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