Materials - Plastics Flashcards
General Properties of Plastics
Plastics are:
generally less stiff than either
metal or timber
produced from crude oil,
coal and natural gas
available in a wide range of
colors and surface finishes
resistant to rotting and corrosion
generally stronger than timber
generally weaker than metals
often referred to as polymers
Thermoplastics
Thermoplastics:
soften when heated
Thermosetting Plastics
Thermosetting plastics:
do not soften when heated
can be shaped and molded
come as either sheets or as liquid
resins which can be made to set
Composites
Thermosetting resins can be
reinforced with fibers such as
glass or carbon to produce stiffer,
stronger materials.
Expanded Plastics
Solid plastics can be modified to
make foams.
Acrylic
- Polymethyl Methacrylate
- PMMA
- Softens 185-240 deg Fahrenheit
- Thermoplastic
- Used for signs or as a stand-in for glass
PVC
- Polyvinyl chloride
- PVC
- Softens between 160-175 deg Fahrenheit
- Thermoplastic
- Used for insulation tape, pipes
Nylon
- Polyamide
- PM
- Softens at 450 deg Fahrenheit
- Thermoplastic
- Used for bearings and super-light structures
Formica
- Melamine Formaldehyde
- MF
- Thermoset
- Work surfaces
Line Bending
Strip heaters are often used to
bend angles into acrylic.
They do this by heating a
localized area in the shape of
a small strip on the acrylic.
Care must be taken not to
over heat the acrylic or
bubbling may occur.
Once the acrylic has reached
softening temperature, it can be
bent to the required angle.
A jig is sometimes used to bend the
acrylic to a specific angle.
Vacuum Forming
Electrical elements heat the
plastic from above.
Air is removed by tiny holes in the
former, creating a vacuum.
Plastic expands onto the former.
Laminating
The idea of laminating is to
protect something with a hard
layer of plastic.
For example, instead of wooden
floor boards, less expensive
laminate flooring can be used.
A thin, resin-based pattern of
wood is protected beneath a
durable layer of clear plastic.
A thick layer of fiber board provides
support and strength for the plank.
Fiber board is made up of
wood dust, held together
with plastic resin.
Plastic Foams
inexpensive, light, soft, easy to
work by hand or machine
usually formed by hot wire cutting
Liquid Resins
expensive, strong, dense
used in conjunction with reinforcing
material for greater strength
can be cast or molded into shape
Formica
hard, dense and inflexible plastic
quite difficult to work by hand
or machine
usually laminated onto other
materials, for example, wood
