SEMINAR ON

PLASTIC AND THEIR JOINING PROCESSES FOR DIFFERENT INDUSTRIAL USES

SUBMITTED BY :-PRAVEEN KUMARBRANCH : MEROLL NO. : 2004423

SUBMITTED TO :-MR. RANJEET SINGH

Classification of polymers

Thermoplastics•Above the melting point, the secondary bonds weaken, making it easier to form the plastic into any desired shape•On cooling, it returns to its original strength and hardness•reversible process.

Thermosetting Plastics (thermosets)•Permanent shape•Cannot be re-melted •continued heating leads to degradation or decomposition•better mechanical, thermal and chemical properties•better electrical resistance and dimensional stability than do thermoplastics.

There are two major classifications of polymers

Uses of PlasticsThe modern car is made of many

different type of plastics, ranging from shock absorbing bumper bars to durable tyres and internal fittings.

Some plastics do not react with other substances and are chemically inert and non-toxic.

Many pipes are now made out of a plastic called polyvinyl chloride (PVC).

In kitchen a granite bench top is actually made of hard, durable plastic, while the tiles on the floor are made of vinyl plastic.

Some plastics (elastomers)are very flexible and resist melting,are used in making tyres.

Why Design with Plastics?Corrosion resistanceLow electrical and

thermal conductivity, insulator

Easily formed into complex shapes, can be formed, casted and joined.

Wide choice of appearance, colors and transparencies

Disadvantages of using PlasticsLow strengthLow useful temperature

range (up to 600 oF)Less dimensional

stability over period of time (creep effect)

Aging effect, hardens and become brittle over time

Sensitive to environment, moisture and chemicals

Poor machinability

Joining Methods of Plastics

Mechanical Fasteners

Adhesives

Welding Processes

• can join two components quickly

•do not provide leak• tight joint

• good properties and fully sound joints

• difficult to handle and slow to

• cure• to produce bonded

joints • confined to

thermoplastic polymers

Ultrasonic Welding Internal friction induced by ultrasonic

oscillation melts the boundary surfaces of the joining partners. Fusion of the parts is reached by applying a certain pressure

Advantages • Very short cycle times • Limited 3D contours – joints do not

have to be completely flat • Low maintenance costs

Disadvantages • Flash generated • limited to small components • Particulate development – dust-like

particles left behind that may cause part contamination

expensive

Applications of Ultrasonic Welding

Computer and electrical industries

Aerospace and automotive industries

Medical industryPackaging industry

Friction Welding Parts are rubbed together,

the friction created from this process generates heat at the contacting surfaces where the plastic becomes molten and weldable

Advantages • inexpensive process • Low maintenance • Low cycle times

Disadvantages • large flash generated • High mechanical load • Limited design freedom • Large weld line width

Applications of Friction Welding

domestic appliance industry

Automobile industry

Vibration Welding the vibrations applied

typically of 100 – 240 Hz, 1-5 mm amplitude

parts are rubbed together due to machine vibration

Advantages ability to weld a number of

components simultaneously

Ability to join large no. of pieces

Disadvantages For very small and light

parts

Applications of Vibration Welding

Automobile industrydomestic appliance

industry