2. What is Plastics?
Derived from GREEK word “PLASTIKOS” = able to
be shaped or molded.
Any synthetic organic material that can be
molded under heat and pressure into a shape
that is retained after the heat and pressures are
removed is called plastic.
3. PLASTICS
Advantages
Durable
cheap
Corrosions resistance
Light weight
Reusable and recyclable
Good insulators
Resistant to chemicals and
water
Can be formed into
complex shapes
Disadvantages
Not friendly to the
environment
Can be a fire hazard
Brittle at low
temperature
Produce toxic fumes
when its burnt
Low heat resistance
Softer and less elastic
than metal
4. Thermoplastic
Can be softened and reshaped by heating again
and again
Many types – soften at different temperatures
They can be retransformed into thermoplastics by
reheating.
No chemical changes (curing) takes place during
the molding operations
5. -Will harden
when cooled,
but can be
reshaped
because it has
no link between
polymer chains
- Do not
chemically bond
with each other
when heated
7. Thermosetting plastic (thermoset)
It can be heated and set, once only
Cannot be re-softened
But once hardened they can not be transformed
back to thermosets by application of heat.
Used where an item needs to withstand heat
The thermosets are those that undergo a curing
process during heating and shaping, which causes
a permanent chemical change in their molecular
structure.
8. -If re-heated
they cannot
soften as
polymer chains
are interlink
-consist of
chain molecules
that chemically
bonded or
cross-linked
with each other
when heated
11. Plastic Forming Machine
It is the process of shaping plastic using a rigid frame
or mould.
It began somewhere between 1940 and 1950 in the
USA
By the late 1950s, when the rotational moulding
process was better understood, applications for other
industries were developed including road cones,
marine buoys, and car armrests. A process was
developed in Europe in the early 1960s that enabled
large hollow containers to be created in Low
Density Polyethylene(LDPE)
12. Working Mechanism
Forming the parison firstly, with compressed air (and
tensile rod) to the radial Inflation (axial stretch) type
blank, to make it close to (stretch) the blow molding
cavity, then the cavity shape and size are given to the
plastic products and make it cool.