Engineering plastics, Mechanical Engineering

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Engineering Plastics

In this time this has become clear to know, the plastics are utilized as engineering materials for machine parts, casting and bodies and for structure mainly due to low density though their strength is much less than such of metal. In the electrical engineering field the plastics are utilized caused their excellent insulating properties, normally measured in forms of dielectric strength in V/m. Their low melting point is a weakness or negative advantage and in a lot of applications the maximum employ temperature is a yardstick also. The impact strength of plastics is other important characteristic and in applications, here vibration is likely to arise plastics of low impact strength are not favored. The capability of plastics to be made in thin walled bags so foamed structure, in various colours and to be recycled or thermoplastics are added advantages. Their non-degradability has undoubtedly that provide ascend to problems of last applications and disposal, at this time they can be discarded via users in public places is to discouraging. Table no.1 illustrates a few plastics, their applications and properties.

                                                                                                                       Table no.1

 Sl. No.

Plastic

Density

(g/cm3)

Tensile Strength (MPa)

Iozed Impact Strength (J/m)

Dielectric Strength (V/m)

Maximum Use Temperature (oC)

Applications

1

Polyethylene Low Density High Density

 

0.92-0.93

0.95-0.96

 

6.0-17

20-37

 

-

21-748

 

18912

-

 

82-100

80-120

Corrosion resistant, Containers, Tubing, Houseware and Electrical insulation, Packaging film.

2

Rigid Chlorinated

PVC

1.49-1.58

50-68

53-400

-

110

Chemically resistant, Building material, Auto upholstery, Shoes, Suitcases, Refrigerator gasket, Electrical wire insulation.

3

Polypropylene

0.90-0.91

33-38

21-117

25610

107-150

Bottles, Laboratory ware, Packaging, Fan shrouds, Heater ducts, Battery housing in automobiles.

4

Styrene Acrylonitrile (SAN)

1.08

70-83

21-27

69935

60-104

Instrument lens and dash board components in automobile, Medical syringes, Blood aspirators, Blender and mixer bowls.

5

ABS

1.05-1.07

40

320

15169

71-93

Pipe and fittings in drain waste and vent of buildings, Business machines, Computer housing, Electrical conduits.

6

Polymethyl Methacrylate (PMMA)

1.11-1.19

76

123

18715

54-110

Transparent like glass, Good weatherability, Glazing in aircrafts and boats, Skylight, Exterior lighting, Advertising signs, Auto tail light, Protective goggles.

7

Polytetrafluoro ethylene (PTFE, Teflon)

2.19

7.0-9.8

133-210

17730

288

High chemical resistance, Chemical piping, Pump parts, Electrical components, Cable insulation, Non-stick cooking utensile lining, Bearing seals, Bushings.

8

Phenolic (wood flour filled/glass filled/mica filled)

1.34-1.95

5-18

10.6-955

10,000-

15000

150-288

Connectors, Electrical switch gear, Telephone relays, Adhesive in

plywoods and binder of sand in foundary.

9

Polyster

(glass filled)

1.7-2.3

5-18

425-1150

1200-

1400

150-177

Good corrosion resistance, Pipes, Tanks, Ducts, Automobile body parts, Small boat hulls.

10

Melamine

1.5

5-13

10.6-26.5

6700-

1500

77-200

Knobs and handles, Moulded dinner wares, Binder in particle board, Boat hulls, Flooring.

11

Epoxy (without filler, glass/ mineral filled)

1.06-2.0

4-30

10.6-55

10700-

22000

120-260

Protective and decorative coating, Primer on automobile bodies, High voltage insulators in Switchgears


          Notice: Materials from Sl. No. 1 to 7 such are thermoplastics and Sl. No. 8 to 11 such are thermosetting plastics.Along with filler thermosetting plastics are used.


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