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.
- 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.
- 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.
- Used for sintering and spraying coatings.
- Ideal for bearings, gears, pulleys, and simple machine parts.
- Exhibits good strength adhesive properties.
- 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.