1. Thermosetting Plastics
Design and Manufacture

2. Thermosetting Plastics
These plastics are formed by chemical reactions which leave them in a relatively fixed state.
Thermosetting plastics are formed and ‘set’ in a single operation when a chemical reaction leaves them ‘fixed’ in the shape of the mould. They cannot be softened or reformed when reheated.
Although thermosets can withstand high temperatures, excess heat will simply cause the material to decompose.
An egg yolk is a good analogy for this. When a yolk is raw, it is in a soft liquid state. But if it is heated, it becomes hard and is no longer capable of becoming soft.
Thermosetting plastics are often used when a product needs resistance to extremes in temperature, electrical current, chemicals and wear.

3. Thermosetting Plastics

4. Thermosetting Plastics
Name
Properties and working characteristics
Uses
Glass reinforced plastics (GRP)
Strengthened by glass fibres, mats of glass fibre being sandwiched between layers of polyester plastics
Boat hulls, bodies and some structural components of high-performance cars and aircrafts
Carbon-fibre plastics (GFRP)
Strong, lightweight, higher strength to weight ratio, durable, very expensive
Modern bicycles, sailboats

5. Epoxy resin (ER) USES for bonding of other materials PROPERTIES
COMMON NAME: Araldite
Many adhesives (glues) are thermosetting plastics. A good example is ‘Araldite’ which is an epoxy resin that hardens when a second chemical is added (a catalyst). It will bond most materials including woods and metals as well as some plastics
USES
for bonding of other materials
PROPERTIES
Good electrical insulator
hard
brittle unless reinforced
resists chemicals well

6. Melamine formaldehyde (MF)
COMMON NAME: Formica or Melaware
Used in the production of plastic laminates because of its smooth surface and hygienic qualities.
PROPERTIES
waterproof
odourless
mark and scratch resistance
USES
worktops
buttons
electrical insulation

7. Urea formaldehyde COMMON NAME: Aerolyte or Cascamite
Used in homes as an adhesive resin in pressed wood products
PROPERTIES
good adhesive qualities
stiff, hard and brittle
good electrical insulator
USES
electrical fittings
paper and textile coating
wood adhesive

8. Polyester resin COMMON NAME: Orel or Beetle PROPERTIES
Stiff, hard and brittle
Resilient as laminated GRP
Formed without heat and pressure
USES
panels for car bodies and boat hulls
casting
embedding

9. GRP
One way on reinforcing plastic is to add fibred glass to it. This makes it much stronger and is generally referred to as G.R.P. (glass reinforced plastic).
GRP is used in car body repairs, sailing boats, corrugated sheet because of its lightness, toughness and resistance to water.