non-recyclable and there are links between polymers to stop them moving its to complex.
Thermoplastics - can be reshaped if they are reheated many times and are more common.
General Properties of Polymers:
Good conductrors and insulators
Strong for the weight of the product
Good resistance to chemicals
Low melting point
Lightweight and durable
Ways of improving properties of polymers:
Fillers- are added to give it extra bulk and make it cheaper.
Flame Retardants - when the fire is present they slow down the spread of the fire
Anti-static agent - reduces static charge build up.
Stabalisers - reduces the effects of UV Light onto plastics
Thermo-Polymers:
ABS - Acrlonite butadine styreine
CA - Cellulose Acetate
Nylon - Polymide
PMMA - Acrylic
PP- Polypropellene
PS- Polystyrene
PE- Polyethelene
PVC- Polyvinalchloride
PET- Polyethelene Terepheluate
PC-Polycarbonate
Thermosetting Plastics:
Expoxy Resins- Adhesives.
Melamine Formaldehyde- Tables.
Polyester Resins- Castings used in GRP.
Urea Formaldehyde - Electrical Fittings and adhesives.
Homework:
Injection molding process:Plastic in the form of granules is melted until soft enough to be injected under enough pressure to fill a mould.
The result is that the shape is exactly copied. Once the plastic moulding has cooled enough to harden the mould opens releasing the part.
The main reasons for using a mould are:
Quicker
Safer
Faster
More Accurate
You can produce more efficiently
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