Lesson 7: Methods that meet today’s requirements – repair and overhaul using plastics

In this lesson, we will explore the use of plastics in repair and overhaul processes, including their applications, properties, and suitability.


  • Plastics have become indispensable in repair and overhaul activities due to advancements in the chemical industry.
  • They are utilized in various ways, such as coating, bonding, filling, sealing, and sheltering components.

Key Considerations

  • Before selecting plastics for repair, it’s crucial to assess their physical and mechanical properties.
  • Factors to evaluate include coefficient of thermal expansion, heat resistance, thermal conductivity, abrasion resistance, hardness, chemical behavior, and adhesion.

Properties of Plastics

  • Plastics exhibit unique properties:
    • Coefficient of thermal expansion much higher than metals, leading to residual internal stresses.
    • Heat resistance varies among plastics; some can withstand high temperatures while others decompose.
    • Low thermal conductivity compared to metals, which may result in local heating.
    • Favorable abrasion resistance, although embedded metal wear can affect mating steel components.

Types of Plastic and Their Applications

  • Poly-Vinyl Chloride
    • Used in films, sheets, pastes (adhesive, sealant), and low-stress parts.
  • Poly(tetra-fluoro) ethylene (Teflon)
    • Known for low friction, suitable for plain bearings.
    • Low compressive and tensile strength.
    • High heat resistance (used in pans) and good sealing performance.
    • Chemical resistant but challenging to bond.
  • Polypropylene
    • Features low density and moderate mechanical properties.
    • Offers good chemical resistance, suitable for pipe lining.
    • Weldable, deep-drawable, and used in various applications including vacuum forming.
  • Acrylic Resins
    • Available as instant, emulsion, and solvent adhesives.
  • Polyamides
    • Used for sintering and spraying coatings.
    • Ideal for bearings, gears, pulleys, and simple machine parts.
    • Exhibits good strength adhesive properties.
  • Polycarbonate
    • Translucent and crystalline thermoplastic with moderate chemical resistance.
    • Suited for gears, structural components, and electrical fittings.
    • Can be used to form adhesive coatings via flame spraying.


  • Plastics offer versatile solutions for repair and overhaul needs, with various types catering to specific requirements.
  • Understanding the properties and applications of different plastics is vital for effective maintenance and repair activities.
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