Upload
ira-jacobs
View
224
Download
0
Tags:
Embed Size (px)
Citation preview
UNIT-V MANUFACTURING OF PLASTICS
• In general many organic materials are used in
Engineering Industries.
• Organic material is matter (stuff) that has come from a
once-living organism(creature); is capable of decay.
How Organic Matter is created
• All living and growing matter on this planet contains organic
components. Different types of matter include humans,
animals, plants, and microorganisms. After the living matter
dies, it decomposes.
• Eg: (Compostable Material, Food Waste)
Organic materials are classified into two types:
• Natural organic materials
( Coal, wood, petroleum and natural rubber)
• Synthetic organic materials
(plastics, ceramics glass and synthetic rubber)
These are called polymers
(polymer is something made of many units. The
units or “monomers” are small molecules that
usually contain ten or less atoms in a row.)
POLYMERS
• Polymers are long chain molecules formed by
polymerization process.
– Linked polymers
– Branched polymers
– Cross-linked polymers
– Network polymers
• POLYMERIZATION PROCESS– The combination of many small molecules to form large
molecules.
It is achieved by
1.Addition polymerization
2. Condensation polymerization
An addition polymer is a polymer which is formed by an
addition reaction, where many monomers bond together via
rearrangement of bonds without the loss of any atom or
molecule.
Two or more unlike monomers are linked and there is a
repetitive releasing small molecules as by-products such as
water or methanol. This by - product formation is known as
condensation.
TYPES OF PLASTICS
• Thermoplastics and Thermosetting polymers.
• Thermoplastics are the plastics that do not undergo
chemical change in their composition when heated
and can be moulded again and again.
Examples are polyethylene, polypropylene,
polystyrene, polyvinyl chloride and
polytetrafluoroethylene (PTFE).
• Thermosets can melt and take shape once; after
they have solidified, they stay solid.
MOULDING OF THERMOPLASTICS
• Injection moulding
• Blow moulding
• Rotational moulding
• Film blowing
• Sheet forming process
PROCESSING OF THERMOSETS
• Compression moulding
• Transfer moulding
INJECTION MOULDING
Torpedo
Band Heaters
Shooting Pot
Nozzle
Hopper
Plunger
Screw meters plastic, plunger provides pressure
Band Heaters
Shooting Pot
Nozzle
Hopper
ReciprocatingScrew
TRANSFER MOULDING
Transfer Molding (Resin Transfer Molding) is a
process in which a pre-weighed amount of a
polymer is preheated in a separate chamber
(transfer pot) and then forced into a preheated
mold through a sprue, taking a shape of the mold
cavity and performing curing due to heat and
pressure applied to the material.
Typical parts: Electrical and electronic
components, rubber and silicone parts.
COMPRESSION MOLDING
• Compression Molding is a process in which a
molding polymer is squeezed into a preheated
mold taking a shape of the mold cavity and
performing curing due to heat and pressure
applied to the material.
• Examples: Dishes, Handles, Electrical
Components, Fittings and housings
BLOW MOLDING
• Blow Molding is a process in which a heated hollow
thermoplastic tube (parison) is inflated into a closed
mold conforming the shape of the mold cavity.
There are three principal techniques of Blow Molding,
differing in the method by which parisons are prepared:
• Extrusion Blow Molding
• Injection Blow Molding
• Stretch Blow Molding
ROTATIONAL MOLDING
TYPICAL PARTS: Tanks, trash cans, boat hulls, buckets, housings, toys, carrying cases, and footballs.
EXTRUSION• Extrusion process
• Most common manufacturing of plastic resin.• Combines pigments, additives and resin.• High heat, high pressure molten mixture.• Pushed through die.• Create warm plastic for possible further
“finishing” operation such as pelletizing, calendaring, or molding.
CALENDARING
THERMOFORMING