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SEMINAR ON
PLASTIC AND THEIR JOINING PROCESSES FOR DIFFERENT INDUSTRIAL USES
SUBMITTED BY :-PRAVEEN KUMARBRANCH : MEROLL NO. : 2004423
SUBMITTED TO :-MR. RANJEET SINGH
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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
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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.
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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
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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
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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
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Applications of Ultrasonic Welding
Computer and electrical industries
Aerospace and automotive industries
Medical industryPackaging industry
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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
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Applications of Friction Welding
domestic appliance industry
Automobile industry
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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
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Applications of Vibration Welding
Automobile industrydomestic appliance
industry
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